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.
Two protocols for the transamidation of primary amides with primary and secondary amines, forming secondary and tertiary amides, respectively, are described. Both processes employ N,N-dialkylformamide dimethyl acetals for primary amide activation, producing N'-acyl-N,N-dialkylformamidines as intermediates, as widely documented in the literature. Although the latter intermediates react irreversibly with amines by amidinyl transfer, we show that in the presence of certain Lewis acid additives efficient acyl transfer occurs, providing new and useful methods for amide exchange. In one protocol for transamidation, the N'-acyl-N,N-dialkylformamidine intermediates are purified by flash-column chromatography and the purified intermediates are then treated with an amine (typically, 2.5 equiv) in the presence of scandium triflate (10 mol %) in ether to form in high yields the products of transamidation. In a second procedure, N'-acyl-N,N-dialkylformamidines are generated in situ and, without isolation, are subjected to transamidation in the presence of zirconium chloride (0.5 equiv) and an amine (typically 2 equiv). A variety of different primary amides and amines are found to undergo efficient transamidation using the methods described.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.