Reactions of nitrite oxides and nitrite imines with derivatives of 4,5-dihydrooxazole and 4,5-dihydrothiazole and with related compounds

Abstract

2-Phenyl-4, 5-dihydrooxazole 4 gives a cycloadduct 6 when treated with benzonitrile N-oxide; with a 1-oxoalkane- or α-oxoarene-nitrite N-oxide (RCOCNO), an open-chain product, RCO₂CH₂CH₂N(CN)COPh, is obtained. The six-membered-ring analogue of compound 4 undergoes similar reactions. Depending on the nature of the ring substituents, a substituted 4, 5-dihydrooxazole reacts with a C, N-diarylnitrile imine, to give either a cycloadduct, e.g.17, or a 1, 2, 4-triazol-4-ium salt, e.g.19. The product from the reaction of 4, 5-dihydro-2-methylthiazole 1b with a nitrite imine depends upon the nature of the C- and N-substituents in the latter. In all cases it is postulated that a 4-substituted triazolium salt 24 is formed. This may lose thiirane to give a substituted 1, 2, 4-triazole 25, or it may react with a second molecule of the precursor of the nitrite imine, to give a 4-substituted 1, 2, 4-triazolium salt, e.g.27, in which the precursor moiety is incorporated into the C-4 side chain.