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 1H and 13C nmr techniques. It has also been detected that a triple trans ⇌ cis-1 ⇌ cis-2 conformation equilibrium exists in solution.