The synthesis of organoboron compounds is of contemporary importance in the chemistry community given their utility in subsequent functionalization reactions as well as their growing therapeutic potential in the treatment of human disease. Recently, our lab developed a catalytic reaction which uses CO2, a highly sustainable feedstock, and B2(pin)2 (pin = pinacolato: 2,3-dimethyl-2,3-butanediolate) to difunctionalize alkenes regioselectively to generate several carboxylic acid derivatives with an ICyCuCl precatalyst (ICy = (1,3-dicyclohexyl)imidazol-2-ylidene). A subsequent publication detailed the addition of PPh3 as a secondary ligand, which allowed access to substituted styrenes that were previously not amenable to our original catalytic conditions. A desire to understand the mechanism by which these transformations occur has led to an extensive experimental and computational analysis. IPrCu(I) complexes (IPr = 1,3-didiisopropylphenyl)imidazol-2-ylidene) analogous to those proposed in the catalytic cycle were synthesized and characterized through X-Ray crystallography and several spectroscopic techniques. The rates of carboxylation of the Cu(I)-alkyl-β-boryl complex, proposed to be the rate determining step, was also studied, employing a variety of para-substituted styrene derivatives. Results indicated competing mechanisms when exposing electron-rich versus electron-deficient aryl complexes to carboxylation. Addition of PPh3 and its effect on the catalytic mechanism were also considered. Complementary computational studies were also conducted, exploring the electronic effects of both the para substituents for vinyl arenes and the boron fragment on rate-determining CO2 insertion. Varying the para substituents in silico produces results consistent with those obtained experimentally; furthermore, introducing PPh3 leads to an SEn-type mechanism rather than direct insertion. The effect of the boron was explored by selecting fragments (BX2) with varying electronegativities and considering the energetic impacts on carboxylation. Results revealed that increasing electron deficiency at boron leads to more energetically accessible CO2 insertion. This relationship suggests that boron facilitates this step to a certain degree through a Lewis acid/base interaction.

Mechanistic analysis of Cu(I)-catalyzed boracarboxylation of vinyl arenes

Macromolecular Chemistry: The Second Century

[Author Benefits](https://scimeetings.acs.org/?utm_source=pubs_content_marketing&utm_medium=website&utm_campaign=0320_MCF_NPI_Launch_Spring_Homepage&ref=pubs_content_marketing)

[How to use SciMeetings](https://storage.googleapis.com/dl.morressier.com/acs/SciMeetings-ACSSpring2020-HowToGuide_M3020-Final.pdf)

[Frequently Asked Questions](https://storage.googleapis.com/dl.morressier.com/acs/SciMtng_ACSNMSp2020_FAQ_M3120_Final.pdf)

ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.