Diastereo- and Enantioselective Synthesis of α,α′-Disubstituted,<i>C</i> ₂-Symmetric Ketones Using the SAMP-/RAMP-Hydrazone Method

Abstract

Starting from simple, symmetric ketones such as, 3-pentanone,1, 3-diphenyl-2-propanone and 2,2-dimethyl-1,3-dioxan-.5-one, α,α′-bisalkylation of the corresponding SAMP-hydrazones (S)-2 and (S)-8 [(S)-1-(alkylideneamino)-2-(methoxymethyl)pyrrolidines and (S)-1-(2,2-dimethyl-1,3-dioxan-5-ylideneamino)-2-(methoxymethyl)pyrrolidines, respectively], followed by oxidative cleavage with ozone affords chiral, C2-symmetric ketones 5 and (S,S)-11 of high diastereo- and enantiomeric purity (de, ee > 98%).