Selective Synthetic Routes to Sterically Hindered Unsymmetrical Diaryl Ketones via Arylstannanes

Bulky arylstannanes and bulky aroyl chlorides are good reaction partners for the synthesis of two-, three-, and even four-ortho-substituted benzophenones, in good to excellent isolated yields (47-91%). Three simple and direct routes, with differential advantages, are proposed: (i) a catalyst-free protocol, in o-dichlorobenzene (ODCB) at 180 degrees C; (ii) a room temperature protocol, using AlCl3 (0.5 equiv), in dichloromethane (DCM); and (iii) a solvent-free, indium-promoted procedure. A radical mechanism is proposed for the indium-mediated reactions.