Highly diastereoselective desymmetrizing intramolecular cyclization of allylstannane with a diketone promoted by Lewis acid or transition metal complex

The Lewis acid mediated desymmetrizing intramolecular cyclization of prochiral allylstannyl diketone (1) gave a mixture of two diastereomers (2 and 3). Highly diastereoselective synthesis of each of the diastereomers was accomplished by appropriate choice of the Lewis acid. Compound 3 was also produced stereoselectively by using a palladium catalyst instead of Lewis acid.