We report a catalytic method to access secondary alcohols by the coupling of aryl iodides. Either aldehydes or alcohols can be used as reaction partners, making the transformation reductive or redox-neutral, respectively. The reaction is mediated by a Ni catalyst and a 1,5-diaza-3,7-diphospha­cyclooctane. This P2N2 ligand, which has previously been unrecognized in cross-coupling and related reactions, was found to avoid deleterious aryl halide reduction pathways that dominate with more traditional phosphines and NHCs. An interrupted carbonyl-Heck type mechanism is proposed to be operative, with a key 1,2-insertion step forging the new C–C bond and forming a nickel alkoxide that may be turned over by an alcohol reductant. The same catalyst was also found to enable synthesis of ketone products from either aldehydes or alcohols, demonstrating control over the oxidation state of both the starting materials and products.

Upon UVA irradiation, aryl halides can undergo dehalogenation in presence of bases and methanol as a hydrogen donor. This catalyst-free photochemical dehalogenation is furnished through a facile radical-chain reaction under mild conditions. The chain reaction follows UVA irradiation of the reaction mixture in a transition metal-free environment. Mechanistic studies support a chain mechanism in which initiation involves absorption by a methoxide-bromoarene complex facilitated by halogen bonding interactions. The methoxide-bromine interaction leads to a weakened Br-C bond that is prone to facile cleavage during the initiation and propagation steps.

We report an intermolecular Ni-catalyzed reductive coupling of aryl iodides and isatins to form 3-hydroxyoxindoles. In contrast to common metal-mediated methods, sec-butanol is used as a mild stoichiometric reductant resulting in benign waste products. This formal 1,2-addition reaction is facilitated by a 1,5-diaza-3,7diphosphacyclooctane (P 2 N 2 ) ligand. Two Ni(0)−P 2 N 2 species are prepared and found to be catalytically active, supporting a mechanistic hypothesis that this reaction proceeds by a modified carbonyl-Heck-type pathway.