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A Review of Recent Advances in the Green Synthesis of Azole- and Pyran-based Fused Heterocycles Using MCRs and Sustainable Catalysts



Nitrogen, oxygen and sulfur-containing fused heterocycles are of great importance
because of their exciting and diverse biological activities. The construction of the carbonnitrogen
and carbon-oxygen through a multicomponent reaction approach by using ecofriendly
reusable heterogeneous catalysts are of significant importance as it opens avenues for
the introduction of nitrogen and oxygen in organic molecules. Thus, green methodologies
have gained particular significance in this field; today, green chemistry is considered a tool
for introducing sustainable concepts at the fundamental level. This review emphasizes and
discusses the current progress on the applications of eco-friendly, recyclable heterogeneous
catalysts for the synthesis of different heterocyclic fused systems and their green protocols.
We paid particular attention to the specific integration of carbon-nitrogen, and carbon-oxygen
bond-forming fused heterocycles by a one-pot approach by evaluating the literature between 2012 and the middle of
2020. The efficiency of the catalyst is assessed in terms of reaction time, yield and possible reusability. The MCR and
heterogeneous catalyst strategies have demonstrated broader scope, economical and viability for the green and sustainable
processes in the field of synthetic organic chemistry.
