Rh-catalyzed [7 + 1] cycloaddition of buta-1,3-dienylcyclopropanes and CO for the synthesis of cyclooctadienones.

Discovering new carbon building blocks is very significant to advance transition-metal-catalyzed cycloadditions for the synthesis of various-sized ring compounds. A new seven-carbon building block from buta-1,3-dienylcyclopropanes (BDCPs) has been developed, showing that, under the catalysis of [Rh(CO)(2)Cl](2), BDCPs react with CO to give [7 + 1] cycloaddition products, cyclooctadienones. The present [7 + 1] reaction provides an efficient entry to the synthetically challenging eight-membered carbocyclic skeleton, which is present in many natural products of medicinal and biological significance.