Thermal cyclisation of trans-o-fluorocinnamic acids to coumarins. An apparent similarity between mass spectral and thermal fragmentations

Abstract

The predominant fragmentation of the molecular ion derived from trans-pentafluorocinnamic acid involves the initial loss of hydrogen fluoride; this process is also important in the case of trans-o-fluorocinnamic acid. Pyrolyses of the acids lead to the formation of coumarin derivatives in good yield. The photolysis of an aqueous solution of sodium pentafluorocinnamate at 100° also results in the formation of 5,6,7,8-tetrafluorocoumarin.