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Exceptional Products of the Desulfurization of N ,2‐Diaryl‐5‐(arylimino)‐ 2,5‐dihydro‐4‐nitroisothiazol‐3‐amines
Author(s) -
Moya Argilagos Dally,
Linden Anthony,
Heimgartner Heinz
Publication year - 1999
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/(sici)1522-2675(19990210)82:2<238::aid-hlca238>3.0.co;2-h
Subject(s) - chemistry , ketene , flue gas desulfurization , imine , quinoxaline , medicinal chemistry , combinatorial chemistry , stereochemistry , organic chemistry , catalysis
The desulfurization of several N ,2‐diaryl‐5‐(arylimino)‐2,5‐dihydro‐4‐nitroisothiazol‐3‐amines 5 with Ph 3 P led to complex mixtures of products in low yields. For instance, quinoxaline‐2‐carboxamide 1‐oxides of type 6 ( Scheme 2 ) and, in some cases, also 3‐nitroquinolines of type 7 ( Scheme 5 ) were isolated. By the desulfurization of the substituted derivatives 5b – e , a rearrangement of the intermediates yielded 6 and 7 with a different substitution pattern from that expected from the starting materials ( Scheme 3 ). The additional formation of two isomeric 1,2,5‐oxadiazole‐3‐carboxamides 8 was observed only in the case of 5d (R 1 =R 2 =F) ( Scheme 6 ). Under the same reaction conditions, the major product of the desulfurization of 5c was the quinoxaline‐2‐carboxamide 1‐oxide 9 ( Scheme 7 ). Reaction mechanisms involving intermediate ketene imines and O transfer from the NO 2 group to the neighboring ketene imine are proposed. The structures of 6a , 6e , 6k , 7b , and 8d were established by X‐ray crystallography, while the structure of 9 was elucidated by 2D‐NMR spectroscopy and corroborated by X‐ray crystallography.