Two series of sterically encumbered gold(I)-acyclic diaminocarbene (ADC) complexes were prepared by reaction of mono-and dialkylamines with gold-bound 2-mesitylphenyl isocyanide (monomesityl series) and 2,6-dimesitylphenyl isocyanide (dimesityl series). X-ray crystal structures and solution 1 H NMR data showed that the ADC-gold complexes adopt major rotameric conformations with the bulky biaryl/terphenyl group and one alkyl group located syn to gold. This engenders substantial steric hindrance at the metal, as evidenced by percent buried volume (%V bur ) parameters of 35.7 -37.2 for the monomesityl series and 46.4 -52.4 for the dimesityl series. Modest out-of-plane distortions of the ADC N-substituents in the dimesityl series were attributed to attractive CH•••π interactions between alkyl groups and mesityl rings on the basis of dispersion-corrected density functional theory calculations. Gold-catalyzed regiodivergent domino cyclization/hydroarylation reactions of a 1,6-enyne with indole revealed that the bulky biaryl/terphenyl substituents of the ligands exert a strong influence on product selectivity, with the bulkier dimesityl ADC-Au catalysts inducing a shift away from the cyclopropane-fused product toward the normally disfavored alkene product. Incorporation of a yet bulkier bis(2,6-diisopropylphenyl)-substituted terphenyl moiety into the ADC led to a gold catalyst that provided exclusive selectivity for the alkene product. Computational modeling suggested that bulky terphenyl groups hinder attack at the a carbon in the initially formed organogold intermediate, allowing steric effects to override the intrinsic electronic preference for the cyclopropane product. File list (3) download file view on ChemRxiv Slaughter_Encumbered_ADC-Au_Preprint.pdf (2.05 MiB) download file view on ChemRxiv Slaughter_Encumbered_ADC-Au_SuppInfo_Preprint.pdf (4.44 MiB)

Gold(i) catalyzes domino homodimerization of o-alkynylbenzaldehydes via a sequence of 6-endo-dig-cyclization, amine addition, and [4+2] cycloaddition involving two bicyclic intermediates. The resulting products integrate medicinally relevant 1,2-dihydronaphthalene and isochromene moieties into a single amine-substituted tetracyclic framework.

A Pd(OAc)2/xantphos catalyst system was found effective for benzylaminations of binaphthyl 2-triflates bearing a variety of alkyl, benzyl, and substituted phenyl substituents at the 2'-position. With 2'-aryl substituents, an intramolecular Pd-catalyzed C-H arylation was observed as a competing side reaction under some conditions. By adjusting the solvent and quantity of the amine, the reaction was optimized to favor either the amination or the C-H arylation pathway, affording two distinct and potentially useful sets of products. The amines represent tunable chiral ligand precursors, while the C-H arylation pathway affords a series of benzofused [5]helicene derivatives. Kinetic studies and activation parameters for the C-H arylation pathway, supported by DFT calculations, are consistent with a concerted metalation-deprotonation (CMD) mechanism involving a Pd-bound carbonate as the base. Xantphos is proposed to facilitate the turnover-limiting inner-sphere CMD step by acting as a hemilabile ligand, while its wide bite angle engenders a low reductive elimination barrier.