An efficient synthesis of 1-cyanoacetyl-5-halomethyl-4,5-dihydro-1<Emphasis Type="Italic">H</Emphasis>-pyrazoles in ionic liquid

The synthesis of eleven 1-cyanoacetyl-5-hydroxy-5-halomethyl-4,5-dihydro-1H-pyrazoles from the reaction of 4-alkoxy-3-alken-2-ones f(R ³C(O)C(R ²) = C(R ¹)OR, where R ³ = CF₃, CCl₃, CHCl₂, CO₂ Et; R ²/R ¹ = H/H, H/Me, H/Et, -(CH₂)₄-, Me/H, H/Pr, and R = Me, Et) with cyanoacetohydrazide is reported. The reaction was carried out in the ionic liquid ([bmim][BF₄]) and molecular solvents. The results showed that when the ionic liquid was used as reaction medium, the reaction time was drastically decreased and the yield was improved. Correspondence: Marcos A. P. Martins, Núcleo de Química de Heterociclos – NUQUIMHE, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil.     

A facile and convenient approach to the synthesis of 3,5-diaryl-1H-pyrazoles

A simple and convenient one-pot synthesis route is described for the synthesis of 3,5-diaryl-1H-pyrazoles in short reaction times from the reaction of α-epoxyketones with semicarbazide hydrochloride under mild conditions.     

Facile and efficient synthesis of 2-substituted-N1-carbethoxy-2, 3-dihydro-4（1H）-quinazolinones in fluorous solvent

A facile, efficient and novel approach to access 2-substituted-N1-carbethoxy-2,3-dihydro-4（1H）-quinazolinones was developed by condensation of substituted N-carbethoxyanthranilamide with alkyl, aromatic or heteroaromatic aldehydes in the refluxing 2,2,2- trifluoroethanol or hexafluoroisopropanol using p-toluenesulfonic acid as catalyst.     

A novel synthesis of 5-perfluorophenyl 4,5-dihydro-1H-pyrazoles in THF or water

5-Perfluorophenyl 4,5-dihydro-1H-pyrazoles were synthesized from 1,3-dipolar cycloaddition reaction of perfluorobenyl 2,4,6-triisopropylbenzenesulfonylhydrazone and α,β-unsaturated carbonyl compounds or acrylonitrile in THF or water. It was worthy to note that better results were obtained when water was employed as the solvent, which was considered as an effective, economic and environmentally friendly method to synthesize these pyrazole derivatives.     

Five-membered 2,3-dioxo heterocycles: LXXVI. Reaction of methyl 1-aryl-3-benzoyl-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates with 6-amino-1,3-dimethylpyrimidine-2,4(1H,3H)-dione

Methyl 1-aryl-3-benzoyl-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates reacted with 6-amino-1,3-dimethylpyrimidine-2,4(1H,3H)-dione to give methyl 11-aryl-12-benzoyl-9-hydroxy-4,6-dimethyl-3,5,10-trioxo-4,6,8,11-tetraazatricyclo[7.2.1.0^2,7]dodec-2(7)-ene-1-carboxylates which underwent thermal recyclization to 1-aryl-3-benzoyl-4-hydroxy-1′,3′-dimethylspiro[pyrrole-2,5′-pyrrolo[2,3-d]pyrimidine]-2′,4′,5,6′(1H,1′H,3′H,7′H)-tetraones.     

An efficient three‐component synthesis of hexahydroquinoline derivatives in ionic liquid

A series of hexahydroquinoline derivatives were synthesized by the three‐component reaction of 5,5‐dimethyl‐3‐aminocyclohex‐2‐enone, aromatic aldehyde, and acyl acetonitrile in ionic liquid without using any catalyst. This protocol has the advantages of easier work‐up, milder reaction conditions, high yields, and environmentally benign procedure. J. Heterocyclic Chem., (2011).     

An efficient green synthesis of xanthenedione derivatives promoted by acidic ionic liquid

Xanthenedione derivatives were prepared through the condensation reaction of aromatic aldehydes with 5,5‐dimethyl‐1,3‐cyclohexanedione promoted by acidic ionic liquid. The reaction time was 20–40 min with the yields between 82.3% and 95.3%. It was shown that the proposed method was fast, high efficient, and environmentally benign. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:609–611, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20486     

Synthesis and Dynamic NMR Spectroscopic Study of Dialkyl 4-Ethoxy-1-(1-naphthyl)-5-oxo-4,5-dihydro-1 H-pyrrole-2,3-dicarboxylates

Protonation of the reactive 1:1 intermediate produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates with ethyl 2-(1-naphthylamino)-2-oxoacetate, leads to a vinylphosphonium salt, which undergoes intramolecular Wittig reaction to produce dialkyl 4-ethoxy-1-(1-naphthyl)-5-oxo-4,5-dihydro-1H-pyrrole-2,3-dicarboxylates in excellent yields. A dynamic NMR effect is observed in the ¹H NMR spectra of the title compounds as a result of restricted rotation around the single bond linking the naphthalene moiety and the heterocyclic system, which is attributed to the peri interaction between the pyrrole residue and the peri CH group. The free energy of activation (G ) for this process is 58±2kJmol^–1.     

Five-membered 2,3-dioxo heterocycles: LXXXII. Recyclization of dimethyl 4,5-Dioxo-4,5-dihydro-1H-pyrrole-2,3-dicarboxylates in reaction with monosubstituted hydrazines. crystalline and molecular structure of dimethyl 1-benzyl-5-(4-methylphenylcarbamoyl)-1H-pyrazole-3,4-dicarboxylate

Dimethyl 1-aryl(benzyl)-4,5-dioxo-4,5-dihydro-1H-pyrrole-2,3-dicarboxylates reacted with phenylhydrazine and benzylhydrazine to give dimethyl 1-aryl(benzyl)-5-[(aryl or benzyl)carbamoyl]-1H-pyrazole-3,4-dicarboxylates.     

An efficient synthesis of 3-arylmethyl-7,8-dihydro-6H-chromene-2,5-diones from Baylis–Hillman adduct acetates under solvent-free conditions

A simple, efficient synthesis of 3-arylmethyl-7,8-dihydro-6H-chromene-2,5-dione 4 from Baylis–Hillman adduct acetates derived from aromatic aldehydes and cyclohexane-1,3-diones under solvent-free conditions is described. Interestingly, when Baylis–Hillman adducts derived from aliphatic aldehydes were tested under the similar conditions, the unexpected stereoisomers 5 and 6 were obtained in moderate yields. A plausible mechanism for the formation of 4–6 is proposed.     

Use of Vilsmeier reagent for the solid-phase synthesis of 1,5-disubstituted 4,5-dihydro-1H-imidazoles and disubstituted 4,5-dihydro-1H-imidazolylbenzimidazoles

The solid-phase synthesis of novel imidazolines and dihydroimidazolylbenzimidazoles is described. Resin-bound diamines, derived from resin-bound N-acylated amino acid amides, were cyclized using Vilsmeier reagent to yield imidazolines following cleavage. Similarly, cyclization of resin-bound tetraamines having two secondary amines and an o-dianiline yielded dihydroimidazolylbenzimidazoles following cleavage.     

An efficient synthesis of anti-microbial 1,2,4-triazole-3-thiones promoted by acidic ionic liquid

Acidic ionic liquid, [(Py)₂SO][HSO₄]₂ has been used as an efficient catalyst for the reaction of ketone with thiosemicarbazide in ethanol at room temperature for the eco-friendly synthesis of spiro-1,2,4-triazolidine-3-thiones. Smooth reactions, ambient temperature, use of alcohol as a solvent, high yields, easy work-up procedure and excellent recyclability of ionic liquid and high atom economy are the auxiliary advantages of the present protocol, which makes it ecofriendly. All the synthesized 1,2,4-trioazoles were screened for antimicrobial activity. Most of compounds displayed moderate to good biological activity.     

The convenient synthesis of 4-arylmethylidene-4,5-dihydro-3-phenylisoxazol-5-ones

4-Arylmethylidene-4,5-dihydro-3-phenylisoxazol-5-ones were synthesized by the convenient three-component reaction of ethyl benzoylacetate,hydroxylamine and aromatic aldehydes in the presence of pyridine.The target compounds were also obtained by the reaction between 3-phenylisoxazol-5-one and aromatic aldehydes at 105℃under solvent free condition.Yields of products depended considerably on the aldehyde used.     

Highly stereoselective iodolactonization of 4,5-allenoic acids--an efficient synthesis of 5-(1'-iodo-1'(Z)-alkenyl)-4,5-dihydro-2(3H)-furanones

In this paper, it is reported that the efficient iodolactonization of 4,5-allenoic acid with I2 in cyclohexane in the presence or absence of K2CO3 afforded 5-(1'-iodo-1'(Z)-alkenyl)-4,5-dihydro-2(3H)-furanones highly stereoselectively. However, the reaction of axially optically active 4,5-allenoic acids (R)-(-)-5 a and (R)-(-)-5 b with I2 afforded the corresponding products with a serious loss of chirality. This problem was solved by conducting the iodolactonization with N-iodosuccinimide in CH2Cl2 in the presence of Cs2CO3; however, the Z/E selectivity is somewhat lower. The pure optically active Z products were prepared by subsequent kinetic resolution with Sonogashira coupling. The reaction of the substrates with a substituent at the 3-position of the starting 4,5-allenoic acids afforded the trans-4,5-disubstituted gamma-butyrolactones as the only products. The reaction of the 4,5-allenoic acids (S)-(+)-1 l, (R)-(-)-1 l, and (S)-(+)-1 m with a center chirality at the 3-position afforded the trans products with very high enantiopurity and up to 98:2 Z/E selectivity regardless of the axial chirality of the allene moiety.     

Regioselective synthesis of 6-halomethyl-5,6-dihydro-4H-1,2-oxazines based on cyclizations of arylalkenyl-oximes

6-Iodo- and 6-bromomethyl-5,6-dihydro-4H-1,2-oxazines were prepared by condensation of dilithiated acetophenone-oximes with allylbromide and subsequent regioselective iodine- or NBS-mediated cyclization.     

A novel and efficient ionic liquid supported synthesis of oligosaccharides

A novel and efficient ionic liquid supported synthesis of oligosaccharides with a general protocol of coupling and purification is described. The method represents an attractive alternative to the classical solid- and fluorous-phase synthesis strategies and combines the advantage of performing homogeneous chemistry on a relatively large scale while avoiding large excesses of reagents.     

An efficient synthesis of novel 1,3-oxazolo[4,5-d]pyridazinones

A convenient and versatile synthetic approach to substituted 1,3-oxazolo[4,5-d]pyridazinones is developed. The oxazole ring was formed upon reaction of 5-amino-4-hydroxy-3(2H)-pyridazinone with various carboxylic acid derivatives using a microwave-assisted procedure, which favors the reaction time and purity of the resulting products. The developed methodology is suitable for rapid, parallel, automated synthesis of oxazolopyridazinone libraries.     

The first 2,3-dihydro-1H-[1,2,4] triphosphole

Protonation of the lithium triphospha-cyclopentenyl salt Li (P₃C₂Bu^t₂RR′) (R=(Me₃Si)₂CH-, R′=Buⁿ) with HCl affords the new 2,3-dihydro-1H-[1,2,4] triphosphole P₃C₂Bu^t₂(H) (Buⁿ)CH(SiMe₃)₂ which has been structurally characterised as its [W(CO)₅] complex.     

An efficient synthesis of some thiopyranopyrazole-heterocycles via domino reaction in a Brønsted acidic ionic liquid

The thiopyrazole gave many new polycyclic thiopyranopyrazole-heterocycles when it was assembled with a variety of O-alkenylated/alkynylated salicylaldehydes and naphthaldehydes in Brønsted acidic ionic liquid, [Hmim]HSO₄, via domino/Knoevenagel–hetero-Diels–Alder (DKHDA) reaction. The reaction is highly stereoselective and the work-up procedure required no chromatography of products in many cases.