A strategic approach for synthesis of benzimidazo[2,1-b]thiazolidinone appended dispirooxindole hybrids via [3 + 2] cycloaddition using fluoro-ethanol as solvent

Abstract

A series of new functionalized analogues of spirooxindole-pyrrolidines have been synthesized by comprising benzimidazo[2,1-b]thiazolidinone heterocyclic fused moiety via 1,3-dipolar cycloaddition reaction strategy under an efficient and eco-comfortable reaction conditions. In the present study a new dipolarophiles alkyl(Z)-2-(3-oxobenzo[4,5]imidazo[2,1-b]thiazol-2(3H)-ylidene)acetate reacts efficiently with non-stabilized 1,3-dipolar component azomethine ylide formed in situ from the reaction of substituted isatins and α-amino acid sarcosine to affording new complex heterocyclic hybrid i.e.,dispiro[benzimidazo[2,1-b]thiazole-2,3′-pyrrolidine-2′,3′'- indoline]-4′-carboxylates. The present benzimidazo[2,1-b]thiazolidinone grafted dispirooxindole core system formed by the creation of two new CC and one CN bonds with multiple stereo centers in one-step operation and reaction proceed with highly regio and exo- selective manner. Further, the present approach is high yielding protocol for synthesis of target cycloadducts in short reaction time using 2,2,2-trifluoroethanol (TFE) as an efficient reaction medium. The regio-/stereochemistry has been concluded by single crystal X-ray diffraction analysis.