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Dipolare (1:1)-Addukte aus der Reaktion von 3-Amino-2H-azirinen mit 1,3,4-Oxadiazol- und 1,3,4-Thiadiazol-2(3H)-onen


Ametamey, Simon M; Vincent, Beverly R; Heimgartner, Heinz (1990). Dipolare (1:1)-Addukte aus der Reaktion von 3-Amino-2H-azirinen mit 1,3,4-Oxadiazol- und 1,3,4-Thiadiazol-2(3H)-onen. Helvetica Chimica Acta, 73(2):492-507.

Abstract

3-Amino-2H-azirines 1 react with 5-(trifluoromethyl)-1,3,4-oxadiazol-2(3H)-one (2) as well as with different 5-substituted 1,3,4-thiadiazol-2(3H)-ones(5a-e) in 2-propanol at room temperature to give dipolar 1:1 adducts of type 3 and 6, respectively, in reasonable-to-good yields (Schemes 3 and 6, Tab. 1 and 2). The structure of two of these dipolar adducts, 6a and 6e, which are formally donor-acceptor-stabilized azomethine imines, have been elucidated by X-ray crystallography (Figs. 1-4). In the reaction of 2 and sterically crowded 3-amino-2H-azirines 1c-e with a 2-propyl and 2-propenyl substituent, respectively, at C(2), a 4.5-dihydro-1,2,4-triazin-3(2H)-one of type 4 is formed as minor product (Scheme 3 and Table 1). Independent syntheses of these products proved the structure of 4. Several reaction mechanisms for the formation of compounds 3 and 4 are discussed, the most likely ones are described in Scheme 4: reaction of 2 as an NH-acidic compound leads, via a bicyclic zwitterion of type A, to 3 as well as to 4. In the latter reaction, a ring-expanded intermediate B is most probable.

Abstract

3-Amino-2H-azirines 1 react with 5-(trifluoromethyl)-1,3,4-oxadiazol-2(3H)-one (2) as well as with different 5-substituted 1,3,4-thiadiazol-2(3H)-ones(5a-e) in 2-propanol at room temperature to give dipolar 1:1 adducts of type 3 and 6, respectively, in reasonable-to-good yields (Schemes 3 and 6, Tab. 1 and 2). The structure of two of these dipolar adducts, 6a and 6e, which are formally donor-acceptor-stabilized azomethine imines, have been elucidated by X-ray crystallography (Figs. 1-4). In the reaction of 2 and sterically crowded 3-amino-2H-azirines 1c-e with a 2-propyl and 2-propenyl substituent, respectively, at C(2), a 4.5-dihydro-1,2,4-triazin-3(2H)-one of type 4 is formed as minor product (Scheme 3 and Table 1). Independent syntheses of these products proved the structure of 4. Several reaction mechanisms for the formation of compounds 3 and 4 are discussed, the most likely ones are described in Scheme 4: reaction of 2 as an NH-acidic compound leads, via a bicyclic zwitterion of type A, to 3 as well as to 4. In the latter reaction, a ring-expanded intermediate B is most probable.

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Other titles:Dipolar 1:1 Adducts from the Reaction of 3-Amino-2H-azirines with 1,3,4-Oxadiazol- and 1,3,4-Thiadiazol-2(3H)-ones
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 15:36
Last Modified:08 Dec 2017 04:51
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.19900730230

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