Radical Cascade Multicomponent Minisci Reactions with Diazo Compounds

Based
on the strategy of polarity reversal in the generation of
free radicals derived from diazo compounds, photocatalyzed multicomponent
reactions (MCRs) of nitrogen aromatic heterocycles, alkenes, and diazo
compounds form functionalized derivatives in good to high yields and
exacting regioselectivities. The carbon radicals generated from the
acceptor diazo compounds are electrophilic, and their selective additions
with alkenes provide nucleophilic radicals, which enable the further
rapid assembly with various heteroarenes. A delicate balance has been
achieved between the activation of heteroarenes through protonation
and the decomposition of diazo compounds by the same acid. This multicomponent
Minisci reaction shows high functional group tolerance, especially
in the incorporation of biologically active molecules. Detailed mechanistic
studies that include photophysical measurements elaborate this radical
cascade reaction. Furthermore, this transformation provides new opportunities
for versatile reactions of diazo compounds in radical cascade multicomponent
coupling reactions.