Synthesis of Spiro[2 H-1-benzopyran-2, 3'-phthalides]

Abstract

The condensation of 2-acetylbenzoic acids with salicylaldehydes has been studied.2-Hydroxy2'-carboxychalcones were obtained in the alkaline condensation. Dehydration by heat or by usual dehydrating agents gave spiro[2 H-1-benzopyran-2, 3'-phthalides] [1]. In the acidic condensation, [1] was obtained directly. [1] was also obtaned by the reaction of 3-methylenephthalide with salicylaldehyde in sulfuric acid. Similarly spiro[3 H-naphtho[2, 1-b]pyran-3, 3'- phthalide] [2] was prepared by the condensation of 2-acetylbenzoic acid with 2-hydroxy-1- naphthaldehyde in the presence of alkali, while selfcondensation product of 2-acetylbenzoic acid was obtained in place of [2] in the acidic condensation.