The Vilsmeier complexes 3-8 were obtained from the reaction of amide such as N-methylformanilide (NMFA) and N,N-dimethylformamide (DMF) and chloride such as diphosphoryl chloride, phosphorous oxychloride, and oxalyl chloride. The behavior of complexes was clarified by H NMR measurement in a deutrated solvent such as CDCl3, CD2Cl2, CD2ClCD2Cl, CD3CN, THF-d8, and dioxane-d8. Complexes 3 and 4 were converted to DMF or NMFA partially in chlorinated hydrocarbons. On the other hand, complexes 3 and 4 were stable in CD3CN. The reactivity of the Vilsmeier complexes is determined by the reaction of complexes 3-8 with 1,3-dimethoxybenxzene(9) in dry acetonitrile at 70℃ for 3h. The order of reactivity is complex 6> complex 4> complex 3 and complex 5> complex 7 and complex 8.