A Convenient Approach to meso -Uracil-4,4-Difluoro-4-bora-3a, 4a-diaza- s -indacene Derivatives

An effective and convenient protocol for the synthesis of 1-substituted uracil-6-carbaldehyde derivatives has been developed. A three-step sequence permits the preparation of uracil-6-carbaldehydes with various substituents at the N-1 in large quantities by using low-cost precursors. The aldehyde-functionalized uracils served as useful precursors for the preparation of meso-(1-substituted 6-uracil)-derivatives of 4,4-difluoro-4-bora-3a,4a-diaza- s -indacene (BODIPY). In this way, regioselectively functionalized BODIPYs with a direct connection to a nucleobase were prepared in yields of 30-45%. MALDI-TOF mass spectrometry, NMR, UV/vis absorption, and steady-state and time-resolved fluorescence spectroscopies were used to characterize the structures and the spectroscopic/photophysical properties of the resultant dyes.