Syntheses of Anthracenones. 2. Preparation of 1,8-Dimethoxy- (Dimethylanthralin) and 4,5-Dihydroxy-9(10H)-anthracenone (Isoanthralin): A Revision
摘要:
The reduction of 1,8-dimethoxyanthracenedione with zinc dust and aqueous ammonia gives a mixture of 1,8-dimethoxyanthracene and 4,5-dimethoxy-9(10H)-anthracenone, rather than the isomeric 1,8-dimethoxy-9(10H)-anthracenone (dimethylanthralin). This isomer was obtained exclusively using SnCl2 in HCl and acetic acid as reducing agent at room temperature. The structure was confirmed to exist as the tautomeric 1,8-dimethoxy-9-hydroxyanthracene. Furthermore, the reduction of 1,8-diacetoxyanthracenedione with SnCl2 in HCl and acetic acid leads to 1,8-dihydroxy-(10H)-anthracenone (anthralin) rather than 4,5-dihydroxy-9(10H)-anthracenone (isoanthralin), which was prepared by ether cleavage of 4,5-dimethoxy-9(10H)-anthracenone. In light of these findings some biological studies on antipsoriatic anthracenones have to be reconsidered.
Breaking Symmetry with Symmetry: Bifacial Selectivity in the Asymmetric Cycloaddition of Anthracene Derivatives
作者:Carles Rodríguez-Escrich、Rebecca L. Davis、Hao Jiang、Julian Stiller、Tore K. Johansen、Karl Anker Jørgensen
DOI:10.1002/chem.201300142
日期:2013.2.25
Push to activate: A new catalytic strategy for the activation of anthracenederivatives has been developed. From symmetrical starting materials, enantioselective cycloaddition reactions can be achieved by employing a C2‐symmetric aminocatalyst. This selectivity is due to the gain or loss of conjugation between the enamine and the anthracene in the two transition‐state structures. This methodology is demonstrated