Metal triflate-catalyzed cyclization of arylvinylcarbinols: formal synthesis of (±)-dichroanone and (±)-taiwaniaquinone H
作者:Badrinath N. Kakde、Subhadip De、Dhananjay Dey、Alakesh Bisai
DOI:10.1039/c3ra41497c
日期:——
A formal synthesis of diterpenoids viz. the taiwaniaquinoids (±)-dichroanone (1a) and (±)-taiwaniaquinone H (1b) possessing an all carbon quaternary stereocenter has been reported. The key step involves a metal triflate-catalyzed cyclization of arylvinylcarbinols, prepared from β-cyclocitral. The reaction possibly follows a stepwise mechanism via the intermediacy of arylallyl carbocationic species
A very expedient and efficient new route toward taiwaniaquinoids, bearing the 4a-methyltetrahydrofluorene skeleton, is reported. Key steps are the intramolecular Friedel−Crafts alkylation of an aryldiene and the degradative oxidation of a methylenedioxy group; the latter process could also be utilized for building the 2-hydroxy-1,4-benzoquinone unit, which is frequently found in natural products. Utilizing