We report the regioselective carbonylation of 2,2-disubstituted epoxides to beta,beta-disubstituted beta-lactones. Mechanistic studies revealed epoxide ring-opening as the turnover limiting step, an insight that facilitated the development of improved reaction conditions using weakly donating, ethereal solvents. A wide range of epoxides can be carbonylated to beta-lactones, which are subsequently ring-opened to produce ketone-based aldol adducts, providing an alternative to the Mukaiyama aldol reaction. Enantiopure epoxides were demonstrated to undergo the carbonylation/ring-opening process with retention of stereochemistry to form enantiopure beta-hydroxy esters.