Synthesis of derivatives of 1-phenylhydropyrimidines

The synthesis has been effected, via the corresponding N-phenyl-ß-aminopropionic acids, of 1-(o-methoxyphenyl)-, 1-(o-ethoxyphenyl)-, and 1-(o-tolyl)dihydrouracils and also of 1-(o-methoxyphenyl)-, 1-(o-ethoxyphenyl)-, and 1-(o-tolyl)-2-thiodihydrouracils. The dihydrouracits and thiodihydrouracils obtained have been reduced with LiAlH₄ to the corresponding 2-oxohexahydro-, and 2-thioxohexahydropyrimidines. By the action of bromine and the subsequent splitting out of HBr, the dihydrouracils have been converted into 1-(o-methoxyphenyl)-, 1-(o-ethoxyphenyl)-, and 1-(o-tolyl)uracils.     

Influence of terpyridine as pi-acceptor ligand on the kinetics and mechanism of the reaction of NO with ruthenium(III) complexes

The kinetics of the unusually fast reaction of cis- and trans-[Ru(terpy)(NH3)2Cl]2+ (with respect to NH3; terpy=2,2':6',2"-terpyridine) with NO was studied in acidic aqueous solution. The multistep reaction pathway observed for both isomers includes a rapid and reversible formation of an intermediate Ru(III)-NO complex in the first reaction step, for which the rate and activation parameters are in good agreement with an associative substitution behavior of the Ru(III) center (cis isomer, k1=618 +/- 2 M(-1) s(-1), DeltaH(++) = 38 +/- 3 kJ mol(-1), DeltaS(++) = -63 +/- 8 J K(-1) mol(-1), DeltaV(++) = -17.5 +/- 0.8 cm3 mol(-1); k -1 = 0.097 +/- 0.001 s(-1), DeltaH(++) = 27 +/- 8 kJ mol(-1), DeltaS(++) = -173 +/- 28 J K(-1) mol(-1), DeltaV(++) = -17.6 +/- 0.5 cm3 mol(-1); trans isomer, k1 = 1637 +/- 11 M(-1) s(-1), DeltaH(++) = 34 +/- 3 kJ mol(-1), DeltaS(++) = -69 +/-11 J K(-1) mol(-1), DeltaV(++) = -20 +/- 2 cm3 mol(-1); k(-1)=0.47 +/- 0.08 s(-1), DeltaH(++)=39 +/- 5 kJ mol(-1), DeltaS(++) = -121 +/-18 J K(-1) mol(-1), DeltaV(++) = -18.5 +/- 0.4 cm3 mol(-1) at 25 degrees C). The subsequent electron transfer step to form Ru(II)-NO+ occurs spontaneously for the trans isomer, followed by a slow nitrosyl to nitrite conversion, whereas for the cis isomer the reduction of the Ru(III) center is induced by the coordination of an additional NO molecule (cis isomer, k2=51.3 +/- 0.3 M(-1) s(-1), DeltaH(++) = 46 +/- 2 kJ mol(-1), DeltaS(++) = -69 +/- 5 J K(-1) mol(-1), DeltaV(++) = -22.6 +/- 0.2 cm3 mol(-1) at 45 degrees C). The final reaction step involves a slow aquation process for both isomers, which is interpreted in terms of a dissociative substitution mechanism (cis isomer, DeltaV(++) = +23.5 +/- 1.2 cm3 mol(-1); trans isomer, DeltaV(++) = +20.9 +/- 0.4 cm3 mol(-1) at 55 degrees C) that produces two different reaction products, viz. [Ru(terpy)(NH3)(H2O)NO]3+ (product of the cis isomer) and trans-[Ru(terpy)(NH3)2(H2O)]2+. The pi-acceptor properties of the tridentate N-donor chelate (terpy) predominantly control the overall reaction pattern.     

Cyclodextrin complexation of a stilbene and the self-assembly of a simple molecular device

(E)-4-tert-Butyl-4'-oxystilbene, 1(-), is thermally stable as the (E)-1(-) isomer but may be photoisomerized to the (Z)-1(-) isomer as shown by UV-vis and (1)H NMR studies in aqueous solution. When (E)-1(-) is complexed by alphaCD two inclusion isomers (includomers) form in which alphaCD assumes either of the two possible orientations about the axis of (E)-1(-) in alphaCD.(E)-1(-) for which (1)H NMR studies yield the parameters: k(1)(298 K)= 12.3 +/- 0.6 s(-1), DeltaH(1)(++)= 94.3 +/- 4.7 kJ mol(-1), DeltaS1(++)= 92.0 +/- 5.0 J K(-1) mol(-1), and k(2)(298 K)= 10.7 +/- 0.5 s(-1), DeltaH(2)(++)= 93.1 +/- 4.7 kJ mol(-1), DeltaS2(++)= 87.3 +/- 5.0 J K(-1) mol(-1) for the minor and major includomers, respectively. The betaCD.(E)-1(-) complex either forms a single includomer or its includomers interchange at the fast exchange limit of the (1)H NMR timescale. Complexation of 1(-) by N-(6(A)-deoxy- alpha-cyclodextrin-6(A)-yl)-N'-(6(A)-deoxy- beta-cyclodextrin-6(A)-yl)urea, results in the binary complexes 2.(E)-1(-) in which both CD component annuli are occupied by (E)-1(-) and which exists exclusively in darkness and 2.(Z)-1(-) in which only one CD component is occupied by (Z)-1(-) and exists exclusively in daylight at lambda > or = 300 nm. Irradiation of solutions of the binary complexes at 300 and 355 nm results in photostationary states dominated by 2.(E)-1(-) and 2.(Z)-1(-), respectively. In the presence of 4-methylbenzoate, 4(-), 2.(Z)-1(-) forms the ternary complex 2.(Z)-1(-).4(-) where 4(-) occupies the second CD annulus. Interconversion occurs between 2.(Z)-1(-).4(-) and 2.(E)-1(-)+4(-) under the same conditions as for the binary complexes alone. Similar interactions occur in the presence of 4-methylphenolate and 4-methylphenylsulfonate. The two isomers of each of these systems represent different states of a molecular device, as do the analogous binary complexes of N,N-bis(6(A)-deoxy- beta-cyclodextrin-6(A)-yl)urea, 3, [3.(E)-1(-) and 3.(Z)-1(-), where the latter also forms a ternary complex with 4(-).     

Determination of interconversion barriers by dynamic gas chromatography: epimerization of chalcogran

The four stereoisomers of chalcogran 1 ((2RS,SRS)-2-ethyl-1,6-di-oxaspiro[4.4]nonane), the principal component of the aggregation pheromone of the bark beetle pityogenes chalcographus, are prone to interconversion at the spiro center (C5). During diastereo- and enantioselective dynamic gas chromatography (DGC), epimerization of 1 gives rise to two independent interconversion peak profiles, each featuring a plateau between the peaks of the interconverting epimers. To determine the rate constants of epimerization by dynamic gas chromatography (DGC), equations to simulate the complex elution profiles were derived, using the theoretical plate model and the stochastic model of the chromatographic process. The Eyring activation parameters of the experimental interconversion profiles, between 70 and 120 C in the presence of the chiral stationary phase (CSP) Chirasil-beta-Dex, were then determined by computer-aided simulation with the aid of the new program Chrom-Win: (2R,5R)-1: deltaG(++) (298.15 K) = 108.0 +/-0.5 kJ mol(-1), deltaH(++) = 47.1+/-0.2 kJ mol(-1), deltaS(++) = -204+/-6 JK(-1) mol(-1): (2R,5S)-1: deltaG(++) (298.15 K) = 108.5+/-0.5 kJ mol(-1), deltaH(++) = 45.8+/-0.2 kJ mol(-1), deltaS(++) = -210 +/-6 J K mol(-1); (2S,5S)-1: deltaG(++) (298.15 K)= 108.1+/-0.5 kJ mol(-1), deltaH(++) = 49.3+/-0.3 kJ mol(-1), deltaS(++) = -197+/-8 J K(-1) mol(-1); (2S,5R)-1: deltaG(++) (298.15 K)=108.6+/-0.5 kJ mol(-1), deltaH(++) = 48.0+/-0.3 kJ mol(-1), deltaS(++) = -203+/-8 J K(-1) mol(-1). The thermodynamic Gibbs free energy of the E/Z equilibrium of the epimers was determined by the stopped-flow multidimensional gas chromatographic technique: deltaG(E/Z) (298.15 K)= -0.5 kJ mol(-1), deltaH(E/Z) = 1.4 kJ mol(-1) and deltaS(E/Z) = 6.3 J K(-1) mol(-1). An interconversion pathway proceeding through ring-opening and formation of a zwitterion and an enol ether/alcohol intermediate of 1 is proposed.     

Synthesis of deuterium-labeled derivatives of dimethylallyl diphosphate

Short practical syntheses for five deuterium-labeled derivatives of dimethylallyl diphosphate (DMAPP) useful for enzymological studies are reported. These include the preparation of the C1-labeled derivatives (R)-[1-2H]3-methylbut-2-enyl diphosphate ((R)-[1-2H]1-OPP) and (S)-[1-2H]3-methylbut-2-enyl diphosphate ((S)-[1-2H]1-OPP), the C2-labeled derivative [2-2H]3-methylbut-2-enyl diphosphate ([2-2H]1-OPP), and the methyl-labeled derivatives (E)-[4,4,4-2H3]3-methylbut-2-enyl diphosphate ((E)-[4,4,4-2H3]1-OPP) and (Z)-[4,4,4-2H3]3-methyl-but-2-enyl diphosphate ((Z)-[4,4,4-2H3]1-OPP).     

Synthesis of Urinary Metabolites of Retinoic Acid

Urinary metabolites 5-methyl-5-[2-(2,6,6-trimethyl -3-oxo-1-cyclohexen-1-yl)-vinyl]-2-tetrahydrofuranone (1) and 5-[2-(6-hydroxymethyl-2, 6-dimethyl-3-oxo-1- cyclohexen-1-yl)vinyl]-5-methyl-2-tetrahydrofuranone (2) of retinoic acid have been synthesized from 4-[2,2,6-trimethyl-3-(tetrahydro-2 H -pyran-2-yl)oxy-1-cyclohexen-1-yl]-3-buten-2-one (4) and methyl 2-(3,3-ethylenedioxy-1-butenyl)-1, 3-dimethyl-4-oxo-2-cyclohexene-1-carboxylate (5) .     

Hypohalite ion catalysis of the disproportionation of chlorine dioxide

The disproportionation of chlorine dioxide in basic solution to give ClO2- and ClO3- is catalyzed by OBr- and OCl-. The reactions have a first-order dependence in both [ClO2] and [OX-] (X = Br, Cl) when the ClO2- concentrations are low. However, the reactions become second-order in [ClO2] with the addition of excess ClO2-, and the observed rates become inversely proportional to [ClO2-]. In the proposed mechanisms, electron transfer from OX- to ClO2(k1OBr- = 2.05 +/- 0.03 M(-1) x s(-1) for OBr(-)/ClO2 and k1OCl-= 0.91 +/- 0.04 M(-1) x s(-1) for OCl-/ClO2) occurs in the first step to give OX and ClO2-. This reversible step (k1OBr-/k(-1)OBr = 1.3 x 10(-7) for OBr-/ClO2, / = 5.1 x 10(-10) for OCl-/ClO2) accounts for the observed suppression by ClO2-. The second step is the reaction between two free radicals (XO and ClO2) to form XOClO2. These rate constants are = 1.0 x 10(8) M(-1) x s(-1) for OBr/ClO2 and = 7 x 10(9) M(-1) x s(-1) for OCl/ClO2. The XOClO2 adduct hydrolyzes rapidly in the basic solution to give ClO3- and to regenerate OX-. The activation parameters for the first step are DeltaH1(++) = 55 +/- 1 kJ x mol(-1), DeltaS1(++) = - 49 +/- 2 J x mol(-1) x K(-1) for the OBr-/ClO2 reaction and DeltaH1(++) = 61 +/- 3 kJ x mol(-1), DeltaS1(++) = - 43 +/- 2 J x mol(-1) x K(-1) for the OCl-/ClO2 reaction.     

Kinetics and thermodynamics of the reaction of deoxyhemerythrin with nitric oxide

Deoxyhemerythrin reacts with NO to form a 1:1 adduct shown spectrophotometrically. The kinetics of the formation have been studied directly by stopped-flow measurements at four different temperatures (0.0-23.6 degrees C). The kinetics of the dissociation have been studied, also by stopped-flow techniques, at five different temperatures (4.0-35.1 degrees C) using three different scavengers [Fe(II)(edta)2-, O2 and sperm whale deoxymyoglobin], which gave similar values. For the formation kf = (4.2 +/- 0.2) x 10(6) M-1 s-1, delta Hf not equal = 44.3 +/- 2.3 kJ mol-1, delta Sf not equal to = 30 +/- 8 J mol-1 K-1 and for the dissociation kd = 0.84 +/- 0.02 s-1, delta Hd not equal to 95.6 +/- 2.1 kJ mol-1 delta Sd not equal to = 74 +/- 7 J mol-1 K-1 (25 degrees C, I = 0.2 M and pH 7-8.1). From the kinetic data the thermodynamic data for the formation of HrNO were calculated: Kf = (5.0 +/- 0.3) x 10(6) M-1, delta H = -51.3 +/- 3.1 kJ mol-1 and delta S = -44 +/- 11 J mol-1 K-1 (25 degrees C). The kinetic data suggest that NO occupies the same iron(II) site in deoxyhemerythrin as oxygen does. The equilibrium constant for the formation of Fe(II)(edta)(NO)2- has been redetermined: K1 = (1.45 +/- 0.07) x 10(7) M-1, delta H = -77.5 +/- 1.5 kJ and mol-1 and delta S = -123.5 J mol-1 K-1 (25 degrees C).     

Generation of simple methylenecyclopropenes as reactive intermediates

The dehydrochlorination of either 1,2 - dichloro - 1 - methylcyclopropane or 1 - bromo - 2 - chloro - 2 - methylcyclopropane with potassium t-butoxide yields 2 - t - butoxy - 1 - methylenecyclopropane. These results are interpreted in terms of methylenecyclopropene as a reactive intermediate which is trapped by addition of nucleophile (t-butoxide) to the cyclopropenyl double bond. The introduction of methanethiol to the reaction medium yields 2 - thiomethyl - 1 - methylenecyclopropene 2,2 - Dichloro - 1 - methylenecyclopropane reacts with potassium t-butoxide in tetrahydrofuran to yield trans- and cis - t - butoxybut - 1 - ene - 3 - yne. The addition of thiomethide ion results in the formation of 2,2 - bis(thiomethyl) - 1 - methylenecyclopropane and 2 - t - butoxy - 2 - thiomethyl - 1 - methylenecyclopropane. Other evidence for simple methylenecyclopropenes as reactive intermediates comes from the observation that nucleophiles add nonregiospecifically to the reactive intermediate produced by the dehydrohalogenation of 2 - halo - 1 - alkylidenecyclopropanes. Novel methylenecyclopropane→ cyclopropene transformations were found in the reaction of 2 - halomethylenecyclopropanes with thiomethide ion.     

Novel rearrangement of chloromethylvinylsilanes into allylsilanes. Stereoselective synthesis of metallated allylsilanes from 1-alkynes

Regio and stereoselective hydralumination of 1-(chloromethyldimethylsilyl)-1-alkyne with diisobutylaluminium hydride (DIBAH) affords (Z)-1-(chloromethyldimethylsilyl)-1-(diisobutylalumino)-1-alkene. Treatment of the aluminium-substituted vinylsilane with 3 equivalents of methyllithium affords (E)-1-(trimethylsilyl)-2-lithio-2-alkene as a sole product. Reaction of aluminium-substituted vinylsilane with trimethylaluminium in refluxing heptane produces a mixture of (E)-1-trimethyl-silyl-2-alumino-2-alkene and 2-trimethylsilyl-1-alkene. Reaction of 1-(chloromethyldimethylsilyl)-1-alkyne with triisobutylaluminium gives 2-(isobutyldimethylsilyl)-1-alkene exclusively. Reactions of the lithiated allylsilane with several electrophiles give the corresponding carbometallated products, allylsilanes bearing alkyl, allyl, vinyl, or alkoxycarbonyl groups. Protodesilylation of 3-(trimethylsilylmethyl)-1,3-decadiene gives 3-methylene-1-decene selectively. Reaction of trialkylaluminium with trimethylsilylethyne gives bistrimethylsilylated diene by successive addition of silylethyne to the aluminium reagent; in contrast, chloromethyldimethylsilylethyne gives the mono-adduct regio and stereoselectively.     

Determination of dissociation constants of cyclodextrin-ligand inclusion complexes by electrospray ionization mass spectrometry

The inclusion complexes of four ligands binding to cyclodextrins (CDs) were studied by electrospray ionization mass spectrometry (ESI-MS) and the dissociation constants of the complexes were obtained. The 1:1 stoichiometric inclusion complex was found in the system of CD and fenbufen or aspirin. The obtained KD values of the inclusion complexes of fenbufen binding to alpha-CD and to beta-CD are 4.38x10(-4) mol L(-1) and 2.12x10(-4) mol L(-1), respectively. The KD values of the inclusion complexes of alpha-CD-aspirin and beta-CD-aspirin are 3.33x10(-4) mol L(-1) and 1.83x10(-4) mol L(-1), respectively. A non-linear least squares regression method was applied to validate the results which were consistent with each other. For the system of tetracycline hydrochloride and CD, the 1:1 and 1:2 stoichiometric inclusion complexes were found in the mass spectra. The KD,1 and KD,2 values of the 1:1 and 1:2 stoichiometric inclusion complexes of alpha-CD and tetracycline hydrochloride are 4.47x10(-4) mol L(-1) and 6.51x10(-4) mol L(-1), respectively, and those of beta-CD and tetracycline hydrochloride are 2.26x10(-4) mol L(-1) and 8.57x10(-4) mol L(-1), respectively. For the system of norfloxacin and CD, besides the 1:1 and 1:2 inclusion complexes, the 1:3 stoichiometric inclusion complex was also found. The KD,1, KD,2 and KD,3 of alpha-CD and norfloxacin inclusion complexes are 4.61x10(-4) mol L(-1), 6.05x10(-4) mol L(-1) and 1.45x10(-3) mol L(-1), respectively. The three KD values of beta-CD and norfloxacin are 1.96x10(-4) mol L(-1), 4.93x10(-4) mol L(-1) and 1.15x10(-3) mol L(-1), respectively.     

Oligomerization of indole derivatives with incorporation of thiols

Two molecules of indole derivative, e.g. indole-5-carboxylic acid, reacted with one molecule of thiol, e.g. 1,2-ethanedithiol, in the presence of trifluoroacetic acid to yield adducts such as 3-[2-(2-amino-5-carboxyphenyl)-1-(2-mercaptoethylthio)ethyl]-1Hindole-5-carboxylic acid. Parallel formation of dimers, such as 2,3-dihydro-1H,1'H-2,3'-biindole-5,5'-dicarboxylic acid and trimers, such as 3,3'-[2-(2-amino-5-carboxyphenyl) ethane-1,1-diyl]bis(1H-indole-5-carboxylic acid) of the indole derivatives was also observed. Reaction of a mixture of indole and indole-5-carboxylic acid with 2-phenylethanethiol proceeded in a regioselective way, affording 3-[2-(2-aminophenyl)-1-(phenethylthio)ethyl]-1H-indole-5-carboxylic acid. An additional product of this reaction was 3-[2-(2-aminophenyl)-1-(phenethylthio)ethyl]-2,3-dihydro-1H,1'H-2,3'-biindole-5'-carboxylic acid, which upon standing in DMSO-d6 solution gave 3-[2-(2-aminophenyl)-1-(phenethylthio)ethyl]-1H,1'H-2,3'-biindole-5'-carboxylic acid. Structures of all compounds were elucidated by NMR, and a mechanism for their formation was suggested.     

Hydroxylation of phenolic compounds by a peroxodicopper(II) complex: further insight into the mechanism of tyrosinase

The dicopper(I) complex [Cu2(MeL66)]2+ (where MeL66 is the hexadentate ligand 3,5-bis-{bis-[2-(1-methyl-1H-benzimidazol-2-yl)-ethyl]-amino}-meth ylbenzene) reacts reversibly with dioxygen at low temperature to form a mu-peroxo adduct. Kinetic studies of O2 binding carried out in acetone in the temperature range from -80 to -55 degrees C yielded the activation parameters DeltaH1(not equal) = 40.4 +/- 2.2 kJ mol(-1), DeltaS1)(not equal) = -41.4 +/- 10.8 J K(-1) mol(-1) and DeltaH(-1)(not equal) = 72.5 +/- 2.4 kJ mol(-1), DeltaS(-1)(not equal) = 46.7 +/- 11.1 J K(-1) mol(-1) for the forward and reverse reaction, respectively, and the binding parameters of O2 DeltaH degrees = -32.2 +/- 2.2 kJ mol(-1) and DeltaS degrees = -88.1 +/- 10.7 J K(-1) mol(-1). The hydroxylation of a series of p-substituted phenolate salts by [Cu2(MeL66)O2]2+ studied in acetone at -55 degrees C indicates that the reaction occurs with an electrophilic aromatic substitution mechanism, with a Hammett constant rho = -1.84. The temperature dependence of the phenol hydroxylation was studied between -84 and -70 degrees C for a range of sodium p-cyanophenolate concentrations. The rate plots were hyperbolic and enabled to derive the activation parameters for the monophenolase reaction DeltaH(not equal)ox = 29.1 +/- 3.0 kJ mol(-1), DeltaS(not equal)ox = -115 +/- 15 J K(-1) mol(-1), and the binding parameters of the phenolate to the mu-peroxo species DeltaH degrees(b) = -8.1 +/- 1.2 kJ mol(-1) and DeltaS degrees(b) = -8.9 +/- 6.2 J K(-1) mol(-1). Thus, the complete set of kinetic and thermodynamic parameters for the two separate steps of O2 binding and phenol hydroxylation have been obtained for [Cu2(MeL66)]2+.     

甲磺酸达比加群酯杂质的合成

根据甲磺酸达比加群酯工艺,合成了甲磺酸达比加群酯的7个杂质：3-【【【2-｛［(4-氰基苯基)氨基］甲基｝-1-甲基-1H-苯并咪唑-5-基】羰基】(吡啶-2-基)氨基】丙酸（A）, 3-【【【2-【｛［4-(乙氧基)叔胺基］苯基｝氨基】甲基】-1-甲基-1H-苯并咪唑-5-基】羰基】(吡啶-2-基)氨基】丙酸乙酯盐酸盐(B), 3-【【【2-【｛［(4-甲脒基)苯基］氨基｝甲基】-1-甲基-1H-苯并咪唑-5-基】羰基】(吡啶-2-基)氨基】丙酸乙酯盐酸盐(C), 3-【【【2-【【【4-｛［(己氧基)羰基］氨基亚甲胺基｝苯基】氨基】甲基】-1-甲基-1H-苯并咪唑-5-基】羰基】(吡啶-2-基)氨基】丙酸甲酯盐酸盐(D), 3-【【【2-【【【4-【｛［(己氧基)羰基］氨基｝羰基】苯基】氨基】甲基】-1-甲基-1H-苯并咪唑-5-基】羰基】(吡啶-2-基)氨基】丙酸乙酯(E), 3-【【【2-【【【4-【｛［(己氧基)羰基］氨基｝亚氨甲基】苯基】氨基】甲基】-1-甲基-1H-苯并咪唑-5-基】羰基】(吡啶-2-基)氨基】丙酸(F), (Z)-3-【【【2-【【【4-【｛［(N,N′-二己氧基)羰基］脒基｝亚氨甲基】苯基】氨基】甲基】-1-甲基-1H-苯并咪唑-5-基】羰基】(吡啶-2-基)氨基】丙酸乙酯(G),其结构经¹H NMR和ESI-MS确证。     

1-Arylethylamino-substituted s-triazine derivatives as chiral solvating agents for the determination of the enantiomeric composition of chiral compounds

The development of 2-[(R)-1-(9-anthryl)ethylamino]-4-chloro-6-methoxy-1,3,5-triazine, 2-[(R)-1-(9-anthryl)ethylamino]-4-chloro-6-[(R)-1-(1-naphthyl)ethylamino]-1,3,5-triazine and 2-[(R)-1-(9-anthryl)ethylamino]-4,6-bis-[(R)-1-(1-naphthyl)ethylamino]-1,3,5-triazine as chiral solvating agents (CSAs) for the determination of the enantiomeric composition of derivatized and underivatized chiral compounds is presented. The comparison between the efficiency of these chiral auxiliaries with the corresponding 1-(1-naphthyl)ethylamino substituted s-triazine derivatives is also discussed.     

Synthesis of nucleosides of 5-substituted-1,2,4-triazole-3-carboxamides

Nucleosides of 5-substituted-1,2,4-triazole-3-carboxamides were prepared by the acid-catalyzed fusion procedure and by glycosylation of the appropriate trimethylsilyl derivative. The following nucleosides were obtained in two steps starting from methyl 4-substituted-1,2,4-triazole-3-carboxylates: 5-chloro-1-β- D -ribofuranosyl-1,2,4-triazole-3-carboxamide ( 6 ), 3-chloro-1-β- D -ribofuranosyl-1,2,4-triazole-5-carboxamide ( 5 ), 3-nitro-1-β- D -ribofuranosyl-1,2,4-triazole-5-carboxamide ( 12 ), 3-amino-1-β- D -ribofuranosyl-1,2,4-triazole-5-carboxamide ( 13 ), 5-methyl-1-β- D -ribofuranosyl-1,2,4-triazole-3-carboxamide ( 15 ), and 3-methyl-1-β- D -ribofuranosyl-1,2,4-triazole-5-carboxamide ( 16 ). In addition, 5-amino-1-β- D -ribofuranosyl-1,2,4-triazole-3-carboxamide ( 7 ), and 1-β- D -ribofuranosyl-1,2,4-triazole-3-carboxamide-5-thiol ( 8 ) were prepared from 6 .     

Stereoselective synthesis of optically active disilanes and selective functionalization by the cleavage of silicon-naphthyl bonds with bromine

Optically active disilanes with one chiral silicon center, (R)-1,2-dimethyl-1-(naphth-1-yl)-1,2,2-triphenyldisilane and (R)-1,2,2-trimethyl-2-(4-methoxynaphth-1-yl)-1-(naphth-1-yl)-1-phenyldisilane, were obtained by the reaction of (S)-methyl(naphth-1-yl)phenylchlorosilane (> 99% ee) with methyldiphenylsilyllithium or by the reaction of methyldiphenylchlorosilane with optically active (S)-methyl(naphth-1-yl)phenylsilyllithium and by the reaction of (S)-methyl(naphth-1-yl)phenylchlorosilane (> 99% ee) with dimethyl(4-methoxynaphth-1-yl)silyllithium. Under the optimized conditions, the reactions proceeded with almost complete inversion for the cholorosilanes and retention for the silyl anions. Optically active disilanes with two chiral centers, (1R,2R)-1,2-dimethyl-1,2-di(naphth-1-yl)-1,2-diphenyldisilane and (1S,2S)-1,2-di(4-methoxynaphth-1-yl)-1,2-dimethyl-1,2-diphenyldisilane, were obtained in high optical purity by the reactions of corresponding optically active halogenosilanes (Cl or F) with optically active silyllithiums. The silicon-silicon bond and the silicon-naphthyl bond of (R)-1,1,2-trimethyl-1,2-di(naphth-1-yl)-2-phenyldisilane and (1R,2R)-1,2-dimethyl-1,2-di(naphth-1-yl)-1,2-diphenyldisilane were cleaved without selectivity on bromination. The silicon-(4-methoxynaphth-1-yl) bond of (R)-1,2,2-trimethyl-2-(4-methoxynaphth-1-yl)-1-(naphth-1-yl)-1-phenyldisilane was regiospecifically cleaved, followed by the stereoselective cleavage of the remaining chiral silicon-naphthyl bond (94% inversion). Although the silicon-(4-methoxynaphth-1-yl) bonds of (1S,2S)-1,2-di(4-methoxynaphth-1-yl)-1,2-dimethyl-1,2-diphenyldisilane (> 99% ee) were regioselectively cleaved without silicon-silicon bond scission, remarkable racemization could not be avoided during the one-pot reaction.     

An effective BINAP and microwave accelerated palladium-catalyzed amination of 1-chloroisoquinolines in the synthesis of new 1,3-disubstituted isoquinolines

A facile and microwave accelerated reaction of 1-chloro-3-(4-chlorophenyl)isoquinoline with various heterocyclic amines, catalyzed by Pd, in the presence of BINAP additive and sodium carbonate as the base, leads to the formation of 3-(4-chlorophenyl)-1-(1H-1,2,3-triazol-1-yl)isoquinoline, 3-(4-chlorophenyl)-1-(1H-imidazol-1-yl)isoquinoline and 3-(4-chlorophenyl)-1-(1H-1,2,4-triazol-1-yl)isoquinoline via Buchwald protocol in good yields. Similarly pyrazolylisoquinolines are also reported.     

Synthesis of 1-(4-bromo-1-naphthyl)-dihydrouracil and some of its transformations

1-(4-Bromo-1-naphthyl)dihydrouracil, which is also obtained from 1-(4-bromo-1-naphthyl)--alanine, is formed by the bromination of 1-(1-naphthyl)dihydrouracil. Hydrogenation of 1-(4-bromo-1-naphthyl)dihydrouracil with lithium aluminum hydride yields either 1-(1-naphthyl)-2-oxohexahydropyrimidine or 1-(4-bromo-1-naphthyl)-2-oxohexahydropyrimidine, depending on the solvent used. 1-(4-Bromo-1-naphthyl)-2-oxohexahydropyrimidine is formed by the bromination of 1-(1-naphthyl)-2-oxohexahydropyrimidine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 524–526, April, 1971.     

Photochemistry of peroxoborates: borate inhibition of the photodecomposition of hydrogen peroxide

The UV absorbance and photochemical decomposition kinetics of hydrogen peroxide in borate/boric acid buffers were investigated as a function of pH, total peroxide concentration, and total boron concentration. At higher pH borate/boric acid inhibits the photodecomposition of hydrogen peroxide (molar absorptivity and quantum yield of H(2)O(2) and HO(2) (-), (19.0+/-0.3) M(-1) cm(-1) and 1, and (237+/-7) M(-1) cm(-1) and 0.8+/-0.1, respectively). The results are consistent with the equilibrium formation of the anions monoperoxoborate, K(BOOH)=[H(+)][HOOB(OH)(3) (-)]/([B(OH)(3)][H(2)O(2)]), 2.0 x 10(-8), R. Pizer, C. Tihal, Inorg. Chem. 1987, 26, 3639-3642, and monoperoxodiborate, K(BOOB)=[BOOB(2-)]/([B(OH)(4) (-)][HOOB(OH)(3) (-)]), 1.0+/-0.3 or 4.3+/-0.9, depending upon the conditions, with molar absorptivity, (19+/-1) M(-1) cm(-1) and (86+/-15) M(-1) cm(-1), respectively, and respective quantum yields, 1.1+/-0.1 and 0.04+/-0.04. The low quantum yield of monoperoxodiborate is discussed in terms of the slower diffusion apart of incipient (.)OB(OH)(3) (-) radicals than may be possible for (.)OH radicals, or a possible oxygen-bridged cyclic structure of the monoperoxodiborate.