Reductive ring opening of 2-azetidinones promoted by sodium borohydride

Variously substituted 2-azetidinones 3 and 4 were reacted with sodium borohydride in aqueous isopropanol giving 3-aminopropan-1,2-dioles 5 and 7. Reaction extent was dependent upon the substitution pattern in the 3- and 4-positions of the 2-azetidinone ring and revealed good correlation with carbonyl LUMO energies of starting 3.