Agro-waste as source of fine and industrial chemicals: synthesis of 2-formyl-6 hydroxybenzoic acid and 4-methoxyisobenzofuran-1,3-dione from cashew nut shell liquid

Abstract

This paper reports on the synthesis of 2-formyl-6-hydroxybenzoic acid (8) and 4 methoxyisobenzofuran-1,3-dione (10) from a renewable natural material Cashew Nut Shell Liquid (CNSL) achieved in five and seven steps, respectively. Anacardic acid was isolated from CNSL, dimethoxylated into (E)-methyl 2-methoxy-6-(pentadec-8-enyl)benzoate which was subsequently hydrogenated into methyl 2-methoxy-6-pentadecylbenzoate. Benzylic bromination of the methoxyester, and dehydrobromination afforded (E)-methyl 2-methoxy-6-(pentadec-1-enyl)benzoate which upon ozonolysis gave methyl 2-formyl-6-methoxybenzoate. Oxidation and dehydration of 8 formed methoxyphthalic anhydride (10). The work reported in this paper has further demonstrated the resourcefulness of cashew nut shell liquid as a renewable natural resource for synthesis of fine and industrial chemicals.

Keywords:  Anacardium occidentale, Cashew Nut Shell Liquid, Anacardic acid, 2 formyl-6-methoxybenzoate, methoxyphthalic anhydride