The Partial Reduction of Carboxylic Acids to Aldehydes via 3-Acylthiazolidine-2-thiones with Diisobutylaluminum Hydride and with Lithium Tri-t-butoxyaluminum Hydride

Abstract

3-Acylthiazolidine-2-thiones, easily prepared from carboxylic acids and readily available thiazolidine-2-thione, were reduced to the corresponding aldehydes either with diisobutylaluminum hydride in toluene at −78–−40 °C in 70–90% yields or with lithium tri-t-butoxyaluminum hydride in tetrahydrofuran at −20-0 °C in 80–90% yields. The present method appears to be applicable to the synthesis of aldehydes from both aromatic and aliphatic derivatives having chloro, bromo, nitro, and noncojugated double bond, except for the reduction of α,β-unsaturated derivatives with lithium tri-t-butoxyaluminum hydride and of cyano derivative with diisobutylaluminum hydride. Completion of the reduction is indicated by disappearance of the original yellow color of the reaction mixture.