Metal-free halogen, chalcogen, or oxocarbenium ion mediated yne-carbonyl or yne-thioxo transformations of a range of N-and O-propargylic compounds have been studied. This investigation has led to the development of a mild, economic, and effective method for the synthesis of functionalized 4H-

SummaryA N-nitroso moiety can be used for the activation of chloropyrimidines toward a nucleophilic substitution reaction with amines. The subsequent treatment of the obtained products with aq H2SO4 can lead to either N-denitrosation to obtain 4,6-pyrimidinediamines or to a Fischer–Hepp type rearrangement to obtain 5-nitroso-4,6-pyrimidinediamines. It was found that the outcome of the reaction strongly depends on the structure of the pyrimidines. Activation of the pyrimidine ring by three groups with a positive mesomeric effect is crucial for the intramolecular nitroso group migration.

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An oxocarbenium ion mediated cyclization of (Z)-1,3-diarylprop-2-yn-1-one O-methyloximes and 3-arylprop-2-yn-1-(2-methoxyphenyl)-1-ones resulted in regioselective formation of functionalized isoxazoles and chromones, respectively. Alkoxy(aryl)methyl group containing compounds were obtained in good and high yields.