Condensation of 6-formyl-7-hydroxy-2,2-dimethylchroman with ω-nitrostyrene in the presence of triethylamine yields 3-nitro-8,8-dimethyl-2-phenyl-7,8-dihydro-2H,6H-benzo[1,2-b:5,4-b′]dipyran which on treatment with hydrogen peroxide gives 3-hydroxy-8,8-dimethyl-2-phenyl-7,8-dihydro-4H,6H-benzo[1,2-6:5,4-b′]dipyran-4-one.
在
三乙胺存在下,6-醛基-
7-羟基-2,2-二甲基苯并吡喃与ω-硝基
苯乙烯缩合生成
3-硝基-8,8-二甲基-2-苯基-7,8-二氢-2H,6H-苯并[1,2-b:5,4-b′]二
吡喃,用
过氧化氢处理后得到 3-羟基-8,8-二甲基-2-苯基-7,8-二氢-4H,6H-苯并[1,2-b:5,4-b′]二
吡喃-4-酮。