Novel synthesis of 4-chloro-3-hydroxy-2-pyrone by the reaction of acetonide protected 4,5-dihydroxy-2-chloroglycidic ester with magnesium chloride

Treatment of acetonide protected 4,5-dihydroxy-2-chloroglycidic ester with magnesium chloride gave 4-chloro-3-hydroxy-2-pyrone in excellent to good yields.     

Synthesis of 2-hydroxy-3-substituted naphthoquinones using the Heck reaction

An efficient Heck coupling of 2-hydroxy-3-iodo-naphthoquinone with a series of electron-deficient alkenes in aqueous solution has been accomplished. The method is characterized by simple conditions and facile work-up to isolate the products in good to excellent yields. The products contain the motif present in several naphthoquinone pigments but with enhanced polarity.     

Efficient stepwise and one pot three-component synthesis of 2-amino-4-(2-oxo-2H-chromen-3-yl)thiophene-3-carbonitriles

Environmentally benign conditions have been developed for the synthesis of 2-amino-4-(2-oxo-2H-chromen-3-yl)thiophene-3-carbonitriles (3) starting from 3-acetyl-2H-chromen-2-one (1) through the intermediacy of 2-(1-(2-oxo-2H-chromen-3-yl)ethylidene)malononitrile (2) using the Knoevenagel condensation followed by the Gewald reaction. Alternatively, 3 could also be prepared in a one pot method by treating equimolar amounts of 1, malononitrile, and elemental sulfur. The merits of this preparation are mild reaction conditions, easy work-up procedure, and good yields.     

Novel tetradentate chelators derived from 3-hydroxy-4-pyridinone units: synthesis, characterization and aqueous solution properties

The synthesis and characterization of three novel tetradentate ligands (T1, T2 and T3) based on 3-hydroxy-4-pyridinone chelating units are described. The three ligands exhibit different flexibility due to the use of two different anchor molecules, piperazine and 1,2-diaminobenzene, and to the diverse length of the 3-hydroxy-4-pyridinone arms. All reactions were performed using both conventional heating and microwave irradiation in order to evaluate the possibility of using greener methods in these synthetic procedures. The results showed that, in all cases, microwave irradiation provides the desired ligands reducing reaction time in ca. 97%. The structure of ligand T3 was resolved by X-ray crystallography, showing significant hydrogen bonding and interesting π-π interaction between the benzene and pyridinone rings. The use of potentiometric and spectroscopic methods allowed determination of acidity constants and unequivocal assignment of proton loss for each pK_a value. Interaction of the ligands with divalent metal ions was assessed by spectroscopic methods.     

Molecular structure of complexes with a bifurcated hydrogen bond. 5. Dimers of 3-hydroxy-2-methyl-4-pyrone in inert media

According to the data from IR spectroscopy and quantum-chemical calculations (B3LYP/6-31G**, B3LYP/6-311G*), in the vapor and in dichloroethane the synperiplanar conformer of 3-hydroxy-2-methyl-4-pyrone (maltol) exists in equilibrium with two types of dimers. The hydrogen atom of the hydroxy group of one them participates in the formation of a three-center bifurcated hydrogen bond. The second isomer is formed by means of two such H bonds, the intramolecular component of which is substantially weakened while the intermolecular component is so strong that it approximates in character to a two-center hydrogen bond. Dedicated to Academician of the Russian Academy of Sciences M. G. Voronkov on his 85th birthday. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1635–1646, November, 2006.     

Nanosized magnesium oxide as catalyst for the rapid and green synthesis of substituted 2-amino-2-chromenes

A nanosized magnesium oxide catalyzed three-component condensation reaction of aldehyde, malononitrile, and α-naphthol proceeded rapidly in water-PEG to afford corresponding 2-amino-2-chromenes in high yields at room temperature. The greener protocol was found to be fairly general and the catalyst was reused in subsequent reactions with consistent activity.     

T3P catalyzed one pot three-component synthesis of 2,3-disubstituted 3H-quinazolin-4-ones

An efficient methodology for the synthesis of 2,3-disubstituted 3H-quinazolin-4-ones is described via one-pot three component reaction from anthranilic acid using T3P as catalyst. Mild reaction conditions, short reaction time, broad functional group tolerance, easy isolation of products and good yields are main advantages of this protocol.     

Ultrasound promoted enantioselective transesterification of 3-hydroxy-3-(2-thienyl) propanenitrile catalyzed by lipase

(S)-3-hydroxy-3-(2-thienyl) propanenitrile, which is the key chiral building block for the synthesis of (S)-duloxetine, was successfully prepared via enantioselective transesterification catalyzed by lipase under ultrasound irradiation. Compared with conventional shaking, the enzyme activity and enantioselectivity were dramatically enhanced under ultrasound irradiation. Under optimum reaction conditions (solvent: n-hexane, ultrasound power: 150?W, a_w: 0.33, temperature: 40°C), Pseudomonas sp. lipase exhibited an excellent catalytic performance (enzyme activity: 81.5?μmol?g^?1?min^?1, E-value: 65.4). The reaction achieved its equilibrium in approximately 7?h with a conversion of 53.9% and high enantiopurity (99% ee) of (S)-3-hydroxy-3-(2-thienyl) propanenitrile could be obtained.     

Microwave assisted rapid,catalyst-free,and efficient synthesis of a new class of diversely functionalized 3-hydroxy-2-oxindole scaffolds under aqueous reaction media

An efficient and rapid synthesis of a new class of diversely functionalized 3-substituted, 3-hydroxy-2-oxindoles scaffolds in catalyst-free conditions is described by the reaction of 1,3-diketone with isatins under microwave irradiation in aqueous medium. The generality of the reaction to afford the γ regioselective aldol addition products is well demonstrated by screening different structurally varied 1,3-diketone nucleophiles as well as isatin electrophiles. Simple reaction condition, good isolated yield of the product, and environmentally benign medium are attractive features of the present protocol.     

3-Alkenyl-5-chloropyrazoles: expedient synthesis via heterocyclization of 1,1-dichloro-4-halo-1-alken-3-ones with hydrazines

Synthesis of hard-to-reach 5-chloro-3-alkenylpyrazoles was developed via heterocyclization of alkyl-, benzyl- or dialkylhydrazines with 1,1-dichloro-4-halo-1-alken-3-ones obtained from haloacyl chlorides and vinylidene chloride. The reaction process includes the formation of intermediate 5-chloro-3-(1-haloalkyl)pyrazoles followed by dehydrohalogenation.     

A convenient synthesis of methyl 2-hydroxy-4-oxo-4-(substituted phenyl) butanoates from malic acid

A synthesis of methyl 2-hydroxy-4-oxo-4-(substituted phenyl)butanoates has been accomplished using Friedel-Crafts acylation of substituted benzenes with 2-acetoxybutanoyl chloride.The key feature of this strategy is that various 4-arylbutanoates can be obtained conveniently,which are important intermediates for the synthesis of biologically active compounds including ACE inhibitors.     

Dehydration of 4-hydroxy-4-methyl-3-phenylamino-oxazolidin-2-ones

The dehydration of two 5,5-disubstituted 4-hydroxy-4-methyl-3-phenylaminooxazolidin-2-ones into the corresponding 4-methylene-3-phenylaminooxazolidin-2-ones has been carried out. The structure of the products was confirmed by X-ray diffraction analysis.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1512–1517, October, 2004.     

双(2-取代-3-羟基-4-吡喃酮)合铜(II)配合物的合成和降血糖作用

合成了双(2-取代-3-羟基-4-吡喃酮)合铜(II)配合物, 采用元素分析、质谱、红外光谱、电子光谱、电子自旋共振谱表征了它们为平面正方型配合物, 中心离子和配体的物质的量比为1∶2. 在STZ-糖尿病小鼠模型上, 其中双(2-乙基-3-羟基-4-吡喃酮)合铜(II)在10 mg/kg的剂量下灌胃给药, 能增加血清胰岛素的合成和分泌、降低糖尿病小鼠的血糖水平, 显示出良好的抗糖尿病的作用. 该配合物毒性低, 对正常小鼠灌胃给药的半数致死量LD₅₀是855.9 mg/kg.     

双(2-取代-3-羟基-4-吡喃酮)合铜(II)配合物的合成和降血糖作用

合成了双(2-取代-3-羟基-4-吡喃酮)合铜(II)配合物,采用元素分析、质谱、红外光谱、电子光谱、电子自旋共振谱表征了它们为平面正方型配合物,中心离子和配体的物质的量比为1∶2.在STZ-糖尿病小鼠模型上,其中双(2-乙基-3-羟基-4-吡喃酮)合铜(II)在10mg/kg的剂量下灌胃给药,能增加血清胰岛素的合成和分泌、降低糖尿病小鼠的血糖水平,显示出良好的抗糖尿病的作用.该配合物毒性低,对正常小鼠灌胃给药的半数致死量LD50是855.9mg/kg.     

Novel Dispersion of MWCNTs in Polystyrene Polymer Induced by the Addition of 3-Hydroxy-2-Napthoic Acid

This article reports an extensive investigation of the unique dispersion behavior of solutions with multi-walled carbon nanotubes (MWCNTs) and 3-hydroxy-2-napthoic acid (β-HNA) in tetrahydrofuran (THF) solvent, which results into a multifold enhancement in the electrical properties of polystyrene (PS). A number of solutions with 0.4% of MWCNTs (w/v) and β-HNA (0–1%, w/v) in THF were prepared separately. MWCNTs precipitated out in THF solvent shortly after the preparation and formed two distinct phase regions (2φ). Gratifyingly, addition of β-HNA solution to the MWCNTs solution offered an unprecedented enhancement in the dispersion of MWCNTs. Such dispersion in solutions with only 0.02% β-HNA (w/v) was found to be stable up to 2 weeks at room temperature. FTIR spectroscopy was incorporated to illustrate the adsorption of β-HNA onto the surface of carbon nanotubes (CNTs). After this successful dispersion, nanocomposites solutions comprising of 0.067% β-HNA (w/v), 6.7% PS (w/v), and varying concentrations of MWCNTs (0–0.33%, w/v) were prepared. A remarkable dispersion behavior of MWCNTs in the presence of polymer was also observed. Finally, thin films made up of consistent polystyrene/β-HNA concentrations and increasing amounts of MWCNTs were prepared by casting technique to investigate the influence of dispersion on the electrical properties of the film. The dispersion significantly affected the DC electrical conductivity and incorporation of 5% MWCNTs elevated the electrical conductivity up to 10 orders of magnitude with respect to neat PS.     

Separation of enantiomers and diastereomers of 4-hydroxy-2H-1,4-benzoxazin-3(4H)-one derivatives by capillary electrophoresis

Summary A high performance capillary electrophoresis (HPCE) procedure for the enantioseparation of the methyl acetals3 and4 of the natural products DIBOA1 and DIMBOA2, respectively, has been developed using borate buffers (pH 9–10 range), cyclodextrins as chiral additives and addition of up to 20% methanol. A mixture of GDIBOA5 and GDIMBOA6 of natural origin was also clearly separated. HPCE proved to be superior to HPLC by the first separation of GDIBOA5 and three of its diastereomers resulting from a synthetic approach to this acetalglucoside.     

A new and efficient one-pot synthesis of 2-hydroxy-1,4-dihydrobenzoxazines via a three-component Petasis reaction

The secondary amines synthesized by the reaction between 2-aminophenols and aromatic aldehydes, via the reduction of the corresponding imines, were employed in the synthesis of new 2-hydroxy-2H-1,4-benzoxazine derivatives through a one-pot Petasis multicomponent reaction in good to excellent yields.     

Synthesis of chiral β-3-amino-2-hydroxyalkanoates and 3-alkyl-3-hydroxy-β-lactams by double asymmetric induction

Reactions of chiral (2S)-enolates of dioxolan-4-ones, derived from lactic, mandelic, and phenyllactic acids, with aliphatic (S_S)- and (S_R)-tert-butylsulfinyl aldimines afforded conformationally restrained C2-disubstituted N,O-orthogonally protected 3-amino-2-hydroxyalkanoates in the form of N-sulfinyl protected 1′-aminodioxolan-4-ones. The product distribution showed that there is significant kinetic selectivity, due to the presence of ‘matched’ and ‘mismatched’ components, between the (S)- or (R)-tert-butylsulfinyl aldimines and the (2S)-enolates of the 1,3-dioxolan-4-ones. Selective methoxide-induced removal of the acetal group of the N-sulfinyl-1′-aminodioxolanones yielded the corresponding N-sulfinyl protected methyl alkanoates. In addition, the selective acid-induced removal of the sulfinyl group of the N-sulfinyl-1′-aminodioxolanones provided the corresponding N-unprotected 1′-aminodioxolanones, whose base-induced cyclization afforded the corresponding β-lactams.     

Syntheses and crystal structures of diorganotin (IV) moieties with 3-hydroxy-2-pyridinecarboxylic acid

A series of new organotin (IV) complexes with 3-hydroxy-2-pyridinecarboxylic acid (3-OH-2-picH) of two types: R₂SnCl(3-OH-2-pic) (I) (R = Me 1, n-Bu 2, Ph 3, PhCH₂4) and R₂ Sn(3-OH-2-pic)₂ (II) (R = Me 5, n-Bu 6, Ph 7, PhCH₂8)have been synthesized by reactions of diorganotin (IV) dichloride with 3-hydroxy-2-pyridinecarboxylic acid in the presence of sodium ethoxide. All complexes are characterized by elemental analyses, IR spectra and NMR spectra analyses. Among them, complexes 1, 5, 6 and 7 are also characterized by X-ray crystallography diffraction analyses. Complex 1 is a 1D polymeric chain with six-coordinate tin atoms and the packing of complex 1 is stabilized by the C-H?Cl intermolecular weak interactions, thus a 2D network of 1 is formed. Complex 5 is also a 1D polymeric chain with seven-coordinate tin atoms. Complex 6 is a zigzag polymeric chain linked by Sn?O intermolecular weak interactions. Complex 7 is a monomeric complex with distorted octahedral geometry.     

Camps reaction for the synthesis of 3-RS-4-arylquinolin-2-ones

The replacement of the chlorine atom in 2-(chloroacetamido)benzophenones on treatment with RSH (R = Alk, Ar, Hetaryl) in the presence of MeONa is accompanied by intramolecular cyclization following the Camps reaction pattern to give 3-RS-4-arylquinolin-2-ones. Cleavage of 4-aryl-3-(benzoxazol-2-ylthio)quinolin-2-ones by morpholine has resulted in the corresponding 4-aryl-3-mercaptoquinolin-2-ones.