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Nonconcerted Cycloaddition of 2H-Azirines to Acylketenes: A Route to N-Bridgehead Heterocycles

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posted on 2016-02-22, 14:30 authored by Alexander F. Khlebnikov, Mikhail S. Novikov, Viktoriia V. Pakalnis, Dmitry S. Yufit
Reactions of acylketenes, generated from diazo diketones, with 2-unsubstituted and 2-monosubstituted 3-aryl-2H-azirines lead to 1:1 or 2:1 adducts, which are derivatives of 5-oxa-1-azabicyclo[4.1.0]­hept-3-ene or 5,7-dioxa-1-azabicyclo[4.4.1]­undeca-3,8-diene. According to DFT B3LYP/6-31G­(d) computations, the formation of (4+2)-monoadducts proceeds via a stepwise non-pericyclic mechanism. Reaction with methanol transforms quantitatively both 1:1 and 2:1 adducts into 1,4-oxazepine derivatives.

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