Sur l'orientation et les anomalies de l'acetylation des Bz-méthoxy nitro-2 benzofurannes

4-Methoxy-, 5-methoxy- and 7-methoxy-2-nitrobenzofurans have been acetylated via the Friedel-Crafts reaction under the same reaction conditions. 2-Nitrobenzofuran does not undergo acetylation while 6-methoxy-2-nitrobenzofuran only produces decomposition products. As a result of the positive acetylation reactions, 7-acetyl-4-methoxy-, 4-acetyl-5-methoxy- and 4-acetyl-7-methoxy-2-nitrobenzofuran have been prepared. As side products in the acetylation reactions, 4-methoxy-3-(4′-methoxy-2′-nitro-7′-benzofuranyl)-2,3-dihydrobenzofuran-2-one was isolated when 4-methoxy-2-nitrobenzofuran was the starting material and, likewise, when 5-methoxy-2-nitrobenzofuran was the starting material, 3-chloro-5-methoxy-2,3-dihydrobenzofuran-2-one was obtained. Furthermore, 5-methoxy-2-nitrobenzofuran participated in an unexpected chlorination leading to 4-chloro-5-methoxy-2-nitrobenzofuran.     

Total syntheses of beta-carboline alkaloids, (R)-(-)-pyridindolol K1, (R)-(-)-pyridindolol K2, and (R)-(-)-pyridindolol.

The total syntheses of beta-carboline alkaloids, (R)-(-)-pyridindolols (1, 5, and 6) are described. The two key steps involved are (1) a thermal electrocyclic reaction of the 3-alkenylindole-2-aldoxime 10 and (2) a thermal cyclization of 3-alkynylindole-2-aldoxime 11 to construct the beta-carboline N-oxides 8, which upon heating with acetic anhydride and sequential treatment with trifluoromethanesulfonic anhydride gave the triflates 18. The Stille coupling reaction of 18 with vinylstannane, followed by cleavage of MOM ether, afforded the 1-ethenyl-3-hydroxymethyl-beta-carboline (7a). Subsequent acetylation of 7a yielded the acetate 7b, which was subjected to the Sharpless asymmetric 1,2-dihydroxylation by AD-mix-beta to produce (R)-(-)-pyridindolol K2 (6). Selective acetylation of 6 was effected by Ac(2)O and collidine to form (R)-(-)-pyridindolol K1 (5). By contrast, hydrolysis of 6 provided (R)-(-)-pyridindolol (1).     

Infrared and 13C MAS nuclear magnetic resonance spectroscopic study of acetylation of cotton

The acetylation of commercial cotton samples with acetic anhydride without solvents in the presence of about 5% 4-dimethylaminopyridine (DMAP) catalyst was followed using Fourier transform infrared (FTIR) and 13C MAS NMR spectroscopy. This preliminary investigation was conducted in an effort to develop hydrophobic, biodegradable, cellulosic materials for subsequent application in oil spill cleanup. The FTIR results provide clear evidence for successful acetylation though the NMR results indicate that the level of acetylation is low. Nevertheless, the overall results indicate that cotton fibres are potential candidates suitable for further development via acetylation into hydrophobic sorbent materials for subsequent oil spill cleanup application. The results also indicate that de-acetylation, the reverse of the equilibrium acetylation reaction, occurred when the acetylation reaction was prolonged beyond 3 h.     

Syntheses of 7-fluoro- and 6,7-difluoroserotonin and 7-fluoro- and 6,7-difluoromelatonin

The Abramovitch adaption of the Fischer indole synthesis gave low yields of 7-fluoro-5-methoxytryptamine due in part to decomposition during the required decarboxylation step. Therefore, 7-fluoro- and 6,7-difluoro-5-methoxytryptamines were prepared by reaction of aminobutyraldehyde (generated in situ from the diethyl acetal) with 2-fluoro- and 2,3-difluoro-4-methoxyphenylhydrazine, and the products converted to the corresponding serotonins. The melatonins were prepared by a one-pot reaction that involved in situ acetylation of the aminobutyraldehyde.     

Resolution of an iridoid synthon, gastrolactol, by means of dynamic acetylation and lipase-catalyzed alcoholysis

A short synthetic route to asymmetric iridoids was developed. The three key steps were an intramolecular [4 + 2] cycloaddition reaction of an enamine derivative of 8-oxocitral (2), a dynamic acetylation, and an enzymatic resolution of the gastrolactyl acetates 5a and 5b, iridoids with three stereocenters. Some regio- and stereoselective heterogeneous catalytic hydrogenations of double bonds in iridoid aglucones were discussed.     

Selective acetylation of toluene to 4-methylacetophenone over zeolite catalysts

The vapour phase acetylation of toluene has been catalysed by acidic H-ZSM-5, H-mordenite and REY zeolite catalysts at 453 K in a tubular reactor at atmospheric pressure. H-ZSM-5 exhibited the best results during the reaction with respect to rate of acetylchloride conversion (TOF=7.5 mol s⁻¹ mol⁻¹ Al×10⁻⁴), conversion of acetyl chloride (60.2 wt.%) and selectivity for 4-methylacetophenone (88.3%) compared to both H-mordenite and REY zeolites. It is revealed that the activity and selectivity of the catalyst strongly depend on the acidic properties and pore openings of the zeolites, respectively. It is observed that isomer ratio (4-methylacetophenone/2-methylacetophenone) is influenced by the reaction conditions and type of zeolite used in the reaction. With increasing reaction temperature and toluene to CH₃COCl molar ratio, the conversion of CH₃COCl (ACT) increases, while it decreases with the increase in reaction time, weight hourly space velocity (WHSV), Na-content and silica to alumina molar ratio of H-ZSM-5 in the acetylation of toluene. H-ZSM-5 is deactivated under the reaction conditions.     

Studies on the homogeneous acetylation of cellulose in the novel solvent dimethyl sulfoxide/tetrabutylammonium fluoride trihydrate

The novel solvent dimethyl sulfoxide (DMSO)/tetrabutylammonium fluoride trihydrate (TBAF . 3H(2)O) was studied for acetylation of linters cellulose. In order to control the degree of substitution (DS), acetylation of the macromolecule was carried out at different reaction time and temperature, molar ratio of reactants, as well as under variation of the concentration of TBAF . 3H(2)O in solution. Cellulose acetate (CA) was accessible with DS ranging from 0.43 to 2.77. The change in concentration of TBAF . 3H(2)O in DMSO showed a strong influence on DS. The most appropriate reaction conditions for acetylation of linters cellulose regarding maximal DS were evaluated. The structure of the CA was characterized by means of FTIR and NMR spectroscopy. The solubility of the CA depends not only on the DS but also on the reaction conditions applied, indicating a different distribution of acetate moieties both within and between polymer chains.     

Synthesis of [1,5-A]Pyrimidinone Ring Derivatives

Cyclodehydrogenation of the benzalhydrazino derivatives 5 and 6 gave 6-cyano-7-(4-methoxyphenyl)- 2-phenyl-5-oxo-1,2,4-triazolo[1,5-a]pyrimidine (8) and 6-cyano-7-(4-methoxyphenyl)-4-methyl-2-phenyl- 5-oxo-1,2,4-triazolo[1,5-a]pyrimidine (9) respectively. Melhylation, acetylation and benzylation of 8 gave the corresponding N-methyl, acetyl and benzyl derivatives 10-12 . Methylation of 5 with dimethylsulfate gave 2-benzalhydrazino-5-cyano-3-methyl-6-(4-methoxyphenyl)-3,4-dihydropyrimidin-4-one (6) , of which the reaction with acetic anhydride in pyridine afforded the N-acetylbenzalhydrazino derivative 15 . The latter was also prepared from acetylation of 5 followed by medthylation with iodomethane. Acetylation of 5 with boiling acetic anhydride afforded the diacetyl derivative 16 , whereas its benzylation gave the mono-N-benzyl derivative 14 .     

Synthesis, structure and properties of N-acetylated derivatives of methyl 5-amino-1H-[1,2,4]triazole-3-carboxylate

Methyl 5-amino-1H-[1,2,4]triazole-3-carboxylate hydrochloride (1). and free ester (2). were obtained and 2 was reacted with Ac(2)O to give the acetylated products 3-6. Compounds 1-6 were studied using HPLC, GC-MS, FTIR and multinuclear NMR spectroscopy, including the cross-polarisation magic angle spinning (CPMAS) technique. The results of the acetylation of 2 were compared to those of the acetylation of 5-amino-1H-[1,2,4]triazole, and for 2 a significant decrease in the susceptibility to acetylation was found. The reaction of 2 with Ac(2)O at 20 degrees C, regardless of the amount and the concentration of the latter, including neat Ac(2)O, proceeds fully regioselectively and leads to one product: methyl 1-acetyl-5-amino-1H-[1,2,4]triazole-3-carboxylate (3). In sharp contrast to 5-amino-1H-[1,2,4]triazole, neither an additional monoacetylated isomer, whether annular or exocyclic, nor any diacetylated derivative could be detected. The diacetylation of 2 requires the process to be carried out in neat boiling Ac(2)O and, as in the case of 5-amino-1H-[1,2,4]triazole, gives two diacetylated isomers. These are methyl 1-acetyl-3-(acetylamino)-1H-[1,2,4]triazole-5-carboxylate (4) and 1-acetyl-5-(acetylamino)-1H-[1,2,4]triazole-3-carboxylate (5). Hypothetical pathways of their formation have been suggested. A mixture of 4 and 5 upon hydrolysis of the ring acetyl group gives the monoacetylated derivative methyl 5-(acetylamino)-1H-[1,2,4]triazole-3-carboxylate (6). The spectroscopic, structural and conformational characteristics of compounds 1-6 have been given and methods for their preparation have been provided.     

Synthesis of 5H‐1,2,3‐triazolo[4,3‐a][2]benzazepines from the baylis‐hillman adducts of 2‐alkynylbenzaldehydes

The facile synthesis of 5H‐1,2,3‐triazolo[4,3‐a][2]benzazepines 5a‐d by the intramolecular 1,3‐dipolar cycloaddition reaction of 2‐alkynylphenylallyl azides 4a‐d is described. The latter were readily obtained from 2‐alkynylbenzaldehydes 1a‐d through the Baylis‐Hillman adducts 2a‐d followed by acetylation to compounds 3a‐d and nucleophilic substitution by azide to compounds 4a‐d.     

Synthesis of 3-arylpiperidines by a radical 1,4-aryl migration

[reaction: see text] A route to 3-arylpiperidines, 3-arylpyridines, and 5-arylpiperidin-2-ones involving a radical 1,4-aryl migration has been explored. The sequence requires a xanthate addition to an N-allylarylsulfonamide, followed by acetylation and treatment with dilauroyl peroxide to give the 1,4-aryl transfer product, which upon acidic hydrolysis affords the desired piperidine derivative.     

Synthesis of 2'-C-beta-fluoromethyluridine

[reaction: see text] 2'-C-beta-Fluoromethyluridine (17) represents both a potentially important biological agent and a tool for biochemical analysis. Here we describe the first synthesis of this compound starting from uridine. The key steps include protection of the uracil base with methoxyethoxymethyl (MEM) chloride, conversion to the corresponding 2'-C-alpha-epoxide, and regioselective opening of the oxirane ring with potassium fluoride/hydrogen fluoride. Subsequent acetylation of the 3'- and 5'-hydroxyl groups enables MEM removal using B-bromocatecholborane. Deacetylation generates the parent nucleoside, 2'-C-beta-flurormethyluridine.     

4'-(丹磺酰氨基)苯并冠醚和4'-[α-(丹磺酰氨基)乙基]苯并-15-冠-5的合成

从B12C4, B15C5和B18C6经过硝化、催化氢化和丹磺酰化合成了三种4'-(丹磺酰氨基)苯并冠醚, 从B15C5径乙酰化, Leuckart反应和丹磺酰化合成了另一个4'-[α-(丹磺酰氨)乙基]苯并-15-冠-5这些丹磺酰氨衍生物均为新荧光冠醚.     

A bacterial acetyltransferase capable of regioselective N-acetylation of antibiotics and histones

The Salmonella enterica chromosomally encoded AAC(6')-Iy has been shown to confer broad aminoglycoside resistance in strains in which the structural gene is expressed. The three-dimensional structures reported place the enzyme in the large Gcn5-related N-acetyltransferase (GNAT) superfamily. The structure of the CoA-ribostamycin ternary complex allows us to propose a chemical mechanism for the reaction, and comparison with the Mycobacterium tuberculosis AAC(2')-CoA-ribostamycin complex allows us to define how regioselectivity of acetylation is achieved. The AAC(6')-Iy dimer is most structurally similar to the Saccharomyces cerevisiae Hpa2-encoded histone acetyltransferase. We demonstrate that AAC(6')-Iy catalyzes both acetyl-CoA-dependent self-alpha-N-acetylation and acetylation of eukaryotic histone proteins and the human histone H3 N-terminal peptide. These structural and catalytic similarities lead us to propose that chromosomally encoded bacterial acetyltransferases, including those functionally identified as aminoglycoside acetyltransferases, are the evolutionary progenitors of the eukaryotic histone acetyltransferases.     

Preparation and properties of phenyl-substituted cyclopentadienylides

Phenyl-substituted cyclopentadienylides have been prepared, for the most part by carbenic decomposition of diazocyclopentadienes copper-bronze was an effective catalyst and also enabled reaction to be carried out in solution 2,5-Diphenyldiazocyclopentadiene gave triphenylarsonium 2,4-diphenylcyclopentadienylide instead of the expected product. Electrophilic substitution (acetylation, formylation, diazo-coupling) proceeds preferentially at the 2(5)-positions, but if these sites are blocked, may take place at the 3(4)-positions. The spectra of 3(4)-acyl- and 3(4)-phenylazo-derivatives differ markedly from those of their 2(5)-analogues. Unlike their 2(5)-acyl-analogues, triphenylarsonium 3(4)-acyl-derivatives are unstable to hydrolysis.     

One‐Pot Synthesis of 3‐Acetyl‐2‐aryl‐3,4‐dihydroquinazolines from N‐[2‐(Azidomethyl)phenyl]benzamides Utilizing Intramolecular Aza‐Wittig Reaction

A new and convenient method for the preparation of 3,4‐dihydroquinazolines 5 with aryl and Ac groups at C(2) and N(3), respectively, has been developed. The key sequence is the formation of aza‐phosphorane intermediates by the reaction of N‐[2‐(azidomethyl)phenyl]benzamides 1 with Ph₃P, followed by intramolecular aza‐Wittig reaction and 3‐acetylation, which can be conducted in one‐pot.     

An efficient synthesis of cholanic acids from 20-ketopregnanes

An efficient synthesis of 3β-hydroxy-5-cholanic acid (8) and 3β-hydroxy-Δ⁵-cholanic acid (16) was carried out starting from 5-dihydropregnenolene (1) and pregnenolone (9). The monoacetates (3 and 11), prepared by Grignard reaction of 1 and 9 with 3,3-ethylenedioxypropylmagnesium bromide followed by acetylation, were dehydrated selectively to give the Δ²⁰⁽²²⁾-compounds (4 and 12) which on hydrogenation followed by acid treatment and Jones oxidation yielded 8 and 16, respectively.     

Preparation of cis-5-methoxy-and-7-methoxy-1-acetoxy-1,2,3,4,4a,10a- hexahydro-9(10H)-phenanthrenone. An epoxide-arene reaction involving a selective 1,2-alkyl shift rearrangement.

The preparation of cis-1-acetoxy-7-methoxy-1,2,3,4,4a,10a-hexahydro-9(10H)- phenanthrenone 5 was accomplished starting from 6-methoxy-1-tetralone. Reduction of 7-methoxy-1,2,3, 4,9,10-hexahydro-1-oxo-phenanthrene 8, acetylation and subsequent oxidation delivered 5. Application of an analogus procedure to the preparation of cis-1β-acetoxy-5-methoxy-1,2,3,4,,4a,10a-hexahydro-9(10H)- phenanthrenone 6 was not feasible. A more elaborate route was developed for the synthesis of compound 6, where an epoxide-arene reaction involving a 1,2-alkyl shift rearrangement, constituted a highly selective key transformation.     

(5-氨基-[1,3,4]噻二唑-2-基)-丙酸乙酯的合成工艺改进

以丁二酸酐为起始原料,经醇解和酰化反应制得丁二酸单乙酯酰氯(3);3经甲烷磺酸催化与氨基硫脲环合合成了重要药物中间体——(5-氨基-[1,3,4]噻二唑-2-基)-丙酸乙酯,其结构经~1H NMR,IR和MS确证。运用正交试验对环合反应条件进行优化。最优反应条件为:3 132 mmol,n(氨基硫脲)∶n(3)∶n(甲烷磺酸)=1∶3∶3,于110℃反应3 h,总收率51.3%。     

负载型催化剂HPW/SBA-15的合成及其在2-萘甲醚乙酰化反应中的应用

采用浸渍法制备了SBA-15负载磷钨酸（HPW）催化剂HPW/SBA-15（Cat）,其结构和性能经XRD, IR和NH₃-TPD表征。将 Cat 应用于2-萘甲醚（1）和乙酸酐（2）的傅 克酰基化反应,考察了不同负载量的催化剂、反应时间、催化剂用量、原料摩尔比、反应温度对2-萘甲醚酰基化反应的转化率和主产物选择性的影响。结果表明:Cat₄₀ 0.05 g,反应5 h,n(1) ：n(2)=1：4,反应温度120 ℃时,1的转化率为92.59%,主产物2-甲氧基-1-萘乙酮的选择性达99.22%。