Electrochemistry-Enabled Ir-Catalyzed Vinylic C–H Functionalization

Synergistic use of electrochemistry and organometallic
catalysis
has emerged as a powerful tool for site-selective C–H functionalization,
yet this type of transformation has thus far mainly been limited to
arene C–H functionalization. Herein, we report the development
of electrochemical vinylic C–H functionalization of acrylic
acids with alkynes. In this reaction an iridium catalyst enables C–H/O–H
functionalization for alkyne annulation, affording α-pyrones
with good to excellent yields in an undivided cell. Preliminary mechanistic
studies show that anodic oxidation is crucial for releasing the product
and regeneration of an Ir­(III) intermediate from a diene-Ir­(I) complex,
which is a coordinatively saturated, 18-electron complex. Importantly,
common chemical oxidants such as Ag­(I) or Cu­(II) did not give significant
amounts of the desired product in the absence of electrical current
under otherwise identical conditions.

电化学与有机金属催化的协同应用，已成为实现位点选择性C-H官能化的有力工具，然而此类转化迄今仍主要局限于芳烃C-H官能化领域。于此，我们报道了丙烯酸与炔烃的电化学乙烯基C-H官能化反应。该反应中，铱催化剂可介导C-H/O-H官能化以实现炔烃环化，在无分隔电解池中以良好至优异的收率得到α-吡喃酮类化合物。初步机理研究表明，阳极氧化对于产物释放以及从二烯-铱(I)配合物（一种配位饱和的18电子配合物）中再生铱(III)中间体至关重要。值得注意的是，在其他条件完全一致且无电流通入的情况下，常见的化学氧化剂如银(I)或铜(II)无法得到可观量的目标产物。