64175-51-5Relevant articles and documents
Pd(OH)2/C, a Practical and Efficient Catalyst for the Carboxylation of Benzylic Bromides with Carbon Monoxide
Wakuluk-Machado, Anne-Marie,Dewez, Damien F.,Baguia, Hajar,Imbratta, Miguel,Echeverria, Pierre-Georges,Evano, Gwilherm
, p. 713 - 723 (2020/02/04)
A simple, efficient, cheap, and broadly applicable system for the carboxylation of benzylic bromides with carbon monoxide and water is reported. Upon simple reaction with only 2.5 wt % of Pearlman's catalyst and 10 mol % of tetrabutylammonium bromide in tetrahydrofuran at 110 °C for 4 h, a range of benzylic bromides can be smoothly converted to the corresponding arylacetic acids in good to excellent yields after simple extraction and acid-base wash. The reaction was found to be broadly applicable, scalable, and could be successfully extended to the use of ex situ-generated carbon monoxide and applied to the synthesis of the nonsteroidal anti-inflammatory drug diclofenac.
Benzofurans as efficient dienophiles in normal electron demand [4 + 2] cycloadditions
Chopin, Nathalie,Gerard, Helene,Chataigner, Isabelle,Piettre, Serge R.
scheme or table, p. 1237 - 1246 (2009/07/04)
Dearomatization of electron-poor benzofurans is possible through involvement of the aromatic 2,3-carbon-carbon double bond as dienophile in normal electron demand [4 + 2] cycloadditions. The tricyclic heterocycles thereby produced bear a quaternary center at the cis ring junction, a feature of many alkaloids such as morphine, galanthamine, or lunaridine. The products arising from the reaction have been shown to depend on different factors among which the type of the electron-withdrawing substituent of the benzofuran, the nature of the reacting diene, and the method of activation. In the presence of all-carbon dienes, the reaction yields the expected Diels-Alder adducts. When thermal activation is insufficient, a biactivation associating zinc chloride catalysis and high pressure is required to generate the cycloadducts in good yields and high stereoselectivities, for instance, when cyclohexadiene is involved in the process. The use of more functionalized dienes, such as those bearing alkoxy or silyloxy substituents, also shows the limits of the thermal activation, and hyperbaric conditions are, in this case, well-suited. The involvement of Danishefsky's diene induces a competition in the site of reactivity. The aromatic 2,3-carbon-carbon double bond is unambiguously the most reactive dienophile, and the 3-carbonyl unit becomes a competitive site of reactivity with benzofurans bearing substituents prone to heterocyloaddition, in particular under Lewis acid activation. The sequential involvment of both the aromatic double bond and the carbonyl moiety as dienophiles is then possible by using an excess of diene under high-pressure activation. In line with the experimental results, DFT computations suggest that the Diels-Alder process involving the aromatic double bond is preferred over the hetero-Diels-Alder route through an asynchronous concerted transition state. However, Lewis acid catalysis appears to favor the heterocycloaddition pathway through a stepwise mechanism in some cases. 2009 American Chemical Society.
Cycloaddition chemistry of 2-vinyl-substituted indoles and related heteroaromatic systems
Padwa, Albert,Lynch, Stephen M.,Mejia-Oneto, Jose M.,Zhang, Hongjun
, p. 2206 - 2218 (2007/10/03)
(Chemical Equation Presented) The intramolecular Diels-Alder cycloaddition reaction (IMDAF) of several N-phenylsulfonylindolyl-substituted furanyl carbamates containing a tethered π-bond on the indole ring were examined as an approach to the iboga alkaloi
