A synthetic approach to 4-oxo and 4-thioxo azetidinones from heterocumulenes and ester enolates. A novel synthesis of 4-thio-acetoxy azetidin-2-ones.

Abstract

The addition of the ester enolates ( 3 ) to the heterocumulenes ( 4 ), yields acyclic derivatives ( 5 ), which can be cyclized to the thio or to the oxo malonimmides ( 1 ). A further elaboration of thiomalonimides ( 5a ) and ( 5c ) led to 4-thio-acetoxy azetidinones ( 10a ) and ( 10c ).