Elektroreduktion organischer Verbindungen, 19 Bildung benzoanellierter Schwefelheterocyclen durch intramolekulare kathodische Cyclisierung von Dithiocarbonsäureestern

Abstract

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.