Tunable regioselective synthesis of pyrazolo[3,4-d]pyrimidine derivatives via aza-Wittig cyclization and dimroth-type rearrangement

A novel tunable regioselective synthesis of pyrazolo[3,4-d]pyrimidine derivatives via aza-Wittig/Ag(I) or base-promoted tandem reaction has been developed. This approach provides a simple and efficient way to construct pyrazolo[3,4-d]-pyrimidine derivatives under mild conditions.