Stereoselective Synthesis of Hagen's Gland Lactones by Employing Vinylogous Mukaiyama Type Reaction

Graphene Oxide Catalyzed Synthesis of Fused Chromeno Spiro Pyrrolidine Oxindoles via Tandem Decarboxylation and 1,3-Dipolar Cycloaddition

A short and efficient multicomponent sequence for synthesizing fused novel polyheterocyclic chromeno spiro-pyrrolidine oxindoles via 1,3-dipolar cycloaddition reaction mediated by reactive azomethine ylides catalyzed by the Graphene Oxide (GO) is reported herein. This approach was utilized for synthesizing fused polyheterocyclic spiro-pyrrolothiazole and spiro-pyrrole oxindoles with yields ranging from good to excellent. A heterogeneous GO catalyst with an ultra-low catalytic loading of 0.05 wt% could proficiently catalyze the reaction without the formation of any side products and can also be visualized by the formation of solid mass in the reaction flask. The methodology is green in nature and the products were isolated by simple filtration without the use of any chromatographic techniques.

Recent approaches in the organocatalytic synthesis of pyrroles

Organocatalysis has emerged as one of the most important tools for the synthesis of diverse structural scaffolds, and has become one of the most important hot topics of current research. Construction of the pyrrole ring has gained much attention from the last few decades due to its remarkable biological activities, pharmaceutical application, intermediate in the synthesis of many natural products, and material science application. With access to these 5-membered aza heterocycles, organocatalytic approaches have provided a new alternative from the perspective of synthetic efficiency, as well as from the green chemistry point of view, and a vast array of synthetic procedures has been developed. Enlightened by the significance of this growing research area, we aim to describe the recent organocatalytic approaches developed for the construction of pyrroles, and organized them based on substrates employed.

Advances in Total Synthesis of Some 2,3,5-Trisubstituted Tetrahydrofuran Natural Products

2,3,5-Trisubstituted tetrahydrofuran moiety is ubiquitous in natural products. These have served as appealing candidates for total synthesis due to their varied bio- and pharmaceutical activities. This tutorial review delineates the ingenious efforts by many researchers in the total synthesis of selected natural products based on a common 2,3,5-trisubstituted tetrahydrofuran core structure. Many of the syntheses display nuanced interplay between new methods and the ingenuity of planned strategies achieved through catalysis or cascade chemistry. In some cases, the chiron approach has come quite handy, wherein the structural features and the stereochemistry in select molecules could map well with naturally available starting materials. This compilation also aims to enhance the diversity space based on these natural products and further interest in sustainable total synthesis.

Highly efficient catalyst-free domino conjugate addition, decarboxylation and esterification/amidation of coumarin carboxylic acid/esters with pyrazolones: a green chemistry approach

Tandem conjugate addition, decarboxylation and esterification/amidation of coumarin 3-carboxylic acid derivatives with pyrazolones have been developed.