Synthesis of new 1,3-disubstituted-2,3-dihydro-1H-naphth[1,2e][1,3]oxazines

1,3-Disubstituted-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines were prepared through the ring-closure reactions of the aminobenzylnaphthols with substituted aryl- and heteroarylaldehydes.     

Calcium acetate catalyzed synthesis of 4-arylidene-2-phenyl-5(4H)-oxazolones under solvent-free conditions

Eight 4-arylidene-2-phenyl-5(4H)-oxazolones (azlactones) have been prepared via Erlenmeyer synthesis from aromatic aldehydes and hippuric acid using calcium acetate under solvent-free conditions with microwave irradiation.     

Dual Behavior of Ammonium Acetate for the Synthesis of Diverse Symmetrical/Unsymmetrical Bis[1,3]oxazines Possessing Anticancer Activity

A simple and efficient approach was developed to synthesize symmetrical/unsymmetrical bis[1,3]oxazines using ammonium acetate with controllable substitution patterns in a one-pot fashion. In a representative crystal structure, the [1,3]oxazine ring is in a distorted semichair conformation with C2-carbon and nitrogen atoms residing above and below the naphthalene plane, leading to strain in the ring that allows ring-opening polymerization to take place. A few of the derivatives were found to possess anticancer activity. This current modest protocol affords numerous advantages such as mild reaction condition, shorter reaction time, operational simplicity, and excellent yield.     

Synthesis of 2,3-dihydro-1H-imidazo[1,2-b]pyrazoles

Two novel 2,3-dihydro-1H-imidazo[1,2-b]pyrazole derivatives 7 and 8 have been prepared by hydrazinolysis with 2,4-dinitrophenylhydrazine of 1-(benzylideneamino)-2-(2-ethoxycarbonyl-2-nitromethylidene)-imidazolidine 4 . The precursor 4 was conveniently prepared from ethyl nitroacetate and 1-(benzylidene-amino)-2-(methylthio)imidazoline 3 . Two examples are presented in which ethyl aceto(and trifluoroaceto)acetate 2-nitrophenyl-hyrazone, 9 and 10 , both of which also feature the β-hydrazinoacrylate arrangement, are refluxed in ethanol containing hydrochloric acid and thereby converted into pyrazolones 11 and 12 , pyrazoles 13 and 14 , and ketone 2-nitrophenylhydrazones 15 and 16 , respectively.     

微波无溶剂法合成香草醛氨基酸席夫碱

氨基酸席夫碱是制备特殊生物活性物质的重要中间体。氨基酸席夫碱中的亚胺(C=N)结构与亚磷酸烷基酯加成的化合物具有良好的抗植物病毒,除草,杀菌等性能[1-3]。氨基酸席夫碱中的羟基,羧基和亚胺等多个活性基团,可以与多种金属离子配位,其配合物具有抗菌,抗病毒,抗癌等性能[4-9],     

Synthesis and Ring Transformation of Pyrrolo[2,3-d][1,3]oxazine to Pyrrolo[2,3-d]Pyrimidines

A convenient route is reported for the synthesis of fused pyrrolo[2,3-d][1,3]oxazine and pyrrolo[2,3-d]-pyrimidine derivatives from 2-amino-1-benzyl-3-t-butoxycarbonyl]-4,5-dimethylpyrrole.     

Green synthesis of 1,3-diynes from terminal acetylenes under solvent-free conditions

Herein, we report the microwave-assisted synthesis of 1,3-diynes from terminal acetylenes, catalyzed by CuI and tetramethylethylenediamine, in the presence of air as the oxidant, at 100 °C for only 10 min under solvent-free conditions. This efficient methodology allowed the homocoupling of several terminal alkynes in moderate to excellent yields. Moreover, the same protocol was also applicable for the synthesis of some unsymmetrical 1,3-diynes through the cross-coupling reaction.     

Choline hydroxide promoted sustainable one-pot three-component synthesis of 1H-pyrazolo[1,2-a]pyridazine-2-carbonitriles under solvent-free conditions

Abstract

A sustainable one-pot three-component synthesis of novel 1H-pyrazolo[1,2-a]pyridazine-2-carbonitrile derivatives employing a highly efficient, biodegradable, and recyclable choline hydroxide catalyst under solvent-free conditions is demonstrated. The salient features of this protocol are simple workup, mild reaction conditions, short reaction time (10?min), excellent yields (up to 97%), high atom economy, column chromatography-free protocol, and eco-friendliness. Interestingly, the choline hydroxide was recycled up to five cycles without any considerable loss of efficiency. The structures of the products were deduced by their ¹H NMR, ¹³C NMR, and HRLC-MS spectra.     

CAN-catalyzed microwave promoted reaction of indole with Betti bases under solvent-free condition and evaluation of antibacterial activity of the products

CAN-catalyzed reaction of Betti bases with indoles under microwave irradiation gives 3-(α,α-diarylmethyl)indoles. Better yield of the products, especially when one of the aryl ring is phenol were achieved. The reaction is performed in solvent-free condition. The antibacterial studies of the synthesized compounds were performed and some of the compounds showed good activity against Methicillin-resistant Staphylococcus aureus bacteria.     

An efficient synthesis of imidazo[2,1-b][1,3]thiazins via a one-pot,three-component and solvent-free reaction

A simple and eco-friendly method for the synthesis of novel imidazo[2,1-b][1,3]thiazin derivatives has been developed via the one-pot, three-component and solvent-free reaction of thiohydantoins, aromatic aldehyde and 5,5-dimethylcyclohexane-1,3-dione in the presence of catalytic amount of p-toluene sulfonic acid, in good and excellent yields.     

Sc(OTf)3 catalysed multicomponent synthesis of chromeno[2,3-d]pyrimidinetriones under solvent-free condition

An efficient, simple, and environmentally friendly synthesis of a series of chromeno[2,3-d]pyrimidine-trione derivatives has been accomplished via the three-component reaction of a barbituric acid, dimedone/cyclohexane-1,3-dione, and aromatic aldehydes using Sc(OTf)₃ as a recyclable catalyst under solvent-free condition. This method exploits the use of Sc(OTf)₃ as a Lewis acid catalyst in organic synthesis and offers many rewards such as excellent product yield and easy work-up procedure. Harmless reaction conditions, as well as the absence of side-products, are another green aspects of this protocol.     

Efficient and green synthesis of 4H-pyrans and 4H-pyrano[2,3-c] pyrazoles catalyzed by task-specific ionic liquid [bmim]OH under solvent-free conditions

Abstract

A facile and convenient procedure for the synthesis of 4H-pyrans from aldehydes, malononitrile, and ethyl acetoacetate/acetylacetone and also synthesis of 4H-pyrano[2,3-c]pyrazoles from three-component condensation of aldehydes, malononitrile, and pyrazolone or four-component condensation of aldehydes, malononitrile, ethyl acetoacetate, and hydrazine monohydrate using [bmim]OH as task-specific ionic liquid has been described. The protocol proves to be efficient and environmentally benign in terms of high yields, low reaction times, ease of recovery, and reusability of reaction medium.

     

13C NMR spectra of 2,3-dihydro-1H-pyrrolo[1,2-c]imidazol-1,3-dione and its thione analogues

Analysis of the ¹³C NMR spectra of a series of 2,3-dihydro-1H-pyrrolo[1,2-c]imidazole derivatives has provided chemical shift data for (?184 ppm), (?173.5 ppm), (?158 ppm) and (?148 ppm) groups. A full analysis of the ¹³C chemical shifts of the C atoms of the pyrrole ring and of an N-phenyl substituent is described.     

Microwave assisted synthesis of 2,3-dihydro-4H-benzo[4,5]thiazolo[3,2-a]furo[2,3-d]pyrimidin-4-ones and 6,7-dihydro-5H-furo[2,3-d]thiazolo[3,2-a]pyrimidin-5-ones using Mn(OAc)3

2-Hydroxy-4H-benzo[4,5]thiazolo[3,2-a]pyrimidin-4-one 2a and 7-hydroxy-5H-thiazolo[3,2-a]pyrimidin-5-one 2b, were obtained in high yields under mild conditions from the cyclization reactions of bis-(2,4,6-trichlorophenyl) malonate and 2-aminobenzothiazole or 2-aminothiazole, respectively. A new class of compounds, 2,3-dihydro-4H-benzo[4,5]thiazolo[3,2-a]furo[2,3-d]pyrimidin-4-ones and 6,7-dihydro-5H-furo[2,3-d]thiazolo[3,2-a]pyrimidin-5-ones, were synthesized via the microwave assisted radical addition of compounds 2a and 2b to various alkenes using manganese(III) acetate. A preliminary acetylcholine esterase (AchE) inhibition test of compound 4e showed excellent (92%) inhibitory potential, comparable with the standard drug Donapezil®.     

1-Aryl-1-chloro-2,2,2-trifluoroethylisocyanates—convenient reagents for synthesis of 2-aryl-2-trifluoromethyl-2,3-dihydro-4H-benzo[e][1,3]oxazin-4-ones

1-Aryl-1-chloro-2,2,2-trifluoroethylisocyanates react with 3-alkoxyphenols to form N-(1-aryl-2,2,2-trifluoroethylidene)-O-(3-alkoxyphenyl)urethanes, which undergo intramolecular thermal cyclization into derivatives of 2-aryl-2-trifluoromethyl-2,3-dihydro-4H-benzo[e][1,3]oxazin-4-ones.     

Substituent effects in the ring-chain tautomerism of 1,3-diaryl-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines

Condensation of Betti base analogue amino naphthols with substituted benzaldehydes led to 1,3-diaryl-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines (3-9) which proved to be three-component (r¹-o-r²) tautomeric mixtures in CDCl₃ at 300 K. The electronic effects of the 3-aryl groups on the ratios of the ring-chain tautomeric forms at equilibrium could be described by the equation log K_X=ρσ⁺+log K_X=H. The value of the intercept was found to be strongly influenced by the steric arrangement of the 1,3-diaryl substituents.     

The synthesis of 5,6-dihydro-6-methylthiazolo-[2,3-b] [1,3] benzodiazepines, 2,3,10,11-tetrahydro-10-methyl-1H-cyclopenta[4,5] thiazolo[2,3-b] [1,3] benzodiazepine,and 7,8,9,10,12,13-hexahydro-13-methylbenzothiazolo[2,3-b] [1,3]-benzodiazepine via 1,3,4,5-tetrahydro-5-methyl-2H-1,3-benzodiazepine-2-thione

Catalytic reductive scission of 4-methylcinnoline (V) with Raney nickel afforded o-amino-β-methylphenethylamine (IV) in 57% yield. Treatment of IV with carbon disulfide followed by thermal cyclization of the product furnished 1,3,4,5-tetrahydro-5-methyl-2H-1,3-benzodiazepine-2-thione (III). Reaction of III with ethyl chloroacetate, ethyl 2-bromohexanoate, ethyl 2-chloroacetoacetate, 2-bromo-2′-methoxyacetophenone, and 2-bromoacetophenone provided a series of substituted 5,6-dihydro-6-methylthiazolo[2,3-b][1,3]benzodiazepines. Condensation of III with 2-chlorocyclopentanone and 2-chlorocyclohexanone gave 2,3,10,11-tetrahydro-10-methyl-1H-cyclopenta[4,5]thiazolo[2,3-b][1,3]benzodiazepine and 7,8,9,10,12,13-hexahydro-13-methylbenzothiazolo[2,3-b][1,3]benzodiazepine, respectively. Structure assignments are discussed. None of the compounds possessed appreciable biological activity.     

2,3-Dihydronaphtho[1,2-b]thiophene 1-oxides in the synthesis of 2,3-dihydronaphtho- and naphtho[1,2-b]thiophenes

2,3-Dihydronaphtho[1,2-b]thiophene 1-oxides, obtained by thermolysis of alkyl 1-naphthyl sulfoxides, are reduced by lithium aluminum hydride to 2,3-dihydronaphtho [1,2-b]thiophenes, whereas under the influence of acetic and trifluoroacetic anhydrides they form naphtho[1,2-b]thiophenes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1629–1633, December, 1989.     

Convenient synthesis of furo[2,3-c][1,2]dioxoles from 1-aryl-2-allylalkane-1,3-diones

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Iodine-Catalyzed,Rapid and Efficient,One-Pot Synthesis of 1,2-Dihydro-1-arylnaphtho[1,2e][1,3]oxazine-3-ones Under Solvent-Free Conditions

A mixture of β-naphthol, araldehydes, and urea in the presence of a catalytic amount of iodine as catalyst under solvent-free condition was heated for 5 min on a preheated hot plate to get the corresponding 1,2-dihydro-1-aryl-naphtho[1,2-e][1,3]oxazine-3-ones in very good yield.