Synthesis of Biologically Active Heterocycles via a Domino Sequence Involving an SN2/Thorpe–Ziegler Reaction Step

This review highlights methods for the synthesis of five- and six-membered heterocycles and their annulated analogues. These methods are based on anionic domino reactions that have a common step: an SN2/Thorpe–Ziegler reaction. In addition, data on the biological activity of these heterocycles are summarized.

1 Introduction

2 Synthesis of Thiophenes, Pyrroles, Furans and Other Heterocycles

2.1 Synthesis of 3-Aminothiophenes

2.2 Synthesis of 3-Aminopyrroles

2.3 Synthesis of 3-Aminofurans

3 Synthesis of Bicyclic Heterocyclic Systems

3.1 Thiophenes, Pyrroles and Furans Fused with Five-Membered Heterocycles

3.2 Thiophenes, Pyrroles and Furans Fused with Six-Membered Heterocycles

4 Synthesis of Heterocyclic Compounds Using Three-Step Domino Reactions

5 Synthesis of Heterocyclic Compounds Based on a Combination of Two Domino Reactions

6 Miscellaneous

7 Conclusion

One-pot Synthesis of Pyrano[2,3-c]pyrazole Derivatives via Multicomponent Reactions (MCRs) and their Applications in Medicinal Chemistry

Background:

Many pyrano[2,3-c]pyrazole derivatives display diverse biological activities and some of them are known as anticancer, analgesic, anticonvulsant, antimicrobial, anti-inflammatory, and anti-malarial agents. In recent years, easy convergent, multicomponent reactions (MCRs) have been adopted to make highly functionalizedpyrano[2,3-c]pyrazole derivatives of biological interest. The synthesis of 1,4-dihydropyrano[2,3-c]pyrazole (1,4-DHPP, 2), 2,4-dihydropyrano[2,3-c]pyrazole (2,4-DHPP, 3), 4-hydroxypyrano[2,3-c]pyrazole (4-HPP, 4) derivatives, 1,4,4-substitied pyranopyrazole (SPP, 5) were reported via two-, three-, four- and five-component reactions (MCRs).

Methods:

This review article compiles the preparation of pyrano[2,3-c]pyrazole derivatives, and it highlights the applications of various pyrano[2,3-c]pyrazole derivatives in medicinal chemistry.

Results:

Varieties of pyrano[2,3-c]pyrazole derivatives were achieved via “One-pot” multicomponent reactions (MCRs). Different reaction conditions in the presence of a catalyst or without catalysts were adapted to prepare the pyrano[2,3-c]pyrazole derivatives.

Conclusion:

Biologically active pyrano[2,3-c]pyrazole derivatives were prepared and used in drug discovery research.

Unconventional approaches for the introduction of sulfur-based functional groups

Organosulfur compounds have a pivotal role in the functionalities of many natural products, pharmaceuticals and organic materials. For these reasons, the search for new methodologies for the formation of carbon-sulfur bonds has been the object of intensive work for organic chemists. However, the proposed strategies suffer from various drawbacks, such as volatility, toxicity, and instability of the sulfur sources or the use of VOC solvents. In this review, we summarise the recent protocols which have the goal of obtaining sulfones, thioethers, thiazines, thiazepines and sulfonamides in an unconventional and/or sustainable way. The use of starting materials less invasive and toxic with respect to the traditional reagents, alternative solvents such as water, ionic liquids or deep eutectic solvents, the exploitation of ultrasound and electrochemistry, increasing the efficiency of the process, are reported. Moreover, representative reaction mechanisms are also discussed.