作者:Eva Castagnetti、Manfred Schlosser
DOI:10.1002/1521-3765(20020215)8:4<799::aid-chem799>3.0.co;2-6
日期:2002.2.15
rather than next to the strongly electron-withdrawing CF(3)O group. 1,3-Benzodioxole undergoes ortho lithiation only six times faster than anisole, whereas 2,2-difluoro-1,3-benzodioxole reacts about 5000 times faster, as evidenced by competition experiments. The structure and distance dependence of substituent effects can be rationalized by assuming superposing sigma- and pi-polarizing interactions.
从其促进邻位氢/金属排列的能力判断,三氟甲氧基优于甲氧基和三氟甲基。而且,像CF(3)一样,与OCH(3)不同,OCF(3)发挥了远距离作用,当位于更遥远的间位甚至对位时,仍会大大降低芳基金属化合物的碱性。结果,4-(三氟甲氧基)苯甲醚主要在邻近OCH(3)的位置而不是在强吸电子的CF(3)O处被仲丁基锂去质子化,而仅由叔丁基锂去质子化。组。竞争实验证明,1,3-苯并二恶唑的邻位锂化速度仅比苯甲醚快六倍,而2,2-二氟-1,3-苯并二恶唑的反应速度快约5000倍。