Tetrahydrofuran → 3,4-dihydro-3-hydroxy-N-methyl-6-nitrospiro[2H-1-benzopyran-2,4'-tetrahydropyran]-4-carbothioamide

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Reaction Steps

To a mixture of 3.7 g of 3-hydroxy-N-methyl-6-nitrospiro[2H-1-benzopyran-2,4'-tetrahydropyran]-4-carbothioamide, 100 ml of tetrahydrofuran and 100 ml of methanol was added 2.8 g of sodium borohydride (NaBH4) with stirring under ice-cooling, and the mixture was stirred under ice-cooling for 30 minutes and then at room temperature for 24 hours. The reaction solution was vacuum-distilled, water was added therein and the resultant mixture was extracted with methylene chloride. An organic layer was washed with water and dried. The solvent was distilled to obtain 1.7 g of 3,4-dihydro-3-hydroxy-N-methyl-6-nitrospiro[2H-1-benzopyran-2,4'-tetrahydropyran]-4-carbothioamide. Subsequently, to 1.5 g of it were added 2.1 g of p-toluenesulfonyl chloride and 60 ml of pyridine. After the mixture was refluxed with heating for 1 hour, the solvent was distilled. Ice water was added to the residue and the reaction solution was acidified to be hydrochloric acid and extracted with methylene chloride. An organic layer was washed with water and dried, and the solvent was distilled. The residue was purified according to silica gel column chromatography (developing solution, MeOH:CH2Cl2 =1:99) to obtain 1.2 g of N-methyl-6-nitrospiro[2H-1-benzopyran-2,4'-tetrahydropyran]-4-carboxamide with a melting point of 183°-184° C.

Provenance & Evidence