Diversity Oriented Synthesis of 4H-Pyrimido[2,1-b]benzothiazole Derivatives via Biginellis Reaction: A Review

Background: Heterocycles have extended into widespread use for generating large collection of molecules in multi-component reactions. The development of new strategies for fused pyrimidobenzothiazole system has remained a highly attractive but challenging proposition for scientists working all around. Objective: The main objective of this work is to explore the utility of different catalysts as an ecofriendly reaction medium for green Biginellis reaction. Method: A detailed study of Biginellis reactions using various catalysts was done using different research tools. The methods involved reaction of equimolar mixture of benzothiazole, 1,3-diketone and aldehyde as reactants by conventional and greener pathways via Knoevenagal condensation. Results: The present review has several significant advantages for the scientists regarding green synthesis viz. green conditions, short reaction times, high yields, clean reaction conditions, easy isolation of products, simple work-up procedure and mild reaction conditions. Conclusion: Our report gives an overview of the combinatorial libraries for fused benzothiazole entities using metal catalyst, acid catalyst, ionic liquids, phase transfer catalyst, nano catalyst, etc.