1,3- versus 1,4-Asymmetric induction in Mukaiyama–Michael additions of optically active ketene acetals to 2-methylcyclopent-2-en-1-one: a remarkable inversion of facial selectivity
TrSbCl6-catalyzed addition of selected optically active ketene acetals to 2-methylcyclopent-2-en-1-one for steroid synthesis is described. Inversion of facial selectivity in 1,3- and 1,4-asymmetricinduction was observed.