Guangyang Xu

Gold(I)‐Catalyzed Diazo Coupling: Strategy towards Alkene Formation and Tandem Benzannulation

A gold(I)-catalyzed cross-coupling of diazo compounds to afford tetrasubstituted alkenes has been developed by taking advantage of a trivial electronic difference between two diazo substrates. A N-heterocyclic-carbene-derived gold complex is the most effective catalyst for this transformation. Based on this new strategy, a gold(I)-initiated benzannulation has been achieved through a tandem reaction involving a diazo cross-coupling, 6π electrocyclization, and oxidative aromatization.

Gold(I)‐Catalyzed Diazo Cross‐Coupling: A Selective and Ligand‐Controlled Denitrogenation/Cyclization Cascade

An unprecedented gold-catalyzed ligand-controlled cross-coupling of diazo compounds by sequential selective denitrogenation and cyclization affords N-substituted pyrazoles in a position-switchable mode. This novel transformation features selective decomposition of one diazo moiety and simultaneous preservation of the other one from two substrates. Notably, the choice of the ancillary ligand to the gold complex plays a pivotal role on the chemo- and regioselectivity of the reactions.

Gold-Catalyzed Formal [4+1]/[4+3] Cycloadditions of Diazo Esters with Triazines

Reported herein is the unprecedented gold-catalyzed formal [4+1]/[4+3] cycloadditions of diazo esters with hexahydro-1,3,4-triazines, thus providing five- and seven-membered heterocycles in moderate to high yields under mild reaction conditions. These reactions feature the use of a gold complex to accomplish the diverse annulations and the first example of the involvement of a gold metallo-enolcarbene in a cycloaddition. It is also the first utilization of stable triazines as formal dipolar adducts in the carbene-involved cycloadditions. Mechanistic investigations reveal that the triazines reacted directly, rather than as formaldimine precursors, in the reaction process.

Stereodivergent Synthesis of N-Heterocycles by Catalyst-Controlled, Activity-Directed Tandem Annulation of Diazo Compounds with Amino Alkynes.

A stereodivergent synthesis of five-membered N-heterocycles, such as 2,3-dihydropyrroles, and 2-methylene and 3-methylene pyrrolidines, has been developed through a tandem annulation of amino alkynes with diazo compounds and involves the trapping of in situ formed intermediates. Mechanistic investigations indicate that the copper-catalyzed tandem annulations proceed by allenoate formation and subsequent intramolecular hydroamination. In contrast, the rhodium-catalyzed protocol features a carbenoid insertion into the NH bond and subsequent Conia-ene cyclization.

Realized C-H functionalization of aryldiazo compounds via rhodium relay catalysis.

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.

Copper-Catalyzed Diazo Cross-/Homo-Coupling toward Tetrasubstituted Olefins and Applications on the Synthesis of Maleimide Derivatives

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.

Palladium-catalyzed carbenoid based N–H bond insertions: application to the synthesis of chiral α-amino esters

A highly efficient palladium-catalyzed carbenoid based N-H bond insertion has been developed. The α-amino esters were obtained in high isolated yields. Moreover, by choosing a suitable chiral auxiliary, stereoselective Pd-catalyzed N-H insertion has been realized. The chiral α-amino esters were obtained in high yields (up to 91%) and with excellent diastereoselectivities (d.r. > 19 : 1).

Base‐Promoted/Gold‐Catalyzed Intramolecular Highly Selective and Controllable Detosylative Cyclization

A highly selective, controllable and synthetically useful base-promoted intramolecular detosylative cyclization of bis-N-tosylhydrazones has been achieved, affording N-containing heterocycles and cyclic olefins under transition-metal-free or gold-catalyzed procedures, respectively. Moreover, an effective and practical metal-free or gold-catalyzed approach to synthesize polycyclic aromatic compounds is also reported.

Copper-Catalyzed NH Insertion and Oxidative Aromatization Cascade: Facile Synthesis of 2-Arylaminophenols

A copper-catalyzed cascade reaction of N-H insertion and oxidative aromatization has been developed. 2-Arylaminophenols have been prepared in moderate to high yields from the diazo substrates. Moreover, this newly established methodology allows efficient access to natural 1-oxygenated carbazole alkaloids, such as glycozolicine and murrayafoline A.

When Aryldiazonium Salts Meet Vinyl Diazoacetates: A Cobalt-Catalyzed Regiospecific Synthesis of N-Arylpyrazoles

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.