Organoiron- and Fluoride-Catalyzed Phosphinidene Transfer to Styrenic Olefins in a Stereoselective Synthesis of Unprotected Phosphiranes

Catalytic phosphiranation has been achieved, allowing preparation of trans -1-R-2-phenylphosphiranes (R = t -Bu: 1 - t -Bu; i -Pr: 1 - i -Pr) from the corresponding dibenzo-7-(R)-7-phospha-norbornadiene (RP A , A = C 14 H 10 , anthracene) and styrene in 73% and 57% isolated yields, respectively. The cocatalyst system requires tetramethylammonium fluoride (TMAF) and [Fp(THF)][BF 4 ] (Fp = Fe(η 5 -C 5 H 5 )(CO) 2 ). In the case of the t -Bu derivative, the reaction mechanism was probed using stoichiometric reaction studies, a Hammett analysis, and a deuterium labeling experiment. Together, these suggest the intermediacy of iron-phosphido FpP(F)( t -Bu) ( 2 ), generated independently from the stoichiometric reaction of [Fp( t -BuP A )][BF 4 ] with TMAF. Two other plausible reaction intermediates, [Fp( t -BuP A )][BF 4 ] and [Fp( 1 - t -Bu)][BF 4 ], were prepared independently and structurally characterized.