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DOI: 10.1055/a-2112-2353
Visible-Light-Induced Metal-Free Selenation of Tryptamines/3-Substituted Indoles
Generous financial support from Science and Engineering Research Board (SERB) (CRG/2021/006502) and Department of Atomic Energy, Government of India (201804BRE02RP04978-BRNS.
Abstract
Visible-light-mediated novel metal-free, oxidant-free phosphoric acid-catalyzed method for the synthesis of 2-selanyl NHCbz-tryptamines/3-subtituted indoles is presented. This direct C-2 selenation strategy, with environmental benign conditions by reaction of tryptamines/3-substituted indoles and diaryl/dialkyl selenides, allows access to a wide range of 2-aryl/alkylselanyl NHCbz-tryptamines/3-substituted indoles. An experimental investigation using UV/Vis, cyclic voltammetry, and controlled experiments sheds light on the plausible mechanism.
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The incorporation of selenium into organic scaffolds is not only pivotal for understanding redox processes of biological system,[1] but also plays an important role in pharmaceuticals[2] wherein selenium-containing molecules serve as synthetic intermediates[3] and catalysts for the preparation of various bioactive compounds. In addition to the naturally bioactive scaffolds, synthetic 2-selanylindole core also acts as a precursor for numerous biologically active compounds.[1] For example, novel cyclic peptide ITFUDLLWYYGKK[4] containing a specific indolyl-selanyl bridge acts as an anti-infective agent (Figure [1]). As a consequence, substantial efforts have been employed by the scientific community for the construction of selective C–Se bonds. In this regard, several synthetic protocols have been reported for 3-selanylindole formation.[5] The commonly reported methodologies involve the reaction of heterocycle with diphenyl diselenide in the presence of transition metals such as iron (II),[6] copper,[7], Ag,[8] and Mn (Figure [1]).[9] Other established methodologies include the in situ formation of highly electrophilic species from diselenide, which can be further modified using electron-rich indoles/heterocycles. Nevertheless, most of these strategies suffer several limitations such as the use of stoichiometric amount of additives,[10] toxic oxidants,[11] and harsh conditions with high temperature requirement.[12]
Recently, the use of visible light has been demonstrated as an excellent approach to facilitate synthetic organic transformations.[13] Visible light has relatively low energy and can serve as an everlasting energy reservoir. A large number of reports utilizing visible light for organic transformations involve the use of transition metal complexes[5a] based on Ir and Ru. These complexes have excellent redox potential and photophysical properties but usually have restricted usage due to their high cost, toxicity, and non-environmentally friendly nature.
Interestingly, organic dyes have been employed to obtain 3-selanylindole via photochemical reactions.[5b] It is worth mentioning that regardless of the progress attained by these strategies, they have not been successful in obtaining C-2 selenated adduct under mild metal-free protocol.[5a] [b] [14] Sun et al. have reported electrochemical functionalization of C–H activation of indoles, which deploys an alternative strategy and employs electrons avoiding the essence of stoichiometric amounts of oxidants and reductants.[14] However, this approach limits its scope to only few indoles. In fact, simple indoles like 3-methyl-1H-indole could not undergo selenation at the C2 position of the indole ring.
Another important class of pharmaceutically relevant scaffold is tryptamine,[15] an indole containing scaffold, which constitutes an important core nucleus of many complex natural products of high significance in drug discovery.[16] A number of naturally occurring, synthetic and semi-synthetic pharmaceuticals are based on the tryptamine skeleton. Transition-metal-catalyzed C2/C3–H activation of indole core (tryptamines) offers robust synthetic strategies to deliver functionalized cores.[17] However, to the best of our knowledge, only few reports have demonstrated the synthesis of C-2 selanyltryptophan derivatives using different selenation reagent[18] while with diphenyl diselenide only one report has been published.[19] On the other hand, 2-selanyltryptamine derivatives under visible light with very mild reaction conditions have not been explored yet. Thus, development of new synthetic methodologies for selective C-2 selenation is highly desirable. Our strategy focuses on addressing this issue and developing an efficient protocol to deliver C-2 selenated products (Figure [1]).
We began our investigation with NHCbz-protected tryptamine 1a and diphenyl diselenide (2a) as a selenating reagent in the presence of oxygen atmosphere at room temperature under blue light irradiation. Unfortunately, we did not observe any product formation (Table [1], entry 1). When an additive diphenyl phosphate (DPP) was added, formation of desired C-2 Cbz-tryptamine selenide adduct was observed in good yield (entry 2). Further, we examined the effect of different solvents such as CH2Cl2, MeCN, DMF, and acetone, and the desired selenide adduct was obtained in moderate to good yield (entries 3–6). Surprisingly, when the reaction was performed in DMSO, only trace amount of desired selenide adduct was formed (entry 7). Gratifyingly, when the reaction was performed in the polar aprotic solvent ethyl acetate, a substantial increase in the reactivity of the corresponding selenide adduct was obtained (entry 8). Additionally, good yields were also obtained in hexafluoroisopropanol (HFIP) and MeOH (entries 9, 10). When TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl) as an oxidant was employed, no product formation was observed (entry 11). Moreover, moist condition was also tolerated affording the desired adduct in slightly lower yield (entry 13). However, in the absence of light in dark condition, the reaction failed to proceed (entry 12).
a Reaction conditions: NHCbz-tryptamine 1a and diphenyl diselenide (2a), DPP (10 mol%), under O2, 24 h.
b NMR yield using mesitylene as internal standard. N.D.: Not detected.
c Reaction was conducted in the dark.
d In the presence of 18 μL H2O.
With the optimized conditions in hand, we investigated the tolerance of metal-free selenation strategy towards functional indole cores 1 and aryl diselenide 2 (Scheme [1]). NHCbz-protected tryptamine 1a could afford C-2 selenated product 3a in excellent yield. Next, while screening the effect of protecting group towards phosphoric acid for a metal-free approach, it was observed that the indolyl N-methyl-substituted NHCbz-tryptamine was found to be a good substrate, affording the corresponding adduct 3b in good yield. NHCbz-tryptamine bearing 5-OMe group at benzo core afforded the selanyl product 3c in good yield. Encouraged by the initial results, we next investigated the scope of Boc-protected tryptamine derivative for the present protocol, where the corresponding product 3d was obtained in excellent yield. The desired product 3d was unambiguously confirmed by NMR spectroscopy and single crystal X-ray structure analysis (Figure [2]).[20] Furthermore, scope of this strategy was validated with 3-methylindole and 5-bromo-3-methylindole, furnishing the selenation products 3e and 3f in good to moderate yields. Indole bearing cyclic chain at C-3 position showed great reaction efficiency towards optimized protocol affording C-2 selenation products 3g and 3h in good yields. Further exploration with ester group containing indole afforded the desired product 3i in good yield.
Owing to the importance of Se group on indoles, it would be highly intriguing to introduce selenium on bioactive core bearing indoles. To our delight, biomolecule and druggable scaffolds such as menthol, protected d-galactose, naproxen, and cholic acid tethered indoles were subjected to standard condition that rendered the desired products 3j–n in moderate to good yields.
Redox active ester containing indole core was also compatible under optimized conditions giving the desired product 3o in good yield. Subsequently, functional group tolerance on diaryl diselenide was investigated to conclude the versatility of the protocol. To our delight, p-fluoro- and p-bromo-substituted diselenide underwent smooth transformation to furnish the desired adducts 3p and 3q in moderate to good yields. The 1-naphthyl- and 2-naphthyl-substituted diselenides gave the selanyl products 3r and 3s in good yields. Gratifyingly cyclohexyl diselenide underwent smooth transformation to give 3t, albeit in low yield.
To demonstrate the utility of our transformation, we conducted the reaction in the presence of sunlight. The reaction also proceeded smoothly furnishing the desired product in good yield (Scheme [2]). To probe the intermediacy of the radical generation from 2a, the reaction was carried out in the presence of radical quenchers TEMPO and BHT. Under these conditions, product 3a was not observed and complete quenching of the reaction was observed. When reaction was performed in the absence of oxygen in argon environment, the corresponding adduct was not formed (Scheme [3]).
For establishing the role of light and to get insight in the reaction mechanism, the UV/visible spectroscopic study was also carried out for tryptamine and diphenyl diselenide. The absorption spectra of indole 1a, 2a, and the reaction mixture were recorded in methanol independently, which show clear distinct absorption in the range 260–290 nm, while diphenyl diselenide (2a) absorbs in the UV range in MeOH (Figure [3]). The absorbance of diphenyl phosphate with each substrate was also recorded. Subsequently, absorbance was recorded before irradiation and after 4 hours of irradiation under blue light. A new absorption peak in the range of 240–250 nm indicates the dissociation of 2a to form selanyl radical in blue light.
Effect of catalyst on each substrate was also studied and the corresponding absorbance was recorded before irradiation and after 4 hours of irradiation. Interestingly a new absorption peak was observed for 2a post irradiation, however, no discernible change in the absorbance spectrum of 1a was observed (for comparison: see SI). Thus, the UV studies clearly indicate the role of visible light in facilitating this transformation.
To better understand the role of diphenyl phosphate in this protocol, we first examined the electro-oxidation potential of 1i alone and 1i in the presence of diphenyl phosphate. The cyclic voltammetry (CV) results suggest that oxidation of 1i-phosphate complex is kinetically more favorable than direct oxidation of 1i (Figure [4]), this observation was in accordance of tryptamine-phosphate complex shown by Knowles.[21]
To further validate these observations, fluorescence quenching experiments were carried out with 2a, and DPP (Figure [5]). The fluorescence quenching effect was witnessed in the presence of diphenyl diselenide (2a), which might be attributed to the formation of complex.
Based on control experiments and findings from previous studies,[5] [12] [17] we speculate that visible light excites diaryl diselenide 2 to its electronically excited state, thereby subsequently undergoing homolytic cleavage to give selanyl radical ArSe . , which further undergoes single electron oxidation to produce electrophilic species ArSe+ and superoxide anion (O2 .– ). It is envisioned that a prospective catalytic cycle wherein phosphoric acid (DPP) would first form a hydrogen bonded adduct with the substrate NH or NHCbz of 1, followed by resultant adduct capturing the electrophilic species to produce the corresponding intermediate. An intermolecular hydrogen abstraction by superoxide anion occurs, which furnishes the desired selanyl adduct thus completing the catalytic cycle and restoring the aromaticity (see: Supporting Information).
In summary, a metal-free, economical, and highly efficient protocol for the C–H activation of tryptamines/3-substituted indoles for the synthesis of C-2 selanyl adduct was developed. Diverse substitution patterns on substrates were well tolerated, highlighting the greener synthetic potential of this protocol. Further, bioactive tethered indoles were well tolerated.
All the reactions were performed under O2 atmosphere. A Bruker AV-instrument (400 and 500 MHz, and 100, 125 MHz, respectively) was used to record 1H and 13C NMR spectra in deuterated solvents with residual protonated solvent signals as internal reference. 1H NMR data are reported as chemical shift (d, ppm), multiplicity (s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet), integration, coupling constant (Hz). 13C NMR data are recorded in terms of chemical shift (d, ppm). A PerkinElmer FT-IR spectrophotometer was used to record IR spectra and values are reported in frequency of absorption. An MS-TOF mass spectrometer and ESI mass spectrometer were used to record low-resolution and high-resolution mass spectra. Column chromatographic separations were carried out on silica gel (100–200 mesh).
For the preparation of substrates and other details, see the Supporting Information.
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Visible-Light-Induced Metal-Free Selenation of Tryptamines and Indoles and 1; General Procedure
NHCbz tryptamine/indole 1 (0.2 mmol, 1.0 equiv), aryl diselenide 2 (0.2 mmol, 0.1 equiv), and diphenyl phosphate (DPP, 10 mol%) were added to a 5 mL round-bottom flask provided with a magnetic stir bar in EtOAc (O2 purged, 2 mL). The reaction mixture was stirred for 24–30 h under blue light. The progress of the reaction was monitored by TLC. After completion of the reaction, the solvent was removed on rotary evaporator under vacuum. The residue was purified by flash column chromatography on silica gel (EtOAc/PE 1:3, v/v) to afford the desired product.
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Benzyl (2-(2-(Phenylselanyl)-1H-indol-3-yl)ethyl)carbamate (3a)
Brown liquid; yield: 78 mg (87%).
1H NMR (500 MHz, CDCl3): δ = 8.38 (s, 1 H), 7.66 (d, J = 8.0 Hz, 1 H), 7.36–7.32 (m, 6 H), 7.24 (t, J = 7.6 Hz, 1 H), 7.19–7.13 (m, 6 H), 5.09 (s, 2 H), 4.83 (s, 1 H), 3.47 (q, J = 6.6 Hz, 2 H), 3.12 (t, J = 6.8 Hz, 2 H).
13C NMR (126 MHz, CDCl3): δ = 156.5, 137.8, 136.7, 132.0, 129.5, 129.5, 128.6, 128.2, 128.1, 127.7, 126.7, 123.4, 120.4, 120.0, 119.3, 119.3, 66.6, 41.8, 26.3.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C24H23N2O2SeNa: 451.0919; found: 451.0928.
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Benzyl (2-(1-Methyl-2-(phenylselanyl)-1H-indol-3-yl)ethyl)carbamate (3b)
Yellow sticky liquid; yield: 65 mg (70%).
1H NMR (500 MHz, CDCl3): δ = 7.73 (d, J = 8.0 Hz, 1 H), 7.36 (tt, J = 11.2, 5.0 Hz, 8 H), 7.18 (q, J = 9.8, 8.5 Hz, 5 H), 7.13–7.01 (m, 3 H), 5.10 (s, 2 H), 4.82 (s, 1 H), 3.78 (s, 4 H), 3.49 (q, J = 6.6 Hz, 2 H), 3.21 (t, J = 6.9 Hz, 2 H).
13C NMR (126 MHz, CDCl3): δ = 156.4, 138.5, 136.8, 132.6, 129.6, 128.6, 128.3, 128.2, 127.1, 126.4, 123.7, 123.2, 120.6, 119.7, 119.5, 110.1, 66.6, 42.1, 31.6, 26.9.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C25H25N2O2SeNa: 465.1075; found: 465.1086.
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Benzyl (2-(5-Methoxy-2-(phenylselanyl)-1H-indol-3-yl)ethyl)carbamate (3c)
Brown liquid; yield 77 mg (80%).
1H NMR (500 MHz, CDCl3): δ = 8.19 (s, 1 H), 7.62 (d, J = 6.8 Hz, 1 H), 7.35–7.30 (m, 6 H), 7.15 (dd, J = 11.5, 4.4 Hz, 4 H), 7.08 (s, 1 H), 6.90 (dd, J = 9.2, 2.7 Hz, 1 H), 5.09 (d, J = 13.4 Hz, 2 H), 4.80 (d, J = 5.9 Hz, 1 H), 3.84 (s, 3 H), 3.50–3.42 (m, 2 H), 3.07 (q, J = 5.2, 3.7 Hz, 2 H).
13C NMR (126 MHz, CDCl3): δ = 156.5, 154.4, 136.7, 135.5, 133.1, 132.2, 131.6, 129.6, 129.5, 128.6, 128.6, 128.2, 128.2, 126.7, 119.7, 114.0, 111.9, 100.6, 66.7, 55.9, 41.7, 26.4.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C25H24N2O3SeNa: 503.0844; found: 503.0850.
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tert-Butyl (2-(2-(Phenylselanyl)-1H-indol-3-yl)ethyl)carbamate (3d)
White solid; yield: 76 mg (92%).
1H NMR (500 MHz, CDCl3): δ = 8.19 (s, 1 H), 7.67 (d, J = 7.9 Hz, 1 H), 7.33 (d, J = 8.2 Hz, 1 H), 7.25 (d, J = 7.3 Hz, 1 H), 7.23 (t, J = 1.2 Hz, 1 H), 7.21–7.13 (m, 7 H), 7.15 (ddd, J = 8.1, 7.0, 1.0 Hz, 1 H), 4.56 (s, 1 H), 3.77–2.73 (m, 6 H), 1.42 (s, 12 H).
13C NMR (126 MHz, CDCl3): δ = 156.0, 137.9, 132.0, 129.7, 129.6, 127.9, 126.8, 123.4, 120.0, 119.3, 111.0, 28.6.
77Se NMR (76 MHz, CDCl3): δ = 262.55.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C21H24N2O2SeNa: 439.0895; found: 439.0906.
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3-Methyl-2-(phenylselanyl)-1H-indole (3e)
Brown liquid; yield: 34 mg (60%).
1H NMR (400 MHz, CDCl3): δ = 7.94 (s, 1 H), 7.60–7.46 (m, 1 H), 7.25 (dt, J = 8.2, 1.0 Hz, 1 H), 7.22–7.17 (m, 1 H), 7.17–7.08 (m, 6 H), 2.39 (s, 3 H).
13C NMR (126 MHz, CDCl3): δ = 137.7, 132.2, 129.5, 129.4, 128.4, 126.5, 123.3, 120.0, 119.7, 119.4, 118.2, 110.9, 10.5.
HRMS (ESI/QTOF): m/z [M]+ calcd for C15H13NSe: 287.0213; found: 287.0211.
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5-Bromo-3-methyl-2-(phenylselanyl)-1H-indole (3f)
White solid; yield: 31 mg (42%).
1H NMR (500 MHz, CDCl3): δ = 8.02 (s, 1 H), 7.74 (t, J = 1.8 Hz, 1 H), 7.31 (dt, J = 8.6, 2.0 Hz, 1 H), 7.24–7.18 (m, 5 H), 7.16 (dd, J = 8.6, 2.6 Hz, 1 H), 2.39 (s, 3 H).
13C NMR (126 MHz, CDCl3): δ = 136.2, 131.7, 130.1, 129.7, 129.7, 129.6, 129.6, 126.8, 125.9, 121.9, 119.9, 119.3, 112.9, 112.3, 112.2, 10.4.
77Se NMR (76 MHz, CDCl3): δ = 265.49.
HRMS (ESI/QTOF): m/z [M + H]+ calcd for C15H13BrNSe: 365.9391; found: 365.9395.
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3-Cyclohexyl-2-(phenylselanyl)-1H-indole (3g)
White solid; yield: 46 mg (65%).
1H NMR (500 MHz, CDCl3): δ = 7.97 (s, 1 H), 7.86 (d, J = 8.0 Hz, 1 H), 7.30 (d, J = 8.2 Hz, 1 H), 7.26–7.17 (m, 6 H), 7.16–7.10 (m, 1 H), 3.15–3.02 (m, 1 H), 2.03 (dd, J = 12.5, 3.4 Hz, 2 H), 1.85 (dq, J = 10.1, 3.1 Hz, 2 H), 1.83–1.75 (m, 3 H), 1.40 (dddd, J = 10.6, 8.2, 5.7, 3.0 Hz, 3 H).
13C NMR (126 MHz, CDCl3): δ = 138.1, 132.6, 129.6, 129.5, 129.3, 126.6, 126.5, 122.9, 120.6, 119.5, 119.3, 117.1, 111.1, 38.3, 33.4, 27.3, 26.4.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C20H21NSeNa: 378.0731; found: 378.0740.
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3-Cyclododecyl-2-(phenylselanyl)-1H-indole (3h)
White solid; yield: 60 mg (68%).
1H NMR (500 MHz, CDCl3): δ = 8.02 (s, 1 H), 7.83 (d, J = 8.0 Hz, 1 H), 7.34 (d, J = 8.2 Hz, 1 H), 7.30–7.27 (m, 2 H), 7.25–7.21 (m, 4 H), 7.15 (t, J = 7.4 Hz, 1 H), 3.38 (t, J = 6.8 Hz, 1 H), 2.12 (ddd, J = 13.7, 7.1, 3.5 Hz, 2 H), 2.02–1.77 (m, 1 H), 1.74–1.70 (m, 2 H), 1.63 (d, J = 6.9 Hz, 2 H), 1.52–1.44 (m, 8 H), 1.38–1.32 (m, 6 H), 1.19 (d, J = 6.7 Hz, 1 H).
13C NMR (126 MHz, CDCl3): δ = 138.4, 132.7, 129.7, 129.4, 128.6, 126.5, 122.8, 120.8, 119.2, 111.1, 32.2, 30.9, 24.6, 24.4, 23.8, 22.7, 22.5.
77Se NMR (95 MHz, CDCl3): δ = 268.66.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C26H33NSeNa: 462.1670; found: 462.1676.
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1,1,1,3,3,3-Hexafluoropropan-2-yl 2-(2-(Phenylselanyl)-1H-indol-3-yl)acetate (3i)
White solid; yield: 68 mg (71%).
1H NMR (500 MHz, CDCl3): δ = 8.27 (s, 1 H), 7.54 (dd, J = 8.0, 1.0 Hz, 1 H), 7.34 (dt, J = 8.1, 1.0 Hz, 1 H), 7.27–7.17 (m, 7 H), 5.77 (pent, J = 6.1 Hz, 1 H), 4.15 (s, 2 H).
13C NMR (126 MHz, CDCl3): δ = 168.45, 137.57, 131.03, 129.89, 129.54, 127.03, 126.99, 123.73, 121.08, 120.52, 118.89, 114.33, 111.11, 67.02 (J = 35.8), 66.75 (J = 35.8), 66.47 (J = 35.8), 66.19 (J = 35.8), 30.96.
19F NMR (471 MHz, CDCl3): δ = –73.18.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C19H13F6NO2SeNa: 503.9907; found: 503.9913.
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(1R,2S,5R)-2-Isopropyl-5-methylcyclohexyl 2-(2-(Phenylselanyl)-1H-indol-3-yl)acetate (3j)
Yellow liquid; yield: 68 mg (73%).
1H NMR (400 MHz, CDCl3): δ = 8.15 (s, 1 H), 7.59 (dd, J = 8.0, 1.1 Hz, 1 H), 7.25–7.20 (m, 3 H), 7.20–7.12 (m, 4 H), 7.10 (ddd, J = 8.1, 7.0, 1.2 Hz, 1 H), 4.62 (td, J = 10.9, 4.4 Hz, 1 H), 3.88 (d, J = 2.8 Hz, 2 H), 1.95–1.87 (m, 1 H), 1.58 (ddd, J = 14.2, 9.0, 3.0 Hz, 3 H), 1.28–1.21 (m, 2 H), 0.96 (dd, J = 12.8, 3.3 Hz, 1 H), 0.82 (d, J = 6.6 Hz, 3 H), 0.71 (d, J = 7.0 Hz, 3 H), 0.59 (d, J = 7.0 Hz, 3 H).
13C NMR (126 MHz, CDCl3): δ = 171.2, 137.8, 131.8, 130.0, 129.5, 127.7, 126.8, 123.5, 120.4, 120.2, 119.7, 117.2, 110.9, 74.8, 47.2, 40.9, 34.4, 32.6, 31.5, 26.2, 23.5, 22.1, 20.8, 16.3.
77Se NMR (95 MHz, CDCl3): δ = 259.14.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C26H31NO2SeNa: 492.1412; found: 492.1430.
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(1R,2S,5R)-2-Isopropyl-5-methylcyclohexyl 4-(2-(Phenylselanyl)-1H-indol-3-yl)butanoate (3k)
Yellow liquid; yield: 75 mg (76%).
1H NMR (500 MHz, CDCl3): δ = 8.20 (s, 1 H), 7.71 (d, J = 7.9 Hz, 1 H), 7.34 (d, J = 8.1 Hz, 1 H), 7.28–7.17 (m, 7 H), 4.75 (td, J = 10.9, 4.4 Hz, 1 H), 2.98 (dd, J = 8.4, 6.8 Hz, 2 H), 2.36 (t, J = 7.4 Hz, 2 H), 2.02 (pent, J = 7.7 Hz, 3 H), 1.91 (pd, J = 7.0, 2.8 Hz, 1 H), 1.71 (ddd, J = 13.3, 7.0, 3.3 Hz, 2 H), 1.51 (ddd, J = 8.9, 4.6, 2.3 Hz, 1 H), 1.39 (tt, J = 12.4, 3.2 Hz, 1 H), 1.09 (qd, J = 13.5, 12.8, 3.8 Hz, 1 H), 0.98 (d, J = 11.6 Hz, 1 H), 0.96–0.89 (m, 7 H), 0.80 (d, J = 6.9 Hz, 3 H).
13C NMR (126 MHz, CDCl3): δ = 173.5, 136.5, 127.6, 122.0, 121.6, 119.3, 119.0, 115.9, 111.2, 74.1, 47.2, 41.1, 34.5, 34.4, 31.5, 26.4, 25.8, 24.7, 23.5, 22.2, 20.9, 16.4.
77Se NMR (95 MHz, CDCl3): δ = 258.19.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C28H35NO2SeNa: 520.1725; found: 520.1708.
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((3aS,5R,5aR,8aR,8bS)-2,2,7,7-Tetramethyltetrahydro-5H-bis([1,3]dioxolo)[4,5-b:4′,5′-d]pyran-5-yl)methyl 2-(2-(Phenylselanyl)-1H-indol-3-yl)acetate (3l)
White solid; yield: 69 mg (60%).
1H NMR (400 MHz, CDCl3): δ = 8.31 (s, 1 H), 7.62 (d, J = 7.9 Hz, 1 H), 7.36–7.01 (m, 8 H), 5.53 (d, J = 5.0 Hz, 1 H), 4.54 (dd, J = 7.9, 2.4 Hz, 1 H), 4.33–4.18 (m, 3 H), 4.09 (dd, J = 7.9, 1.9 Hz, 1 H), 4.03–3.97 (m, 1 H), 3.96 (s, 2 H), 1.43 (d, J = 2.8 Hz, 6 H), 1.31 (s, 3 H), 1.28 (s, 3 H).
13C NMR (126 MHz, CDCl3): δ = 171.5, 137.7, 131.8, 129.8, 129.8, 129.5, 127.5, 126.7, 123.4, 120.4, 120.2, 119.6, 116.5, 111.0, 109.6, 108.8, 96.3, 70.9, 70.7, 70.5, 65.9, 63.8, 31.9, 26.1, 26.0, 25.1, 24.4.
77Se NMR (95 MHz, CDCl3): δ = 261.11, 260.30.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C28H31NO7SeNa: 596.1157; found: 596.1150.
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(R)-2-(6-Methoxynaphthalen-2-yl)propyl 2-(2-(Phenylselanyl)-1H-indol-3-yl)acetate (3m)
White solid; yield: 80 mg (75%).
1H NMR (500 MHz, CDCl3): δ = 8.14 (s, 1 H), 7.63 (dd, J = 8.6, 4.1 Hz, 2 H), 7.53–7.46 (m, 2 H), 7.26 (d, J = 1.1 Hz, 1 H), 7.22 (ddd, J = 7.1, 3.4, 1.5 Hz, 2 H), 7.19 (dd, J = 7.0, 3.0 Hz, 2 H), 7.15 (qd, J = 4.0, 1.8 Hz, 4 H), 7.11 (d, J = 2.5 Hz, 1 H), 7.06 (ddd, J = 8.1, 6.9, 1.1 Hz, 1 H), 4.28 (dd, J = 10.8, 7.0 Hz, 1 H), 4.19 (dd, J = 10.8, 6.9 Hz, 1 H), 3.93 (s, 3 H), 3.89 (d, J = 1.3 Hz, 2 H), 3.15 (q, J = 7.0 Hz, 1 H), 1.29 (d, J = 7.0 Hz, 3 H).
13C NMR (126 MHz, CDCl3): δ = 171.5, 157.5, 138.4, 137.7, 133.6, 131.7, 129.9, 129.5, 129.3, 129.1, 127.6, 127.0, 126.8, 126.4, 125.7, 123.4, 120.4, 120.2, 119.5, 118.8, 116.6, 110.9, 105.7, 69.8, 55.4, 38.9, 32.2, 18.1.
77Se NMR (95 MHz, CDCl3): δ = 261.88.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C30H27NO3SeNa: 552.1048; found: 552.1046.
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(R)-4-((3S,5R,7S,8S,9R,10R,12R,13S,14R,16R)-3,7,12-Trihydroxy-10,13-dimethylhexadecahydro-1H-cyclopenta[a]phenanthren-16-yl)pentyl 2-(2-(Phenylselanyl)-1H-indol-3-yl)acetate (3n)
White solid; yield: 64 mg (45%).
1H NMR (500 MHz, CDCl3): δ = 8.56–8.46 (m, 1 H), 7.69 (d, J = 7.9 Hz, 1 H), 7.62 (d, J = 7.0 Hz, 1 H), 7.34 (d, J = 8.3 Hz, 1 H), 7.27 (s, 1 H), 7.23–7.18 (m, 5 H), 7.16 (s, 1 H), 4.76 (s, 1 H), 4.59 (dt, J = 11.6, 6.4 Hz, 2 H), 3.99 (q, J = 5.1, 3.1 Hz, 2 H), 3.86 (d, J = 4.0 Hz, 2 H), 3.24 (t, J = 7.1 Hz, 2 H), 2.32 (d, J = 3.6 Hz, 2 H), 2.22 (d, J = 4.7 Hz, 2 H), 1.96–1.91 (m, 3 H), 1.82–1.74 (m, 6 H), 1.68–1.66 (m, 2 H), 1.55–1.51 (m, 5 H), 1.30–1.24 (m, 4 H), 1.07 (dd, J = 14.4, 3.2 Hz, 2 H), 0.92 (s, 3 H), 0.67 (s, 3 H).
13C NMR (126 MHz, CDCl3): δ = 174.4, 171.0, 137.9, 131.6, 129.6, 129.5, 129.3, 127.8, 127.8, 126.7, 123.3, 119.9, 119.4, 119.3, 111.1, 74.5, 73.1, 68.4, 64.5, 47.3, 46.6, 42.0, 41.3, 39.6, 35.3, 35.2, 35.0, 34.8, 34.5, 31.4, 30.9, 28.3, 27.5, 26.7, 25.6, 23.3, 22.6, 21.6, 17.4, 12.6.
77Se NMR (95 MHz, CDCl3): δ = 259.84.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C40H60N2O6SeNa: 767.3514; found: 767.3520.
#
2-(3-(2-(Phenylselanyl)-1H-indol-3-yl)propyl)isoindoline-1,3-dione (3o)
Red sticky solid; yield: 69 mg (68%).
1H NMR (500 MHz, CDCl3): δ = 8.18 (s, 1 H), 7.88 (dd, J = 5.5, 3.1 Hz, 2 H), 7.78 (dd, J = 5.5, 3.1 Hz, 2 H), 7.69 (dd, J = 7.8, 1.1 Hz, 1 H), 7.34 (d, J = 8.1 Hz, 1 H), 7.24–7.16 (m, 7 H), 3.04 (t, J = 7.5 Hz, 2 H), 2.68 (t, J = 7.5 Hz, 2 H), 2.12 (pent, J = 7.6 Hz, 2 H).
13C NMR (126 MHz, CDCl3): δ = 169.7, 162.1, 137.8, 134.9, 132.1, 129.6, 129.6, 129.0, 127.6, 126.7, 124.1, 123.6, 122.4, 122.6, 119.9, 119.4, 118.8, 111.1, 30.6, 25.7, 24.9.
HRMS (ESI/QTOF): m/z [M – H]+ calcd for C24H19N2O4Se: 503.0486; found: 503.0506.
#
Benzyl (2-(2-((4-Fluorophenyl)selanyl)-1H-indol-3-yl)ethyl)carbamate (3p)
Red liquid; yield: 38 mg (40%).
1H NMR (500 MHz, CDCl3): δ = 8.20 (s, 1 H), 7.64 (d, J = 8.0 Hz, 1 H), 7.33 (qt, J = 8.3, 4.7 Hz, 6 H), 7.25–7.07 (m, 4 H), 6.88 (t, J = 8.7 Hz, 2 H), 5.10 (d, J = 15.6 Hz, 2 H), 4.77 (s, 1 H), 3.47 (q, J = 6.6 Hz, 2 H), 3.11 (t, J = 6.9 Hz, 2 H).
13C NMR (126 MHz, CDCl3): δ = 163.2, 161.3, 156.5, 137.8, 135.0, 134.9, 132.1, 132.0, 128.6, 128.3, 128.2, 123.6, 120.2, 119.7, 119.3, 116.9, 116.7, 111.1, 77.4, 77.2, 76.9, 66.7, 41.8, 26.4.
19F NMR (471 MHz, CDCl3): δ = –115.09.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C24H21FN2O2SeNa: 491.0644; found: 491.0651.
#
Benzyl (2-(2-((4-Bromophenyl)selanyl)-1H-indol-3-yl)ethyl)carbamate (3q)
Yellow liquid; yield: 64 mg (60%).
1H NMR (400 MHz, CDCl3): δ = 8.15 (s, 1 H), 7.57 (d, J = 8.0 Hz, 1 H), 7.26 (q, J = 4.1 Hz, 6 H), 7.21–7.12 (m, 3 H), 6.95 (d, J = 8.2 Hz, 2 H), 5.00 (s, 2 H), 4.69 (s, 1 H), 3.38 (t, J = 6.6 Hz, 2 H), 3.02 (t, J = 6.9 Hz, 2 H).
13C NMR (126 MHz, CDCl3): δ = 156.5, 137.9, 136.7, 132.6, 132.4, 131.0, 131.0, 128.6, 128.3, 128.2, 127.6, 123.7, 120.9, 120.8, 120.3, 119.4, 118.7, 111.2, 66.7, 41.8, 26.4.
77Se NMR (95 MHz, CDCl3): δ = 260.84.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C24H21BrN2O2SeNa: 550.9843; found: 550.9851.
#
Benzyl (2-(2-(Naphthalen-1-ylselanyl)-1H-indol-3-yl)ethyl)carbamate (3r)
Yellow solid; yield: 50 mg (50%).
1H NMR (500 MHz, CDCl3): δ = 8.27 (s, 1 H), 8.19 (d, J = 8.3 Hz, 1 H), 7.84 (dd, J = 8.0, 1.6 Hz, 1 H), 7.80–7.59 (m, 2 H), 7.58–7.49 (m, 2 H), 7.31 (qd, J = 8.5, 4.0 Hz, 6 H), 7.25–7.09 (m, 4 H), 5.05 (s, 2 H), 4.80 (s, 1 H), 3.47 (q, J = 6.6 Hz, 2 H), 3.14 (t, J = 6.8 Hz, 2 H).
13C NMR (126 MHz, CDCl3): δ = 156.5, 138.0, 136.8, 134.2, 134.1, 132.6, 130.7, 129.9, 128.8, 128.7, 128.6, 128.5, 128.2, 128.1, 127.9, 127.7, 126.9, 126.8, 126.5, 126.4, 126.3, 125.8, 123.3, 120.6, 120.1, 119.2, 118.8, 111.1, 66.6, 41.8, 26.4.
77Se NMR (95 MHz, CDCl3): δ = 264.72.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C28H24N2O2SeNa: 523.0895; found: 523.0881.
#
Benzyl (2-(2-(Naphthalen-2-ylselanyl)-1H-indol-3-yl)ethyl)carbamate (3s)
Yellow solid: yield: 54 mg (54%).
1H NMR (500 MHz, CDCl3): δ = 7.76–7.70 (m, 2 H), 7.65 (dt, J = 13.1, 8.2 Hz, 3 H), 7.45–7.39 (m, 2 H), 7.36–7.27 (m, 6 H), 7.26–7.21 (m, 2 H), 7.15 (t, J = 7.6 Hz, 1 H), 5.03 (s, 2 H), 4.78 (s, 1 H), 3.49 (q, J = 6.6 Hz, 2 H), 3.15 (t, J = 6.8 Hz, 2 H).
13C NMR (126 MHz, CDCl3): δ = 156.5, 137.9, 136.8, 134.2, 132.3, 129.2, 129.2, 128.6, 128.5, 128.3, 128.2, 128.2, 128.1, 127.9, 127.5, 127.3, 126.8, 126.2, 123.5, 120.6, 120.2, 119.5, 119.4, 111.1, 66.6, 41.8, 26.5.
HRMS (ESI/QTOF): m/z [M + Na]+ calcd for C28H24N2O2SeNa: 523.0895; found: 523.0883.
#
Benzyl (2-(2-(Cyclohexylselanyl)-1H-indol-3-yl)ethyl)carbamate (3t)
Yellow liquid; yield: 19 mg (20%).
1H NMR (500 MHz, CDCl3): δ = 8.07 (s, 1 H), 7.60 (d, J = 7.9 Hz, 1 H), 7.32 (dd, J = 15.6, 7.0 Hz, 6 H), 7.20 (t, J = 7.8 Hz, 1 H), 7.10 (s, 1 H), 5.30 (s, 1 H), 5.11 (d, J = 7.2 Hz, 2 H), 4.80 (s, 1 H), 3.50 (d, J = 7.0 Hz, 2 H), 3.10 (s, 2 H), 1.95 (d, J = 12.6 Hz, 2 H), 1.69 (s, 3 H), 1.57 (s, 2 H), 1.22 (s, 3 H).
13C NMR (126 MHz, CDCl3): δ = 156.5, 137.6, 128.6, 128.3, 128.2, 122.9, 120.2, 119.9, 110.8, 66.7, 45.1, 41.9, 34.8, 29.9, 27.0, 25.7.
HRMS (ESI/QTOF): m/z [M – H]+ calcd for C24H27N2O2Se: 455.1238; found: 455.1239.
#
#
Conflict of Interest
The authors declare no conflict of interest.
Acknowledgment
S.S. is grateful to MHRD for a fellowship. A.K. is grateful to PMRF, India, for a fellowship.
Supporting Information
- Supporting information for this article is available online at https://doi-org.accesdistant.sorbonne-universite.fr/10.1055/a-2112-2353.
- Supporting Information
-
References
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Corresponding Author
Publication History
Received: 11 April 2023
Accepted after revision: 19 June 2023
Accepted Manuscript online:
19 June 2023
Article published online:
09 August 2023
© 2023. Thieme. All rights reserved
Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany
-
References
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- 1b Bhabak KP, Mugesh G. Acc. Chem. Res. 2010; 43: 1408
- 1c Sancineto L, Mariotti A, Bagnoli L, Marini F, Desantis J, Iraci N, Santi C, Pannecouque C, Tabarrini O. J. Med. Chem. 2015; 58: 9601
- 1d Stolwijk JM, Garje R, Sieren JC, Buettner GR, Zakharia Y. Antioxidants 2020; 9: 420
- 2 Nogueira CW, Zeni G, Rocha JB. T. Chem. Rev. 2004; 104: 6255
- 3a Garud DR, Koketsu M, Ishihara H. Molecules 2007; 12: 504
- 3b Tanini D, Capperucci A. Adv. Synth. Catal. 2021; 363: 5360
- 4 Buchwald S, Pentelute B, Cohen D, Zhang C. WO Pat 2016205798, 20161222 A1, 2016
- 5a Zhang Q.-B, Ban Y.-L, Yuan P.-F, Peng S.-J, Fang J.-G, Wu L.-Z, Liu Q. Green Chem. 2017; 19: 5559
- 5b Saba S, Rafique J, Franco MS, Schneider AR, Espíndola L, Silva DO, Braga AL. Org. Biomol. Chem. 2018; 16: 880
- 5c Rathore V, Kumar S. Green Chem. 2019; 21: 2670
- 5d Lemir ID, Castro-Godoy WD, Heredia AA, Schmidt LC, Argüello JE. RSC Adv. 2019; 9: 22685
- 6a Du H.-A, Tang R.-Y, Deng C.-L, Liu Y, Li J.-H, Zhang X.-G. Adv. Synth. Catal. 2011; 353: 2739
- 6b Wen Z, Xu J, Wang Z, Qi H, Xu Q, Bai Z, Zhang Q, Bao K, Wu Y, Zhang W. Eur. J. Med. Chem. 2015; 90: 184
- 7a Mandal A, Sahoo H, Baidya M. Org. Lett. 2016; 18: 3202
- 7b Wang J, Li H, Leng T, Liu M, Ding J, Huang X, Wu H, Gao W, Wu G. Org. Biomol. Chem. 2017; 15: 9718
- 7c Murata Y, Otake N, Sano M, Matsumura M, Yasuike S. Asian J. Org. Chem. 2021; 10: 2975
- 8 Wang D.-L, Jiang N.-Q, Cai Z.-J, Ji S.-J. J. Org. Chem. 2021; 86: 9898
- 9 Wang M, Wu Z, Zhu C. Org. Chem. Front. 2017; 4: 427
- 10 Taniguchi N, Onami T. J. Org. Chem. 2004; 69: 915
- 11a Silveira CC, Mendes SR, Wolf L, Martins GM, von Mühlen L. Tetrahedron 2012; 68: 10464
- 11b Prasad CD, Balkrishna SJ, Kumar A, Bhakuni BS, Shrimali K, Biswas S, Kumar S. J. Org. Chem. 2013; 78: 1434
- 11c Zimmermann EG, Thurow S, Freitas CS, Mendes SR, Perin G, Alves D, Jacob RG, Lenardão EJ. Molecules 2013; 18: 4081
- 11d Kumar A, Bhakuni BS, Prasad ChD, Kumar S, Kumar S. Tetrahedron 2013; 69: 5383
- 12a Li Z, Hong J, Zhou X. Tetrahedron 2011; 67: 3690
- 12b Wen Z, Li X, Zuo D, Lang B, Wu Y, Jiang M, Ma H, Bao K, Wu Y, Zhang W. Sci. Rep. 2016; 6: 23986
- 12c Vieira BM, Thurow S, da Costa M, Casaril AM, Domingues M, Schumacher RF, Perin G, Alves D, Savegnago L, Lenardão EJ. Asian J. Org. Chem. 2017; 6: 1635
- 13 König B. Eur. J. Org. Chem. 2017; 1979
- 14 Zhang X, Wang C, Jiang H, Sun L. Chem. Commun. 2018; 54: 8781
- 16a Zhang M.-Z, Mulholland N, Beattie D, Irwin D, Gu Y.-C, Chen Q, Yang G.-F, Clough J. Eur. J. Med. Chem. 2013; 63: 22
- 16b Kousara S, Anjuma SN, Jaleela F, Khana J, Naseema S. J. Pharmacovigil. 2017; 5: 1000239
- 17a Sandtorv AH. Adv. Synth. Catal. 2015; 357: 2403
- 17b Melis N, Secci F, Boddaert T, Aitken DJ, Frongia A. Chem. Commun. 2015; 51: 15272
- 17c Chauhan J, Ravva MK, Gremaud L, Sen S. Org. Lett. 2020; 22: 4537
- 18a Crich D, Davies JW. Tetrahedron Lett. 1989; 30: 4307
- 18b Abdo M, Zhang Y, Schramm VL, Knapp S. Org. Lett. 2010; 12: 2982
- 19 Gao Y.-T, Liu S.-D, Cheng L, Liu L. Chem. Commun. 2021; 57: 3504
- 20 CCDC 2255165 (3d) contains the supplementary crystallographic data for this paper. The data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/structures
- 21 Gentry EC, Rono LJ, Hale ME, Matsuura R, Knowles RR. J. Am. Chem. Soc. 2018; 140: 3394
