Dipolar Cycloaddition on the Transient Thiophene Sulfone: Isoxazoline and Isoxazolidine Derivatives

Article abstract of DOI:10.1021/jo00330a024

From the 3,4-dibromotetrahydrothiophene 1,1-dioxide under basic conditions and in the presence of 1,3 dipoles such as N,α-diphenylnitrone and/or mesitonitrile oxide are obtained isoxazoline and isoxazolidine derivatives of the transient thiophene sulfone as mono- or diadducts.Kinetic studies of the nitrone cycloaddition show a consecutive kinetic scheme of the addition and show that the monoadduct formation is 1E3 faster than that of the diadduct.NMR analysis (1H and 13C) and crystallographic studies show the formation of the adduct where the regioselectivity corresponds to the oxygen atom of the dipoles bonded to the carbon atom β to the sulfone group, the "endo" nature of the addition, and the anti situation of the two rings in the diadduct.