Piperidine–iodine a dual system catalyst for synthesis of coumarin bearing pyrrolo[1,2-a]quinoxaline derivatives via a one-pot three-component reaction

The synthesis of 3-(4-alkyl-4,5-dihydropyrrolo[1,2-a]quinoxalin-4-yl)-2H-chromen-2-one derivatives by a three-component reaction of salicylaldehyde, β-keto esters, and 1-(2-aminophenyl)pyrrole using piperidine–iodine as a dual system catalyst is reported. Good yields, mild reaction conditions, and ease of handling are the main aspects of the method. The structural assignments are supported by ¹H NMR, ¹³C NMR, and X-ray crystallography data.     

A facile and efficient synthesis of fully substituted pyridin-2(1H)-ones from α-oxoketene-S,S-acetals

A facile and efficient synthesis of fully substituted pyridin-2(1H)-ones has been developed by the reaction of readily available α-oxoketene-S,S-acetals with malononitrile in the presence of sodium methoxide in methanol under reflux.     

[bmim]OH-promoted one-pot,three-component synthesis of β-nitro sulfides in water

A task-specific ionic liquid, [bmim]OH, has been found to be a highly efficient catalyst for one-pot, three-component coupling of aryl aldehydes, nitromethane, and thiols for the synthesis of β-nitro sulfides in water. The main advantages of the present protocol include the use of inexpensive simple substrates and an ionic liquid as a basic catalyst.     

Multicomponent reactions of pyridines, α-bromo carbonyl compounds and silylaryl triflates as aryne precursors: a facile one-pot synthesis of pyrido[2,1-a]isoindoles

Multicomponent reactions (MCRs) involving pyridines, α-bromo ketones, and silylaryl triflates as aryne precursors were investigated. The reactions could also be extended to isoquinoline or α-bromo ethyl acetate. Substituted pyrido[2,1-a]isoindoles or isoindolo[2,1-a]isoquinolines could be obtained from this routine, which may have potential applications in antitumor drugs and fluorescent material fields.     

DBU as a scaffold for the synthesis of [1,3]oxazolo[2’,3’ : 2,3]pyrimido-[1,2-a]azepines: annulation with aromatic cyanopropargylic alcohols

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Oxone®-mediated direct arylselenylation of imidazo[2,1-b]thiazoles,imidazo[1,2-a]pyridines and 1H-pyrazoles

Oxone mediated reaction of imidazo[2,1-b]thiazole, imidazo[1,2-a]pyridine and 1H-pyrazole derivatives with diaryl diselenides is presented here. The methodology represents an efficient and simple protocol for carrying out the selective synthesis of 5-arylselanyl-imidazo[2,1-b]thiazoles, 3-arylselanyl-imidazo[1,2-a]pyridines and 4-arylselanyl-1H-pyrazoles in high yields using a stable, nontoxic and cheap oxidant. The reactions were conducted at 60?°C in air using acetonitrile as solvent. Alternatively, the use of ultrasound irradiation is presented as a tool for fast and efficient energy transfer that significantly reduced the reaction time.     

Synthesis of novel spiro[benzo[4,5]thiazolo[3,2-a]chromeno[2,3-d]pyrimidine-14,3′-indoline]-1,2′,13(2H)-triones via three component reaction

A new and efficient method for the synthesis of hitherto unreported spiro[benzo[4,5]thiazolo[3,2-a]chromeno[2,3-d]pyrimidine-14,3′-indoline]-1,2′,13(2H)-triones was developed via the Domino Knoevenagel condensation–Michael addition–intermolecular cyclization sequences of isatin derivatives, cyclohexane-1,3-diones, and 2-hydroxy-4H-benzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones, employing 12-tungstophosphoric acid (H₃PW₁₂O₄₀) as an effective and inexpensive catalyst.     

Methyl 1-imidazolecarbodithioate as a thiocarbonyl transfer reagent: a facile one-pot, three-component synthesis of novel 2-substituted-5-aryl-1-oxo-3-thioxo-1,2,3,5,11,11a-hexahydro-6H-imidazo-[1,5-b]-β-carbolines

An efficient one-pot, three-component synthesis of novel 2-substituted-5-aryl-1-oxo-3-thioxo-1,2,3,5,11,11a-hexahydro-6H-imidazo-[1,5-b]-β-carbolines employing 1-aryl-1,2,3,4-tetrahydro-β-carboline-3-carboxylates, primary amines (or amino acid esters) and methyl 1-imidazolecarbodithioate as the thiocarbonyl transfer reagent is reported.     

Tandem Parham cyclisation--α-amidoalkylation reaction in the synthesis of the isoindolo[1,2-a]isoquinoline skeleton of nuevamine-type alkaloids

C-12b substituted isoindolo[1,2-a]isoquinolones 4 are prepared efficiently via a tandem Parham cyclisation--α-amidoalkylation reaction. Thus, Parham cyclisation on imide 1 generates a 12b-hydroxy isoindolo[1,2-a]isoquinolone, which is an immediate precursor of an N-acyliminium ion. Intermolecular alkylation with different π-nucleophiles (allyl silanes or enol ethers) is accomplished upon treatment with Lewis acids (BF₃·OEt₂, TiCl₄) to obtain nuevamine-type derivatives in high yields (69-95%) under mild conditions.     

2-Allyl-N-benzyl substituted α-naphthylamines as building blocks in heterocyclic synthesis. New and efficient syntheses of benz[e]naphtho[1,2-b]azepine and naphtho[1,2-b]azepine derivatives

A new series of 13-acetyl-7,12-dihydro-7-ethylbenz[e]naphtho[1,2-b]azepine (4a-d) and 2-aryl-4-hydroxy-2,3,4,5-tetrahydronaphtho[1,2-b]azepine derivatives (6a-d) have been synthesized from N-allyl-N-benzyl substituted α-naphthylamines (1a-d) by utilizing aromatic amino-Claisen rearrangement, intramolecular Friedel-Crafts alkylation and intramolecular dipolar 1,3-cycloaddition nitrone-olefin reactions.     

l-Proline catalyzed efficient one-pot three-component aza-Diels–Alder reactions on nitrostyrylisoxazoles: a facile synthesis of new isoxazolyl tetrahydroquinolines and isoxazolo[2,3-a]pyrimidines

l-Proline acts as an efficient organocatalyst and found to promote one-pot three-component aza-Diels–Alder reaction of aryl or isoxazole imines formed in situ from aromatic or isoxazoleamines and aromatic aldehydes with nitrostyrylisoxazoles to afford the isoxazolyl tetrahydroquinolines or isoxazolo[2,3-a]pyrimidines, respectively, in excellent yields at ambient temperature under neutral conditions.     

A convenient synthesis of tetrazolo[1,5-a]-α-cycloalkanones

A convenient synthesis of a series of tetrazolo[1,5-a]-α-cycloalkanones 4a-d with the carbonyl group attached at the tetrazole carbon is described. The sequence entails the formation of an exocyclic olefin at the α-methylene position and subsequent ozonolysis. The reactions proceed under mild conditions, and the tetrazole moiety is well tolerated.     

Microwave-assisted synthesis of pyrazolo[3,4-b]pyridine-spirocycloalkanediones by three-component reaction of 5-aminopyrazole derivatives, paraformaldehyde and cyclic β-diketones

New pyrazolo[3,4-b]pyridine-5-spirocycloalkanedione derivatives were prepared via three-component reaction between 5-(4-R-benzylamino)pyrazoles, cyclic β-diketones and paraformaldehyde. The use of indandione as β-diketone resulted in the formation of two products, the pyrazolo[3,4-b]pyridine-5-spiroindanediones and 3-tert-butyl-1-phenylindeno[2,3-e]pyrazolo[3,4-b]pyridine. The structures of the pyrazolo[3,4-b]pyridine-5-spirocycloalkanedione were confirmed by single-crystal X-ray diffraction. This protocol provides a simple one-step synthetic methodology with the advantages of easy work-up, mild reaction conditions and environmentally benign.     

Synthesis of dihydrochromeno[4,3-b]pyrazolo[4,3-e]pyridin-6(7H)-ones involving one-pot three-component tandem Knoevenagel–Michael reaction catalyzed by n-tetrabutylammonium tribromide (TBATB)

The synthesis of dihydrochromeno[4,3-b]pyrazolo[4,3-e]pyridin-6(7H)-ones was achieved through one-pot three-component reaction from 4-hydroxycoumarin, aldehydes, and 3-amino-5-methyl-pyrazole in acetonitrile using 5 mol % TBATB as the catalyst under reflux condition. The product formation is through tandem Knoevenagel–Michael reaction followed by concomitant cyclization. Simple reaction procedure, shorter reaction time, good yields, avoidance of aqueous work-up, and column chromatographic separation are some of the salient features of the present protocol.     

Novel synthesis of 3-pyrrole substituted β-lactams via microwave-induced bismuth nitrate-catalyzed reaction

Highly stereoselective synthesis of 3-pyrrole substituted β-lactams is accomplished. The first step involves the synthesis of 3-phthalimido substituted β-lactams following Staudinger cycloaddition reaction of acid chloride equivalent with imines. Synthesis of 3-amino β-lactams is achieved via the deprotection of phthalimido group with ethylenediamine. These 3-amino β-lactams are converted to a new series of N-substituted pyrroles at room temperature as well as using microwave-induced bismuth nitrate-catalyzed reaction with an excellent yield. Exclusive formation of trans pyrrole-substituted β-lactams is observed with N-chrysenyl system. The method is equally efficient for the synthesis of racemic as well as optically pure 3-pyrrole substituted β-lactams.     

Diastereoselective synthesis of dispirooxindoline fused [1,3]oxazines via Diels–Alder reaction of functionalized 1,2-dihydropyridines with (E)-1,3-dihydro-3-phenacylidene-2H-indol-2-ones

An efficient synthetic procedure for the complex dispirooxindoline fused [1,3]oxazines was successfully developed via Diels–Alder reaction of (E)-1,3-dihydro-3-phenacylidene-2H-indol-2-ones with 1,2-dihydro-2-oxospiro[3H-indole-3,2′-[2H,9aH-pyrido[2,1-b][1,3]oxazines], which were obtained from three-component reactions of pyridine and isatins with acetylenedicarboxylate or propiolate. ¹H NMR data and single crystal structures indicated that this reaction has both high regioselectivity and diastereoselectivity.     

An efficient synthesis of pyrazolo[3,4-b]pyridine-4-spiroindolinones by a three-component reaction of 5-aminopyrazoles, isatin, and cyclic β-diketones

Novel pyrazolopyridine-spiroindolinones were prepared by the three-component reaction of 5-aminopyrazoles, isatin, and cyclic β-diketones in aqueous media and catalyzed by p-TSA. This protocol provides a simple one-step procedure with the advantages of easy work-up, mild reaction conditions and environmentally benign.     

Iodine/CuI-mediated alkyne–carbonyl metathesis reaction: synthesis of 1-aryl-1,2-dihydrochromeno[2,3-b]azepine-3,6-dione

Iodine/cuprous iodide-mediated intramolecular alkyne–carbonyl metathesis reaction has been developed using 2-(N-aryl-N-propargyl)aminochromone-3-carbaldehyde as the substrate. It led to the synthesis of hitherto unreported chromeno[2,3-b]azepine-3,6-dione. The special features of this methodology are mild reaction conditions, 100% atom economy and use of inexpensive reagents. This is the first example of I₂/CuI-mediated alkyne–carbonyl metathesis reaction.     

An efficient synthesis of fully substituted pyrazolo[3,4-b]pyridin-5-amines from α-azidochalcones

A facile, mild and efficient procedure for the synthesis of fully substituted pyrazolo[3,4-b]pyridin-5-amines is reported. A mixture of an α-azidochalcone, a 5-aminopyrazole and t-BuOK was stirred in DMF at ambient temperature for 5?min to afford the corresponding pyrazolo[3,4-b]pyridin-5-amines in good to excellent yields.     

One-pot,three-component synthesis of spiro[indeno[1,2-b]quinoline-10,3′-pyrroles] via the Hantzsch-type reaction of 1H-pyrrole-2,3-diones

A new methodology for the synthesis of spiro[indeno[1,2-b]quinoline-10,3′-pyrrole] derivatives via a Hantzsch-type reaction has been developed. This process involves the one-pot, three-component reaction of a 1H-pyrrole-2,3-dione, an aminocyclohexenone and 1,3-indanedione in acetic acid at reflux. Operationally simple, metal-free reaction conditions, simplicity of product isolation and good yields are key advantages of this methodology.