Diastereoselective additions of organolithiums to new chiral hydrazones

Abstract

The new chiral auxiliaries for the stereoselective reactions were synthesized from (S)-indoline-2-carboxylic acid. These derivatives provided high stereoselectivities in various asymmetric reactions. The reaction of organolithiums with chiral hydrazones derived from (S)-indoline-2-carboxylic acid afforded chiral hydrazines with high diastereoselectivity (up to >99% de). Diastereomeric excess was determined by HPLC (Chiral OD Column). The absolute configuration was determined by the optical rotation of the corresponding N-salicylidene derivative of TBDMS-protected phenylglycinol and by comparison of its rotation with one of the optically pure authentic sample. Diastereoselective addition of PhLi to chiral trifluoropyruvic aldehyde hydrazones gave the corresponding tertiary alcohols containing CF3 in good optical purity (up to 72% de). If the optical yield can be enhanced it may be used for the enantioselective synthesis of Mosher reagent ((S) or (R)-α-Methoxy-α-trifluoromethylphenylacetic acid).