Silver-Catalyzed One-Pot Biarylamination of Quinones with Arylamines: Access to N-Arylamine-Functionalized p-Iminoquinone Derivatives

Oxidative Aminotrifluoromethylation of 1,4-Naphthoquinone

A strategy for convenient and precise oxidative aminotrifluoromethylation of 1,4-naphthoquinone with the Togni reagent and amines has been demonstrated via a radical process. This method allows efficient access for the preparation of a wide range of CF3-functionalized 1,4-naphthoquinones under mild conditions, and its application in late-stage modification of drug molecules is achieved. Mechanistic studies indicate that 1,4-naphthoquinone serves as both a substrate and a catalyst and that the Togni reagent plays a dual role of a substrate and an oxidant. As a result, the title reaction can take place in the dark without external catalysts and oxidants.

Blue Light Irradiated Metal-, Oxidant-, and Base-Free Cross-Dehydrogenative Coupling of C(sp2)-H and N-H Bonds: Amination of Naphthoquinones with Amines

Herein, we report a blue-light-driven amination of C(sp²)-H bond of naphthoquinones and quinones with the N-H bond of primary and secondary amines for the synthesis of 2-amino-naphthoquinones and 2-amino-quinones. The coupling of naphthoquinones with a wide array of aliphatic, aromatic, chiral, primary, and secondary amines having electron donating (-CH₃, -OCH₃, -SCH₃), withdrawing (-F, -Cl, -Br, -I), and CO₂H, -OH, -NH₂ groups with acidic protons selectively occurred to afford C-N coupled 2-amino-naphthoquinones in 60-99% yields and hydrogen gas as a byproduct in methanol solvent without using any additional reagents, additives, and oxidant under the blue light irradiation. Mechanistic insight by DFT computation, controlled experiments, kinetic isotopic effect, and substitution effect of the substrates suggest that the reaction proceeds by radical pathway in which naphthoquinone forms a highly oxidizing naphthoquinonyl biradical upon irradiation of blue light (457 nm). Consequently, electron transfer from electron-rich amine to an oxidizing naphthoquinonyl biradical leads to a naphthoquinonyl radical anion and aminyl radical cation, followed by proton transfer and delocalization leading to a carbon-centered naphthoquinonyl radical. The cross-coupling of naphthoquinonyl carbon-centered and aminyl nitrogen radicals forms a C-N bond, with subsequent elimination of hydrogen gas (which was also confirmed by GC-TCD), affording 2-amino-1,4-naphthoquinone under metal-, reagent-, base-, and oxidant-free conditions.

Silver-Catalyzed, One-Pot, Three-Component Difunctionalization of Quinones: Synthesis of Indole-Functionalized p-Iminoquinone Derivatives

A one-pot, three-component difunctionalization of quinones with indoles and arylamines has been developed to synthesize indole functionalized p-iminoquinones derivatives. The approach employed AgOAc as the catalyst in the presence of 3-chlorophenylboronic acid, giving a series of indole functionalized p-iminoquinones derivatives in moderate to good yields. This catalytic approach represents a step-economic and convenient strategy for the difunctionalization of quinones. A plausible reaction pathway has been proposed based on a series of control experiments.