Access to Polysubstituted (Furyl)methylthioethers via a Base-Promoted S-H Insertion Reaction of Conjugated Enynones

Spirocyclopropanes and Substituted Furans by Controlling Reactivity of 1,3-Enynoates: γ- and δ-Addition of Phosphines to Conjugate Acceptors

In the Morita-Baylis-Hillman (MBH) reaction, a nucleophile undergoes β-addition to activated alkenes or alkynes, forming reactive intermediates for subsequent carbon-carbon or carbon-hetero bond formation. By using a π-conjugated acceptor, however, an unprecedented reactivity of 1,3-enynoates and indane-1,3-diones was uncovered in the presence of phosphines. When indan-1,3-diones were used, γ-addition of phosphines to 1,3-enynoates was observed for the first time; moderate to good yields were obtained for 14 substances containing the prominent spirocyclopropane scaffold with 100 % retention of (Z)-alkene. When 2-methyl-indan-1,3-diones were used, di(tri)-substituted furans were produced through the δ-addition pathway, with 20 substances and a yield of up to 88 % being achieved. Control experiments and density functional theory calculations were conducted to obtain insights into the unconventional γ-addition reaction pathway.

Copper-Catalyzed Radical Sulfonylation: Divergent Construction of C(sp3)-Sulfonyl Bonds with Sulfonylhydrazones

Sulfonylhydrazones have been proven to be versatile synthetic intermediates in a panel of transformations. However, radical sulfonylation with sulfonylhydrazone as sulfonyl radical source is relatively rare. Here, we found that sulfonylhydrazone can serve as a new sulfonyl radical precursor to couple various partners such as arylacetic acids, ene-yne-ketones, and para-quinone methides under copper catalysis and microwave irradiation. The reactions of sulfonyl radicals have been successively developed to enable the divergent synthesis of C(sp3)-sulfonyl bonds. In addition, when alkynes and alkenes are used as radical receptors, this method can also promote the formation of C(sp2)-sulfonyl bonds. This finding suggests that sulfonylhydrazone could be regarded as a potentially useful sulfonyl radical in sulfone synthesis.

Manganese-Promoted Cyclization Reaction of Enynones with Tetrasulfides: Synthesis of Multisubstituted Furanmethyl Disulfides

A tandem cyclization reaction of enynones with tetrasulfides has been developed under manganese-promoted conditions, leading to the high-yield formation of various furanmethyl disulfides. This reaction is characterized by readily available starting materials, mild reaction conditions, and a broad substrate scope, making it attractive and practical. It provides a new strategy for the synthesis of disulfide-containing functionalized furans.

Synthesis of (Furyl)Methyl Disulfides via Tandem Reaction of Conjugated Ene-Yne-Ketones with Acetyl-Masked Disulfide Nucleophiles

In this study, we outline a general method for the construction of various (furyl)methyl disulfides from acetyl-masked disulfide nucleophiles and ene-yne-ketones. This protocol is feathered by metal-free, simple experimental conditions, high efficiency, and scalable potential, which make it attractive and practical.

Cu-Catalyzed tandem cyclization and coupling of enynones with enaminones for multisubstituted furans & furano-pyrroles

A synthetic strategy that efficiently constructs complex molecular diversity in a few steps will always be embraced by organic chemists. Here, we report a cascade reaction of enynones with enaminones via carbene insertion and aryl migration to engineer distinctive multisubstituted furans with an all-carbon quaternary center, and could extend the protocol in the same pot towards furano-pyrrole bis-heterocycles. Heterogeneity of this protocol was proved with the upshot of divergent chemical space under a relatively mild reaction environment.

Palladium-catalyzed acetalization/cyclization of enynones with alcohols: rapid access to functionalized dihaloalkenyl dihydrofurans

A novel Pd-catalyzed acetalization/cyclization of enynones and alcohols for the construction of dihaloalkenyl dihydrofuran derivatives is described.

Copper(II)-Catalyzed Domino Synthesis of 4-Benzenesulfonyl Isoxazoles from 2-Nitro-1,3-enynes, Amines, and Sodium Benzenesulfinate

A simple and effective method for the synthesis of fully substituted 4-benzenesulfonyl isoxazoles through a copper(II)-catalyzed three-component reaction of 2-nitro-1,3-enynes, amines, and sodium benzenesulfinate is described. The reaction proceeds smoothly under mild conditions and provides the benzenesulfonyl isoxazoles with high chemoselectivity.

BF3·OEt2-mediated cyclization of β,γ-unsaturated oximes and hydrazones with N-(arylthio/arylseleno)succinimides: an efficient approach to synthesize isoxazoles or dihydropyrazoles

A highly efficient BF3·OEt2-mediated cyclization of β,γ-unsaturated oximes and tosylhydrazones with N-(arylthio/arylseleno)succinimides has been established for the construction of N-heterocycles in a one-step manner. This metal-free cyclization provides direct access to isoxazoles and dihydropyrazoles in good to excellent yields at room temperature. The mechanistic experiments support the formation of a cationic species PhS+ which plays a critical role in this cyclization process.