Substituent effect on the asymmetric induction with (1R,2S,5R)-and (1S,2R,5S)-menthol auxiliaries

Abstract

Substituted benzaldehydes reacts in cis-diastereoselective manner with menthyl haloacetates in the presence of phase transfer catalyst and a base in THF at room temperature to, give the corresponding 3-aryloxirane-2-carboxylates (2/3a-h) in moderate to high yields. The magnitude of asymmetric induction in the latter reaction was quantified by a Hammett type equation log(2/3)(X) = p sigma(1) + log(2/3)(X=H). The stereochemistry of compounds 2 and 3 was elucidated by correlation with (4S,5R)-2,4-dipheny1-4,5-dihydrooxazole-5-carboxylic acid (+)-8 as well as its enantiomer (-)-8.