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Oxidation of ( Z , Z )‐1,4‐Diaminobuta‐1,3‐diene‐1,4‐dithiolates and Related Precursors − Alternatives For 1,2‐Dithiin Formation
Author(s) -
Schroth Werner,
Spitzner Roland,
Felicetti Michael,
Wagner Christoph,
Bruhn Clemens
Publication year - 2000
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200009)2000:17<3093::aid-ejoc3093>3.0.co;2-k
Subject(s) - chemistry , dimer , ring (chemistry) , heteroatom , diene , disulfide bond , stereochemistry , monomer , polymer , organic chemistry , biochemistry , natural rubber
Oxidation of the title compounds, in contrast to that of “normal” ( Z , Z )‐buta‐1,3‐diene‐1,4‐dithiolates, does not lead to the formation of 1,2‐dithiins. Thus, the aliphatic diaminodithiolates 7 and 8 were converted into the ( E )‐2‐butenedithioamides 12 and 15 as a result of resonance stabilization of the thiocarbonyl group. On the other hand, the 3,3′‐biindole‐2,2′‐dithiolate 9 , the aromatic counterpart of 8 , undergoes disulfide formation with preservation of aromaticity in the hetarene rings and yields the 1,2‐dithiin dimer 31 with a 12‐membered ring structure. In this instance, the formation of the expected ( E )‐3,3′‐biindolinylidene‐2,2′‐dithione 29 (a thioxo analogue of isoindigo) does not take place, paralleling the general problems for the existence of thioxo indigoid compounds 37 . On the other hand, oxidation of the 2,2′‐bi‐hetarene‐3,3′‐dithiolates 34 [formally, ( Z,Z )‐buta‐1,3‐diene‐1,4‐dithiolates with π‐donor substituents X in the 2‐ and 3‐positions] affords either monomeric ( 38c ) or dimeric 1,2‐dithiins (e.g. 39a , b , d ) depending on the heteroatom X in the anellated hetarene ring. It was possible to correct some longstanding erroneous structures: such as the 3,6‐diamino‐1,2‐dithiins 20 in favor of the ( E )‐2‐butenedithioamides 22 , and the alleged thioxoisoindigo 29 − obtained from 1‐methylindoline‐2‐thione ( 23 ) and N , N ‐dimethyl‐4‐nitrosoaniline − in favor of the 1,2‐dithiin dimer 31 .