带有两个相似取代基的内部炔烃加成反应的选择性控制对现代有机合成提出了巨大的挑战。在此我们报道了通过使用Co 2 (CO) 8作为催化剂可以实现烷-2-炔与叔硅烷的β-( E )-选择性氢化硅烷化。在催化反应条件下,多种烷-2-炔可以转化为乙烯基硅烷,其中β-( E )异构体作为主要或唯一的氢化硅烷化产物。机理研究表明炔桥二钴物质是可能的中间体。烯基桥联二钴甲硅烷基中间体中取代基之间的空间排斥被认为是引起观察到的区域选择性的关键因素。
Decarboxylative Benzylations of Alkynes and Ketones
摘要:
Benzyl esters of propiolic and beta-keto acids undergo catalytic decarboxylative coupling when treated with appropriate palladium catalysts. Such decarboxylative couplings allow the benzylation of alkynes without the use of strong bases and/or organometallics. This allows the synthesis of sensitive benzylic alkynes that are prone to undergo isomerizations under basic conditions. Additionally, decarboxylation facilitates the site-specific benzylation of diketones and ketoesters under mild, base-free conditions. Ultimately, the methodology described expands our ability to cross-couple medicinally relevant heterocycles.