Intramolecular Trapping of Alkyl- and Arylrhodium Hydride Intermediates in the Decarbonylation of Aldehydes by Chlorotris(triphenylphosphine)rhodium

Article abstract of DOI:10.1021/jo00178a008

The reaction of 5-hexenal with RhCl(PPh3)3 (1) or 2 (5) gives some cyclopentane.The reaction of 2-allylbenzaldehyde with 5 gives a good yield of indan.These cyclization reactions to give cyclopentanes, and other reactions of Δ⁴-enals to give cyclopropanes, reveal the presence of intermediate alkyl- and arylrhodium hydride complexes on the pathway for decarbonylation of aldehydes.The formation of nortricyclene from endo-5-norbornene-2-carboxaldehyde shows that the alkylrhodium hydride must be formed with retention of stereochemistry at the α-carbon of the aldehyde.