A general synthetic route to differentially functionalized angularly and linearly fused [6-7-5] ring systems: a Rh(I)-catalyzed cyclocarbonylation reaction.

Investigations of a Rh(I)-catalyzed cyclocarbonylation reaction reveal its general synthetic utility for accessing highly functionalized tricyclic [6-7-5] linear and angular ring systems from allene-ynes. Three types of allene-ynes were prepared and subjected to Rh(I)-catalyzed cyclocarbonylation conditions. For three series of allene-ynes, the [6-7-5] ring systems were afforded in varying yields depending on the substrate structure. One series of allene-ynes afforded the [6-6-5] ring system possessing an alpha-alkylidene cyclopentenone as a result of a selective reaction with the proximal double bond of the allene.