meta-Benzyne reacts as an electrophile

Examination of gas-phase reactions of various nucleophiles with meta-benzyn e analogues that carry a positively charged substituent has revealed that t he meta-benzyne moiety is susceptible to nucleophilic attack. Addition of n ucleophiles to the meta-benzyne moiety occurs rapidly without energy-demand ing uncoupling of the singlet biradicals' formally unpaired electrons. The resulting zwitterionic intermediate may undergo fragmentation either by a h omolytic bond cleavage to yield net-radical type products or by a heterolyt ic bond cleavage that generally leads to replacement of the original charge d group with the incoming nucleophile. The intermediate was characterized e xperimentally and computationally and found to be a low-energy species. The nonradical reactivity reported here is common for meta-benzynes with posit ively charged substituents, and is predicted also to dominate the chemistry of anionic and neutral meta-benzynes.