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

The TiCl4- promoted addition of allyltrimethylsilane to chiral 5- and 6-mem bered 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 di astereoselection was observed with (1R,2S,5R)-8-phenylmenthol as the chiral auxiliary. The 2-substituted amides and carbamates were converted to the c orresponding alkaloids (S)- and (R)-propyl pyrrolidine and coniine with eff icient recovery of the chiral auxiliaries.