Ultrasound has been found to accelerate the formation of isopentenyl
alcohol dianion by metalation with butyllithium in diethyl ether-tetrahydrofuran.
The reaction of this dianion with carbonyl compounds followed by
intramolecular acetalization under Wacker-type conditions provides
a direct route for the synthesis of 2-substituted perhydrofuro[2,3-b]furans.
metalation - ultrasound - polyanions - Wacker-type
reaction - cyclization - perhydrofuro[2,3-b]furans