The Addition of Alkylation alfa-Hydroxy-benzylphosphonates to Dialkyl Acetylenedicarboxylates; Catalytic Hydrogenation of the Adducts

Abstract

alfa-Hydroxy-benzylphosphonates obtained by the Pudovik reaction of substituted benzaldehydes and dialkyl phosphites were added on the triple bond of dialkyl acetylenedicarboxylates. Optimum conditions involved a 24 h’ stirring in the presence of 10% of diazabicycloundecene in dichloromethane to afford the adducts as a mixture of predominant “E” and a minor “Z” izomers in 75–90% yields after flash chromatography. Structure of the geometrical isomers was confirmed by NOE- and ROE measurements. Catalytic hydrogenation of the olefinic moiety of the adducts led to the diastereomers of corresponding saturated derivatives.