Visible-Light-Driven (NSNO)Nickel complex catalyzed (Z)-Selective semi-hydrogenation of alkynes

Abstract

We reported that a new type of nickel catalysts, in combination with use of as a 2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN) as a photoinitiator, are capable of affecting (Z)-selective semi-hydrogenation of alkynes utilizing carbonic acid, in-situ generation by the reaction of carbon dioxide and water, and Et₃N as a hydrogen source under mild photochemical conditions. This catalytic system allows wide scopes of alkynes, including aryl internal alkynes, mono-alkylacetylene, and aryl terminal alkynes, affording (Z)-alkenes as major product in good to excellent yields. It is noteworthy that N-heteroaromatic internal alkynes, such as 2-pyridyl arylenyne, yield (E)-alkenes. The cooperative catalysis between nickel complexes and 4CzIPN was revealed by in situ infrared spectroscopy, high-resolution mass spectrometry (HRMS), and control experiments.