C−H Activation for the Construction of C−B Bonds

Totalsynthese von Nosiheptid

“…Basierend auf Literaturbeispielen zur meta-selektiven Borylierung von Pyridinen [283][284][285][286][287] mittels Ir-katalysierter C-H-Aktivierung [288][289][290] Die Ausbeute an Pyridin 233 lag jedoch bei nur 20% über zwei Stufen und bedarf weiterer…”

BCl3‐Induced Annulative Oxo‐ and Thioboration for the Formation of C3‐Borylated Benzofurans and Benzothiophenes

“…Notably these routes are not compatible with some of the functional groups tolerated by BCl 3 ‐induced borylative cyclization (e.g., amide/nitrile groups are generally incompatible with metallation). Furthermore, this methodology is complementary to iridium‐catalyzed C−H borylation which provides C2‐ or C7‐borylated benzofurans 4. Finally, it worth emphasizing that 4 a – h are formed at ambient temperature without a catalyst using inexpensive BCl 3 , in contrast the previous borylative cyclization route to C3‐borylated benzofurans required pre‐installation of the borane (using NaH/CatBCl), Au catalysis, raised temperatures and ≥20 h 15…”

“…The boronic acid derivatives of these heteroaromatics are desirable as they are bench‐stable, have low toxicity and are effective in many functional group transformations, including the ubiquitous Suzuki–Miyaura cross coupling reaction 3. Typically, the formation of these borylated compounds is achieved via the C−H or C−X borylation of the pre‐formed heteroaromatic 3b, 4. An alternative more efficient approach is to form the heteroaromatic scaffold and the C−B bond in one pot via the borylative cyclization of alkynes.…”

“…To demonstrate further that this methodology allows access to otherwise challenging to synthesize boronic acid derivatives 11 d was produced in 55 % isolated yield. Compound 11 d is not readily accessible by established borylation routes commencing from 2‐(thiophen‐3‐yl)benzo[b]thiophene (e.g., Ir‐catalyzed borylation and halogenation/lithiation approaches would all proceed at the thienyl alpha position) 3b, 4…”

meta‐Selective C−H Borylation of Benzylamine‐, Phenethylamine‐, and Phenylpropylamine‐Derived Amides Enabled by a Single Anionic Ligand

“…Perhaps most interesting is the regioselectivity of this process, which is largely controlled by steric considerations 6a, 7. Whilst highly effective for borylation of 1,3‐disubstituted arenes, isomeric mixtures are typically obtained when borylation is applied to monosubstituted and unsymmetrical 1,2‐disubstituted arenes, limiting broader application.…”