Synergistic effect of multichiral centres. Chelation control vs. acetal template in 1,3-asymmetric induction
Abstract
The allylation of the β-siloxyacetal (5), (S–R,R isomer) in the presence of TiCl4 gave the chelation adduct (6) with very high selectivity, while the (R–R,R) isomer (8) also produced the chelation adduct (9), indicating that the 1,3-asymmetric induction is dictated by chelation rather than the acetal template.