Switchable Divergent Synthesis Using Photocatalysis

Abstract

A highly selective and divergent synthesis enables access to various molecules and has garnered broad interest from not only organic chemists but also medicinal chemists and biologists who work with chemical libraries. Since the 20th century, such divergent transformations have been achieved using transition-metal-catalyzed reactions, in which the choice of catalyst or ligand crucially affects the selectivity. Over the past several decades, photocatalysts have attracted a considerable amount of attention because they provide additional ways to control the reaction intermediates and product selectivity via electron or energy transfer. From this perspective, we highlight the recent development of switchable and divergent syntheses using photocatalysts, which are difficult to achieve using classical catalytic transformations.

Solvent-Controlled Switchable Synthesis of gem-Difluoro Compounds from Anhydrides under Photoredox Catalysis

“…Since the latter example represents a three-component intramolecular Ritter type reaction, 65 our curiosity was dragged into the origin of oxygen in the N-acetate moiety. It turned out, that the only source of oxygen would be CDFAA, as the competition experiments using H2O 18 revealed no incorporation of 18 O into the product, endorsing our proposed mechanism. Experiments with both -d2 labelled styrene and d3-MeCN validated the originality of chemo-and regioselectivity (74, 75) (Fig.…”

“…In addition to changing chemistry, the way chemists approach this subject is also constantly evolving. Unconventional, yet valuable concepts have been introduced into the field, including but not limited to late-stage functionalization, 12 atom economy, 13,14 bifunctional reagents, 15 divergent syntheses, [16][17][18][19][20] and multicomponent reactions. 21 Indeed, these strategies allow scientists to access broader chemical space for achieving synthetic endeavors.…”

Switchable photocatalysis for the chemodivergent benzylation of 4-cyanopyridines

“…In this manuscript, we describe the development of switchable photocatalytic methods 7 that allowed us to select at will between the functionalization of 4-cyanopyridines at the C4 or C2 position, leading to products 3 and 4 respectively ( Fig. 1b ).…”

Photochemical Activation of Sulfur Hexafluoride: A Tool for Fluorination and Pentafluorosulfanylation Reactions

“…3 Organic photoredox catalysts overspan a broad variety of molecular scaffolds that can easily be tuned by core modifications, a crucial prerequisite to adjust a particular catalyst system to be most effective in a distinct transformation. 14 While divergent photochemical synthesis has become an important tool in modern photocatalysis, 15 the photoactivation of notoriously inert sulfur hexafluoride (SF6) and switching between its fluorination-and pentafluorosulfanylation reactivity describe recent challenges in photochemistry. In contrast to its smaller fluorinated analogues bearing a dipole moment along the elongated C-X-bond, namely a simple fluorine substituent and the CF3-group, the late-stage introduction of the SF5 group is still a major challenge in synthetic chemistry and its chemistry is highly underdeveloped.…”

“…While divergent photochemical synthesis has become an important tool in modern photocatalysis, 15 the photoactivation of notoriously inert sulfur hexafluoride (SF 6 ) and switching between its fluorination and pentafluorosulfanylation reactivity illustrate recent challenges in photochemistry. In contrast to its smaller fluorinated analogues bearing a dipole moment along the elongated C–X bond, namely a simple fluorine substituent and the CF 3 group, the late-stage introduction of the SF 5 group is still a major challenge and its chemistry is highly underdeveloped.…”