Facile One-Pot Synthesis of Functionalized Quinoline-Fused Fluorescent Dihydro/Spiro-quinazolinone Derivatives

A facile and efficient
method has been developed for the synthesis
of quinoline-fused fluorescent dihydro/spiro-quinazolinones. A plausible
mechanism involving an acid-mediated enaminone intermediate is provided.
The reaction proceeded using p-toluene sulfonic acid
as a green promoter. The methodology was successful in synthesizing
various quinoline-appended spiro-quinazolinones 4a–o. The synthetic utility of compounds 4a–o was
demonstrated by synthesizing compounds 6a–d via
Suzuki coupling as a key reaction. Significantly, the π–π*
electronic transition of compounds 4c and 4k showed a blue shift. The molar extinction coefficient (ε),
Stoke’s shift (Δu̅), and quantum
yield (Φf)c were calculated for these
derivatives (4c and 4k).