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 tert‑butyl 3-oxopiperidine-1-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. © 2020 Elsevier B.V.