Rhodium(I)-Catalyzed Cyclization of Allenynes with a Carbonyl Group through Unusual Insertion of a CO Bond into a Rhodacycle Intermediate

Rhodium(I)‐catalyzed cyclization of allenynes with a tethered carbonyl group was investigated. An unusual insertion of a CO bond into the C(sp2)–rhodium bond of a rhodacycle intermediate occurs via a highly strained transition state. Direct reductive elimination from the obtained rhodacyle intermediate proceeds to give a tricyclic product containing an 8‐oxabicyclo[3.2.1]octane skeleton, while β‐hydride elimination from the same intermediate gives products that contain fused five‐ and seven‐membered rings in high yields. Unusual insertion: During the title reaction, a CO bond is inserted into the C(sp2)Rh bond of rhodacycle intermediate I. The insertion occurs via a highly strained transition state. Direct reductive elimination from II gives a tricyclic product containing an 8‐oxabicyclo[3.2.1]octane skeleton, whereas β‐hydride elimination from II gives products with fused five‐ and seven‐membered rings.