Visible-light-induced photoredox-catalyzed synthesis of benzimidazo[2,1-a]iso-quinoline-6(5H)-ones

A simple and efficient visible-light-induced photoredox-catalyzed diarylation of N-methacryloyl-2-arylbenzoimidazoles with aryl diazonium salts was developed. The reaction provides a convenient access to a variety of benzimidazoisoquinolinones through the construction of two CC bonds in one step under mild reaction conditions.     

Photoredox-catalyzed sulfenylation/cyclization of N-aryl-N-tosylpropargylamine with disulfide: A concise route to 3-phenylthioquinoline

A facile and novel protocol for one-pot synthesis of 3-phenylthioquinoline derivates via visible-light induced tandem cyclization of N-aryl-N-tosylpropargylamine with disulfides was developed. This unprecedented method, involving CS bond formation, detosylation and aromatization, afforded the desired products in a broad substrate scope under mild conditions.     

Visible-light-induced dearomative spirocyclization of N-benzylacrylamides toward perfluorinated azaspirocyclic cyclohexadienones

A feasible approach to 2-azaspirocyclic cyclohexadienones via visible-light-induced perfluoroalkylation cyclization of N-benzylacrylamides was reported. Using R_f-X (X = I or Br) as the R_f radical source, the reaction underwent a cascade radical addition/dearomative cyclization process by Ir photocatalyst, leading to various 2-azaspiro[4.5]deca-6,9-diene-3,8-diones bearing perfluorinated groups including CF₃, n-C₃F₇, n-C₄F₉, n-C₆F₁₃, n-C₈F₁₇, n-C₁₀F₂₁, CH₂CF₂ and CF₂CO₂Et.     

Direct synthesis of 3-arylindoles via annulation of aryl hydroxylamines with alkynes

3-Arylindoles are produced in moderate to excellent yields from the reaction between aryl hydroxylamines and alkynes catalyzed by 10 mol % iron(II) phthalocyanine [Fe(Pc)]. Terminal and internal alkynes afford 3-aryl substituted indoles exclusively. Electron-donating and -withdrawing groups are tolerated on the aryl hydroxylamine. A few bioactive indoles are synthesized as well as several new indoles using this one-step intermolecular annulation procedure.     

Regioselective synthesis of indoles via reductive annulation of nitrosoaromatics with alkynes

[reaction: see text] Indoles are produced regioselectively and in moderate yields by two new processes: (a) from the [CpRu(CO)2]2-catalyzed reaction of nitrosoaromatics (ArNO) with alkynes under carbon monoxide and (b) in a two-step sequence involving the (uncatalyzed) reaction of ArNO with alkynes, followed by reduction of the intermediate adduct.     

Facile synthesis of isoquinolines by imination and subsequent palladacycle-catalyzed iminoannulation of internal alkynes

An efficient and facile synthesis of isoquinolines has been described via a tandem reaction of imination of o-halobenzaldehydes with tert-butyl amine and subsequent palladacycle-catalyzed iminoannulation of internal alkynes. This tandem reaction could be carried out successively in one pot without any special operation, and the annulation step could afford isoquinolines derivatives in moderate to good yields with high regioselectivity. In addition, the simple synthesis of indoles was realized by palladacycle-catalyzed annulation of o-iodoaniline or o-bromoanilines with internal alkynes.     

Efficient synthesis of aryl-substituted carbazoles via tandem double or triple suzuki coupling and cadogan cyclization

An efficient one-step method to prepare aryl-substituted carbazoles via tandem double or triple CC bond formations by multiple Suzuki couplings and CN bond formation by Cadogan cyclization has been developed. The developed method employs commercially available or easily preparable polybromonitrobenzenes and arylboronic acids as starting materials, tolerates various functional groups, and provides good yields.     

A novel and direct synthesis of indoles via catalytic reductive annulation of nitroaromatics with alkynes

Indoles are produced regioselectively and in moderate yields from the reactions of nitroaromatics with alkynes catalyzed by [CpM(CO)2]2 (1; [(eta 5-C5H5)Fe(CO)2]2; [(eta 5-C5Me5)-Fe(CO)2]2; [(eta 5-C5Me5)Ru(CO)2]2) under carbon monoxide.     

有机催化不对称Michael/环化串联反应的研究进展北大核心CSCD

串联反应能够减少反应步骤、简化操作、降低成本、实现高效率转化,符合原子经济性和绿色化学理念.特别是有机催化的不对称串联环化反应以一锅法连续催化多个化学反应,为高效合成多手性中心环状结构提供了新方法.不对称Michael/环化串联反应是构建光学活性状化合物的常用方法之一,近些年,各种有机小分子催化剂应用于不对称Michael/环化串联反应的报道不断增加,并且取得了重大进展.我们根据不同的催化剂类型综述了近5年来关于不对称Michael/环化串联反应的研究进展,并对有机催化不对称Michael/环化串联反应的发展趋势进行了展望.     

Copper-catalyzed annulation of 2-bromobenzoic esters with terminal alkynes towards 3-substituted isocoumarins

An efficient method for the synthesis of 3-substituted isocoumarins that are an important class of biologically active scaffolds via annulation of 2-bromobenzoic esters with terminal alkynes by copper catalyzed is described. The advantages of this method include mild reaction conditions, high yield and regioselectivity, and wide tolerance toward functional groups.     

Intra- and intermolecular reactions of indoles with alkynes catalyzed by gold

Indoles react intramolecularly with alkynes in the presence of gold catalysts to give from six- to eight-membered-ring annulated compounds. The cationic Au(I) complex [Au(P{C(6)H(4)(o-Ph)}(tBu)(2))(NCMe)]SbF(6) is the best catalyst for the formation of six- and seven-membered rings by 6-endo-dig, 6-exo-dig, and 7-exo-dig cyclizations. Indoloazocines are selectively obtained with AuCl(3) as catalyst in a rare 8-endo-dig process. In this process allenes or tetracyclic annulated derivatives are also formed as a result of an initial fragmentation reaction. The intermolecular reaction of indoles with alkynes proceeds to form 3-alkenylated intermediates that react with a second equivalent of indole to give bisindolyl derivatives. Indoles that are substituted at the 3-position react intermolecularly with alkynes to give 2-alkenylated intermediates that can be trapped intramolecularly with the appropriate nucleophiles.     

A concise synthesis of nornitidine via nickel- or palladium-catalyzed annulation

A concise method to synthesize benzo[c]phenanthridine alkaloid, nornitidine, was developed utilizing nickel- or palladium-catalyzed iminoannulation of an internal alkyne. The advantages of this strategy included readily available starting materials, inexpensive reagents, short reaction steps, and good yields.     

Iron-catalyzed cascade reaction of ynone with o-aminoaryl compounds: a Michael addition-cyclization approach to 3-carbonyl quinolines

An efficient iron-catalyzed cascade Michael addition-cyclization of o-aminoaryl compounds including o-aminoaryl aldehydes, o-aminoaryl ketones, and o-aminobenzyl alcohols with ynones for the synthesis of 3-carbonyl quinolines is reported. The reactions proceed to afford 3-carbonyl quinoline derivatives with or without substituent at the C-4 position in good to high yields using Iron(III) chloride hexahydrate as the catalyst in the air.     

Highly substituted furans from 2-propynyl-1,3-dicarbonyls and organic halides or triflates via the oxypalladation-reductive elimination domino reaction

The palladium-catalysed reaction of 2-propynyl-1,3-dicarbonyls with organic halides or triflates provides an efficient straightforward entry into highly substituted furans. The best results have been obtained by using an excess of the alkyne. The process can tolerate a wide variety of important functional groups both on the alkyne and the organic halide or triflate. Under an atmosphere of carbon monoxide, the reaction affords furan derivatives incorporating carbon monoxide. Depending on the alkyne to organic halide or triflate ratio, acyl furans (incorporating one molecule of carbon monoxide) or enol esters (incorporating two molecules of carbon monoxide) can be isolated as the main products.     

Visible-light-induced direct oxysulfonylation of alkynes with sulfonyl chlorides and HCl

A mild, practical and efficient strategy to prepare β-keto sulfones has been developed by visible-light-induced reactions. This reaction involved Ir(dtbbpy)(ppy)₂PF₆-catalyzed direct functionalization of alkynes with sulfonyl chloride and HCl using air as the oxidant. HCl not only acted as a hydrogen source in the proton transfer process, but also played a vital role in the reaction process.     

Synthesis of di-, tri-, and tetra-substituted carbazole analogs involving annulation methodology

Synthesis of substituted carbazole analogs was achieved via Michael addition followed by intramolecular cyclization and subsequent aromatization.