Acid-promoted cyclization of 2-propynolphenols leading to 4-tosyloxy-2H-chromenes

A novel and efficient p-TsOH-promoted cascade cyclization of 2-propynolphenols is developed to give 4-tosyloxy-2H-chromenes in moderate to efficient yields. It is noted that p-TsOH acts not only as a promoter in this reaction, and also as the sulfonate source. Importantly, the obtained 4-tosyloxy-2H-chromenes can be used as versatile intermediates for the synthesis of various functionalized compounds through diverse metal-catalyzed cross-coupling reactions. Moreover, this method can be enlarged to gram scale. (C) 2018 Elsevier Ltd. All rights reserved.