Jun-Fang Gong

Cobalt‐Catalyzed C(sp2)H Alkoxylation of Aromatic and Olefinic Carboxamides

The cobalt-catalyzed alkoxylation of C(sp(2) )uf8ffH bonds in aromatic and olefinic carboxamides has been developed. The reaction proceeded under mild conditions in the presence of Co(OAc)2 ⋅4H2 O as the catalyst and tolerates a wide range of both alcohols and benzamide substrates, including even olefinic carboxamides. In addition, this reaction is the first example of the direct alkoxylation of alkenes through Cuf8ffH bond activation.

Copper-Mediated Direct Aryloxylation of Benzamides Assisted by an N,O-Bidentate Directing Group

Copper-mediated selective mono- or diaryloxylation of benzamides has been achieved by using 2-aminopyridine 1-oxide as a new and removable N,O-bidentate directing group. The reaction system shows a broad substrate scope and provides a straightforward way for the synthesis of mono- and diaryloxylated benzoic acids.

Chiral bis(imidazolinyl)phenyl NCN pincer rhodium(III) catalysts for enantioselective allylation of aldehydes and carbonyl-ene reaction of trifluoropyruvates.

Chiral NCN pincer rhodium(III) complexes with bis(imidazolinyl)phenyl ligands were found to be effective catalysts for the allylation of a variety of electronically and structurally diverse aldehydes with allyltributyltin, giving the corresponding optically active homoallylic alcohols in high yields with enantioselectivities of up to 97% ee. These complexes were also applied in the carbonyl-ene reaction of ethyl or methyl trifluoropyruvate with various 2-arylpropenes. With the aid of silver trifluoromethanesulfonate, the pincer rhodium(III) catalysts could catalyze the reaction to provide the corresponding chiral α-hydroxy-α-trifluoromethyl esters in good yields with high stereoselectivities (up to 95% ee).

PCN Pincer Palladium(II) Complex Catalyzed Enantioselective Hydrophosphination of Enones: Synthesis of Pyridine-Functionalized Chiral Phosphine Oxides as NCsp3O Pincer Preligands

A series of chiral PCN pincer Pd(II) complexes VI-XIII with aryl-based aminophosphine-imidazoline or phosphinite-imidazoline ligands were synthesized and characterized. They were examined as enantioselective catalysts for the hydrophosphination of enones. Among them, complex IX, which features a Ph2PO donor as well as an imidazoline donor with (4S)-phenyl and N-Tol-p groups, was found to be the optimal catalyst. Thus, in the presence of 2-5 mol % of complex IX a wide variety of enones reacted smoothly with diarylphosphines to give the corresponding chiral phosphine derivatives in high yields with enantioselectivities of up to 98% ee. In particular, heteroaryl species such as 2-thienyl-, 2-furyl-, and 2-pyridinyl-containing enones that have a strong coordination ability to the Pd center were also appropriate substrates for the current catalytic system. For example, hydrophosphination of 2-alkenoylpyridines with diphenylphosphine followed by oxidation with H2O2 afforded the corresponding pyridine-functionalized chiral phosphine oxides in good yields with good to excellent enantioselectivities (10 examples, up to 95% ee). Furthermore, it had been demonstrated that the obtained pyridine-containing phosphine oxide acted as a tridentate ligand in the reaction with PdCl2 to form an intriguing NCsp(3)O pincer Pd(II) complex via Csp(3)-H bond activation, which to our knowledge is the first example of a chiral DCsp(3)D Pd pincer (D ≠ D; D and D denote donor atoms such as P, N, etc.).

Copper-Mediated Direct Alkoxylation of Arenes Using an N,O-Bidentate Directing System

Highly effective CuCl-mediated C-H alkoxylation of arenes and heteroarenes has been developed by using a 2-aminopyridine 1-oxide moiety as an N,O-bidentate directing group. The reaction proceeds smoothly using a broad range of substrates to afford o-alkoxylated benzoic and heteroaromatic amide products. Moreover, the reaction system shows remarkable compatibility when hexafluoroisopropanol is used as a coupling parter; halogen, nitro, ether, alkoxy, ester, and sulfonyl functional groups are all tolerated. The directing group can be easily removed by base hydrolysis, affording o-alkoxylated benzoic acids.

An Approach to 3-(Indol-2-yl)succinimide Derivatives by Manganese-Catalyzed C–H Activation

The manganese-catalyzed addition of C-2 position of indoles to maleimides has been achieved under additive-free conditions. The manganese catalyst exhibits excellent chemo- and regioselectivity, good functional group compatibility, and high catalytic efficiency. The substrate scope can also be extended to maleates, ethyl acrylate, 1,4-dihydro-1,4-epoxynaphthalene, pyrroles, and 2-phenylpyridine, which further demonstrates the universality of this straightforward approach.

Efficient and scalable Pd-catalyzed double aminocarbonylations under atmospheric pressure at low catalyst loadings

By using a robust acenaphthoimidazolylidene palladium complex (Pd-NHC 1), a scalable approach to access a variety of chiral, pharmaceutical and structurally intriguing N-substituted phthalimides via double aminocarbonylations has been established under atmospheric carbon monoxide pressure at catalyst loadings as low as 0.05 mol%. In addition, the fluorescent properties of the selected N-substituted phthalimide products were also characterized. In comparison with well-known fluorescent molecules, some of them exhibited enhanced violet emission, especially for the ester analogue of Alrestatin, which further confirmed the applicability of the protocol.

Cobalt(II)/(imidazoline–oxazoline)-catalyzed enantioselective Michael addition of 2-acetyl azaarenes to β-CF3-β-disubstituted nitroalkenes

A series of chiral (imidazoline–oxazoline) N,N-bidentate ligands L1–L5 derived from 2,2-dimethylmalonic acid were conveniently synthesized and characterized. With the aid of the new ligands, the first Co(II)-catalyzed asymmetric Michael addition of 2-acetyl azaarenes to β-CF3-β-disubstituted nitroalkenes was successfully achieved, producing chiral compounds with a trifluoromethylated all-carbon quaternary stereocenter in good yields with enantioselectivities of up to 98% ee.

Synthesis, Characterization, and Crystal Structures of Heteroannular Cyclopalladated Ferrocenylimine-Pyridine Complexes

Two new heteroannular cyclopalladated ferrocenylimine-pyridine derivatives, 2a and 2b, were easily prepared by the reaction of chlorine-bridged binuclear palladium complexes, 1a and 1b, with pyridine in high yields. They were characterized by ESI-MS, H-NMR, and IR spectra. The detailed structures of complexes 2a and 2b were determined by single-crystal X-ray analysis. According to the crystal structure, the palladium atom is bound to the unsubstituted Cp ring, forming a new heteroannular pyridine-cyclopalladated large-membered metallocycle. Complex 2a exists as a dimer in the crystal due to intermolecular CH(CH˭N)···Cl hydrogen bonds, while 2b has a two-dimensional network structure formed by the intermolecular hydrogen bonds between the Cl atom with the adjacent C-H groups of Cp and pyridine.