Proline Tetrazole and Related Catalysts

A mechanistic investigation of this chemistry using density functional theory calculations [176] and reactions in ionic Hquids as solvents have also been reported [177]. 

Very similar results have also been reported with the use of sulfur ylides as donor molecules [179]. With regard to the asymmetric Biginelli reaction [180] and mulhcomponent coupling reachons [181] using 30 or its analog as a catalyst, only references are given here. 

The utility of ionic liquid conjugate catalysts such as 32 and 33 can be ascribed to their recyclability [195-199]. On the other hand, triazole-based catalysts such as 34 and 35 are readily accessible via Huisgen 1,3-dipolar cycloadditions, so-called click reactions, from azidomethyl-pyrrolidine and acetylenic precursors, and hence make it possible to design new immobilized catalysts [200-207]. 

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