Silver(I)‐Catalyzed Regioselective Synthesis of Dihydrofuro[3,4‐b]quinolines from o‐Alkynylquinoline‐MBH Adducts and Evaluation of their Photophysical Properties

Abstract

A simple and facile approach is described for the regioselective synthesis of dihydrofuro[3,4‐b]quinolines from ortho‐alkynylquinoline‐Morita‐Baylis‐Hillman adducts under mild reaction conditions. Interestingly, in case of aromatic alkynes, 5‐exo‐dig cyclization was observed, while in case of aliphatic long chain alkynes, 6‐endo‐dig cyclized products were obtained. The present approach does not require any dry conditions, tedious work‐up or inert atmosphere for the production of dihydrofuro[3,4‐b]quinolines. The exact structures and stereochemistry of the synthesized molecules were assigned by NMR and X‐ray crystallographic analysis. Their photophysical properties were also evaluated.

Radical Promoted Synthesis of Furoquinolines via Anomalous Dakin‐Type Reaction

“…Similarly, in 2019, furoquinolines were constructed using copper catalyst via intramolecular cyclization (Scheme 1b) [14] . Very recently, silver‐catalyzed synthesis of vinyl substituted furoquinolines was developed by Singh and co‐workers (Scheme 1c) [15] . The synthesis of furo[3,2‐ b ]quinolines from ortho ‐alkynyl aldehyde without using a transition‐metal catalyst and external nucleophile is still unexplored.…”

“…[14] Very recently, silver-catalyzed synthesis of vinyl substituted furoquinolines was developed by Singh and co-workers (Scheme 1c). [15] The synthesis of furo [3,2-b]quinolines from ortho-alkynyl aldehyde without using a transition-metal catalyst and external nucleophile is still unexplored. The use of expensive transition metal catalysts restricted their applications for industrial purposes.…”