methyl 2-(chlorocarbonyl)benzoate

Methyl 2-(chlorocarbonyl)benzoate can be used for N-phthalylation of α-amino acids and preparation of isocoumarins.

Heat o-methoxycarbonylbenzoic acid (methyl hydrogen phthalate) with Thionyl Chloride for 1 h on a steam bath (eq 1).

Corrosive and moisture sensitive; reacts with protic solvents; use in a fume  hood; do not breathe vapors and avoid contact with skin, eyes, and clothing; causes burns and irritation of the  respiratory system; lachrymator; use immediately after preparation.