The first ionic liquid-promoted Kabbe condensation reaction for an expeditious synthesis of privileged bis-spirochromanone scaffolds

A variety of privileged bis-spirochromanones were synthesized for the first time from 4,6-diacetyl resorcinol in one-pot by carrying out the Kabbe condensation in room temperature ionic liquid [bbim]Br.     

A novel synthesis of precocenes. Efficient synthesis and regioselective O-alkylation of dihydroxy-2,2-dimethyl-4-chromanones

The reactions of trihydroxybenzenes 1a-c and 3-methylbut-2-enoic acid ( 2 ) in a zinc chloride/water/phosphoryl chloride system afford either the new trihydroxyphenylbutenone derivatives 3b,c or dihydroxy-2,2-dimethyl-4-chromanones 4a-c in good yields. Compounds 3b,c can be cyclized in high yields to 4b,c in 5% sodium hydroxide solution. Regioselective O-alkylation of 4a-c leads to 5a-f in good yields. O-Alkylation of 5a-f , followed by reduction and dehydration, results in the formation of precocene 3 ( 7d ) and its regioisomer 7a-c,e,f . Methylation of 4a-c gives 6g-i . Subsequent reduction and dehydration affords precocene 2 ( 7h ) and its regioisomers 7g,i .     

An efficient synthesis of 4-chromanones

A two step efficient and practical synthesis of a variety of 4-chromanones is described. Phenols undergo a Michael addition to acrylonitriles in the presence of catalytic amounts of potassium carbonate and tert-butanol to generate the corresponding 3-aryloxypropanenitriles in 50-93% yields. Treatment of the resulting aryloxypropionitriles with 1.5 equiv of TfOH and 5 equiv of TFA, followed by an aqueous work up afforded 4-chromanones in moderate to excellent yields.     

A facile and expeditious microwave-assisted synthesis of 4-aryl-2-ferrocenyl-quinoline derivatives via multi-component reaction

An efficient and rapid route for the synthesis of 4-aryl-2-ferrocenyl-quinoline derivatives through microwave-assisted multi-component reaction of acetylferrocene with aromatic aldehyde and dimedone in the presence of ammonium acetate using DMF as reaction media at 100 °C is described. This novel procedure lends itself well to combinatorial methods, providing the target heteropolymetallic compounds in excellent yield without further purification.     

An efficient and expeditious microwave-assisted synthesis of 4-azafluorenones via a multi-component reaction

An efficient and expeditious microwave-assisted synthesis of 4-azafluorenone derivatives and related compounds is accomplished via a multi-component reaction of an aldehyde, 1,3-indanedione, an arone and ammonium acetate. It is an efficient and promising synthetic strategy to build indenopyridine skeleton.     

Direct preparation of 3,4-dichloro-2,-dimethyl-3-chromenes from 2,2-dimethyl-4-chromanones

Reaction of 2,2-dimethyl-4-chromanones($\text{1}$) with two equivalents of phosphorus pentachloride affords, 3,4-dichloro-2,2-dimethyl-3-chromenes($\text{2}$) in variable yields depending on the substituents of the aromatic ring. A plausible pathway for this reaction is given.     

Synthesis of 2,2-dialkyl(phenyl)-4-(2-hydroxyethyl)thiadiazinones

2,2-Dialkyl(phenyl)-4-(2-hydroxyethyl)thiadiazin-5-ones are formed as a result of the reaction of thioglycolic acid with 2-hydroxyethylhydrazones. The structures of the reaction products were proved by PMR and ¹³C NMR spectrometry and the mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 838–839, June, 1991.     

A facile and expeditious approach for the synthesis of 2-azetidinone derivatives via a multicomponent reaction

Abstract  

New organic reactions allow chemical transformations which were previously unknown. Therefore, new reactions are important contributions to progress in the field of organic synthesis. Herein, we are reporting a simple, one-pot, efficient three-component synthesis of novel 3-chloro-4-[4-(2-oxo-2H-chromen-4-ylmethoxy)phenyl]-1-phenylazetidin-2-one derivatives using 4-(2-oxo-2H-chromen-4-ylmethoxy)benzaldehydes, anilines, and chloroacetyl chloride in the presence of triethyl amine as a catalyst under different conditions. Taking into account environmental and economic considerations, the protocol presented here has the merits of simple operation, convenient work-up, being environmentally benign, and providing good yields. The synthesized compounds were characterized by IR, ¹H NMR, ¹³C NMR, MS, and elemental analysis.     

A new synthesis of homoisoflavanones (3-benzyl-4-chromanones)

Two 7-hydroxyhomoisoflavanones ( / ) have been synthesized from corresponding 2'-hydroxydihydrochalcones ( / ) in about 33% overall yields. The stages are : (1) selective protection of C₄'-hydroxyl in ( / ) with EtO.CH₂Cl (1 molar equiv.) In the presence of dry K₂C0₃ and acetone at r.t.; (ii) reaction with one more molar equiv. of EtO.CH₂Cl at 60–70° without Isolating products ( / ) (iii) cyclizatlon of resulting α-hydroxymethyl derivatives ( / ) with 4% aq. aIc. Na₂C0₃ and (iv) deprotection of resulting 7-ethoxymethoxy homoisoflavanones ( / ) with 10% CH₃0H-HC1. The explanations for the formation of ( / ) and ( / ) are given.     

Corrole synthesis by dipyrromethane-dicarbinol and 2,2′-bipyrrole condensation

A₃ and trans-A₂B tris-aryl corroles 1a-c have been synthesized in up to 12% yield by BF₃·Et₂O-catalyzed condensation of dipyrromethane-dicarbinol and 2,2′-bipyrrole (1:1 ratio) in acetonitrile at room temperature for 24 h.     

Zirconium-catalyzed Nagata reaction for the synthesis of 2-aryl-1,3,2-aryldioxaborins via a mild three-component condensation of phenols, aldehydes, and boronic acid

An efficient ZrCl₄-catalyzed ortho-hydroxyalkylation of phenols with aldehydes promoted by 3,5-bis(trifluoromethyl)phenyl boronic acid, leading to the formation of 2-aryl-1,3,2-aryldioxaborins, was investigated and optimized. The reaction afforded the desired aryldioxaborins in good to excellent yields under mild conditions at room temperature. The electron-deficient boronic acid promoter was essential. Electron-rich phenols react faster, and both alkyl and aryl aldehydes are suitable substrates. The resulting aryldioxaborins can be further elaborated to produce substituted saligenols, 2-ethoxy chromans, and 2-substituted phenols.     

Organocatalyzed enantioselective synthesis of 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carboxylates

The organocatalyzed enantioselective synthesis of biologically active 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carboxylate derivatives was achieved using bifunctional cinchona alkaloids as the catalysts. Using quinine thiourea as the catalyst, the tandem Michael addition-cyclization reaction between 1,3-cyclohexanediones and alkylidenecyanoacetate derivatives gives the desired products in high yields (up to 92%) and good ee values (up to 82%).     

An expeditious synthesis of 4-fluoropiperidines via aza-Prins cyclization

The reaction of aldehydes with N-tosyl homoallylamine in the presence of a solution of tetrafluoroboric acid-diethyl ether complex in dichloromethane at ambient temperature gave the 4-fluoropiperidines in good yields and with high cis-selectivity. This aza-Prins-type cyclization has a wide scope and the use of HBF₄·OEt₂ makes this procedure simple, convenient, and cost-effective for the preparation of 4-fluoropiperidines.     

Organocatalyzed synthesis of 2-amino-8-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitriles

2-Amino-8-oxo-tetrahydro-4H-chromene-3-carbonitriles were synthesized for the first time from a tandem Michael addition-cyclization reaction between cyclohexane-1,2-dione and benzylidenemalononitriles. An enantioselective synthesis of these compounds was achieved in moderate ee values (up to 63% ee) by using a cinchona alkaloid-derived thiourea catalyst.     

Novel and expeditious microwave-assisted three-component reactions for the synthesis of spiroimidazolin-4-ones

Highly efficient methods for the syntheses of spiroimidazolinones via microwave-assisted three-component one-pot sequential reactions or one-pot domino reactions are described. The efficiency and utility of the methods have been demonstrated by quickly accessing the antihypertensive drug irbesartan (2).     

Three-component coupling strategy for the expeditious synthesis of novel 4-aminobenzoxazinone N-nucleosides

One-pot montmorillonite K-10 clay-supported three-component reactions of substituted salicylaldehydes, ribosyl/deoxyribosylureas and ammonium acetate expeditiously yield the novel N-nucleosides, 4-amino-3,4-dihydro-3-(β-d-ribo- or β-d-2′-deoxyribofuranosyl)-2H-benz[e]-1,3-oxazin-2-ones, via cycloisomerisation of an aldimine intermediate under solvent-free microwave irradiation conditions.     

Heteropoly acid-catalyzed aza-Prins-cyclization: an expeditious synthesis of 4-hydroxypiperidines

4-Hydroxypiperidines are prepared in good yields and with high selectivity by means of aza-Prins-cyclization using 10 mol % phosphomolybdic acid under mild reaction conditions. This is the first report on the preparation of 4-hydroxypiperidines via aza-Prins-cyclization.