Organic Synthesis, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
Chemistry. 2013 Jul 29;19(31):10378-87. doi: 10.1002/chem.201204438. Epub 2013 Jun 18.
Transition-metal-catalyzed sp(3) C-H activation has emerged as a powerful approach to functionalize saturated cyclic amines. Our group recently disclosed a direct catalytic arylation reaction of piperidines at the α position to the nitrogen atom. 1-(Pyridin-2-yl)piperidine could be smoothly α-arylated if treated with an arylboronic ester in the presence of a catalytic amount of [Ru3(CO)12] and one equivalent of 3-ethyl-3-pentanol. A systematic study on the substrate and reagent scope of this transformation is disclosed in this paper. The effect of substitution on both the piperidine ring and the arylboronic ester has been investigated. Smaller (pyrrolidine) and larger (azepane) saturated ring systems, as well as benzoannulated derivatives, were found to be compatible substrates with the α-arylation protocol. The successful use of a variety of heteroarylboronic esters as coupling partners further proved the power of this direct functionalization method. Mechanistic studies have allowed for a better understanding of the catalytic cycle of this remarkable transformation featuring an unprecedented direct transmetalation on a Ru(II)-H species.
过渡金属催化的 sp(3) C-H 活化已成为一种强大的方法，用于饱和环状胺的功能化。我们小组最近公开了一种哌啶氮原子α位直接催化芳基化反应。1-(吡啶-2-基)哌啶在[Ru3(CO)12]的催化量和 3-乙基-3-戊醇的一个当量存在下，用芳基硼酸酯处理可以顺利地进行α-芳基化。本文披露了对此转化的底物和试剂范围的系统研究。研究了取代对哌啶环和芳基硼酸酯的影响。较小的（吡咯烷）和较大的（氮杂环庚烷）饱和环系以及苯并稠合衍生物被发现是与α-芳基化方案兼容的底物。各种杂芳基硼酸酯作为偶联试剂的成功使用进一步证明了这种直接功能化方法的强大。机理研究使我们能够更好地理解这种具有前所未有的 Ru(II)-H 物种直接转金属化的非凡转化的催化循环。
