- A mechanistic dehydration study with [2-13C]-DIMBOA
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Dehydration of a 2-13C-labeled synthetic sample of the natural aglucone 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one ([2-13C]-DIMBOA, 10) using N-ethoxycarbonyltrichloroacetaldimine led to 3-formyl-6-methoxybenzoxazolin-2(3H)-one (13C-labeled FMBOA, 11) with complete transfer of the 13C label into the -CHO group. On the basis of this finding, a mechanism for the dehydration is proposed.
- Hao, Huang,Sieler, Joachim,Sicker, Dieter
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- Acridino-diaza-20-crown-6 ethers: New macrocyclic hosts for optochemical metal ion sensing
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Acridino-diaza-20-crown-6 ether derivatives as new turn-on type fluorescent chemosensors with an excellent functionality and photophysical properties have been designed and synthesized for metal ion-selective optochemical sensing applications. Spectroscopic studies revealed that in an acetonitrile-based semi-aqueous medium, the sensor molecules exhibited a remarkable fluorescence enhancement with high sensitivity only toward Zn2+, Al3+ and Bi3+, among 23 different metal ions. Studies on complexation showed a great coordinating ability of logK > 4.7 with a 1:1 complex stoichiometry in each case. The detection limits were found to be from 59 nM to micromoles. The new ionophores enabled an optical response without being affected either by the pH in the range of 5.5–7.5, or the presence of various anions or competing metal ions. Varying the N-substituents of the new host-backbone provides diverse opportunities in both immobilization and practical applications without influencing the molecular recognition abilities.
- Golcs, ádám,Huszthy, Péter,Kovács, Korinna,Tóth, Tünde,Vezse, Panna
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- FUNGICIDAL 2-(BICYCLIC ARYLOXY)CARBOXAMIDES
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Disclosed are compounds of Formula 1, N-oxides, and salts thereof, (Formula 1 should be inserted here) wherein Q is O or S; Z1 and Z2 are each independently CR9 or N; and R1, R2, R3, R4, R5, R6, R7, R8 and R9 are as defined in the disclosure. Also disclosed are compositions containing the compounds of Formula 1 and methods for controlling plant disease caused by a fungal pathogen comprising applying an effective amount of a compound or a composition of the invention.
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Page/Page column 79
(2012/07/13)
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- Simple, rapid procedure for the synthesis of chloromethyl methyl ether and other chloro alkyl ethers
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Zinc(II) salts catalyze the reaction between acetals and acid halides to provide haloalkyl ethers in near-quantitative yield. Reactions from millimole to mole scale are typically complete in 1-4 h with 0.01 mol % catalyst. The solutions of haloalkyl ethers thus obtained can be utilized directly in reactions in which the presence of the ester byproduct does not interfere. Excess haloalkyl ether is destroyed on workup, thereby minimizing exposure to this class of carcinogenic compounds.
- Berliner, Martin A.,Belecki, Katherine
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p. 9618 - 9621
(2007/10/03)
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- Chloropyridylcarbonyl derivatives
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Novel chloropyridylcarbonyl derivatives of the formula STR1 in which Het is STR2 n is 1 or 2, R1 is hydrogen, optionally substituted C1-6 alkyl, optionally substituted C2-6 alkenyl, optionally substituted C3-6 alkynyl, optionally substituted phenyl or optionally substituted pyrimidinyl, and R2 and R3, independently of each other, are hydrogen or C1-4 alkyl, and acid addition salts and metal salt complexes thereof, are outstandingly active as microbicides.
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- Cross Aldol Products from α-Haloalkoxysilanes and Silyl Enol Ethers
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α-Haloalkoxysilanes have been prepared by cleavage of the C-S bond in O,S-acetals with sulfuryl chloride, and by cleavage of C-Sn bond in α-silyloxystannanes by bromine.The α-haloalkoxysilanes, both after isolation or after preparation in situ react with silyl enol ethers to yield silyl-protected cross aldol products.The reaction is catalyzed by Lewis acids.
- Antonsen, Oeyvind,Benneche, Tore,Gundersen, Lise-Lotte,Undheim, Kjell
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p. 172 - 177
(2007/10/02)
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- Dual Reactivity of Methoxymethyl Benzenesulfonate in Nucleophilic Substitution
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Hydrolysis of methoxymethyl benzenesulfenate is catalyzed by both acid and base.Acid-catalyzed hydrolysis is further accelerated by various nucleophiles like halide ions, thiocyanate, dialkyl sulfide, and the substrate itself.The catalytic constants coincide with those for ethyl benzenesulfenate within 2-fold in magnitude.The nucleophilic reactivity strongly suggests the reaction at the sulfenyl sulfur, but examination of the products from the 18O-labeled substrate showed that the bond cleavage occurs mostly between the oxygen and the proformyl carbon except for the acid-catalyzed water reaction which undergoes the S-O cleavage.A mechanism for a nucleophilic reaction at the sulfur to form a sulfurane intermediate which breaks down with the C-O cleavage is presented.The hydrolysis rate is also strongly dependent on the second order of buffer concentrations in carboxylate and tertiary amine buffer solutions.The third-order term involves both the general acid and the conjugate base of the buffer, and the latter reacts at the sulfur as a nucleophile in the rate-determining step but leads to the C-O cleavage in the same way as the other catalytic nucleophiles.
- Okuyama, Tadashi,Fueno, Takayuki
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p. 2672 - 2683
(2007/10/02)
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- Mechanism of Reactions of N-(Methoxymethyl)-N,N-dimethylanilinium Ions with Nucleophilic Reagents
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The prediction that the oxocarbonium ion derived from formaldehyde should have a "lifetime" of ca. 10-15 s that gives rise to an enforced preassociation or concerted reaction mechanism has been tested by examining the reactions of N-(methoxymethyl)-N,N-dimethylanilinium ions in water in the presence of added nucleophilic reagents.These compounds undergo well-behaved second-order reactions with nucleophiles and give the amount of substitution product that is expected from the rate increase in the presence of nucleophile.Structure-reactivity correlations exhibit behavior intermediate between that expected for SN2 (Swain-Scott) and carbonium ion (N+) reactions.The small values of s = 0.3 and βnuc = 0.14 and large values of β1g = -0.7 to -0.9 indicate a transition state that can be described either as an open transition state for SN2 displacement or as an oxocarbonium ion that is stabilized by weak interactions with the entering and leaving groups.Secondary α-deuterium isotope effects for the second-order reactions range from (kH/kD)/D = 0.99 for fluoride ion to 1.18 for iodide ion.Solvolysis and the second-order reaction with n-propylamine exhibit values of ΔS(ex) = -1.2 and -2.1 cal K-1 mol-1, respectively, and display similar changes in rate in mixed water-alcohol solvents.It is suggested that the lifetime of the carbonium ion species in the presence of nucleophiles is so short that the reaction mechanism must be concerted.
- Knier, Barry L.,Jencks, William P.
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p. 6789 - 6798
(2007/10/02)
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