Rapid and efficient synthesis of five- to eight-membered cyclic aminals under ultrasound irradiation

A simple, efficient, and green procedure has been developed for the synthesis of cyclic aminals from alkylenediamines and aqueous formaldehyde under ultrasound irradiation. Applying this methodology a series of five-to eight-membered 1,3-dibenzyl substituted aminals were synthesized in excellent yields after short reaction times. Results were compared to thermal conventional method. All novel compounds were identified and characterized by ¹H and ¹³C NMR spectra.