Nickel-Catalyzed Cross-Electrophile Coupling of Aryl Triflates with Alkyl Halides: Mechanism-Informed Design of More General Conditions.

Aryl triflates make up a class of aryl electrophiles that are available in a single step from the corresponding phenol. Despite the known reactivity of nickel complexes for aryl C-O bond activation of phenol derivatives, nickel-catalyzed cross-electrophile coupling using aryl triflates has proven challenging. Herein, we report a method to form C(sp)-C(sp) bonds by coupling aryl triflates with alkyl bromides and chlorides using phenanthroline (phen) or pyridine-2,6-bis(-cyanocarboxamidine) (PyBCam)-ligated nickel catalysts.

Control of Redox-Active Ester Reactivity Enables a General Cross-Electrophile Approach to Access Arylated Strained Rings.

Strained rings are increasingly important for the design of pharmaceutical candidates, but cross-coupling of strained rings remains challenging. An attractive, but underdeveloped, approach to diverse functionalized carbocyclic and heterocyclic frameworks containing all-carbon quaternary centers is the coupling of abundant strained-ring carboxylic acids with abundant aryl halides. Herein we disclose the development of a nickel-catalyzed cross-electrophile approach that couples a variety of strained ring N-hydroxyphthalimide (NHP) esters, derived from the carboxylic acid in one step, with various aryl and heteroaryl halides under reductive conditions.

In-Situ Bromination Enables Formal Cross-Electrophile Coupling of Alcohols with Aryl and Alkenyl Halides.

Although alcohols are one of the largest pools of alkyl substrates, approaches to utilize them in cross-coupling and cross-electrophile 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)-C(sp) 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% ave yield) facilitates use at all scales.

The Mechanism of Rhodium-Catalyzed Allylic C-H Amination.

Herein, the mechanism of catalytic allylic C-H amination reactions promoted by Cp*Rh complexes is reported. Reaction kinetics experiments, stoichiometric studies, and DFT calculations demonstrate that the allylic C-H activation to generate a Cp*Rh(π-allyl) complex is viable under mild reaction conditions. The role of external oxidants in the catalytic cycle is elucidated.