Syntheses and photophysical properties of fluorescent 2-aryl-3-hydroxy-4-chromenones

The particle detectors proposed for the Super-conducting Super Collider contain polystyrene scintillation fibers as a component. Scintillation fluors soluble in styrene are required which have improved light output and response time. New 2-aryl-3-hydroxy-4-chromenones related to 3-hydroxyflavone were prepared which displayed these improved properties. Improved solvent systems for chromenone formation were essential in the synthesis of two of the chromenones. One chromenone produced fluorescence emission at 560 nm with a quantum yield of 0.53 and a scintillation decay time of 5 nsec.     

Syntheses of 2-acetyl-3-hydroxy-1-n-propylpyrrole from isomaltol and 1-n-alkyl-3-hydroxy-2-methyl-4-pyridones from maltol

2-Acetyl-3-hydroxyfuran (2) reacts with n-propylamine affording 2-acetyl-3-hydroxy-1-n-propylpyrrole (3) in 63% yield. The transformation of 2-methyl-3-hydroxy-4-pyrone (4) into 1-n-alkyl-3-hydroxy-2-methyl-4-pyridones is achieved by benzylation of the 3-hydroxyl group whereupon the product reacts with ammonia and the corresponding pyridone is obtained. The pyridone is alkylated with alkyl bromides and after hydrobromic acid in acetic acid cleavage of the 3-position ether function, 1-n-alkyl-3-hydroxy-2-methyl-4-pyridones are obtained in 48% overall yield.     

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.     

Syntheses of 5-hydroxy-2-(phenyl or styryl)chromones and of some halo derivatives

One-pot syntheses of 5-hydroxy-2-(phenyl or styryl)chromones and the corresponding 6- and 8-monoiodo- and 6,8-diiodochromones have been developed. The procedures involve oxidative cyclization of 2′-benzyloxy-6′-hydroxychalcones and 2′-benzyloxy-6′-hydroxy-2-cinnamylideneacetophenones and electrophilic substitution processes on the chromone moieties; such procedures were also applied to the syntheses of 6,8-dibromochromone derivatives.     

Asymmetric Syntheses of Osmundalactones and 5-Hydroxy-2-hexen 4-olides from 4-Benzyloxy-5-hydroxy-2（E）-hexenoate

( )-(4S,5R)-Osmundalactone 1 was isolated from the fungus Paxillus atrotomentosus (Paxillaceae) by Buchanan1. (-)-(4R,5S)-Osmundalactone 1 and ( )-(4R,5S)-5-hydroxy- 2-hexen-4-olide 2 were isolated from Osmunda japonica (Osmundaceae) as feeding inhibitors…     

Syntheses for 2-hydroxy-2H-1,4-benzothiazin-3(4H)-one derivatives as thio analogues of natural hemiacetals

Reductive cyclizations of methyl 2-(2-nitrophenylthio)acetate 2 by means of electrochemistry or by catalytic hydrogenation have been used as key steps in the syntheses of the hemiacetals 2-hydroxy-2H-1,4-benzothiazin-3(4H)-one 10 and its 4-hydroxy derivative 9 representing thio analogues of allelo chemicals found in Gramineae and Acanthaceae. In contrast to its natural counterpart 2,4-dihydroxy-2H-1,4-benzoxa-zin-3(4H)-one hydroxamic acid 9 did not undergo degradation by extrusion of formic acid.     

Regioselective synthesis of 1,5-diaryl-1H-imidazoles by palladium-catalyzed direct arylation of 1-aryl-1H-imidazoles

[reaction: see text] A variety of 1,5-diaryl-1H-imidazoles have been regioselectively synthesized by direct coupling of 1-aryl-1H-imidazoles with aryl iodides or bromides in DMF in the presence of CsF as the base and a catalyst precursor consisting of a mixture of Pd(OAc)2 and AsPh3. The data obtained in this synthetic study support a reaction mechanism involving an electrophilic attack of an arylpalladium(II) halide species onto the imidazole ring. Interestingly, some imidazole derivatives synthesized in this study have been found to exhibit significant cytotoxic activity against human tumor cell lines.     

天然产物1,3-二-(2-羟基-4-甲氧基苯基)丙烷和1,3-二-(2,4-二羟基苯基)丙烷的合成

1,3-二-(2-羟基-4-甲氧基苯基)丙烷(1)和1,3-二-(2,4-二羟基苯基)丙烷(2)是从菊叶薯蓣(Dioscorea composita Hemsl.)分离出来的天然产物, 以间苯二酚为起始原料, 分别经甲酰化和乙酰化得到2,4-二羟基苯甲醛和2,4-二羟基苯乙酮, 然后经选择性地甲基化、甲氧甲基化、羟醛缩合、还原、脱保护等步骤完成了上述两种天然产物的首次全合成. 产物通过¹H NMR, IR, MS进行了结构确证.     

Syntheses and characterization of new (2S)-2-hydroxy-1,4-oxazin-3-ones derived from β-aminoalcohols

The reactions of methyl glyoxylate hemiacetal 1 with 2-(methylamino)ethanol 2 , (1R,2S)-(–)-ephedrine 3 and (1S,2S)-(+)-pseudoephedrine 4 provide the (2S)-2-hydroxy-1,4-oxazin-3-ones 2a , 3a , 4a in good yield. They were characterized by ¹H, ¹³C, NMR, and infrared and mass spectroscopy. The structures of 2a and 3a were established by X-ray diffraction. The configuration of C₂ (S) is demonstrated by ¹H NMR data and confirmed for compounds 2a and 3a by single-crystal X-ray diffraction studies. © John Wiley & Sons, Inc.     

Stereoselective Synthesis of Substituted 2-(Z-Styrylsulfonyl)-1H-imidazoles and Benzothiazole

A novel method has been reported involving the synthesis of z-styryl sulfides by the reaction of phenylacetylene with 2-mercpto benzimidazoles and benzthiazole using NaOH as a base in absolute ethanol. On further oxidation with H₂O₂, these resulted in the formation of the desired styryl sulfones in good yields with retention of stereochemistry.     

New Syntheses of 2-Phenylsulphonylfurans

the synthesis of 2-phenylsulphonyltetrahydrofuran (1), 2-phenyl sulphonyl-5-methoxy-2,5-dihydrofuran (2) and 2-phenylsulphonylfuran (3) was carried out in very good yields and short reaction times starting from easily available precursors.     

Microwave-Assisted Syntheses of 2-Phenylbenzothiazoles

A new and easy synthetic route to 2-phenylbenzothiazoles has been achieved by direct thiation of benzoyl derivatives of aniline, various substituted anilines, and 1-naphthylamine under microwave irradiation. The oxidative cyclization using elemental sulfur in the presence of a catalytic amount of iodine is inexpensive and worked well for a number of anilides.     

嘌呤2位卤素取代衍生物的合成

嘌呤2位卤素取代衍生物的合成;嘌呤;重氮化;合成;杀菌活性     

Syntheses of methyl-2-furylketones

, -Dibromomethyl-2-furylketone and its 5-nitro derivatives are prepared by brominating the appropriate ketones in CCl₄.,-diiodomethyl-2-furylketone and its 5-nitro derivative are synthesized by the action of iodine on the appropriate diazoketones, and in the case of the 5-nitro derivative along with the diiodoketone is isolated the corresponding glyoxal. 5-Nitro-2-furylglyoxal is also obtained by the action of dimethylsulfoxide on bromomethyl-5-nitro-2-furylketone.For Part XII see [1]     

Syntheses of E-2-Nitroethenyltrimethylsilane

Three routes were explored for the conversion of tri-methylvinylsilane (1) to E-2-nitroethenyltrimethylsilane (2). In each case, 2 was afforded by base-induced vicinal elimination within the adducts arising from 1 plus (a) NO₂C1 (b) N₂O₄ or (c) HgC1₂ + NaNO₂.     

Syntheses of 2-Bromopyrene and 2-Hydroxypyrene

Regiospecific monobromination of 4,5,9,10-tetrahydropyrene in the 2-posiuon is accomplished in aqueous dimethylformamide. Conversion of the previously unknown 2-bromo-4,5,9,10-tetrahydropyrene to the title compounds is described.