A Metal-Free Protocol for Aminofunctionalization of Olefins Using TsNBr₂

Abstract

N,N-Dibromo-p-toluene sulfonamide (TsNBr2) has been found to be an effective reagent for various aminofunctionalization reactions. This reagent behaves both as an electrophilic bromine source as well as amine to react with olefins under different conditions to yield aminoether, imidazoline, diamine and amino bromine. The reaction proceeds rapidly under mild conditions with high regioselectivity. Olefins react with TsNBr2 in moist THF to form δ-amino ether at room temperature. Treatment of TsNBr2 with olefin in MeCN at room temperature produced imidazoline in high yield. Further modification of the reaction condition resulted in the development of a one-step procedure for the synthesis of N-acetyl,N'-tosyl diamine derivatives directly from olefin. When the olefin was treated with 2.4 mol equiv of TsNBr2 in the presence of K2CO3, N,N'-ditosyl diamine derivative was obtained in moderate yield. Instantaneous formation of aminobromine was observed when an olefin was treated with the reagent in dry CH2Cl2 at room temperature.

Recent Advances in the Synthesis of Imidazolines (2009–2020)

“…Based on the experimental results, a reasonable mechanism was illustrated in the report (Scheme 97 In 2016, Phukan and co-workers developed a metal-free aminofunctionalization protocol to synthesize 2-imidazoline (350) (Scheme 98). [95] The reaction utilized treatment of N,N-dibromo-p-toluene sulfonamide (TsNBr 2 ) (348) with the olefin (347) and acetonitrile (349) at room temperature to synthesize imidazoline analogs (350). The reaction scope was investigated by using different alkyl-and aryl-substituted alkenes (347) with TsNBr 2 in acetonitrile, and the imidazolines were isolated in good yields (73-81%).…”

“…In 2016, Phukan and co‐workers developed a metal‐free aminofunctionalization protocol to synthesize 2‐imidazoline ( 350 ) (Scheme ) . The reaction utilized treatment of N , N ‐dibromo‐ p ‐toluene sulfonamide (TsNBr 2 ) ( 348 ) with the olefin ( 347 ) and acetonitrile ( 349 ) at room temperature to synthesize imidazoline analogs ( 350 ).…”

Photoredox-Induced Functionalization of Alkenes for the Synthesis of Substituted Imidazolines and Oxazolidines

“…5, 66.6, 126.3, 127.1, 127.7, 128.7, 129.5, 133.7, 138.1, 141.4, 156.2; IR (KBr, cm −1 ): 3278,3064,2927,1647,1543,1448,1360,1243,1169,1116,1092,1024,970,757,730,690,600,570 4-(4-Fluorophenyl)-2-methyl-1-tosyl-4,5-dihydro-1H-imidazole (3c). 17 Colorless oil; 58.5 mg, 88% yield; 1 H NMR (400 MHz, CDCl 3 ) δ (ppm) = 2.39 (d, J = 1.4 Hz, 3H), 2.46 (s, 3H), 3.58 (dd, J = 9.8, 7.8 Hz, 1H), 4.16 (t, J = 10.1 Hz, 1H), 4.97 (t, J = 8.7 Hz, 1H), 6.94 (t, J = 8.7 Hz, 2H), 7.00−7.03 (m, 2H), 7.35 (d, J = 8.1 Hz, 2H), 7.74 (d, J = 8.3 Hz, 2H); 13 C NMR (100 MHz, CDCl 3 ) δ (ppm) = 16.8, 21.5, 55. 5,65.9,115.5 (d,J = 21.3 Hz), 127.2, 128.0 (d, J = 8.1 Hz), 130.1, 137.4 (d, J = 3.1 Hz), 144.8,156.6,162.1 (d,J = 244.5 Hz); IR (KBr, cm −1 ): 3283,3060,2927,1646,1599,1511,1360,1225,1166,1114,1092,1016,971,836,710,657,593,546 4-(4-Chlorophenyl)-2-methyl-1-tosyl-4,5-dihydro-1H-imidazole (3d).…”

“…5,65.9,115.5 (d,J = 21.3 Hz), 127.2, 128.0 (d, J = 8.1 Hz), 130.1, 137.4 (d, J = 3.1 Hz), 144.8,156.6,162.1 (d,J = 244.5 Hz); IR (KBr, cm −1 ): 3283,3060,2927,1646,1599,1511,1360,1225,1166,1114,1092,1016,971,836,710,657,593,546 4-(4-Chlorophenyl)-2-methyl-1-tosyl-4,5-dihydro-1H-imidazole (3d). 17 Colorless oil; 66.0 mg, 95% yield; 1 H NMR (400 MHz, CDCl 3 ) δ (ppm) = 2.39 (d, J = 1.4 Hz, 3H), 2.40 (s, 3H), 3.57 (dd, J = 9.8, 7.8 Hz, 1H), 4.17 (t, J = 10.1 Hz, 1H), 4.97 (t, J = 8.9 Hz, 1H), 6.98 (d, J = 8.4 Hz, 2H), 7.23 (d, J = 8.4 Hz, 2H), 7.35 (d, J = 8.1 Hz, 2H), 7.73 (d, J = 8.2 Hz, 2H); 13 C NMR (100 MHz, CDCl 3 ) δ (ppm) = 16.8, 21.6, 55.4, 65.8, 127.2, 127.7, 128.8, 130.1, 133.4, 135.0, 140.1, 144.9, 156.9; IR (KBr, cm −1 ): 3276,3059,2926,1647,1598,1493,1360,1166,1115,1091,1015,971,816,736,656,593,547 4-(4-Bromophenyl)-2-methyl-1-tosyl-4,5-dihydro-1H-imidazole (3e). 17 Colorless oil; 55.7 mg, 71% yield; 1 H NMR (400 MHz, CDCl 3 ) δ (ppm) = 2.39 (s, 3H), 2.45 (s, 3H), 3.56 (dd, J = 9.8, 7.9 Hz, 1H), 4.16 (t, J = 10.1 Hz, 1H), 4.95 (t, J = 8.7 Hz, 1H), 6.92 (d, J = 8.3 Hz, 2H), 7.32−7.38 (m, 4H), 7.72 (d, J = 8.2 Hz, 2H); 13 C NMR (100 MHz, CDCl 3 ) δ (ppm)...…”

“…17 Colorless oil; 66.0 mg, 95% yield; 1 H NMR (400 MHz, CDCl 3 ) δ (ppm) = 2.39 (d, J = 1.4 Hz, 3H), 2.40 (s, 3H), 3.57 (dd, J = 9.8, 7.8 Hz, 1H), 4.17 (t, J = 10.1 Hz, 1H), 4.97 (t, J = 8.9 Hz, 1H), 6.98 (d, J = 8.4 Hz, 2H), 7.23 (d, J = 8.4 Hz, 2H), 7.35 (d, J = 8.1 Hz, 2H), 7.73 (d, J = 8.2 Hz, 2H); 13 C NMR (100 MHz, CDCl 3 ) δ (ppm) = 16.8, 21.6, 55.4, 65.8, 127.2, 127.7, 128.8, 130.1, 133.4, 135.0, 140.1, 144.9, 156.9; IR (KBr, cm −1 ): 3276,3059,2926,1647,1598,1493,1360,1166,1115,1091,1015,971,816,736,656,593,547 4-(4-Bromophenyl)-2-methyl-1-tosyl-4,5-dihydro-1H-imidazole (3e). 17 Colorless oil; 55.7 mg, 71% yield; 1 H NMR (400 MHz, CDCl 3 ) δ (ppm) = 2.39 (s, 3H), 2.45 (s, 3H), 3.56 (dd, J = 9.8, 7.9 Hz, 1H), 4.16 (t, J = 10.1 Hz, 1H), 4.95 (t, J = 8.7 Hz, 1H), 6.92 (d, J = 8.3 Hz, 2H), 7.32−7.38 (m, 4H), 7.72 (d, J = 8.2 Hz, 2H); 13 C NMR (100 MHz, CDCl 3 ) δ (ppm) = 16.7, 21. 5, 55.3, 65.8, 121.4, 127.1, 128.0, 130.1, 131.6, 135.0, 140.6, 144.8, 156.8; IR (KBr, cm −1 ): 3276,3055,2924,1646,1597,1488,1359,1242,1166,1116,1091,1011,971,816,709,663,593,547 4-(3-Chlorophenyl)-2-methyl-1-tosyl-4,5-dihydro-1H-imidazole (3f).…”