Selective and Facile Palladium-Catalyzed Amination of 2-Fluoro-4-iodopyridine in the 4-Position under Microwave Conditions
作者:Marko Mihovilovic、Moumita Koley、Michael Schnürch
DOI:10.1055/s-0029-1219940
日期:2010.6
The selective C-N cross-coupling of 2-fluoro-4-iodopyridine with aromatic amines is reported. In contrast to conventional substitutions where C-N bond formation takes place at the 2-position (e.g., 2,4-dichloropyridine), the Buchwald-Hartwig cross-coupling was found to be complementary and exclusive for the 4-position. Reactions were carried out under microwave irradiation typically within 30 minutes. These conditions also allowed a decrease in the amount of base required to 3.5 equivalents compared to 20 equivalents in established protocols. Additionally, use of potassium carbonate as a mild base was sufficient, and good yields of the coupling products were obtained in all cases with the simple system Pd(OAc)2/BINAP.
报道了2-氟-4-碘吡啶与芳香胺的选择性C-N交叉耦合反应。与传统取代反应中C-N键在2-位形成(例如2,4-二氯吡啶)不同,Buchwald-Hartwig交叉耦合反应被发现是互补且仅限于4-位的。反应通常在微波辐射下进行,仅需30分钟。这些条件下还使得所需碱的量减少到3.5当量,相比之下,传统协议中需要20当量。此外,使用温和的碱碳酸钾即可,且在所有情况下,采用简单的Pd(OAc)2/BINAP体系均能获得良好的耦合产物收率。