5 BODIPY Dyes and Their Analogues
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Fig. 5.6 Synthetic method of symmetrical BODIPY dyes. Method (2): reaction of acyl chlorides
with pyrroles. Substituents on the pyrrole rings have been omitted for clarity
Fig. 5.7 Synthetic method of symmetrical BODIPY dyes. Method (3): reaction of pyrrole-2carbaldehydes with phosphoryl chloride. Substituents on the pyrrole rings have been omitted for
clarity
Fig. 5.8 Synthetic method of symmetrical BODIPY dyes. Method (4): reaction of dipyrrylketone
with phosphoryl halide. Substituents on the pyrrole rings have been omitted for clarity
Through method (1) (Cui et al. 2007), BODIPY dyes can be synthesized in one-pot
reactions without the isolation of the intermediates (Fig. 5.5). First, dipyrromethanes
are prepared by the condensation of aromatic aldehydes and α-free pyrroles. Second,
oxidation by DDQ gives the dipyrromethanes, and finally, boron complexation
by boron trifluoride ethyl ether complex (BF 3 ·OEt 2 ) forms meso-aryl substituted
BODIPY dyes.
In method (2) (Kim et al. 2015; Michel et al. 2012; Jiang et al. 2017), condensation of acyl chlorides with α-free pyrroles gives unstable dipyrromethene hydrochloride salt intermediates. Subsequent treatment with Et 3 N and BF 3 ·OEt 2 to provides
meso-aryl (Kim et al. 2015) or alkyl (Michel et al. 2012) substituted BODIPY dyes
(Fig. 5.6). meso-CF 3 substituted BODIPY dyes can also be obtained by one-pot