Synthesis of carbazoles via an intramolecular cyclization of 2-(6-substituted 3(Z)-hexen-1,5-diynyl)anilines and their related molecules

Various 2-(6-substituted 3(Z)-hexen-1,5-diynyl)anilines 1a-g were treated with potassium tert-butoxide or potassium 3-ethylpentanoxide in NMP at 60 degrees C for 2 h to give the corresponding 5-substituted carbazoles 2a-g in 36-65% yields together with indoles 9a-g in 21-40% yields, respectively. Exposing the trifluoroacetamide analogues 10h-k under the same reaction conditions gave the carbazoles 2b-e in 37-57% yields and indoles 9b-e in 15-27% yields. Subsequent cyclizations of acetamide analogues 10a-g gave carbazoles 2a-g in 53-86% yields.     

Dual Palladium/Scandium Catalysis toward Rotationally Hindered C3‐Naphthylated Indoles from β‐Alkynyl Ketones and o‐Alkynyl Anilines

A new dual palladium/scandium catalysis starting from β‐alkynyl ketones and o‐alkynyl anilines is reported for the first time, leading to the atom‐economic synthesis of rotationally hindered C3‐naphthylated indoles in moderate to good yields and high regioselectivity. This method can tolerate normal air conditions, and features the use of palladium/scandium cooperative catalysts without any ligand, facile double annulation involving various internal alkynes, and good functional group tolerance.     

A bimetallic catalyst and dual role catalyst: synthesis of N-(alkoxycarbonyl)indoles from 2-(alkynyl)phenylisocyanates

3-allyl-N-(alkoxycarbonyl)indoles are synthesized via the reaction of 2-(alkynyl)phenylisocyanates and allyl carbonates in the presence of Pd(PPh(3))(4) (1 mol %) and CuCl (4 mol %) bimetallic catalyst. It is most probable that Pd(0) acts as a catalyst for the formation of a pi-allylpalladium alkoxide intermediate and Cu(I) behaves as a Lewis acid to activate the isocyanate, and the cyclization step proceeds with a cooperative catalytic activity of Pd and Cu. On the other hand, N-(alkoxycarbonyl)indoles are produced via the reaction of 2-(alkynyl)phenylisocyanates and alcohols under a catalytic amount of Na(2)PdCl(4) (5 mol %) or PtCl(2) (5 mol %). Pd(II) or Pt(II) catalyst exhibits dual roles; it acts as a Lewis acid to accelerate the addition of alcohols to isocyanates and as a typical transition-metal catalyst to activate the alkyne for the subsequent cyclization.     

Reactions of N- and C-Alkenylanilines: II. Halocyclization of 2-(2-Cycloalkenyl)anilines

The reaction of 2-(2-cyclopentenyl)anilines with I₂ in the presence of NaHCO₃ results in formation of 3-iodocyclopenta[b]indoles in high yields. Under similar conditions 2-(2-cyclohexenyl)anilines give rise to cyclization products whose structure depends on the solvent and substituents in the aromatic ring and on the nitrogen atom.     

Synthesis of N-aryl-3-(arylimino)-3H-indol-2-amines via hypervalent iodine promoted oxidative diamination of indoles

A direct and fast oxidative diamination of substituted indoles with anilines was realized by using 1-fluoro-1,2-benziodoxol-3(1H)-one under mild conditions. This protocol could provide a wide range of synthetically valuable N-aryl-3-(arylimino)-3H-indol-2-amine derivatives under peroxide-free conditions within 30?min in up to 91% yields.     

Iron(iii) chloride-catalyzed mechanochemical cascade synthesis of highly-substituted pyrrolyl indoles

Iron(iii) chloride has been found to serve as an efficient catalyst for a mechanochemical (ball milling) one-pot four- component cascade reaction of phenyl glyoxal, anilines, indoles and activated alkyne affording highly-substituted 3-(1H-pyrrol-2-yl)-1H-indoles. The procedure is beneficial because of mild conditions, easily available starting materials, cheap catalyst and possibility for scaling.     

Direct palladium-catalyzed C-3 alkynylation of indoles

The direct palladium-catalyzed coupling reaction of indoles with alkynyl bromides was described in this paper. In the presence of catalytic amount of PdCl₂(PPh₃)₂ and 2.0 equiv. NaOAc, the coupling reaction of indoles with alkynyl bromides proceeded smoothly at 50 °C to give the corresponding 3-alkynylindoles with high regioselectivity in good to excellent yields.     

Regioselective Mercury(I)/Palladium(II)-Catalyzed Single-Step Approach for the Synthesis of Imines and 2-Substituted Indoles

An efficient synthesis of ketimines was achieved through a regioselective Hg(I)-catalyzed hydroamination of terminal acetylenes in the presence of anilines. The Pd(II)-catalyzed cyclization of these imines into the 2-substituted indoles was satisfactorily carried out by a C-H activation. In a single-step approach, a variety of 2-substituted indoles were also generated via a Hg(I)/Pd(II)-catalyzed, one-pot, two-step process, starting from anilines and terminal acetylenes. The arylacetylenes proved to be more effective than the alkyl derivatives.     

2-(取代苯亚氨次甲基)吲哚衍生物的质谱研究

报道了由吲哚-2-甲醛和取代苯胺进行亲核加成反应合成了22个2-(取代苯亚氨次甲基)吲哚衍生物,主要对本类化合物的两种质谱特殊裂解过程进行了分析研究。     

One-pot synthesis of indole-fused scaffolds via gold-catalyzed tandem annulation reactions of 1,2-bis(alkynyl)-2-en-1-ones with indoles

The gold-catalyzed tandem cyclization of 1,2-bis(alkynyl)-2-en-1-ones with indoles offers an efficient and straightforward route to indole-fused polycyclic systems. The process is realized through a cascade carbonyl-yne cyclization/Friedel-Crafts/indole-yne cyclization sequence catalyzed by a single-pot catalyst of gold.     

Sc(OTf)3-catalyzed or t-BuOK promoted tandem reaction of 2-(2-(alkynyl)benzylidene)malonate with indole

Tandem reaction of 2-(2-(alkynyl)benzylidene)malonate with indole was investigated. (Z)-1-Benzylidene-3-(1 H-indol-1-yl)-1 H-indene-2,2(3 H)-dicarboxylate was generated in the presence of t-BuOK at room temperature; whereas 3-((1 H-indol-3-yl)(2-(alkynyl)aryl)methyl)-1 H-indole was obtained when Sc(OTf)3 was utilized as catalyst at 50 degrees C.     

The preparation of 5-indolyl-Mannich bases: an expedient source of 5-(chloromethyl)indoles

Regioisomeric analogues of gramine, 5-(dialkylaminomethyl)indole-2-carboxylates were prepared by the Fischer indolization of 4-(dialkylaminomethyl)phenylhydrazones easily obtained from diazotized 4-(dialkylaminomethyl)anilines by the Japp-Klingemann reaction. These formal Mannich bases are valuable synthetic intermediates affording 5-(chloromethyl)indoles on reaction with acetyl chloride at rt within a few minutes in quantitative yields.     

Domino rhodium(I)-catalysed reactions for the efficient synthesis of substituted benzofurans and indoles

Rhodium(I) catalysts promote the transformation of o-alkynyl phenols and anilines to the corresponding benzo[b]furans and indoles. The reaction is postulated to proceed via a transient 3-rhodium heterocycle intermediate, which can be trapped with suitable electrophiles to give poly-substituted heterocycles. In the case of mono-substituted electron-withdrawn electrophiles, excellent yield and selectivity for conjugate addition versus Heck-Mizoroki reaction can be achieved. In the case of 2-alkynyl pyridine electrophiles, novel 2-(benzofuran-3-yl)vinylpyridines are formed.     

Synthesis of 3-substituted cyclopenta[b]indoles

When reacting with I₂, 2-(cyclopent-2-enyl)anilines undergo cyclization into 3-iodo-1,2,3,3a,4,8b-hexahydrocyclopenta[b]indoles in high yields. The minor reaction products were 3,5- or 3,7-diiodoindolines. Ammonolysis of 3-iodo-5-methyl-1,2,3,3a,4,8b-hexahydro-cyclopenta[b]indole or itsN-chloroacetyl derivative results in 3-amino-5-methyl-1,2,3,3a,48b-hexahydro- and 5-methyl-1,3a,4,8b-tetrahydrocyclopenta[b]indoles. Published inIzvestiya Akademii Nauk. Seriya Khimischeskaya, No. 10, pp. 1789–1793, October, 2000.     

An Ir-Pt catalyst for the multistep preparation of functionalized indoles from the reaction of amino alcohols and alkynyl alcohols

The 1,2,4-trimethyltriazolylidene (ditz) ligand allows the preparation of homo- and heterodimetallic complexes of Pt(2) and Ir-Pt. These two complexes have been characterized by means of spectroscopic and diffractommetric techniques. The catalytic activity of these complexes, together with that of other Pt-based compounds, has been explored in the cyclization-addition of alkynyl alcohols and indoles. The Ir-Pt complex [{PtI(2)(py)}(μ-ditz){IrI(2)(Cp*)}] (py=pyridine; Cp*=pentamethylcyclopentadienyl) allows the combination of an iridium-mediated oxidative cyclization of 2-(ortho-aminophenyl)ethanol to form indoles, with a further step employing a Pt-based multistep reaction that functionalizes indoles. Our results show that the Ir-Pt complex is a very active catalyst in this new multistep preparation of functionalized indoles from the reaction of an amino alcohol with alkynyl alcohols.     

l-Proline catalyzed domino Michael addition of N-substituted anilines

Here we report l-proline catalyzed 3-component reaction of indoles, aldehydes and N-substituted anilines in water as solvent at room temperature for the synthesis of 3-(α,α-diarylmethyl)indoles. The reaction is in fact a Michael addition of N-substituted anilines to alkylideneindolenines. The reaction is very clean, high yielding and having broad substrate scope. A tentative mechanism is proposed.     

New Synthesis of 1-Substituted 3-(2-Aminoethyl)indoles

A number of 1-substituted 3-(2-aminoethyl) indoles were prepared, in one step, by alkylation of the corresponding 3-(2-aminoethyl)indoles (tryptamines) in the presence of NaH.     

Regioselective alkynylation of 2-aryl-4-chloro-3-iodoquinolines and subsequent arylation or amination of the 2-aryl-3-(alkynyl)-4-chloroquinolines

Palladium-CuI catalyzed Sonogashira coupling of 2-aryl-4-chloro-3-iodoquinolines with terminal acetylenes (1 equiv) in triethylamine afforded the 2-aryl-3-(alkynyl)-4-chloroquinolines as sole products. The 2-aryl-4-chloro-3-iodoquinolines coupled with excess terminal acetylenes (2.5 equiv) in dioxane/water to yield the 2-aryl-3,4-bis(alkynyl)quinoline derivatives in a one-pot operation. The 2-aryl-3-(alkynyl)-4-chloroquinolines were, in turn, subjected to arylation via Suzuki cross-coupling with arylboronic acid derivatives or amination with methylamine, respectively. The structures of the products of successive Sonogashira and Suzuki cross-couplings were also confirmed by X-ray crystallography.     

Rapid, robust, clean, catalyst-free synthesis of 2-halo-3-carboxyindoles

A novel synthesis of 2-halo-3-carboxyindoles from 2-(2,2-dihalovinyl)anilines was discovered. Reaction conditions and substrate applicability were studied. Optimally, the reaction takes only minutes when these substrates are heated in DMSO at 120 °C in the presence of cesium carbonate. However, the reaction is robust and takes place at a wide range of temperatures, is tolerant of aqueous reaction conditions, and can be performed in a variety of polar solvent/carbonate base combinations—where the limiting factor is base solubility. A wide range of substituents is tolerated on the 2-(2,2-dihalovinyl)anilines, and yields are generally high, requiring only acidic aqueous work-up to obtain pure products. No catalyst is required for the transformation. The mechanism is believed to involve initial formation of an alkynyl bromide intermediate followed by ring closure and carbon dioxide trapping, leading to product formation.     

A convenient synthesis of 3-(4-pyridinyl)quinolines

3-(Arylamino)-2-(4-pyriclinyl)acroleins 3 prepared by reacting anilines 1 with 3-(dimethylamino)-2-(4-pyridinyl)acrolein ( 2 ) were cyclized with phosphorus oxychloride or acetic acid to give 3-(4-pyridinyl)quinolines 4 .