SRN1 REACTIONS OF ARYLHALODIAZIRINES WITH AZIDE ION

(m-(Trifluoromethyl)phenyl)bromodiazirine, 10, reacts with 15N terminally labeled sodium azide in dimethyl sulfoxide to give m-(trifluoromethyl)benzonitrile which, in all cases, contains 15N incorporation. The largest amount of label incorporation (42%), and the fastest rate, is observed when the reaction is carried out in room light. The smallest amount of label incorporation (11%), and the slowest reaction, is observed when the reaction is carried out in the dark and a trace of the free radical, galvinoxyl, is added. The reaction in the light is proposed to occur mainly via the SRN1 chain process. The intermediate C-azidodiazirine substitution product is not observed, but presumably rapidly loses 2 mol of nitrogen to give the nitrile product. (p-Nitrophenyl)bromodiazirine, 20, can also react with azide ion via an analogous SRN1 process, and the reaction is more facile than that of 10. Label incorporation from 15N-labeled sodium azide is substantial (47.3%) and is in agreement with the proposed SRN1 process. A variety of arylchlorodiazirines, substituted with electron-deficient aromatic groups, also react with azide ion in room light, to give nitriles via C-azidodiazirines, which lose molecular nitrogen. Evidence for the proposed SRN1 process includes initiation of the reaction by exposure to room light, initiation by the addition of the sodium salt of 2-nitropropane or sodium thiophenoxide, and inhibition of the reaction by the addition of galvinoxyl. In the case of these arylchlorodiazirines, reaction with 15N terminally labeled sodium azide led to 15N label incorporation approaching the maximum amount possible for a reaction proceeding exclusively via C-azidodiazirines. These studies show the propensity for arylhalodiazirines to undergo reaction initiated by electron-transfer processes. © 1990, American Chemical Society. All rights reserved.