STEREOSELECTIVE INTRAMOLEKULAR ALLYLSILANE ADDITIONS TO CHIRAL ALDEHYDES

Article abstract of DOI:10.1016/S0040-4020(01)86643-6

The sense of 1,3-asymmetric induction in the TiCl₄ mediated allylsilane addition of O-(allyl)silyl protected aldehydes 14 is opposite (>90percent syn selectivity) to that of the previously reported reaction of the O-benzyl protected analogs 7 with allyltrimethylsilane (>90percent anti selectivity).Crossover experiments show that strict intramolecularity pertains, suggesting an intramolecular allylsilane addition as depicted in 15.Surprisingly, the switch from TiCl₄ to SnCl₄ results in the reversal of diastereofacial selectivity and in an intramolecular allyl transfer mechanism. α-Chiral β-silyloxy aldehydes of the type 35 are not very well suited for stereoselective allylations.