New aspects of phosphirene chemistry

Abstract

Two methodologies have been tested for the functionalization of phosphirenes. In the first one, the C−Si bond of a 2-silylphosphirene is activated by a substoichiometric quantity of fluoride ion (TBAF) in THF at −78 °C. Using this technique, it is possible to perform a protodesilylation or a functionalization by benzaldehyde. However, at room temperature with a stoichiometry of fluoride, a nucleophilic attack takes place at P, leading to a ring-opened fluorophosphine. Stille cross-coupling with a 2-stannylphosphirene in the presence of [PdL2] as a catalyst leads to an alkynylphosphine by [1,3] migration of tin from C to P. Next, special chemistry of 2-aminophosphirene: the reaction of the bulkyynamine PhCCNiPr2 with terminal phosphinidene complexes [R−PW(CO)5], generated from phosphanorbornadiene complex, affords the corresponding phosphirenes (R = Ph, OMe) and the diphosphetene (R = Me). The reaction of this phosphirene with dimethyl acetylenedicarboxylate gives the phosphole resulting from the insertion of the alkyne into the P−C(N) bond and the tetrafunctional arene resulting from [2+2+2] cycloaddition of one alkyne with two phosphirene units. Finally, the reaction of strong Lewis acids with 2-amino-3-phenylphosphirene pentacarbonyltungsten complexes leads to the corresponding 2-amino phosphindoles through the unexpected formation of a bond between phosphorus and one of the ortho carbons of the phenyl ring.