Electroreductive Carbofunctionalization of Alkenes with Alkyl Bromides via a Radical-Polar Crossover Mechanism.

Electrochemistry grants direct access to reactive intermediates (radicals and ions) in a controlled fashion toward selective organic transformations. This feature has been demonstrated in a variety of alkene functionalization reactions, most of which proceed via an anodic oxidation pathway. In this report, we further expand the scope of electrochemistry to the reductive functionalization of alkenes. In particular, the strategic choice of reagents and reaction conditions enabled a radical-polar crossover pathway wherein two distinct electrophiles can be added across an alkene in a highly chemo- and regioselective fashion. Specifically, we used this strategy in the intermolecular carboformylation, anti-Markovnikov hydroalkylation, and carbocarboxylation of alkenes—reactions with rare precedents in the literature—by means of the electroreductive generation of alkyl radical and carbanion intermediates. These reactions employ readily available starting materials (alkyl halides, alkenes, etc.) and simple, transition-metal-free conditions and display broad substrate scope and good tolerance of functional groups. A uniform protocol can be used to achieve all three transformations by simply altering the reaction medium. This development provides a new avenue for constructing Csp3−Csp3 bonds.

电化学以可控的方式直接获取活性中间体（自由基和离子），用于选择性有机转化。这一特性已在多种烯烃官能化反应中得到证实，其中大多数通过阳极氧化途径进行。在本报告中，我们进一步将电化学的应用范围扩展到烯烃的还原官能化。特别是，试剂和反应条件的策略性选择实现了一种自由基 - 极性交叉途径，通过该途径，两种不同的亲电试剂能够以高度化学选择性和区域选择性的方式加成到烯烃上。具体而言，我们通过电还原产生烷基自由基和碳负离子中间体，将该策略应用于烯烃的分子间羰基化、反马氏氢烷基化和碳羧化反应——这些反应在文献中鲜有先例。这些反应使用容易获得的起始原料（烷基卤化物、烯烃等）以及简单的无过渡金属的条件，并且显示出广泛的底物适用范围和对官能团的良好耐受性。只需改变反应介质，就可以使用统一的方案实现所有这三种转化。这一进展为构建Csp3 - Csp3键提供了一条新途径。