Facile and efficient synthesis of 4-azidotetrafluoroaniline: a new photoaffinity reagent

p-Azidotetrafluoroaniline (1) was synthesized in 65-73% yield by two different methods employing a stable carbamate intermediate. The first method trapped the intermediate isocyanate generated via a modified Curtius rearrangement with 2-methyl-2-propanol or 2-(trimethylsilyl)ethanol to form the stable carbamates 2d and 2e, respectively. Benzoic acid 2c was first converted to its acid chloride with PCl(5). Displacement of the chloride by NaN(3) in acetone/water formed the acyl azide. Thermal rearrangement followed by the addition of the appropriate alcohols provided the carbamates. The acid labile carbamate 2d was deprotected with HCl/AcOH to provide 1, while trifluoroacetic acid was required to deprotect 2e and afford 1. In the second path, 1 was synthesized in five steps from pentafluoronitrobenzene (3a) in 65% overall yield. Compound 3a was converted into 4-azidotetrafluoronitrobenzene (3b) with NaN(3) in 93% yield and was used without further purification to form 1, 4-diaminotetrafluorobenzene (3c) by Sn/HCl reduction in 85% yield. The mono-9-fluorenylmethoxycarbonyl (FMOC) derivative 3d was formed from 3c with FMOC-Cl and pyridine in EtOAc in 92% yield. Diazotization of 3d under anhydrous conditions with TFA/NaNO(2) and NaN(3) gave 3e in 87% yield. The aryl azide was formed with concurrent nitration of the 2-position of the fluorenyl system. The protecting group was removed with piperidine to afford 1 in 93% yield. Irradiation of 1 with 254 nm light in cyclohexane gave cyclohexylamine 11, diamine 3c, and azobenzene 12 as the primary products. The formation of C-H insertion product 11 indicates that 1 forms a singlet nitrene upon photolysis. Two heterobifunctional photoaffinity reagents iodoacetamide 9 and dansyl derivative 10 were prepared.     

Zinc(0)/dimethylformamide-mediated synthesis of symmetrical carboxylic anhydrides from acid chlorides

The high yielding synthesis of symmetrical carboxylic anhydrides from acid chlorides mediated by zinc dust in the presence of dimethylformamide is presented. A mechanism involving the reductive insertion of zinc(0) into the C-Cl bond of a Vilsmeier-type iminium intermediate as the crucial step is also proposed.     

An efficient synthesis of polymer-supported silyl linkers using a di-Grignard reagent

Various trialkylsilyl linked polymer supports have been prepared by reacting benzyl chloride resin and a di-Grignard reagent with CuBr·Me₂S, followed by dialkylchlorosilanes. 4-Alkoxybenzyl type resin, Wang-Cl 2c and Argogel Wang-Cl 2d provided 4c and 4d at ambient temperature, whereas nonactivated resin, Merrifield 2a and Argogel-Cl 2b afforded 4a and 4b at 60 °C. Primary and secondary alcohols 6-10 were attached to the alkyldiisopropyl-linked Wang type resin 4cA by a novel dehydrosilation with B(C₆F₅)₃ as well as by conventional methods.     

Novel annulation reactions : the direct synthesis of cyclopentanes using a lewis acid activated bisfunctional annulating reagent

In a novel one-pot reaction 3,3-Dimethoxy-1-trimethylstannyl-propane (1) reacts in the presence of Lewis acids with O-silytated enolates in a [3+2] annulation to form fused cyclopentanes possessing a bridgehead hydroxy group.     

Stability of photocurable anhydrides: Methacrylic acid mixed anhydrides of nontoxic diacids

Disproportionation of the liquid mixed anhydride dimethacrylic sebacic anhydride (m‐SA) to methacrylic anhydride and polyanhydride oligomers, as well as vinylic polymerization, can occur on workup and storage at room temperature. Dimethacrylic 1,3‐bis(p‐carboxyphenoxy) propane, being a solid, can also disproportionate, but the propensity to do so is lower than for m‐SA. These events can be suppressed with free‐radical inhibitors, and the inhibitor 2+3‐t‐butyl‐4‐methoxyphenol is a more effective stabilizer than 4‐methoxyphenol at 20 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4189–4195, 2001     

Facile synthesis of acyl sulfonamides from carboxyic acids using the Mukaiyama reagent

A fast and convenient method using the Mukaiyama reagent was developed to prepare acyl sulfonamides from carboxylic acids and sulfonamides. This methodology is effective for a range of acids and sulfonamides proceeding in moderate to good yields with the majority of reactions complete within one hour under the optimized condition.     

The efficient synthesis of morphinandienone alkaloids by using a combination of hypervalent iodine(III) reagent and heteropoly acid

The non-phenolic coupling reaction of benzyltetrahydroisoquinolines (laudanosine derivatives) by using a hypervalent iodine(III) reagent is described. In general, chemical oxidation of laudanosine gives glaucine. In contrast to general chemical oxidizing reagent systems, the novel use of reagent combination of phenyliodine bis(trifluoroacetate) (PIFA), and heteropoly acid (HPA) afforded morphinandienone alkaloids in excellent yields. In order to achieve the coupling reaction with simple reaction procedure, the use of HPA supported on silica gel instead of HPA was demonstrated and sufficient yield was exerted again. The present reagent system, PIFA/HPA, was also applied to the oxidation of other non-phenolic benzyltetrahydroisoquinolines and the high yield conversion to morphinandienones was accomplished.     

A mild, clean, and simple synthesis of symmetrical carboxylic anhydrides from carboxylic acides using a polymer supported tosyl chloride

The use of polymeric reagents simplifies routine acylation of carboxylic acid because it eliminates the traditional purification. We describe the use of readily available cross-linked poly(4-vinylpyridine) supported tosyl chloride, [P₄VP].TsCl, in the suspended solution phase synthesis of symmetrical anhydrides from carboxylic acids in the presence of K₂CO₃ in high yields and purity. The products can be obtained by filtration and evaporation of the solvent.     

A new synthesis of carboxylic and carbonic acid anhydrides using phase transfer reactions

Acyl chlorides and alkylchloroformates smoothly reacted with one molar equivalent of sodium hydxoxide, using liquid-liquid phase transfer conditions to afford high yields of the corresponding symmtrical carboxylic and carbonic hemiester anhydrides. Unstable, anhydrides such as 4-nitrobenzoïc, 2-furoïc and methacrylic anhydrides, which are otherwise difficult to obtain, were easily prepared by this method. The reaction mechanism does not seem to involve intermediate hydrolysis of half the acid chloride into the corresponding sodium carboxylate.     

Activation of a carboxy group by dialkyl pyrocarbonates. Synthesis of symmetrical anhydrides and aryl esters of N-protected amino acids using di-tert-butyl pyrocarbonate as condensing reagent

It has been shown that di-tert-butyl pyrocarbonate can be used as a condensing reagent in the production of anhydrides and some aryl esters of carboxylic acids. The synthesis of anhydrides and of phenyl, p-nitrophenyl, -naphthyl, and quinolin-8-yl esters of N-protected amino acids is described.Institute of Biological and Medicinal Chemistry, Academy of Medical Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 357–362, May–June, 1984.     

Facile and efficient total synthesis of (+)-preussin

[structure] The enantioselective total synthesis of (+)-preussin, a potent antifungal agent, has been achieved. The key steps are a Pd(0)-catalyzed oxazoline-forming reaction from L-phenylalanine, hydrogenolysis, and subsequent diastereoselective reductive cyclization of the intermediate aminoketone to pyrrolidine using Pearlman's catalyst.     

A novel and direct synthesis of chroman derivatives using a hypervalent iodine(III) reagent

The direct aromatic carbon-oxygen bond-formation reaction was described and the novel and simple synthetic method for chroman derivatives involving aromatic cation radical intermediates was developed using the hypervalent iodine(III) reagent, phenyliodine(III) bis(trifluoroacetate) (PIFA).     

2-Diazoacetoacetic acid, an efficient and convenient reagent for the synthesis of alpha-diazo-beta-ketoesters

The formation of various alpha-diazo acetoacetic esters can be obtained in a single transformation with good to excellent yields using readily available 2-diazoacetoacetic acid.     

Facile and efficient synthesis of star-shaped oligomers from a triazine core

A facile and efficient synthetic approach to tripodal star-shaped oligomers is described. Several generations of hydroxyl-terminated tripodal star-shaped oligomers were prepared in high yield from 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAT) as a core by alternating amine-catalyzed thiol-ene and acrylate esterification reactions. The compounds were fully characterized by 1D and 2D NMR spectroscopy, ESI-MS, and elemental analysis. The combination of thioether groups and hydrogen bonding moieties suggests that these products can be used as metal chelating ligands.     

One-pot electrochemical synthesis of acid anhydrides from alcohols

Russian Journal of General Chemistry - One-pot indirect electrochemical oxidation of alcohols in the methylene chloride–aqueous solution of sodium hydrocarbonate two-phase system in the...     

Synthesis of mixed acid anhydrides from methane and carbon dioxide in acid solvents

[reaction: see text] The reaction of CH(4) with CO(2) has been performed in anhydrous acids using VO(acac)(2) and K(2)S(2)O(8) as promoters. NMR analysis establishes that the primary product is a mixed anhydride of acetic acid and the acid solvent. In sulfuric acid, the overall reaction is CH(4) + CO(2) + SO(3) --> CH(3)C(O)-O-SO(3)H. Hydrolysis of the mixed anhydride produces acetic acid and the solvent acid. When trifluoroacetic acid is the solvent, acetic acid is primarily formed via the reaction CH(4) + CF(3)COOH --> CH(3)COOH + CHF(3).     

白花丹酸的简易合成法

设计了以邻苯二酚为起始原料的新合成路线, 在不同保护基的条件下用二条合成路线合成了白花丹酸, 方法的特点是以杂原子诱导的芳基锂化反应实现了区域专一性芳酰化; 用KH为碱顺利实现了羰基α位的羧甲基化; 采用环己酮保护酚羟基后, 后处理方便, 收率提高。     

Discovery of powerful uranyl ligands from efficient synthesis and screening

New tripodal gem-(bis-phosphonates) uranophiles were discovered by a screening method that allowed for the selection of ligands with strong uranyl-binding properties in a convenient microtiter-plate format. The method is based on competitive uranium binding by using Sulfochlorophenol S as chromogenic chelate. This dye compound was found to present high uranyl complexation properties and allowed to highlight ligands presenting association constants for UO(2+)(2) up to 10(18) at pH 7.4 and 10(20) at pH 9. A collection of 40 known ligands including polycarboxylate, hydroxamate, catecholate, hydroxypyridonate and hydroxyquinoline derivatives was tested. Also screened was a combinatorial library prepared from seven amine scaffolds and eight acrylates bearing diverse chelating moieties. Among these 96 tested candidates, a tripod derivative bearing gem-bis-phosphonates moieties was found to present the highest complexation properties over a wide range of pH and was further studied.