Iron phthalocyanine-catalyzed radical phosphinoylazidation of alkenes: A facile synthesis of β-azido-phosphine oxide with a fast azido transfer step

Abstract

Phosphinoylazidation of alkenes is a direct method to build nitrogen- and phosphorus-containing compounds from feed-stock chemicals. Notwithstanding the advances in other phosphinyl radical related difunctionalization of alkenes, catalytic phosphinoylazidation of alkenes has not yet been reported. Here, we describe the first iron-catalyzed intermolecular phosphinoylazidation of styrenes and unactivated alkenes. The method is practically useful and requires a relatively low loading of catalyst. Mechanistic studies confirmed the radical nature of the reaction and disclosed the unusually low activation energy 4.8 kcal/mol of radical azido group transfer from the azidyl iron(III) phthalocyanine species (PcFeIIIN3) to a benzylic radical. This work may help to clarify the mechanism of iron-catalyzed azidation, inspire other mechanism studies and spur further synthetic applications.