One-Pot Synthesis of 4‑Carboalkoxy-Substituted Benzo[h]coumarins from α- and β‑Naphthols and Their Excited-State Properties

One-pot synthesis has been developed for 4-carboethoxybenzo­[h]­coumarins starting from α-/β-naphthols. Accordingly, diverse 4-carboethoxybenzocoumarins can be synthesized in moderate-to-excellent (31–75%) isolated yields. The synthesis involves initial oxidation of naphthols to the intermediary 1,2-naphthoquinones with 2-iodoxybenzoic acid followed by a cascade of reactions, namely, Wittig olefination, Michael addition, β-elimination, and cyclization. Furthermore, we have comprehensively investigated the excited-state properties of differently substituted 4-carboalkoxybenzo­[h]­coumarins. It is shown that they exhibit low to high fluorescence quantum yields (1–36%) and excited-state lifetimes (ca. 1–7 ns) depending on the substitution pattern and solvent employed.