Utilizing Native Directing Groups: Mechanistic Understanding of a Direct Arylation Leads to Formation of Tetracyclic Heterocycles via Tandem Intermolecular, Intramolecular C-H Activation

Preparative Scale Applications of C-H Activation in Medicinal Chemistry

C-H activation is an attractive methodology to increase molecular complexity without requiring substrate prefunctionalization. In contrast to well-established cross-coupling methods, C-H activation is less explored on large scales and its use in the production of pharmaceuticals faces substantial hurdles. However, the inherent advantages, such as shorter synthetic routes and simpler starting materials, motivate medicinal chemists and process chemists to overcome these challenges, and exploit C-H activation steps for the synthesis of pharmaceutically relevant compounds. In this review, we will cover examples of drugs/drug candidates where C-H activation has been implemented on a preparative synthetic scale (range between 355 mg and 130 kg). The optimization processes will be described, and each example will be examined in terms of its advantages and disadvantages, providing the reader with an in-depth understanding of the challenges and potential of C-H activation methodologies in the production of pharmaceuticals.

The application of modern reactions in large-scale synthesis

In the past decade, the field of organic synthesis has witnessed tremendous advancements in the areas of photoredox catalysis, electrochemistry, C-H activation, reductive coupling and flow chemistry. While these methods and technologies offer many strategic advantages in streamlining syntheses, their application on the process scale is complicated by several factors. In this Review, we discuss the challenges that arise when these reaction classes and/or flow chemistry technology are taken from a research laboratory operating at the milligram scale to a reactor capable of producing kilograms of product. We discuss how these challenges have been overcome through chemical and engineering solutions. Specifically, this Review will highlight key examples that have led to the production of multi-hundred-gram to kilogram quantities of active pharmaceutical ingredients or their intermediates and will provide insight on the scaling-up process to those developing new technologies and reactions.