Visible light induced generation of amidyl radical enables functionalization of hydrocarbons

Abstract

1. Ir(III)-Catalyzed Stereoselective Haloamidation of Alkynes Enabled by Ligand Participation In organometallic catalysis, ligand plays a critical role in controlling the steric environment of the catalyst and tuning the electronic structure of the catalyst to drive the reaction toward the desired pathway. Since metal-acylnitrenoid intermediate is well-known for its Curtius-type rearrangement leading to isocyanate, direct formation of a new amide group in hydrocarbon has been thought to be challenging. Described herein is the application of a strategy of ligand participation for the Ir-catalyzed imido transfer into alkynes. It was revealed that the ligand participation suppresses the undesired isocyanation pathway simultaneously to afford synthetically versatile Z-(halovinyl)lactams with excellent stereoselectivity. On the basis of a stoichiometric [3 + 2] cycloaddition of Cp*Ir(III)($\kappa^2 -N$,O-chelate) with alkynyl dioxazolone, a catalytic haloamidation was developed for the first time by employing $[Cp*IrCl_2]_2$ precatalyst and NaX salts (X = Cl or Br) as practical halide sources. 2. Visible Light Induced Generation of Amidyl Radical Enables Functionalization of Hydrocarbons To recent date, the generation and utilization of radical species had required energetically demanding environment. Controlling the highly reactive radical species in an organic reaction has been thought to be even more challenging. By using photocatalyst, however, which absorbs visible light wavelength as the sole energy source, we were able to generate amidyl radical from N-arylroylamide under ambient condition. The resultant participated in a variety of reactions in intra- or intermolecular manner to afford C-H oxygenation, $\delta-lactam$, 1,2-aminoalcohol, and 2-oxazoline product respectively. Furthermore, the intra- and intermolecular reaction pathway were controlled in 2-oxazoline formation reaction depending on the reaction condition. For the intermolecular reaction, The N-aryloylamide was regioselectively added across double bond in atom economic way.