Highly selective glycine phase-transfer catalysis using fluoroanthracenylmethyl cinchonidine catalysts

Abstract

Fluoroanthracenylmethyl cinchonidine phase-transfer catalysts have been produced and explored for asymmetric glycine alkylation. The fluoroanthracenylmethyl precursors were made from aryloxazolidinones and aldehydes using an efficient electrophilic substitution with phosphorous pentoxide. The cinchonidine catalysts promote highly selective glycine alkylation under mild conditions. The 1,8-difluoroanthracenyl-10-methyl catalyst 6 (10 mol %) in toluene/THF with 50% aqueous KOH (−20 °C) promoted benzylation of glycine 1 to give 2 in 86% yield, 98% ee. Other electrophiles also gave excellent selectivity and reactivity.