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MICROWAVE-ASSISTED CHEMISTRY: SYNTHESIS OF AMINES AND HETEROCYCLES VIA CARBON-NITROGEN BOND FORMATION IN AQUEOUS MEDIA
Citation:
VARMA, R. S. AND Y. JU. MICROWAVE-ASSISTED CHEMISTRY: SYNTHESIS OF AMINES AND HETEROCYCLES VIA CARBON-NITROGEN BOND FORMATION IN AQUEOUS MEDIA . Presented at 1nd International Conference on Green & Sustainable Chemistry, Washington, DC, June 20 - 24, 2005.
Impact/Purpose:
To inform the public.
Description:
Improved C-N bond formation under MW influence is demonstrated by a) solventless three-component coupling reaction to generate propargyl amines that uses only Cu (I); b) aqueous N-alkylation of amines by alkyl halides that proceeds expeditiously in the presence of NaOH to deliver tertiary amines; c) synthesis of N-aryl azacycloalkanes, an important class of building blocks in natural products and pharmaceuticals, via an efficient and eco-friendly protocol that involves double N-alkylation of primary amines. The last reaction utilizes readily available aniline derivatives and alkyl dihalides or ditosylates in aqueous potassium carbonate to assemble two C-N bonds in a SN2-like heterocyclization sequence which cannot be fully realized under conventional heating conditions. These MW-assisted "greener" transformations circumvent the need for multi-step processes that use expensive metal catalysts, afford excellent yields, and accommodate reactive functional groups because of mild reaction conditions. Additional advantages include considerably reduced reaction times, and minimization or elimination of byproducts.