Black, Mercedes S., Talia M. Fanelli, Witold K. Fuchs, Sara B. Kuhn, Sai Nimmagadda, and Matthew J. Mio
Sonogashira coupling reactions have been modified to include the insertion of carbon monoxide at the junction of the aryl ring and acetylene functional groups. In situ removal of the terminal silylacetylene protecting group allows for further, one-pot difunctionalization. Key to the protocol is the inclusion of a mixture of two nitrogenous bases: triethylamine and amidines, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). Under balloon pressure of CO, the triethylamine base aids in the carbonyl insertion, while the amidine affects the in situ silylacetylene deprotection. Substoichiometric amounts of water, in addition to Pd catalyst, CuI and organic solvent are also required for these transformations to proceed.