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An unexpected isomerization of N-Aryl-3-amino-4-nitroisothiazol-5(2H)-imines to 2-(Benzothiazol-2-y1)-2-nitroethene-1,1-diamines


Moya Argilagos, Dally; Garcia Trimino, Maria I; Macias Cabrera, Arturo; Linden, Anthony; Heimgartner, Heinz (1997). An unexpected isomerization of N-Aryl-3-amino-4-nitroisothiazol-5(2H)-imines to 2-(Benzothiazol-2-y1)-2-nitroethene-1,1-diamines. Helvetica Chimica Acta, 80:273-292.

Abstract

The syntheses of several N-aryl-3-amino-4-nitroisothiazol-5(2H)-imines 12 from 3,3-diamino-2-nitrothioacrylamides 11 are reported (Scheme 3). In polar solvents, a spontaneous isomerization of some of the prepared isothiazol-5(2H)-imines 12 yielded benzothiazoles 13 (Scheme 4). In the case of 2-alkyl-substituted derivatives of type 12, the isomerization occurred only at higher temperatures. Electronic influences of different substituents on the rate of the isomerization were studied, and a polar reaction mechanism is proposed in Scheme 6. The structures of 12e and 13e were established by X-ray crystallography. Conformational analyses of 3-(methylamino)-2-nitro-N-phenyl-3-(pyrrolidin-1-yl)thioacrylamide (11l) by NMR and X-ray methods were performed with the aim of explaining the distinct behavior of this amide towards Br2 or diethyl azodicarboxylate.

Abstract

The syntheses of several N-aryl-3-amino-4-nitroisothiazol-5(2H)-imines 12 from 3,3-diamino-2-nitrothioacrylamides 11 are reported (Scheme 3). In polar solvents, a spontaneous isomerization of some of the prepared isothiazol-5(2H)-imines 12 yielded benzothiazoles 13 (Scheme 4). In the case of 2-alkyl-substituted derivatives of type 12, the isomerization occurred only at higher temperatures. Electronic influences of different substituents on the rate of the isomerization were studied, and a polar reaction mechanism is proposed in Scheme 6. The structures of 12e and 13e were established by X-ray crystallography. Conformational analyses of 3-(methylamino)-2-nitro-N-phenyl-3-(pyrrolidin-1-yl)thioacrylamide (11l) by NMR and X-ray methods were performed with the aim of explaining the distinct behavior of this amide towards Br2 or diethyl azodicarboxylate.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:1997
Deposited On:18 Nov 2013 09:57
Last Modified:07 Dec 2017 23:47
Publisher:Wiley-Blackwell
ISSN:0018-019X
Funders:Schweizerische Eidgenössische Stipendienkommission, F. Hoffmann-La Roche AG
Publisher DOI:https://doi.org/10.1002/hlca.19970800125

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