ASYMMETRIC INDUCTION IN DARZENS CONDENSATION BY MEANS OF (-)-8-PHENYLMENTHYL AND (-)-MENTHYL AUXILIARIES

Asymmetric Darzens condensation of benzaldehyde and various ketones ha s been investigated, The condensation of acetophenone, propiophenone a nd symmetric ketones with (-)-8-phenylmenthyl halogenoacetates 3a,b af forded the corresponding glycidic esters cis-12, cis-13 and 15-19 in 7 7-96% de, respectively, as the major products, Aza-Darzens condensatio n between N-benzylideneaniline and 3a occurred to give the trans-aziri dine 21 as the major isomer in >85% de, The stereochemistry of the maj or diastereoisomers of cis-12 and 18 was confirmed by their conversion into the known optically active diols 22 and 24, The configuration of the major product of cis-12 was determined to be 2R,3R and that of 18 to be 2R, The geometric and disastereofacial selectivities were under standable in terms of the open-chain or non-chelated antiperiplanar tr ansition state model in the initial aldol-type reaction.