Studies on the racemization of optically active ortho-tert-butyl-N,N-diacylanilines 1c-e including the electronic effects of their acyl groups are described. The racemization of 1c bearing a 4-methoxyphenyl substituent occurred faster while that of le bearing a 4-trifluoromethylphenyl substituent was slower, compared with that of 1d bearing a phenyl group. Thus, the rate of racemization depends on the electronic effects of the acyl groups in addition to steric effects of the acyl groups in la, b as reported previously (K. Kondo, H. Fujita, T. Suzuki and Y. Murakami, Tetrahedron Lett. 1999, 40, 5577-5580).