N-Acylation of glycine with carboxylic acids was carried out by using the Vilsmeier reagent. The resulting N-acyl-α-amino acids were subsequently cyclodehydrated into oxazol-5-ones via the Vilsmeier reagent. Finally, treatment of oxazol-5-ones with aldehydes in the presence of the Vilsmeier reagent delivered Erlenmeyer azlactones. By combining these steps, using the Vilsmeier reagent allowed direct one-pot conversion of carboxylic acids into oxazol-5-ones and direct one-pot conversion of carboxylic acids into Erlenmeyer azlactones in the presence of aldehydes. These Vilsmeier reagent-mediated multicomponent reactions proceeded smoothly in reasonable chemical yields at room temperature. The chemical structure of the title compounds was confirmed by spectral data.