One‐Pot Solvent‐Free Synthesis of Diaryl 1,2‐Diketones by the Sequential Heck Oxidation Reaction of Aryl Halides with Styrenes

A novel one‐pot procedure for the synthesis of benzil derivatives was developed by the sequential Heck oxidation reaction of aryl halides (I and Br) with styrenes. In situ‐generated stilbene scaffolds were directly converted to the corresponding diaryl 1,2‐diketones. In the present transformation, tetrabutylammonium iodide (TBAI) was employed as a dual role reagent, one as a reducing agent in Heck reaction and another as a catalyst in the oxidation step. Mechanistic studies showed that molecular oxygen plays a significant part in the oxidation step. Various derivatives of diaryl 1,2‐diketones were synthesized through this protocol in acceptable yields. Say no to solvent: Heck reaction of aryl halides with styrenes followed by an oxidation of the corresponding intermediate in the presence of a Pd/TBAI/TBHP combination system as an efficient and one‐pot procedure results in the synthesis of benzil derivatives. TBAI= tetrabutylammonium iodide; TBHP=tert‐butyl hydroperoxide.