Expedient Synthesis of Substituted Thieno[3,2-]thiophenes and Selenopheno[3,2-]selenophenes Through Cascade Cyclization of Alkynyl Diol Derivatives.

Thieno[3,2-]thiophenes are used as key components in optoelectronic materials, porous hydrogen-storage hosts, organic solar cells, and polymer semiconductors. A step-efficient synthetic protocol was proposed herein for obtaining multisubstituted thieno[3,2-]thiophene and selenopheno[3,2-]selenophenes in moderate to good yields via the bisulfur/biselenium cyclization of alkynyl diols with I/NaSO or selenium. Using this strategy, substitution patterns were obtained for backbone modification in functional materials.

Silver-Mediated Acetoxyselenylation of Alkynes: Mild Stereoselective Access to Bifunctional Alkenes.

Herein, we report a AgF-mediated regio- and stereoselective acetoxyselenylation of terminal/internal alkynes from iodobenzene dicarboxylate [PhI(OCOR)] and diorganyl diselenides via multiple-site functionalization to afford β-selenyl enol esters in good yields. Alkynes derived from bioactive molecules, such as l(-)-borneol, l-menthol, and acyne oxalate, are also suitable for this transformation and afford the expected compounds.

Synthesis of Dihalonaphthalenes via Silver-Catalyzed Halogenation and Electrophilic Cyclization of Terminal Alkynols.

Herein, we report a silver-catalyzed halogenation and electrophilic cyclization reaction based on the trifunctionalization of terminal alkynols with NBS or iodine monochloride in a step-efficient synthetic way to produce homo/heterodihalogenated naphthalene derivatives bearing two different halogen atoms in moderate to good yields. This methodology readily accommodates various functional groups, including electron-withdrawing nitro, cyano, acid-sensitive dioxazolyl, and alkoxy groups.

Expedient Synthesis of Alkyl and Aryl Thioethers Using Xanthates as Thiol-Free Reagents.

Thioethers are critical in the fields of pharmaceuticals and organic synthesis, but most of the methods for synthesis alkyl thioethers employ foul-smelling thiols as starting materials or generate them as by-products. Additionally, most thiols are air-sensitive and are easily oxidized to produce disulfides under atmospheric conditions; thus, a novel method for synthesizing thioethers is necessary. This paper reports a simple, effective, green method for synthesizing dialkyl or alkyl aryl thioether derivatives using odorless, stable, low-cost ROCSK as a thiol surrogate.

Chemoselective Synthesis of α-Halo--difluoromethyl Ketones from Trimethyl(phenylethynyl)silane.

Here, we describe a novel strategy for chemoselective synthesis of α-halo--difluoromethyl ketones (-COCF and -COClCF motifs) from trimethyl(phenylethynyl)silane under catalyst-free and mild conditions. Commercially available Selectfluor or additional NaCl as halogen reagent was employed to complete this transformation, thereby demonstrating the potential synthetic value of this new reaction in organic synthesis.

Electrochemically Driven para-Selective C(sp)-H Alkylation Enabled by Activation of Alkyl Halides without Sacrificial Anodes.

With alkyl halides (I, Br, Cl) as a coupling partner, an electrochemically driven strategy for para-selective C(sp)-H alkylation of electron-deficient arenes (aryl esters, aldehydes, nitriles, and ketones) has been achieved to access diverse alkylated arenes in one step. The reaction enables the activation of alkyl halides in the absence of sacrificial anodes, achieving the formation of C(sp)-C(sp) bonds under mild electrolytic conditions. The utility of this protocol is reflected in high site selectivity, broad substrate scope, and scalable.

Selective Access to Functional Fluoroenones via Palladium-Catalyzed Selenofluoroalkylacylation of Terminal Alkynes.

The trifluoromethylacyl group (-COCF) is an important motif and widely studied in catalysis, medicinal chemistry, and materials science. Herein, a novel palladium-catalyzed selenofluoroalkylacylation of terminal alkynes with commercially available fluoroalkyl anhydride and diorganyl diselenides to afford β-seleno and aryl/alkyl disubstituted enones under mild conditions is disclosed. In addition, selenodifluoroacetylations and selenoperfluoroacetylations are also suitable for this reaction.

Potassium xanthate-promoted reductive sulfuration reaction: from aldehydes to thiol, disulfide, and thioester derivatives.

Herein, we developed a synthetic strategy for the direct construction of C-S bonds to obtain biologically active sulfur-containing compounds and a methodology involving the reductive sulfuration of aldehydes or ketones to obtain diverse substituted thiol, disulfide, and thioester derivatives. EtOCSK is demonstrated as a potential substitute for the Berzelius reagent or Lawesson's reagent for the construction of C-S bonds.

Electrochemically Driven C4-Selective Decyanoalkylation of Cyanopyridines with Unactivated Alkyl Bromides Enabling C(sp)-C(sp) Coupling.

With cyanopyridines and alkyl bromides as coupling partners, an electrochemically driven C4-selective decyanoalkylation has been established to access diverse 4-alkylpyridines in one step. The reaction proceeds through the single electron reduction/radical-radical coupling tandem process under mild electrolytic conditions, achieving the cleavage of the C(sp)-CN bond and the formation of C(sp)-C(sp). The practicality of this protocol is illustrated by no sacrificial anodes, a broad substrate scope, and gram-scale synthesis.

Ru(OAc)-Catalyzed Regioselective Difunctionalization of Alkynes: Access to ()-2-Bromo-1-alkenyl Sulfonates.

A new approach is proposed for the divergent and regioselective synthesis of ()-2-bromo-1-phenylvinyl trifluoromethanesulfonates through alkyne difunctionalization by employing a compatible system of abundantly available alkynes, -bromosuccinimide (NBS), and trimethylsilyl trifluoromethanesulfonate (TMSOTf) catalyzed by ruthenium(III) acetate [Ru(OAc)]. It is a novel method for the preparation of vinyl triflate and it offers a fundamental basis for the development of advanced functional compounds, including drugs and organic functional materials. Unlike previously reported methods, the proposed protocol can tolerate a broad range of functional groups.

Aromatization of cyclic hydrocarbons thioether elimination reaction.

Herein, the diversity-oriented aromatization of cyclic hydrocarbons potassium ethyl xanthogenate (EtOCSK)/NHI-mediated methylthiyl radical addition and thioether elimination was investigated under transition-metal-free conditions. The methylthiyl radical species were generated the NHI-mediated decomposition of DMSO following which EtOCSK promoted the breaking of carbon-sulfur bonds of thioether.

Expedient Synthesis of Dihaloalkenynes via Pd-Catalyzed Haloalkynylation Reaction.

Herein, the Pd -catalyzed construction of functionalized dihaloalkenynes from haloalkynes via a self-haloalkynylation reaction, without specialized ligands or oxidizing additives, is reported. The method tolerates a diverse range of haloalkynes, including electron-donating and electron-withdrawing functional groups, such as macrocyclic alkynols, spiro-oxy ring alkynols, and even carbazole-containing, pyrrolidine-2,5-dione-containing and silyl-protected bromoalkynes. Using an opposite lithium halide (LiX) to the haloalkyne starting material, remarkably high regio- and stereoselectivity of the haloalkynylation reaction is possible, yielding 1-bromo-2-chloroalkenyne or 2-bromo-1-chloroalkenyne products as desired.

Cathodic Carbonyl Alkylation of Aryl Ketones or Aldehydes with Unactivated Alkyl Halides.

An efficient cathodic carbonyl alkylation of aryl ketones or aldehydes with unactivated alkyl halides has been realized through the electrochemical activation of iron. The protocol is believed to include a radical-radical coupling or nucleophilic addition process, and the formation of ketyl radicals and alkyl radicals has been demonstrated. The protocol provides various tertiary or secondary alcohols by the formation of intermolecular C-C bonds under safe and mild conditions, is scalable, consumes little energy, and exhibits a broad substrate scope.

Construction of Spirocyclic Pyrrolo[1,2-]quinoxalines via Palladium-Catalyzed Hydrogenative Coupling of Phenols and Nitroarenes.

The replacement of fossil resources with biomass resources in the construction of N-heterocycles is rapidly attracting research interest. Herein, we report palladium-catalyzed selective hydrogenative coupling of nitroarenes and phenols based on a transfer hydrogenation strategy, allowing straightforward access to spirocyclic pyrrolo- and indolo-fused quinoxalines, a class of compounds found in numerous natural alkaloids. The synthetic protocol is characterized by a broad substrate scope and the utilization of biomass-derived reactants and commercially available catalysts.

Ruthenium-Catalyzed Regioselective Hydrohalogenation of Alkynes Mediated by Trimethylsilyl Triflate.

Here we describe a ruthenium-catalyzed regioselective hydrohalogenation reaction of alkynes under mild conditions. Commercially simple halogen sources such as KI, ZnBr, and ZnCl were employed to achieve this transformation. Alkynes derived from bioactive molecules such as l-(-)-borneol, l-menthol, and estrone were also suitable for the transformation, demonstrating the potential synthetic value of this new reaction in organic synthesis.

Electrochemically induced Markovnikov-type selective hydro/deuterophosphonylation of electron-rich alkenes.

The regioselective hydro/deuterophosphonylation of electron-rich alkenes with P(O)H compounds has been realized a metal-free electrochemically induced strategy, accessing various Markovnikov-type adducts in high yields. A series of monodeuterated organophosphorus compounds with high deuterium (D) incorporation are subsequently obtained by adding DO as the D source. The protocol features broad substrate scope, low energy consumption, high atom economy, and scalability.

Optimization of Artistic Image Segmentation Algorithm Based on Feed Forward Neural Network under Complex Background Environment.

Based on the theory and application, this paper discusses the optimization of art image segmentation algorithm based on FFNN (Feed Forward Neural Network). In this paper, residual units are used in the corresponding stages of encoder and decoder, and feature information of several convolution layers in each convolution stage of encoder is extracted at the same time. And the feature pyramid module is used to extract multiscale features from the feature map of the last convolution stage in the encoder.

Palladium-Catalyzed Cross Haloalkynylation of Haloalkynes.

Herein, we have developed a robust Pd-catalyzed haloalkynylation of haloalkynes for the synthesis of dihaloalkenyne derivatives. This cross-haloalkynylation reaction proceeds in a highly chemo- and regioselective manner under mild conditions in the presence of two slightly structurally different haloalkynes and shows strong functional group tolerance under ligand- and base-free conditions.

Access to Thienopyridine and Thienoquinoline Derivatives via Site-Selective C-H Bond Functionalization and Annulation.

To develop of an effective synthetic methodology for biologically relevant thienopyridines, a concise and efficient protocol is described for the synthesis of a series of substituted thienopyridine and thienoquinoline derivatives with high selectivity using EtOCSK as the sulfur source. The reaction proceeds via metal-free, site-selective C-H bond thiolation and cyclization of the alkynylpyridine and alkynylquinoline substrates.

Manganese-Catalyzed Asymmetric Hydrogenation of 3H-Indoles.

The asymmetric hydrogenation (AH) of 3H-indoles represents an ideal approach to the synthesis of useful chiral indoline scaffolds. However, very few catalytic systems based on precious metals have been developed to realize this challenging reaction. Herein, we report a Mn-catalyzed AH of 3H-indoles with excellent yields and enantioselectivities.

Selective Synthesis of Substituted Pyridines and Pyrimidines through Cascade Annulation of Isopropene Derivatives.

Diverse substituted pyridines and pyrimidines with high selectivity were obtained using a concise and efficient protocol developed herein. The reaction proceeds via metal-free cascade annulation of isopropene derivatives. Using isopropene derivatives as C3 synthons, NHI as the "N" source, and formaldehyde or dimethyl sulfoxide as the carbon source, this reaction realizes the efficient formation of intermolecular C-N and C-C bonds.

Synthesis of Substituted Thiophenes through Dehydration and Heterocyclization of Alkynols.

A protocol was described for obtaining a variety of substituted thiophenes with functional potential metal-free dehydration and sulfur cyclization of alkynols with elemental sulfur (S) or EtOCSK in moderate-to-good yields. The method provides the base-free generation of a trisulfur radical anion (S) and its addition to alkynes as an initiator. This research broadens the applications of S in the synthesis of sulfur-containing heterocycles.

Cathodic Regioselective Coupling of Unactivated Aliphatic Ketones with Alkenes.

A regioselective coupling of aliphatic ketones with alkenes has been realized by cathodic reduction. This reaction enables the formation of ketyl radicals and the activation of challenging alkenes under mild electrolysis conditions, providing an effective protocol for accessing diverse tertiary alcohols with substrate-dependent regioselectivity. The practicability of this reaction is demonstrated by scale-up experiments.

Layered Double Hydroxides as Reusable Catalysts for Cyclocondensation of Amidines and Aminoalcohols: Access to Multi-functionalized Oxazolines.

An efficient catalytic protocol based on reusable MgAl-layered double hydroxides has been developed for the synthesis of multi-functionalized oxazolines via the cyclocondensation of amidines and aminoalcohols. The developed method has a broad substrate scope and excellent functional group tolerance and uses a reusable catalyst. The catalyst can be conveniently recycled by filtration and reused for at least five times without obvious deactivation.