Photocatalytic Cross‐Pinacol Coupling Promoted by Carbon Dioxide**
Shintaro Okumura, Teruki Takahashi, Kaoru Torii, Yasuhiro Uozumi
Abstract
Abstract Cross‐pinacol coupling of two different carbonyl compounds was achieved through successive one‐electron transfer processes under photocatalytic conditions. In the reaction, an umpoled anionic carbinol synthon was generated in situ to react nucleophilically with a second electrophilic carbonyl compound. It was revealed that a CO 2 additive promoted the photocatalytic generation of the carbinol synthon to suppress undesired radical dimerization. A wide variety of aromatic and aliphatic carbonyl substrates underwent the cross‐pinacol coupling to afford the corresponding unsymmetric vicinal 1,2‐diols, in which even a combination of carbonyl reactants with similar structures such as two aldehydes and two ketones were also well tolerated with high cross‐coupling selectivity.