Highly Stereoselective Synthesis of (<i>E</i>)- and (<i>Z</i>)-α-Fluoro-α,β-unsaturated Esters and (<i>E</i>)- and (<i>Z</i>)-α-Fluoro-α,β-unsaturated Amides from 1-Bromo-1-fluoroalkenes via Palladium-Catalyzed Carbonylation Reactions
作者:Jianjun Xu、Donald J. Burton
DOI:10.1021/jo050314a
日期:2005.5.1
(Z)-1-bromo-1-fluoroalkenes and the reduced products underwent similar palladium-catalyzed carboalkoxylation reactions at 70 °C, and the (E)-α-fluoro-α,β-unsaturated esters were stereospecifically obtained. This methodology was also successfully applied for the stereospecific synthesis of (Z)- and (E)-α-fluoro-α,β-unsaturated amides: the palladium-catalyzed carboamidation reaction of high E/Z and (Z)-1-bromo-1-fluoroalkenes
描述了(E)-和(Z)-α-氟-α,β-不饱和酯和(E)-和(Z)-α-氟-α,β-不饱和酰胺的高度立体选择性合成。1-溴-1-氟烯烃(É / ž ≈1:1),它们是容易获得的原料,已经发现异构化为高È / ž比在-20℃下贮存1周后的或通过在254光解纳米 由于已发现(E)异构体在室温下在Pd(0)催化的反应中比相应的(Z)异构体反应更快,因此钯催化的高E / Z的碳烷氧基化反应1-溴-1-氟烯烃导致高ž / é(ż / é ≥98:2)的α氟α,β -不饱和酯的比率。当1-溴-1-氟烯烃(É / ž ≈1:1)用HCOOH / NBU反应3 /钯(II)/ DMF中,(ë) -异构体选择性地减小,并且剩余的(Ž)-1-以基本上纯的异构体形式回收了β-溴-1-氟烯烃。将所得的混合物(ż)-1-溴-1-氟烯烃和还原产物进行类似的钯催化反应carboalkoxylation在70℃,和(Ë立