We report anew visible-light-mediated carbonylative amidation of aryl, heteroaryl, and alkyl halides.Atandem catalytic cycle of [Ir(ppy) 2 (dtb-bpy)] + generates ap otent iridium photoreductant through as econd catalytic cycle in the presence of DIPEA, whichp roductively engages aryl bromides,i odides,a nd even chlorides as well as primary, secondary,a nd tertiary alkyli odides.T he versatile in situ generated catalyst is compatible with aliphatic and aromatic amines,shows high functional-group tolerance,and enables the late-stage amidation of complex natural products.

Photolysis of 1 in argon-saturated acetonitrile yields 2, whereas in oxygen-saturated acetonitrile small amounts of benzoic acid and benzamide are formed in addition to 2. Similarly, photolysis of 2 in argon-saturated acetonitrile results in 1 and a trace amount of 3, whereas in oxygen-saturated acetonitrile the major product is 1 in addition to the formation of small amounts of benzoic acid and benzamide. Laser flash photolysis of 1 results in an absorption due to triplet vinylnitrene 4 (broad absorption with λ(max) at 360 nm, τ = 1.8 μs, acetonitrile) that is formed with a rate constant of 1.2 × 10(7) s(-1) and decays with a rate constant of 5.6 × 10(5) s(-1). Laser flash photolysis of 2 in argon-saturated acetonitrile likewise results in the formation of triplet vinylnitrene 4 but also ylide 5 (λ(max) at 440 nm, τ = 13 μs). The rate constant for forming 4 in argon-saturated acetonitrile is 1.6 × 10(7) s(-1). In oxygen-saturated acetonitrile, vinylnitrene 4 reacts to form the peroxide radical 6 (λ(max) 360 nm, ~0.7 μs, acetonitrile) at a rate of 2 × 10(9) M(-1) s(-1). Density functional theory calculations were performed to aid in the characterization of vinylnitrene 4 and peroxide 6 and to support the proposed mechanism for the formation of these intermediates.

Photolysis of 3-methyl-2-phenyl-2H-azirine (1a) in argon-saturated acetonitrile does not yield any new products, whereas photolysis in oxygen-saturated acetonitrile yields benzaldehyde (2) by interception of vinylnitrene 5 with oxygen. Similarly, photolysis of 1a in the presence of bromoform allows the trapping of vinylnitrene 5, leading to the formation of 1-bromo-1-phenylpropan-2-one (4). Laser flash photolysis of 1a in argon-saturated acetonitrile (λ = 308 nm) results in a transient absorption with λ(max) at ~440 nm due to the formation of triplet vinylnitrene 5. Likewise, irradiation of 1a in cryogenic argon matrixes through a Pyrex filter results in the formation of ketene imine 11, presumably through vinylnitrene 5. In contrast, photolysis of 2-methyl-3-phenyl-2H-azirine (1b) in acetonitrile yields heterocycles 6 and 7. Laser flash photolysis of 1b in acetonitrile shows a transient absorption with a maximum at 320 nm due to the formation of ylide 8, which has a lifetime on the order of several milliseconds. Similarly, photolysis of 1b in cryogenic argon matrixes results in ylide 8. Density functional theory calculations were performed to support the proposed mechanism for the photoreactivity of 1a and 1b and to aid in the characterization of the intermediates formed upon irradiation.

The general catalytic synthesis of aryl and vinyl thioethers from readily available halides remains a challenge. Herein we report a unified method for the thiolation of aryl and vinyl iodides with dialkyl disulfides using visible light photoredox catalysis. A range of thioether products bearing diverse functional groups can be accessed in high yield and with excellent chemoselectivity. We demonstrate the versatility of this method through the expedient synthesis of a family of thioether-rich natural products. A detailed investigation of the photocatalytic mechanism is presented from both steady-state and time-resolved luminescent quenching as well as transient absorption spectroscopy experiments.