Synthesis of α,β-Unsaturated Amidines through Gold-Catalyzed Intermolecular Reaction of Azides with Ynamides.

A concise and flexible synthesis of α,β-unsaturated amidines via gold-catalyzed intermolecular ynamide amination/carbene 1,2-shift between ynamides and benzylic azides has been developed. Under mild reaction conditions, various α,β-unsaturated amidines were obtained in mostly good yields, thus providing an efficient and atom-economic way for the construction of valuable α,β-unsaturated amidines.

Gold-Catalyzed Intermolecular Ynamide Amination-Initiated Aza-Nazarov Cyclization: Access to Functionalized 2-Aminopyrroles.

A novel gold-catalyzed intermolecular ynamide amination-initiated aza-Nazarov cyclization has been developed, allowing the facile and efficient synthesis of various 2-aminopyrroles in moderate to good yields. Furthermore, a mechanistic rationale for this tandem sequence, especially for the observed high regioselectivity, is also well supported by DFT (density functional theory) computations. The high flexibility, broad substrate scope, and mild nature of this reaction render it a viable alternative for the construction of 2-aminopyrroles.

Gold-Catalyzed Tandem Cycloisomerization-Halogenation of Chiral Homopropargyl Sulfonamides.

Two new gold-catalyzed tandem cycloisomerization-halogenation reactions of chiral homopropargyl sulfonamides have been developed. Various enantioenriched 3,3-diiodopyrrolidin-2-ols and 3-fluoropyrrolidin-2-ols were obtained in moderate-to-good yields with excellent enantio- and diastereoselectivity.

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.