Yancheng Hu

From Propargylamides to Oxazole Derivatives: NIS-Mediated Cyclization and Further Oxidation by Dioxygen

NIS-mediated iodocyclization of N-sulfonyl propargylamides for the synthesis of various oxazolidines and iodoalkylidenedihydrooxazoles via a 5-exo-dig process is developed. The resulting iodoalkylidenedihydrooxazoles can be further transformed into the corresponding oxazoles in the presence of dioxygen.

Synthesis of Tetrasubstituted Pyrroles from Terminal Alkynes and Imines

Tetrasubstituted pyrroles can be obtained via the reaction of terminal alkynes and imines using (n)BuLi as the base in one step with high chemoselectivity (method 1). Alternatively, the intermediate propargylamines can also react with imines to afford tetrasubstituted pyrroles when using LiHMDS as the base (method 2), which provides a complementary method to construct the pyrroles with different substituents.

Synthesis of Functionalized Oxazoles via Silver-Catalyzed Cyclization of Propargylamides and Allenylamides

Silver(I)-catalyzed [3,3] rearrangement of N-sulfonyl propargylamides affords functionalized oxazoles with highly regioselective migration of the sulfonyl group by the introduction of acyloxy groups. The allenylamides, generated from the corresponding propargylamides, can also undergo the silver-catalyzed cyclization to give various 5-vinyloxazoles.

Gold(I)-Catalyzed Intra- and Intermolecular Alkenylations of β-Yne-pyrroles: Facile Formation of Fused Cycloheptapyrroles and Functionalized Pyrroles

An efficient gold(I)-catalyzed alkenylation of β-alkyne-substituted pyrroles is reported. The intramolecular reaction gives straightforward access to different types of seven-membered-ring-fused pyrroles with endo-selectivity, and the intermolecular reaction with alkynes provides functionalized pyrrole derivatives.

Transition-Metal Controlled Diastereodivergent Radical Cyclization/Azidation Cascade of 1,7-Enynes

A strategy for achieving diastereodivergent azidations of enynes has been developed, employing azide transfer from the M-N3 complex to alkyl radicals. Following this concept, the diastereoselectivity has been switched by modulating the transition metals and the ligands. The Mn(III)-mediated radical cyclization/azidation cascade of 1,7-enynes afforded trans-fused pyrrolo[3,4-c]quinolinones, whereas the Cu(II)/bipyridine system gave cis-products.

Tf2NH-Catalyzed Formal [3 + 2] Cycloaddition of Ynamides with Dioxazoles: A Metal-Free Approach to Polysubstituted 4-Aminooxazoles

An unprecedented Tf2NH-catalyzed formal [3 + 2] cycloaddition of ynamides with dioxazoles was developed to construct various polysubstituted 4-aminooxazoles. This approach features a metal-free catalytic bimolecular assembly of oxazole motifs, a low-cost catalyst, exceptionally mild reaction conditions, a very short reaction time, a broad substrate scope, and high efficiency. This metal-free protocol may find applications in pharmaceutical-oriented synthesis.