Department of Chemistry, York University, 4700 Keele Street, Toronto, Ontario, M3J1P3 (Canada).
Lilly Research Laboratories, Indianapolis, IN 46285 (USA).
Angew Chem Int Ed Engl. 2015 Aug 10;54(33):9502-6. doi: 10.1002/anie.201503941. Epub 2015 Jun 25.
The ability to cross-couple secondary alkyl centers is fraught with a number of problems, including difficult reductive elimination, which often leads to β-hydride elimination. Whereas catalysts have been reported that provide decent selectivity for the expected (non-rearranged) cross-coupled product with aryl or heteroaryl oxidative-addition partners, none have shown reliable selectivity with five-membered-ring heterocycles. In this report, a new, rationally designed catalyst, Pd-PEPPSI-IHept(Cl), is demonstrated to be effective in selective cross-coupling reactions with secondary alkyl reagents across an impressive variety of furans, thiophenes, and benzo-fused derivatives (e.g., indoles, benzofurans), in most instances producing clean products with minimal, if any, migratory insertion for the first time.
交叉偶联二级烷基中心存在许多问题，包括难以进行还原消除，这往往会导致β-氢消除。虽然已经报道了一些催化剂，它们可以为与芳基或杂芳基氧化加成伙伴的预期（非重排）交叉偶联产物提供相当好的选择性，但没有一种催化剂在与五元杂环的反应中表现出可靠的选择性。在本报告中，一种新的、经过合理设计的催化剂 Pd-PEPPSI-IHept(Cl)，被证明在与各种呋喃、噻吩和苯并稠合衍生物（如吲哚、苯并呋喃）的二级烷基试剂的选择性交叉偶联反应中非常有效，在大多数情况下，首次以最小的、如果有的话，迁移插入，生成干净的产物。
