1,3-Dipolar cycloaddition reaction of 3,4-dihydro-6,7-dimethoxyisoquinoline ylide with olefins

Abstract

2-Methoxycarbonylmethyl-3,4-dihydro-6,7-dimethoxyisoquinolinium ylide (2) in a concerted cycloaddition reaction of type π_4s+π_2s with dimethyl fumarate and dimethyl maleate gives the (4a)‘endo’-, (4b)‘exo-’, and (6a)‘endo’-pyrrolo [2,1-a] isoquinoline derivatives, respectively. The structure and conformation of the products have been determined by ¹H, ¹³C, and ¹⁵N n.m.r. spectroscopy and X-ray diffraction for compound (4a).