Reactivity of 1-chloro-3-phenyldiazirines.
p-Substituted 1-chloro-3-phenyldiazirines (5), the putative intermediates of the reaction of N,N,N'-trichlorobenzamidines (10) with excess of bromide ions, react further to afford mixtures of 3-bromo- (4) and 3-chloro-3-phenyldiazirines (6). The 6:4 ratios inversely correlate with the Hammett sigma(p) and sigma(p)+ constants of the p-substituents. The formation of 4, proposed to proceed by anti-S(N)2' mechanism, is predominant with electron-withdrawing p-substituents. Compounds 6, the major products with electron-donating p-substituents, may arise from 5 by a [1,3]-sigmatropic shift of chlorine proceeding via polar transition structures 12. The results of a gas-phase DFT (B3LYP/6-31+G*) study on the two mechanisms are consistent with experiment.
Martinu
Tomas
T
Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Dailey
William P
WP
D003978:Diazomethane / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure
D003978:Diazomethane