Abstract: We have directly observed twelve ketyl radical intermediates 4～6[ArC(R)OMgX) formed during the reactions of a series of alkyl aryl ketones 1～3(Ar: 2,5-dimethylphenyl (1); 2,5-dimethoxyphenyl(2); 4-t-butyl-2, 5-dimethoxyphenyl (3) with t-butyl magnesium chloride by means of EPRtechnique. The product analysis shows that the major products formed in the reactions of alkyl 2,5-dimethylphenyl ketones l_a-d (R:a, Me; b, Et; c, i-Pr; d, t-Bu) are reduction products 7 and 1,2-addition products 8. The lower polarity of the used solvent and the lower reaction temperature would favour the formation of 7. In accordance with these results, the possible mechanisms for the titled reactions are discussed.

Key words: Alkyl phenyl ketones, Grignard reactions, Ketyl radical anions, Election paramagnetic resonance (EPR)