C-C Bond Cleavage of 8-Quinolinyl Alkyl Ketone by σ,η³-Allyl Rhodium(III) Complex

Bis(ethylene)rhodium(I) chloride dimer reacted with vinylcyclopropane to give σ,η³-allylrhodium(III) complex 3. Complex 3 underwent C-C bond cleavage of 8-quinolinyl ethyl ketone 11, to form η³-1,3-dimethylallylrhodium(III) complex 8, which was reductively eliminated by trimethyl phosphite to give 8-quinolinyl-1-methylbut-2-enyl ketone (10). More sterically hindered 8-quinolinyl alkyl ketones were allowed to react with complex 3 to afford corresponding alkenes as well as a mixture of complex 8 and η³-1-ethylallyl rhodium(III) complex 19, identified as 10 and 8-quinolinyl-pent-2-enyl ketone (20) after reductive elimination. 8-Quinolinyl alkyl ketone bearing a sterically hindered alkyl group showed less reactivity for C-C bond cleavage and higher 20/10 ratio compared with those having a less sterically hindered alkyl group, such as 8-quinolinyl ethyl ketone (11).