Pyridinolysis of a-Chloroacetanilides in dimethyl sulfoxide

초록

Kinetic studies of the reactions of α-Chloroacetanilides (YC6H4NRC(=O)CH2Cl; R=H and CH3) with pyridines (NC6H4X) were carried out in dimethyl sulfoxide at 95℃. The selectivity parameters bX, rX, rY and rXY values are small in this reaction system. For R=CH3, βX =0.29~0.32, ρX=-1.48~-1.61, ρY=0.23~0.40 and ρXY=-0.13. The activation parameters for the above reaction system (R=CH3) are DH¹=9~15 kcal mol-1 and -DS¹=31~47 cal mol-1K-1. The rates were faster for R=H than R=CH3 under the same reaction condition. Based on these results, a bridged type TS is feasible for the present reaction system which safely ruled out the development of negative charge on Ca delocalizes toward the carbonyl group (nC ？ p*C=O interaction). Lee and coworkers have recently reported the nucleophilic substitution reactions of a-chloroacetanilides with benzylamines in dimethyl sulfoxide as stepwise with tetrahedral intermediate, T± and bridged type TS.