Fundamentals and Prospects of Catalysis

Goutam Kumar Patra, Santosh Singh Thakur, Goutam Kumar Patra, Santosh Singh Thakur

• Publisher: Bentham Science Publishers
• Year: 2020
• Print ISBN: 9789811458491
• eBook ISBN: 9789811458514
• Topic: Physical Sciences
• Subtopic: Chemistry
• Index: Chemistry

Catalysis is an area of chemical sciences which has fascinated a wide range of academicians, researchers, chemical technologists and industries throughout the world. Progress in this field has been made owing to the thrust provided by this research and commercial interest. The field of catalysis is interdisciplinary by its nature, as it requires knowledge of organic synthesis, coordination and organometallic chemistry, reaction kinetics and mechanisms, stereochemical concepts and materials science. Fundamentals and Prospects of Catalysis highlights many important topics and sub-disciplines in catalysis by presenting 7 chapters on different but varied catalytic processes. This volume presents the following topics: · Organocatalytic Asymmetric Synthesis of Spiroacetals and Bridged Acetals· Design and Development of Bimetallic Enantioselective Salen Co Catalysts for The Hydrolytic Kinetic Resolution of Terminal Epoxides· Recent Trend in Asymmetric Heterogeneous Flow Catalysis· Ball Milling: A Green Tool in Synthetic Organic Chemistry· Recent Advances in the Developments of Enantioselective Electrophilic Fluorination Reactions via Organocatalysis· Green and Sustainable Biocatalytic Routes to Prepare Biobased Polyols as Precursors for Polyurethanes with Comparison of Existing Biobased Polyol Technology· Polymers Used as Catalysts

Design and Development of Bimetallic Enantioselective Salen Co Catalysts for the Hydrolytic Kinetic Resolution of Terminal Epoxides

Santosh Singh Thakur^{1, *}, Deepak Patel¹, Nidhi Nirmalkar¹, Kiran Thakur², Goutam Kumar Patra¹

¹ Department of Chemistry, Guru Ghasidas Vishwavidyalaya (A Central University) Koni, Bilaspur (Chhattisgarh) 495009-India

² Department of Chemistry, Government Pataleshwar College Masturi, Bilaspur (Chhattisgarh) 495551-India

Abstract

The hydrolytic kinetic resolution of terminal epoxides catalyzed by the monometallic chiral salen Co complex follows the cooperative bimetallic mechanism and second order kinetic dependency on the catalyst. In this mechanism, one metal works as an active Lewis acid center for preferential activation of one enantiomer from a racemic substrate and the second metal center stimulates the incoming nucleophile. Mechanistically, rational design and development of bi- and multimetallic chiral complex centers within the sterically, electronically, and co-ordinatively accessible framework of chiral salen ligand provides improved activity and enantioselectivity relative to their corresponding monometallic catalysts. This chapter provides a survey of bimetallic chiral salen Co complexes used in the hydrolytic kinetic resolution of terminal epoxides to procure valuable chiral intermediates, useful for academic interest and in industrial applications.

Keywords: Asymmetric catalysis, Chiral salen Co complex, Kinetic resolutions, Terminal epoxides.

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^* Corresponding author Santosh Singh Thakur: Department of Chemistry, Guru Ghasidas Vishwavidyalaya (A Central University) Koni, Bilaspur (Chhattisgarh) 495009-India; Tel: [phone] and [phone];
E-mails: [email protected], [email protected]

BACKGROUND AND MOTIVATION

Asymmetric synthesis of chiral compounds, using enantioselective catalysts, plays a crucial role in chemical and pharmaceutical sciences [1]. The industrial need and great academic interest of enantiomerically pure (chiral) compounds in drug

synthesis have motivated, in the past decades, a tremendous growth in catalytic stereoselective synthesis [2^-9]. A number of homogeneous chiral catalysts have already gained wide acceptance in terms of efficiency and selectivity, some of which are even used on an industrial scale, and the chemists involved in the pioneering breakthroughs were recently awarded the Nobel Prize [9]. Asymmetric or chirality (molecular handedness) is considered to be a major element in nearly all naturally occurring or manmade molecules that imparts a key role in science, engineering, and technology. There must be a fine-tuning of chirality in a wide range of chemical, biological and physical functions that are generated through precise stereochemical communications and molecular recognition. Life itself depends on chiral recognition because living systems, particularly enzymes, interact with enantiomers in decisively different manners [8].

Enantiomerically pure compounds can be obtained by one of three strategies [3]:

1. By resolution, either spontaneous (the way Pasteur resolved a tartaric acid salt) or with the aid of an enantiopure reagent. In a classical resolution, two diastereoisomers are formed, and their properties are sufficiently different so they can be separated by a conventional method, such as fractional crystallization or chromatography. The desired enantiomer is then obtained from one of the purified diastereoisomers, while the other is recycled, used for another purpose, or discarded. Classical methods are frequently applied on a large scale [2]. The method based on kinetic resolution is also frequently used.
2. By the use of chiral substrates (“chirons”), mainly of natural origin, which undergo highly stereoselective transformations leading to desired enantiomeric targets [2c].
3. By conversion of prochiral precursor into a chiral products (i.e. asymmetric synthesis). Biochemically, asymmetric synthesis can be performed by enzymes. Chemically, asymmetric synthesis can be performed using chiral auxiliaries, reagent, or catalysts [4].

These three methods have been actively developed for the past few decades. The asymmetric synthesis process should have high (greater than 90%) regio-, diastereo- and enantioselectivities. Furthermore, other important factors in this process are the expense and accessibility of the reagents, the conditions of the reaction (solvent, temperature, and pressure), and the ease of workup and purification. Keeping in mind all these practical considerations, less selective methods are sometimes favored over more selective ones, particularly for large-scale asymmetric synthesis.

Epoxides ar...

Table of contents

• Welcome
• Table of Content
• Title
• BENTHAM SCIENCE PUBLISHERS LTD.
• PREFACE
• List of Contributors
• Organocatalytic Asymmetric Synthesis of Spiroacetals and Bridged Acetals
• Design and Development of Bimetallic Enantioselective Salen Co Catalysts for the Hydrolytic Kinetic Resolution of Terminal Epoxides
• Recent Trends in Asymmetric Heterogeneous Flow Catalysis
• Ball Milling: A Green Tool in Synthetic Organic Chemistry
• Recent Advances in the Developments of Enantioselective Electrophilic Fluorination Reactions via Organocatalysis
• A Green and Sustainable Biocatalytic Routes to Prepare Biobased Polyols as a Precursor For Polyurethanes as Compared to Existing Biobased Polyol Technology
• Polymers Used as Catalyst