Metal-free benzannulation reaction of 2-(phenylethynyl)-benzaldehyde and alkynes proceeded in the presence of Brønsted acid under microwave irradiation to give the 2,3-disubstituted naphthalenes.This research was financially supported in part by the Kansai University Subsidy for Supporting Young Scholars, 2015.2015年度関西大学若手研究者育成経