Construction of heterocycles via 1,4-dipolar cycloaddition of quinoline-DMAD zwitterion with various dipolarophiles

Quinoline forms 1,4-zwitterion with dimethyl acetylenedicarboxylate, which is trapped by various dipolarophiles to yield a variety of pyridoquinoline and oxazinoquinoline derivatives. (c) 2008 Elsevier Ltd. All rights reserved.