Synthesis of 3-methyleneazetidin-2-one derivatives from α-keto-amides

Abstract

Several α-methyleneazetidin-2-one derivatives (CH₂[graphic omitted]HR², R¹= cyclohexyl, PhCH₂; R²= H, Me, Et, Prⁿ, etc.) were prepared from the 2-(2,4,6-tri-isopropylbenzenesulphonylhydrazones) of primary α-ketoamides (CH₃COCONHR¹) using the Shapiro reaction. Thus, trimetallation of these hydrazone derivatives at –78 °C and warming to between –10 and +25° C gave the allenic dianions [CH₂CC(O^–)N^–R]. Reaction of these with the aldehydes (R²CHO), followed by toluene-4-sulphonyl chloride or -sulphonic anhydride, gave the title β-lactams.