1433997-82-0Relevant academic research and scientific papers
Isoxazolium N-ylides and 1-oxa-5-azahexa-1,3,5-trienes on the way from isoxazoles to 2H-1,3-oxazines
Khlebnikov, Alexander F.,Novikov, Mikhail S.,Gorbunova, Yelizaveta G.,Galenko, Ekaterina E.,Mikhailov, Kirill I.,Pakalnis, Viktoriia V.,Avdontceva, Margarita S.
, p. 1896 - 1905 (2014)
Theoretical and experimental studies of the reaction of isoxazoles with diazo compounds show that the formation of 2H-1,3- oxazines proceeds via the formation of (3Z)-1-oxa-5-azahexa-1,3,5-trienes which undergo a 6p-cyclization. The stationary points corresponding to the probable reaction intermediates, isoxazolium N-ylides, were located by DFT calculations at the B3LYP/6- 31G(d) level only for derivatives without a substituent in position 3 of the isoxazole ring. These isoxazolium N-ylides are thermodynamically and kinetically very unstable. According to the calculations and experimental results 2H-1,3-oxazines are usually more thermodynamically stable than the corresponding open-chain isomers, (3Z)-1-oxa-5-azahexa-1,3,5-trienes. The exception are oxaazahexatrienes derived from 5-alkoxyisoxazoles, which are thermodynamically more stable than the corresponding 2H-1,3- oxazines. Therefore, the reaction of diazo esters with 5-alkoxyisoxazoles is a good approach to 1,4-di(alkoxycarbonyl)-2- azabuta-1,3-dienes. The reaction conditions for the preparation of aryl- and halogen-substituted 2H-1,3-oxazines and 1,4-di(alkoxycarbonyl)- 2-azabuta-1,3-dienes from isoxazoles were investigated.
Rh2(OAc)4-catalyzed reaction of α-diazocarbonyl compounds with 2-carbonyl-substituted 2H-azirines
Zavyalov, Kirill V.,Novikov, Mikail S.,Khlebnikov, Alexander F.,Yufit, Dmitry S.
, p. 4546 - 4551 (2013/06/26)
The Rh2(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-π-electrocyclization to give 2H-1,3-oxazines. Ac
