The addition of allyltrimethylsilane to cyclic N-acyliminium ions derived from(S)-(+)-mandelic acid and cyclohexyl-based chiral auxiliaries

• Autor(a) principal: D'Oca,Marcelo G. M.
• Data de Publicação: 2001
• Outros Autores: Pilli,Ronaldo A., Pardini,Vera L., Curi,Denise, Comninos,Francisco C. M.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Journal of the Brazilian Chemical Society (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532001000400011
• topic: (S)-(+)-Mandelic acid; cyclohexyl-based chiral auxiliaries; N-acyliminium ions; pyrrolidine and piperidine derivatives

The TiCl4- promoted addition of allyltrimethylsilane to chiral 5- and 6-membered N-acyliminium ions employing (S)-(+)-mandelic acid, (1R,2S)-trans-2-phenyl-1-cyclohexanol and (1R,2S,5R)-8-phenylmenthol derivatives as chiral auxiliaries occurred with low to moderate diastereoisomeric ratios (1:1-6:1) to afford 2-substituted amides and carbamates in good yields. The best diastereoselection was observed with (1R,2S,5R)-8-phenylmenthol as the chiral auxiliary. The 2-substituted amides and carbamates were converted to the corresponding alkaloids (S)- and (R)-propyl pyrrolidine and coniine with efficient recovery of the chiral auxiliaries.