Beilstein J. Org. Chem.2014,10, 1896–1905, doi:10.3762/bjoc.10.197
, isoxazoliumN-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 isoxazoliumN-ylides are thermodynamically and kinetically very unstable. According to the calculations and experimental results 2H-1,3
; isoxazoles; isoxazoliumN-ylides; 2-azabuta-1,3-dienes; 2H-1,3-oxazines; Introduction
Isoxazoles are versatile building blocks, which have found extensive use in organic synthesis [1][2][3]. However, reactions of isoxazoles with diazo compounds have scarcely been studied [1][2][3][4][5]. In 2008 Davies and
isoxazoliumN-ylides from N-unsubstituted isoxazole derivatives. The formation of such ylides as reactive intermediates in the reactions of bases on isoxazolium salts was earlier supposed [6][7][8][9]. However, the detection of isoxazoliumN-ylides has never been reported.
Recently, we found an alternative
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Graphical Abstract
Scheme 1:
Mechanistic scheme of the formation of 2H-1,3-oxazine by the reaction of isoxazoles with a diazo co...