Rhodium(I)-catalyzed reductive cyclocarbonylation of internal alkynes: atom-economic process for synthesis of 2-cyclopenten-1-ones, 5-alkylidenefuran-2(5 H)-ones and indan-1-ones.

The reductive cyclocarbonylation of internal alkynes with carbon monoxide catalyzed by [{RhCl(CO)(2)}(2)]/CO(NH(2))(2) in the presence of water has been investigated. Dialkyl alkynes underwent a reductive [2+2+1] cyclocarbonylation to afford selectively cis-2-cyclopenten-1-ones in high yields. In the cases of diarylacetylenes used, both trans-2-cyclopenten-1-ones and 5-alkylidenefuran-2(5 H)-ones were obtained, and the presence of electron-withdrawing group on the benzene ring enhanced the formation of 5-alkylidenefuran-2(5 H)-ones. On the other hand, ortho-substituted diarylacetylenes underwent a reductive [4+1] cyclocarbonylation to produce selectively indan-1-ones in good yields.