Synthesis, spectral characterization and photophysical studies of tetrahydroquinolines

A metal-free, ultrasound-assisted, fast synthesis of fluorescent N-Boc-protected 1,2,3,4-tetrahydroquinolines 9a-p is described through carbanion-induced ring transformation of 6-aryl-2H-pyran-2-ones 7 with tent-butyl 3-oxopiperidine-l-carboxylate 8 under basic condition. The reaction products 9a-p were isolated in high yields. Our synthetic approach is flexible for introducing electron-withdrawing and electron-donating groups. All the synthesized 1,2,3,4-tetrahydroquinolines 9a-p showed blue fluorescence in the range of 422-470 nm. Based on the optical behavior of compounds 9a-p, we calculated stokes shift, quantum yield and optical band gap which are highly influenced by the substituents in the ring. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

A metal-free, ultrasound-assisted, fast synthesis method is described for fluorescent N-Boc-protected 1,2,3,4-tetrahydroquinolines. The synthesized compounds showed blue fluorescence and optical properties were influenced by substituents in the ring.