Organic Communications

A one-pot, ionic-liquid-mediated synthesis has been developed for novel thiazolidine-4-ones containing a pyrazole and thiazole hybrid. This was achieved using a three-component reaction of 2-amino-thiazole, pyrazole-3-aldehyde, and mercaptoacetic acid in [bmim][PF6]. The whole procedure is robust and straightforward. By employing this protocol, a series of novel thiazolidine-4-ones containing pyrazole and thiazole hybrids were prepared in good yield (56-88%) and their preliminary cyclooxygenase activities were also studied and reported. The compounds 3h and 3k show the top-tier selective index for cyclooxygenase enzyme, in comparable with celecoxib as a standard.

We have thoroughly investigated the C-benzylation of pyrrole (1) using different second and third generation ionic liquids (ILs). The pyrrole C-benzylation is achieved with benzyl halides, mesylate, and tosylate selectively at C2 position in good yield. Moreover, minimal byproducts under relatively mild conditions in hexaethylene glycol substituted imidazolium based ILs (hexaEGILs) have been observed. 2-Benzyl pyrrole (3) was synthesized in high yield from pyrrole (1) and benzyl bromide (2a) in the presence of [hexaEGmim][OMs] and [dihexaEGim][OMs] as two different tailor-made ILs as catalysts (10 mol%) in MeCN at 80 oC within an hour.