Density functional theory investigations revealed that the pyridine-boryl radical generated in situ using 4-cyanopyridine and bis(pinacolato)diboron could be used as a bifunctional “reagent”, which serves as not only a pyridine precursor but also a boryl radical. With the unique reactivity of such radicals, 4-substituted pyridine derivatives could be synthesized using α,β-unsaturated ketones and 4-cyanopyridine via a novel radical addition/C—C coupling mechanism. Several controlled experiments were conducted to provide supportive evidence for the proposed mechanism. In addition to enones, the scope could be extended to a wide range of boryl radical acceptors, including various aldehydes and ketones, aryl imines and alkynones. Lastly, this transformation was applied in the late-stage modification of a complicated pharmaceutical molecule.

For the first time, 4-alkyl Hantzsch esters were used to construct molecules with all-carbon quaternary centers by visible light-induced photoredox catalysis via transfer alkylation. Up to a 1500 h–1 turnover frequency was achieved in this reaction. Reactions of 4-alkyl Hantzsch nitriles as tertiary radical donors joined two contiguous all-carbon quaternary centers intermolecularly, and this chemistry was used to synthesize a common precursor of a class of hydroxysteroid dehydrogenase inhibitors.

Hydrodifluoroacetamidation of alkenes with readily available α-bromodifluoroacetamides was achieved by means of a photoreductive reaction catalyzed by the phenyl thiyl radical. A Hantzsch ester was used as the hydrogen donor and electron donor. This photoreductive pathway did not involve the oxidation of a carbon radical intermediate to a carbocation species.Keywords: difluoroacetamidation; Hnatzsch ester; photoreductive; thiyl radical; visible light

The intermolecular direct C–H alkylation of aniline derivatives with α-bromo ketones to build a quaternary carbon center was reported with a visible-light catalysis procedure. The reaction covers a variety of functional groups with good to excellent yields. A regioselectivity favoring the ortho position for the amine group was observed and investigated with Fukui indices and spectral methods.

We report the first example of difluoroalkylation/C–H annulation cascade reactions of cyclopropyl olefins induced by visible-light photoredox catalysis regioselectively affording partially hydrogenated naphthalenes and quinolines with a variety of difluorinated side chains. The alkylation reagent could be extended to monofluoro and trifluoro reagents, nitrile and malonate. The regioselectivity was investigated by means of density functional theory calculations.