SEQUENCE OF REACTANT COMBINATION ALTERS THE COURSE OF THE STAUDINGER REACTION OF AZIDES WITH ACYL DERIVATIVES - BIMANES .30.

The Staudinger reaction of azides has now been followed by NMR and oth er spectroscopic techniques. syn-(Azidomethyl,methyl)(methyl,methyl)bi mane (1) and Ph(3)P form a triazaphosphadiene intermediate 2 and then the bimane P-triphenyliminophosphorane 3. The iminophosphorane reacts with an acyl chloride to yield an iminophosphonium salt 4 which then f orms the oxazaphosphetane 13. The latter undergoes an electrocyclic re version to form the phosphine oxide and the chloroimines 7E and 7Z, th e last being hydrolyzed to the (acylamido)bimane 6. This set of reacti ons constitutes the ''iminophosphorane pathway''. A significant divers ion of the reaction path to an (N-alkylamino)phosphonium chloride 8 oc curs through reaction of 4 with H2O present in the CDCl3 and through r eaction of 3 with HCl. A different azide (alpha-azido-o-xylene Ib) pro duces the (acylamido)-o-xylene as the sole product. A less sterically hindered phosphine (tri-2-furylphosphine) reacts more slowly to form t he iminophosphorane 3a from the azidobimane 1. Reaction of the bimane P-tri-2-furyliminophosphorane with acyl chloride gives only the (acyla mido)bimane 6. If the acyl chloride is mixed with 1, followed by addit ion of the Ph(3)P, the triazaphosphadiene adduct 5 is formed via the t riazaphosphadiene. The adduct 5 is converted rapidly into a six-member ed cyclic compound 11. The latter either loses nitrogen to yield 6 via 72 and 7E and the phosphine oxide or loses chloride 10 through a nove l chloride-induced elimination reaction from its protonated form. The change in procedure thus results in a dramatic change in the reaction pathway, a reaction set that constitutes the ''triazaphosphadiene addu ct pathway''. In the case of alpha-azido-o-xylene, alpha-chloro-xylene (10b) is the only product. The reactions of the azides 1 or Ib with t ri-2-furylphosphine also produce chlorides as the major products accom panied by some acetamido derivatives. The nucleophile-induced reaction explains a ''surprising result'' (formation of ester rather than amid e) reported by Sahlberg et al. (Sahlberg, C.; Jackson, A. M.; Claesson , A. Acta Chem. Scand. 1888, B42, 556-562). The intramolecular ''aza-W ittig'' reaction may depend on the nucleophilicity of the triazaphosph adiene. A comprehensive mechanistic scheme for the Staudinger reaction of azides is conveniently divided into the following: (A) formation o f the triazaphosphadiene (Scheme 1), (B) reactions of the triazaphosph adiene (Scheme 2), and (C) reactions via the iminophosphorane (Scheme 3). Some approximate kinetic parameters are reported for some of the r eactions.