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Unique Versatility of Ionic Liquids as Clean Decarboxylation Catalyst Cum Solvent: A Metal‐ and Quinoline‐Free Paradigm towards Synthesis of Indoles, Styrenes, Stilbenes and Arene Derivatives under Microwave Irradiation in Aqueous Conditions
Author(s) -
Sharma Abhishek,
Kumar Rakesh,
Sharma Naina,
Kumar Vinod,
Sinha Arun K.
Publication year - 2008
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200800537
Subject(s) - chemistry , decarboxylation , ionic liquid , quinoline , catalysis , organic chemistry , reagent , aryl , green chemistry , aqueous solution , combinatorial chemistry , alkyl
Abstract Ionic liquids have been found to provide a new platform for metal‐ and quinoline‐free decarboxylation of various N ‐heteroaryl and aryl carboxylic acids under microwave irradiation in aqueous condition. The method was found to possess a wide substrate scope towards the synthesis of various pharmacologically and industrially important aromatic compounds including indoles, styrenes, stilbenes, and nitro‐ or hydroxyarene derivatives. The decarboxylation of indole and α‐phenylcinnamic acids proceeded well without addition of any catalyst in neat 1‐hexyl‐3‐methylimidazolium bromide ([hmim]Br) and 1‐methylimidazolium p ‐toluenesulfonic acid ([Hmim]PTSA), respectively, while addition of a mild base like aqueous sodium hydrogen carbonate (NaHCO 3 ) to [hmim]Br further improved the decarboxylation of hydroxylated cinnamic and aromatic acid substrates. The developed methodology not only precludes the usage of toxic metal/quinoline and harsh organic bases but also offers several inherent benefits like recyclability of reagent system, reduction in waste and hazards, short reaction time besides ease of product recovery.