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Reaktionen von 3-(Dimethylamino)-2H-azirinen mit 1,3-Benzoxazol-2(3H)-thion


Ametamey, Simon M; Heimgartner, Heinz (1990). Reaktionen von 3-(Dimethylamino)-2H-azirinen mit 1,3-Benzoxazol-2(3H)-thion. Helvetica Chimica Acta, 73(3):599-607.

Abstract

The reaction of 3-(dimethylamino)-2H-azirines 2 with 1,3-benzoxazole-2(3H))-thione (5), which can be considered as NH-acidic heterocycle (pKa ca. 7.3), in MeCN at room temperature, leads to 3-(2-hydroxyphenyl)-2-thiohydantoins 6 and thiourea derivatives of type 7 (Scheme 2). A reaction mechanism for the formation of the products via the crucial zwitterionic intermediate A' is suggested. This intermediate was trapped by methylation with MeI and hydrolysis to give 9 (Scheme 4). Under normal reaction conditions, A' undergoes a ring opening to B which is hydrolyzed during workup to yield 6 or rearranges to give the thiourea 7. A reasonable intermediate of the latter transformation is the isothiocyanate E (Scheme 3) which also could be trapped by morpholine. In i-PrOH at 55-65°, 2a and 5 react to yield a mixture of 6a, 2-(isopropylthio)-1,3- benzoxazole (12), and the thioamide 13 (Scheme 5). A mechanism for the surprising akylation of 5 via the intermediate 2-amino-2-alkoxyaziridine F is proposed. Again via an aziridine, e.g. H (Scheme 6), the formation of 13 can be explained.

The reaction of 3-(dimethylamino)-2H-azirines 2 with 1,3-benzoxazole-2(3H))-thione (5), which can be considered as NH-acidic heterocycle (pKa ca. 7.3), in MeCN at room temperature, leads to 3-(2-hydroxyphenyl)-2-thiohydantoins 6 and thiourea derivatives of type 7 (Scheme 2). A reaction mechanism for the formation of the products via the crucial zwitterionic intermediate A' is suggested. This intermediate was trapped by methylation with MeI and hydrolysis to give 9 (Scheme 4). Under normal reaction conditions, A' undergoes a ring opening to B which is hydrolyzed during workup to yield 6 or rearranges to give the thiourea 7. A reasonable intermediate of the latter transformation is the isothiocyanate E (Scheme 3) which also could be trapped by morpholine. In i-PrOH at 55-65°, 2a and 5 react to yield a mixture of 6a, 2-(isopropylthio)-1,3- benzoxazole (12), and the thioamide 13 (Scheme 5). A mechanism for the surprising akylation of 5 via the intermediate 2-amino-2-alkoxyaziridine F is proposed. Again via an aziridine, e.g. H (Scheme 6), the formation of 13 can be explained.

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Additional indexing

Other titles:Reaction of 3-(Dimethylamino)-2H-azirines with 1,3-Benzoxazole-2(3H)-thione
Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:German
Date:1990
Deposited On:27 Mar 2014 15:33
Last Modified:05 Apr 2016 17:46
Publisher:Wiley-Blackwell
ISSN:0018-019X
Funders:Schweizerischer Nationalfonds zur Förderung der wissenschaftlichen Forschung, F. Hoffmann-La Roche AG, Basel, Prof. Hans-E.-Schmid-Stiftung, Anna-Feddersen-Wagner-Fonds
Publisher DOI:https://doi.org/10.1002/hlca.19900730308
Permanent URL: https://doi.org/10.5167/uzh-94223

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