Synthesis of unsymmetrical biphenyls as potent cytotoxic agents

Chemo- and regioselective benzylic C(sp3)–H oxidation bridging the gap between hetero- and homogeneous copper catalysis

Selective C‒H functionalization in a pool of proximal C‒H bonds, predictably altering their innate reactivity is a daunting challenge. We disclose here, an expedient synthesis of privileged seven-membered lactones, dibenzo[c,e]oxepin-5(7H)-one through a highly chemoselective benzylic C(sp³)‒H activation. Remarkably, the formation of widely explored six-membered lactone via C(sp²)‒H activation is suppressed under the present conditions. The reaction proceeds smoothly on use of inexpensive metallic copper catalyst and di-tert-butyl peroxide (DTBP). Owing to the hazards of stoichiometric DTBP, further, we have developed a sustainable metallic copper/rose bengal dual catalytic system coupled with molecular oxygen replacing DTBP. A 1,5-aryl migration through Smiles rearrangement was realized from the corresponding diaryl ether substrates instead of expected eight-membered lactones. The present methodology is scalable, applied to the total synthesis of cytotoxic and neuroprotective natural product alterlactone. The catalyst is recyclable and the reaction can be performed in a copper bottle without any added catalyst.

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Catalytic strategy for chemo- and regioselective benzylic C–H activation

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Bulk copper catalysis merging with photocatalysis

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Reusable copper catalyst

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Reaction demonstrated in commercial copper bottle without external catalyst

Cu(ii)-vitamin C-complex catalyzed photo-induced homocoupling reaction of aryl boronic acid in base-free and visible light conditions

In this work, the photocatalytic efficiency of Cu(ii)-vitamin C complex immobilized on titanium dioxide nanoparticles was exploited in the photo-assisted homocoupling reaction of aryl boronic acids under heterogeneous conditions. The homocoupling reaction affords the corresponding symmetrical biaryls in 50-97% yields at ambient temperature in the air under visible light irradiation without any need for any additive such as base or oxidant. This method tolerates various substituents on the aryl boronic acids such as halogen, carbonyl, and a nitro group. The light-dependent photocatalytic performance of the title catalyst evaluated by action spectra revealed a maximum apparent quantum efficiency (AQYs) at 410 nm demonstrating the visible-light-driven photocatalytic reaction. The as-prepared nano biophotocatalyst proved to be reusable at least six times without losing its activity. Thus this work exhibits a favorable method from the environmental and economic point of view which enables the industrially important reactions such as coupling reactions, to be carried out efficiently under photocatalytic and practically attainable conditions.

Synthesis and anti-proliferative activities of 5,6,7-trimethoxyflavones and their derivatives

A series of 5,6,7-trimethoxyflavones 1a-1g and their derivatives 2a-2g, 3a-3d, 4 and 5, including the natural products 5,6,7-trimethoxy-4'-hydroxyflavone (1a), 5,6,7,3',4' -pentamethoxyflavone (sinensetin, 1 b), 5,6,7-trimethoxy-3',4'-methyl enedioxy flavone (1c), 5,6,7,3'-tetramethoxy-4,5'-methylenedioxyflavone (1e), 5,6,7, 3',4',5'-hextamethoxyflavone (1 g), 5-hydroxy-3,4,2',3',4'-pentamethoxy chal-cone (2 b), 5,4'-dihydroxy-6,7-dimethoxy flavone (cirsimaritin, 3a) and 5-hydroxy-6,7,3', 4'-tetramethoxyflavone (5-demethylsinensetin, 3 b), 3,5,6,7,3',4'-hexamethoxyflavone (3-methoxysinensetin, 4) and 5'-hydroxy-3,6,7,3',4'-pentamethoxyflavone (5) were synthesized. Their anti-proliferative activity in vitro was evaluated against a panel of four human cancer cell lines (Aspc-1, HCT-116, HepG-2 and SUN-5) by the CTG assay. The results showed that most of the synthetic compounds exhibited moderate to high anti-proliferative activities. In particular, compound 3c possess IC₅₀ (5.30 μM) values below 10 μM against Aspc-1 cells and are worthy of further investigation.

Cu(II)-Catalyzed Homocouplings of (Hetero)Arylboronic Acids with the Assistance of 2-O-Methyl-d-Glucopyranose

This is the first report of a natural ligand improving the copper-catalyzed homocouplings of (hetero)arylboronic acids. Various important synthetic biaryl intermediates in organic synthesis could be assembled via this method. To gain insight into this reaction, in situ React IR technology was used to confirm the effectivity of this catalyst system. This protocol could provide important biaryl compounds in high yields within a short time.

The palladium/norbornene-catalyzed ortho-silylmethylation reaction: a practical protocol for ortho-functionalized one-carbon homologation of aryl iodides

We reported the introduction of a functionalized methyl group into the ortho-position using the Catellani reaction.

Green synthesis of stable Cu(0) nanoparticles onto reduced graphene oxide nanosheets: a reusable catalyst for the synthesis of symmetrical biaryls from arylboronic acids under base-free conditions

The Cu(0) nanoparticle-rGO composites exhibit excellent catalytic activity for the synthesis of symmetrical biaryls from arylboronic acids under microwave irradiation.

Discovery of novel antitumor dibenzocyclooctatetraene derivatives and related biphenyls as potent inhibitors of NF-κB signaling pathway

Several dibenzocyclooctatetraene derivatives (5-7) and related biphenyls (8-11) were designed, synthesized, and evaluated for inhibition of cancer cell growth and the NF-κB signaling pathway. Compound 5a, a dibenzocyclooctatetraene succinimide, was discovered as a potent inhibitor of the NF-κB signaling pathway with significant antitumor activity against several human tumor cell lines (GI₅₀ 1.38-1.45 μM) and was more potent than paclitaxel against the drug-resistant KBvin cell line. Compound 5a also inhibited LPS-induced NF-κB activation in RAW264.7 cells with an IC₅₀ value of 0.52 μM, prevented IκB-α degradation and p65 nuclear translocation, and suppressed LPS-induced NO production in a dose-dependent manner. The antitumor data in cellular assays indicated that relative positions and types of substituents on the dibenzocyclooctatetraene or acyclic biphenyl as well as torsional angles between the two phenyls are of primary importance to antitumor activity.