In the presence of Lewisacid, such as SbCl5, SbCl6·NAr3 or Cu(OTf)2, difluorovinyl methylether (1,1-difluoro-2-methoxy-1-alkene) 1 reacted with carbonyl compounds to give O-methylated aldol-type products 3 in good yields, while Lewisacid, such as TMSOTf, TiCl4 or BF3·Et2O, did not work in these reactions. On the other hand, TMSOTf was found an effective catalyst for the reaction of 1 with carbonyl