Metals in organic syntheses : V. The gattermann-koch synthesis of aromatic aldehydes promoted by CuCl(PPh 3) n ( n = 0, 1 or 3). Is the cuprous complex necessary in the synthesis of tolualdehyde?

Abstract

The use of CuCl(PPh 3) in place of CuCl in the Gattermann-Koch synthesis slightly improves the yield of benzaldehyde but lowers the yield of tolualdehyde. The poorest yields are obtained in the presence of CuCl(PPh 3) 3. The formation of tolualdehyde from toluence and carbon monoxide in the presence of AlCl 3 and HCl is faster in the presence of CuCl, but higher yields are obtained in its absence and using an excess of hydrocarbon. In competitive experiments carried out using benzene and toluene together in equimolecular amounts, only tolualdehyde was formed, supporting the view that an electrophilic substitution is involved.