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

Economical atoms : 2‐Cyclopenten‐1‐ones, 5‐alkylidenefuran‐2(5  H )‐ones and indan‐1‐ones have been synthesized by atom‐economic reductive cyclocarbonylation of internal alkynes with carbon monoxide catalyzed by [{RhCl(CO) 2 } 2 ]/CO(NH 2 ) 2 in the presence of water (see scheme).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.