REMARKABLE DEPENDENCE OF THE REGIOSELECTIVITY OF FREE-RADICAL ADDITIONS TO 3-CINNAMOYLOXAZOLIDIN-2-ONES ON THE STABILITY OF THE INTERMEDIATE ADDUCT-RADICAL, ELECTROPHILICITY OF THE ADDING RADICALS AND THE CONDITIONS FOR THEIR GENERATION

Electrophilic (CCl3) and nucleophilic radicals (Pr-i) are found to add at 80 degrees C to the C=C bond of 3-(E)-cinnamoyl-4-phenyloxazolidin -2-one 1a and 3-(E)-cinnamoyl-4-benzyloxazolidin-2-one 1b predominantl y at the alpha-position of the bond. While for the CCl3 radical no pro duct of beta-addition has been found, for the Pr-i radical such a path constitutes up to 40% of the whole process at 80 degrees C. An interp lay between the stability of the intermediate adduct radicals and the electrophilicity or nucleophilicity of the radicals undergoing additio n are invoked to rationalize the observation. At a low temperature (-2 3 degrees C)beta-addition of the Pr-i radical becomes the dominant pro cess (up to 75%).