Low‐valent Cobalt Complexes in C–X Coupling and Related Reactions

Cobalt-Catalyzed C(sp2)–CN Bond Activation: Cross-Electrophile Coupling for Biaryl Formation and Mechanistic Insight

“…With the optimized conditions in hand, we then investigated the scope of the title transformation (Table ). The reaction works in accordance with most cross-electrophile couplings catalyzed by cobalt previously reported ,,, and is highly sensitive to the electronic properties of the substrates, sometimes necessitating tuning of the coupling partners to induce cross-selectivity. It should be pointed out that the superior reactivity of aryl iodides compared to that of aryl cyanides mainly led to the homocoupling products of the aryl iodide substrates instead of cross-coupling products.…”

“…Cobalt complexes have already shown to be efficient catalysts to perform cross-electrophile coupling reactions. ,, Moreover, we and others have revealed the great ability of cobalt complexes to perform cross-coupling reactions of partners other than halide derivatives . Therefore, as part of our continuous effort to develop efficient couplings from more stable and available halide surrogates, we disclose herein an attractive cobalt-catalyzed intermolecular cross-electrophile coupling to form biaryls from benzonitrile derivatives under mild conditions (Scheme d).…”

Cobalt-Catalyzed Enantiospecific Dynamic Kinetic Cross-Electrophile Vinylation of Allylic Alcohols with Vinyl Triflates

“…We then focused on cobalt, 18 which has also found promising applications in cross-electrophile coupling. 19 After numerous trials, we determined that a combination of Co(acac) 3 , ligand L8, Mn, and additives (MgBr 2 , BiCl 3 , and 4 Å MS) in DMF at −40 °C gave the best result; the reaction afforded 3a in 80% isolated yield with a nearly exclusive inversion of configuration (Table 1, entry 1). Comparable results were obtained when CoBr 2 or CoCl 2 was used (entries 2 and 3).…”

“…Our initial studies started with the reaction of alcohol 1a and triflate 2a and DMO using nickel catalysis but were fairly unsuccessful; the reactions generally gave only a trace of 3a or none. We then focused on cobalt, which has also found promising applications in cross-electrophile coupling . After numerous trials, we determined that a combination of Co­(acac) 3 , ligand L8 , Mn, and additives (MgBr 2 , BiCl 3 , and 4 Å MS) in DMF at −40 °C gave the best result; the reaction afforded 3a in 80% isolated yield with a nearly exclusive inversion of configuration (Table , entry 1).…”

Cobalt-catalyzed cross-coupling of Umpolung carbonyls with alkyl halides under mild conditions

“…Since then, great progress has been made in cobalt-catalyzed C–C cross-coupling reactions, including arylation, alkenylation and alkylation of alkyl halides. 3 b ,9 In general, cobalt catalysis features mild reaction conditions, high functional-group compatibility, and broad availability of cobalt halide pre-catalysts, all of which have contributed to the growing success in this field. In view of the advantages of cobalt, we postulated that cross-coupling of hydrazones with alkyl halides can also be catalyzed by cobalt, which will open new avenues for other kinds of cobalt-catalyzed reactions involving Umpolung hydrazone chemistry.…”