TFA-Mediated Tandem Friedel−Crafts Alkylation/Cyclization/Hydrogen Transfer Process for the Synthesis of Flavylium Compounds
摘要:
[Graphics]The tandem reaction of phenols and chalcones in refluxing TFA gave the flavylium species of 2-hydroxy-2-phenyl-2H-chromenes in moderate to good isolated yields. The reaction was proposed to involve a tandem transformation of Friedel-Crafts alkylation, dehydrative cyclization, intermolecular hydrogen transfer, and hydration. As a multifunctional catalyst, TFA mediated the processes efficiently and cleanly.
Palladium-catalyzed conjugate addition type reaction of (2-hydroxyaryl)mercury chlorides with .alpha.,.beta.-unsaturated ketones in a two-phase system. A new synthesis of 2-chromanols and 2-chromenes
carried out at 0–25 °C in the presence of a dicationic palladium(II) catalyst, [Pd(S,S-chiraphos)(PhCN)2](SbF6)2. Addition of a silver salt such as silvertetrafluoroborate [AgBF4] or silver hexafluoroantimonate [AgSbF6] (5–10 mol %) was effective to achieve high enantioselectivities at low temperatures (92–99 % ee) and to reduce the catalyst loading to 0.05 mol %. The protocol provided a simple access to
Compounds of formula (I): wherein variable groups are as defined within; for use in the inhibition of 11βHSD1 are described.
描述了式(I)的化合物:其中变量基团如定义的那样;用于抑制11βHSD1。
Reaction of 3-halogeno-2H-1-benzopyran-2-ones with organometallic compounds. Synthesis of 4-Alkyl-2H-1-benzopyran-2-ones. X-Ray molecular structure of 3-bromo-3,4-dihydro-4-isopropylcoumarin
作者:Angel Alberola、Blanca Calvo、Alfonso Gonzalez Ortega、Martina Vicente、Santiago G. Granda、Juan F. Van der Maelen
DOI:10.1039/p19910000203
日期:——
3-Halogeno-2H-1-benzopyran-2-ones react with magnesium, lithium, aluminium and copper derivatives to give 3,4-dihydrocoumarins and 3-(o-hydroxyphenyl)propenols as major products. The nature and the ratio of the products in the final mixture depend on the solvent and on the organometallic reagent. Grignard derivatives yield 1,4-monoalkylation compounds in tetrahydrofuran (THF) or 1,2-dialkylation derivatives in toluene. In some cases the dehalogenation competes with the 1,2-alkylation process in the reactions with alkyllithiums. The presence of the halogen at C-3 increases the reductive ability of organoaluminiums. In general, the reaction with lithium dialkylcuprates leads to complex mixtures of products. The 4-alkyl-3-halogeno-3,4-dihydrocoumarins obtained undergo dehydrohalogenation easily, and lead to 4-alkylcoumarins in good yields. The tandem alkylation-dehydrohalogenation of 3-halogeno-2H-1-benzopyran-2-ones constitutes a versatile synthesis of 4-alkylcoumarins.
ALBEROLA, ANGEL;CALVO, BLANCA;ORTEGA, ALFONSO GONZALEZ;VICENTE, MARTINA;G+, J. CHEM. SOC. PERKIN TRANS. PT 1,(1991) N, C. 203-210
作者:ALBEROLA, ANGEL、CALVO, BLANCA、ORTEGA, ALFONSO GONZALEZ、VICENTE, MARTINA、G+