Herein we have developed a strategy for chemodivergent
functionalization
of N-methylalkanamides via C–Br bond activation
of CBr4, using an orthorhombic CsPbBr3 perovskite
photocatalyst under blue LEDs (450–470 nm). The selectivity
of whether a 5-exo-trig spiro cyclization or a 6-endo-trig cyclization
occurred depended on the stability of the radical intermediate that
was formed after the addition of the bromide radical to the starting
compound to obtain 3,8-dibromo-1-methyl-4-phenyl-1-azaspiro[4.5]deca-3,6,9-trien-2-on
or 3-bromo-1-methyl-4-phenyl-1-azaspiro[4.5]deca-3,6,9-triene-2,8-dione
or 3-bromo-6-(tert-butyl)-1-methyl-4-phenylquinolin-2(1H)-one.