Synthesis of highly substituted furans by the electrophile-induced coupling of 2-(1-alkynyl)-2-alken-1-ones and nucleophiles

[reaction: see text] The coupling of 2-(1-alkynyl)-2-alken-1-ones with nucleophiles, either catalyzed by AuCl3 or induced by an electrophile, provides highly substituted furans in good to excellent yields under very mild reaction conditions. Various nucleophiles, including functionally substituted alcohols, H2O, carboxylic acids, 1,3-diketones, and electron-rich arenes, and a range of cyclic and acyclic 2-(1-alkynyl)-2-alken-1-ones readily participate in these cyclizations. Iodine, NIS, and PhSeCl have proven successful as electrophiles in this process. The resulting iodine-containing furans can be readily elaborated to more complex products using known organopalladium chemistry.     

Cu(I) catalyst in DMF: an efficient catalytic system for the synthesis of furans from 2-(1-alkynyl)-2-alken-1-ones

The cyclization of 2-(1-alkynyl)-2-alken-1-ones 1 proceeded very smoothly in the presence of alcohols 2 with a catalytic amount of Cu(I)Br in DMF at 80 degrees C, leading to the formation of highly substituted furans 3. The catalytic system reported herein is easy to handle, compared to the previously known system wherein the reaction between 1 and 2 needed to use moisture sensitive gold(III) chloride.     

Electrophilic cyclization of 2-(1-alkynyl)-2-alken-1-ones using the I2/K3PO4 system: an efficient synthesis of highly substituted iodofurans

[reaction: see text] The electrophilic cyclization of 2-(1-alkynyl)-2-alken-1-ones in the presence of various alcohols or carbon-based nucleophiles offers an efficient and straightforward route to highly substituted iodofurans under extremely mild reaction conditions. The iodo derivatives are potential synthetic intermediates for amplification of molecular complexity.     

Gold(I)-catalyzed synthesis of highly substituted furans

Cationic triphenylphosphinegold(I) complexes are excellent catalysts for a cascade reaction of propargyl-Claisen rearrangement and heterocyclization to synthesize tri- and tetrasubstituted furans. Starting from easily accessed propargyl vinyl ethers, the furans are obtained in 72-99% yield. [reaction: see text]     

An efficient synthesis of highly substituted furans via the electrophilic cyclization of 1-(1-alkynyl)-cyclopropyl ketones

The electrophilic cyclization of 1-(1-alkynyl)-cyclopropyl ketones offers an efficient and straightforward route to highly substituted furans under extremely mild reaction conditions. Iodine, NIS, and PhSeBr have proven successful as electrophiles in this process.     

AuCl3催化2-(1-炔基)-2-烯基酮合成多取代呋喃的机理

采用密度泛函理论的B3LYP泛函对AuCl₃催化的2-(1-炔基)-2-烯基酮与亲核试剂反应的机理进行了研究, 得到了反应的最优路径. 结果表明, 整个反应的决速步骤是羟基H转移到AuCl₃的配体Cl上, 其活化能为49.3 kJ·mol^-1. 通过计算发现, 催化剂AuCl₃的配体Cl原子在反应中有重要的作用, 它不仅稳定配合物, 而且直接参与反应, 协助质子的转移, 显著降低质子转移的活化能(由71.5 kJ·mol^-1降低到49.3 kJ·mol^-1). 另外还讨论了HBF₄不能催化此反应的可能原因, 计算结果与实验结果一致.     

Chemoselective synthesis of highly substituted 1,2-allenyl ketones, furans, and 2-alkynyl ketones from reaction of lithium selenolates with 1-(1-alkynyl)cyclopropyl ketones and electrophiles

A homo-Michael addition reaction of lithium selenolates with 1-(1-alkynyl)cyclopropyl ketones and the subsequent reaction with electrophiles such as PhSeBr, NFSI and NCS is reported. Based on the nature of electrophiles, this reaction may afford highly substituted 1,2-allenyl ketones or furans (E(+) = PhSe(+)) and 2-alkynyl ketones (E(+) = F(+), Cl(+), active halides) as the final products, respectively.     

Tetrasubstituted furans by Pd(II)/Cu(I)-cocatalyzed three-component domino reactions of 2-(1-alkynyl)-2-alken-1-ones, nucleophiles and diaryliodonium salts

A novel Pd(OAc)(2)/CuI-cocatalyzed three-component reaction of 2-(1-alkynyl)-2-alken-1-ones, nucleophiles and diaryliodonium salts has been developed. The procedure allows the synthesis of tetrasubstituted furans in good to high yields under mild conditions.     

The reaction of 3-(1-imidazolyl)-2-alken-1-ones with nucleophiles

Generally 3-hetero-substituted 2-alken-1-ones were prepared from 1,3-alkanediones, 3-chloro-2-alken-1-ones, or conjugated ynones. The preparation of 3-hetero-substituted 2-alken-1-ones was subjected to some limitations by these methods. By the reaction of 3-(1-imidazolyl)-2-alken-1-ones (I) and 3-(3-oxo-1-alkenyl)-1-methylimidazolium iodides (II) with nucleophiles, 3-hetero-substituted 2-alken-1-ones could be obtained regioselectively in good yield under mild conditions. These results suggested that compounds I and II were concluded to be useful intermediates for the organic synthesis.     

Enantioselective synthesis of highly substituted furans by a copper(II)-catalyzed cycloisomerization-indole addition reaction

A catalytic enantioselective reaction based on a copper(II) catalyst strictly containing chiral anionic ligands is described. In the present work, copper(II)-phosphate catalyst promotes the intramolecular heterocyclization of 2-(1-alkynyl)-2-alkene-1-ones and facilitates high levels of enantioselectivity in the subsequent nucleophile attack. Mechanistic studies suggest that formation of a copper(II)-indole species is important for catalysis.     

Exo/endo selectivity-control in Lewis-acid catalyzed tandem heterocyclization/formal [4+3] cycloaddition: synthesis of polyheterocycles from 2-(1-alkynyl)-2-alken-1-ones and 1,3-diphenylisobenzofuran

A novel catalytic exo/endo selectivity-controllable tandem heterocyclization/formal [4+3] cycloaddition was developed, which provides rapid, efficient and stereoselective access to highly fused polyheterocycles from readily available 2-(1-alkynyl)-2-alken-1-ones and 1,3-diphenylisobenzofuran under mild conditions.     

Palladium-catalyzed carbonylative annulation reaction of 2-(1-alkynyl)benzenamines: selective synthesis of 3-(halomethylene)indolin-2-ones

A novel and selective palladium-catalyzed carbonylative annulation process for the synthesis of 3-(halomethylene)indolin-2-ones was demonstrated. In the presence of PdX2 and CuX2, 3-(halomethylene)indolin-2-ones were selectively obtained from the carbonylative annulations of 2-(1-alkynyl)benzenamines with CO in moderate to good yields.     

Reactivities of 3-(1-Azolyl)-2-alken-1-ones and the related compounds with pyrrolidine

From the rate constants of the reaction with pyrrolidine, the reactivities of 3-(1-azolyl)-2-alken-1-ones with nucleophiles were evaluated to be rather high. Especially the reactivities of the quaternary salts of 3-(1-imidazolyl)-2-alken-1-ones were nearly equal to those of 3-chloro-2-alken-1-ones. In conclusion, 3-(1-imidazolyl)-2-alken-1-ones satisfied the practical requirements for the starting materials of the synthesis of 3-hetero-substituted 2-alken-1-ones.     

DBU-promoted cyclization of ortho-(3-hydroxy-1-alkynyl)benzamide: synthesis of trans-3,4-dihydroisoquinolin-1(2H)-ones and (E)-4-(1-alkenyl)isoquinolin-1(2H)-ones

DBU-promoted cyclization of ortho-(3-hydroxy-1-alkynyl)benzamide is presented, providing an efficient method for the synthesis of trans-3,4-dihydroisoquinolin-1(2H)-ones and (E)-4-(1-alkenyl)isoquinolin-1(2H)-ones under mild conditions.     

AuCl(3)-catalyzed benzannulation: synthesis of naphthyl ketone derivatives from o-alkynylbenzaldehydes with alkynes

The reaction of o-alkynylbenzaldehydes 1 and alkynes 2 in the presence of a catalytic amount of AuCl3 in (CH2Cl)2 at 80 degrees C gave naphthyl ketone products in high yields. The AuCl3-catalyzed formal [4 + 2] benzannulation proceeds most probably through the coordination of the triple bond of 1 to AuCl3, the formation of benzo[c]pyrylium auric ate complex via the nucleophilic addition of the carbonyl oxygen atom, the Diels-Alder addition of alkynes 2 to the auric ate complex, and subsequent bond rearrangement. Similarly, the AuCl3-catalyzed reactions of o-alkynylacetophenone and o-alkynylbenzophenone with phenylacetylene afforded the corresponding naphthyl ketone products in good yields.     

Synthesis of phosphaisoquinolin-1-ones by Pd(II)-catalyzed cyclization of o-(1-alkynyl)phenylphosphonamide monoesters

A Pd(II)-catalyzed intramolecular cyclization of o-(1-alkynyl)phenylphosphonamide monoethyl esters was examined, and a new class of six-membered phosphorus heterocycles (phosphaisoquinolin-1-ones) were formed with high regioselectivity and good yields. The present reaction is the first example of intramolecular addition of P-NH to substituted alkynes, which provides a valuable way to synthesize novel phosphorus heterocycles with potential bioactivities.