A new synthetic route to substituted 1-fluoro-1-cyclopropanecarboxylates

Substituted 6-fluoro-2,4-dioxo-3-azabicyclo[3.1.0]hexane-6-carboxylates were obtained as a mixture of the exo- and endo-isomers by reaction of substituted 6,8-dioxo-2,3,7-triazabicyclo[3.3.0]oct-3-en-4-carboxylates with N-fluoropyridinium tetrafluoroborate.     

单壁碳纳米管与卤代烷的亲电加成反应

主要考察了以路易斯酸为催化剂,几种卤代烷烃为反应试剂的单壁碳纳米管侧壁的亲电加成反应,并通过傅立叶红外光谱、热失重分析和拉曼光谱验证了实验所得产物。此反应的目的是在单壁碳纳米管的侧壁连上烷基基团以提高其溶解性和分散性,并可使其更好地与聚烯烃相结合从而提高复合材料的性能,因而具有较高的研究和应用价值。     

First electrophilic substitution of 4-methoxyindole with triethyl orthoformate as an a1-synthon

Summary 4-Methoxyindole (2) reacts with triethyl orthoformate (1a) under proton catalysis to yield the functionalized indoles3a–3e in dependence on the reaction conditions. The attack of the electrophile takes place regiospecifically at the 3-position of the indole2

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Erste elektrophile Substitution von 4-Methoxyindol mit Orthoameisensäuretriethylester als a¹-Synthon (Kurze Mitt.)

Zusammenfassung In Abhängigkeit von den Reaktionsbedingungen reagiert 4-Methoxyindol (2) mit Orthoameisensäuretriethylester (1a) zu funktionalisierten Indolderivaten3a–3e. Der Angriff des Elektrophils erfolgt regiospezifisch an der 3-Position von2.

     

Conversion of Alcohols to Bromides by Trimethylsilane and lithium Bromide in Acetone

Conversion of alcohols to alkyl bromides is one of the most frequently used functional group transformation reactions. Phosphorus tribromide is one of the most popular classical reagents. Triphenylphosphine has been used in combination with bromine,carbon tetrabromide,N-halo imides and other bromide compounds as a mild reagents for the preparation of alkyl bromides. More reacently, halotrimethylsilanes were found to be useful for halogenation of alcohols. Geo- rge A.Olah successfully convert…     

Pictet Spengler-type reactions in 3-arylmethylpiperazine-2,5-diones. Synthesis of pyrazinotetrahydroisoquinolines

The behavior of aldehydes and acetals as N-alkylating agents of 1-acetyl-3-arylmethylpiperazine-2,5-diones and the subsequent cyclization of the N-alkylated products was studied. Use of paraformaldehyde in different reaction conditions gave 6-unsubstituted 3,6,11,11a-tetrahydro-2H-pyrazino[1,2-b]isoquinoline-1,4-diones and, in some cases, benzo[f]pyrazino[1,2-c]1,3-oxazepine-1,4-diones. Succesful reactions with benzaldehyde required a first activation of the lactam function and a catalyzed N-alkylation with the aldehyde dimethyl acetal. The isolated O,N-amidoacetals thus obtained were submitted to a diastereoselective Pictet Spengler-type reaction that worked with arenes at several degrees of ring activation and with thiophene to give 6-phenylpyrazinoisoquinolinediones and the corresponding thieno analog.     

Synthesis and properties of 1-bromo-2,3,5,6-tetrakis(3-pentyl)benzene: a highly sterically hindered aryl bromide

The preparation of 1-bromo-2,3,5,6-tetrakis(3-pentyl)benzene is reported. The ¹H and ¹³C NMR spectra indicate the presence of rotational isomers at room temperature which interconvert on heating. Coalescence of the NMR peaks for the methine and methylene aliphatic protons is observed at 100–120 °C. The conversion of this aryl bromide to the corresponding aryllithium is reported. Similar but less bulky aryl bromides have also been synthesised.     

Synthesis of 20-iodochlorophyll derivatives and their properties including reactivity,electronic absorption,and self-aggregation

Methyl 20-iodopyropheophorbides-a possessing several substituents at the 3-position were prepared by treatment of the corresponding 20-unsubstituted chlorophyll-a derivatives with iodine and [bis(trifluoroacetoxy)iodo]benzene in chloroform and water at room temperature. The sterically demanding 20-iodination was clean, efficient, and regioselective without alteration of the 3-substituents, and also highly reproducible. The resulting 20-iodides were so reactive that they were readily transformed into 20-acetylchlorin (Pd-catalyzed cross-coupling) and 20-unsubstituted chlorin (acidic deiodination). Electronic absorption spectra in dichloromethane showed that the 20-iodination shifted the maxima to longer wavelengths in their monomeric states. Zinc complexes of 3¹-hydroxy-20-iodo-13¹-oxochlorins self-aggregated in non-polar organic solvents to give red-shifted and broadened absorption bands, similarly as in the corresponding 20-unsubstituted molecules, which are good models of the main light-harvesting antenna systems in photosynthetic green bacteria.     

Improved,Highly Efficient,and Green Synthesis of Bromofluorenones and Nitrofluorenones in Water

A series of bromo-, nitro-, and bromonitrofluorenones were synthesized chemo- and regioselectively in 90–98% yield via electrophilic aromatic bromination and nitration under mild conditions using water as the sole solvent. These synthetic methods involve simple workup procedures and use only minimal amounts of organic solvents during the purification of products. The newly developed methods have the advantages of being cost-effective and environmentally friendly and could potentially be used for the large-scale synthesis of fluorenone derivatives.     

Citric Acid‐catalyzed Synthesis of 2,4‐Disubstituted Thiazoles from Ketones via C–Br,C–S,and C–N Bond Formations in One Pot: A Green Approach

An improved and greener protocol has been developed for the synthesis of 2,4‐disubstituted thiazoles via C–Br, C–S, and, C–N bond formations in a single step from readily available ketones, N‐bromosuccinimide (NBS), and thiourea catalyzed by citric acid in a mixture of ethanol and water (3:1) under reflux conditions. This method has the advantages of freedom from the isolation of lachrymatory α‐bromoketones, ease of carrying out, cleaner reaction profile, broad substrate scope, freedom from chromatographic purification, and suitability for large‐scale synthesis.