Highly Stereoselective Ylide Aziridination of N-Sulfonylimines with Sulfonium Propargylides:  A Simple Way To Synthesize Scalemic Acetylenylaziridines

Abstract

Under phase-transfer or low-temperature conditions, the ylide generated from diphenylsulfonium salt 2 readily reacts with N-sulfonylimines 1 to give acetylenylaziridines in excellent yields, but low to moderate cis/trans selectivity. When using n-BuLi as the base to generate the ylide at low termperature, product 3 with an intact silyl protecting group is obtained. t-BuOK, however, leads to desilylation product 4. With Cs 2 CO 3 as the base, dimethylsulfonium salts 6, 21, and 22 show much better cis/trans selectivity (>98:2) than diphenylsulfonium salt 2. The asymmetric version of the above aziridination reaction using camphor-derived sulfonium salts 12-14 and 20 gives chiral aziridines with ee values up to 85%. Both (2R,3S)-(-)-3 and (2S,3R)-(+)-3 can be prepared from 12/20 or 13/14, respectively. Ylides produced from telluronium salt 7 failed to react with imine 1a at room temperature, but the reaction succeeded at low temperature. Arsonium ylides from 8 cannot react with N-sulfonylimines under both sets of conditions.

Recent Developments on Catalytic Applications of Nano-Crystalline Magnesium Oxide

“…Surprisingly, these results are in contrast to many reports in which aziridine, aziridinyl carboxamide or b-amino alkenes are the final products [98][99][100]. In order to understand the relationship between structure and reactivity (please refer Fig.…”

An efficient and selective synthesis of 2,5-substituted pyrroles by gold-catalysed ring expansion of alkynyl aziridines

“…All the alkynyl aziridines employed in our study were prepared according to the method of Dai through a convergent coupling of an imine with a propargylic sulfonium ylide (Scheme 2) [11]. In most cases a mixture of diastereomers were obtained, with the cis-diastereomer predominating, and were used as such in the subsequent reactions [12].…”

“…For analytical data relating to compounds in Table 1 Entries 1e6 see Ref [3]. Data for the following compounds are in accordance to literature values (Table 1 Entries , 10, 11, 14) [6a]; 4a [23], 4b [6a], 5b/c [6a], 4c [11], dimethyl (3-(trimethylsilyl)prop-2-yn-1-yl)sulfonium bromide and dimethyl(3-phenylprop-2-yn-1-yl) sulfonium bromide correspond to the literature [11]. …”

“…and Bruker DRX500 ( 1 H ¼ 500 MHz, 13 Sulfonium salts and alkynyl aziridines were prepared according to the literature method [11]. For analytical data relating to compounds in Table 1 Entries 1e6 see Ref [3].…”

Isotopic labelling studies for a gold-catalysed skeletal rearrangement of alkynyl aziridines

“…Oxidation to the aldehyde followed by condensation with tosylamide afforded the deuterated imine 6 . Aziridination using the sulfonium ylide generated in situ from 7 proceeded smoothly to afford the desired cycloisomerisation precursor 4 [ 28 ]. The aziridines were formed as a mixture of diastereomers, with the cis diastereomer predominating, and were employed as such in the cycloisomerisation reactions.…”