Transition-metal-catalyzed
addition of aryl halides across carbonyls
remains poorly developed, especially for aliphatic aldehydes and hindered
substrate combinations. We report here that simple nickel complexes
of bipyridine and PyBox can catalyze the addition of aryl halides
to both aromatic and aliphatic aldehydes using zinc metal as the reducing
agent. This convenient approach tolerates acidic functional groups
that are not compatible with Grignard reactions, yet sterically hindered
substrates still couple in high yield (33 examples, 70% average yield).
Mechanistic studies show that an arylnickel, and not an arylzinc,
adds efficiently to cyclohexanecarboxaldehyde, but only in the
presence of a Lewis acid co-catalyst (ZnBr
2
).
Although alcohols are one of the largest pools of alkyl substrates, approaches to utilize them in cross-coupling and crosselectrophile coupling are limited. We report the use of 1°and 2°alcohols in cross-electrophile coupling with aryl and vinyl halides to form C(sp 3 )− C(sp 2 ) bonds in a one-pot strategy utilizing a very fast (<1 min) bromination. The reaction's simple benchtop setup and broad scope (42 examples, 56% ± 15% average yield) facilitates use at all scales. The potential in parallel synthesis applications was demonstrated by successfully coupling all combinations of 8 alcohols with 12 aryl cores in a 96-well plate.
Highly efficient transmetalation between gold phosphites and iodopalladium species is presented. In addition to successful transfer of cyclic and acyclic phosphites, studies involving P‐chiral substrates revealed that an initial protodeauration as well as the target transmetalation were both stereospecific, and that the overall process occurred with retention of configuration at phosphorus. Building on the mechanistic work, a catalytic approach to the synthesis of chiral P‐arylated nucleoside derivatives was developed. This chemistry has the potential to be easily adapted for the preparation of a diverse group of P‐chiral species.
SummaryA range of arylgold compounds have been synthesized and investigated as single-component catalysts for the hydrophenoxylation of unactivated internal alkynes. Both carbene and phosphine-ligated compounds were screened as part of this work, and the most efficient catalysts contained either JohnPhos or IPr/SIPr. Phenols bearing either electron-withdrawing or electron-donating groups were efficiently added using these catalysts. No silver salts, acids, or solvents were needed for the catalysis, and either microwave or conventional heating afforded moderate to excellent yields of the vinyl ethers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.