A novel approach toward diverse six-membered carbo-/heterocycles has been developed using diazo compounds and alkyne-substituted malonates as the suitable substrates. The polyfunctionalized cyclohexenes, tetrahydropyridines, and dihydropyrans have been prepared in moderate to high yield under mild reaction conditions. Importantly, the ligand plays a significant role in this copper-catalyzed protocol.

A stereoselective, gold-catalyzed, cross-coupling reaction of enynones with diazo compounds has been developed, affording 2-alkenylfurans in moderate to good yields with excellent E-stereoselectivity. Upon using diazo compounds as nucleophiles to trap the in situ formed gold furyl carbene, this protocol provides a novel path toward the formation of unsymmetrical tetrasubstituted alkenes.

Gold-catalyzed regiodivergent cycloadditions of functionalized allenes with 1,3,5-triazines, providing diverse N-heterocycles in moderate to excellent yields under mild reaction conditions, are reported. Importantly, different types of allenes exhibit distinct selectivity and reactivity for the reactions. Mechanistic investigations reveal that all of the cycloadditions proceed through a stepwise [2 + 2 + 2]-cycloaddition process.

A distinct one-pot protocol toward several types of fused tricyclic scaffolds has been developed, by employing diazoesters and alkynyl-cyclohexadienones as starting materials, enabling rapid construction of diverse tricyclic compounds with multiple bonds formation in an operationally simple procedure. Typically, this controlled tandem sequence showcases the in situ formation of tetrasubstituted allenoates, an unprecedented anion-triggered annulation, and oxidative aromatization.

A novel protocol toward imidazolidines has been accomplished using tosylhydrazones and hexahydro-1,3,5-triazines as the substrates under metal-free reaction conditions. Importantly, the role of LiOtBu has been confirmed not only to release the diazo but also to promote the cycloaddition. Further mechanistic investigations reveal that the reaction proceeds through a stepwise [2 + 1 + 2] process.

A novel approach to synthesize seven-membered heterocycles is established by reacting amide tethered terminal alkynes with aryl diazoacetates in a one-pot reaction. This reaction involves copper-catalyzed cross coupling followed by base-promoted intramolecular Michael addition and yields products with a medium-sized ring.

A gold-catalyzed sequential annulation reaction to prepare 3,4-fused bicyclic furan compounds has been realized by employing 2-(1-alkynyl)-2-alken-1-ones and 1,3,5-triazines as the starting materials under mild reaction conditions. This protocol features multiple bond formation in a single operation with the incorporation of two nitrogen and two carbon atoms into the final products. A mechanistic investigation reveals that the sequential annulations involved an unprecedented stepwise [3+2+2]-cycloaddition.

The first gold-catalyzed highly regio- and enantioselective carbene insertion into the O–H bonds of 2-pyridones has been realized in the presence of catalytic amounts of chiral dual-gold complexes. The corresponding chiral products were obtained in moderate to good yields, excellent O-selectivity, excellent carbenic selectivity and moderate to excellent enantioselectivities (up to 96% ee).

An unprecedented gold-catalyzed [2+2+2+2]-annulation of 1,3,5-hexahydro-1,3,5-triazines with alkoxyallenes has been developed, providing eight-membered heterocycles in good to excellent yields. Deuterium labeling and control experiments reveal the possible reaction mechanism for this annulation.

We report here an unprecedented iron-catalyzed cycloaddition reaction of diazo surrogates with hexahydro-1,3,5-triazines, providing five-membered heterocycles in moderate to high yields under mild reaction conditions. This cycloaddition features C–N and C–C bond formation using a cheap iron catalyst. Importantly, different to our former report on a gold-catalyzed system, both donor/donor and donor/acceptor diazo substrates are tolerated in this iron-catalyzed protocol.

An unprecedented regioselective metallo-vinylcarbene insertion into O–H bonds has been achieved with vinyldiazoacetates and 2-pyridones/benzyl alcohols as ideal substrates, which displayed distinct regioselectivity by employing gold and silver catalytic systems.

We report here an effective protocol to prepare highly functionalized dihydropyrans via sequential reaction of cross-coupling-intramolecular Michael addition of functionalized terminal alkynes and diazo compounds under mild reaction conditions. Importantly, by choosing different ligands, the configuration of exocyclic double bonds of dihydropyrans can be selectively controlled.

A challenging selective intermolecular cross-coupling and homocoupling of aryl–aryl or aryl–alkyl diazo compounds has been accomplished via a copper system, which afforded tetrasubstituted olefins in moderate to high yields with good to excellent Z-selectivity. This novel methodology enables rapid synthesis of tetrasubstituted olefins, which would find broad application in accessing maleimide libraries of nature products and bioactive small molecules.

An unprecedented C–H functionalization of aryldiazo compounds without a preinstallation of directing group has been realized under mild conditions, which differs from former reports in its use of diazo compounds as coupling partners in directed C–H activations. This novel transformation has been realized by a rhodium self-relay catalysis, a tandem process of the in situ formation of a directing group and sequential C–H bond activation.

A copper-catalyzed stereoselective 1,3-dipolar cycloaddition of methyleneindolinones and N,N′-cyclic azomethine imines has been developed under mild reaction conditions. The spiro[pyrazolidin-3,3′-oxindoles] were obtained in moderate to high isolated yields (up to 82%) with good stereoselevtivities (up to 15:1) in the presence of 5 mol% of Cu(OAc)2 at room temperature.A copper-catalyzed stereoselective 1,3-dipolar cycloaddition of methyleneindolinones and N,N′-cyclic azomethine imines has been developed under mild reaction conditions.

A cobalt-catalyzed C–N bond formation between aryl diazonium salts and vinyl diazoacetates has been developed under relatively mild conditions. The N-arylpyrazoles have been prepared in moderate to high yields in a regiospecific way.

Polyheteroaromatic compounds are potential optoelectronic conjugated materials due to their electro- and photochemical properties. Transition-metal-catalyzed multiple C–H activation and sequential oxidative annulation allows rapidly assembling of those compounds from readily available starting materials. A rhodium-catalyzed cascade oxidative annulation of β-enamino esters or 4-aminocoumarins with internal alkynes is described to access those compounds, featuring multiple C–H/N–H bond cleavages and sequential C–C/C–N bond formations in one pot.

We report here an effective protocol to prepare highly functionalized dihydropyrans via sequential reaction of cross-coupling-intramolecular Michael addition of functionalized terminal alkynes and diazo compounds under mild reaction conditions. Importantly, by choosing different ligands, the configuration of exocyclic double bonds of dihydropyrans can be selectively controlled.

A novel approach to synthesize seven-membered heterocycles is established by reacting amide tethered terminal alkynes with aryl diazoacetates in a one-pot reaction. This reaction involves copper-catalyzed cross coupling followed by base-promoted intramolecular Michael addition and yields products with a medium-sized ring.

An unprecedented regioselective metallo-vinylcarbene insertion into O–H bonds has been achieved with vinyldiazoacetates and 2-pyridones/benzyl alcohols as ideal substrates, which displayed distinct regioselectivity by employing gold and silver catalytic systems.

The first gold-catalyzed highly regio- and enantioselective carbene insertion into the O–H bonds of 2-pyridones has been realized in the presence of catalytic amounts of chiral dual-gold complexes. The corresponding chiral products were obtained in moderate to good yields, excellent O-selectivity, excellent carbenic selectivity and moderate to excellent enantioselectivities (up to 96% ee).

A gold-catalyzed sequential annulation reaction to prepare 3,4-fused bicyclic furan compounds has been realized by employing 2-(1-alkynyl)-2-alken-1-ones and 1,3,5-triazines as the starting materials under mild reaction conditions. This protocol features multiple bond formation in a single operation with the incorporation of two nitrogen and two carbon atoms into the final products. A mechanistic investigation reveals that the sequential annulations involved an unprecedented stepwise [3+2+2]-cycloaddition.