Synthesis of sterically congested 1,3,4-oxadiazole derivatives from aromatic carboxylic acids, acenaphthoquinone, and (N-isocyanimino)triphenylphosphorane

Abstract  

Reactions of (N-isocyanimino)triphenylphosphorane with acenaphthoquinone in the presence of aromatic carboxylic acids proceed smoothly at room temperature and under neutral conditions to afford sterically congested 1,3,4-oxadiazole derivatives in high yields. The reaction proceeds smoothly and cleanly under mild conditions and no side reactions are observed.     

A one-pot synthesis of N-alkylthiazoline-2-thiones from CS2, primary amines, and 2-chloro-1,3-dicarbonyl compounds in water

Abstract  

A simple synthesis of N-alkylthiazoline-2-thiones by reaction of primary amines, carbon disulfide, and 2-chloro-1,3-dicarbonyl compounds in water is described. Proceeding without catalyst under one-pot conditions in high yields and with broad scope, this method high synthetic utility.     

A highly selective method for the synthesis of 1,3-diarylbenzo[f]quinoline derivatives catalyzed by silver triflate

Abstract  

The three-component reactions of aromatic aldehydes, naphthalen-2-amine, and phenylacetylene catalyzed by AgOTf in toluene selectively gave 1,3-diarylbenzo[f]quinolines in high yields. This procedure provides an efficient method for the synthesis of benzo[f]quinolines under mild reaction conditions and with high yields, high selectivity, and operational simplicity.     

Zirconium(IV) chloride as versatile catalyst for the expeditious synthesis of quinoxalines and pyrido[2,3-<Emphasis Type="Italic">b</Emphasis>]pyrazines under ambient conditions

Abstract  

Among the various transition metal chlorides, zirconium(IV) chloride was found to be an efficient catalyst for the rapid synthesis of a wide range of 2,3-dialkyl- and 2,3-diaryl-quinoxaline and pyrido[2,3-b]pyrazine derivatives in excellent yields at room temperature. The remarkable features of this catalytic process are the mild reaction conditions, quantitative yields, short reaction times, high conversions, tolerability of various functional groups, clean reaction profiles, and operational simplicity.     

Sulfamic-acid-catalyzed simple and efficient synthesis of 4-aryl-3-methyl-1-phenyl-1H-benzo[g]pyrazolo[3,4-b]quinoline-5,10-diones under solvent-free conditions

Abstract  

An efficient synthesis of 4-aryl-3-methyl-1-phenyl-1H-benzo[g]pyrazolo[3,4-b]quinoline-5,10-diones from the three-component condensation reaction of 3-methyl-1-phenyl-1H-pyrazol-5-amine, aromatic aldehydes, and 2-hydroxy-1,4-naphthoquinone under solvent-free conditions in good to excellent yields and short reaction times using sulfamic acid as heterogeneous acid catalyst has been investigated.     

Nanocrystalline aluminium oxide: a mild and efficient reusable catalyst for the one-pot synthesis of poly-substituted quinolines via Friedlander hetero-annulation

Abstract  

o-Aminoaryl ketones undergo smooth condensation with α-methylene ketones in the presence of nanocrystalline aluminium oxide under mild reaction conditions to afford the corresponding poly-substituted quinolines in excellent yields. The catalyst can be recovered by simple filtration and can be recycled in subsequent reactions.     

PTSA catalyzed simple and green synthesis of benzothiazole derivatives in water

Abstract  

p-Toluenesulfonic acid (10 mol%) was found to be an effective and efficient catalyst for the synthesis of 2-substituted benzothiazoles from aromatic aldehydes and 2-aminothiophenol in moderate to excellent yields in water. This method provides a simple and efficient protocol in terms of mild reaction conditions, clean reaction profiles, small quantity of catalyst, and simple workup procedure.     

A single-step, mild, neutral, catalyst-free method for cyanohydrin synthesis

Abstract  

A wide variety of carbonyl compounds can be transformed to their corresponding cyanohydrins in a single step using a dimethyl sulfoxide (DMSO)–water system in excellent yields (75–94%). The major advantages of this system are that the reaction conditions are mild and neutral; the reaction proceeds without catalyst and gives the corresponding cyanohydrins in short time (15–120 min).     

Succinimide sulfonic acid (SuSA): an efficient and recyclable catalyst for the chemoselective <Emphasis Type="Italic">N</Emphasis>-Boc protection of amines

Abstract  

Succinimide sulfonic acid (SuSA) as a stable reagent is easily prepared by the reaction of succinimide with neat chlorosulfonic acid. This compound is able to catalyze the chemoselective conversion of amines to their corresponding N-Boc protected derivatives with (Boc)₂O. All reactions were performed under mild conditions, giving the desired products in good to high yields.     

A facile and efficient method for synthesis of xanthone derivatives catalyzed by HBF4/SiO2 under solvent-free conditions

Abstract  

HBF₄/SiO₂ was used as an efficient, green, and inexpensive catalytic system for synthesis of 12-aryl or 12-alkyl-8,9,10,12-tetrahydro-11H-benzo[a]xanthen-11-one derivatives via a one-pot three-component reaction of aldehydes, 2-naphthol, and cyclic 1,3-dicarbonyl compounds. The reactions proceeded rapidly at 80 °C under solvent-free conditions and the desired products were obtained in good to excellent yields.     

Synthesis of pyrrolo[1,2-f]phenanthridine-annulated polycyclic heterocycles from palladium-catalyzed intramolecular direct arylation reaction

Abstract  

A concise synthesis of pyrrolo[1,2-f]phenanthridine-annulated polycyclic heterocycles has been achieved in good yields by palladium-catalyzed intramolecular direct arylation reaction.     

Stereoselective reaction between alkyl propiolates and phenols in the presence of sodium azide in tert-butyl alcohol

Abstract  

Stereoselective reaction of various substituted phenols with alkyl propiolates in the presence of a catalytic amount of sodium azide in tert-butyl alcohol at reflux temperature leads to alkyl (Z)-3-phenoxy-2-propenoates in good yields.     

Expedient one-pot synthesis of N-aryliminoethers via mild electrophilic activation of secondary amides

Abstract  

The direct transformation of various secondary amides into N-aryliminoethers via mild electrophilic activation with trifluoromethanesulfonic anhydride in the presence of 2-chloropyridine is described. Low temperature amide activation followed by warming to 0 °C and subsequent treatment with phenols provides the desired products with short overall reaction times and moderate to high reaction yields.     

Synthesis of fused uracils: pyrano[2,3-d]pyrimidines and 1,4-bis(pyrano[2,3-d]pyrimidinyl)benzenes by domino Knoevenagel/Diels-Alder reactions

Abstract  

Knoevenagel condensation of barbituric acids with aromatic aldehydes containing one or two formyl groups was carried out. 5-Arylidenebarbituric acids underwent smooth hetero-Diels-Alder (HDA) reactions with enol ethers to afford cis and trans diastereoisomers of pyrano[2,3-d]pyrimidine-2,4-diones and 5,5′-(1,4-phenylene)bis[2H-pyrano[2,3-d]pyrimidine-2,4(3H)-dione] derivatives in excellent yields (75–88 %). Syntheses were realized by Knoevenagel condensation and HDA reaction in four different reaction conditions: Knoevenagel condensation in water and Diels-Alder reaction in methylene chloride solution, Knoevenagel condensation in water and Diels-Alder reaction without solvent, three-component one-pot reaction in methylene chloride solution, or three-component one-pot reaction in water. All reactions were carried out without catalyst at room temperature. The reactions of malononitrile with Knoevenagel condensation products of barbituric acids and heteroaromatic aldehydes or terephthalaldehyde were examined and did not provide corresponding pyranopyrimidines.     

Granulated copper oxide nano-catalyst: a novel and efficient catalyst for C–N cross-coupling of amines with iodobenzene

Abstract  

Nano-structured CuO granules catalyze the C–N cross-coupling of amines with iodobenzene in excellent yields. The reaction is simple, efficient, and operates in air under ligand-free conditions.     

l-Proline: an efficient catalyst for the synthesis of new spirooxindoles

Abstract  

l-Proline was found to be a versatile organocatalyst for the synthesis of new spirooxindole derivatives in good yields under mild reaction conditions using 1-propanol as a solvent.     

DBU-catalyzed expeditious and facile multicomponent synthesis of N-arylquinolines under microwave irradiation

Abstract  

N-Arylquinoline derivatives are obtained in excellent yields by a rapid, easy, and efficient one-pot multicomponent reaction of aromatic aldehydes, 3-arylamino-5,5-dimethylcyclohex-2-enone, and active methylene compounds utilizing 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a catalyst in ethanol under microwave irradiation.     

Aldimines of 5-aminouracil as reagents in 1,3-dipolar cycloaddition reaction

Abstract  

The condensation of 5-aminouracil with aromatic aldehydes gave the appropriate C-arylimines, which were used in [2+3] cycloaddition with nitrile oxides derived from 4-substituted benzaldoximes. As a result of the dipolar cycloaddition reaction several hitherto unknown 5-(3,5-diphenyl-1,2,4-oxadiazol-4(5H)-yl)pyrimidine-2,4(1H,3H)-diones have been obtained in satisfactory yields.     

Synthesis of 8-oxoprotoberberines using acid-mediated cyclization or the Heck reaction

Abstract  

A facile method of synthesizing 8-oxoprotoberberines is described from 6-benzoyl-5,6,7,8-tetrahydro-[1,3]dioxolo[4,5-g]isoquinoline-5-carbaldehyde via acid-mediated cyclization or from 2-(2-iodophenethyl)isoquinolin-1(2H)-one via the Heck reaction. The present method offers several advantages, such as good yields and a simple procedure.     

Solvent-free, one-pot synthesis of amidoalkyl naphthols by a copper p-toluenesulfonate catalyzed multicomponent reaction

Abstract  

An efficient synthesis of amidoalkyl naphthols using copper p-toluenesulfonate (CPTS) as catalyst for the three-component condensation reaction of 2-naphthol, aldehydes, and amides under thermal, solvent-free conditions is described. This new approach has advantages such as short reaction time, high yield, simple work-up, and reusable catalyst.