葸酮(1)与3,5-二甲氧基苯甲醛(2)在吡啶/哌啶中反应生成10-(3,5-二甲氧基苯甲亚基葸酮(3);3经Pd/C催化氢化生成10-(3,5-二甲氧基苄基葸酮(4);4与3.甲氧基苄基氯(5)进行相转移催化烷基化反应生成10-(3,5-二甲氧基苄基)-10-(3-甲氧基苄基)蒽酮(6);6经NaBH4还原生成10-(3,5-二甲氧基苄基)-10-(3-甲氧基苄基)-9(10H)-葸醇(7);7在酸催化下发生选择性1,7-脱水反应,生成高三蝶烯(hornotriptycene)(8).其反应机理可能是7在酸存在下生成正碳离子中间体,然后选择性地亲电进攻富电荷的3,5.二甲氧基苯基,而不进攻3-甲氧基苯基.
Anthrone (1) reacted in pyridine/pipeddine with 3,5-dimethoxybenzaldehyde (2) to give 10-(3,5-dimethoxybenzylidene)-9-anthrone (3). Catalytic hydrogenation (5% Pd on carbon) of 3 afforded 10-(3,5-dimethoxybenzyl)-9-anthrone (4). 10-(3,5-Dimethoxybenzyl)-10-(3-methoxybenzyl)-9-anthrone (6) was obtained by alkylation of anthrone 4 with 3-methoxybenzyl chloride (5). Subsequent reduction of 6 with NaBH4 gave 10-(3,5-dimethoxybenzyl)- 10-(3-methoxybenzyl)-9(10H)-9-anthranol 7. 7 exhibits in the presence of formic acid or p-methylphenyl-sulfonic acid a selective 1,7-elimination of water which leads to homotriptycene (8). It could be assumed that the protonation of the hydroxy group leads to a carbenium ion intermediate which selectively attacks as electrophile the electron-rich benzene ring with 3,5-dimethoxy groups, instead of attacking the benzene ring with 3-methoxy group.