Atom-economic generation of gold carbenes: gold-catalyzed formal [3+2] cycloaddition between ynamides and isoxazoles

Gold-catalyzed [4+3] and [4+4]-annulation reactions of t-butyl propiolate derivatives with epoxides and oxetanes for the construction of 1,4-dioxepane and 1,5-dioxocane cores

Gold-catalyzed [4+n]-annulations (n = 3, 4) of tert-butyl propiolate derivatives with epoxides or oxetanes proceed smoothly to yield seven- or eight-membered oxacyclic products efficiently. In the context of the [4+3]-annulations, product analysis reveals a retention of stereochemistry upon the intramolecular SN2 attack of an epoxide. We also report the [4+5]-annulation between one tert-butyl propiolate and γ-lactol, to manifest the utility toward medium-sized rings.

Dioxazoles, a new mild nitrene transfer reagent in gold catalysis: highly efficient synthesis of functionalized oxazoles

A gold-catalyzed regioselective [3+2] cycloaddition of ynamides with 1,4,2-dioxazoles was developed and offers a novel approach to obtain highly functionalized oxazoles under mild reaction conditions. 1,4,2-Dioxazole was found to act as an efficient N-acyl nitrene equivalent to trigger a facile generation of α-imino gold-carbene intermediate through the elimination of a ketone.

Synthesis of α-haloenamides via zinc halide mediated direct addition of benzhydryl halides to ynamides

A regio- and stereoselective synthesis of highly substituted α-haloenamides was described via the zinc halide mediated direct addition of benzhydryl halides to ynamides under mild conditions. The products α-haloenamides were further transformed into multisubstituted enamides via Suzuki and Sonogashira cross-coupling reactions.

Gold-catalyzed formation of indole derivatives from 2-alkynyl arylazides and oxygen-containing heterocycles

Gold-catalyzed ring-opening reactions of oxygen-containing heterocycles.

Recent progress towards gold-catalyzed synthesis of N-containing tricyclic compounds based on ynamides

The recent advances in the gold-catalyzed construction of N-containing tricycles based on ynamides are reviewed by highlighting their specificity and applicability, and the mechanistic rationale.

Synthesis of fused isoquinolines via gold-catalyzed tandem alkyne amination/intramolecular O–H insertion

A novel gold-catalyzed tandem alkyne amination/intramolecular O–H insertion has been developed. A variety of [1,4]oxazino[3,2-c]isoquinolines are readily accessed under mild reaction conditions by utilizing this strategy, thereby providing an efficient and practical route for the construction of synthetically useful fused isoquinolines.

An efficient approach toward formation of polycyclic coumarin derivatives via carbocation-initiated [4+2] cycloaddition and atom-economical photo-irradiated cyclization

Polycyclic coumarin derivatives were easily prepared by carbocation initiated [4+2] cycloaddition of propargyl silyl ethers with ynamides and fluorescent analysis-oriented photo-irradiated cyclization.

A zinc-catalyzed oxidative reaction of ynamides with phenols and thiophenols: highly site-selective synthesis of versatile α-aryloxy amides and α-arylthio amides

A zinc-catalyzed oxidative reaction of ynamides with phenols and thiophenols under mild reaction conditions has been developed, which provides various α-aryloxy amides and α-arylthio amides in moderate to good yields, respectively. Importantly, high chemoselectivity is achieved by such a non-noble metal-catalyzed alkyne oxidation.

Divergent C-H Insertion-Cyclization Cascades of N-Allyl Ynamides

Gold carbene reactivity patterns were accessed by ynamide insertion into a C(sp(3) )H bond. A substantial increase in molecular complexity occurred through the cascade polycyclization of N-allyl ynamides to form fused nitrogen-heterocycle scaffolds. Exquisite selectivity was observed despite several competing pathways in an efficient gold-catalyzed synthesis of densely functionalized C(sp(3) )-rich polycycles and a copper-catalyzed synthesis of fused pyridine derivatives. The respective gold-keteniminium and ketenimine activation pathways have been explored through a structure-reactivity study, and isotopic labeling identified turnover-limiting CH bond-cleavage in both processes.

Synthesis of α,β-Unsaturated N-Sulfonyl Imides through Zinc-Catalyzed Intermolecular Oxidation of N-Sulfonyl Ynamides

A novel zinc-catalyzed intermolecular oxidation of N-sulfonyl ynamides has been developed. A variety of functionalized α,β-unsaturated N-sulfonyl imides are readily accessed by utilizing this approach, thus providing a viable alternative to synthetically useful α,β-unsaturated imides. Importantly, the reaction is proposed to proceed by a vinyligous E2-type elimination pathway, but not metal carbene pathway.