Trialkylsilyloxyallyl cations 2 with a π-donating methoxy substituent at the allylic termini are generated from nonhalogenated substrates via treatment of 5b-e with Lewis acids. 2 undergoes stereo- and regioselective cycloaddition with furans yielding 2-methoxy-8-oxabicyclo[3.2.1] oct-6-en-3-ones. Cycloadduct 7 is converted to 2-methoxytropone 14 and thus represents an efficient entry into tropolonoid
通过用
路易斯酸处理5b-e,由非卤化的底物产生在烯丙基末端具有π-供体甲氧基取代基的三烷基甲
硅烷基氧基烯丙基阳离子2。2与
呋喃进行立体和区域选择性环加成反应,生成2-甲氧基-8-氧杂双环[3.2.1] oct-6-en-3-ones。Cycloadduct 7转化为2-甲氧基托酮14,因此代表着有效地进入tropolonoid系统。