Bodipy Derivatives as Organic Triplet Photosensitizers
for Aerobic Photoorganocatalytic Oxidative Coupling of Amines and
Photooxidation of Dihydroxylnaphthalenes
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Abstract
We used iodo-Bodipy derivatives that
show strong absorption of
visible light and long-lived triplet excited states as organic catalysts
for photoredox catalytic organic reactions. Conventionally most of
the photocatalysts are based on the off-the-shelf compounds, usually
showing weak absorption in the visible region and short triplet excited
state lifetimes. Herein, the organic catalysts are used for two photocatalyzed
reactions mediated by singlet oxygen (<sup>1</sup>O<sub>2</sub>),
that is, the aerobic oxidative coupling of amines and the photooxidation
of dihydroxylnaphthalenes, which is coupled to the subsequent addition
of amines to the naphthoquinones, via C–H functionalization
of 1,4-naphthoquinone, to produce <i>N</i>-aryl-2-amino-1,4-naphthoquinones
(one-pot reaction), which are anticancer and antibiotic reagents.
The photoreactions were substantially accelerated with these new iodo-Bodipy
organic photocatalysts compared to that catalyzed with the conventional
Ru(II)/Ir(III) complexes, which show weak absorption in the visible
region and short-lived triplet excited states. Our results will inspire
the design and application of new organic triplet photosensitizers
that show strong absorption of visible light and long-lived triplet
excited state and the application of these catalysts in photoredox
catalytic organic reactions