The Rh-2(OAc)(4)-catalyzed reaction of 2H-azirine-2-carbaldehydes with dimethyl diazomalonate proceeds via azirinium ylide formation, isomerization to 2-azabuta-1,3-dienes followed by 1,6-pi-electrocyclization to give 2H-1,3-oxazines. According to DFT-calculations ring opening of azirinium ylides should occur stereoselectively to give 2-azadienes with the C=C bond exclusively in the Z configuration. Changing a formyl group for an acetyl group in the azirine leads to a lowering of stereoselectivity and the formation of azadienes with an E configuration of the C=C bond was observed. The reaction of 2-acy1-2-diazoacetates with 2H-azirine-2-carbaldehydes proceeds similarly, but the 2-acetyl-substituted 2H-1,3-oxazines formed are unstable under chromatographic purification and rearrange easily into pyrrole derivatives. (C) 2013 Elsevier Ltd. All rights reserved.
Zavyalov, K. V., Novikov, M. S., Khlebnikov, A. F., & Yufit, D. S. (2013). Rh2(OAc)4-catalyzed reaction of α-diazocarbonyl compounds with 2-carbonyl-substituted 2H-azirines. Tetrahedron, 69(23), 4546-4551. https://doi.org/10.1016/j.tet.2013.04.022