Ru(II)-Catalyzed One-Pot Synthesis of 1,2-Hydropyridines via a Three-Component Reaction

A ruthenium(II)-catalyzed one-pot synthesis of highly substituted 1,2-dihydropyridines (DHPs) via a three-component reaction system has been realized. The reaction is conducted using a simple Ru(II) catalyst without the addition of specific ligands. The catalytic system exhibits good functionality tolerance with a wide range of starting materials. The DHPs obtained can be easily converted into tetrahydropyridines and azabicyclo[4.2.0]octa-4,7-dienes by subsequent reduction or [2 + 2] cycloaddition reaction

Synthesis of Spirocyclohexadienones via Palladium-Catalyzed Dearomatization of Dibenzoxaborins

The development of Pd(II)-catalyzed dearomatization transformation of dibenzoxaborins with alkynes triggered by transmetalation from boron to palladium has been achieved, leading to the synthesis of spirocyclohexadienones, an important skeleton demonstrating potential biomedical utility. The [3 + 2] spiroannulation exhibits remarkable regioselectivity and broad substrate scope under mild reaction conditions. This methodology employs dibenzoxaborin as a substrate to establish the formal dearomatization of 2-phenylphenol, which poses a formidable energy barrier to the destruction of aromaticity

Asymmetric [5+1] Annulation via C–H Activation/1,4-Rh Migration/Double Bond Shift Using a Transformable Pyridazine Directing Group

N-Heterocycle-assisted C–H activation/annulation reactions have provided new concepts for the construction and transformation of azacycles. In this work, we disclose a [5+1] annulation reaction using a novel transformable pyridazine directing group (DG). The DG-transformable reaction mode led to the construction of a new heterocyclic ring accompanied by transformation of the original pyridazine directing group via a C–H activation/1,4-Rh migration/double bond shift pathway, affording the skeleton of pyridazino[6,1-b]quinazolines with a good substrate scope under mild conditions. Diverse fused cyclic compounds can be achieved by derivatization of the product. The asymmetric synthesis of the skeleton was also realized to afford the enantiomeric products with good stereoselectivity

Rh(III)-Catalyzed C–C Coupling of Diverse Arenes and 4‑Acyl-1-sulfonyltriazoles via C–H Activation

4-Acyl-1-sulfonyltriazoles act as versatile carbene reagents in Cp*Rh­(III)-catalyzed ortho-selective coupling with arenes via C–H activation. The coupling led to olefination with possible cyclization, depending on the nature of the arene

Rh(III)-Catalyzed Annulation of 2‑Biphenylboronic Acid with Diverse Activated Alkenes

Rhodium­(III)-catalyzed annulation of 2-biphenylboronic acids with three classes of activated alkenes has been realized, leading to the synthesis of fused or bridged cyclic skeletons via transmetalation-initiated C–H activation. In the annulative coupling of 2-biphenylboronic acid with a CF3-substituted enone, the bulky cyclopentadienyl ligand (CptBu) in the catalyst proved effective to promote the reductive elimination process prior to protonolysis, affording the [4 + 2] annulated products instead of the simple 1,4-addition product. Seven-membered rings were obtained when disubstituted cyclopropenones were employed. Bridged cycles were isolated from the coupling of 2-biphenylboronic acid with benzoquinones as a result of 2-fold Michael additions. The substrate scopes were found to be broad with up to 99% yield under air-tolerant conditions

Ag(I)-Catalyzed Nucleophilic Addition and Friedel–Crafts Alkylation between α‑Oxoketene Dithioacetals and Propargyl Carbonates

Silver-catalyzed nucleophilic addition and intramolecular Friedel–Crafts alkylation between α-oxoketene dithioacetals and tertiary propargylic carbonates have been realized. The reactions proceeded in moderate to good yields with broad substrate scope, providing a straightforward method for the synthesis of substituted indenes

Divergent Annulative C–C Coupling of Indoles Initiated by Manganese-Catalyzed C–H Activation

Manganese­(I)-catalyzed C–H activation of indoles and divergent annulative coupling with alkyne-tethered cyclohexadienones has been realized under operationally simple conditions. These annulation systems are under condition control. The coupling in the presence of BPh3 additive followed a C–H activation-alkyne insertion-Michael addition pathway, affording an exocyclic olefin attached to a tetrahydrofuran ring. In contrast, when Zn­(OAc)2/PivOH additives were introduced, initial olefination en route to intramolecular Diels–Alder reaction and subsequent elimination of an alcohol was followed to deliver a fused six-membered ring. The selectivity stands in contrast to those reported using rhodium­(III) and cobalt­(III) catalysts, highlighting the unique reactivity and selectivity of manganese catalysts

Synthesis of Bridged Cycloisoxazoline Scaffolds via Rhodium-Catalyzed Coupling of Nitrones with Cyclic Carbonate

Bridged isoxazolidines were synthesized via Rh(III)-catalyzed C–H allylation of α-aryl nitrones with 5-methylene-1,3-dioxan-2-one. The nitrone group serves as a directing group and 1,3-dipole in the C–H activation/[3 + 2] cycloaddition cascade, exhibiting excellent chemo- and stereoselectivity along with good functional group compatibility. The resulting skeletal structure was conveniently modified to produce a range of important chemical frameworks, and the protocol was applied to biologically active molecules

Rhodium-Catalyzed Cascade Oxidative Annulation Leading to Substituted Naphtho[1,8-<i>bc</i>]pyrans by Sequential Cleavage of C(sp²)–H/C(sp³)–H and C(sp²)–H/O–H Bonds

The cascade oxidative annulation reactions of benzoylacetonitrile with internal alkynes proceed efficiently in the presence of a rhodium catalyst and a copper oxidant to give substituted naphtho­[1,8-bc]­pyrans by sequential cleavage of C­(sp2)–H/C­(sp3)–H and C­(sp2)–H/O–H bonds. These cascade reactions are highly regioselective with unsymmetrical alkynes. Experiments reveal that the first-step reaction proceeds by sequential cleavage of C­(sp2)–H/C­(sp3)–H bonds and annulation with alkynes, leading to 1-naphthols as the intermediate products. Subsequently, 1-naphthols react with alkynes by cleavage of C­(sp2)–H/O–H bonds, affording the 1:2 coupling products. Moreover, some of the naphtho­[1,8-bc]­pyran products exhibit intense fluorescence in the solid state