The oxidative coupling between benzaldehyde derivatives and phenylacetylene catalyzed by rhodium complexes via C-H bond activation

Abstract

This paper reports the use of rhodium (Rh) catalysts for the oxidative coupling reaction between phenylacetylene and benzaldehyde derivatives via C-H bond activation. These reactions were catalyzed by Rh(l-amino acid)(cod) (the l-amino acid is l-phenylalanine, l-valine or l-proline; cod is 1,5-cyclooctadiene) to obtain chromones in 12.7-88.3% yield. These new Rh catalysts have excellent activity for the coupling reaction between phenylacetylene and different benzaldehyde derivatives. It was found that the electronic effects of the benzaldehyde derivative substituent affected the reaction yield, which is in accordance with the proposed mechanism.

Rh(I) Complexes in Catalysis: A Five-Year Trend

“…For instance, L-phenylalanine, L-valine, and Lproline were introduced as anionic ligands in Rh-COD compounds to give chiral complexes for the oxidative coupling reaction between phenylacetylene and benzaldehyde derivatives, producing seven types of chromones via C-H bond activation. Yields were variable, comprised between about 13-88%, depending on the electronic nature of the substituents on the benzaldehyde derivatives [80]. Moreover, it was found that when the amino acid was L-phenylalanine with its large aromatic moiety, it could easily dissociate from the metal centre to leave an empty active site, thus increasing the catalytic activity of the Rh complex.…”