Synthesis of Rhodium and Ruthenium Pi-Complexes with Pendant Amide Substituents for Intramolecular Proton Transfer upon Activation of C–H Bonds

Abstract

Cyclopentadienyl and arene complexes with pendant amide substituents [(C₅Me₄CH₂CH₂NHR)RhCl₂]_n and [(C₆H₅CH₂CH₂NHR)RuCl₂]_n (R = COCF₃, Ts) were synthesized by heating the corresponding dienes with metal chlorides. They were tested as catalysts for the annulation of N-methoxy-p-methylbenzamide with alkynes. Contrary to our expectations, the pendant amide groups did not act as internal proton acceptors and did not accelerate the C–H activation process. However, it was found that the reaction of N-methoxy-p-methylbenzamide with 4-octyne in the presence of various rhodium complexes produced an O-methyl oxime of isocoumarin instead of the expected isoquinolone as the major product.