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1. Ni- and Pd-Catalyzed Enantioselective 1,2-Dicarbofunctionalization of Alkenes

   https://doi.org/10.1055/a-2108-9549  

   Kang, Taeho ; Apolinar, Omar ; Engle, Keary M ( December 2023 , Synthesis)

   Catalytic enantioselective 1,2-dicarbofunctionalization (1,2-DCF) of alkenes is a powerful transformation of growing importance in organic synthesis for constructing chiral building blocks, bioactive molecules, and agrochemicals. Both in a two- and three-component context, this family of reactions generates densely functionalized, structurally complex products in a single step. Across several distinct mechanistic pathways at play in these transformations with nickel or palladium catalysts, stereocontrol can be obtained through tailored chiral ligands. In this Review we discuss the various strategies, mechanisms, and catalysts that have been applied to achieve enantioinduction in alkene 1,2-DCF.

   1 Introduction

   2 Two-Component Enantioselective 1,2-DCF via Migratory Insertion

   3 Two-Component Enantioselective 1,2-DCF via Radical Capture

   4 Three-Component Enantioselective 1,2-DCF via Radical Capture

   5 Three-Component Enantioselective 1,2-DCF via Migratory Insertion

   6 Miscellaneous Mechanisms

   7 Conclusion

    

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2. Nickel‐Catalyzed 1,2‐Diarylation of Alkenyl Carboxylates: A Gateway to 1,2,3‐Trifunctionalized Building Blocks

   https://doi.org/10.1002/anie.201913062  

   Derosa, Joseph ; Kang, Taeho ; Tran, Van T. ; Wisniewski, Steven R. ; Karunananda, Malkanthi K. ; Jankins, Tanner C. ; Xu, Kane L. ; Engle, Keary M. ( December 2019 , Angewandte Chemie International Edition)

   A nickel‐catalyzed conjunctive cross‐coupling of alkenyl carboxylic acids, aryl iodides, and aryl/alkenyl boronic esters is reported. The reaction delivers the desired 1,2‐diarylated and 1,2‐arylalkenylated products with excellent regiocontrol. To demonstrate the synthetic utility of the method, a representative product is prepared on gram scale and then diversified to eight 1,2,3‐trifunctionalized building blocks using two‐electron and one‐electron logic. Using this method, three routes toward bioactive molecules are improved in terms of yield and/or step count. This method represents the first example of catalytic 1,2‐diarylation of an alkene directed by a native carboxylate group.

    

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3. Nickel‐Catalyzed 1,2‐Diarylation of Alkenyl Carboxylates: A Gateway to 1,2,3‐Trifunctionalized Building Blocks

   https://doi.org/10.1002/ange.201913062  

   Derosa, Joseph ; Kang, Taeho ; Tran, Van T. ; Wisniewski, Steven R. ; Karunananda, Malkanthi K. ; Jankins, Tanner C. ; Xu, Kane L. ; Engle, Keary M. ( December 2019 , Angewandte Chemie)

   A nickel‐catalyzed conjunctive cross‐coupling of alkenyl carboxylic acids, aryl iodides, and aryl/alkenyl boronic esters is reported. The reaction delivers the desired 1,2‐diarylated and 1,2‐arylalkenylated products with excellent regiocontrol. To demonstrate the synthetic utility of the method, a representative product is prepared on gram scale and then diversified to eight 1,2,3‐trifunctionalized building blocks using two‐electron and one‐electron logic. Using this method, three routes toward bioactive molecules are improved in terms of yield and/or step count. This method represents the first example of catalytic 1,2‐diarylation of an alkene directed by a native carboxylate group.

    

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4. Intermolecular 2+2 imine-olefin photocycloadditions enabled by Cu(I)-alkene MLCT

   https://doi.org/10.1038/s41467-022-30393-6  

   Flores, Daniel M. ; Neville, Michael L. ; Schmidt, Valerie A. ( May 2022 , Nature Communications)

   2 + 2 Photocycloadditions are idealized, convergent construction approaches of 4-membered heterocyclic rings, including azetidines. However, methods of direct excitation are limited by the unfavorable photophysical properties of imines and electronically unbiased alkenes. Here, we report copper-catalyzed photocycloadditions of non-conjugated imines and alkenes to produce a variety of substituted azetidines. Design principles allow this base metal-catalyzed method to achieve 2 + 2 imine-olefin photocycloaddition via selective alkene activation through a coordination-MLCT pathway supported by combined experimental and computational mechanistic studies.

    

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5. Electrochemical C–H bond activation via cationic iridium hydride pincer complexes

   https://doi.org/10.1039/C9SC03076J  

   Lindley, Brian M. ; Walden, Andrew G. ; Brasacchio, Ann Marie ; Casuras, Andrea ; Lease, Nicholas ; Chen, Chun-Hsing ; Goldman, Alan S. ; Miller, Alexander J. ( January 2019 , Chemical Science)

   A C–H bond activation strategy based on electrochemical activation of a metal hydride is introduced. Electrochemical oxidation of ( tBu4 PCP)IrH 4 ( tBu4 PCP is [1,3-( t Bu 2 PCH 2 )-C 6 H 3 ] − ) in the presence of pyridine derivatives generates cationic Ir hydride complexes of the type [( tBu4 PCP)IrH(L)] + (where L = pyridine, 2,6-lutidine, or 2-phenylpyridine). Facile deprotonation of [( tBu4 PCP)IrH(2,6-lutidine)] + with the phosphazene base tert -butylimino-tris(pyrrolidino)phosphorane, t BuP 1 (pyrr), results in selective C–H activation of 1,2-difluorobenzene (1,2-DFB) solvent to generate ( tBu4 PCP)Ir(H)(2,3-C 6 F 2 H 3 ). The overall electrochemical C–H activation reaction proceeds at room temperature without need for chemical activation by a sacrificial alkene hydrogen acceptor. This rare example of undirected electrochemical C–H activation holds promise for the development of future catalytic processes. 

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