In this work, we have reported a mild, fast and efficient method for the preparation of 1,3-dithiolanes using catalytic amount of P2O5/Al2O3 under solvent-free conditions (MW). A wide variety of aldehydes and ketones can be easily protected to their corresponding 1,3-dithiolanes using 1,2-ethanedithiol in the presence of catalyting amount of P2O5/Al2O3 under microwave irradiation. Using this method, transthioacetalization of acetals and acylals into their corresponding 1,3-dithiolanes was also carried out in good yields and short reaction times. (C) 2008 Elsevier B.V. All rights reserved.