The synthesis of a dimeric pyranonaphthoquinone (8) was investigated focusing
on a late-stage biaryl coupling of suitably functionalized bromonaphthofurans
by using Suzuki–Miyaura methodology. Bromonaphthofuran (16) underwent
reaction with bis(pinacolato)diboron in the presence of
PdCl2(dppf) to afford boronate ester (21) and
furonaphthofuran (22). ‘In situ’coupling of
the boronate ester (21) with aryl bromide (16) to the desired dimer (11) was
not realized. Bromonaphthofuran (17), prepared by
Diels–Alder/retro-Claisen reaction of bromonaphthoquinone (24) with
diene (25), underwent Suzuki–Miyaura coupling to naphthofuran (27) and
boronate ester (28). Numerous attempts to alter the reaction conditions to
effect homocoupling of bromide (17) to biaryl (19) were unsuccessful.
Bromopyranonaphthoquinone (18) prepared by oxidative rearrangement of (17)
failed to undergo Suzuki–Miyaura coupling.
研究了二聚吡喃萘醌(8)的合成,重点是
的后期双芳基偶联。
通过使用 Suzuki-Miyaura 方法。溴萘并呋喃 (16) 与双(频哪醇)
与双(频哪醇)二硼在 PdCl2(dppf)存在下发生反应。
PdCl2(dppf) 的存在下与双(频哪醇)二硼发生反应,生成硼酸酯 (21) 和
呋喃(22)。硼酸酯
硼酸酯 (21) 与芳基溴化物 (16) 的 "原位 "偶联生成所需的二聚体 (11)。
没有实现。溴代萘呋喃(17)的制备方法是
溴萘醌(24)与二烯(25)的 Diels-Alder/retro-Claisen 反应制备溴萘呋喃(17)。
二烯 (25) 发生 Diels-Alder/retro-Claisen 反应制备的溴萘醌 (17),经 Suzuki-Miyaura 偶联生成萘呋喃 (27) 和
硼酸酯 (28)。为了改变反应条件以实现溴呋喃的同偶联反应,人们进行了无数次尝试。
溴(17)与双芳基(19)的同偶联反应,但都没有成功。
通过 (17) 的氧化重排制备的溴吡喃萘醌 (18)
未能发生铃木-宫浦偶联反应。