Dedicated to Professor Hisashi Yamamoto on the occasion of his 80th birthday.
An asymmetric isomerization of β,γ-unsaturated butenolides with a newly developed betaine catalyst at a 0.2–2 mol% loading, an improvement upon available methods that use 0.5–2.0 mol% catalyst.
Key words
butenolides - isomerization - betaines - cinchona alkaloids - asymmetric catalysis - furanones