A new Vilsmeier reagent-mediated one-pot reaction using 5-(2-chloroacetylamino)pyrazoles as the starting material was developed for the efficient synthesis of 6-[(formyloxy)methyl]-1H-pyrazolo[3,4-d]pyrimidine. This new multiple tandem reaction, involving the Vilsmeier–Haack reaction, the Morgan–Walls reaction, sequential elimination, substitution, and final hydrolysis, afforded formyloxymethyl pyrazolo[3,4-d]pyrimidine products in good yields.