An Efficient Synthesis of 3-(1H-Tetrazol-5-yl)coumarins (=3-(1H-Tetrazol-5-yl)-2H-1-benzopyran-2-ones) via Domino Knoevenagel Condensation, Pinner Reaction, and 1,3-Dipolar Cycloaddition in Water

A novel straightforward synthesis of 3-(1H-tetrazol-5-yl)coumarins (=3-(1H-tetrazol-5-yl)-2H-1-benzopyran-2-ones) 6 via domino Knoevenagel condensation, Pinner reaction, and 1,3-dipolar cycloaddition of substituted salicylaldehydes (=2-hydroxybenzaldehydes), malononitrile (propanedinitrile), and sodium azide in H2O is reported (Scheme 1 and Table 2). This general protocol provides a wide variety of 3-(1H-tetrazol-5-yl)coumarins in good yields under mild reaction conditions.