Efficient multi-component synthesis of 1,4-benzodiazepine-3,5-diones: a Petasis-based approach

Catalyst-free Synthesis of Aminomethylphenol Derivatives in Cyclopentyl Methyl Ether via Petasis Borono-Mannich Reaction

OBJECTIVE

Aminomethylphenol molecules have wider applications in pharmaceuticals, agrochemicals, plant protection and promising functional materials. The development of an efficient and practical method to prepare this class of compound is highly desirable from both environmental and economical points of view.

MATERIALS AND METHODS

In order to establish an effective synthetic method for preparing aminomethylphenol derivatives, the Petasis borono-Mannich reaction of salicylaldehyde, phenylboronic acid and 1,2,3,4- tetrahydroisoquinoline was selected as a model reaction. A variety of reaction conditions are investigated, including solvent and temperature. The generality and limitation of the established method were also evaluated.

RESULTS AND DISCUSSION

It was found that model reaction can be carried out in cyclopentyl methyl ether at 80 oC under catalyst-free conditions. This protocol, with broad substrate applicability, the reaction of various arylboronic acid, secondary amine and salicylaldehyde proceeded smoothly under optimal reaction conditions to afford various aminomethylphenol derivatives in high yields. A practical, scalable, and high-yielding synthesis of aminomethylphenol derivatives was successfully accomplished.

CONCLUSION

A catalyst-free practical method for the synthesis of minomethylphenol derivatives based on Petasis borono-Mannich (PBM) reaction of various arylboronic acid, secondary amine and salicylaldehyde in cyclopentyl methyl ether has been developed. The salient features of this protocol are avoidance of any additive/catalyst and toxic organic solvents, use of cyclopentyl methyl ether as the reaction medium, clean reaction profiles, easy operation, and high to excellent yield.

Multicomponent reactions as a potent tool for the synthesis of benzodiazepines

Benzodiazepines (BZDs), a diverse class of benzofused seven-membered N-heterocycles, display essential pharmacological properties and play vital roles in some biochemical processes. They have mainly been prescribed as potential therapeutic agents, which interestingly represent various biological activities such as anticancer, anxiolytic, antipsychotic, anticonvulsant, antituberculosis, muscle relaxant, and antimicrobial activities. The extensive biological activities of BZDs in various fields have encouraged medicinal chemists to discover and design novel BZD-based scaffolds as potential therapeutic candidates with the favorite biological activity through an efficient protocol. Although certainly valuable and important, conventional synthetic routes to these bicyclic benzene compounds contain methodologies often requiring multistep procedures, which suffer from waste materials generation and lack of sustainability. By contrast, multicomponent reactions (MCRs) have recently advanced as a green synthetic strategy for synthesizing BZDs with the desired scope. In this regard, MCRs, especially Ugi and Ugi-type reactions, efficiently and conveniently supply various complex synthons, which can easily be converted to the BZDs via suitable post-transformations. Also, MCRs, especially Mannich-type reactions, provide speedy and economic approaches for the one-pot and one-step synthesis of BZDs. As a result, various functionalized-BZDs have been achieved by developing mild, efficient, and high-yielding MCR protocols. This review covers all aspects of the synthesis of BZDs with a particular focus on the MCRs as well as the mechanism chemistry of synthetic protocols. The present manuscript opens a new avenue for organic, medicinal, and industrial chemists to design safe, environmentally benign, and economical methods for the synthesis of new and known BZDs.

The Application of 4Å Molecular Sieves in Organic Chemical Syntheses: An Overview

In the last two decades, considerable attention has been devoted to the use of 4Å molecular sieves (MS 4A) in organic chemical syntheses. Initially, they were applied as drying agents in order to dry gases, solvents and liquid reagents. Nowadays, there is a growing tendency to apply MS 4A as an additive, catalyst, co-catalyst or catalyst support in organic reactions. In this review, we aim to summarize the recent examples of organic syntheses promoted by MS 4A from 1997 to 2020. We hope to provide the reader with an overview of the potential of MS 4A in the field of organic synthesis.

1 Introduction

2 Application as an Additive

3 Application as Catalyst

4 Application as Co-catalyst

5 Application as Support

6 Conclusion

Reactivity and Synthetic Applications of Multicomponent Petasis Reactions

The Petasis boron-Mannich reaction, simply referred to as the Petasis reaction, is a powerful multicomponent coupling reaction of a boronic acid, an amine, and a carbonyl derivative. Highly functionalized amines with multiple stereogenic centers can be efficiently accessed via the Petasis reaction with high levels of both diastereoselectivity and enantioselectivity. By drawing attention to examples reported in the past 8 years, this Review demonstrates the breadth of the reactivity and synthetic applications of Petasis reactions in several frontiers: the expansion of the substrate scope in the classic three-component process; nonclassic Petasis reactions with additional components; Petasis-type reactions with noncanonical substrates, mechanism, and products; new asymmetric versions assisted by chiral catalysts; combinations with a secondary or tertiary transformation in a cascade- or sequence-specific manner to access structurally complex, natural-product-like heterocycles; and the synthesis of polyhydroxy alkaloids and biologically interesting molecules.

A simple one-pot synthesis of 2,4-diaryl- 9H-pyrido[2,3-b]indoles under solvent-free conditions

A novel, simple, one-pot synthesis of 2,4-diaryl-9

Synthesis and Evaluation of Novel Quinazolinone-1,2,3-Triazoles as Inhibitors of Lipoxygenase

This work reports the successful synthesis of quinazolinones carrying triazole derivatives with potent lipoxygenase inhibitory activities. This protocol involves sequential reactions affording novel products in high yields without the need for a tedious work-up procedure.

Three-component one-pot synthesis of dihydrochromeno[4,3-b]pyrazolo[4,3-e]pyridines

A series of dihydrochromeno[4,3-

Copper supported β-cyclodextrin grafted magnetic nanoparticles as an efficient recyclable catalyst for one-pot synthesis of 1-benzyl-1H-1,2,3-triazoldibenzodiazepinone derivatives via click reaction

Cu immobilized into β-cyclodextrin covalently attached to magnetic nanoparticles (denoted as [Cu@β-CD@SPIONs]) is reported as an efficient and recoverable catalyst for “click” and multicomponent reactions.

Rapid synthesis of alkylaminophenols via the Petasis borono–Mannich reaction using protonated trititanate nanotubes as robust solid–acid catalysts

The Petasis borono–Mannich reaction was applied to the synthesis of alkylaminophenols from o-hydroxybenzaldehydes, secondary amines and boronic acids in the presence of H₂Ti₃O₇ nanotubes as reusable solid–acid catalysts.