methoxymethyl protecting group, with 7‐endo‐trig alkoxycyclization then dominating instead (see scheme). In addition, the regioselectivity of the La‐catalyzed cycloetherification can be modulated (5‐exo versus 6‐endo versus 7‐endo) simply through subtle variation in the functionalization of the allene component.
指导环化:通过改变
金属(Pd代替Au)或使用甲氧基甲基保护基,可以完全逆转γ-烯醇的5 -exo-trig环化途径,然后以7 - endg -trig烷氧基环化为主(参见方案)。此外,La催化的
环醚化的区域选择性可以通过亚丙基成分功能的细微变化来调节(5- exo与6- end对7- endo)。