Academic literature on the topic 'Asymmetric photocatalysis'

Asymmetric transformation of radicals has always been recognized as a highly challenging issue, compared with the well-developed enantioinduction methods in traditional polar/ionic chemistry. Enantioselective radical polar crossover (RPC) reactions have recently emerged as valuable and powerful tools to assemble molecular complexity that would be impossible using either a radical or polar approach alone. This chapter summarizes the recent and synthetically important stereoselective RPC transformations by merging photoredox catalysis.

AbstractC—H bond functionalization catalyzed by high-valent-cobalt species with the aid of bidentate chelation has come a long way since the pioneering report by Daugulis almost a decade ago. Further study of the reaction mechanisms revealed that stoichiometric amounts of metal salts could be replaced with photocatalysts or electricity as one-electron oxidants, and approaches based on these strategies can be considered more environmentally friendly than the initially developed catalytic systems. Systematic investigations have led to a better understanding of the coordination environment of the in-situ-formed cobaltacycle, and this has led to the development of external chiral ligands for cobalt-catalyzed asymmetric C—H functionalizations. This review is a comprehensive summary of the documented methods for cobalt-catalyzed, bidentate-chelation-assisted C—H bond functionalizations as of early 2023.

The α-C–H functionalization of piperidine catalyzed by tantalum complex 1 to pro­duce amine 2 was developed (Org. Lett. 2013, 15, 2182) by Laurel L. Schafer at the University of British Columbia. An asymmetric diamination of diene 3 with diaziri­dine reagent 4 under palladium catalysis to furnish cyclic sulfamide 5 was developed (Org. Lett. 2013, 15, 796) by Yian Shi at Colorado State University. Enantioenriched β-fluoropiperdine 8 was prepared (Angew. Chem. Int. Ed. 2013, 52, 2469) via amino­fluorocyclization of 6 with hypervalent iodide 7, as reported by Cristina Nevado at the University of Zurich. Erick M. Carreira at ETH Zürich disclosed (J. Am. Chem. Soc. 2013, 135, 6814) a ruthenium-catalyzed hydrocarbamoylation of allylic formamide 9 to yield pyrrolidone 10. Hans-Günther Schmalz at the University of Köln disclosed (Angew. Chem. Int. Ed. 2013, 52, 1576) an asymmetric hydrocyanation of styrene 11 with Ni(cod)₂ and phosphine–phosphite ligand 12 to yield exclusively the branched cyanide 13. A simi­lar transformation of styrene 11 to the hydroxycarbonylated product 15 was catalyzed (Chem. Commun. 2013, 49, 3306) by palladium complex 14, as reported by Matthew L. Clarke at the University of St Andrews. Feng-Ling Qing at the Chinese Academy of Sciences found (Angew. Chem. Int. Ed. 2013, 52, 2198) that the hydrotrifluoromethylation of unactivated alkene 16 to 17 was catalyzed by silver nitrate. The same transformation was also reported (J. Am.Chem. Soc. 2013, 135, 2505) by Véronique Gouverneur at the University of Oxford using a ruthenium photocatalyst and the Umemoto reagent 18. Clark R. Landis at the University of Wisconsin, Madison reported (Angew. Chem. Int. Ed. 2013, 52, 1564) a one-pot asymmetric hydroformylation using 21 followed by Wittig olefination to transform alkene 19 into the γ-chiral α,β-unsaturated carbonyl compound 20. Debabrata Mati at the Indian Institute of Technology Bombay found (J. Am. Chem. Soc. 2013, 135, 3355) that alkene 22 could be nitrated stereoselectively with silver nitrite and TEMPO to form alkene 23. Damian W. Young at the Broad Institute disclosed (Org. Lett. 2013, 15, 1218) that a macrocyclic vinylsiloxane 24, which was synthesized via an E-selective ring clos­ing metathesis reaction, could be functionalized to make either E- or Z-alkenes, 25 and 26.

AbstractThe possibility of creating a chiral center directly from two C—H bonds, or from a C—H bond and an X—H bond (X = heteroatom), without any prior derivatization (e.g., the installation of a leaving group) opens up many new possibilities in synthesis. Many chiral ligands and organocatalysts have now been discovered to be compatible with the oxidizing conditions in which these transformations take place. Furthermore, as reactions that can be performed under milder conditions are found, such as those that involve the use of molecular oxygen or even air to accept the two hydrogen atoms lost, or that can be run at lower temperatures, the repertoire of cross-dehydrogenative coupling (CDC) methodologies has become even bigger. Ligands such as mono- and bisoxazolines, bisphosphines, axially chiral binaphthols and bi-2-naphthylamine derivatives, and salens, as well as organocatalysts such as amino acids, chiral amines and diamines, cinchona alkaloids, axially chiral phosphoric acids, imidodiphosphoric acids, imidazolinones, and thioureas, amongst others, have been found to be robust and to perform well under CDC reaction conditions, providing high asymmetric induction and good yields of products. Some of these catalysts also work well in synergy with another catalyst. Recent developments in this area include the use of light energy for activation in combination with photocatalysts, as well as methods based on the use of electrochemistry. In this review, methods involving CDC that have been developed for the synthesis of molecules with one or more chiral centers, including compounds with axial or planar chirality, are presented, and their scope and limitations are discussed. The organization is based firstly on the type of catalysis used, and then divided further according to the type of bond being formed.