CHEMOSELECTIVE N-ALKYLATION OF 2-HYDROXYCARBAZOLE AS A MODEL FOR THE SYNTHESIS OF N-SUBSTITUTED PYRROLE DERIVATIVES CONTAINING ACIDIC FUNCTIONS

2-Hydroxycarbazole (1) was chemoselectively N-alkylated with several alkyl halides 3 by generating the corresponding N,O-dianion using excess sodium hydride in a suitable solvent, under anhydrous conditions. The highest yields (87-96%) of 9-alkyl-2-hydroxycarbazoles 4 and the mildest reaction conditions were reached in THF containing DMF as an additive (2 mol equiv), but other solvents (DMSO, diglyme, DME) or solvent-additive systems (THF-diglyme, THF-DMSO, DME-DMF, diglyme-DMF) are effective.