Rabina Pradhan

Major: Chemistry

Faculty Advisor: Kris Waynant

Project Title:

Catalytic carboxylation of terminal alkynes with CO2 using copper(I) azothioformamide complexes

Abstract

Carbon dioxide has enormous potential as a C1 building block for organic synthesis due to its non-toxicity and natural abundance. In particular, direct carboxylation of terminal alkynes using carbon dioxide to form propiolic acid has received much attention. Propiolic acids are popular intermediates in synthesis and industries. However, most classic methods to create propiolic acids require harsh reaction conditions or suffer from limited substrate scope. Direct copper(I) catalyzed carboxylation has been a marked improvement in yields and adaptability. A relatively new ligand class, the azothioformamide (ATF) rapidly coordinates with a variety of Cu(I) salts yielding many unique coordination complexes. These complexes were found to act catalytically to effectively transform terminal alkynes to propiolic acids in the presence of base and 1 atm CO2 at 40˚C. Sixteen different ATF-Cu(I) complexes, substrate scope, base, solvent, and temperature were screened for this conversion. The N,N-diethyl-para-methoxyphenyl-azothioformamide Cu(I)I complex with caesium carbonate and dimethyl sulfoxide was found to be most efficient system to produce propiolic acid in good to excellent yield with high functional group tolerance.

Funding: NIH, Idaho INBRE