| Abstract |
Due to the lability of one of the CO ligands in trans-[Fe(PNP)(CO)(2)Cl](+) this compound is an efficient catalyst for the coupling of a series of aromatic aldehydes with ethyl diazoacetate (EDA), which give, in most cases, selectively 3-hydroxyacrylates rather than beta-oxo esters. This reaction is strongly dependent on the nature of the counterion. Whereas with BF(4)(-) the reaction proceeds with conversions up to 90\%, in the case of the counterions NO(3)(-), CF(3)COO(-), CF(3)SO(3)(-), SbF(6)(-), and BAr (-)(4) [Ar = 3,5-(CF(3))(2)C(6)H(3)] no reaction took place. In the case of PF(6)(-) only up to 20\% conversion was achieved. A conceivable mechanism for the coupling of aromatic aldehydes with EDA was established by means of DFT/B3LYP calculations, which allowed the rationalization of both the chemoselectivity and the role of the counterions. |
