A Flexible Asymmetric Synthesis of anti‐1,2‐Sulfanyl Amines

Abstract

An efficient and flexible asymmetric synthesis of various protected anti-1,2-sulfanyl amines bearing two adjacent stereogenic centres is described. Key steps are the diastereoselective α-alkylation of α-sulfanylated acetaldehyde-SAMPhydrazones with various electrophiles and subsequent nucleophilic 1,2-addition of organocerium reagents to the hydrazone CN double bond. The resulting hydrazines were converted into the title compounds with excellent diastereo-

N,N-Dialkylhydrazones in Organic Synthesis. From Simple N,N-Dimethylhydrazones to Supported Chiral Auxiliaries

“…The products, again, had excellent diastereomeric and enantiomeric excesses (de, ee 96%). 207,208 The unnatural enantiomer of the alkaloid R-conhydrine (256) was synthesized starting from a protected glycol aldehyde SAMP-hydrazone, 252, via R-alkylation and 1,2-addition of alkyllithium reagent 254 (Scheme 49). After borane cleavage of the auxiliary and simultaneous acidic hydrolysis of the acetal, hydrolysis of the tert-butyldimethylsilyl ether and imine formation took place during acidic workup.…”

Asymmetric Synthesis of 3‐Substituted γ‐ and δ‐Sultams

“…13 C NMR (100 MHz, CDCl 3 ): δ = 21.0 (NCH 2 CH 2 ), 23.5, 24.8, 32.7 (11), 328 (7), 283 (21), 281 (11), 215 (8), 214 (12), 203 (34), 197 (9), 130 (16), 129 (100), 117 (17), 106 (7), 105 (47), 84 (24), 83 (37), 77 (8), 70 (9), 67 (9), 55 (11), 54 (7), 46 (7), 45 (16). MS (CI): m/z (%) = 411 (21), 410 (15), 409 (10), 363 (19), 357 (17), 330 (14), 329 (78), 327 (14), 311 (7), 281 (9), 245 (7), 243 (10), 217 (6), 216 (11), 214 (100), 203 (6), 197 (14), 132 (15), 129 (18), 105 (12). C 21 H 34 N 2 O 4 S (410.57) calcd.…”

“…0,128.1,128.5 (CPh) (11), 250 (22), 227 (6), 206 (13), 205 (6), 173 (10), 142 (14), 137 (5), 107 (6), 91 (45), 84 (7), 83 (100), 82 (18), 82 (70), 79 (10), 69 (20), 67 (12). HRMS, C 22 (6), 371 (20), 287 (9), 286 (53), 248 (21), 243 (10), 242 (62), 236 (14), 225 (11), 205 (6), 204 (38), 108 (18), 107 (8), 92 (8), 91 (100), 83 (5), 67 (6). MS (CI): m/z (%) = 454 (6), 354 (9), 264 (17), 221 (10), 173 (8), 108 (22), 107 (14), 95 (8), 92 (9), 91 (74), 84 (5), 83 (70), 82 (69), 81 (100), 80 (13), 79 (31), 69 (18), 67 (61).…”

“…[19] As part of our continuous interest in the asymmetric synthesis of sulfur-containing heterocycles, [20] we already described the diastereo-and enantioselective synthesis of cis-3,4-disubstituted β-sultams. [21] In this paper, we wish to report the efficient enantioselective synthesis of 3-substituted γ-and δ-sultams with the SAMP/RAMP-hydrazone methodology. [22]…”

A Simple and One‐Pot Synthesis of β‐Sultams by Using the Vilsmeier Reagent

“…To synthesize β‐sultams, a number of methods has been developed , most notably (a) cyclization of 2‐aminosulfonyl halides ; (b) cyclization of activated β‐hydroxysulfonamides ; (c) cyclization of α‐(halomethylsulfonamido) ketones, esters, or nitriles ; (d) [2 + 2] cycloaddition reactions of sulfonylamines with particularly electron‐rich olefins ; (e) ring contraction of five‐membered rings of pentafluorophenyl sulfonates ; and (f) [2 + 2] cycloaddition reactions of sulfenes with imines . Among these methods, a widely used method is via the [2 + 2] cyclocondensation of nucleophilic imines and sulfenes.…”