Abstract An efficient and three‐step procedure for the synthesis of novel 6,7‐dihydro‐1 H ,4 H ‐pyrazolo[3,4‐ d ][1,3]oxazine derivatives in good to excellent yields by treatment of pyrazolamines with aqueous formaldehyde in the presence of acetic acid is provided. The reactions proceeded through an intramolecular etherification process by dehydration of a 1,5‐diol intermediate formed in the course of the reaction and promoted by acid media.