The enantioselective functionalization of ubiquitous C(sp3)âH bonds is ideally suited for the construction of three-dimensional chiral structures. However, organic molecules often contain multiple C(sp3)âH bonds with a similar energy and steric environment, rendering the simultaneous control of site-, chemo- and stereoselectivity extremely challenging. Here we show the merger of molecular photoelectrochemistry with asymmetric catalysis for the highly site- and enantioselective cyanation of benzylic C(sp3)âH bonds. This example of photoelectrochemical asymmetric catalysis requires no chemical oxidant and exhibits an exceptional level of site selectivity and functional group tolerance, enabling not only the efficient conversion of feedstock chemicals but also the late-stage functionalization of complex bioactive molecules and natural products, including ones with multiple benzylic sites. Asymmetric synthetic photoelectrochemical transformations are underdeveloped. Now, the combination of a photocatalyst, a chiral copper catalyst and an electrode allows the enantioselective cyanation of benzylic CâH bonds without a chemical oxidant.
Remote C−H Pyridylation of Hydroxamates through Direct Photoexcitation of
<i>O</i>
‐Aryl Oxime Pyridinium Intermediates
作者:Byeongseok Kweon、Changha Kim、Seonyul Kim、Sungwoo Hong
DOI:10.1002/anie.202112364
日期:2021.12.13
designing a new class of photon-absorbing O-aryl oxime pyridinium salts generated in situ from the corresponding pyridines and hydroxamates. This method involves photolytic N−O bond cleavage through the photoexcitation of oxime pyridiniumintermediates to generate iminyl radicals, which enable the installation of pyridyl rings at the γ-CN position in complex settings under mild and metal-free conditions.