We disclose that 1,3-bis(diphenylphosphino)methane]nickel(II) chloride NiCl(2)(dppp)] is a highly active, universally applicable, cheap, and stable catalyst for Suzuki-Miyaura cross-coupling reactions of aryl halides with a catalyst loading of lower than 1 mol%, and more notably, in the absence of extra supporting ligands. Under the optimized reaction conditions, a broad range of aryl bromides as well as the notoriously unreactive aryl chlorides, including activated, non-activated, deactivated, and heteroaromatic and sterically hindered substrates can be coupled smoothly with various boronic acids (47 examples, 48-98% yields). In addition, the transformation is tolerant of various functional groups such as ether, ester, ketone, aldehyde, cyano, and un-protected amino and hydroxy groups. Finally, the potential utilization of the methodology was further demonstrated by the gram-scale synthesis of several core structures of commercialized antihypertensive drugs and fungicides. Thus, the combination of high activity, broad applicability, cheapness, and high stability of NiCl(2)(dppp) presented in this work constitutes one of the few prominent catalysts which allow for practical and reliable construction of biaryls and heterobiaryls with structural diversity from readily available aryl halides and boronic acids.
We present a highly active, inexpensive, universally applicable, and markedly stable 1,3-bis(diphenylphosphino)propane]nickel(II) chloride Ni(dppp)Cl(2)] catalyst that is capable of effecting the Suzuki-Miyaura cross-coupling of the inherently less reactive but readily available aryl tosylates and mesylates with only 1 mol% loading and in the absence of extra supporting ligand. Under the optimized reaction conditions, cross-coupling of a wide range of activated, non-activated, and deactivated, as well as sterically hindered and heteroaromatic substrates (36 examples) could proceed efficiently to afford the coupled products in 53-99% yields. Consequently, the results presented in this work provide a significant advance in Suzuki-Miyaura cross-coupling in terms of generality, practicality, and cost which are key concerns in recent research regarding transition metal-catalyzed cross-couplings.
The first organocatalytic diastereo- and enantioselective Michael addition reaction of 4-substituted-pyrazolin-5-ones to nitroolefins has been developed with a chiral bifunctional thiourea as organocatalyst. A wide variety of desired multi-substituted pyrazolin-5-one derivatives with contiguous quaternary and tertiary stereocenters are smoothly obtained in very good yields (up to 98%) with excellent enantioselectivities (up to > 99% ee) and acceptable diastereoselectivities (up to 80:20). This experimentally simple process facilitates the access to various enantioenriched, multiply substituted pyrazolin-5-one derivatives, potential biologically active molecules, starting from readily available starting materials.
A practical method has been developed for the C-sulfinylation of enamides and enecarbamates using sodium phenylsulfinate/methyltrichlorosilane (PhSO2Na/MeSiCl3) as the sulfinylating reagent and N,N-dimethylacetamide (DMAc) as the Lewis base promoter. which allows for the preparation of a variety of N-protected-beta-sulfinylenamines in high yields and good stereoselectivities. The Lewis base is found to be important for both the in situ generation of the active sulfinylating species (PhSOCl) and the sulfinylation step.
We recently reported the first example of S-chiral organocatalysts, that are highly efficient and enantioselective in substoichometric amounts, and which use a chiral monosulfinamide group as Lewis base to activate trichlorosilane (HSiCl3) to reduce N-arylketimines. A plausible mechanism involving two molecules of the monosulfinamde catalyst for the activation of HSiCl3 prompted us to design S-chiral bissulfinamides as new catalysts. We herein describe our findings that an easily prepared S-chiral bissulfinamide bearing a five-methylene linkage not only inherited the excellent substrate generality from the monosulfinamide catalysts, but also exhibited further improved enantioselectivity.
Bipyrazolidin-3-one derivatives are biologically significant compounds and their importance has increased in the past decades. In this paper, the first stereoselective 3 + 2] dipolar cycloadditions of azomethine imines with alpha,beta-unsaturated aldehydes catalyzed by readily available alpha,alpha-diarylprolinol salts are reported, providing a facile route to the synthesis of various chiral bipyrazolidin-3-one derivatives under mild conditions. The organocatalyst 1g with strongly electron-withdrawing groups exhibited the best stereoselectivity (exo:endo up to 98:2, for exo product up to 97% ee), in the combination with trifluoroacetic acid.
Heck coupling reactions of methyl acrylate with various aryl bromides have been investigated using a Pd/TPP catalyst in toluene under pressurized CO2 conditions up to 13 MPa. Although CO2 is not a reactant, the pressurization of the reaction liquid phase with CO2 has positive and negative impacts on the rate of Heck coupling depending on the structures of the substrates examined. In the case of either 2-bromoacetophenone or 2-bromocinnamate, the conversion has a maximum at a CO2 pressure of about 3 MPa;
Heck coupling reactions of methyl acrylate with various aryl bromides have been investigated using a Pd/TPP catalyst in toluene under pressurized CO2 conditions up to 13 MPa. Although CO2 is not a reactant, the pressurization of the reaction liquid phase with CO2 has positive and negative impacts on the rate of Heck coupling depending on the structures of the substrates examined. In the case of either 2-bromoacetophenone or 2-bromocinnamate, the conversion has a maximum at a CO2 pressure of about 3 MPa; for the former, it is much larger by a factor of 3 compared with that under ambient pressure. For 2-bromobenzene, in contrast, the conversion is minimized at a similar CO2 pressure, being half compared with that at ambient pressure
An efficient and divergent one-pot synthesis of substituted 2H-pyrans, 4H-pyrans and pyridin-2(1H)-ones from beta-oxo amides based on the selection of the reaction conditions is reported. Mediated by N,N,N',N'-tetramethylchloroformamidinium chloride, beta-oxo amides underwent intermolecular cyclizations in the presence of triethylamine at room temperature to give substituted 2H-pyrans in high yields, which could be converted into substituted 4H-pyrans in the presence of sodium hydroxide in ethanol at room temperature, or into substituted pyridin-2(1H)-ones under reflux.
Copolymerizations of ethylene with 5-vinyl-2-norbornene or 5-ethylidene-2-norbornene under the action of various titanium complexes bearing bis(beta-enaminoketonato) chelate ligands of the type, (RN)-N-1=C(R-2)CH=C(R-3)O](2)TiCl2 (1, R-1=Ph, R-2=CF3, R-3=Ph; 2, R-1=C6H4F-p, R-2=CF3, R-3=Ph; 3, R-1=Ph, R-2=CF3, R-3=t-Bu; 4, R-1=C6H4F-p, R-2=CF3, R-3=t-Bu; 5, R-1=Ph, R-2=CH3, R-3=CF3; 6, R-1=C6H4F-p, R-2=CH3 R-3=CF3), have been shown to occur with the regioselective insertion of the endocyclic double bond of the monomer into the copolymer chain, leaving the exocyclic vinyl double bond as a pendant unsaturation. The ligand modification strongly affects the copolymerization behaviour. High catalytic activities and efficient co-monomer incorporation can be easily obtained by optimizing the catalyst structures and polymerization conditions.