Summary: | A number of novel 6-R-isoxazolo[4,3-<i>b</i>]pyridines were synthesized and their reactions with neutral C-nucleophiles (1,3-dicarbonyl compounds, π-excessive (het)arenes, dienes) were studied. The reaction rate was found to be dependent on the nature of the substituent 6-R. The most reactive 6-nitroisoxazolo[4,3-<i>b</i>]pyridines are able to add C-nucleophiles in the absence of a base under mild conditions. In addition, these compounds readily undergo [4+2]-cycloaddition reactions on aromatic bonds C=C(NO<sub>2</sub>) of the pyridine ring, thus indicating the superelectrophilic nature of 6-NO<sub>2</sub>-isoxazolo[4,3-<i>b</i>]pyridines.
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