Dual gold-catalyzed regioselective synthesis of benzofulvenes via 5-endo dig cyclization

An efficient dual gold-catalyzed regioselective synthesis of benzofulvenes has been developed from substituted allyloxy 1,5-diynes via 5-endo dig cyclization. In this intramolecular organic transformation a new C-C bond formation occurs and moderate to very good yields are obtained in one pot.

Controllable C-H Alkylation of Polyethers via Iron Photocatalysis

The efficient conversion of a C-H bond in the polyether chain to other functional groups provides great opportunities for development of novel applications in many research fields. However, this field is quite underdeveloped due to the key challenge on controlling the selectivity of the C-H bond functionalization over the chain cleavage. In this work, we report a controllable C-H bond alkylation of polyethers under mild conditions via photoinduced iron catalysis. The level of functionalization could be controlled by using different amounts of alkenes and various reaction times, while the molecular weight distributions were maintained narrow. A broad scope of electron-deficient alkenes containing nitrile, ester, epoxide, terminal alkynyl, 2,5-dioxotetrafuranyl, and 2,5-dioxopyrrolidinyl groups could be utilized to functionalize the different polyethers with great efficiencies. The potential applications of the modified polyethylene glycols and polyethylene oxides were explored by the preparation of novel hydrogels and solid-state electrolytes with enhancement of lithium ion conductivities. Moreover, the density functional theory calculation disclosed the plausible mechanism and explained the high selectivity for the C-H alkylation.

Regioselective Direct C-H Phosphorylation of Benzofulvenes

A practical and straightforward protocol to access site-selective C-3 phosphorylated benzofulvenes by means of cross-dehydrogenative coupling of two nucleophilic moieties, employing silver as a promoter, is described here. Remarkably, this protocol provides a broad, structurally diverse phosphorylated benzofulvene. Initial mechanistic studies shed light on its radical coupling nature, and late-stage transformations offer highly diversified benzofulvenes core.

Direct Synthesis of Sulfinylated Benzofulvenes via BF3·Et2O-Promoted Cascade Reactions of Arylsulfinic Acids with 1,3-Enynes

A novel and efficient method for the selective synthesis of sulfinylated benzofulvenes has been developed through the BF₃·Et₂O-promoted electrophilic addition/cyclization of 1,3-enynes. This metal-free cascade reaction employs readily accessible arylsulfinic acids as sulfinyl cation sources at room temperature and provides a wide range of functionalized benzofulvenes in good to excellent yields under mild conditions.

Dataset of asymmetric intramolecular [4+3] cycloaddition reactions catalyzed by NHC-gold(I) complexes

The shared data is the unpublished portion of the experimental section for the article with the title “NHC–Au(I) catalyzed enantioselective intramolecular [4 + 3] cycloaddition of furan propargyl esters”.[1] The preparation of the intermediates for chiral NHC-gold(I) complexes and the furan propargyl ester substrates are included in this article. The ¹H NMR and ¹³C NMR spectra of the gold complexes 17a-19c and the X-ray crystal data of 17a, 18a and cycloaddition product 24 are also provided in this article or in Mendeley Data. Finally, the chiral HPLC spectra used to determine enantiomeric excess and Cartesian coordinates of the optimized structure of 25 and 26 calculated by DFT calculation are also presented in the article.

Cascade cyclization and acyl migration of propargylic esters with isocyanides: rapid access to substituted furans

A novel rearrangement of ester-activated propargylic acetate with isocyanide has been disclosed. This protocol enables a quick synthesis of polysubstituted furan derivatives.

Synthesis of functionalized pyrazole derivatives by regioselective [3+2] cycloadditions of N-Boc-α-amino acid-derived ynones

[3+2] cycloadditions of ynones derived from glycine and (S)-alanine and some other dipolarophiles with azomethine imines, nitrile oxides, diazoacetate, and azidoacetate were studied. The dipolarophiles were obtained from α-amino acids, either by the reduction of the carboxy function with ethynylmagnesium bromide or by propiolation of the amino function. Cu-catalyzed cycloadditions of ynones to azomethine imines were regioselective and gave the expected cycloadducts as inseparable mixtures of diastereomers. In some instances, further oxidative hydrolytic ring-opening took place to afford 3,3-dimethyl-3-(1H-pyrazol-1-yl)propanoic acids. Acid-catalyzed cycloadditions of 3-butenone were also regioselective and provided mixtures of diastereomeric cycloadducts, which were separated by chromatography. In the reactions of title ynones with alkyl diazoacetates, in situ-formed benzonitrile oxides, and tert-butyl azidoacetate, all cycloadducts were obtained as single regioisomers. The structures of all novel compounds were established by nuclear magnetic resonance and X-ray diffraction.

Enediynes bearing polyfluoroaryl sulfoxide as new antiproliferative agents with dual targeting of microtubules and DNA

A novel series of enediynes possessing pentafluorophenylsulfoxide have been developed. The innovative compounds possess antiproliferative activity against a broad panel of human cancer cells originating from breast, blood, lung, kidney, colon, prostate, pancreas or skin with IC₅₀ ranging from 0.6 to 3.4 μM. The antiproliferative activity of enediynes in darkness is associated to their ability to compromise microtubule network. In addition, exposure to UV leads to double-stranded DNA cleavage caused by the newly synthesized molecules reducing further their IC₅₀ in nanomolar range against human tumor cells, including chemo-resistant pancreatic cancer cells. Taken together, the examined data demonstrate that enediynes possessing pentafluorosulfoxide are promising molecules in the cancer therapy.

Organocopper triggered cyclization of conjugated dienynes via tandem SN2′/Alder-ene reaction

Propargylic carbonates were converted to indenes through a S_N2′/Alder-ene cascade triggered by organocopper reagents.

Construction of Polyarylenes with Various Structural Features via Bergman Cyclization Polymerization

Synthetic polymer chemistry is a fundamental part of polymer science, and highly efficient polymerization reactions are essential for the synthesis of high-performance polymers. Development of new synthetic methods for emerging polymer science is of great importance in this regard. Bergman cyclization is a chemical process in which highly reactive aryl diradicals form from enediyne precursors, having a strong impact in a number of fields including pharmaceutics, synthetic chemistry, and materials science. Diradical intermediates stemming from enediynes can cause DNA cleavage under physiological conditions, leading to the strong cytotoxicity of many naturally occurring enediyne antibiotics. Meanwhile, diradical intermediates can quickly couple with each other to construct polyarylenes, providing a novel method to synthesize these conjugated polymers with the advantages of facile and catalyst-free operation, high efficiency, and tailored structure. Moreover, conjugated polymers generated by Bergman cyclization exhibit many remarkable properties, such as excellent thermal stability and good solubility and processability, enabling their further processing into carbon-rich materials. This review presents a brief overview of the trajectory of Bergman cyclization in polymer science, followed by an introduction to research advances, mainly from our group, in developing polymerization methods based on Bergman cyclization, taking advantages of its catalyst-free, byproduct-free, in situ polymerization mechanism to synthesize new polymeric materials with various structures and morphologies. These synthetic strategies include fabrication of rod-like polymers with polyester, dendrimer, and chiral imide side chains, functionalization of carbon nanomaterials by surface-grafting conjugated polymers, formation of nanoparticles by intramolecular collapse of single polymer chains, and construction of carbon nanomembranes on the external and internal surface of inorganic nanomaterials. These polymers with novel structural features have been used in a variety of fields, such as energy transformation, energy storage, catalyst support, and fluorescent detection. Finally, the outlook for future developments of Bergman cyclization in polymer science is presented.

Enantioselective syntheses of indanes: from organocatalysis to C–H functionalization

The indanyl core is ubiquitous in a large variety of drugs and natural products. Remarkable recent progress has been accomplished in the step-economical assembly of functionalization of chiral indanes by means of enantioselective catalysis, with major progress being achieved in organocatalysis and C–H activation chemistry.

Platinum-Catalyzed Cascade Rearrangement Reaction of 1,5-Diynyl Esters: Unusual Regioselective 1,5-Hydride Migration

A highly regioselective sequential 1,3-acyloxy migration/pentannulation/1,5-hydride migration reaction is disclosed which provides an efficient access to (E)-2-vinyl-3-oxo-1-methyleneindenes under neutral and mild reaction conditions. The migrated hydrogen atom was derived from an unactivated alkyl group, and the long-range 1,5-H shift was confirmed through related deuterium experiments.