Synthesis and Conformational Analysis of Dibenzodithiocin Derivatives

Article abstract of DOI:10.1002/mrc.1260270809

N-(3,4-Dialkoxyphenylthiomethyl)aroylamides (1a, b) reacted with phosphoryl chloride to give not only the expected 4H- and 2H-1,3-benzothiazine derivatives (4a, b and 5a, b), but also dibenzodithiocins of new (dibenzo<1,3>dithiocins 2a, b) and known (dibenzo<1,5>dithiocins 3a, b) types.The analogous reaction of the 4-methylaroylamide 8a furnished the 4H-1,3-benzothiazine 9a, the dibenzo<1,5>dithiocin derivative 10a and benzonitrile.In contrast, 8b (the chloro analogue of 8a) furnished only benzonitrile and bis(4-chlorophenylmercapto)methane (11).The structures of the new compounds were confirmed by IR, 1H and 13C NMR, and (in part) by mass spectrometry.Temperature-dependent 1H NMR studies were used for the conformational analysis of 2a and its disulphone 6a; the nature and free enthalpies of activation of the two different conformational motions occuring at higher temperatures were determined.KEY WORDS - Dibenzodithiocins Synthesis 1H and 13C NMR Conformation Structural isomerism