Synthese von einigen 2 H ‐Pyran‐2‐on‐Derivaten

The Synthesis of Some 2 H ‐Pyran‐2‐one Derivatives Derivatives of 6‐unsubstituted 2 H ‐pyran‐2‐one have been synthesized by several different methods. The 4‐chloro‐2 H ‐pyran‐2‐one ( 9 ) is the most important, since it serves as starting material for the synthesis of different 4‐substituted 2 H ‐pyran‐2‐ones ( Scheme 2 ). Also described are simple transformations of cumalic‐acid derivatives producing 5‐(2,2‐dichlorovinyl)‐2 H ‐pyran‐2‐one ( 23 ), 2‐oxo‐2 H ‐pyran‐2‐carbonitrile ( 26 ), and 4,5‐bis(trifluoromethyl)‐2 H ‐pyran‐2‐one ( 32 ) ( Scheme 3 and 4 ).