A solution of the carbonyl compound, acetal or ketal (1 equiv), in anhydrous dichloromethane (3 M) was added in a dropwise fashion to a solution of Me3SiOTf or MeSSiI (5%) and 2 (1.2-1.3 equiv) in dichloromethane at-78" C (ca. 1 M final concentration). In some cases, di-tert-butylpyridine (2%) was also present. The solution was stirred at the temperature/time indicated in Table I. On occasion, additional MesSiOTf catalyst was ...
