Enantiopure Chiral (2,4,6-Triisopropylbenzoyl)oxy-[D₁]methyllithium: Configurational Stability, Reactions, and Mechanistic Studies

Abstract

The configurational stability of enantiopure chiral (2,4,6-triisopropylbenzoyl)oxy-[D(1)]methyllithium generated by a tin-lithium exchange was tested on the macroscopic time scale, employing trapping experiments with benzaldehyde. It was found to be configurationally stable for minutes at -78 degrees C and to be an appropriate substitute for the carbamoyloxy-substituted analogue in terms of cleavage. Its addition to several electrophiles was studied, leading to a protocol for the preparation of chiral primary deuterated alcohols, exemplified by the synthesis of 2-phenyl-[1-D(1)]ethanol of 98% enantiomeric excess (ee). Furthermore, the mechanisms of enantiomerization and decomposition of this aroyloxymethyllithium were addressed by spectroscopic investigations of labeled substrates. It decomposed by formation of ethylene (minor pathway) and homologation of n-BuLi by up to three methylene units, followed by an exchange for a butyl group of Bu(4)Sn.