An efficient and highly selective approach for the construction of novel dispiro heterocycles in guanidine-based task-specific [TMG][Ac] ionic liquid

A simple, efficient and highly selective one-pot approach for the synthesis of biologically important novel dispiro heterocycles assembling three pharmacophoric moieties such as piperidinone, 1,3-indanedione, and pyrrolidine in a single molecular framework by means of three-component reaction between ninhydrin, sarcosine, and 1-benzyl/methyl-3,5-bis[(E)-arylidene]-piperidin-4-one is reported in task-specific 1,1,3,3-tetramethylguanidine acetate [TMG][Ac] ionic liquid as a environmentally benign solvent in excellent yields without using any catalyst. The TMG-based ionic liquid could be recovered and used at least four times without considerable reduction in its activity and selectivity. Good functional group tolerance and broad scope of usable substrates are other prominent features of the present methodology with high degree of chemo-, regio-, and stereoselectivity. The structure and relative stereochemistry of final products were established by single crystal X-ray structure and spectroscopic techniques.