Organic Letters最新文献

Herein, we report a visible-light-driven and cobalt-mediated 1,4-hydroamination reaction of 1,3-dienes with arylmines as the nucleophiles. The reaction involves regioselective addition of [Co^III]-H to 1,3-diene, followed by oxidation and nucleophilic substitution by amines. Using Ir(ppy)₃ as the photocatalyst enables the cobalt redox cycle to be implemented without using an external oxidant and hydride regent. This protocol can be applied as well to forge the carbon-oxygen and carbon-sulfur bonds in an analogous way.

A synthetic route to the highly functionalized tetracyclic core framework of daphlongamine B is described. Key features of the strategy involve an oxidative dearomatization-induced [4+2] cycloaddition, a di-π-methane rearrangement, and a ring-closing metathesis reaction. Our approach enables the reliable construction of a fully elaborated tetracyclic precursor, which, in turn, provides valuable functional handles for further elaboration to the target molecule.

A novel protocol for the chemically divergent synthesis of chiral oxacycles has been developed using organo/metal relay catalysis. The methodology integrates a stereospecific Mannich reaction between β,γ-alkynyl-α-imino esters and 1,3-diones catalyzed by a chiral bifunctional squaramide, followed by Lewis acid-catalyzed regioselective annulation reactions. By switching the Lewis acid employed, we achieved a divergent pathway to construct structurally related pyran and furan derivatives from a common intermediate. The (3+3) and (3+2) annulation products were obtained in high yields and excellent stereoselectivities. Comprehensive mechanistic studies were conducted to establish the reaction mechanism.

We describe a protocol for the selective cleavage of the 2-deoxystreptamine ring from the structurally unusual aminoglycoside antibiotic apramycin, enabling for the first time the preparation of aprabiosamine derivatives. We further describe reglycosylation of the aprabiosamine core with a selectively protected optically pure streptamine derivative, giving, after deprotection, 2-hydroxyapramycin, the first apramycin derivative functionalized at the 2 position.

The utilization of high-valent metal catalysts to promote cycloaddition reactions involving π bonds through C-C bond activation remains challenging. Despite extensive research, the cycloaddition of aldehydes with cyclopropenones catalyzed by metal complexes has not been documented. Herein, we disclose a novel Rh(III)-catalyzed cycloaddition reaction between cyclopropenones and aldehydes, enabling the efficient synthesis of highly functionalized furanones. A detailed mechanistic investigation was conducted, revealing the likely involvement of a tripodal Rh-carbene intermediate in the catalytic cycle, which facilitates the product release pathway. This reaction exhibits a broad substrate scope, good functional group compatibility, and high atom economy, thereby offering a versatile and general approach to the construction of furanones.

Herein, we developed the new, powerful, and easy-to-handle chemical reagent, dimethoxyacetaldehyde-N-triftosylhydrazone (DMHz-Tfs), as a convenient in situ source of dimethoxydiazoethane under mild conditions. We demonstrate the carbene reactivity of DMHz-Tfs in iron-catalyzed cyclopropanation and Doyle-Kirmse reactions, providing access to diverse acetal functionalized cyclopropanes and homoallylic- and allenyl-sulfides at gram-scale with high stereoselectivity. DFT calculations elucidated the involvement of the most stable doublet spin state iron-carbene intermediate over other possible spin states.

By means of simple Rh catalysis, the direct activation of the ortho-C-H bond in aryl enaminones has been realized with the enaminone structure as a traceless directing fragment. The products resulting from C-H alkenylation and further annulation via intramolecular C-H bond addition could be accessed depending upon the structure of alkenes. The annulated products could be used for the easy synthesis of valuable 2-aza-fluorenones in a one-pot operation by employing NH₄OAc.

Coumarin skeletons are significant structural units frequently used in the fields of synthetic chemistry, medicinal chemistry, and materials science. Herein, we report a hemilabile P,N-ligand-assisted gold-catalyzed difunctionalization of activated alkynes with organohalides. The reaction occurs effectively under mild conditions without requiring an external oxidant, producing a variety of 3-arylated and alkenylated coumarin derivatives in high to excellent yields. This method demonstrates a wide substrate tolerance and superb functional group compatibility and is also suitable for heteroaromatic substrates. Further mechanistic investigations strongly support the proposed mechanism of the reaction.