A Convenient and Efficient Route to 1,4-Bis（heteroaryl）-buta-1,3-diene and 4-Heteroarylbut-1-en-3-yne from 1,4-Dichlorobut-2-yne

A convenient and practical route to functionalized conjugated 1,3-enynes and 1,3-dienes is described. 1,4-Bis（heteroaryl）- 1,3-diene and 1-heteroarylbut- 1-en-3-yne derivatives were prepared from 1,4-dichloro-2-butyne and corresponding N-heteroarenes such as imidazole, pyrrole, pyrazole and indole derivatives in the presence of bases in good to high yields.     

Regiodivergent sulfonylarylation of 1,3-enynes via nickel/photoredox dual catalysis

Catalytic difunctionalization of 1,3-enynes represents an efficient and versatile approach to rapidly assemble multifunctional propargylic compounds, allenes and 1,3-dienes. Controlling selectivity in such addition reactions has been a long-standing challenging task due to multiple reactive centers resulting from the conjugated structure of 1,3-enynes. Herein, we present a straightforward method for regiodivergent sulfonylarylation of 1,3-enynes via dual nickel and photoredox catalysis. Hinging on the nature of 1,3-enynes, diverse reaction pathways are feasible: synthesis of α-allenyl sulfones via 1,4-sulfonylarylation, or preparation of (E)-1,3-dienyl sulfones with high chemo-, regio- and stereoselectivity through 3,4-sulfonylarylation. Notably, this is the first example that nickel and photoredox catalysis are merged to achieve efficient and versatile difunctionalization of 1,3-enynes.

A mild reaction protocol for regiodivergent sulfonylarylation of 1,3-enynes via dual nickel and photoredox catalysis has been developed, which led to efficient synthesis of α-allenyl sulfones or 1,3-dienyl sulfones.     

The Studies of Free Radical Cyclization Reactions Mediated by Sulfonyl Chloride (II)

A study on the free radical cyclization reaction of substituted 1,6-dienes mediated by p-toluenesulfonyl chloride is described.     

Palladium-catalyzed one-pot construction of difluorinated 1,3-enynes from α,α,α-iododifluoroacetones and alkynes

A palladium-catalyzed one-pot difunctionalization of alkynes with α,α,α-iododifluoroacetones is introduced for the synthesis of difluorinated 1,3-enynes. The reaction proceeds through the radical addition of RCOCF₂ radical to alkynes and subsequent Sonogashira coupling with the same alkynes to give the 1,3-enyne products with high regio and stereoselectivity.     

Recent applications of radical cascade reaction in the synthesis of functionalized 1-indenones

1-Indenones are important scaffolds in natural products, biologically active molecules as well as functional materials. Recently, radical cascade cyclization has emerged as an efficient and powerful strategy for the construction of valuable and versatile functionalized 1-indenones. In this review, the recent advances of this rapidly growing area were summarized. The selected examples have been classified according to the type of reaction substrates such as 1,3-diarylpropynones, 2-alkynylbenzonitriles, arylpropynols, 1,5-enynes and 2-alkynylated bromocinnamates.     

3,3,3-trichloropropyl-1-triphenylphosphorane: a reagent for the synthesis of (Z)-1,3-enynes, (Z,Z)-1-chloro-1,3-dienes, and 1,3-diynes

3,3,3-Trichloropropyl-1-triphenylphosphonium chloride is conveniently prepared from 2-chloroethanol, triphenylphosphine, and trichloroacetic acid. Deprotonation of this reagent generates 3,3,3-trichloropropyl-1-triphenylphosphorane, which reacts with aldehydes to give trichloromethylated (Z)-olefins, which are useful for the synthesis of (Z)-1,3-enynes, (Z,Z)-1-chloro-1,3-dienes, and 1,3-diynes in high yields and stereospecificities.     

Electroreductive Dicarboxylation of Unactivated Skipped Dienes with CO2

Carboxylation of easily available alkenes with CO₂ is highly important to afford value-added carboxylic acids. Although dicarboxylation of activated alkenes, especially 1,3-dienes, has been widely investigated, the challenging dicarboxylation of unactivated 1,n-dienes (n>3) with CO₂ remains unexplored. Herein, we report the first dicarboxylation of unactivated skipped dienes with CO₂ via electrochemistry, affording valuable dicarboxylic acids. Control experiments and DFT calculations support the single electron transfer (SET) reduction of CO₂ to its radical anion, which is followed by sluggish radical addition to unactivated alkenes, SET reduction of unstabilized alkyl radicals to carbanions and nucleophilic attack on CO₂ to give desired products. This reaction features mild reaction conditions, broad substrate scope, facile derivations of products and promising application in polymer chemistry.     

Intramolecular Vinyl Radical Cyclization Reactions of cyclohexadienes derived from sequential additions to (arene)(tricarbonyl)chromium complexes. Preliminary communication

Cyclohexa-1,3-dienes 7–10 with a 1,5,6-substitution pattern were prepared in a one-pot reaction sequence by sequential addition of MeLi and propargyl bromides to the tricarbonylchromium complex 1a . These products were subjected to radical cyclization procedures. Vinyl radical generation by Bu₃Sn addition to the propargyl group in 7–10 was followed by regio- and diastereoselective intramolecular ring closure. Two different 5-exo-trig cyclizations are possible via different vinyl radical intermediates and cyclization to one or the other of the termini of the cyclohexadiene moiety. Internal alkynes reacted to yield exclusively the cis-fused hexahydroindene products 12–14 , whereas the terminal alkyne yielded bicyclo[3.2.1]octenes 11 as sole products.     

Copper-catalyzed asymmetric silylative cyclization of cyclohexadienone-containing 1,6-enynes

The first copper-catalyzed asymmetric silylative cyclization of cyclohexadienone-containing 1,6-enynes has been accomplished through a tandem process: regioselective silylcupration of terminal unactivated alkynes and subsequently enantioselective conjugate addition to cyclohexadienones. This reaction proceeded smoothly to afford the cis-hydrobenzofuran and cis-hydroindole frameworks bearing two consecutive chiral carbon centers in high to excellent yields and moderate enantioselectivities. Additionally, the cyclization products could be readily subjected to several transformations for elaborating synthetic utilities.     

The Free-Radical Cyclization Reaction of 1, 6-Dienes with Selenosulfonate

A sulfonyl radical induced addition-cyclization reaction of 1, 6-dienes with p-tolyl benzeneselenosulfonate giving functionalized cyclopentane system is described.     

Cyclization of 1-bromo-2,7- and 1-bromo-2,8-enynes mediated by indium

[reaction: see text] The cyclization of 1-bromo-2,7- and 1-bromo-2,8-enynes mediated by indium in DMF produced five- and six-membered cyclic compounds. Although KI was a necessary additive in the cyclization of terminal 1-bromo-2,7-enynes to give the desired products at 25 degrees C, reactions of terminal 1-bromo-2,8-enynes and internal 1-bromo-2,7-enynes with indium proceeded at 100 degrees C in DMF without KI. After cyclizations, subsequent cross-coupling reaction and iodolysis increase the usefulness of this reaction.     

A new stereospecific cross-coupling by the palladium-catalyzed reaction of 1-alkenylboranes with 1-alkenyl or 1-alkynyl halides

The representative (E)-1-alkenyldisiamylboranes and (E)-1-alkenyl-1,3,2-benzodioxaboroles readily obtainable $\text{via}$ hydroboration of 1-alkynes react with 1-alkenyl halides or 1-alkynyl halides in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium and base to give corresponding conjugated (E)-dienes or (E)-enynes with high regio- and stereospecificity in good yields, respectively.     

1‐Phosphabicyclo[3.2.1]octane

1‐Phosphabicyclo[3.2.1]octanes 1‐Phosphabicyclo[3.2.1]octane has been obtained by free‐radical cyclization of (2‐vinyl‐4‐pentenyl)‐phosphane in the presence of AIBN. Another approach to 1‐phosphabicyclo[3.2.1]octanes involves free‐radical cyclization of 2‐methyl‐4‐(2‐propenyl)‐phospholane synthesized by the reaction of [2‐(2‐propenyl)‐4‐pentenyl]‐phosphane with KPH₂/[18]crown‐6 in THF. The bicyclic phosphanes are characterized by reactions with CS₂, selenium, sulfur, NO, CH₃I, and HSO₃F, respectively, structural and analytical data as well as ¹H, ¹³C, ³¹P, ⁷⁷Se NMR spectral measurements. The steric crowding of the phosphanes as complex ligands has been estimated from ³¹P–¹H coupling constants according to the Tolman model. The configuration of the methyl substituents as well as the conformation of the six‐membered ring were determined by NMR parameters (coupling constants, noe's) and proved by X‐ray crystal structure analysis.     

Time and Atom Economical Regio- and Chemoselective Radical Cyclization of Unactivated 1,6-Enynes Under Metal- and Oxidant-Free Conditions

We developed time-atom economic regio- and chemoselective sulfonyl radical triggered 5-exo-dig cyclization of unactivated 1,6-enynes with sulfonyl halides under metal, additive-free reaction conditions to achieve highly substituted five-membered heterocyclic compounds. This transformation creates three new bonds, such as C−SO₂, C−C, and active C−I/Br bonds. Importantly, one-pot protocols produce desired products directly from sodium sulfinates and have an additional advantage such as minimising chemical waste, saving time, and simplifying practical aspects compared to existing protocols.     

Radical cascade reaction with 1,4-dienes and 1,4-enynes using 2-(iodomethyl)cyclopropane-1,1-dicarboxylate as a homoallyl radical precursor: one-step synthesis of bicyclo[3.3.0]octane derivatives

[reaction: see text] Radical cascade reaction with various 1,4-dienes and 1,4-enynes using dimethyl 2-(iodomethyl)cyclopropane-1,1-dicarboxylate as a homoallyl radical precursor smoothly proceeds through an iodine atom transfer mechanism to give functionalized bicyclo[3.3.0]octane derivatives in good yields.     

Diastereoselective Synthesis of Polysubstituted Piperidines through Visible-Light-Driven Silylative Cyclization of Aza-1,6-Dienes: Experimental and DFT Studies

A visible-light-driven radical silylative cyclization of aza-1,6-dienes featuring an acrylonitrile or acrylate moiety and an electron-neutral olefin was developed, which allows for stereoselective synthesis of densely functionalized piperidines in a highly atom-economical manner. Depending on the substitution pattern of the electron-neutral olefin, poor-to-excellent diastereoselectivity was observed. It was suggested that the 6-exo-trig cyclization was initiated by a chemoselective addition of silyl radical toward electron-deficient olefin and the geometry of the remaining olefin is closely associated with the cis-stereoselectivity. DFT calculations supported that a transition state with a cyano group locating at the axial position of the forming piperidine ring might be involved, in which either the increase of 1,3-diaxial repulsion or the lack of hydrogen bonding interaction will diminish diastereoselectivity.     

Rapid Interception of CnF2n+1(O)SO. Radical with Copper-Based Carbene: A Novel Access to Perfluoroalkanesulfinate Ester

In this communication, an unprecedented interception of C_nF_2n+1(O)SO^. radical with a copper-based carbene has been established. Distinguished by wide substrate scopes and mild reaction conditions, this novel radical–carbene coupling reaction (RCC reaction) provides a fundamentally different and mechanistically interesting strategy for the synthesis of perfluoroalkanesulfinate esters.     

Palladium-catalyzed asymmetric hydrosilylation of 1,3-dienes

Advances in the palladium-catalyzed asymmetric hydrosilylation of 1,3-dienes are presented according to substrate types and chiral monophosphine ligands. Chiral monodentate phosphine ligands with a binaphthyl moiety have been proven to be the most efficient ligands for cyclic 1,3-dienes, and planar chiral ferrocenylmonophosphine ligands with two ferrocenyl moieties for linear 1,3-dienes. The ferrocenylmonophosphine ligands have expanded the substrate scope to 1,3-enynes in the asymmetric hydrosilylation. Palladium-catalyzed asymmetric hydrosilylation of 1,3-dienes and 1,3-enynes leads to the stereoselective synthesis of allylsilanes and allenylsilanes, respectively.     

Scalable Total Synthesis of rac‐Jungermannenones B and C

Reported is the first scalable synthesis of rac‐jungermannenones B and C starting from the commercially available and inexpensive geraniol in 10 and 9 steps, respectively. The unique jungermannenone framework is rapidly assembled by an unprecedented regioselective 1,6‐dienyne reductive cyclization reaction which proceeds through a vinyl radical cyclization/allylic radical isomerization mechanism. DFT calculations explain the high regioselectivity observed in the 1,6‐dienyne reductive radical cyclization.     

Reductive activation of arenes

Reductive alkylation of benzonitrile, ortho-, meta-, para-tolunitriles, and 1-naphthonitrile by sequential action of alkali metal and alkyl bromide in liquid ammonia results in corresponding alkylarenes and 1-alkyl-1-cyanocyclohexa-2,5-dienes. The experimental conditions for target synthesis of the specified products are found. A method of synthesis of 1-(ω-bromoalkyl)-1-cyanocyclohexa-2,5-dienes based on the interaction of two-electronic reduction products of aromatic nitriles with α,ω-dibromoalkanes Br(CH₂)_nBr (_n = 3−5) is developed.