Coupling of Quinone Monoacetals Promoted by Sandwiched Brønsted Acids: Synthesis of Oxygenated Biaryls
作者:Toshifumi Dohi、Naohiko Washimi、Tohru Kamitanaka、Kei-ichiro Fukushima、Yasuyuki Kita
DOI:10.1002/anie.201101646
日期:2011.6.27
Unusual protons: Brønsted acids sandwiched between sheets of solid acids, such as montmorillonites, activated quinone monoacetals 1 to selectively react with aromatic nucleophiles 2 in an unprecedented substitution reaction. The syntheticutility of the strategy for obtaining highly oxygenated biaryls 3 is highlighted by the synthesis of gilvocarcin aglycones.
A mild and concise [3+2] coupling of quinonemonoacetals or quinoneimineketals with vinylcarbamates promoted by Lewisacid was realized. Various 2-carbamate-2,3-dihydrobenzofurans and 2-carbamate-indolines have been prepared in moderate to good yields.
[3 + 2] Coupling of Quinone Monoacetals by Combined Acid–Hydrogen Bond Donor
作者:Toshifumi Dohi、Yinjun Hu、Tohru Kamitanaka、Naohiko Washimi、Yasuyuki Kita
DOI:10.1021/ol201886r
日期:2011.9.16
expeditious and efficient [3 + 2] coupling approach of quinonemonoacetals 1 with alkene nucleophiles 2 by the action of an activated Brønsted acid in the presence of a hydrogen bond donor perfluorinated alcohol has been achieved. With the optimized combined acid, the reaction could proceed under mild conditions by only mixing the two reactants to afford the cycloadducts 3 in a short time (within 10
[3 + 2] Coupling of Quinone Monoacetals with Vinyl Ethers Effected by Tetrabutylammonium Triflate: Regiocontrolled Synthesis of 2-Oxygenated Dihydrobenzofurans
作者:Tohru Kamitanaka、Yusuke Tsunoda、Yuriko Fujita、Toshifumi Dohi、Yasuyuki Kita
DOI:10.1021/acs.orglett.1c02792
日期:2021.12.3
The synthesis of 2-oxygenated dihydrobenzofurans involving the [3 + 2] coupling of quinone monoacetals with vinyl ethers has been realized by tetrabutylammonium triflate catalysis. The reaction involves a new activation method of the acetal moiety in quinone monoacetals under acid-free conditions affording the highly oxygenated dihydrobenzofurans. This new activation mode was achieved by using the
An Efficient, Simple and Inexpensive Method for the Preparation of 1,4-Benzoquinone Monoketals<i>via</i>Anodic Oxidation of 1,4-Dimethoxybenzenes
作者:Elisabeth C. L. Gautier、Norman J. Lewis、Alexander McKillop、Richard J.K. Taylor
DOI:10.1080/00397919408010619
日期:1994.11
Anodic oxidation of a series of 1-substituted-2,5-dimethoxybenzenes gives 2-substituted-1,1,4,4-tetramethoxycyclohexa-2,5-dienes in almost quantitative crude yield. Selective monohydrolysis of these bis-ketals is possible in many cases, and gives 3-substituted-4,4-dimethoxycyclohexa-2,5-dienones in good to excellent overall yield.