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DOI: 10.1055/a-1878-8084
Construction of Quaternary Allylic Amino Acid Derivatives through Palladium-Catalyzed Allylic Alkylation Reaction of Azlactones with Vinyl Aziridine
We are grateful for the financial support from Youth Foundation of Henan Scientific Committee (No. 222300420249), Foundation of Henan Education Committee (No. 21A150039) and Doctoral Research Start-up Fund project of Nanyang Institute of Technology (No. NGBJ-2021-03).
Abstract
A highly efficient Pd-catalyzed allylic alkylation reaction of azlactones with vinyl aziridine has been achieved for the first time to access functionalized quaternary allylic amino acid derivatives (17 examples, up to 89% yield and 80% ee). Moreover, the broad scope and easy transformations of the products reinforce the value of this approach, which can enrich the chemistry of quaternary allylic amino acid derivatives.
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Key words
allylic alkylation - quaternary allylic amino acid derivatives - Pd-catalyzed - vinyl aziridine - azlactonesIn recent years, synthesis of functional quaternary amino acid derivatives has attracted considerable attention since they are key components in many active pharmaceutical ingredients.[1] [2] Among various strategies toward the construction of these useful compounds, azlactones have emerged as common starting materials because they contain numerous reaction sites.[3,4] As shown in Scheme 1a[4c] the C4-position of azlactones is nucleophilic, which can easily react with electrophiles[5] (Scheme [1a], eqn 1). Reports show that the azlactone ring can be opened by a nucleophilic attack at the C5-position forming various amino acid derivatives[6] (Scheme [1a], eqn 2). Azlactones can also participate in cyclization with dipoles utilizing its C4 and C5 reactivity[7] (Scheme [1a], eqn 3). Hence, we were curious about what happens to the azlactones when the allylic synthons were used as the reaction partners, which contain both nucleophilic (Nu–) and electrophilic (E+) sites. Recently, Zhao’s group developed a formal [5+2] cycloaddition of azlactones with 2-phenyl-2-vinyloxiranes, furnishing the desired seven-membered lactones derivatives[8a] (Scheme [1b]). Cai demonstrated the feasibility of allylic alkylation reaction of azlactones with vinylcyclopropane, which provided concise access to quaternary allylic amino acid derivatives.[8b] However, other allylic synthons, such as vinyl aziridine, still remain unexplored.
According to studies, vinyl aziridine, in the presence of palladium(0) species, mainly undergoes formal [3+2] cycloaddition[9] rather than allylic allylation reaction.[10] Although several elegant examples of the allylic allylation reaction using vinyl aziridine as electrophile have been reported, these reactions are usually limited to stable carbon nucleophiles.[10] At present, azlactones, possessing numerous reaction sites, have not yet been employed as the carbon nucleophile to react with vinyl aziridine. Given the reaction’s interest, we envisioned that the allylic alkylation reaction of azlactones with vinyl aziridine could provide a new synthetic route to quaternary amino acid derivatives. It should be noted that the reaction is still full of challenges because the reactivity of vinyl aziridine is lower than that of vinyl cyclopropane[9f] (Scheme [1c]).
a Reaction conditions: [M] (10 mol%), L (10 mol%), additive (1.0 equiv), 1a (0.1 mmol), 2 (0.12 mmol), solvent (1.0 mL) at rt for 24 h.
b Isolated yield.
We started our investigation by employing 4-benzyl-2-(4-methoxyphenyl)oxazol-5(4H)-one (1a) with 1-tosyl-2-vinylaziridine (2) as model reaction (Table [1]). The reaction was carried out in dichloromethane in the presence of 5 mol% of Pd2(dba)3 at room temperature for 24 hours. The linear product[11] 3a was obtained in moderate yield (53%) (Table [1], entry 1). Other palladium source, such as Pd(PPh3)4, show poor catalytic effects (entry 2). After screening different metal precursors, the reaction did not show significant improvements (entries 3, 4). Then, a series of achiral diphosphine ligands L1–L4 were examined (entries 5–8). To our delight, utilization of rac-BINAP (L4) showed significant improvements, producing an 80% yield of 3a (entry 8). Meanwhile, it was found that the addition of a base also played a vital role in the reaction outcome. However, a strong base, such as Cs2CO3, had a detrimental effect on the yield, whereas Na2CO3 was demonstrated to be the best additive (entries 9–12). Further examination of solvents such as diethyl ether, chloroform, toluene, chlorobenzene, dimethylformamide, or acetonitrile showed that CH2Cl2 is the optimum solvent (entries 13–18). Based on the series of experiments, the optimal conditions were determined as follows: When 1a (0.1 mmol) and 2 (0.12 mmol) were treated with Na2CO3 (1 equiv) in the presence of Pd2(dba)3 (5 mol%) and rac-BINAP (L4; 10 mol%) in dichloromethane at room temperature for 24 hours, the desired product 3a was isolated in 87% yield (entry 11).
a Unless otherwise noted, the reaction conditions were as follows: Pd2(dba)3 (5 mol%), L4 (10 mol%), 1 (0.1 mmol), 2 (0.12 mmol), Na2CO3 (1.0 equiv), CH2Cl2 (1.0 mL) at rt for 24 h.
b Isolated yield.
c Reaction time: 48 h.
Under the optimized reaction conditions, the scope with respect to the azlactones was evaluated and summarized in Table [2]. In most cases, the reactions proceeded well and were completed within 24 hours. Substrates with different alkyl substituents (methyl, ethyl, propyl, and butyl) at the C4 position of 1,3-oxazol-5(4H)-one skeleton worked well in this allylic alkylation reaction to deliver 3b–h in similar yields. It seems that steric hindrance has little effect on the yields (Table [2], entries 2–8). Functional groups such as a substituted benzyl group, an aryl group, or a sulfide were also well tolerated, furnishing the desired products 3i–k in good yields (entries 9–11). Notably, substrates bearing an unprotected indole group underwent allylic alkylation reaction for 48 hours with a slight decrease in yield (52% yield, entry 12). Other substrates bearing hydrogen, chloro, or methyl substituents on the phenyl skeleton also showed good reaction efficiency, delivering the desired products 3m–o in yields of 83–89% (entries 13–15). Introducing a tert-butyl group at the C2-position of azlactone appeared to have little effect on the reaction outcomes (79% yield, entry 16).
With the useful allylic alkylation protocol in hand, we were curious whether the catalytic system could be extended to the reaction of 2-vinyloxirane (Scheme [2]). When employing 4-benzyl-2-(4-methoxyphenyl)oxazol-5(4H)-one (1a) with 2-vinyloxirane (4), the desired product 5a was obtained in 81% yield under the now standard reaction conditions. Note that the current catalytic systems could not tolerate 2-(prop-1-en-2-yl)-1-tosylaziridine.
In line with the application of this method, a scale up synthesis and further transformations were conducted (Scheme [3]). In the presence of 5 mol% Pd2(dba)3 and 10 mol% L4, 5 mmol of azlactone substrate 1a reacted smoothly with 1-tosyl-2-vinylaziridine (2), affording 1.90 g (76% yield) of the desired allylic alkylation product 3a (Scheme [3a]). Treatment of 3a with K2CO3/MeOH resulted in protected quaternary allylic amino acid 6a in excellent yield. Meanwhile, product 3a was easily converted to compound 7a through hydrolysis reaction (Scheme [3b]).
Meanwhile, the enantioselective variant of this allylic alkylation reaction was also tried (Table [3]). In initial experiments, azlactone 1a and 1-tosyl-2-vinylaziridine (2) were used as model substrates, with Pd2(dba)3/L as the catalyst and CH2Cl2 as solvent. The C2-symmetric diphosphine ligand L5 gave the desired product 3a in high yield with low ee-value (Table [3], entry 1). Then, various chiral phosphine ligands L6–L17 were evaluated using similar conditions in an attempt to improve the yield and ee of 3a. However, these efforts were unsuccessful (entries 2–13). Further screening the ligands showed that (S)-3,5-tBu-4-MeO-MeOBIPHEP (L18) gave 3a in 66% yield and 69% ee (entry 14).
a Unless otherwise noted, the reaction conditions were as follows: [Pd] (10 mol%), L (10 mol%), 1a (0.1 mmol), 2 (0.12 mmol), additive (1.0 equiv), solvent (1.0 mL) at rt for 24 h.
b Isolated yield.
c Determined by HPLC analysis.
Furthermore, evaluation of different solvents showed that CHCl3 can increase the ee-value but decrease the yield, affording product 3a in 59% yield and 80% ee (Table [3], entries 15–20). Other Pd sources coordinated with ligand L18 had a detrimental influence on the reaction (entries 21–24). Meanwhile, a slight enhancement of the yield was achieved when the additive Na2CO3 was introduced into the reaction (entries 25–27). Although a series of chiral phosphine ligands were systematically investigated, the chiral product 3a was only obtained in 65% yield and 80% ee with Pd2(dba)3/L-18 as the catalyst, Na2CO3 as the additive, and CHCl3 as the solvent (entry 27).
In conclusion, we have successfully developed a Pd-catalyzed allylic alkylation reaction, which provides a convenient and efficient strategy to construct quaternary allylic amino acid derivatives containing trans-form double bond and another amino/hydroxyl group in high yields. Meanwhile, the broad scope and easy transformations of the products reinforce the value of this approach, which can enrich the chemistry of quaternary allylic amino acids derivatives. Although further improvement of the enantioselectivity of this allylic alkylation reaction is still needed, the results are expected to provide opportunities for developing new methods in asymmetric synthesis quaternary allylic amino acids derivatives.
All reagents were reagent grade quality and purchased from commercial sources, unless otherwise indicated. NMR spectra were recorded with a 600 MHz or 400 MHz spectrometer for 1H NMR, 150 MHz, or 100 MHz for 13C NMR. Data were reported as follows: chemical shift, multiplicity (s = singlet, d = doublet; t = triplet; q = quartet; m = multiplet; br = broad, etc.), coupling constants (Hz), integration. Enantiomer excesses were determined by chiral HPLC analysis on Chiralcel ID in comparison with the authentic racemates. High-resolution mass spectra [HRMS (ESI)] were obtained via ESI mode by using a MicrOTOF mass spectrometer. Optical rotations were reported as follows: [α]D T (c: g/100 mL, in solvent). The chiral ligands L1–L18 were purchased from commercial suppliers and used without further purification. All the azlactones are known compounds and synthesis according to the literature.[5e] [h] [6i]
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Functionalized Quaternary Allylic Amino Acid Derivatives 3; General Procedure
In a test tube, azlactone 1 (0.1 mmol), Pd2(dba)3 (4.5 mg, 5 mol%), rac-BINAP (6.3 mg, 10 mol%), and Na2CO3 (10.6 mg, 1.0 equiv) were added. The tube was filled with N2 gas. Subsequently, CH2Cl2 (1.0 mL) was added, and the mixture was stirred at rt for 0.5 h. Then, the vinyl aziridine 2 (26.7 mg, 0.12 mmol) was added and the mixture was stirred at rt for 24 h. After completion of the reaction, which was determined by TLC, the mixture was directly purified by flash chromatography on silica gel (PE/EtOAc 2:1) to afford the desired product 3.
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Catalytic Asymmetric Allylic Alkylation Reaction; Typical Procedure
In a test tube, 4-benzyl-2-(4-methoxyphenyl)oxazol-5(4H)-one (1a; 28.1 mg, 0.1 mmol), Pd2(dba)3 (4.5 mg, 5 mol%), L18 (11.5 mg, 10 mol%), and Na2CO3 (10.6 mg, 1.0 equiv) were added. The tube was filled with N2 gas. Subsequently, CHCl3 (1.0 mL) was added and the mixture was stirred at rt for 0.5 h. Then, the vinyl aziridine 2 (26.7 mg, 0.12 mmol) was added and the mixture was stirred at rt for 24 h. After completion of the reaction, which was determined by TLC, the mixture was directly purified by flash chromatography on silica gel (PE/EtOAc 2:1) to afford the product Cat-3a (65%, 32.7 mg, 80% ee).
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(E)-N-(4-(4-Benzyl-2-(4-methoxyphenyl)-5-oxo-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3a)
rac-3a: colorless oil; 87% yield, 43.8 mg; Rf = 0.27 (PE/EtOAc 2:1) [UV].
Cat-3a: colorless oil; 65% yield, 32.7 mg, 80% ee; [α]D 26 62.1 (c 0.7, CH2Cl2).
HPLC: Chiralcel ID, n-hexane/i-PrOH (50:50), flow rate = 1.0 mL/min, column temperature = 25 °C, λ = 250 nm, t R = 12.770 min (minor), 16.670 min (major).
1H NMR (400 MHz, CDCl3): δ = 7.76 (d, J = 8.8 Hz, 2 H), 7.67 (d, J = 8.2 Hz, 2 H), 7.29–7.23 (m, 2 H), 7.16–7.12 (m, 5 H), 6.91 (d, J = 8.8 Hz, 2 H), 5.57–5.41 (m, 2 H), 4.37 (t, J = 6.0 Hz, 1 H), 3.85 (s, 3 H), 3.46 (t, J = 6.0 Hz, 2 H), 3.10 (q, J = 13.4 Hz, 2 H), 2.65–2.56 (m, 2 H), 2.40 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 179.2, 163.3, 159.7, 143.6, 136.8, 134.3, 130.7, 130.2, 129.8, 129.8, 128.3, 127.3, 127.2, 126.8, 117.8, 114.3, 74.4, 55.6, 45.1, 43.2, 39.9, 21.7.
HRMS (ESI): m/z [M + Na]+ calcd for C28H28N2O5SNa: 527.1611; found: 527.1619.
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(E)-N-(4-(2-(4-Methoxyphenyl)-4-methyl-5-oxo-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3b)
Colorless oil; 79% yield, 33.8 mg; Rf = 0.23 (PE/EtOAc 2:1).
1H NMR (400 MHz, CDCl3): δ = 7.90 (d, J = 8.8 Hz, 2 H), 7.67 (d, J = 8.2 Hz, 2 H), 7.27 (d, J = 7.5 Hz, 2 H), 6.98 (d, J = 8.8 Hz, 2 H), 5.55–5.39 (m, 2 H), 4.38 (t, J = 6.0 Hz, 1 H), 3.88 (s, 3 H), 3.46 (t, J = 5.4 Hz, 2 H), 2.52–2.44 (m, 2 H), 2.41 (s, 3 H), 1.46 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 180.3, 163.4, 159.8, 143.6, 136.9, 130.6, 129.9, 129.8, 127.2, 126.9, 117.9, 114.4, 69.3, 55.7, 45.1, 40.9, 23.3, 21.7.
HRMS (ESI): m/z [M + Na]+ calcd for C22H24N2O5SNa: 451.1298; found: 451.1292.
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(E)-N-(4-(4-Ethyl-2-(4-methoxyphenyl)-5-oxo-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3c)
Colorless oil; 85% yield, 37.5 mg; Rf = 0.21 (PE/EtOAc 2:1) [UV].
1H NMR (400 MHz, CDCl3): δ = 7.95–7.89 (m, 2 H), 7.67 (d, J = 8.0 Hz, 2 H), 7.27 (d, J =8.0 Hz, 2 H), 7.01–6.96 (m, 2 H), 5.54–5.39 (m, 2 H), 4.31 (t, J = 6.0 Hz, 1 H), 3.89 (s, 3 H), 3.47–3.44 (m, 2 H), 2.56–2.43 (m, 2 H), 2.41 (s, 3 H), 1.87 (q, J = 7.6 Hz, 2 H), 0.82 (t, J = 7.2 Hz, 3 H).
13C NMR (150 MHz, CDCl3): δ = 179.9, 163.4, 160.0, 143.6, 136.9, 130.4, 129.9, 129.8, 127.2, 127.0, 118.0, 114.4, 73.9, 55.7, 45.1, 39.9, 30.2, 21.7, 8.3.
HRMS (ESI): m/z [M + Na]+ calcd for C23H26N2O5SNa: 465.1455; found: 465.1457.
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(E)-N-(4-(2-(4-Methoxyphenyl)-5-oxo-4-propyl-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3d)
Colorless oil; 83% yield, 37.8 mg; Rf = 0.25 (PE/EtOAc 2:1) [UV].
1H NMR (400 MHz, CDCl3): δ = 7.94–7.87 (m, 2 H), 7.71–7.63 (m, 2 H), 7.30–7.23 (m, 2 H), 7.01–6.95 (m, 2 H), 5.53–5.37 (m, 2 H), 4.31 (t, J = 6.2 Hz, 1 H), 3.88 (s, 3 H), 3.49–3.42 (m, 2 H), 2.56–2.43 (m, 2 H), 2.41 (s, 3 H), 1.83–1.77 (m, 2 H), 1.33–1.08 (m, 2 H), 0.87 (t, J = 7.2 Hz, 3 H).
13C NMR (150 MHz, CDCl3): δ = 180.0, 163.4, 159.9, 143.6, 136.9, 130.5, 129.9, 129.8, 127.2, 126.9, 118.0, 114.4, 73.4, 55.7, 45.1, 40.2, 39.1, 21.6, 17.4, 14.0.
HRMS (ESI): m/z [M + Na]+ calcd for C24H28N2O5SNa: 479.1611; found: 479.1617.
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(E)-N-(4-(4-Isopropyl-2-(4-methoxyphenyl)-5-oxo-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3e)
Colorless oil; 85% yield, 38.7 mg; Rf = 0.27 (PE/EtOAc 2:1) [UV].
1H NMR (400 MHz, CDCl3): δ = 7.96–7.88 (m, 2 H), 7.68–7.64 (m, 2 H), 7.27–7.25 (m, 2 H), 6.99–6.96 (m, 2 H), 5.51–5.45 (m, 1 H), 5.42–5.37 (m, 1 H), 4.30 (t, J = 6.0 Hz, 1 H), 3.88 (s, 3 H), 3.48–3.37 (m, 2 H), 2.58 (dd, J = 14.0, 6.6 Hz, 1 H), 2.46 (dd, J = 13.8, 7.6 Hz, 1 H), 2.41 (s, 3 H), 2.13–2.04 (m, 1 H), 1.01 (d, J = 6.8 Hz, 3 H), 0.91 (d, J = 6.8 Hz, 3 H).
13C NMR (150 MHz, CDCl3): δ = 179.8, 163.3, 159.8, 143.6, 136.9, 130.4, 129.9, 129.8, 127.2, 127.2, 118.0, 114.4, 76.5, 55.7, 45.1, 37.7, 34.5, 21.6, 17.1, 16.8.
HRMS (ESI): m/z [M + Na]+ calcd for C24H28N2O5SNa: 479.1611; found: 479.1615.
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(E)-N-(4-(4-Butyl-2-(4-methoxyphenyl)-5-oxo-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3f)
Colorless oil; 89% yield, 41.8 mg; Rf = 0.23 (PE/EtOAc 2:1) [UV].
1H NMR (400 MHz, CDCl3): δ = 7.84 (d, J = 8.8 Hz, 2 H), 7.60 (d, J = 8.2 Hz, 2 H), 7.20 (d, J = 6.4 Hz, 2 H), 6.92 (d, J = 8.8 Hz, 2 H), 5.49–5.29 (m, 2 H), 4.25 (t, J = 6.0 Hz, 1 H), 3.81 (s, 3 H), 3.38 (t, J = 5.2 Hz, 2 H), 2.48–2.37 (m, 2 H), 2.34 (s, 3 H), 1.81–1.71 (m, 2 H), 1.23–1.12 (m, 3 H), 1.06–0.95 (m, 1 H), 0.77 (t, J = 7.2 Hz, 3 H).
13C NMR (100 MHz, CDCl3): δ = 180.0, 163.4, 159.8, 143.6, 136.9, 130.5, 129.9, 129.8, 127.2, 126.9, 117.9, 114.4, 73.4, 55.7, 45.1, 40.2, 36.8, 26.0, 22.6, 21.7, 13.9.
HRMS (ESI): m/z [M + Na]+ calcd for C25H30N2O5SNa: 493.1768; found: 493.1772.
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(E)-N-(4-(4-Isobutyl-2-(4-methoxyphenyl)-5-oxo-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3g)
Colorless oil; 85% yield, 39.9 mg; Rf = 0.23 (PE/EtOAc 2:1) [UV].
1H NMR (400 MHz, CDCl3): δ = 7.92 (d, J = 8.8 Hz, 2 H), 7.67 (d, J = 8.2 Hz, 2 H), 7.27 (d, J = 8.0 Hz, 2 H), 6.99 (d, J = 8.8 Hz, 2 H), 5.51–5.44 (m, 1 H), 5.44–5.35 (m, 1 H), 4.28 (t, J = 6.0 Hz, 1 H), 3.89 (s, 3 H), 3.46–3.40 (m, 2 H), 2.53–2.43 (m, 2 H), 2.42 (s, 3 H), 1.88 (dd, J = 14.0, 5.4 Hz, 1 H), 1.75 (dd, J = 14.0, 7.4 Hz, 1 H), 1.59 (dt, J = 13.0, 6.6 Hz, 1 H), 0.87 (d, J = 6.6 Hz, 3 H), 0.82 (d, J = 6.6 Hz, 3 H).
13C NMR (100 MHz, CDCl3): δ = 180.5, 163.4, 159.6, 143.6, 136.9, 130.7, 129.9, 127.2, 126.6, 118.0, 114.5, 72.8, 55.7, 45.7, 45.1, 41.5, 25.1, 24.1, 23.1, 21.7.
HRMS (ESI): m/z [M + Na]+ calcd for C25H30N2O5SNa: 493.1768; found: 493.1764.
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(E)-N-(4-(4-(tert-Butyl)-2-(4-methoxyphenyl)-5-oxo-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3h)
Colorless oil; 86% yield, 40.4 mg; Rf = 0.25 (PE/EtOAc 2:1) [UV].
1H NMR (400 MHz, CDCl3): δ = 7.91 (d, J = 8.8 Hz, 2 H), 7.62 (d, J = 8.2 Hz, 2 H), 7.25 (d, J = 8.2 Hz, 2 H), 6.98 (d, J = 8.8 Hz, 2 H), 5.51–5.39 (m, 1 H), 5.32–5.21 (m, 1 H), 4.11 (t, J = 6.0 Hz, 1 H), 3.88 (s, 3 H), 3.39–3.35 (m, 2 H), 2.65–2.53 (m, 2 H), 2.40 (s, 3 H), 1.05 (s, 9 H).
13C NMR (150 MHz, CDCl3): δ = 179.4, 163.3, 159.3, 143.6, 136.9, 130.5, 129.9, 129.8, 127.8, 127.2, 118.1, 114.4, 78.9, 55.7, 45.1, 37.5, 34.6, 25.1, 21.6.
HRMS (ESI): m/z [M + Na]+ calcd for C25H30N2O5SNa: 493.1768; found: 493.1765.
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(E)-N-(4-(2-(4-Methoxyphenyl)-4-(2-(methylthio)ethyl)-5-oxo-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3i)
Colorless oil; 86% yield, 41.9 mg; Rf = 0.25 (PE/EtOAc 2:1) [UV].
1H NMR (400 MHz, CDCl3): δ = 7.91 (d, J = 8.8 Hz, 2 H), 7.67 (d, J = 8.0 Hz, 2 H), 7.27 (d, J = 8.5 Hz, 2 H), 6.98 (d, J = 8.8 Hz, 2 H), 5.55–5.38 (m, 2 H), 4.31 (t, J = 6.0 Hz, 1 H), 3.88 (s, 3 H), 3.45 (t, J = 5.0 Hz, 2 H), 2.57–2.43 (m, 3 H), 2.41 (s, 3 H), 2.37–2.28 (m, 1 H), 2.17–2.13 (m, 2 H), 2.04 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 179.8, 163.5, 160.5, 143.7, 136.8, 131.0, 130.0, 129.9, 127.2, 126.3, 117.8, 114.5, 72.3, 55.7, 45.1, 40.5, 35.8, 28.8, 21.7, 15.3.
HRMS (ESI): m/z [M + Na]+ calcd for C24H28N2O5S2Na: 511.1332; found: 511.1327.
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(E)-N-(4-(2-(4-Methoxyphenyl)-5-oxo-4-phenyl-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3j)
Colorless oil; 82% yield, 40.1 mg; Rf = 0.27 (PE/EtOAc 2:1) [UV].
1H NMR (400 MHz, CDCl3): δ = 8.01–7.98 (m, 2 H), 7.69–7.60 (m, 4 H), 7.40–7.27 (m, 5 H), 7.01–6.99 (m, 2 H), 5.51–5.40 (m, 2 H), 4.12 (t, J = 6.4 Hz, 1 H), 3.90 (s, 3 H), 3.45–3.41 (m, 2 H), 2.87–2.77 (m, 2 H), 2.42 (s, 3 H).
13C NMR (150 MHz, CDCl3): δ = 178.3, 163.6, 160.1, 143.6, 137.8, 136.9, 131.0, 130.1, 129.8, 128.8, 128.5, 127.3, 126.9, 125.8, 118.0, 114.5, 74.2, 55.7, 45.1, 43.5, 21.7.
HRMS (ESI): m/z [M + Na]+ calcd for C27H26N2O5SNa: 513.1455; found: 513.1465.
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(E)-N-(4-(4-(4-Chlorobenzyl)-2-(4-methoxyphenyl)-5-oxo-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3k)
Colorless oil; 87% yield, 46.8 mg; Rf = 0.25 (PE/EtOAc 2:1) [UV].
1H NMR (400 MHz, CDCl3): δ = 7.77 (d, J = 8.8 Hz, 2 H), 7.67 (d, J = 8.2 Hz, 2 H), 7.26 (d, J = 8.0 Hz, 2 H), 7.13 (d, J = 8.4 Hz, 2 H), 7.06 (d, J = 8.4 Hz, 2 H), 6.93 (d, J = 8.8 Hz, 2 H), 5.58–5.48 (m, 1 H), 5.48–5.40 (m, 1 H), 4.43 (t, J = 6.0 Hz, 1 H), 3.86 (s, 3 H), 3.46 (t, J = 5.6 Hz, 2 H), 3.14–2.96 (m, 2 H), 2.63–2.53 (m, 2 H), 2.40 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 179.0, 163.4, 159.9, 143.6, 136.9, 133.3, 132.9, 131.6, 130.9, 129.8, 128.4, 127.2, 126.5, 117.6, 114.4, 74.2, 55.6, 45.0, 42.3, 40.0, 21.6.
HRMS (ESI): m/z [M + Na]+ calcd for C28H27ClN2O5SNa: 561.1221; found: 561.1220.
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(E)-N-(4-(4-((1H-Indol-3-yl)methyl)-2-(4-methoxyphenyl)-5-oxo-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3l)
Colorless oil; 52% yield, 28.2 mg; Rf = 0.23 (PE/EtOAc 1:1) [UV].
1H NMR (400 MHz, CDCl3): δ = 8.04 (s, 1 H), 7.71–7.65 (m, 5 H), 7.24–7.21 (m, 2 H), 7.10–7.04 (m, 2 H), 6.99 (d, J = 2.2 Hz, 1 H), 6.88–6.85 (m, 2 H), 5.57–5.41 (m, 2 H), 4.31 (t, J = 6.0 Hz, 1 H), 3.82 (s, 3H ), 3.52–3.40 (m, 3 H), 3.27 (s, 2 H), 2.75–2.56 (m, 2 H), 2.39 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 179.8, 163.2, 159.9, 143.6, 136.9, 135.8, 130.4, 129.8, 127.7, 127.2, 127.1, 123.9, 122.0, 119.6, 117.9, 114.2, 111.0, 108.9, 74.9, 55.6, 45.1, 39.7, 33.1, 21.6.
HRMS (ESI): m/z [M + Na]+ calcd for C30H29N3O5SNa: 566.1720; found: 566.1723.
#
(E)-N-(4-(4-Benzyl-5-oxo-2-phenyl-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3m)
Colorless oil; 89% yield, 42.1 mg; Rf = 0.29 (PE/EtOAc 2:1) [UV].
1H NMR (600 MHz, CDCl3): δ = 7.73 (d, J = 7.4 Hz, 2 H), 7.59 (d, J = 8.2 Hz, 2 H), 7.45 (t, J = 7.4 Hz, 1 H), 7.34 (t, J = 7.8 Hz, 2 H), 7.17 (d, J = 8.2 Hz, 2 H), 7.10–7.04 (m, 5 H), 5.50–5.44 (m, 1 H), 5.44–5.35 (m, 1 H), 4.44 (t, J = 6.0 Hz, 1 H), 3.39–3.75 (m, 2 H), 3.11–2.97 (m, 2 H), 2.55 (qd, J = 14.0, 7.0 Hz, 2 H), 2.32 (s, 3 H).
13C NMR (150 MHz, CDCl3): δ = 178.9, 160.1, 143.6, 136.9, 134.2, 132.8, 130.9, 130.2, 129.8, 128.8, 128.3, 127.9, 127.4, 127.2, 125.5, 74.5, 45.0, 43.1, 39.8, 21.6.
HRMS (ESI): m/z [M + Na]+ calcd for C27H26N2O4SNa: 497.1505; found: 497.1513.
#
(E)-N-(4-(4-Benzyl-5-oxo-2-(p-tolyl)-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3n)
Colorless oil; 86% yield, 41.9 mg; Rf = 0.27 (PE/EtOAc 2:1) [UV].
1H NMR (600 MHz, CDCl3): δ = 7.60 (dd, J = 13.8, 8.2 Hz, 4 H), 7.15 (dd, J = 18.8, 8.0 Hz, 4 H), 7.10–7.00 (m, 5 H), 5.52–5.42 (m, 1 H), 5.42–5.33 (m, 1 H), 4.52 (t, J = 6.0 Hz, 1 H), 3.41–3.33 (m, 2 H), 3.11–2.95 (m, 2 H), 2.52 (qd, J = 14.0, 7.0 Hz, 2 H), 2.31 (s, 6 H).
13C NMR (150 MHz, CDCl3): δ = 179.1, 160.1, 143.5, 136.9, 134.2, 130.7, 130.2, 129.8, 129.5, 128.2, 127.9, 127.3, 127.2, 126.6, 122.7, 74.4, 45.0, 43.1, 39.9, 21.8, 21.6.
HRMS (ESI): m/z [M + Na]+ calcd for C28H28N2O4SNa: 511.1662; found: 511.1667.
#
(E)-N-(4-(4-Benzyl-2-(4-chlorophenyl)-5-oxo-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3o)
Colorless oil; 83% yield, 42.1 mg; Rf = 0.25 (PE/EtOAc 2:1) [UV].
1H NMR (400 MHz, CDCl3): δ = 7.75 (d, J = 8.4 Hz, 2 H), 7.68 (d, J = 8.4 Hz, 2 H), 7.40 (d, J = 8.4 Hz, 2 H), 7.27 (d, J = 8.0 Hz, 2 H), 7.17–7.09 (m, 5 H), 5.59–5.51 (m, 1 H), 5.51–5.43 (m, 1 H), 4.29 (s, 1 H), 3.50–3.44 (m, 2 H), 3.16–3.07 (m, 2 H), 2.68–2.58 (m, 2 H), 2.41 (s, 3 H).
13C NMR (150 MHz, CDCl3): δ = 178.7, 159.3, 143.7, 139.3, 136.9, 134.1, 131.0, 130.2, 129.9, 129.3, 129.2, 128.3, 127.5, 127.2, 126.4, 124.0, 74.7, 45.0, 43.2, 39.8, 21.7.
HRMS (ESI): m/z [M + Na]+ calcd for C27H25ClN2O4SNa: 531.1116; found: 531.1117.
#
(E)-N-(4-(4-Benzyl-2-(tert-butyl)-5-oxo-4,5-dihydrooxazol-4-yl)but-2-en-1-yl)-4-methylbenzenesulfonamide (3p)
Colorless oil; 79% yield, 35.8 mg; Rf = 0.22 (PE/EtOAc 3:1) [UV].
1H NMR (600 MHz, CDCl3): δ = 7.72 (d, J = 8.2 Hz, 2 H), 7.30 (d, J = 8.2 Hz, 2 H), 7.24–7.17 (m, 3 H), 7.07 (d, J = 8.0 Hz, 2 H), 5.53–5.47 (m, 1 H), 5.46–5.38 (m, 1 H), 4.47 (t, J = 6.2 Hz, 1 H), 3.52–3.47 (m, 2 H), 3.02 (s, 2 H), 2.52–2.50 (m, 2 H), 2.42 (s, 3 H), 0.95 (s, 9 H).
13C NMR (150 MHz, CDCl3): δ = 179.8, 170.2, 143.7, 137.0, 134.3, 130.6, 130.3, 129.9, 128.2, 127.4, 127.2, 126.5, 73.8, 44.9, 42.9, 39.4, 33.8, 26.5, 21.6.
HRMS (ESI): m/z [M + H]+ calcd for C25H31N2O4S: 455.1999; found: 455.1992.
#
(E)-4-Benzyl-4-(4-hydroxybut-2-en-1-yl)-2-(4-methoxyphenyl)oxazol-5(4H)-one (5a)
Colorless oil; 81% yield, 28.4 mg; Rf = 0.25 (PE/EtOAc 3:1) [UV].
1H NMR (400 MHz, CDCl3): δ = 7.82–7.73 (m, 2 H), 7.17–7.12 (m, 5 H), 6.92–6.87 (m, 2 H), 5.85–5.78 (m, 1 H), 5.62–5.54 (m, 1 H), 4.03 (d, J = 5.4 Hz, 2 H), 3.84 (s, 3 H), 3.16 (q, J = 13.4 Hz, 2 H), 2.78–2.65 (m, 2 H).
13C NMR (150 MHz, CDCl3): δ = 179.3, 163.2, 159.8, 135.2, 134.5, 130.3, 129.8, 128.3, 127.3, 124.3, 117.9, 114.2, 74.7, 63.2, 55.6, 43.3, 40.2.
HRMS (ESI): m/z [M + Na]+ Calcd for C21H21NO4Na: 374.1363; found: 374.1167.
#
Methyl (E)-2-Benzyl-2-(4-methoxybenzamido)-6-((4-methylphenyl)sulfonamido)hex-4-enoate (6a)
In a test tube, 3a (50.4 mg, 0.1 mmol) was dissolved in MeOH (1.0 mL). Then, K2CO3 (20.7 mg, 0.15 mmol) was added. The reaction mixture was stirred at rt until 3a was consumed (determined by TLC). The residue was purified by silica gel flash chromatography (PE/EtOAc 1:1) to afford product 6a as a colorless oil; 89% yield, 47.7 mg; Rf = 0.31 (PE/EtOAc 1:1) [UV].
1H NMR (400 MHz, CDCl3): δ = 7.64 (dd, J = 12.4, 8.4 Hz, 4 H), 7.25 (d, J = 7.7 Hz, 2 H), 7.21–7.13 (m, 3 H), 6.99–6.97 (m, 2 H), 6.90 (d, J = 8.6 Hz, 2 H), 6.78 (s, 1 H), 5.50–5.36 (m, 2 H), 4.38–4.35 (m, 1 H), 3.86–3.84 (m, 1 H), 3.84 (s, 3 H), 3.79 (s, 3 H), 3.50 (dd, J = 14.0, 6.2 Hz, 1 H), 3.41 (t, J = 5.8 Hz, 2 H), 3.12 (d, J = 13.6 Hz, 1 H), 2.62 (dd, J = 14.0, 7.2 Hz, 1 H), 2.40 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 173.4, 166.4, 162.4, 143.6, 136.8, 136.1, 129.8, 129.7, 129.3, 128.7, 128.4, 128.2, 127.3, 127.2, 127.1, 113.9, 66.4, 55.6, 53.0, 45.2, 40.5, 38.0, 21.6.
HRMS (ESI): m/z [M + H]+ calcd for C29H33N2O6S: 537.2054; found: 537.2050.
#
(E)-2-Benzyl-2-(4-methoxybenzamido)-6-((4-methylphenyl)sulfonamido)hex-4-enoic Acid (7a)
In a test tube, 3a (50.4 mg, 0.1 mmol) was dissolved in MeCN (1.0 mL). Then, HCl (0.3 mmol) was added. The reaction mixture was stirred at rt until 3a was consumed (determined by TLC). The residue was purified by silica gel flash chromatography (CH2Cl2/MeOH 30:1) to afford product 7a as a white solid; 82% yield, 42.8 mg; mp 67.8–69.2 °C; Rf = 0.25 (CH2Cl2/MeOH 30:1) [UV].
1H NMR (400 MHz, CD3OD): δ = 7.64 (d, J = 8.2 Hz, 2 H), 7.56 (d, J = 8.8 Hz, 2 H), 7.29 (d, J = 8.2 Hz, 2 H), 7.07–6.94 (m, 5 H), 6.82 (d, J = 8.8 Hz, 2 H), 5.35 (dt, J = 14.4, 7.0 Hz, 1 H), 5.49–5.31 (m, 1 H), 3.82 (s, 3 H), 3.60 (d, J = 12.8 Hz, 1 H), 3.36–3.31 (m, 2 H), 3.26–3.15 (m, 2 H), 2.58 (dd, J = 13.2, 6.4 Hz, 1 H), 2.29 (s, 3 H).
13C NMR (100 MHz, CD3OD): δ = 167.1, 162.3, 143.1, 137.9, 137.4, 129.6, 129.2, 128.9, 128.1, 127.8, 127.8, 127.4, 126.7, 125.7, 113.3, 54.5, 44.7, 40.3, 38.0, 20.0.
HRMS (ESI): m/z [M + H]+ calcd for C28H31N2O6S: 523.1897; found: 523.1892.
#
#
Conflict of Interest
The authors declare no conflict of interest.
Supporting Information
- Supporting information for this article is available online at https://doi-org.accesdistant.sorbonne-universite.fr/10.1055/a-1878-8084.
- Supporting Information
-
References
- 1 Venkatraman J, Shankaramma SC, Balaram P. Chem. Rev. 2001; 101: 3131
- 2 Liu WX, Wang R. Med. Res. Rev. 2012; 32: 536
- 3a Nájera C, Sansano JM. Chem. Rev. 2007; 107: 4584
- 3b Hyslop JF, Lovelock SL, Sutton PW, Brown KK, Watson AJ. B, Roiban G.-D. Angew. Chem. Int. Ed. 2018; 57: 13821
- 3c Cativiela C, Ordóňez M, Viveros-Ceballos JL. Tetrahedron 2020; 76: 130875
- 4a Fisk JS, Mosey RA, Tepe JJ. Chem. Soc. Rev. 2007; 36: 1432
- 4b de Castro PP, Carpanez AG, Amarante GW. Chem. Eur. J. 2016; 22: 10294
- 4c Ma C, Zhou J.-Y, Zhang Y.-Z, Mei G.-J, Shi F. Angew. Chem. Int. Ed. 2018; 57: 5398
- 4d Marra IF. S, de Castro PP, Amarante GW. Eur. J. Org. Chem. 2019; 5830
- 5a Cabrera S, Reyes E, Alemán J, Milelli A, Kobbelgaard S, Jørgensen KA. J. Am. Chem. Soc. 2008; 130: 12031
- 5b Terada M, Tanaka H, Sorimachi K. J. Am. Chem. Soc. 2009; 131: 3430
- 5c Terada M, Moriya K, Kanomata K, Sorimachi K. Angew. Chem. Int. Ed. 2011; 50: 12586
- 5d Zhou H, Yang H, Liu M, Xia C, Jiang G. Org. Lett. 2014; 16: 5350
- 5e Zhang J, Liu X, Wu C, Zhang P, Chen J, Wang R. Eur. J. Org. Chem. 2014; 7104
- 5f Kalek M, Fu GC. J. Am. Chem. Soc. 2015; 137: 9438
- 5g Wei X, Liu D, An Q, Zhang W. Org. Lett. 2015; 17: 5768
- 5h Wang T, Yu Z, Hoon DL, Phee CY, Lan Y, Lu Y. J. Am. Chem. Soc. 2016; 138: 265
- 5i Yoshioka K, Yamada K, Uraguchi D, Ooi T. Chem. Commun. 2017; 53: 5495
- 5j Zhang L, Han Y, Huang A, Zhang P, Li P, Li W. Org. Lett. 2019; 21: 7415
- 5k Zhang Z, Xiao F, Wu H.-M, Dong X.-Q, Wang C.-J. Org. Lett. 2020; 22: 569
- 6a Lu G, Birman VB. Org. Lett. 2011; 13: 356
- 6b Wang C, Luo H.-W, Gong L.-Z. Synlett 2011; 992
- 6c Rodríguez-Docampo Z, Quigley C, Tallon S, Connon SJ. J. Org. Chem. 2012; 77: 2407
- 6d Palacio C, Connon SJ. Eur. J. Org. Chem. 2013; 5398
- 6e Yu K, Liu X, Lin X, Lin L, Feng X. Chem. Commun. 2015; 51: 14897
- 6f Tallon S, Manoni F, Connon SJ. Angew. Chem. Int. Ed. 2015; 54: 813
- 6g Zhang Y.-C, Yang Q, Yang X, Zhu Q.-N, Shi F. Asian J. Org. Chem. 2016; 5: 914
- 6h Mandai H, Hongo K, Fujiwara T, Fujii K, Mitsudo K, Suga S. Org. Lett. 2018; 20: 4811
- 6i Xie M.-S, Huang B, Li N, Tian Y, Wu X.-X, Deng Y, Qu G.-R, Guo H.-M. J. Am. Chem. Soc. 2020; 142: 19226
- 7a Dong S, Liu X, Zhu Y, He P, Lin L, Feng X. J. Am. Chem. Soc. 2013; 135: 10026
- 7b Liu X, Wang Y, Yang D, Zhang J, Liu D, Su W. Angew. Chem. Int. Ed. 2016; 55: 8100
- 7c Yu X.-Y, Chen J.-R, Wei Q, Cheng H.-G, Liu Z.-C, Xiao W.-J. Chem. Eur. J. 2016; 22: 6774
- 7d Zhang S.-Y, Lv M, Yin S.-J, Li N.-K, Zhang J.-Q, Wang X.-W. Adv. Synth. Catal. 2016; 358: 143
- 7e Zhang L, Liu Y, Liu K, Liu Z, He N, Li W. Org. Biomol. Chem. 2017; 15: 8743
- 7f Zhou J, Wang M.-L, Gao X, Jiang G.-F, Zhou Y.-G. Chem. Commun. 2017; 53: 3531
- 7g Ruan S, Lin X, Xie L, Lin L, Feng X, Liu X. Org. Chem. Front. 2018; 5: 32
- 7h Lin X, Fang F, Lin W, Liu Z, Chang X, Li P, Li W. Asian. J. Org. Chem. 2020; 9: 1187
- 7i Yuan W.-C, Quan B.-X, Zhao J.-Q, You Y, Wang Z.-H, Zhou M.-Q. J. Org. Chem. 2020; 85: 11812
- 7j Xie L, Li Y, Dong S, Feng X, Liu X. Chem. Commun. 2021; 57: 239
- 8a Zhao H.-W, Ding W.-Q, Wang L.-R, Guo J.-M, Song X.-Q, Wu H.-H, Tang Z, Fan X.-Z, Bi X.-F. Eur. J. Org. Chem. 2020; 5557
- 8b Liu Z, Feng X, Xu J, Jiang X, Cai X. Tetrahedron Lett. 2020; 61: 151694
- 9a Feng J.-J, Zhang J. ACS Catal. 2016; 6: 6651
- 9b Rivinoja DJ, Gee YS, Gardiner MG, Ryan JH, Hyland CJ. T. ACS Catal. 2017; 7: 1053
- 9c Gao J, Zhang J, Fang S, Feng J, Lu T, Du D. Org. Lett. 2020; 22: 7725
- 9d Drew MA, Tague AJ, Richardson C, Pyne SG, Hyland CJ. T. Org. Lett. 2021; 23: 4635
- 9e Niu B, Wei Y, Shi M. Org. Chem. Front. 2021; 8: 3475
- 9f Xiao S, Chen B, Jiang Q, He L, Chu W.-D, He C.-Y, Liu Q.-Z. Org. Chem. Front. 2021; 8: 3729
- 10a Trost BM, Fandrick DR, Brodmann T, Stiles DT. Angew. Chem. Int. Ed. 2007; 46: 6123
- 10b Ohno H. Chem. Rev. 2014; 114: 7784
- 10c Zhuo C.-X, Zheng C, You S.-L. Acc. Chem. Res. 2014; 47: 2558
- 10d Lin T.-Y, Wu H.-H, Feng J.-J, Zhang J. ACS Catal. 2017; 7: 4047
- 10e Lin T.-Y, Wu H.-H, Feng J.-J, Zhang J. Org. Lett. 2017; 19: 2897
- 10f Pham QH, Tague AJ, Richardson C, Hyland CJ. T, Pyne SG. Chem. Sci. 2021; 12: 12695
- 10g Pàmies O, Margalef J, Cañellas S, James J, Judge E, Guiry PJ, Moberg C, Bäckvall J.-E, Pfaltz A, Pericàs MA, Diéguez M. Chem. Rev. 2021; 121: 4373
For some recent examples:
For some examples, see:
For some recent examples, see:
For some recent examples, see:
Corresponding Author
Publication History
Received: 15 April 2022
Accepted after revision: 20 June 2022
Accepted Manuscript online:
20 June 2022
Article published online:
27 July 2022
© 2022. Thieme. All rights reserved
Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany
-
References
- 1 Venkatraman J, Shankaramma SC, Balaram P. Chem. Rev. 2001; 101: 3131
- 2 Liu WX, Wang R. Med. Res. Rev. 2012; 32: 536
- 3a Nájera C, Sansano JM. Chem. Rev. 2007; 107: 4584
- 3b Hyslop JF, Lovelock SL, Sutton PW, Brown KK, Watson AJ. B, Roiban G.-D. Angew. Chem. Int. Ed. 2018; 57: 13821
- 3c Cativiela C, Ordóňez M, Viveros-Ceballos JL. Tetrahedron 2020; 76: 130875
- 4a Fisk JS, Mosey RA, Tepe JJ. Chem. Soc. Rev. 2007; 36: 1432
- 4b de Castro PP, Carpanez AG, Amarante GW. Chem. Eur. J. 2016; 22: 10294
- 4c Ma C, Zhou J.-Y, Zhang Y.-Z, Mei G.-J, Shi F. Angew. Chem. Int. Ed. 2018; 57: 5398
- 4d Marra IF. S, de Castro PP, Amarante GW. Eur. J. Org. Chem. 2019; 5830
- 5a Cabrera S, Reyes E, Alemán J, Milelli A, Kobbelgaard S, Jørgensen KA. J. Am. Chem. Soc. 2008; 130: 12031
- 5b Terada M, Tanaka H, Sorimachi K. J. Am. Chem. Soc. 2009; 131: 3430
- 5c Terada M, Moriya K, Kanomata K, Sorimachi K. Angew. Chem. Int. Ed. 2011; 50: 12586
- 5d Zhou H, Yang H, Liu M, Xia C, Jiang G. Org. Lett. 2014; 16: 5350
- 5e Zhang J, Liu X, Wu C, Zhang P, Chen J, Wang R. Eur. J. Org. Chem. 2014; 7104
- 5f Kalek M, Fu GC. J. Am. Chem. Soc. 2015; 137: 9438
- 5g Wei X, Liu D, An Q, Zhang W. Org. Lett. 2015; 17: 5768
- 5h Wang T, Yu Z, Hoon DL, Phee CY, Lan Y, Lu Y. J. Am. Chem. Soc. 2016; 138: 265
- 5i Yoshioka K, Yamada K, Uraguchi D, Ooi T. Chem. Commun. 2017; 53: 5495
- 5j Zhang L, Han Y, Huang A, Zhang P, Li P, Li W. Org. Lett. 2019; 21: 7415
- 5k Zhang Z, Xiao F, Wu H.-M, Dong X.-Q, Wang C.-J. Org. Lett. 2020; 22: 569
- 6a Lu G, Birman VB. Org. Lett. 2011; 13: 356
- 6b Wang C, Luo H.-W, Gong L.-Z. Synlett 2011; 992
- 6c Rodríguez-Docampo Z, Quigley C, Tallon S, Connon SJ. J. Org. Chem. 2012; 77: 2407
- 6d Palacio C, Connon SJ. Eur. J. Org. Chem. 2013; 5398
- 6e Yu K, Liu X, Lin X, Lin L, Feng X. Chem. Commun. 2015; 51: 14897
- 6f Tallon S, Manoni F, Connon SJ. Angew. Chem. Int. Ed. 2015; 54: 813
- 6g Zhang Y.-C, Yang Q, Yang X, Zhu Q.-N, Shi F. Asian J. Org. Chem. 2016; 5: 914
- 6h Mandai H, Hongo K, Fujiwara T, Fujii K, Mitsudo K, Suga S. Org. Lett. 2018; 20: 4811
- 6i Xie M.-S, Huang B, Li N, Tian Y, Wu X.-X, Deng Y, Qu G.-R, Guo H.-M. J. Am. Chem. Soc. 2020; 142: 19226
- 7a Dong S, Liu X, Zhu Y, He P, Lin L, Feng X. J. Am. Chem. Soc. 2013; 135: 10026
- 7b Liu X, Wang Y, Yang D, Zhang J, Liu D, Su W. Angew. Chem. Int. Ed. 2016; 55: 8100
- 7c Yu X.-Y, Chen J.-R, Wei Q, Cheng H.-G, Liu Z.-C, Xiao W.-J. Chem. Eur. J. 2016; 22: 6774
- 7d Zhang S.-Y, Lv M, Yin S.-J, Li N.-K, Zhang J.-Q, Wang X.-W. Adv. Synth. Catal. 2016; 358: 143
- 7e Zhang L, Liu Y, Liu K, Liu Z, He N, Li W. Org. Biomol. Chem. 2017; 15: 8743
- 7f Zhou J, Wang M.-L, Gao X, Jiang G.-F, Zhou Y.-G. Chem. Commun. 2017; 53: 3531
- 7g Ruan S, Lin X, Xie L, Lin L, Feng X, Liu X. Org. Chem. Front. 2018; 5: 32
- 7h Lin X, Fang F, Lin W, Liu Z, Chang X, Li P, Li W. Asian. J. Org. Chem. 2020; 9: 1187
- 7i Yuan W.-C, Quan B.-X, Zhao J.-Q, You Y, Wang Z.-H, Zhou M.-Q. J. Org. Chem. 2020; 85: 11812
- 7j Xie L, Li Y, Dong S, Feng X, Liu X. Chem. Commun. 2021; 57: 239
- 8a Zhao H.-W, Ding W.-Q, Wang L.-R, Guo J.-M, Song X.-Q, Wu H.-H, Tang Z, Fan X.-Z, Bi X.-F. Eur. J. Org. Chem. 2020; 5557
- 8b Liu Z, Feng X, Xu J, Jiang X, Cai X. Tetrahedron Lett. 2020; 61: 151694
- 9a Feng J.-J, Zhang J. ACS Catal. 2016; 6: 6651
- 9b Rivinoja DJ, Gee YS, Gardiner MG, Ryan JH, Hyland CJ. T. ACS Catal. 2017; 7: 1053
- 9c Gao J, Zhang J, Fang S, Feng J, Lu T, Du D. Org. Lett. 2020; 22: 7725
- 9d Drew MA, Tague AJ, Richardson C, Pyne SG, Hyland CJ. T. Org. Lett. 2021; 23: 4635
- 9e Niu B, Wei Y, Shi M. Org. Chem. Front. 2021; 8: 3475
- 9f Xiao S, Chen B, Jiang Q, He L, Chu W.-D, He C.-Y, Liu Q.-Z. Org. Chem. Front. 2021; 8: 3729
- 10a Trost BM, Fandrick DR, Brodmann T, Stiles DT. Angew. Chem. Int. Ed. 2007; 46: 6123
- 10b Ohno H. Chem. Rev. 2014; 114: 7784
- 10c Zhuo C.-X, Zheng C, You S.-L. Acc. Chem. Res. 2014; 47: 2558
- 10d Lin T.-Y, Wu H.-H, Feng J.-J, Zhang J. ACS Catal. 2017; 7: 4047
- 10e Lin T.-Y, Wu H.-H, Feng J.-J, Zhang J. Org. Lett. 2017; 19: 2897
- 10f Pham QH, Tague AJ, Richardson C, Hyland CJ. T, Pyne SG. Chem. Sci. 2021; 12: 12695
- 10g Pàmies O, Margalef J, Cañellas S, James J, Judge E, Guiry PJ, Moberg C, Bäckvall J.-E, Pfaltz A, Pericàs MA, Diéguez M. Chem. Rev. 2021; 121: 4373
For some recent examples:
For some examples, see:
For some recent examples, see:
For some recent examples, see:
