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Abstract: Ultrasound has been found to accelerate the formation of isopentenyl alcohol dianion by metalation with butyllithium in di-ethyl ether–tetrahydrofuran. The reaction of this dianion with car-bonyl compounds followed by intramolecular acetalization under Wacker-type conditions provides a direct route for the synthesis of 2-substituted perhydrofuro[2,3-b]furans. Key words: metalation, ultrasound, polyanions, Wacker-type reac-tion, cyclization, perhydrofuro[2,3-b]furans 2-Methylprop-2-en-1-ol (methallyl alcohol, 1) and 3-me-thylbut-3-en-1-ol (isopentenyl alcohol, 2) are inexpensive and commercially available building blocks, which, through a double direct metalation reaction, can be readily transformed into synthetically useful molecules (Figure 1). The formation of dianions 4 and 5 from 1 and 2 was first described in the 1970s using, respectively