Reactions of 1,3,4-triphenyl-1,2-dihydrophosphete

Abstract

In contrast to previously reported reactivity of the tungsten pentacarbonyl complex of a 2-substituted 1,2-dihydrophosphete, which apparently undergoes electrocyclic ring opening to the corresponding 1-phospha-1,3-butadiene and subsequent [4+2] cycloaddition reactions with dienophiles, the reaction chemistry of 1,3,4-triphenyl-1,2-dihydrophosphete is dominated by its nucleophilic nature. Although low to modest yields of cycloadducts are obtained with some dienophiles, the reactions forming these products are apparently stepwise, as indicated by the loss of stereochemistry in the reaction of dimethyl maleate and in the competitive formation of a phosphorus-free dimer in the reaction of N-methylmaleimide. Dimethyl acetylenedicarboxylate affords three major products, each of which incorporates two equivalents of the acetylene, again apparently a result of initial nucleophilic addition of the dihydrophosphete to the “dienophile.” © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:9–19, 1998