- Synthesis of 3-arylazo-1H-pyridazin-4-ones from difluoroboron chelates of 1,3-diketones
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A convenient method for the synthesis of 6-R-3-arylazo-1H-pyridazin-4-ones from difluoroboron chelates of acetylacetone and aroylacetones was developed. The method is based on the ability of the methyl group of the chelates to react with two equivalents of a diazonium salt.
- Kravtsov,Belyakov,Baranin,Dorokhov
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p. 1561 - 1565
(2008/09/18)
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- 1,3-Dithienium- and 1,3-Dithiolenium Salts, V. Determination of the Relative Reactivity of 1,3-Dithian-2-ylium Tetrafluoroborates by Intermolecular Hydride Ion Transfer
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The 1,3-dithienium- and 1,3-dithiolenium tetrafluoroborates 4 (n=3, 2) react in good yields with the (trimethylsiloxy)alkenes 3 available from β-dicarbonyl compounds to give the 2-substituted 1,3-dicarbonyl compounds 5.Owing to the formation of the difluoroboron acid esters 8 as competition products 3 has to be employed in excess, however.Reaction of 4 (n=3) with 1,3,5-cycloheptatriene (10) leads to the 1,3-dithianes 11 and the more stable tropylium tetrafluoroborate (12).The determination of the corresponding rates of reduction allows in a simple manner the ascertainment of the relative reactivities of 4.Whereas the reactivities of the aryl-substituted representatives of 4 show a sufficient correlation corresponding to the Hammett relationship, the variations of the reactivities of the alkyl substituted salts 4 can be explained on the basis of hyperconjugative stabilization.
- Stahl, Ingfried
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p. 4857 - 4868
(2007/10/02)
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- The preparation and properties of some tetracoordinate boron compounds. The pseudo-metal ion concept
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The infrared, ultraviolet, H1 and B11 nuclear magnetic resonance spectra, and polarographic behavior of a series of R2B complexes possessing tetrahedral geometry indicate that they and similar derivatives can serve as excellent models with which to study chelate characteristics. The R2B moiety functions as a pseudo-metal ion or atom which permits alteration of total and effective charge without variation in size of the chelate ring and permits placement and surveying of probes to study the electron distribution in the chelates.
- Toporcer,Dessy,Green
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p. 1649 - 1655
(2007/10/05)
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