Studies on heteroaromaticity. XV . the 1,3-dipolar cycloaddition reaction of 5-nitro-2-furyldiazomethane

The 1,3-dipolar cycloaddition reaction of 5-nitro-2-furyldiazomethane ( 1 ) with acrylonitrile, acrylamide, methyl acrylate, diethyl fumarate, methyl methacrylate and methyl cinnamate afforded the corresponding 3-substituted pyrazolines. ( 2a-f ). Similarly the pyrazoles ( 3b-d ) were prepared by addition of 1 to acetylenic compounds such as diethyl acetylenedicarboxylate, methyl phenylpropiolate and cyanoacetylene. Reaction of 1 with fumaronitrile and ω-nitro-styrene gave also the corresponding pyrazoles ( 3a and 3e ) instead of the pyrazolines. 3-(5′-Nitro-2′-furyl)-4-phenyl-5-carbomethoxypyrazoline ( 2f ) was oxidized with lead tetraacetate to the corresponding pyrazole ( 3f ), which was different from 3c , an addition product of 1 with methyl phenylpropiolate. 3-(5′-Nitro-2′-furyl)-5-carbamidopyrazoline ( 2b ) was pyrolyzed to the corresponding cyclopropane derivative 4 in low yield.     

Synthesis and Properties of (1,3-Dioxolan-2-yl)furans

Reaction of formylfurancarboxylates with excess ethylene glycol in the presence of p-toluene-sulfonic acid gives rise to (1'3-dioxolan-2-yl)furancarboxylates. Reduction of these products with lithiumaluminum hydride proceeds with preservation of the dioxolane ring. Except for 5-(1'3-dioxolan-2-yl)(hydr-oxymethyl)-2-methyl-3-furan, the obtained alcohols are unstable. Chlorides derived from them decomposeunder conditions of the Michaelis-Becker reaction, no phosphorylation products are formed. By contrast'the above-mentioned stable alcohol by treatment with thionyl chloride in the presence of pyridine is convertedto a fairly stable chloromethylfuran. The latter compound reacts with sodium diethyl phosphite in benzene to form the corresponding phosphonate that exists as a 1:4 mixture of two spectroscopically discernible conformers.     

A STUDY ON THE TRANSESTERIFICATION REACTION OF DIMETHYL AND DIETHYL PHOSPHITE WITH 1,3-DICHLOROPROPANOL-2

Abstract

The transesterification process of dimethyl and diethyl phosphite with 1,3-dichloropropanol-2 is examined. It is found that the reaction proceeds in the absence of catalyst at a temperature of 155°, whereas in the presence of morpholine as a catalyst it takes place at 126°C. The transesterification of dimethyl phosphite and diethyl phosphite with 1,3-dichloropropanol-2 is accompanied by the evolution of dimethyl and diethyl ethers and alkyl halides (methyl chloride and ethyl chloride).     

Synthesis and Crystal Structure of Diethyl-2,6- dimethyl-3,5- diyl- （ 1- （2- chlorob enzoyl）- 1H- pyrazole-3-diethyl-carboxylate）-pyridine

The reaction of hydrazine hydrate with a new α,γ-diketone ester 3, derived from the reaction of 2,6-dimethyl-3,5-diacetyl-pyridine 2 with diethyl oxalate in the presence of sodium ethoxide, afforded the pyrazole derivative 4. Treatment of 4 with 2-chlorobenzoyl chloride gave diethyl 2,6-dimethyl-3,5-diyl-（1-2（chlorobenzoyl）-1H-pyrazole-3-diethyl-carboxylate） pyridine 5. Fine crystal of 5 suitable for XRD analysis was obtained form recrystalization in ethyl acetate. The crystal belongs to the triclinic system, space group P1^-, with a = 1.0342（11）, b = 1.2211（12）, c = 1.5013（15） nm, α = 82.5190（10）,β = 85.7960（10）,γ = 85.3150（10）°, V= 1.8697（3） nm^3, Dc= 1.173 g/cm^3, μ = 0.219 mm^-1, F（000） = 684, Z = 2, the final R = 0.0720 and wR = 0.2211.     

Efficient synthesis and anion recognition of a colorimetric preorganized tripodal thiourea compound

A preorganized colorimetric tripodal thiourea receptor was synthesized in high yield utilizing a thiol-ene reaction as a primary step. The interaction of the receptor with dihydrogen phosphate, acetate, chloride, and fluoride anions was investigated using UV–vis. and ¹H NMR spectroscopic titration techniques. The binding stoichiometry of the receptor with dihydrogen phosphate and acetate was found to be 1:2, and 1:1 with chloride and fluoride. The binding constants for the receptor and dihydrogen phosphate, acetate, chloride, and fluoride were determined using HypNMR2008 and HypSpec.     

Hexachloroacetone as a precursor for a tetrachloro-substituted oxyallyl intermediate: [4+3] cycloaddition to cyclic 1,3-dienes

The enol phosphate 2,2-dichloro-1-(trichloromethyl)ethenyl diethyl phosphate (1), easily available by a Perkow reaction between hexachloroacetone and triethyl phosphite, reacts with sodium trifluoroethoxide/trifluoroethanol in the presence of cyclic 5-membered 1,3-dienes to furnish alpha,alpha,alpha',alpha'-tetrachloro-substituted[3.2.1]bicyclic ketones 2. A [4+3] cycloaddition of a tetrachloro-oxyallyl intermediate is postulated.     

New, efficient synthesis of oseltamivir phosphate (Tamiflu) via enzymatic desymmetrization of a meso-1,3-cyclohexanedicarboxylic acid diester

A new, enantioselective synthesis of the influenza neuraminidase inhibitor prodrug oseltamivir phosphate 1 (Tamiflu) and its enantiomer ent-1 starting from cheap, commercially available 2,6-dimethoxyphenol 10 is described. The main features of this approach comprise the cis-hydrogenation of 5-(1-ethyl-propoxy)-4,6-dimethoxy-isophthalic acid diethyl ester (6a) and the desymmetrization of the resultant all-cis meso-diesters 7a and 7b, respectively. Enzymatic hydrolysis of the meso-diester 7b with pig liver esterase afforded the (S)-monoacid 8b, which was converted into cyclohexenol 17 via a Curtius degradation and a base-catalyzed decarboxylative elimination of the Boc-protected oxazolidinone 14. Introduction of the second amino function via S(N)2 substitution of the corresponding triflate 18 with NaN3 followed by azide reduction, N-acetylation, and Boc-deprotection gave oseltamivir phosphate 1 in a total of 10 steps and an overall yield of approximately 30%. The enantiomer ent-1 was similarly obtained via an enzymatic desymmetrization of meso-diester 7a with Aspergillus oryzae lipase, providing the (R)-monoacid ent-8a.     

REACTION OF PENTAERYTHRITOL WITH DIETHYL PHOSPHOROCHLORIDATE PENTAERYTHRITOL BIS-, TRIS- AND TETRAKIS(DIHYDROGEN PHOSPHATES)

Abstract

Reaction of pentaerythritol 1 with 1, 2 or 3 equivalents of diethyl phosphorochloridate 2 yielded pentaerythritol tris(diethyl phosphate) 5. Treatment of pentaerythritol with 4 or more equivalents of 2 gave pentaerythritol tetrakis(diethyl phosphate) 6. Transesterification of 5 and 6 with trimethylsilyl chloride and sodium iodide in acetonitrile followed by treatment with water gave pentaerythritol tris (dihydrogen phosphate) 7 and pentaerythritol tetrakis(dihydrogen phosphate) 8 respectively. Pentaerythritol bis(dihydrogen phosphate) 9 was prepared by the hydrolysis of 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro [5,5] undecane 3,9-dioxide 10. The compounds 7,8 and 9 were isolated as anilinium salts and characterized by 1H, 13C and 31P NMR spectra.     

2-(1-Chloroalkyl)furans in the reaction with sodium diethyl phosphite

2-(1-Chloroethyl) and 2-(1-chloro-2-methylpropyl)furans react with sodium diethyl phosphite to give two products, 2-(1-diethoxyphosphorylmethyl)furan and 2-alkyl-5-(diethoxyphosphoryloxy)furan. The fraction of the latter product increases with increasing size of the alkyl radical. 2-Methyl substitution in the substrate completely suppresses phosphate formation. 2-(1-Chloroethyl)-5-(2-methylpropyl)furan under the action of sodium diethyl phosphite eliminates hydrogen chloride to give the corresponding alkene.     

Anion sensing using colorimetric amidourea based receptors incorporated into a 1,3-disubstituted calix[4]arene

The synthesis of amidourea-based colorimetric anion sensors 1 and 2 and the evaluation of these sensors using anions such as acetate , fluoride (F⁻), hydrogen phosphate and hydrogenpyrophosphate (pyr) in DMSO is described. While 1 has a single amidourea moiety, 2 has two such receptors incorporated into a lower-rim 1,3-disubstituted calix[4]arene scaffold. Whilst both sensors gave rise to red shifts in their absorption spectra upon anion recognition, the sensing of F⁻ and pyr gave rise to large changes with concomitant colour changes from yellow to purple, which were visible to the naked eye.     

A new route to 7-substituted derivatives of n-[4-(2-[2-amino-3,4-dihydro-4-oxo-7H-pyrrolo(2,3-d)pyrimidin-5-yl]ethyl)benzoyl]-L-glutamic acid [ALIMTA (LY231514, MTA)

Alkylation of various primary amines with crotyl bromide, followed by DMAP-promoted acylation with methyl malonyl chloride to 4 and then manganic triacetate dihydrate/cupric acetate induced radical cyclization, gave 1-substituted-4-vinyl-3-carbomethoxy-2-pyrrolidinones (5). Thiation to the thiolactams 6 and guanidine cyclization then gave a series of 2-amino-3,4-dihydro-4-oxo-5-vinyl-7-substituted pyrrolo[2,3-d]pyrimidines (7). Palladium-catalyzed C-C coupling with diethyl 4-iodobenzoylglutamate led in one step via an unexpected redox reaction to the diethyl esters 9 of a series of 7-substituted derivatives of ALIMTA (LY231514, MTA), from which the target analogues 10 were readily prepared by saponification. Attempted deprotection at position 7 was successful in only one case (9d, R = CH(2)C(6)H(3)(OMe)(2)(-3',4'), which resulted in a known pentultimate precursor (9, R = H) of ALIMTA. The 7-substituted derivatives 10 proved to be inactive in vitro as inhibitors of cell division.     

Synthesis,photopolymerization, and adhesive properties of hydrolytically stable phosphonic acid‐containing (meth)acrylamides

Three novel dental monomers containing phosphonic acid groups ( 1a and 2a , based on diethyl amino(phenyl)methylphosphonate and 3a based on diethyl 1‐aminoheptylphosphonate) were synthesized in two steps: the reaction of α‐aminophosphonates with acryloyl chloride (for monomers 1a and 3a ) or methacryloyl chloride (for 2a ) to give monomers with phosphonate groups, and the hydrolysis of phosphonate groups by using trimethyl silylbromide. Their (and the intermediates') structures were confirmed by FTIR, ¹H, ¹³C, and ³¹P NMR spectroscopy. All the monomers dissolve well in water (1<pH<2) and are hydrolytically stable. Their homo‐ and copolymerizations with 2‐hydroxyethyl methacrylate (HEMA) and HEMA/glycerol dimethacrylate were investigated with photo‐DSC. Thermal polymerization of the new monomers in water or in ethanol/water solution was investigated, giving polymers in good yields. X‐ray diffraction results showed only dicalcium phosphate dehydrate formation upon interaction of 1a ‐ 3a with hydroxyapatite indicating its strong decalcification and that monomer‐Ca salts are highly soluble. Some results were also compared to those with a bisphosphonic acid‐containing methacrylamide ( 4a ) previously reported; and the influence of monomer structure on polymerization/adhesive properties is discussed. These properties, especially hydrolytic stability and good rates of polymerization, make these new monomers suitable candidates as components of dental adhesive mixtures. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 511–522     

Improved straightforward chemical synthesis of dihydroxyacetone phosphate through enzymatic desymmetrization of 2,2-dimethoxypropane-1,3-diol

Dihydroxyacetone phosphate (DHAP) was synthesized in high purity and yield in four steps starting from dihydroxyacetone dimer (DHA) (47% overall yield). DHA was converted into 2,2-dimethoxypropane-1,3-diol, which was desymmetrized by acetylation with lipase AK. The alcohol function was phosphorylated to give dibenzyl phosphate ester 4. From 4, two routes were investigated for large-scale synthesis of DHAP. First, acetate hydrolysis was performed prior to hydrogenolysis of the phosphate protective groups. The acetal hydrolysis was finally catalyzed by the phosphate group itself. Second, acetate and acetal hydrolysis were performed in one single step after hydrogenolysis.     

Determination of ethyl glucuronide in human serum by hyphenation of capillary isotachophoresis and zone electrophoresis

The determination of ethyl glucuronide (EtG), a marker of recent alcohol consumption, in human serum by hyphenation of capillary ITP (CITP) and CZE is reported. For CITP step, 1 x 10(-2) M hydrochloric acid adjusted with epsilon-aminocaproic acid (EACA) to pH 4.4 was used as the leading electrolyte, and 1 x 10(-2) M nicotinic acid with EACA, pH 4.4, was used as the terminating electrolyte (TE). All electrolytes contained 0.2% hydroxypropylcellulose to suppress electroosmosis. In CITP, EtG was separated from fast serum macrocomponents chloride, phosphate, lactate, and acetate. Zones of microcomponents including EtG that migrated between acetate and nicotinate were forwarded to the second capillary filled with a BGE identical with the TE. Conductivity detection was used in the CITP step. Sensitive detection in the CZE step was performed using indirect spectrophotometric detection at 254 nm. The assay is based on a 1:5 dilution of serum with deionized water and has a concentration LOD for EtG in diluted sample of 9.8 x 10(-9) M. The method was used for the determination of EtG in sera of volunteers consuming alcohol.     

Efficient synthesis and hydrolysis of cyclic oxalate esters of glycols

Based on the mechanism postulated for the formation of the cyclic carbonates 3 in the reactions of glycols 1 with oxalyl chloride in the presence of triethylamine, we present here three efficient syntheses of the cyclic oxalates 2 of various glycols 1 by controlling the formation of 3: replacement of the base by pyridine markedly diminishes yields of 3 in all reactions, realizing dramatic reversals of the product ratios in the reactions with the (R*,R*)-compounds 1g-i,q,r and pinacol (1k); although considerable amounts of the oxalate polymers are formed in the reactions with some (R*,S*)-glycols, this drawback can be removed by the use of 2,4,6-collidine instead of pyridine; 1,1'-oxalyldiimidazole is useful for the synthesis of two selected cyclic oxalates 2e,f. The cyclic oxalates 2 other than trisubstituted and tetrasubstituted ones were found to be very reactive: kinetic studies on the hydrolysis of 1,4-dioxane-2,3-dione (2a) as well as its mono- and some selected 5,6-disubstituted derivatives 2 have revealed that they undergo hydrolysis 260-1500 times more rapidly than diethyl oxalate (12) in acetate buffer-acetonitrile (pH 5.69) at 25 degrees C. Although the cyclic oxalate 21 from cis-1,2-cyclopentanediol (11) was 1.5 times more reactive than 2a, it has been shown with other substrates that increasing number of the alkyl substituents decreases the rate of hydrolysis. On the contrary, the phenyl group was found to have somewhat accelerative effect.     

Synthesis and spectroscopic examination of various substituted 1,3-dibenzoylmethane, active agents for UVA/UVB photoprotection

We describe the synthesis of eighteen variously substituted 1,3- dibenzoylmethane (1,3-DBM) and their change in absorption spectra depending of the nature of donor or acceptor substituents on one or the two aromatic moieties. These compounds were prepared in two steps starting from the corresponding acetophenones, phenol and benzoyl chlorides. The phenyl benzoate was obtained by condensation of benzoyl chloride with phenol in a classical way. Stirring of the phenyl benzoate and acetophenone in DMSO with powdered sodium hydroxide for a few minutes gave the dibenzoylmethane in yields depending on substituents on the phenyl rings. Changes in absorption of UVA/UVB sunlight of these molecules were observed according to the nature and the position of substituents on the phenyl rings. Molecules 2b (1-phenyl-3-(3,4,5-trimethoxyphenyl)-1,3-propanedione), 2d (1-(3,4-dimethoxyphenyl)-3-phenyl-l,3-propanedione), 2e (1-(2,3-dimethoxyphenyl)-3-phenyl-l,3-propanedione) and 2f (1-(2,3,4-trimethoxyphenyl)-3-phenyl-l,3-propanedione) were the most interesting for cosmetic applications because even after irradiation, they preserve their absorptive in UVA range and also in UVB range The other compounds are too photounstable and so can lose their protective effects. These results showed the lack of phototoxicity of these compounds and the possibility to use them as solar filters. Therefore, variously di- or tri methoxy 1,3-DBM are interesting molecules in term of photoprotection and open new prospects for UVA photostable filters.     

Urea-, squaramide-, and sulfonamide-based anion receptors: a thermodynamic study

In this work, we compare the anion-binding capabilities of receptors 1-5, characterized by similar structures, but possessing different hydrogen-bond-donor moieties (urea, squaramide, and sulfonamide). The presence of chromophoric substituents on the receptor's skeleton allowed the determination of association constants by performing UV/Vis titrations with the investigated anions on solutions of the receptors in pure acetonitrile. Additional quantitative studies of the anion-binding properties of receptors 1-5 were performed by isothermal titration calorimetry (ITC). The experimental results indicated that 1 and 2 formed 1:1 hydrogen-bonded complexes with most of the anions investigated. In the case of receptors 3-5, the formation of the 1:1 adduct was observed only with anions of low basicity (i.e., chloride, bromide, iodide, and hydrogen sulfate). With more basic anions (i.e., acetate and dihydrogen phosphate), both spectrophotometric and ITC titrations accounted for the deprotonation of the sulfonamide group, involving the formation of the conjugated base of the receptor.     

Synthetic, Mechanistic, and Structural Studies Related to 1,2,4-Dithiazolidine-3,5-dione

Reaction of O-ethyl thiocarbamate (4) with (chlorocarbonyl)sulfenyl chloride (5) gives 3-ethoxy-1,2,4-dithiazolin-5-one (2) and 3,5-diethoxy-1,2,4-thiadiazole (3), with the relative amounts of 2 and 3 formed depending very much on the solvent (e.g., diethyl ether favors 2; chloroform favors 3). The effects of added base, order of addition, concentration, and temperature were also studied. Mechanisms for the observed transformations have been proposed and are supported by the characterization of relatively unstable acyclic intermediates, e.g., formimidoyl(chlorocarbonyl)disulfane 8, symmetrical bis(formimidoyl)disulfane 10, and ethoxythiocarbonyl imidate 11, which are obtained under alternative conditions. Compound 2 is converted with concentrated aqueous hydrochloric acid upon short reflux to 1,2,4-dithiazolidine-3,5-dione (1), rearranges upon prolonged melting to give principally N-ethyl-1,2,4-dithiazolidine-3,5-dione (13), and is desulfurized with various trivalent phosphorus compounds to yield O-ethyl cyanate (15) plus carbonyl sulfide. X-ray crystallographic structures of 1 and 2 have been solved; the planarity and aromatic character of these molecules help to explain some of their reactions.     

Microanalysis of dialkylphosphorus metabolites of organophosphorus pesticides in human blood by capillary gas chromatography and by phosphorus-selective and ion trap detection

A procedure for the determination of dialkyphosphorus metabolites of organophosphorus pesticides in human blood has been worked out. Dimethyl and diethyl phosphates, phosphorothioates and phosphorodithioates, extracted with diethyl ether from plasma acidified with hydrochloric acid, were methylated with diazomethane and analysed by capillary gas chromatography with an alkali flame ionization detector and an ion trap detector. The extraction of metabolites was preceded by n-hexane extraction of parent organophosphorus pesticides without a negative effect on the efficiency of metabolite extraction. If plasma samples, containing 2 μ/ml of each metabolite, were not saturated with sodium chloride before extraction, only dialkyl phosphorothioates were recovered by more than 80%. The recoveries of other metabolites were less than 25%. The extraction of plasma samples saturated with sodium chloride resulted in higher recoveries of all metabolites. At concentrations ranging from 0.2 to 2.8 μg/ml the accumulation effeciencies (%±S.D.) of dimethyl and diethyl phosphorothioates were 92±20 and 97±11, and those of corresponding phosphorodithiotes 79±7 and 71±4. A significantly lower recovery (36±12%) was determined for dimethyl phosphate at concentrations in plasma below 2 μg/ml. The recovery of diethyl phosphate was dependent on the initial metabolite concentration in plasma being 31±5% at concentrations lower than 0.5 μg/ml, 51±12% at concentrations ranging from 0.7 to 1.7 μg/ml and 97±3% at concentrations at or above 2 μg/ml. Detection limits of metabolites in plasma using the phosphorus selective detector were 150 ng/ml for dimethyl phosphate and 50 ng/ml for other metabolites. Those values were for dialkyl phosphates and phophorothioates three to five times lower and for diakyl phosphorodithiotes even 30 times lower than detection limits achieved by the use of ion trap detector. The procedure was applied for the evidence and confirmation of human poisoning with organophosphorus pesticides.