ULTRASOUND PROMOTED N-ALKYLATION OF PYRROLE USING POTASSIUM SUPEROXIDE AS BASE IN CROWN-ETHER

Ultrasound accelerates the N-alkylation of pyrrole by alkylating reage nts using potassium superoxide as base in the presence of 18-crown-6. A much lower yield of N-alkylated pyrrole was realized in the absence of ultrasound. N-alkylating reagents employed for pyrrole are methyl i odide, ethyl bromide, benzyl bromide, as well as acrylonitrile allyl c yanide and methyl acrylate. In an extension of this work, we have foun d that ultrasound was not necessary for the N-alkylation of indole and alkyl amine, such as diphenyl amine and piperidine with alkyl halides using our reagents. In all cases we observed that the 18-crown-6 cata lyzed N-alkylation reaction gives higher yields of N-alkylated product s than that without crown ether, when potassium superoxide was used as base. These observations are probably due to the potassium-crown comp lex which can be released when the reaction goes to completion. (C) 19 97 Elsevier Science B.V.