Abstract：
We describe a unique catalytic system with an efficient coupling of Ti- and Cr-catalysis in a reaction network that allows the use of [BH4 ]- as stoichiometric hydrogen atom and electron donor in catalytic radical chemistry. The key feature is a relay hydrogen atom transfer from [BH4 ]- to Cr generating the active catalysts under mild conditions. This enables epoxide reductions, regiodivergent epoxide opening and radical cyclizations that are not possible with cooperative catalysis with radicals or by epoxide reductions via Meinwald rearrangement and ensuing carbonyl reduction. No typical SN 2-type reactivity of [BH4 ]- salts is observed.
摘要：
我们描述了一种独特的催化体系，该体系在反应网络中具有Ti和Cr催化剂的有效偶联，该反应网络允许使用[BH4]-作为催化自由基化学中的化学计量氢原子和电子供体。关键特征是在温和条件下从[BH4]-到Cr的中继氢原子转移产生活性催化剂。这使得环氧化物减少，区域相反的环氧化物开放和自由基环化，这与自由基的协同催化或通过Meinwald重排和随后的羰基还原的环氧化物还原是不可能的。没有观察到[BH4]-盐的典型SN2型反应性。
