Copper-Catalyzed Dehydrogenative Cross-Coupling Reactions of N-para-Tolylamides through Successive CH Activation: Synthesis of 4H-3,1-Benzoxazines

Copper-Catalyzed Enantioconvergent Cross-Coupling of Racemic Alkyl Bromides with Azole C(sp2 )-H Bonds

The development of enantioconvergent cross-coupling of racemic alkyl halides directly with heteroarene C(sp² )-H bonds has been impeded by the use of a base at elevated temperature that leads to racemization. We herein report a copper(I)/cinchona-alkaloid-derived N,N,P-ligand catalytic system that enables oxidative addition with racemic alkyl bromides under mild conditions. Thus, coupling with azole C(sp² )-H bonds has been achieved in high enantioselectivity, affording a number of potentially useful α-chiral alkylated azoles, such as 1,3,4-oxadiazoles, oxazoles, and benzo[d]oxazoles as well as 1,3,4-triazoles, for drug discovery. Mechanistic experiments indicated facile deprotonation of an azole C(sp² )-H bond and the involvement of alkyl radical species under the reaction conditions.

Copper-catalyzed aromatic C-H alkoxylation with alcohols under aerobic conditions

An efficient protocol for copper-catalyzed aromatic C-H alkoxylation with alcohols has been developed under aerobic conditions. The protocol provides a complementary method to couple arenes and alcohols to furnish aromatic ethers. The advantages of this method are the employment of a cheap Cu(OAc)₂ catalyst, oxygen as the terminal oxidant and alcohol as both an alkoxy reagent and a solvent. Notably, the catalytic amount of benzoic acid plays a significant role in this transformation.