A highly efficient, simple and versatile acid catalyst is proposed for the selective dehydration of 1-phenylethan-1,2-diol to the phenylacetaldehyde as an industrial platform molecule. For the first time, common Lewis acids AlCl3 and FeCl3 and mineral acids HCl and H2SO4 had produced the acetaldehyde derivative under microwave irradiation in sub-critical water in good yield starting from the corresponding diol.