Facile synthetic route to isoxazoles from β-sulfinyl- and β-sulfonyl-cyclohexenones via regioselective nitrile oxide cycloaddition and in-situ elimination

A facile synthetic route to isoxazole is reported. Through examination of the reaction of stable nitrile oxides, β-substituted cyclohexenones, particularly sulfinyl and sulfonyl derivatives, show excellent regioselectivity in the 1,3-dipolar cycloaddition, forming isoxazoline cycloadducts, which undergo in-situ 1,2-elimination either with the assistance of a base (for the β-sulfonyl derivative) or without the need for a base (for the β-sulfinyl derivative), enabling a direct, high-yield access to isoxazoles.