Two syntheses of 3-fluorofuran-2(5H)-one (1) based on Wittig-Horner reaction of ethyl (diethoxyphosphoryl)fluoroacetate (15) with 2-oxoethyl acetate (16) or on transformation of D-erythronolactone (10) are given. 3-Fluorofuran-2(5H)-one (1) and ethyl 2-fluorobut- 2-enoate (2) undergo conjugate addition with soft nucleophiles based on arene- carboxaldehyde dithioacetals 7 to form 2-fluorolactones 3 and 2-fluoroalkanoates 4. Intermediate enolates can be trapped in the sense of tandem addition with arenecarboxaldehydes 8 or (arylmethyl)bromides 9 to form intermediates 5 and 6 for fluorolignans. Although the conjugate addition proceeds with low stereoselectivity yielding mixture of both diastereoisomers, the electrophile in tandem addition attacks the intermediary fluoroenolate exclusively anti to its bulky β-substituent in good accord with non-fluorinated furan- 2(5H)-ones.
两种3-
氟呋喃-2(5H)-酮(1)的合成基于乙基(二乙氧
磷酰基)
氟乙酸酯(15)与2-氧
乙酸乙酯(16)进行的Wittig-Horner反应,或者基于D-赤霉糖内酯(10)的转化。3-
氟呋喃-2(5H)-酮(1)和乙基2-
氟丁-2-烯酸酯(2)与基于
芳烃羧醛二
硫代
缩醛(7)的软亲核试剂发生共轭加成,形成2-
氟内酯(3)和2-氟烷酸酯(4)。中间体烯醇酸盐可以在串联加成中被捕获,与
芳烃羧醛(8)或(芳基甲基)
溴化物(9)形成中间体(5)和(6),用于
氟木脂素的合成。尽管共轭加成的立体选择性较低,产生两种对映异构体的混合物,但串联加成中的亲电试剂仅攻击中间体
氟烯醇酸盐,与其庞大的β-取代基相反,与非
氟代
呋喃-2(5H)-酮的情况非常符合。