Biradical processes in reactions between benzyne and tropone

The title reactions were investigated experimentally and theoretically. The benzyne--tropone pair has been known to give a Diels–Alder [4+2] cycloadduct. However, in the present experiment using two sources of benzyne, many unexpected products were obtained. In particular, a zwitterion with a C–Cl bond is strikingly a major product, the structure of which was determined by the X-ray analysis. The bond is formed by quenching the Cl atom from the solvent CH 2 Cl 2 , which demonstrates that the reactions proceed via radical processes. DFT calculations revealed the elementary processes of the reactions. The presence of the novel zwitterion in the solid state has been interpreted in terms of the permanent dipole–dipole attractions/interactions/stabilization.