Palladium-Catalyzed Coordination-Induced Remote C-H Aryl Etherification/Amination of 8-Amidoquinolines.

Herein, we report a direct method for palladium-catalyzed coordination-induced oxidative remote C-H aryl etherification of 8-amidoquinolines with p-benzoquinone monoacetal. The method provides access to C5-aryl etherified quinolines and shows site-selectivity different from that of typical palladium-catalyzed C(sp2)-H activation reactions. The p-benzoquinone monoacetals act both as oxidants and as aryl etherification reagents. By using proper substrates, C5-aminated quinolines and C4-etherifed 1-naphthylamine could also be formed.

Selective multifunctionalization of N-heterocyclic carbene boranes via the intermediacy of boron-centered radicals.

The selective difunctionalization of N-heterocyclic carbene (NHC) boranes with alkenes has been achieved via decatungstate and thiol synergistic catalysis. The catalytic system also allows stepwise trifunctionalization, leading to complex NHC boranes with three different functional groups which are challenging to prepare by other methods. The strong hydrogen-abstracting ability of the excited decatungstate enables the generation of boryl radicals from mono- and di-substituted boranes for realizing borane multifunctionalization. This proof-of-principle research provides a new chance for fabricating unsymmetrical boranes and developing boron-atom-economic synthesis.

Palladium metallaphotoredox-catalyzed 3-acylation of indole derivatives.

3-Acylindole motifs are wildly found in pharmaceuticals and biologically active alkaloids. Synthesis of this motif from aldehydes and indoles via dehydrogenative cross-coupling (CDC) reactions is the most efficient pathway. Here, we report a method for synthesis of 3-acyl indoles from aldehydes by a combination of photocatalysis and palladium catalysis. This mild, robust method is compatible with a wide array of functional groups and has a broad substrate scope. Our findings may inspire the development of new CDC reactions.

Palladium Metallaphotoredox-Catalyzed 2-Arylation of Indole Derivatives.

Given that biaryl motifs are found in many useful molecules, including pesticides, pharmaceuticals, functional materials, and polymers, the development of methods for their construction is important. Herein, we report a two-step method for C(sp2)-H/C(sp2)-H cross-coupling reactions to synthesize 2-arylindole derivatives by combining palladium catalysis and photocatalysis. This mild, dual-catalysis method showed good functional group tolerance and a wide substrate scope and could be used for late-stage functionalization of oligopeptides, drugs, and natural products.

Radical Transformation of Aliphatic C-H Bonds to Oxime Ethers via Hydrogen Atom Transfer.

Herein, we describe a strategy for conversion of aliphatic C-H bonds to oxime ethers via hydrogen atom transfer. In this strategy, the decatungstate anion and sulfate radical play complementary roles in the abstraction of hydrogen atoms from primary, secondary, and tertiary C-H bonds of alkanes. The easy accessibility of alkanes and the broad substrate scope, mild conditions, and excellent regioselectivity of these reactions make this strategy applicable for the transformation of raw materials to high-value chemicals.

Synthesis of Unnatural α-Amino Acids via Photoinduced Decatungstate-Catalyzed Giese Reactions of Aldehydes.

Synthesis of unnatural amino acids has long been a focus of chemistry research. Here, we present an efficient, general method that furnishes γ-carbonyl α-amino acids via photoinduced decatungstate-catalyzed Giese reactions of readily available aldehydes as radical precursors. This mild, robust method is compatible with a wide array of functional groups and has a broad substrate scope. We demonstrated the utility of the method by modifying several amino acid bearing drugs and natural products.

Construction of 2-(2-Arylphenyl)azoles via Cobalt-Catalyzed C-H/C-H Cross-Coupling Reactions and Evaluation of Their Antifungal Activity.

Although compounds with a 2-(2-arylphenyl) benzoxazole motif are biologically important, there are only a few methods for synthesizing them. Herein, we report an efficient method for synthesis of such compounds by means of cobalt-catalyzed C-H/C-H cross-coupling reactions. This method has a broad substrate scope and good tolerance for sensitive functional groups. In addition, we demonstrate that introducing a heteroarene moiety to biphenyl compounds enhanced their antifungal activity.

Peptide Tectonics: Encoded Structural Complementarity Dictates Programmable Self-Assembly.

Programmable self-assembly of peptides into well-defined nanostructures represents one promising approach for bioinspired and biomimetic synthesis of artificial complex systems and functional materials. Despite the progress made over the past two decades in the development of strategies for precise manipulation of the self-assembly of peptides, there is a remarkable gap between current peptide assemblies and biological systems in terms of structural complexity and functions. Here, the concept of peptide tectonics for the creation of well-defined nanostructures predominately driven by the complementary association at the interacting interfaces of tectons is introduced. Peptide tectons are defined as peptide building blocks exhibiting structural complementarity at the interacting interfaces of commensurate domains and undergoing programmable self-assembly into defined supramolecular structures promoted by complementary interactions. Peptide tectons are categorized based on their conformational entropy and the underlying mechanism for the programmable self-assembly of peptide tectons is highlighted focusing on the approaches for incorporating the structural complementarity within tectons. Peptide tectonics not only provides an alternative perspective to understand the self-assembly of peptides, but also allows for precise manipulation of peptide interactions, thus leading to artificial systems with advanced complexity and functions and paves the way toward peptide-related functional materials resembling natural systems.

Iridium-Catalyzed ortho-C(sp2)-H Amidation of Benzaldehydes with Organic Azides.

An iridium-catalyzed ortho-C(sp2)-H amidation reaction of benzaldehydes with organic azides has been developed. A catalytic amount of 3,5-di(trifluoromethyl)aniline was used to promote the Ir-catalyzed directed C-H amination reaction through a transient aldimine intermediate. This reaction tolerates a broad scope of benzaldehyde substrates and works well with a range of aryl- and alkylsulfonyl azides.

Palladium-catalyzed picolinamide-directed iodination of remote ortho-C-H bonds of arenes: Synthesis of tetrahydroquinolines.

A new palladium-catalyzed picolinamide (PA)-directed ortho-iodination reaction of ε-C(sp(2))-H bonds of γ-arylpropylamine substrates is reported. This reaction proceeds selectively with a variety of γ-arylpropylamines bearing strongly electron-donating or withdrawing substituents, complementing our previously reported PA-directed electrophilic aromatic substitution approach to this transformation. As demonstrated herein, a three step sequence of Pd-catalyzed γ-C(sp(3))-H arylation, Pd-catalyzed ε-C(sp(2))-H iodination, and Cu-catalyzed C-N cyclization enables a streamlined synthesis of tetrahydroquinolines bearing diverse substitution patterns.