Regioselective Synthesis of Emission Color‐Tunable Pyrazolo[1,5‐a]pyrimidines with β,β‐Difluoro Peroxides as 1,3‐Bis‐Electrophiles

Abstract

The synthesis and photophysical properties of fluorescent pyrazolo[1,5‐a]pyrimidines (PPs) are explored. An array of 5,7‐disubstituted fluorescent PPs are prepared selectively by using β,β‐difluoro peroxides as the 1,3‐bis‐electrophiles. The synthesized PPs display a fairly significant stokes shift (up to 211 nm) and a large window of tunable emission wavelength that covers most of the visible spectrum (400 nm to 800 nm). Theoretical calculation indicates that the distinguished variation of intramolecular charge transfer (ICT) ability upon the varied substituents is responsible for the color‐tunable fluorescence emission.

Multiple-fold C–F bond functionalization for the synthesis of (hetero)cyclic compounds: fluorine as a detachable chemical handle

“…After this disclosure, the same strategy could be applied in the functionalization of 5-amino-1 H -pyrazoles by manipulating β,β-difluoro peroxides as 1,3-biselectrophiles, which further broadens its practicability and generality (Scheme 30). 60 Excitingly, a multitude of multi-functionalized fluorescent pyrazolo [1,5- a ] pyrimidines exhibited a large Stokes shift (up to 211 nm) and a large window of tunable emission wavelength. In these structures, the electron-withdrawing character of the pyrazolo [1,5- a ]pyrimidine rings was particularly reinforced by perfluoroalkyl or carbonyl substituents.…”