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1. Construction of congested Csp ³ –Csp ³ bonds by a formal Ni-catalyzed alkylboration

   https://doi.org/10.1039/d1sc00900a  

   Simlandy, Amit Kumar; Sardini, Stephen R.; Brown, M. Kevin (April 2021, Chemical Science)

   null (Ed.)

   Through the combination of a Ni-catalyzed alkene alkenylboration followed by hydrogenation, the synthesis of congested Csp 3 –Csp 3 -bonds can be achieved. Conditions have been identified that allow for the use of both alkenyl-bromides and -triflates. In addition, the hydrogenation creates another opportunity for stereocontrol, thus allowing access to multiple stereoisomers of the product. Finally, the method is demonstrated in the streamlined synthesis of a biologically relevant molecule. 

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2. Organophotoredox/Palladium Dual Catalytic Decarboxylative Csp ³ -Csp ³ Coupling of Carboxylic Acids and π-Electrophiles

   https://doi.org/10.1039/D0SC02609C  

   Cartwright, Kaitie C; Tunge, Jon (January 2020, Chemical Science)

   A dual catalytic decarboxylative allylation and benzylation method for the construction of new C(sp 3 )–C(sp 3 ) bonds between readily available carboxylic acids and functionally diverse carbonate electrophiles has been developed. The new process is mild, operationally simple, and has greatly improved upon the efficiency and generality of previous methodology. In addition, new insights into the reaction mechanism have been realized and provide further understanding of the harnessed reactivity. 

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3. Improved Synthesis of Chiral 1,4,7‐Triazacyclononane Derivatives and Their Application in Ni‐Catalyzed Csp ³ −Csp ³ Kumada Cross‐Coupling

   https://doi.org/10.1002/hlca.202300170  

   Hu, Chi‐Herng; Byeong Chae, Ju; Mirica, Liviu M. (December 2023, Helvetica Chimica Acta)

   Abstract Herein, we report four new chiral 1,4,7‐triazacyclononane (TACN) derivatives and their corresponding nickel(II) chloride complexes. All TACN ligands are bearing one chiral N‐substituent and two alkyl (methyl ortert‐butyl) N‐substituents, and we have developed a new synthetic method for the dimethyl‐substituted TACN derivative, in order to prevent the rotational isomers that hinder the cyclization reaction. The nickel complexes change their coordination geometry significantly depending on the steric bulk of the N‐alkyl substituents, from a dinuclear tris(μ‐chloro)dinickel complex to mononuclear Ni‐dichloride and Ni‐chloride complexes. These complexes were then employed in the alkyl‐alkyl Kumada cross‐coupling reaction and revealed that the more sterically hindered ligands produced more homocoupled product rather than the cross‐coupled product, while the mononuclear Ni‐dichloride complex exhibited significantly lower catalytic activity. These chiral complexes were also employed in enantioconvergent cross‐coupling reactions as well, to afford significant enantioenrichment. Overall, the least sterically hindered Ni complex yields the best yields in the alkyl‐alkyl Kumada cross‐coupling reaction among the four complexes investigated, as well as the highest enantioselectivity. 

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4. N-Directed fluorination of unactivated Csp ³ –H bonds

   https://doi.org/10.1039/C9SC04055B  

   Pinter, Emily N.; Bingham, Jenna E.; AbuSalim, Deyaa I.; Cook, Silas P. (January 2020, Chemical Science)

   Site-selective fluorination of aliphatic C–H bonds remains synthetically challenging. While directed C–H fluorination represents the most promising approach, the limited work conducted to date has enabled just a few functional groups as the arbiters of direction. Leveraging insights gained from both computations and experimentation, we enabled the use of the ubiquitous amine functional group as a handle for the directed C–H fluorination of Csp 3 –H bonds. By converting primary amines to adamantoyl-based fluoroamides, site-selective C–H fluorination proceeds under the influence of a simple iron catalyst in 20 minutes. Computational studies revealed a unique reaction coordinate for the catalytic process and offer an explanation for the high site selectivity. 

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5. Stereospecific Csp ³ Suzuki–Miyaura Cross-Coupling That Evades β-Oxygen Elimination

   https://doi.org/10.1021/acscatal.2c03245  

   LaPorte, Antonio J.; Shi, Yao; Hein, Jason E.; Burke, Martin D. (September 2022, ACS Catalysis)