Stereoselective synthesis of alcohols, XXXIV. Towards an understanding of cram/anti‐cram selectivity on addition of crotylboronates to α‐methylbutyraldehyde

Abstract The diastereoselectivity on addition of γ‐substituted allylboronates to α‐methylbutyraldehyde ( 9 ) did not depend on the size of the substitutent in the reagent, but only on its location in the Z or E position. This finding required a reinterpretation of the reasons for the attendant reversal in diastereoselectivity. New hypotheses are presented based on force‐field calculations on model structures for the transition states.