•Synthesis of 1,2,3,4–tetrahydroquinolines 9 & 11 was achieved in good yields.•All the synthesized compounds were characterized by NMR, Mass & IR Spectroscopy.•Compounds 9 & 11 cored with electronic push-pull system and showed blue fluorescence.•Push-pull electronic system in compounds 9 & 11 lead Internal Charge Transfer.•The stoke shifts, quantum yield and band gap were calculated for compounds 9 & 11. 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. Display omitted