This
review showcases various coupling reagents which have been
implemented specifically for large-scale amide synthesis via the condensation
of an acid and amine, while highlighting the benefits and drawbacks
of each reagent on an industrial scale.
Herein we present a review on methods for carbonyl reductions on large scale (≥100 mmol) applied to the synthesis of drug candidates in the pharmaceutical industry. We discuss the most common and reliable methods for the reduction of aldehydes, ketones, carboxylic acids, esters, amides, imides, and acid chlorides. Representative examples illustrate detailed reaction and workup conditions and highlight the advantages and limitations of each reducing agent with special emphasis on safety, cost, and amenability to scale-up.
High-throughput experimentation (HTE) has revolutionized the pharmaceutical industry, most notably allowing for rapid screening of compound libraries against therapeutic targets. The past decade has also witnessed the extension of HTE principles toward the realm of small-molecule process chemistry. Today, most major pharmaceutical companies have created dedicated HTE groups within their process development teams, invested in automation technology to accelerate screening, or both. The industry's commitment to accelerating process development has led to rapid innovations in the HTE space. This review will deliver an overview of the latest best practices currently taking place within our teams in process chemistry by sharing frequently studied transformations, our perspective for the next several years in the field, and manual and automated tools to enable experimentation. A series of case studies are presented to exemplify state-of-the-art workflows developed within our laboratories.
The
synthesis of NiCl(o-tolyl)(TMEDA) (3; TMEDA = tetramethylethylenediamine) and its application in coupling
reactions is described. In combination with a suitable ligand, precatalyst 3 was applied to a wide range of transformations, such as
Suzuki, amination, Kumada, Negishi, Heck, borylation, and reductive
coupling. Yields of products obtained with 3 are equal
or superior to those obtained with common Ni sources such as Ni(cod)2 (1) and NiCl2(dme) (2). Importantly, and unlike 1, complex 3 is stable for months in air as a solid, which eliminates the need
for a glovebox and greatly facilitates the reaction setup. Thus, complex 3 is the first highly versatile Ni source that combines the
broad applicability of 1 with the air stability of 2.
This review describes the practical aspects involved in the implementation of large-scale amidations in process chemistry. Coupling reagent, base, additive, and solvent selections are critically analyzed to highlight their pros and cons. Other important factors to be considered on large scale, such as atom economy, cost, safety, and toxicity, are also examined. These concepts are then showcased through selected examples from the literature for the synthesis of active pharmaceutical ingredients.
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