Rhodium-Catalyzed Regioselective and Chemoselective Deoxygenative Reduction of 1,3-Diketones

Aldehyde Olefination with Arylboroxines Enabled by Binary Rhodium Catalysis

A rhodium-catalyzed olefination of aliphatic aldehydes with arylboroxines is described. The simple rhodium(I) complex [Rh(cod)OH]₂ without any external ligands or additives is able to catalyze the reaction in air and neutral conditions, allowing the construction of aryl olefins in an efficient manner with a good functional group tolerance. The mechanistic investigation illustrates that the binary rhodium catalysis is the key for the transformation, which involves a Rh(I)-catalyzed 1,2-addition and a Rh(III)-catalyzed elimination.

Electrochemical deoxygenative reduction of ketones

Electrochemical reduction via paired electrolysis has been used to achieve deoxygenative reduction of ketones. As a result of the complexing of ketones with the triphenylphosphine radical cation generated by anodic oxidation, the reduction of carbonyl groups occurs readily. Through spontaneous β-scission of phosphoranyl radicals, C-O bonds are cleaved to form benzylic radical intermediates. These radical species are either able to abstract hydrogen from MeCN or undergo reduction at the cathode to give carbanions, upon workup forming reductive hydrogenation of ketones.