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1. Cyclopentadienyl Amidinate Ligand Directing Effects in the Enantioselective Living Coordinative Chain Transfer Polymerization of 1,5-Hexadiene

   https://doi.org/10.3390/catal14120944  

   Burrows, Cole M; Zavalij, Peter Y; Sita, Lawrence R (December 2024, Catalysts)

   The new chiral and configurationally stable cyclopentadienyl amidinate (CPAM) hafnium complexes, (RC, RHf)-2 and (SC, SHf)-3, have been obtained in enantio- and diastereomerically pure form. Upon activation with the borate co-initiator, [PhNHMe2][B(C6F5)4] (B1), 2 and 3 can serve as pre-initiators for the enantioselective living coordinative polymerization (LCP) and living coordinative chain transfer polymerization (LCCTP) of 1,5-hexadiene to provide optically active poly (methylene-1,3-cyclopentane) (PMCP) and end-group-functionalized PMCP (x-PMCP) in scalable quantities, respectively. 13C NMR stereochemical microstructural analyses reveal the role of ligand directing effects for the two-step propagation mechanism of 1,2-migratory insertion/ring-closing cyclization and structure/property relationships for these new PMCP and x-PMCP materials. 

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2. Hemilabile and Redox‐Active Quinone Ligands Unlock sp ³ ‐Rich Couplings in Nickel‐Catalyzed Olefin Carbosulfenylation

   https://doi.org/10.1002/anie.202411870  

   Li, Zi‐Qi; Alturaifi, Turki M; Cao, Yilin; Joannou, Matthew V; Liu, Peng; Engle, Keary M (December 2024, Angewandte Chemie International Edition)

   Abstract A three‐component coupling approach toward structurally complex dialkylsulfides is described via the nickel‐catalyzed 1,2‐carbosulfenylation of unactivated alkenes with organoboron nucleophiles and alkylsulfenamide (N−S) electrophiles. Efficient catalytic turnover is facilitated using a tailored N−S electrophile containing anN‐methyl methanesulfonamide leaving group, allowing catalyst loadings as low as 1 mol %. Regioselectivity is controlled by a collection of monodentate, weakly coordinating native directing groups, including sulfonamides, amides, sulfinamides, phosphoramides, and carbamates. Key to the development of this transformation is the identification of quinones as a family of hemilabile and redox‐active ligands that tune the steric and electronic properties of the metal throughout the catalytic cycle. Density functional theory (DFT) results show that the duroquinone (DQ) ligand adopts different coordination modes in different stages of the Ni‐catalyzed 1,2‐carbosulfenylation‐binding as an η⁶capping ligand to stabilize the precatalyst/resting state and prevent catalyst decomposition, binding as an X‐type redox‐active durosemiquinone radical anion to promote alkene migratory insertion with a less distorted square planar Ni(II) center, and binding as an L‐type ligand to promote N−S oxidative addition at a relatively more electron‐rich Ni(I) center. 

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3. Rhodium‐Catalyzed Asymmetric Arylation‐Induced Glycolate Aldol Additions of Silyl Glyoxylates

   https://doi.org/10.1002/anie.202311554  

   Turman, Nolan C.; Smith, Kendrick L.; Crawford, Evan T.; Robins, Jacob G.; Weber, Kathryn M.; Liu, Shubin; Johnson, Jeffrey S. (September 2023, Angewandte Chemie International Edition)

   Abstract (Diene)Rh(I) complexes catalyze the stereoselective three‐component coupling of silyl glyoxylates, arylboronic acids, and aldehydes to give glycolate aldol products. The participation of Rh‐alkoxides in the requisite Brook rearrangement was established through two component Rh‐catalyzed couplings of silyl glyoxylates with ArB(OH)₂to give silyl‐protected mandelate derivatives. The intermediacy of a chiral Rh‐enolate was inferred through enantioselective protonation using a chiral Rh‐catalyst. Diastereoselective three‐component couplings with aldehydes as terminating electrophiles to give racemic products were best achieved with a bulky aryl ester on the silyl glyoxylate reagent. Optimal enantioselective couplings were carried out with thetert‐butyl ester variant using an anisole‐derived enantiopure tricyclo[3.2.2.0^2,4]nonadiene ligand. 

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4. Nickel‐Catalyzed Enantioselective Reductive Alkyl‐Carbamoylation of Internal Alkenes

   https://doi.org/10.1002/anie.202207536  

   Wu, Xianqing; Turlik, Aneta; Luan, Baixue; He, Feng; Qu, Jingping; Houk, K. N.; Chen, Yifeng (July 2022, Angewandte Chemie International Edition)

   Abstract Herein, we leverage the Ni‐catalyzed enantioselective reductive dicarbofunctionalization of internal alkenes with alkyl iodides to enable the synthesis of chiral pyrrolidinones bearing vicinal stereogenic centers. The application of newly developed^1‐NapQuinim is critical for formation of two contiguous stereocenters in high yield, enantioselectivity, and diastereoselectivity. This catalytic system also improves both the yield and enantioselectivity in the synthesis of α,α‐dialkylated γ‐lactams. Computational studies reveal that the enantiodetermining step proceeds with a carbamoyl‐Ni^Iintermediate that is reduced by the Mn reductant prior to intramolecular migratory insertion. The presence of thet‐butyl group of the Quinim ligand leads to an unfavorable distortion of the substrate in the TS that leads to the minor enantiomer. Calculations also support an improvement in enantioselectivity with^1‐NapQuinim compared to^p‐tolQuinim. 

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5. Asymmetric synthesis of pharmaceutically relevant 1-aryl-2-heteroaryl- and 1,2-diheteroarylcyclopropane-1-carboxylates

   https://doi.org/10.1039/d1sc02474d  

   Sharland, Jack C.; Wei, Bo; Hardee, David J.; Hodges, Timothy R.; Gong, Wei; Voight, Eric A.; Davies, Huw M. (August 2021, Chemical Science)

   This study describes general methods for the enantioselective syntheses of pharmaceutically relevant 1-aryl-2-heteroaryl- and 1,2-diheteroarylcyclopropane-1-carboxylates through dirhodium tetracarboxylate-catalysed asymmetric cyclopropanation of vinyl heterocycles with aryl- or heteroaryldiazoacetates. The reactions are highly diastereoselective and high asymmetric induction could be achieved using either ( R )-pantolactone as a chiral auxiliary or chiral dirhodium tetracarboxylate catalysts. For meta - or para -substituted aryl- or heteroaryldiazoacetates the optimum catalyst was Rh 2 ( R-p -Ph-TPCP) 4 . In the case of ortho -substituted aryl- or heteroaryldiazoacetates, the optimum catalyst was Rh 2 ( R -TPPTTL) 4 . For a highly enantioselective reaction with the ortho -substituted substrates, 2-chloropyridine was required as an additive in the presence of either 4 Å molecular sieves or 1,1,1,3,3,3-hexafluoroisopropanol (HFIP). Under the optimized conditions, the cyclopropanation could be conducted in the presence of a variety of heterocycles, such as pyridines, pyrazines, quinolines, indoles, oxadiazoles, thiophenes and pyrazoles. 

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