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

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