Anodic Methoxylation of Isatin

Isatin , w hich is the su b stra te fo r industria l syn­ thesis o f the m ost p o p u la r fabric dye, the indigo, has been sub ject to elec tro ly tic red u c tio n u n d e r a varie ty of experim en ta l cond itions [1,2]. P o laro ­ graphie b ehav io r o f isatin and a varie ty of isatin derivatives has been described in m any of papers [3 -6 ] , H ow ever, m ost o f those rep o rts w ere d e ­ vo ted to ca thod ic phen o m en a . H ere we re p o rt the e lec trochem ica l synthesis o f an unusual indo le ring system fo rm ed anodically during the electro lysis o f m eth an o lic isa tine so lu ­ tions. This p ro ced u re resu lts in the fo rm a tio n of 3a ,7a-d ihydro-3a,7a-d im ethoxyisatin , a stab le com pound w ith sa tu ra te d doub le b o n d betw een tw o p a r tn e r rings of the indo le nucleus.