Abstract
Triazolinediones react with olefins bearing allylic hydrogens in an ene fashion to
afford N -allylurazoles. This reaction, apart from considerable mechanistic attention, shows
also substantial synthetic utility. Extensive experimental data, such as deuterium
kinetic isotope effects, trapping of intermediates, and stereochemical studies, and
to a lesser extent computational work, support a two-step mechanism with irreversible
formation of a three-membered ring intermediate (aziridinium imide). On the basis
of recent experimental and theoretical work, an open biradical has been proposed as
the key intermediate.
1 Introduction and Background
2 Isotope Effects
3 Regioselectivity and Diastereoselectivity Studies
3.1 Regioselectivity
3.1.1 Regioselectivity with Simple Alkenes
3.1.2 Regioselectivity with Substituted Alkenes, Styrenes, α,β-Unsaturated Esters,
Carbonyl Compounds and Sulfoxides
3.2 Diastereoselectivity
4 Solvent Trapping Studies
5 Stereochemistry: Simple Alkenes, Non-Polar Solvents
6 Theoretical Calculations
7 Concluding Remarks
Key words
ene reactions - regioselectivity - diastereoselectivity - stereochemistry - kinetic
isotope effects
