Co(I) catalyzed yne-ene-yne [2+2+2] cycloaddition: synthesis of highly strained pentacyclic bis-lactones. A new access to tetraaryl N-hydroxyphthalimides

Highly strained pentacyclic bis-lactones can be obtained by an unusual Co(I) catalyzed [2+2+2] cycloaddition of an yne-ene-yne diester substrate. These bis-lactones can be further transformed into tetraaryl N-hydroxyphthalimides which are potential aerobic oxidation organocatalysts.