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Electroreduction of Organic Compounds, 19. — Formation of Benzoanellated Sulfur Heterocycles by Intramolecular Cathodic Cyclization of Dithiocarboxylic Esters Cathodic reduction of aryl (3) and benzyl (5) dithiopivaloates and related dithioesters with leaving groups at the benzene ring or a side chain yield the sulfur heterocycles 23, 30—32, and 34 depending on the nature of the starting material and the reaction conditions. In case of the α-oxo-dithioester 22, thioindigo (44) is formed. — The corresponding thioamides 14, 16, and 18 show a strong tendency to reductive dehalogenation but the S,N-heterocycles 38 and 39 are also formed in minor amounts. — The formation of the rearranged products 29—32, and 34 is discussed in terms of C,S-splitting in the primarily formed radical anion and subsequent C,C-coupling of the fragments and follow-up reactions. |
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