Catalyst-Free Three-Component Tandem Green Synthesis of Pyrano[2,3-d]Pyrimidine Scaffolds in Ethylene Glycol (E-G) as a Recyclable Reaction Medium

Importance of Hybrid Catalysts toward the Synthesis of 5H-Pyrano[2,3-d]pyrimidine-2-ones/2,4-diones (Thiones)

The pyranopyrimidine core is a key precursor for medicinal and pharmaceutical industries due to its broader synthetic applications as well as its bioavailability. Among its four possible isomers, we found that 5H-pyrano[2,3-d]pyrimidine scaffolds have a wide range of applicability, and in recent years, they have been intensively investigated, but the development of the main core is found to be more challenging due to its structural existence. In this review article, we cover all of the synthetic pathways that are employed for the development of substituted 4-aryl-octahydropyrano/hexahydrofuro[2,3-d]pyrimidin-2-one (thiones) and 5-aryl-substituted pyrano[2,3-d]pyrimidindione (2-thiones) derivatives through a one-pot multicomponent reaction using diversified hybrid catalysts such as organocatalysts, metal catalysts, ionic liquid catalysts, nanocatalysts, green solvents, catalyst-/solvent-free conditions, and miscellaneous catalysts as well as the mechanism and recyclability of the catalysts. This review mainly focuses on the application of hybrid catalysts (from 1992 to 2022) for the synthesis of 5H-pyrano[2,3-d]pyrimidine scaffolds. This review will definitely attract the world's leading researchers to utilize broader catalytic applications for the development of lead molecules.

Recent advancements in the multicomponent synthesis of heterocycles integrated with a pyrano[2,3-d]pyrimidine core

Heterocyclic compounds incorporated with a pyranopyrimidine skeleton have received substantial consideration owing to their privileged, and intelligible biodiversity. Accordingly, this review highlights the multicomponent synthetic routes adopted to prepare heterocyclic compounds incorporated with the pyrano[2,3-d]pyrimidine skeleton in the preceding two years. The different sections comprise the synthesis of bicyclic, tricyclic, polycyclic, and spirocyclic systems along with the estimation of the probable mechanistic routes for the reaction pathways. Commonly, the pyran ring closure was the major idea of most studies, and the mechanistic pathways of these reactions involved Knoevenagel condensation, Michael addition, and intramolecular cyclocondensation. Besides, the significant biological potency of the compounds recently synthesized from multicomponent reactions is deliberated.

The present review highlighted the recent developments of the multicomponent synthesis of heterocyclic compounds with pyrano[2,3-d]pyrimidine skeleton applying the diverse strategies.