Cs 2 CO 3 Promoted [4 + 2] Cycloaddition of 1,6-Enynes: An Approach to Tetrahydro-1 H -benzo- f -isoindole Isomers.

A Cs 2 CO 3 -promoted [4 + 2] cycloaddition of 1,6-enynes under mild reaction conditions has been developed. This protocol provides a facile approach to a series of tetrahydro-1 H -benzo[ f ]isoindole isomerized products promoted by Cs 2 CO 3 with moderate to high yields. By simply switching the reaction solvent and controlling the reaction time, two isomerization products could be obtained, both with good selectivity.