New Access to 2,3-Disubstituted Quinolines through Cyclization of o-Alkynylisocyanobenzenes
摘要:
[GRAPHICS]o-Alkynylisocyanobenzenes underwent nucleophile-induced intramolecular cyclization to give 2,3-disubstituted quinoline derivatives in high yields. In addition to the oxygen and nitrogen nucleophiles such as methanol and diethylamine, the nucleophilic carbon of the enolate of malonate induced the cyclization effectively. Reaction of 1,4-di(trimethylsilylethynyl)-2,3-diisocyanobenzene with methanol afforded 2,9-dimethoxy-1,10-phenanthroline in good yield.
Diversified 2-alkoxy- and 2-aroxy-3-substituted quinolines were synthesized from o-alkynylaryl isocyanides and alcohols and phenols promoted by DABCO, respectively. The reaction was initiated by nucleophilic addition of DABCO to isocyanide and subsequent cycliztion, leading to a DABCO-quinoline-based adduct as the reactive intermediate, followed by substitution of the DABCO moiety with oxygenated nucleophiles.
Tetrabutylammonium chloride-triggered 6-endo cyclization of o-alkynylisocyanobenzenes: an efficient synthesis of 2-chloro-3-substituted quinolines
A highly efficient one-pot synthesis of 2-chloro-3-substituted quinolines has been developed by tetrabutylammonium chloride-triggered 6-endo cyclization of o-alkynylisocyanobenzenes, which are generated in situ by dehydration of the corresponding N-(2-ethynylphenyl)formamides. (C) 2009 Elsevier Ltd. All rights reserved.