Reactions of phosphines with acetylenes. Part XIV. Isomeric 1 : 2 adducts from triarylphosphines and dimethyl acetylenedicarboxylate. A cyclopentenylidenephosphorane

Abstract

The reaction of triphenylphosphine and an excess of dimethyl acetylenedicarboxylate gives in addition to the 2H-phosph(V)ole (1), a second product—the cyclopentenylidenephosphorane (2). Reduction of (2) to the dihydro-compound (7) followed by base-catalysed elimination of methanol, gives the cyclopentadienylidenephosphorane (8). The i.r., u.v., n.m.r., and mass spectra of these compounds are discussed.