Metallation of<i>N</i>-(Pivaloyl)- and<i>N</i>-(<i>tert</i>-Butoxycarbonyl)difluoroanilines : Regiocontrol by Fluorine in the Synthesis of 4-Methoxycarbonyl Derivatives
作者:Timothy J. Thornton、Michael Jarman
DOI:10.1055/s-1990-26856
日期:——
Methyl 2,6-difluoro-4-(pivaloylamino)benzoate (3) and the corresponding 4-(tert-butoxycarbonylamino)-analogue 6 have been synthesised by reacting the appropriate 3,5-difluoroaniline derivatives with butyllithium followed by methyl chloroformate. N-(tert-Butoxycarbonyl)-2,3-difluoroaniline (9) required the "super-basic" butyllithium/potassium tert-butoxide mixture to convert it into methyl 4-(tert-butoxycarbonylamino)-2,3-difluorobenzoate (14): the 2,5-difluoro-analogue was formed in a similar manner. In all cases the regiocontrol of metallation was directed by fluorine rather than by the amide substituent.
甲基2,6-二氟-4-(特戊酰氨基)苯甲酸酯(3)和对相应的4-(叔丁氧羰基氨基)类似物6通过将适当的3,5-二氟苯胺衍生物与丁基锂反应后再与甲基氯甲酸酯反应合成。N-(叔丁氧羰基)-2,3-二氟苯胺(9)需要“超级碱性”的丁基锂/叔丁醇钾混合物将其转化为甲基4-(叔丁氧羰基氨基)-2,3-二氟苯甲酸酯(14):2,5-二氟类似物以类似方式形成。在所有情况下,金属化的区域控制都是由氟而非酰胺取代基导向的。