Download PDF
Synthesis 2014; 46(02): 183-188
DOI: 10.1055/s-0033-1340287
paper
© Georg Thieme Verlag Stuttgart · New York

Synthesis of N-Sulfonylamidines by Catalyst-Free Hydroamination of Ynamides and Amines

Yulong Kong
Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, Hangzhou Normal University, Wenyi Road 222, Hangzhou 310012, P. R. of China   Fax: +86(571)28865135   Email: caojian@hznu.edu.cn
,
Lian Yu
Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, Hangzhou Normal University, Wenyi Road 222, Hangzhou 310012, P. R. of China   Fax: +86(571)28865135   Email: caojian@hznu.edu.cn
,
Yuming Cui
Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, Hangzhou Normal University, Wenyi Road 222, Hangzhou 310012, P. R. of China   Fax: +86(571)28865135   Email: caojian@hznu.edu.cn
,
Jian Cao*
Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, Hangzhou Normal University, Wenyi Road 222, Hangzhou 310012, P. R. of China   Fax: +86(571)28865135   Email: caojian@hznu.edu.cn
› Author Affiliations
Further Information

Publication History

Received: 25 September 2013

Accepted after revision: 28 October 2013

Publication Date:
22 November 2013 (online)

 
 PDF Download Permissions and Reprints All articles of this category


Abstract

A novel synthesis of N-sulfonylamidines by catalyst-free hydroamination of N,N-disulfonyl ynamides with amines was developed. Alkyl amines react with N,N-disulfonyl ynamides under mild conditions, whereas aryl amines require higher temperatures. Plausible mechanisms are proposed to explain this reaction.


#

Key words

amines - sulfonamides - aminations

The amidine group is a fundamental motif of various bioactive natural products,[1] and amidines can serve as efficient coordinating ligands and important synthetic intermediates.[2] Although many methods have been established for the synthesis of amidines,[3] more-efficient strategies are still needed. The intermolecular hydroamination of alkynes is an efficient method for preparing substituted amines and imines or ketones.[4] [5] Ynamides, an important subclass of alkynes, have emerged as important synthons in modern organic synthesis,[6–8] and a variety of synthetic targets, including amidines,[8a] have been constructed from ynamides. Recently, Skrydstrup and co-workers developed an elegant synthesis of amidines by gold(I)-catalyzed hydroamination of ynamides with anilines (Scheme [1, a]).[9] However, there are few reports on catalyst-free hydroaminations of ynamides.[10] In the course of a study on hydroamination reactions of ynamides, we found that N,N-disulfonyl ynamides[11] react spontaneously with amines without any catalyst (Scheme [1, b]). Here, we report this novel catalyst-free hydroamination reaction of ynamides that provides ready access to N-sulfonylamidines.

We began our studies by examining the reaction of equimolar ratios of ynamide 1a and benzylamine (2a) in dichloromethane at room temperature. The expected N-sulfonylamidine 3a was obtained in 27% yield in the absence of a catalyst (Table [1], entry 1). Increasing the quantity of amine 2a to four equivalents significantly improved the yield of 3a to 89% (entries 2 and 3). Subsequent screening of solvents showed that dichloromethane gave the best results, and that the use of other common solvents, such as toluene or tetrahydrofuran, did not improve the yield (entries 4–7). We therefore chose the following conditions as optimized conditions for all subsequent reactions: 0.5 mmol of 1 and 2.0 mmol of 2 in dichloromethane at room temperature for four hours with stirring.

Zoom Image
Scheme 1 Synthesis of amidines from ynamides

Table 1 Optimization of the Reaction Conditions

Entrya

Solvent

Ratio 1a/2a

Yield (%) of 3a

1

CH2Cl2

1:1

27

2

CH2Cl2

1:2

55

3

CH2Cl2

1:4

89

4

THF

1:4

44

5

MeCN

1:4

70

6

toluene

1:4

64

7

DMF

1:4

76

a Unless otherwise specified, the reaction was carried out by using 1a (0.5 mmol) and 2a (0.5–2.0 mmol) in solvent (4 mL) at r.t. for 4 h.

By using these optimized conditions, we examined the scope of this catalyst-free hydroamination reaction. The reaction was successful for various N,N-disulfonyl ynamides 1. The R1 group of ynamide 1 can be a phenyl group optionally substituted with either an electron-donating or an electron-withdrawing group (Table [2], entries 1–5). A variety of amines, including primary, secondary, acyclic, and cyclic amines, were all efficiently coupled to give the corresponding N-sulfonylamidines (entries 1 and 5–8). The reaction was also successful when bulky tert-butylamine (2e) was used, albeit with a low yield (entry 9). However, the presence of a free hydroxy group was not tolerated in this reaction (entry 10).

Table 2 Synthesis of N-Sulfonylamidines 3 a

Entry

Ynamide (R1)

Amine

Product

Yield (%)

 1

1a

Ph

2a

BnNH2

3a

89

 2

1b

4-ClC6H4

2a

BnNH2

3b

65

 3

1c

4-PrC6H4

2b

Pr2NH

3c

92

 4

1d

4-MeOC6H4

2b

Pr2NH

3d

88

 5

1e

4-FC6H4

2b

Pr2NH

3e

95

 6

1a

Ph

2c

3f

65

 7

1a

Ph

2d

3g

58

 8

1a

Ph

2b

Pr2NH

3h

66

 9b

1a

Ph

2e

t-BuNH2

3i

22

10

1a

Ph

2f

unidentified mixture

–

a Unless otherwise specified, the reaction was carried out by using 1 (0.5 mmol) and 2 (2.0 mmol) in CH2Cl2 (4 mL) at r.t. for 4 h.

b The reaction time was 24 h.

Aryl amines did not undergo the hydroamination reaction under these mild conditions. However, under modified conditions (1,4-dioxane solvent, 100 °C), anilines 2g–i also reacted smoothly with ynamides 1a to give the corresponding amidines 3j–l (Scheme [2]).

Zoom Image
Scheme 2 Synthesis of amidines from aryl amines

Note, however, that N-monosulfonyl ynamides 1f and 1g did not undergo this hydroamination reaction, even at 100 °C in 1,4-dioxane for 24 hours; in these cases, the starting material was recovered (Scheme [3]).

In every case where reaction did occur, the sulfonamide PhSO2NR2R3 was obtained as a byproduct; we therefore suggest the mechanism shown in Scheme [4]. Ynamide 1 and amine 2 undergoes a spontaneous hydroamination reaction to form intermediate A, which is desulfonylated by a second molecule of amine 2 to give the N-sulfonylamidine product 3 (route a). Another elimination–addition mechanism via the intermediate ketenimine B (route b) cannot be ruled out. Neither A nor B was detected.

Zoom Image
Scheme 3 Attempted reaction with N-monosulfonyl ynamides
Zoom Image
Scheme 4 Proposed reaction mechanisms

In conclusion, we have described a novel synthesis of N-sulfonylamidines by a catalyst-free hydroamination of ynamides with amines. Alkyl amines react with N,N-disulfonyl ynamides under very mild conditions, whereas aryl amines require higher temperatures. Plausible mechanisms are proposed to explain this reaction, and further investigations on the mechanistic details and applications of this reaction are ongoing in our laboratory.

All commercially available chemicals and reagents were used without any further purification. Flash column chromatography was carried out by using 300–400 mesh silica gel. 1H and 13C NMR spectra were recorded at 400 and 100 MHz, respectively, on a Bruker Avance 400 spectrometer with TMS as the internal standard and CDCl3 as solvent. High-resolution mass spectra were recorded on a Waters Micromass GCT mass spectrometer operating in the ESI-TOF mode. IR spectra were recorded on a Bruker Vector 22 spectrophotometer.

Ynamides were prepared by Muñiz’s method.[11] The properties of previously unreported ynamides are listed below.


#

N-[(4-Chlorophenyl)ethynyl]-N-(phenylsulfonyl)benzenesulfonamide (1b)

Pale-yellow solid; yield: 526.9 mg (61%); mp 139–141 °C (CH2Cl2).

IR (KBr): 3065, 2237, 1448, 1371, 1170, 1083, 823 cm–1.

1H NMR (400 MHz, CDCl3): δ = 8.04 (d, J = 8.0 Hz, 4 H), 7.69–7.74 (m, 2 H), 7.56–7.60 (m, 4 H), 7.29–7.37 (m, 4 H).

13C NMR (100 MHz, CDCl3): δ = 137.7, 135.1, 135.0, 133.3, 129.4, 128.8, 128.6, 120.1, 77.0, 76.3.

HRMS (ESI): m/z [M + Na]+ calcd for C20H14ClNNaO4S2: 453.9945; found: 453.9946.


#

N-(Phenylsulfonyl)-N-[(4-propylphenyl)ethynyl]benzenesulfonamide (1c)

Brown oil; yield: 606.5 mg (69%).

IR (neat): 2927, 2239, 1393, 1173, 1083, 841, 681 cm–1.

1H NMR (400 MHz, CDCl3): δ = 8.05 (d, J = 8.0 Hz, 4 H), 7.71–7.73 (m, 2 H), 7.57–7.59 (m, 4 H), 7. 36 (d, J = 8.0 Hz, 2 H), 7.15 (d, J = 8.0 Hz, 2 H), 2.59 (t, J = 8.0 Hz, 2 H), 1.60–1.67 (m, 2 H), 0.94 (t, J = 8.0 Hz, 3 H).

13C NMR (100 MHz, CDCl3): δ = 144.2, 137.9, 134.8, 132.3, 129.2, 128.61, 128.58, 118.7, 78.2, 74.7, 38.0, 24.3, 13.8.

HRMS (ESI): m/z [M + Na]+ calcd for C23H21NNaO4S2: 462.0804; found: 462.0810.


#

N-[(4-Methoxyphenyl)ethynyl]-N-(phenylsulfonyl)benzenesulfonamide (1d)

Pale-yellow solid; yield: 607.0 mg (71%); mp 119–121 °C (CH2Cl2).

IR (KBr): 2935, 1604, 1569, 1392, 1264, 1173, 732 cm–1.

1H NMR (400 MHz, CDCl3): δ = 8.04 (d, J = 8.0 Hz, 4 H), 7.71–7.72 (m, 2 H), 7.57–7.59 (m, 4 H), 7.38 (d, J = 8.0 Hz, 2 H), 6.85 (d, J = 8.0 Hz, 2 H), 3.82 (s, 3 H).

13C NMR (100 MHz, CDCl3): δ = 160.4, 137.9, 134.7, 134.3, 129.2, 128.6, 114.0, 113.5, 78.1, 74.1, 55.4.

HRMS (ESI): m/z [M + Na]+ calcd for C21H17NNaO5S2: 450.0440; found: 450.0438.


#

N-[(4-Fluorophenyl)ethynyl]-N-(phenylsulfonyl)benzenesulfonamide (1e)

Light-gray solid; yield: 481.9 mg (58%); mp 126–128 °C (CH2Cl2).

IR (KBr): 3066, 2241, 1449, 1392, 1175, 1083, 834 cm–1.

1H NMR (400 MHz, CDCl3): δ = 8.05–8.06 (m, 4 H), 7.71–7.75 (m, 2 H), 7.58–7.60 (m, 4 H), 7.41–7.43 (m, 2 H), 7.01–7.04 (m, 2 H).

13C NMR (100 MHz, CDCl3): δ = 164.2, 161.8, 137.9, 134.9, 134.4, 134.3, 129.3, 128.6, 117.7, 115.9, 115.7, 75.0.

HRMS (ESI): m/z [M + Na]+ calcd for C20H14FNNaO4S2: 438.0240; found: 438.0245.


#

N-Benzyl-2-phenyl-N′-(phenylsulfonyl)ethanimidamide (3a); Typical Procedure

BuNH2 (2a; 2.0 mmol, 214.4 mg, 4.0 equiv) was added to a solution of disulfonamide 1a (0.5 mmol, 198.8 mg) in CH2Cl2 (4 mL), and the mixture was stirred at r.t. for 4 h until 1a was consumed [TLC, hexane–EtOAc (6:1)]. The mixture was then concentrated and the residue was purified by flash chromatography [silica gel, hexane–EtOAc (6:1 to 4:1)] to give a pale-tan solid; yield: 162.4 mg (89%); mp 99–101 °C (CH2Cl2).

IR (KBr): 2922, 1552, 1265, 1140, 1090, 731, 688 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.87 (d, J = 8.4 Hz, 2 H), 7.40–7.51 (m, 3 H), 7.18–7.33 (m, 8 H), 7.04–7.06 (m, 2 H), 5.96 (br s, 1 H), 4.40 (d, J = 5.6 Hz, 2 H), 4.29 (s, 2 H).

13C NMR (100 MHz, CDCl3): δ = 166.7, 143.4, 136.5, 133.1, 131.7, 130.0, 129.4, 128.7, 128.6, 128.1, 127.7, 127.6, 126.3, 45.9, 39.7.

HRMS (ESI): m/z [M + Na]+ calcd for C21H20N2NaO2S: 387.1138; found: 387.1152.


#

N-Benzyl-2-(4-chlorophenyl)-N′-(phenylsulfonyl)ethanimid­amide (3b)

Light-gray solid; yield: 130.4 mg (65%); mp 126–128 °C (CH2Cl2).

IR (KBr): 2924, 1551, 1270, 1138, 1089, 733 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.79 (d, J = 8.0 Hz, 2 H), 7.38–7.49 (m, 3 H), 7.22–7.25 (m, 5 H), 7.06–7.13 (m, 4 H), 6.12 (br s, 1 H), 4.40 (d, J = 5.2 Hz, 2 H), 4.21 (s, 2 H).

13C NMR (100 MHz, CDCl3): δ = 165.9, 143.2, 136.4, 133.9, 131.7, 131.1, 129.4, 128.7, 128.6, 127.8, 127.7, 126.2, 46.0, 38.9.

HRMS (ESI): m/z [M + Na]+ calcd for C21H19ClN2NaO2S: 421.0748; found: 421.0758.


#

N′-(Phenylsulfonyl)-N,N-dipropyl-2-(4-propylphenyl)ethan­imidamide (3c)

Brown oil; yield: 185.2 mg (92%).

IR (neat): 2961, 1541, 1468, 1271, 1140, 1086, 727 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.84 (d, J = 8.0 Hz, 2 H), 7.32–7.40 (m, 3 H), 7.01 (m, 4 H), 4.31 (s, 2 H), 3.34 (t, J = 8.0 Hz, 2 H), 3.05 (t, J = 8.0 Hz, 2 H), 2.49 (t, J = 8.0 Hz, 2 H), 1.53–1.58 (m, 4 H), 1.26–1.30 (m, 2 H), 0.87 (t, J = 8.0 Hz, 3 H), 0.79 (t, J = 8.0 Hz, 3 H), 0.68 (t, J = 8.0 Hz, 3 H).

13C NMR (100 MHz, CDCl3): δ = 165.2, 144.3, 141.1, 131.5, 131.2, 128.9, 128.3, 127.8, 126.1, 50.8, 50.6, 37.5, 36.4, 24.5, 21.6, 20.0, 13.7, 11.4, 11.0.

HRMS (ESI): m/z [M + Na]+ calcd for C23H32N2NaO2S: 423.2077; found: 423.2091.


#

2-(4-Methoxyphenyl)-N′-(phenylsulfonyl)-N,N-dipropylethan­imidamide (3d)

Brown oil; yield: 170.6 mg (88%).

IR (neat): 2963, 1541, 1246, 1139, 1086, 833 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.84–7.86 (m, 2 H), 7.33–7.41 (m, 3 H), 7.03 (d, J = 8.0 Hz, 2 H), 6.75 (d, J = 8.0 Hz, 2 H), 4.27 (s, 2 H), 3.70 (s, 3 H), 3.33 (t, J = 8.0 Hz, 2 H), 3.06 (t, J = 8.0 Hz, 2 H), 1.50–1.57 (m, 2 H), 1.28–1.34 (m, 2 H), 0.78 (t, J = 8.0 Hz, 3 H), 0.70 (t, J = 8.0 Hz, 3 H).

13C NMR (100 MHz, CDCl3): δ = 165.3, 158.4, 144.2, 131.2, 129.0, 128.4, 126.3, 126.0, 114.2, 55.2, 50.8, 50.6, 36.0, 21.6, 20.0, 11.4, 11.1.

HRMS (ESI): m/z [M + Na]+ calcd for C21H28N2NaO3S: 411.1713; found: 411.1730.


#

2-(4-Fluorophenyl)-N′-(phenylsulfonyl)-N,N-dipropylethan­imidamide (3e)

Brown oil; yield: 178.4 mg (95%).

IR (neat): 2965, 1542, 1270, 1139, 1085, 834 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.82 (d, J = 6.4 Hz, 2 H), 7.34–7.37 (m, 3 H), 7.05–7.15 (m, 2 H), 6.86–6.90 (m, 2 H), 4.30 (s, 2 H), 3.32 (t, J = 5.6 Hz, 2 H), 3.03 (t, J = 5.6 Hz, 2 H), 1.51–1.53 (m, 2 H), 1.28–1.30 (m, 2 H), 0.76 (t, J = 8.0 Hz, 3 H), 0.68 (t, J = 8.0 Hz, 3 H).

13C NMR (100 MHz, CDCl3): δ = 164.7, 162.3, 160.4, 144.1, 131.3, 130.20, 130.17, 129.64, 129.56, 128.4, 126.0, 115.8, 115.6, 50.8, 50.6, 36.0, 21.6, 20.0, 11.3, 11.0.

HRMS (ESI): m/z [M + Na]+ calcd for C20H25FN2NaO2S: 399.1513; found: 399.1522.


#

N-(2-Phenyl-1-pyrrolidin-1-ylethylidene)benzenesulfonamide (3f)

Pale-tan solid; yield: 106.6 mg (65%); mp 119–121 °C (CH2Cl2).

IR (KBr): 2977, 1539, 1195, 1136, 1086, 815, 727cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.91 (d, J = 8.0 Hz, 2 H), 7.36–7.41 (m, 3 H), 7.13–7.24 (m, 5 H), 4.33 (s, 2 H), 3.54–3.60 (m, 2 H), 3.17–3.26 (m, 2 H), 1.75–1.83 (m, 4 H).

13C NMR (100 MHz, CDCl3): δ = 164.1, 144.2, 133.6, 131.3, 128.8, 128.5, 128.2, 126.8, 126.3, 49.0, 47.7, 38.3, 25.7, 24.0.

HRMS (ESI): m/z [M + Na]+ calcd for C18H20N2NaO2S: 351.1138; found: 351.1144.


#

N-(1-Morpholino-2-phenylethylidene)benzenesulfonamide (3g)

Light-gray solid; yield: 99.8 mg (58%); mp 121–123 °C (CH2Cl2).

IR (KBr): 2856, 1536, 1443, 1268, 1140, 1086, 720 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.92–7.93 (m, 2 H), 7.42–7.49 (m, 3 H), 7.21–7.30 (m, 3 H), 7.16 (d, J = 8.0 Hz, 2 H), 4.45 (s, 2 H), 3.79–3.80 (m, 2 H), 3.62–3.63 (m, 2 H), 3.32–3.34 (m, 4 H).

13C NMR (100 MHz, CDCl3): δ = 165.1, 143.6, 134.0, 131.6, 129.1, 128.6, 127.9, 127.1, 126.4, 66.2, 66.1, 46.9, 45.0, 36.9.

HRMS (ESI): m/z [M + Na]+ calcd for C18H20N2NaO3S: 367.1087; found: 367.1086.


#

2-Phenyl-N′-(phenylsulfonyl)-N,N-dipropylethanimidamide (3h)

Pale-yellow solid; yield: 118.1 mg (66%); mp 110–112 °C (CH2Cl2).

IR (KBr): 2965, 1543, 1432, 1273, 1141, 1087, 727 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.86–7.88 (m, 2 H), 7.34–7.43 (m, 3 H), 7.17–7.25 (m, 3 H), 7.12 (d, J = 8.0 Hz, 2 H), 4.37 (s, 2 H), 3.37 (t, J = 7.6 Hz, 2 H), 3.06 (t, J = 7.6 Hz, 2 H), 1.55–1.59 (m, 2 H), 1.31–1.35 (m, 2 H), 0.81 (t, J = 7.6 Hz, 3 H), 0.71 (t, J = 7.6 Hz, 3 H).

13C NMR (100 MHz, CDCl3): δ = 164.9, 144.2, 134.4, 131.3, 128.9, 128.4, 127.9, 126.9, 126.1, 50.8, 50.6, 36.8, 21.6, 20.0, 11.4, 11.0.

HRMS (ESI): m/z [M + Na]+ calcd for C20H26N2NaO2S: 381.1607; found: 381.1611.


#

N-(tert-Butyl)-2-phenyl-N′-(phenylsulfonyl)ethanimidamide (3i)

Light-gray solid; yield: 36.3 mg (22%); mp 161–163 °C (CH2Cl2).

IR (KBr): 3309, 2917, 1546, 1273, 1138, 1088, 683 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.96–7.98 (m, 2 H), 7.45–7.52 (m, 3 H), 7.33–7.37 (m, 3 H), 7.20–7.22 (m, 2 H), 5.09 (br s, 1 H), 4.27 (s, 2 H), 1.22 (s, 9 H).

13C NMR (100 MHz, CDCl3): δ = 165.1, 143.8, 133.5, 131.5, 130.0, 129.4, 128.6, 128.1, 126.1, 53.4, 40.6, 28.0.

HRMS (ESI): m/z [M + Na]+ calcd for C18H22N2NaO2S: 353.1294; found: 353.1290.


#

N-Methyl-N,2-diphenyl-N′-(phenylsulfonyl)ethanimidamide (3j); Typical Procedure

PhNHMe (2g; 2.0 mmol, 214.4 mg, 4.0 equiv) was added to a solution of disulfonamide 1a (0.5 mmol, 198.8 mg) in 1,4-dioxane (4 mL) containing Et3N (0.5 mL), and the mixture was stirred at 100 °C for 12 h until 1a was consumed [TLC, hexane–EtOAc (6:1)]. The mixture was then concentrated, and the residue was purified by flash chromatography [silica gel, hexane–EtOAc (6:1 to 4:1)] to give a brown oil; yield: 126.5 mg (69%).

IR (neat): 3062, 1530, 1277, 1143, 1088, 690 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.99 (d, J = 8.0 Hz, 2 H), 7.45–7.48 (m, 3 H), 7.19–7.26 (m, 3 H), 7.06 (d, J = 4.0 Hz, 3 H), 6.77–6.79 (m, 4 H), 4.24 (s, 2 H), 3.32 (s, 3 H).

13C NMR (100 MHz, CDCl3): δ = 166.6, 143.9, 142.5, 134.6, 131.6, 129.6, 128.6, 128.5, 128.4, 128.3, 127.2, 126.5, 126.4, 41.2, 37.8.

HRMS (ESI): m/z [M + Na]+ calcd for C21H20N2NaO2S: 387.1138; found: 387.1138.


#

N-[1-(3,4-Dihydroquinolin-1(2H)-yl)-2-phenylethylidene]benzenesulfonamide (3k)

Pale-yellow solid; yield: 104.9 mg (54%); mp 154–156 °C (CH2Cl2).

IR (KBr): 2951, 1522, 1492, 1278, 1142, 1085, 744 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.99 (d, J = 8.0 Hz, 2 H), 7.45–7.51 (m, 3 H), 7.10–7.18 (m, 6 H), 6.90–6.96 (m, 3 H), 4.59 (s, 2 H), 3.80–3.82 (m, 2 H), 2.21–2.23 (m, 2 H), 1.76–1.81 (m, 2 H).

13C NMR (100 MHz, CDCl3): δ = 166.4, 143.7, 138.4, 134.4, 131.7, 128.6, 128.4, 128.3, 127.0, 126.6, 126.4, 126.3, 124.9, 46.3, 37.6, 25.7, 23.5.

HRMS (ESI): m/z [M + Na]+ calcd for C23H22N2NaO2S: 413.1294; found: 413.1299.


#

N,2-Diphenyl-N′-(phenylsulfonyl)ethanimidamide (3l)

Pale-tan solid; yield: 152.9 mg (87%); mp 160–162 °C (CH2Cl2).

IR (KBr): 3302, 3148, 1537, 1444, 1274, 1138, 1084 cm–1.

1H NMR (400 MHz, CDCl3): δ = 9.97 (br s, 0.38 H), 7.94–7.99 (m, 2 H), 6.86–7.54 (m, 14 H), 4.50 (s, 1.21 H), 3.58 (s, 0.8 H).

13C NMR (100 MHz, CDCl3): δ = 166.5, 163.8, 143.2, 142.0, 136.7, 136.1, 134.4, 132.9, 132.4, 131.9, 130.2, 129.6, 129.5, 128.8, 128.7, 128.4, 127.1, 126.4, 125.8, 121.6, 40.6, 40.2.

HRMS (ESI): m/z [M + Na]+ calcd for C20H18N2NaO2S: 373.0981; found: 373.0989.


#
#

Acknowledgment

We are grateful to the National Natural Science Foundation of China (Project No. 21102029) for financial support.

Supporting Information

    for this article is available online at http://www.thieme-connect.com.accesdistant.sorbonne-universite.fr/ejournals/toc/synthesis.
  • Supporting Information


   Permissions and Reprints All articles of this category
Zoom Image
Scheme 1 Synthesis of amidines from ynamides
Zoom Image
Scheme 2 Synthesis of amidines from aryl amines
Zoom Image
Scheme 3 Attempted reaction with N-monosulfonyl ynamides
Zoom Image
Scheme 4 Proposed reaction mechanisms