Substituted 4-arylamino-1,3-dioxanes were synthesized using a new synthetic protocol of the Prins reaction between aryl amines and acetaldehyde. This one-pot synthesis occurs under catalyst-free conditions in an aqueous medium. By employing condensation of excess acetaldehyde with an aromatic amine in water at 0–5 °C, the corresponding N-aryl-2,6-dimethyl-1,3-dioxan-4-amines are obtained in good yields. Consequently, this is an environmentally benign, simple, efficient, “green” procedure for the preparation of 1,3-dioxanes.