An Improved Synthesis of N-Isocyanoiminotriphenylphosphorane and Its Use in the Preparation of Diazoketones An Improved Synthesis of N-Isocyanoiminotriphenylphosphorane

During the course of recent studies on the formation of functionalized cyclopropanes via diazoketones, we required a safe, scalable alternative to diazomethane in the Arndt–Eistert synthesis of diazoketones.1 Trimethylsilyldiazomethane is often touted as a safe alternative to diazomethane, but the opportunity still exists for the in situ generation of diazomethane when using this reagent. Furthermore, the high cost and limited commercial availability of bulk quantities of TMSCHN2 conspire to make its use on pilot-plant and production scale undesirable.2 Safe, production-scale industrial use of diazomethane has been reported,3 but requires significant capital investment and thus does not fulfill the need for an off-the-shelf alternative to diazomethane. Recently, Aller and co-workers reported on the synthesis of diazoketones from the reaction of acid chlorides with N-isocyanoiminotriphenylphosphorane (1), a thermally stable, solid reagent.4