A route to 2-alkenyl-3-(tert-butyldiphenylsilyl)amines and application to the construction of a tricyclic ring system

摘要

N-Tosyl 3,3-dialkyl-2-(tert-butyldiphenylsilylmethyl)azetidines rearrange smoothly into the corresponding 2-alkenyl-3-(tert-butyldiphenylsilyl)amines upon exposure to BF_3·OEt_2 in CH_2Cl _2. The reaction involves sequential ~σC-N bond cleavage, 1,2-migration of the N-tosyl-aminomethyl group, and deprotonation of the resultant tert-carbenium ions. For the instance in which the carbenium ion formed from migration of the N-tosyl-aminomethyl group is highly stable by virtue of being, for example, tertiary as well as benzylic, the migration takes place in sync with σ_(C-N) bond cleavage, which leads to high configurational control at the tert-butyldiphenylsilylmethyl-bearing carbon atom in the product. In contrast to N-tosyl-substituted 3-alkyl-2-(tert- butyldiphenylsilylmethyl)azetidine, the corresponding 3,3-dialkyl derivative rearranges into N-tosyl-2-alkenyl-3-(tert-butyldiphenylsilyl)amine upon exposure to BF_3·OEt_2. The reaction involves sequential σ_(C-N) bond cleavage, 1,2-migration of the N-tosyl-aminomethyl group, and deprotonation of the resultant tert-carbenium ion.