Jennifer A. Love

Synthesis of 1,1-disubstituted olefins via catalytic alkyne hydrothiolation/Kumada cross-coupling.

Using recently developed methodology for the regioselective formation of branched alkyl vinyl sulfides, we report a convenient route to 1,1-disubstituted olefins. We demonstrate that n-propanethiol successfully undergoes catalytic alkyne hydrothiolation with both aryl and aliphatic alkynes using Tp*Rh(PPh3)2 as the catalyst. The resulting vinyl sulfides undergo Kumada cross-coupling to afford the desired disubstituted alkene. Both two-step and one-pot procedures are reported.

Nickel-Catalyzed Selective Defluorination to Generate Partially Fluorinated Biaryls

A Ni-catalyzed, chemoselective cross-coupling reaction of polyfluoroarenes under mild reaction conditions is reported. A variety of fluorine-containing biaryls are synthesized in good-to-excellent yields. A wide range of substitution patterns and functional groups are tolerated.

The first metal-catalyzed intramolecular [5+2] cycloadditions of vinylcyclopropanes and alkenes: Scope, stereochemistry, and asymmetric catalysis

Abstract The first studies of the metal-catalyzed [5+2] cycloadditions of vinylcyclopropanes and alkenes are described. These reactions proceed with exceptional diastereoselectivity and in good to excellent yields. The effect of tether and substituent variations are examined. In addition, preliminary studies show that enantioselective cycloadditions can be achieved through the use of catalysts modified with chiral phosphine ligands. This novel, general, and efficient procedure provides a fundamentally new approach to the synthesis of a variety of products of structural and medicinal significance.

Synthesis of 1,1-disubstituted alkyl vinyl sulfides via rhodium-catalyzed alkyne hydrothiolation: scope and limitations.

Described herein are the scope and limitations using Tp*Rh(PPh(3))(2) as a catalyst for alkyne hydrothiolation with alkyl thiols. In general, catalytic hydrothiolation proceeds in high yields and with high regioselectivity for a wide range of alkynes and thiols. A variety of functional groups were well-tolerated, including nitriles, amines, halogens, ethers, esters and silanes, although strongly coordinating groups were found to be incompatible with hydrothiolation. Both sterically encumbered alkynes and thiols were successful in hydrothiolation. Electron rich alkynes react more rapidly than electron deficient alkynes. Overall, this hydrothiolation protocol provides convenient access to a variety of functionalized branched alkyl vinyl sulfides.

Nickel‐Catalyzed Csp2Csp3 Bond Formation by CarbonFluorine Activation

We report herein a general catalytic method for Csp(2)-Csp(3) bond formation through C-F activation. The process uses an inexpensive nickel complex with either diorganozinc or alkylzinc halide reagents, including those with β-hydrogen atoms. A variety of fluorine substitution patterns and functional groups can be readily incorporated. Sequential reactions involving different precatalysts and coupling partners permit the synthesis of densely functionalized fluorinated building blocks.

Reactivity by Design—Metallaoxetanes as Centerpieces in Reaction Development

2.2.3. CO2 Fixation with Epoxides 2020 2.3. C-C Bond Forming Reactions 2020 2.3.1. Reductive Coupling 2020 2.3.2. Metallaoxetanes as Metathesis Precursors 2020 2.4. Other Reactions 2021 3. Isolated Metallaoxetanes 2022 3.1. Group 4 Metallaoxetanes 2022 3.2. Group 5 Metallaoxetanes 2023 3.3. Group 6 Metallaoxetanes 2024 3.4. Group 8 Metallaoxetanes 2026 3.5. Group 9 Metallaoxetanes 2028 3.6. Group 10 Metallaoxetanes 2033 3.7. Group 11 Metallaoxetanes 2036 4. Preparation and Reactivity of Metallaoxetanes 2036 5. Discussion and Outlook 2043 Author Information 2043 Biographies 2043 Acknowledgment 2043 References 2043

Capturing HBCy2: Using N,O-Chelated Complexes of Rhodium(I) and Iridium(I) for Chemoselective Hydroboration

1,3-N,O-chelated complexes of Rh(I) and Ir(I) cooperatively and reversibly stabilized the B-H bond of HBCy2 to afford six-membered metallaheterocycles (M=Rh (7) or Ir (8)) having a δ-[M]⋅⋅⋅H-B agostic interaction. Treatment of these Shimoi-type borane adducts 7 or 8 with both an aldehyde and an alkene resulted in chemoselective aldehyde hydroboration and reformation of the 1,3-N,O-chelated starting material. The observed chemoselectivity is inverted from that of free HBCy2 , which is selective for alkene hydroboration.

Exploring Regioselective Bond Cleavage and Cross‐Coupling Reactions using a Low‐Valent Nickel Complex

Recently, esters have received much attention as transmetalation partners for cross-coupling reactions. Herein, we report a systematic study of the reactivity of a series of esters and thioesters with [{(dtbpe)Ni}2(μ-η(2):η(2)-C6H6)] (dtbpe=1,2-bis(di-tert-butyl)phosphinoethane), which is a source of (dtbpe)nickel(0). Trifluoromethylthioesters were found to form η(2)-carbonyl complexes. In contrast, acetylthioesters underwent rapid Cacyl-S bond cleavage followed by decarbonylation to generate methylnickel complexes. This decarbonylation could be pushed backwards by the addition of CO, allowing for regeneration of the thioester. Most of the thioester complexes were found to undergo stoichiometric cross-coupling with phenylboronic acid to yield sulfides. While ethyl trifluoroacetate was also found to form an η(2)-carbonyl complex, phenyl esters were found to predominantly undergo Caryl-O bond cleavage to yield arylnickel complexes. These could also undergo transmetalation to yield biaryls. Attempts to render the reactions catalytic were hindered by ligand scrambling to yield nickel bis(acetate) complexes, the formation of which was supported by independent syntheses. Finally, 2-naphthyl acetate was also found to undergo clean Caryl-O bond cleavage, and although stoichiometric cross-coupling with phenylboronic acid proceeded with good yield, catalytic turnover has so far proven elusive.

Oxidation State Dependent Coordination Modes: Accessing an Amidate‐Supported Nickel(I) δ‐bis(C−H) Agostic Complex

Amidate-supported two- and three-coordinate NiI complexes were synthesized by reduction of the corresponding NiII precursors. A dramatic change in binding mode is observed upon reduction from NiII to NiI . The NiI derivatives include an unprecedented NiI bis(C-H) agostic complex and a two-coordinate NiI complex.

Synthesis of 2-Nickela(II)oxetanes from Nickel(0) and Epoxides: Structure, Reactivity, and a New Mechanism of Formation.

2-Nickelaoxetanes have been frequently invoked as reactive intermediates in catalytic reactions of epoxides using nickel, but have never been isolated or experimentally observed in these transformations. Herein, we report the preparation of a series of well-defined nickelaoxetanes formed via the oxidative addition of nickel(0) with epoxides featuring ketones. The stereochemistry of the products is retained, which has not yet been reported for nickelaoxetanes. Theoretical calculations support a bimetallic ring-opening/closing pathway over a concerted oxidative addition. Initial reactivity studies of a nickelaoxetane demonstrated protonolysis, oxidatively induced reductive elimination, deoxygenation, and elimination reactions when treated with the appropriate reagents.