Catalyst-Controlled [3 + 2] Annulation of Allenes with N-Monosubstituted Hydroxylamines for Regioselective Synthesis of Two Types of Isomeric Isoxazolidines.

Catalyst-controlled regioselective [3 + 2] cascade annulation of allenes with N-monosubstituted hydroxylamines for precise construction of two types of isoxazolidine regiomers has been developed. The Ce(OTf)3 and MgCl2 can guide the nitrogen and oxygen atoms of N-hydroxyarylamides to both ends of the consecutive double bond of allenes, respectively, to afford two kinds of isomeric products. Notably and remarkably, the consecutive double bond of allenes served as a C3 synthon.

Chemoenzymatic formal synthesis of (+)-brazilin.

Herein, the manuscript presents a chemoenzymatic formal synthetic route of (+)-brazilin, a homoisoflavonoid natural product with a chroman skeleton cis-fused with a 2,3-dihydro-1H-indene unit, which is isolated from the traditional Chinese medicine, Caesalpinia sappan L. The key feature of the synthetic strategy includes an enzyme-mediated desymmetrization by employing lipase from Candida antarctica type B (CALB) and a one-pot SN2/hydrolysis reaction.

Synthesis of 3,4,5-Trisubstituted 1,2,4-Triazoles via I2-Catalyzed Cycloaddition of Amidines with Hydrazones.

A general and practical method for the construction of various 3,4,5-trisubstituted 1,2,4-triazoles via I2-catalyzed cycloaddition of N-functionalized amidines with hydrazones is reported. This strategy features cheap and readily available catalyst and starting materials, broader substrate scope, and moderate-to-good yields. The mechanism study shows that the existence of hydrogen on the nitrogen of hydrazones is crucial for this transformation.