Mechanism of Cu-Catalyzed Iododeboronation: A Description of Ligand-Enabled Transmetalation, Disproportionation, and Turnover in Cu-Mediated Oxidative Coupling Reactions

Ecofriendly Protocol for ipso-Bromination of Arylboronic Acids

We report a novel and environmentally friendly method for the ipso-bromination of arylboronic acids by exploiting the oxone/KBr system. We discovered that CuBr can catalyze the reaction and increase the yield from 63 to 97%. We believe that CuBr might catalyze the in situ generation of HOBr from oxone/KBr. The mild reaction condition permits tolerance of a diverse array of functional groups with exclusive regio- and chemoselectivity and allows low-cost large-scale reaction without explosion risk.

Ligand-Enabled Copper-Mediated Radioiodination of Arenes

The discovery of a copper precatalyst that facilitates the key mechanistic steps of arene halodeboronation has allowed a step change in the synthesis of radioiodine-containing arenes. The active precatalyst [Cu(OAc)(phen)2]OAc was shown to perform room temperature radio-iododeboronation of aryl boronic acids with 1-2 mol % loadings and 10 min reaction times. These mild conditions enable particularly clean reactions, as demonstrated with the efficient preparation of the radiopharmaceutical and SPECT tracer, meta-iodobenzylguanidine (MIBG).

One-pot two-step radioiodination based on copper-mediated iododeboronation and azide-alkyne cycloaddition reaction

This methodology demonstrates the ability to sequentially regulate copper-mediated radioiododeboronation and an azide-alkyne cycloaddition reaction, which facilitates the continuous incorporation of reagents into the reaction system and mediates the integration of the purification steps into the final process. Additionally, this reaction is suited to be conducted under mild conditions and yields target compounds through potent radiochemical conversions.

Mechanistic Avenues in the Chan-Lam-Based Etherification Reaction: A Computational Exploration

Ongoing advances in CuII -catalyzed aerobic oxidative coupling reactions between arylboronic esters and diverse heteroatom nucleophiles have strengthened the development of the general Chan-Lam (CL)-based reaction protocol, including C-O bond formation methodologies. In-depth mechanistic understanding of CL etherification with specific emphasis on different reaction routes and their energetics are still lacking, even though the reaction has been experimentally explored. Here, we present a DFT-guided computational study to unravel the mechanistic pathways of CL-based etherification. The computational findings provide some interesting insights into the fundamental steps of the catalytic cycle, particularly the rate-determining transmetalation event. An aryl boronic ester-coordinated, methoxide-bridged CuII intermediate that acts as resting state undergoes transmetalation with an activation barrier of 20.4 kcal mol-1 . The energy spans of the remaining fundamental steps leading to the methoxylated product are relatively low. The minor p-cresol product requires an additional 14.2 kcal mol-1 energy span to surmount in comparison to the favored route. Hammett studies for the substituted aryl boronic esters reveal higher reaction turnovers for electron-rich aryl systems. The results agree with previously reported spectroscopic and kinetic observations. For a series of alcohol substrates, it was observed that, except for cyclohexanol, moderate to high etherification turnovers are predicted.

An Asymmetric Aromatic Finkelstein Reaction: A Platform for Remote Diarylmethane Desymmetrization

A first-of-its-kind enantioselective aromatic Finkelstein reaction is disclosed for the remote desymmetrization of diarylmethanes. The reaction operates through a copper-catalyzed C-I bond-forming event, and high levels of enantioselectivity are achieved through the deployment of a tailored guanidinylated peptide ligand. Strategic use of transition-metal-mediated reactions enables the chemoselective modification of the aryl iodide products; thus, the synthesis of a diverse set of otherwise difficult-to-access diarylmethanes with excellent levels of selectivity is realized from a common intermediate. A mixed experimental/computational analysis of steric parameters and substrate conformations identifies the importance of remote conformational effects as a key to achieving high enantioselectivity in this desymmetrization reaction.