Exocyclic P–C vs. endocyclic P–P bond cleavage in 1,2-diphosphetes. A competition between cyclic delocalization and cyclic strain controlled by the substitution pattern

Abstract

Attack by lithium on 1,2-diphenyl-3,4-di-R-substituted-1,2-diphosphetes takes place on the endocyclic P–P bond where R = Ph whreas it takes place on the exocyclic P-Ph bond when RBu^t; in this latter case, a 1,2-diphosphet-1-yl anion is obtained which is probably stabilized by cyclic delocalization.