Synthesis of 3‐(ω‐Hydroxyalkoxy)isobenzofuran‐1(3H)‐ones by Trifluoroacetic Acid‐Mediated Lactonization of tert‐Butyl 2‐(1,3‐Dioxol‐2‐yl)‐ or 2‐(1,3‐Dioxan‐2‐yl)benzoates

An efficient two-step method for the preparation of 3-(2-hydroxyethoxy)- or 3-(3-hydroxypropoxy)isobenzofuran-1(3H)-ones 3 has been developed. Thus, the reaction of 1-(1,3-dioxol-2-yl)- or 1-(1,3-dioxan-2-yl)-2-lithiobenzenes, generated in situ by the treatment of 1-bromo-2-(1,3-dioxol-2-yl)- or 1-bromo-2-(1,3-dioxan-2-yl)benzenes 1 with BuLi in THF at −78°, with (Boc)2O afforded tert-butyl 2-(1,3-dioxol-2-yl)- or 2-(1,3-dioxan-2-yl)benzoates 2, which can subsequently undergo facile lactonization on treatment with CF3COOH (TFA) in CH2Cl2 at 0° to give the desired products in reasonable yields.

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