Aminosulfonium salts

Two methods are described for the preparation of chiral amino-sulfonium salts. The first is based on the alkylation of nitrogen in chiral sulfimides. In this way the optically active aminosulfonium salt 123 was obtained from sulfimide 124, as shown in eq. [63] (164). 

The second approach to chiral aminosulfonium salts consists of the conversion of chiral sulfoxides into aminosulfonium salts by means of MA -diethylaminosulfinyl tetrafluoroborate (165). The reaction occurs with predominant retention of configuration at sulfur with dialkyl and alkyl aryl sulfoxides. However, its stereospecificity is strongly dependent on the nature of substituents in the starting sulfoxide. In the case of diaryl sulfoxides this method failed to give chiral aminodiarylsulfonium salts. 

The studies of Darwish et al. (166,253) have shown that the sulfonium ylide 127 and the aminosulfonium salts 216 also undergo racemization at 50 to 90 C by pyramidal inversion. 

Aminosulfonium salts are obtained by the reaction of (1) with primary or secondary amines (40-85 % yield). 

Cis- and trons-aminals 385 and 230 which could easily be obtained from en-aminosulfonium salts (255) (Scheme 7) or chloroenamines (228) (see equation 54) were usedior the preparation of further sterically pure aminocyclopropanes (equations 93 and 94). 

In some cases primary products of the reaction of dialkyl and diamino sulfides with CBT were traced in solutions. These ionic or covalent derivatives of tetracoordinate sulfur are convenient intermediates for the preparation of alkoxy- and aminosulfonium salts and sulfoxides [72TL501 ... 

S-Alkoxy-S-aminosulfonium salts S-Aminosulfoxonium salts Sulfinic acid amides Sulfoximines... 

Alkylideneamino)sulfonium salts S-Alkylthiolactims 1-Alkylthio-l-pyridinium salts S-Aminosulfonium ylids... 

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