A general visible-light-induced single nickel-catalyzed cross-coupling method with alkylzirconocenes has been developed. Alkylzirconocenes are generated in situ from terminal or internal alkenes through hydrozirconation and chain walking. This method is suitable for a wide range of organic halides and alkenes with excellent functional group tolerance, suggesting great potential for construction of carbon-carbon bonds. This method represents the first visible-light-induced cross-coupling of alkylzirconocenes.

The [1,2]-Meisenheimer rearrangement is well known as the [1,2]-migration of an O-substituted hydroxylamine from a tertiary amine N-oxide, and it is frequently employed in organic synthesis to enforce adjacent carbon oxidation or install a 1,2-oxazine core, which is a prevalent structural feature and pharmacophore of many bioactive natural products. Although the [1,2]-Meisenheimer rearrangement was proposed to occur in the biosynthesis of a number of 1,2-oxazine-containing natural products, it has never been proved biosynthetically. Here, we identified the biosynthetic gene cluster of an insecticidal natural product, paeciloxazine (1), from Penicillium janthinellum and characterized a flavin-dependent monooxygenase, PaxA, as the first example that mediates the formation of a 1,2-oxazine moiety via Meisenheimer rearrangement. In vitro biochemical assays, site-directed mutations, docking and molecular dynamics simulations, and density functional theory calculations support the mechanism that PaxA first catalyzes N-oxidation to form an N-oxide intermediate, which undergoes [1,2]-Meisenheimer rearrangement with the assistance of an amino acid with proton transfer property. This study expands the repertoire of rearrangement reactions during the biosynthesis of natural products and provides a new strategy for discovering natural products with N–O tethers by genome mining.

A rhodium-catalyzed reaction between 3-diazoindolin-2-imines and 2H-azirines, followed by treatment with a base, furnishes 5H-pyrazino[2,3-b]indoles in excellent yields. A number of functional groups tolerate the reaction conditions, and the resulting 5H-pyrazino[2,3-b]indoles present strong photoluminecence in solutions, powders, and films.

3-Diazoindolin-2-imines reacted with chiral 2-(phenylamino)ethanols under copper catalysis to furnish chiral spiro[indoline-3,2'-oxazolidin]-2-imines in good yields with excellent diastereoselectivity. The reaction undergoes a copper-catalyzed cascade process involving the formation of copper carbene, C-N coupling, and C-O coupling.