Haibo Ge

Room Temperature Palladium-Catalyzed Decarboxylative ortho-Acylation of Acetanilides with α-Oxocarboxylic Acids

A novel Pd-catalyzed decarboxylative ortho-acylation of acetanilides with alpha-oxocarboxylic acids is realized at room temperature. This reaction provides efficient access to o-acyl acetanilides under mild conditions.

Nickel-Catalyzed Site-Selective Alkylation of Unactivated C(sp3)–H Bonds

The direct alkylation of unactivated sp(3) C-H bonds of aliphatic amides was achieved via nickel catalysis with the assist of a bidentate directing group. The reaction favors the C-H bonds of methyl groups over the methylene C-H bonds and tolerates various functional groups. Moreover, this reaction shows a predominant preference for sp(3) C-H bonds of methyl groups via a five-membered ring intermediate over the sp(2) C-H bonds of arenes in the cyclometalation step.

Copper‐Catalyzed Site‐Selective Intramolecular Amidation of Unactivated C(sp3)H Bonds

The intramolecular dehydrogenative amidation of aliphatic amides, directed by a bidentate ligand, was developed using a copper-catalyzed sp(3) C-H bond functionalization process. The reaction favors predominantly the C-H bonds of β-methyl groups over the unactivated methylene C-H bonds. Moreover, a preference for activating sp(3) C-H bonds of β-methyl groups, via a five-membered ring intermediate, over the aromatic sp(2) C-H bonds was also observed in the cyclometalation step. Additionally, sp(3) C-H bonds of unactivated secondary sp(3) C-H bonds could be functionalized by favoring the ring carbon atoms over the linear carbon atoms.

Cobalt-catalysed site-selective intra- and intermolecular dehydrogenative amination of unactivated sp 3 carbons

Cobalt-catalysed sp2 C–H bond functionalization has attracted considerable attention in recent years because of the low cost of cobalt complexes and interesting modes of action in the process. In comparison, much less efforts have been devoted to the sp3 carbons. Here we report the cobalt-catalysed site-selective dehydrogenative cyclization of aliphatic amides via a C–H bond functionalization process on unactivated sp3 carbons with the assistance of a bidentate directing group. This method provides a straightforward synthesis of monocyclic and spiro β- or γ-lactams with good to excellent stereoselectivity and functional group tolerance. In addition, a new procedure has been developed to selectively remove the directing group, which enables the synthesis of free β- or γ-lactam compounds. Furthermore, the first cobalt-catalysed intermolecular dehydrogenative amination of unactivated sp3 carbons is also realized.

Direct Aerobic Carbonylation of C(sp2)–H and C(sp3)–H Bonds through Ni/Cu Synergistic Catalysis with DMF as the Carbonyl Source

The direct carbonylation of aromatic sp(2) and unactivated sp(3) C-H bonds of amides was achieved via nickel/copper catalysis under atmospheric O2 with the assistance of a bidentate directing group. The sp(2) C-H functionalization showed high regioselectivity and good functional group compatibility. The sp(3) C-H functionalization showed high site-selectivity by favoring the C-H bonds of α-methyl groups over those of the α-methylene, β- or γ-methyl groups. Moreover, this reaction showed a predominant preference for functionalizing the α-methyl over α-phenyl group. Mechanistic studies revealed that nickel/copper synergistic catalysis is involved in this process.

Site-selective C–H arylation of primary aliphatic amines enabled by a catalytic transient directing group

Transition-metal-catalysed direct C–H bond functionalization of aliphatic amines is of great importance in organic and medicinal chemistry research. Several methods have been developed for the direct sp3 C–H functionalization of secondary and tertiary aliphatic amines, but site-selective functionalization of primary aliphatic amines in remote positions remains a challenge. Here, we report the direct, highly site-selective γ-arylation of primary alkylamines via a palladium-catalysed C–H bond functionalization process on unactivated sp3 carbons. Using glyoxylic acid as an inexpensive, catalytic and transient directing group, a wide array of γ-arylated primary alkylamines were prepared without any protection or deprotection steps. This approach provides straightforward access to important structural motifs in organic and medicinal chemistry without the need for pre-functionalized substrates or stoichiometric directing groups and is demonstrated here in the synthesis of analogues of the immunomodulatory drug fingolimod directly from commercially available 2-amino-2-propylpropane-1,3-diol. Transition-metal-catalysed direct C(sp3)−H functionalization of primary aliphatic amines is an attractive– but elusive – process that could provide efficient access to biologically and pharmaceutically important compounds. Now, a palladium-catalysed γ-arylation of primary alkylamines is achieved using an inexpensive, catalytic and transient directing group.

Nickel‐Catalyzed Site‐Selective Amidation of Unactivated C(sp3)H Bonds

Intramolecular dehydrogenative cyclization of aliphatic amides was achieved on unactivated sp(3) carbon atoms by a nickel-catalyzed CH bond functionalization process with the assistance of a bidentate directing group. The reaction favors the CH bonds of β-methyl groups over the γ-methyl or β-methylene groups. Additionally, a predominant preference for the β-methyl CH bonds over the aromatic sp(2) CH bonds was observed. Moreover, this process also allows for the effective functionalization of benzylic secondary sp(3) CH bonds.

Copper‐Catalyzed Aerobic Intramolecular Dehydrogenative Cyclization of N,N‐Disubstituted Hydrazones through C sp 3H Functionalization

An aerobic activity: The title reaction proceeds through an oxidation/cyclization/aromatization sequence under an atmosphere of O(2) (see scheme; DBU=1,8-diazabicyclo[5.4.0]undec-7-ene, DCE=1,2-dichloroethane, DMS=dimethylsulfide). This coupling reaction is the first to proceed via an iminium intermediate for a C(sp(3)-H bond-functionalization process, and provides an environmentally friendly and atom-efficient access to substituted pyrazoles.

Nickel‐Catalyzed Decarboxylative Acylation of Heteroarenes by sp2 CH Functionalization

Nickel-catalyzed ligand-free decarboxylative cross-coupling of azole derivatives with α-oxoglyoxylic acids has been developed. This work represents the first example of decarboxylative cross-coupling reactions, in a C-H bond functionalization manner, through nickel catalysis, and tolerates various functional groups. Additionally, this approach provides an efficient access to azole ketones, an important structural motif in many medicinal compounds with a broad range of biological activities.

Palladium-Catalyzed Site-Selective Fluorination of Unactivated C(sp3)–H Bonds

The transition-metal-catalyzed direct C-H bond fluorination is an attractive synthetic tool toward the preparation of organofluorines. While many methods exist for the direct sp(3) C-H functionalization, site-selective fluorination of unactivated sp(3) carbons remains a challenge. Direct, highly site-selective and diastereoselective fluorination of aliphatic amides via a palladium-catalyzed bidentate ligand-directed C-H bond functionalization process on unactivated sp(3) carbons is reported. With this approach, a wide variety of β-fluorinated amino acid derivatives and aliphatic amides, important motifs in medicinal and agricultural chemistry, were prepared with palladium acetate as the catalyst and Selectfluor as the fluorine source.