A convenient one-pot three component synthesis of 3-aminoalkylated indoles catalyzed by 3-chlorophenylboronic acid

An efficient protocol was developed for the synthesis of 3-aminoalkylated indoles using 3-chlorophenylboronic acid as a catalyst under ambient temperature conditions. The three-component reaction of indoles, aromatic aldehydes and N-methyl aniline offered corresponding 3-aminoalkylated indoles in excellent yields. This protocol presents some remarkable features such as mild reaction conditions, simple workup procedure and excellent yields.     

Indium trichloride catalyzed efficient one-pot synthesis of highly substituted furans

A one-pot synthesis of the substituted furans 3 could be achieved in good yields by reacting but-2-ene-1,4-diones 1 with acetoacetates 2 in the presence of a catalytic amount of InCl₃ (20 mol %) using i-PrOH as solvent at 80-90 °C for 4-8 h. InCl₃ was observed to give the optimum results among the various Lewis acids examined.     

Catalyst-free,ethylene glycol promoted one-pot three component synthesis of 3-amino alkylated indoles via Mannich-type reaction

A highly efficient and sustainable approach for the multi-component synthesis of biologically important 3-amino alkylated indoles has been investigated via Mannich-type reaction under catalyst-free, ethylene glycol as a recyclable promoting medium. The wide applicability of the present method was examined with various substrates viz substituted aldehydes, indoles and secondary amines. This method will be useful for a large scale synthesis of 3-amino alkylated indoles without the use of column chromatography. The present method provides higher environmental compatibility and sustainability factors such as smaller E-factor (0.433) and higher atom-economy (AE = 93.3%).     

Saccharomyces cerevisiae catalyzed one-pot three component synthesis of 2,3-diaryl-4-thiazolidinones

Saccharomyces cerevisiae (baker’s yeast) catalyzed one-pot three component cyclocondensation of aryl aldehydes, amines, and thioglycolic acid in organic medium leading to 2,3-diaryl 4-thiazolidinones has been carried out for the first time.     

Indium(III) bromide catalyzed one-pot synthesis of trichloromethylated tetrahydropyrimidinones

One-pot condensation of ethyl trichloroacetoacetate 1 with p-substituted aromatic aldehydes (Ph, 4-Me-C₆H₄, 4-Cl-C₆H₄, 4-MeO-C₆H₄) or furfural, and urea or thiourea catalyzed by indium(III) bromide affords eight trichloromethylated tetrahydropyrimidinones, in high yields.     

Microwave-assisted three component one-pot synthesis of pyrimido-oxazepines

A synthetic approach toward pyrimido-oxazepine analogs was developed through the use of microwave heating. Certain analogs can be made in one step, which make this a valuable tool in the investigation of this therapeutically relevant scaffold.     

Fused lactones as a route to functionalized 1-substituted indoles

Indole lactones 8 and 14 were synthesized as a means of functionalizing the 1-isopropyl substituent of the indole nucleus. Lactone 8 , upon reduction with diisobutylaluminum hydride, produces lactol 9 which behaves like a masked hydroxy aldehyde and undergoes a Horner-Emmons reaction with triethyl phosphonoacteate to give α,β-unsaturated ester 3 which possesses a hydroxyl group on the 1-isopropyl moiety.     

Indium triflate catalyzed one-pot multicomponent synthesis of spiro-hexahydropyrimidines explained by multiple covalent bond formation

A mild, efficient, and expeditious method has been developed for the synthesis of spiro-hexahydropyrimidine derivatives via a three-component, one-pot cyclocondensation reaction of aromatic amines, formaldehyde, and cyclic ketones in 4-6 h using In(OTf)₃ as Lewis acid catalyst for the first time. The reaction involving creation of six new covalent bonds was efficiently promoted by 10 mol % In(OTf)₃ and the catalyst could be recovered easily after the reaction and reused without any loss of its catalytic activity. The advantageous features of this methodology are high atom-economy, operational simplicity, shorter reaction time, and easy handling.     

A one-pot double C-H activation palladium catalyzed route to a unique class of highly functionalized thienoisoquinolines

The synthesis of a unique class of highly functionalized 3,4-thienoisoquinolines via an efficient palladium-catalyzed one-pot, regioselective double C-H activation is presented. This class of biologically relevant compounds has been prepared in five steps from commercially available starting materials with overall yields ranging from 27 to 62%. A masked carboxylic acid was used to direct C-H activation to the typically less reactive C4 position. Additionally, the carboxylic acid provides a synthetically useful handle for further functionalization.     

Synthesis of activated 3-substituted indoles: an optimised one-pot procedure

3-Substituted-4,6-dimethoxyindoles can be synthesised in a one-pot procedure from 3,5-dimethoxyaniline and 2-haloketones in the presence of lithium bromide and sodium bicarbonate.     

Solar radiation-assisted one-pot synthesis of 3-alkylated indoles under catalyst-free conditions

Solar radiation-assisted green approach was developed for the chemoselective synthesis of 3-alkylated indoles via Yonemitsu-type condensation under catalyst-free conditions. The desired products were formed by one-pot three-component reaction of indole, aromatic aldehydes, and β-dicarbonyl compounds in polyethylene glycol-400 (PEG-400). The scope and generality of the presented approach were extended by various aromatic aldehydes and CH activated compounds. Using non-volatile solvent and renewable energy resources, absence of any catalyst, energy conservation, and the selective production of heterodimer product instead of homodimer adducts such as bisindole or xanthine, increase the economic and environmental effectiveness of the present protocol.     

Indium trichloride catalyzed one-pot synthesis of indolo[2,1-a]pyrrolo[4′,3′:2,3]-7a,8,13,13b-tetrahydroquinolines through intramolecular imino Diels-Alder reactions

An efficient synthesis of tetrahydroquinolines has been achieved by the reaction of aldimines derived from various substituted aromatic amines and indole-2-carbaldehyde containing an internal dienophile using 20 mol % InCl₃ in acetonitrile at room temperature. The reactions are very fast and the products are isolated in good yields and in pure form.     

FeCl3 as Lewis acid catalyzed one-pot three-component aza-Friedel-Crafts reactions of indoles, aldehydes, and tertiary aromatic amines

A new strategy for the synthesis of 3-diarylmethyl indoles was developed through FeCl₃ as Lewis acid catalyzed three-component aza-Friedel-Crafts reactions of indoles, aldehydes, and tertiary aromatic amines in one-pot. The reactions generated the corresponding 3-diarylmethyl indoles in good yields under mild reaction conditions by using less expensive, readily available, and environmentally benign iron catalyst. It is important to note that the key feature of this reaction is operational simplicity.     

New versatile route to the synthesis of tetrahydro-beta-carbolines and tetrahydro-pyrano[3,4-b]indoles via an intramolecular Michael addition catalyzed by InBr3

A simple multistep synthetic strategy to 4-substituted 1,2,3,4-tetrahydro-beta-carboline and 1,3,4,9-tetrahydro-pyrano[3,4-b]indole derivatives starting from commercially available indole 2-carboxylic acid (5) is described. The final intramolecular Michael addition promoted by catalytic amount of InBr(3) (5-10 mol %) provided the expected polycyclic compounds in excellent yields (up to 97%) both in anhydrous organic and aqueous media.     

A highly efficient route to C-3 alkyl-substituted indoles via a metal-free transfer hydrogenation

A highly efficient route to C-3 alkyl-substituted indoles via completely metal-free catalytic transfer hydrogenation of 3-indolemethanols was developed. This process proceeds via vinylogous iminium intermediates formed in situ in the presence of Brønsted acids, and Hantzsch ester is used as the reductant. The reduction works extremely well with a large substrate scope, and the yields exceed 90% in almost all cases.     

Indoles from 3-nitropyridinium salts: A new route to chiral indoles and indolines

(S)-1-(1-Methylbenzyl)-2,4,6-trimethylindole was prepared by interaction of (S)-isopropyliden(1-methylbenzyl)amine with 1,2,4,6-tetramethyl-3-nitropyridinium iodide. The indoles thus prepared undergo diastereoselective hydride reduction and debenzylation to afford chiral (S)-2,4,6-trimethylindoline with high yield and optical purity up to 76%.     

The rearrangement route to 3-carboxy- and 3-hydroxymethyl-2-azabicyclo[2.1.1]hexanes: 3,5-methanoprolines

Improved stereocontrolled syntheses of 5-anti-hydroxy-3-exo-methoxycarbonyl-2-azabicyclo[2.1.1]hexanes have been effected from pyridine. The key step in the electrophilic addition-rearrangement of 2-azabicyclo[2.2.0]hex-5-ene precursors incorporates either a 3-endo-phenyl group, as an acid precursor, or a 3-endo-phenyldimethylsilylmethyl group, as a potential hydroxymethyl and acid precursor.     

Three component one-pot synthesis of novel pyrimidino thiazolidin-4-ones catalyzed by activated fly ash

Abstract

2-Phenyl-3-(4,6-diarylpyrimidin-2-yl) thiazolidin-4-ones, 12–22, were synthesized with good yields in a short reaction time by the “one-pot” multicomponent reaction of the appropriate 2-amino-4,6-diarylpyrimidines, benzaldehyde, and thioglycolic acid under microwave irradiation in the presence of activated fly ash catalyst. The characterization of these compounds was confirmed by melting point, elemental analysis, MS, FT-IR, and one-dimensional NMR (¹H and ¹³C) spectroscopic data.     

An amide orthoesterification route to N-(1′-alkylthioglucopyranosyl)indoles

The addition of 3-methylindolylmagnesium bromide to tetra-O-benzyl-α-d-gluconothionolactone yields the expected indole N-gluconothioamide as its hemiorthothioamide tautomer. The thiol function is alkylated to yield the corresponding orthothioamide, a 1′-alkylthio-substituted N-glycoside. Alternatively, the 1′-alkylthio-N-glycoside can be accessed from the corresponding indole N-gluconamide via a boron trifluoride-etherate mediated orthoesterification with ethanethiol. Radical reduction of the orthothioamide yields the N-glycosides in 2:1 stereoselectivity in favor of the β-N-glycoside, while reduction via the oxonium ion leads to an improved 6:1 selectivity.