Synthesis of 2H-chromeno[2,3-d]pyrimidine-2,4-(3H)-diones (10-Oxa-5-deazaflavins) and their use in the oxidation of benzyl alcohol

Treatment of 6-phenoxyuracil derivatives with the Vilsmeier reagent (dimethylformamide-phosphorus oxy-chloride) gave the corresponding 5-formyl-6-phenoxyuracil derivatives or their equivalents (5-dimethylamino-methylene-6-phenoxyuracil derivatives). Dehydrative cyclization of the above 5-formyluracils or 5-dimethyl-aminomethyleneuracils with polyphosphoric acid gave the corresponding 2H-chromeno[2,3-d]pyrimidine-2,4(3H)-diones (10-oxa-5-deazaflavins). These 10-oxa-5-deazaflavins showed strong oxidizing power in oxidizing benzyl alcohol even under neutral conditions (without base) to give benzaldehyde, while they were hydro-genated to 1,5-dihydro-10-oxa-5-deazaflavins.     

Synthesis of some 8-substituted 5-deazaflavins

Treatment of 8-fluoro-3,10-dimethyl-5-deazaflavin (Ia) with ethyl cyanoacetate in ethanol in the presence of potassium carbonate gave the corresponding 8-(1-cyano-1-ethoxycarbonylmethyl)-5-deazaflavin, which was converted into 3,8,10-trimethyl-5-deazaflavin by refluxing in aqueous dimethylformamide. Treatment of Ia with sodium azide in ethanol yielded 8-azido-3,10-dimethyl-5-deazaflavin (V). Compound V was converted into the corresponding 8-amino-, 8-acetamido-, and 8-benzamido-5-deazaflavins by heating in high boiling alcohols, acetic anhydride, and benzoic anhydride, respectively. Fusion of compound V with dimethyl acetylenedicarboxylate yielded 4,5-bis(methoxycarbonyl)-1-(3,10-dimethyl-5-deazaflavin-8-yl)-1,2,3-triazole.     

Synthesis of 8-substituted 5-deazaflavins

To obtain 5-deazaflavins exhibiting red-shifted light absorption spectra, a number of C(8) substituted 5-deazaisoalloxazines were synthesized. This was accomplished a) by the oxidative cyclization of 5,5′-arylmethylenebis(6-methylaminouracil) derivatives and b) by the cyclization of N-methylanilinouracil derivatives with a one-carbon reagent. The latter method led to the formation of impure products. Condensation and oxidation reactions with the π-electron deficient C(8) methyl group in 5-deazalumiflavin did not occur. Introduction of substituents at the C(8) position caused a bathochromic shift that varied between 10 and 40 nm.     

Synthesis of water soluble 8-substituted 5-deazaflavins

By oxidative cyclization of 5,5′-arylmethylenebis(6-methylaminouracil) derivatives with diethyl azodicarb-oxylate a number of 5-deazaisoalloxazines were synthesized having at the C(8) position a substituent that causes a bathochromic shift varying between 20 and 130 nm, depending on the substituent. To increase the solubility in aqueous media 8-substituted 5-deazaflavins were prepared having a carboxymethyl group at the N(3) position. The carboxymethyl group was introduced prior to the oxidative cyclization.     

Synthesis of FeNi3 nanoparticles in benzyl alcohol and their electrical and magnetic properties

Pure and highly crystalline FeNi₃ alloy nanoparticles (NPs) were synthesized via sol–gel route with benzyl alcohol, using hydrazine as a reduction reagent without the usage of additional surfactant molecules nor further annealing processes. The structural studies revealed that the particle size is of ca. 200 nm, whose structure consisted on aggregation of small crystallites of about 13 nm. The magnetic properties of the as-synthesized NPs were similar to the bulk with a saturation magnetization of 95 emu g^?1. Moreover, the coercive field was ca. 50 G, exhibiting a M _r /M _s ratio of 0.03, indicative of soft ferromagnetism. The electrical transport in the temperature range 2–300 K exhibits a typical ferromagnetic metallic behaviour. Finally, similar FeNi₃ NPs were synthesized in EtOH/H₂O mixtures in the presence of sodium dodecyl sulphate molecules as surfactant for comparative purposes, exhibiting a typical half hard magnetic behaviour, highlighting the interest of the reported benzylic route.     

含硝基咔唑类有机电催化剂的合成及其对醇的电催化氧化

有机小分子的电催化氧化是催化领域的一个重要研究内容.通过醇的选择性氧化合成相应醛或酮类化合物在精细化学品和有机化学中间体的合成领域均具有十分重要的意义.有机电催化合成用电子代替强氧化还原剂,可以使反应在比较温和的条件下进行.但在直接电氧化合成反应中,电极表面容易生成有机聚合物膜,使电极钝化,电流效率急剧下降.而在电子转移媒质作用下的有机电催化反应不仅可以避免电极表面钝化,还可以控制目标产物的过度氧化.三芳胺类化合物是一类新型的电氧化还原媒质,由于其具有较宽的电化学氧化还原电位已引起研究者的广泛关注.咔唑类化合物相比于三芳胺类具有更好的平面性,使得取代基效应更为显著.咔唑类化合物被广泛作为荧光材料,但用于电化学方面的研究很少.本文通过在咔唑类化合物中引入具有强吸电子性的硝基以提高该类化合物的氧化电位,并将其作为有机电催化媒质,采用间接电化学氧化的方式,在室温下研究醇的电化学催化氧化反应,合成相应醛类化合物.
　　我们合成了三种含硝基咔唑类有机电催化剂,通过1H NMR对其结构进行了鉴定.采用循环伏安法测试了该类有机电催化剂的电化学氧化还原性能.发现取代基的电子效应对有机电催化剂的氧化还原电位及电化学氧化还原可逆性有很大的影响,供电子基(–OCH3)的引入使氧化电位负移(0.717 V),吸电子基(–Br)的引入使氧化电位明显正移(1.282 V).同时,取代基的引入有效改善了有机电催化剂的电化学可逆性,从而可以作为有效的电氧化还原媒质应用于电化学氧化反应中.而当把化合物中的NO2还原为NH2后,咔唑类化合物的电化学氧化还原可逆性完全消失,表明硝基的引入对咔唑类有机电催化剂的电化学性能有很大的影响.
　　循环伏安结果发现,在咔唑类硝基化合物的作用下,对甲氧基苯甲醇(p-MBzOH)的电化学氧化峰电位从1.350 V降至1.286 V,表明可以在较低电位下进行电解,有效降低了电氧化反应的能耗,同时氧化峰电流明显增加,说明该类有机电催化剂对p-MBzOH具有良好的电催化性能.随着p-MBzOH浓度的增加,氧化峰电流也明显增大,说明在咔唑类有机电催化剂的作用下, p-MBzOH可以在比较高的浓度下进行电化学氧化电解.通过对不同对位取代基的苯甲醇类化合物进行循环伏安研究,发现含硝基咔唑类化合物对具有较高氧化电位的反应底物均表现出良好的电催化氧化性能.
　　在含硝基咔唑类有机电催化剂的氧化电位(1.28 V)和室温下,对不同浓度的p-MBzOH进行恒电位电解6 h,发现当催化剂的用量为底物的2.5 mol%时, p-MBzOH可以完全转化为相应的醛类目标产物.而且恒电位电解后分离回收的含硝基咔唑类有机电催化剂仍具有良好的电化学氧化还原可逆性.     

Synthesis of 2-amino-2-deoxo-5-deazaflavins and related compounds

10-Alkyl-2-amino-2-deoxo-5-deazaflavins were prepared by the condensation of 2-amino-6-chloro-5-formylpyrimidin-4(3H)-one with the corresponding N-alkylanilines. 2-Amino-10-p-tolyl-2-deoxo-5-deazaflavin was prepared by the condensation of 2-amino-6-p-toluidinopyrimidin-4(3H)-one with o-chlorobenzaldehyde. Some reactivities of 2-aminopyrimidin-4(3H)-ones are described.     

5-烃基-5-对甲苯磺酰氧基丙二酸亚异丙酯的合成

报道了利用羟基(对甲苯磺酰氧基)碘苯与5-烃基丙二酸亚异丙酯的反应合成5-烃基-5-对甲苯磺酰氧基丙二酸亚异丙酯的方法。提出了该反应的可能机理。     

Kinetics of oxidation of benzyl alcohol by sodium N-chloro-p-toluenesulfonamide

The kinetics of oxidation of benzyl alcohol and substituted benzyl alcohols by sodium N-chloro-p-toluenesulfonamide (chloramine-T, CAT) in HClO₄ (0.1–1 mol/dm³) containing Cl^? ions, over the temperature range of 30–50°C have been studied. The reaction is of first order each with respect to alcohol and oxidant. The fractional order dependence of the rate on the concentrations of H⁺ and Cl^? suggests a complex formation between RNCl^? and HCl. In higher acidic chloride solution the rate of reaction is proportional to the concentrations of both H⁺ and Cl^7hyphen;. The observed solvent isotope effect (k/k) is 1.43 at 30°C. The reaction constant (p = ?1.66) and thermodynamic parameters are evaluated. Rate expressions and probable mechanisms for the observed kinetics have been suggested.     

Kinetics and mechanism of the oxidation of benzyl alcohol by potassium chlorochromate

The kinetics of the oxidation of benzyl alcohol by potassium chlorochromate, KCrClO₃, has been studied in dimethyl sulfoxide-dichloromethane medium. The reaction is catalyzed by acid. The effects of temperature and solvent composition were studied and activation parameters evaluated. Probable mechanisms are discussed.

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, KCrClO₃, . . . .

     

Synthesis of some 2-alkyl-4-quinolone and 2-alkyl-4-methoxyquinoline alkaloids

Acid-catalyzed condensation of a series of 3-oxoalkanoic acid esters with aniline affords the corresponding 2-alkyl-4-quinolones in good yield. Treatment of these compounds with methyl iodide affords 2-alkyl-4-methoxyquinolines and 2-alkyl-N-methylquinolones. Three of the compounds are naturally-occurring alkaloids which are synthesized here for the first time.     

5-(2,3-二羟丙基)嘧啶的合成及其高碘酸盐氧化

近十年来,呋喃和嘧啶的并合体系之一的呋喃并[2,3-d]嘧啶的合成受到了一定的注意.对其衍生物的肌肉松弛、利尿、抗敏、镇静等作用及抗癌作用曾进行了研究.两个主要的合成途径是由取代4-羟基嘧啶与a-卤代羰基化合物缩合,或从2-氨基呋喃-3-甲腈或酮与胺或甲酰胺环化.     

Synthesis and antimicrobial activity of some novel 5-alkyl-6-substituted uracils and related derivatives

6-chloro-5-ethyl-, n-propyl- and isopropyluracils 5a-c were efficiently prepared from the corresponding 5-alkybarbituric acids 3a-c via treatment with phosphorus oxychloride and N,N-dimethylaniline to yield the corresponding 5-alkyl-2,4,6-trichloro-pyrimidines 4a-c, which were selectively hydrolyzed by heating in 10% aqueous sodium hydroxide for 30 minutes. The reaction of compounds 5a-c with 1-substituted piperazines yielded the corresponding 5-alkyl-6-(4-substituted-1-piperazinyl)uracils 6a-j. The target 8-alkyltetrazolo[1,5-f]pyrimidine-5,7(3H,6H)-diones 7a-c were prepared via the reaction of 5a-c with sodium azide. Compounds 6a-j and 7a-c were tested for in vitro activities against a panel of Gram-positive and Gram-negative bacteria and the yeast-like pathogenic fungus Candida albicans. Compound 6h displayed potent broad-spectrum antibacterial activity, while compound 6b showed moderate activity against the Gram-positive bacteria. All the tested compounds were practically inactive against Candida albicans.     

Synthesis of polymeric ionic liquid microsphere/Pt nanoparticle hybrids for electrocatalytic oxidation of methanol and catalytic oxidation of benzyl alcohol

Herein, we present a facile approach for the synthesis of polymeric ionic liquids (PILs) microspheres for metal scavenging and catalysis. Crosslinked poly(1‐butyl‐3‐vinylimidazolium bromide) microspheres with the diameter of about 200 nm were synthesized via miniemulsion polymerization, in which 1,4‐di(vinylimidazolium) butane bisbromide was added as the crosslinker. Anion exchange of PIL microspheres with Pt precursor and followed by the reduction of Pt ions produced PIL microsphere supported Pt nanoparticle hybrids. The synthesized Pt nanoparticles with a diameter of about 2 nm are uniformly dispersed and strongly bound to the surface of PIL microspheres. The catalytic performances of PIL/Pt nanoparticle hybrids were evaluated for both the electrocatalytic oxidation of methanol and oxidation of benzyl alcohol. The PIL/Pt nanoparticle hybrids show better electrocatalytic activity towards the electrooxidation of methanol than pure Pt nanoparticles. Furthermore, they are effective and easily reusable catalysts for the selective oxidation of benzyl alcohol in aqueous reaction media, demonstrating that the synthesized PIL microspheres are suitable scaffolds for heterogeneous catalysts Pt. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Biocatalytic oxidation of benzyl alcohol to benzaldehyde via hydrogen transfer

Various types of biocatalysts like oxidases, alcohol dehydrogenases, and microbial cells were tested for the oxidation of benzyl alcohol. Oxidases in combination with molecular oxygen led to low conversion. Alcohol dehydrogenases and microbial cells were tested in a hydrogen transfer reaction employing acetaldehyde, chloroacetone, and acetone as hydrogen acceptor. Excellent conversion (95%) could be achieved employing lyophilised cells of Janibacter terrae DSM 13953 at a substrate concentration of 97 mM.     

Solvent-free selective photocatalytic oxidation of benzyl alcohol to benzaldehyde by molecular oxygen using 9-phenyl-10-methylacridinium

9-Phenyl-10-methylacridium ion acts as an effective photocatalyst for solvent free selective photocatalytic oxidation of benzyl alcohol to benzaldehyde under visible light irradiation via efficient photoinduced electron transfer from benzyl alcohol to the singlet excited state of the acridinium ion.     

Synthesis and properties of 2-alkyl-5-ethynyltetrazoles

2-Alkyl-5-ethynyltetrazoles were synthesized. It is shown that ethynyltetrazoles have a triple bond with increased electrophilicity. They readily add aliphatic alcohols and amines and undergo aminomethylation, the Iotsich reaction, oxidative dimerization, and the cycloaddition of azides. 1-Phenyl-3-tetrazolyl-2-propyne, which has the properties of α-acetylenic ketones, was obtained by selective oxidation of tetrazolylethynylcarbinol. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 842–847, June, 1980.     

Discrimination of active palladium sites in catalytic liquid-phase oxidation of benzyl alcohol

Knowledge of the structure of active sites is a prerequisite for the rational design of solid catalysts. Using site-selective blocking by CO and isotope labeling combined with in situ attenuated total reflection infrared (ATR-IR) spectroscopy, we were able to discriminate the different sites involved in the liquid-phase oxidation of benzyl alcohol on Pd/Al(2)O(3). The main reaction, that is, the oxidative dehydrogenation of the alcohol to the corresponding aldehyde, showed only little dependence on structure and occurred on all exposed Pd faces, whereas the undesired product decarbonylation occurred preferentially on hollow sites on (111) Pd faces. This explains why specific blocking of the latter sites, as realized in the industrially used Pd-Bi/Al(2)O(3) catalysts, leads to improved catalytic performance.