Synthese von stereoisomeren 3‐substituierten Cyclobutancarbonsäure‐Derivaten

Abstract

Synthesis of Stereoisomeric 3‐Substituted Cyclobutanecarboxylic Acid Derivatives The preparation of 3‐substituted cyclobutanecarboxylic acids by ring forming malonic ester cycloalkylation/saponification/decarboxylation leads to 50:50 cis / trans mixtures. Only some polar ester derivatives 2 can be separated by chromatographic methods. Catalytic hydrogenation of 3‐substituted cyclobutenecarboxylic acids 3 , however, gives the cis acids 4 with 90–95% selectivity. Reduction of the same acids 3 by Zn in aqueous HCl/THF leads to the trans acids 6 with 90–93% selectivity.