Stereochemistry of cycloadducts from 3,4‐dihydro‐6,7‐dimethoxyisoquinoline ylide and olefins

Cycloaddition of 2‐methoxycarbonylmethyl‐3,4‐dihydro‐6,7‐dimethoxyisoquinolinium ylide with various E ‐substituted olefin type dipolarophiles gave products of 10b‐H, 1‐H, 2‐H and 3‐H α,α,β,β ‐relative configuration with one exception. Relative configuration of compounds prepared has been determined by 1D and 2D 1 H and 13 C nmr techniques. It has also been detected that a triple trans ⇌ cis‐1 ⇌ cis ‐2 conformation equilibrium exists in solution.