Synthesis of some 4-(2′-hydroxyaryl)-5-ethyl-2-(N, N-dialkylamino)-1,3-dithiolium salts

The synthesis of 4-(2′-hydroxyaryl)-5-ethyl-2-(N,N-dialkylamino)-1,3-dithiolium salts (6a–e) has been accomplished by the heterocyclization of the corresponding carbodithioates (3a–e). The required starting materials (1a,b) have been prepared by regioselective bromination of 1-(2′-hydroxyaryl)butanones (4a,b). Under basic conditions, salts 6a–e afford anhydro-hydroxides 7a–e, which are mesoionic compounds with an intramolecular charge-transfer UV/Vis absorption where the donor moiety is linked through σ-bonded bridges (C5-S1, C4-S3) to the acceptor moiety.