- Ion Pairing and Reactivity of the Alkali-Metal and Alkaline-Earth-Metal Derivatives of Ethyl (5-Bromopentyl)acetoacetate
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The effect added alkali-metal and alkaline-earth-metal salts on the rate of intramolecular alkylation of the title compound has been investigated in 99percent aqueous Me2SO.It was found that the rate is practically insensitive to Et4N+ and K+ ions and it is slightly decreased by Na+ ion, but it is strongly depressed by Li+, Ba2+, Sr2+, Ca2+, and Mg2+ ions, the observed effects ranging over nearly 5 powers of ten.Analysis of rate data was carried out by means of a self-consistent approach, as based on the classical Acree hypothesis of independent contributions of free ions and ion pairs to the overall rate.In most cases it was possible to measure the ion pairing association constants (Kip) together with specific rates for reactions of the ion pairs (kip), even when the latter are much lower than the specific rate for reaction of the free ion (ki).The results show that ion pairing decreases in the order Li > Na > K and Mg > Ca > Sr > Ba, which clearly suggests that association is dominated by coulombic interactions.The strong inhibition caused by ion pairing is due to a greater cation interaction with the anionic reactant than with the transition state, where a significant fraction of the available negative charge is concentrated in the C-C bond-forming region.
- Cacciapaglia, Roberta,Mandolini, Luigi
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- FUSED PYRROLE COMPOUNDS, PHARMACEUTICAL AGENTS CONTAINING THE SAME, AND THE USE THEREOF
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The present invention relates to fused pyrrole compounds of the formula 1. in which at least one of the radicals R1, R2, R3 is 4-sulphur-substituted phenyl. These compounds are in particular pyrrolizines, indolizines and heteroanalogues having selective inhibitory action on isoenzyme-2 of prostaglandin H synthase (COX-2). The invention also relates to pharmaceutical compositions which contain these compounds; and the use of these compounds for the treatment of disorders of the rheumatic type.
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- Perkin-Markovnikov Type Reaction Initiated with Electrogenerated Superoxide Ion
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The cyclic condensation of α,ω-dihaloalkanes with acticvated methylene of malonic acid and acetoacetic acid esters is studied using an electrogenerated superoxide ion.Two possible mechanisms for this reaction are postulated.
- Ojima, Fumihiro,Matsue, Tomokazu,Osa, Tetsuo
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p. 2235 - 2238
(2007/10/02)
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