A new simple route for the synthesis of (±)-2-azetidinones starting from β-enaminoketoesters

β-Enaminoketoesters 1, obtained through metal-catalysed reaction of methyl acetoacetate with alkyl cyanoformates have been conveniently transformed into β-aminoesters 4, 5 by reduction of both the carbonyl group and the carbon–carbon double bond of the enaminoester moiety. These intermediates could be easily converted to (±)-2-azetidinones 6, 7 structurally related to thienamycin in good yield and high diastereoselectivity.