Synthesis of 2,3,4,6,7,8-Hexahydro-5H-1-benzopyran-5-ones and 3-(6-Oxo-1-cyclohexenyl)alkanoic Acids by Reduction of 4,6,7,8-Tetrahydro-2H-1-benzopyran-2,5(3H)-diones
作者:Hermann Hombrecher、Paul Margaretha、Paul Tissot
DOI:10.1002/hlca.19860690723
日期:1986.10.29
and 1d (direct irradiation at λ = 300 or 254 nm in i-PrOH, or sensitized irradiation in acetone/i-PrOH or benzene/i-PrOH) gives 3-(6-oxo-1-cyclohexenyl)alkanoic acids 6 in 50–80%, while 1c affords the isomeric 3-(4,4-dimethyl-6-oxo-1-cyclohexenyl)-4-methyl-4-pentenoic acid (9) in 73% isolated yield. Electrochemical reduction (Hg, CH3CN, Bu4N+ClO, −2.6 V vs. Ag/Ag+) requires more than 4 Farad/mol for
报道了还原4,6,7,8-四氢-7,7-二甲基-2 H -1-苯并吡喃-2,5(3 H)-二酮1的比较结果。氢化物还原(LiAlH 4在Et 2 O中或NaBH 4在i-PrOH中)提供2,3,4,6,7,8-六氢-5 H -1-苯并吡喃-5-酮5的分离产率为30-60% 。1b和1d的光化学还原(在i-PrOH中以λ= 300或254 nm直接照射,或在丙酮/ i-PrOH或苯/ i-PrOH中进行敏化照射)得到3-(6-氧代-1-环己烯基)链烷酸酸在50–80%中占6,而1c以73%的分离产率得到异构体3-(4,4-二甲基-6-氧代-1-环己烯基)-4-甲基-4-戊烯酸(9)。电化学还原(Hg,CH 3 CN,Bu 4 N + ClO,-2.6 V对Ag / Ag +)需要消耗大于4法拉/摩尔才能消耗1,而没有检测到任何主要产物。