Rhodium(I)-catalyzed [4+2+2] cycloadditions of 1,3-dienes, alkenes, and alkynes for the synthesis of cyclooctadienes

The first 4+2+2] cycloadditions involving terminal alkynes and diene-enes, including a fully intramolecular example, are reported resulting in the formation of cyclooctadienes using RhCl(CO)2]2 (5 mol %) treated with AgSbF6 (10 mol %) as a precatalyst. The reaction is general for a variety of terminal alkynes, as well as variously substituted diene-enes (yields up to 88%).