DIASTEREOSELECTIVE CYCLOCONDENSATION OF ELECTRON-RICH DIENES WITH CHIRAL THIO-SUBSTITUTED ALDEHYDES

The Lewis acid-promoted cyclocondensation between two electron -rich dienes with a series of racemic alpha- and beta-thio-substituted aldehydes has been studied. Boron trifluoride etherate proved to be the catalyst of choice, affording satisfactory chemical yields and generally good diastereoselectivities. Other Lewis acidic catalysts gave lower yields and in some cases reversed the sense of the diastereoselection. A rationalization of the stereochemical results is presented.