Synthesis of 8-substituted 4, 4-difluoro-4-bora-3a,4a-diaza-s-indacene Dyes (BODIPY)

Abstract

4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes are important in synthetic and applied chemistry. The reaction of pyrrolomethane 1 with acetyl chloride and boron trifluoride etherate in the presence of triethylamine afforded the 4,4-Difluoro-3,5,8-trimethyl-4-bora-3a,4a-diaza-s-indacene 2a. When benzoylchloride and chloroacetyl chloride were used, phenyl 2b and chloromethyl 2c derivatives formed. The treatment of pyrrolomethane 1 with 3- (phenylthio)propanal 3 in the presence of ytterbium (III) trifluoromethanesulfonate hydrate in catalitic amount yielded the 5-(2-thiophenyl ethane)-1,9-dimethyldipyrromethane 4, which was reacted with DDQ and boron trifluoride etherate in the presence of triethylamine formed 8-(2-thiophenylethan) 4,4-difluoro-3,5dimethyl-4-bora-3a,4a-diaza-3-indacene 5. The oxidation of 8-(thiomethyl) 4,4-difluoro-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene 6 with m-CPBA gave methylsulfonyl product 7. Bromination of 4,4-difluoro-3,5,8-trimethyl-4-bora-3a,4a-diaza-s-indacene 2a yielded 1,2,6,7-tetrabromo-4,4-difluoro-3,5,8-trimethyl-4-bora-3a,4a-diaza-s-indacene 8.