Intermolecular Hydroalkoxylation of Terminal Alkynes Catalyzed by a Dipyrrinato Rhodium(I) Complex with Unusual Selectivity

An
operationally simple and atom-economical method for the E-selective preparation of enol ethers is described. A novel
dicarbonyl­(5-phenyldipyrrinato)rhodium complex, 2, was
prepared in four synthetic steps, characterized by X-ray crystallography
and NMR spectroscopy, and then investigated as a catalyst for the
intermolecular hydroalkoxylation of terminal alkynes. Solvent and
substrate studies were used to gain insight into the mechanism of
the reaction. Cyclic voltammetry was also used to investigate the
electronic properties of 2. The rhodium­(I)-catalyzed
intermolecular alkyne hydroalkoxylation reaction reported here mediates
excellent substrate transformation with a high degree of E/Z selectivity which is opposite to that reported
previously using alternative catalysts.