Rh-catalyzed [5+1] and [4+1] cycloaddition reactions of 1,4-enyne esters with CO: a shortcut to functionalized resorcinols and cyclopentenones

We have developed novel Rh-catalyzed n+1]-type cycloadditions of 1,4-enyne esters, which involve an acyloxy migration as a key step. The efficient preparation of functionalized resorcinols, including biaryl derivatives, from readily available 1,4-enyne esters and CO was achieved by Rh-catalyzed 5+1] cycloaddition accompanied by 1,2-acyloxy migration. When enyne esters had an internal alkyne moiety, the reaction proceeded by a 4+1]-type cycloaddition involving 1,3-acyloxy migration, leading to cyclopentenones.