Organoiron-and Fluoride-Catalyzed Phosphinidene Transferto Styrenic Olefins in a Stereoselective Synthesis of UnprotectedPhosphiranes

摘要

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 = C14H10, anthracene) and styrene in 73% and 57% isolated yields, respectively. The cocatalyst system requires tetramethylammonium fluoride (TMAF) and [Fp(THF)][BF4] (Fp = Fe(η⁵-C5H5)(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)][BF4] with TMAF. Two other plausible reaction intermediates, [Fp(t-BuP>A)][BF4] and [Fp(>1-t-Bu)][BF4], were prepared independently and structurally characterized.