Scheme 1.
Synthesis of isatin derivatives 4a–h and their 3’-oximes 5a–f. (i) Na2CO3, MeOH, rt, 6–24 h (73% (4a), 81% (4b), 93% (4c), 88% (4d), 91% (4e), 86% (4f), 59% (4g)); (ii) AcONa, AcOH, 110 °C, 24 h (54% (4h)); (iii) NH2OH•HCl, pyridine, 120 °C, 2 h (71% (5a), 59% (5b), 65% (5c), 73% (5d), 69% (5e), 36% (5f)).