Radical addition reactions of fluorinated species. Part 8. Regioselectivity of radical additions to perfluoroalkylethylenes and quantum chemical calculations. Highly selective two-step synthesis of 4-(perfluoroalkyl)butane-1,2-diols
作者:Vladimı́r Cı́rkva、Stanislav Böhm、Oldřich Paleta
DOI:10.1016/s0022-1139(99)00237-7
日期:2000.3
Perfluoroalkylethylenes RF–CHCH2 (RF = C4F9,C6F13,C8F17) added easily nucleophilic radicals generated from alkanols, oxolane and 2,2-dimethyl-1,3-dioxolane. The additions were initiated photochemically in the presence of acetone or by dibenzoyl peroxide and were completely regioselective and almost completely chemoselective with preparative yields up to 90%. 4-Fluoroalkylated dioxolanes obtained (5a–5c)
全氟烷基乙烯R F –CH = CH 2(R F = C 4 F 9,C 6 F 13,C 8 F 17)易于添加由链烷醇,氧杂环戊烷和2,2-二甲基-1,3-二氧戊环生成的亲核基团。该添加是在丙酮存在下或通过过氧化二苯甲酰以光化学方式引发的,并且具有完全的区域选择性和几乎完全的化学选择性,制备产率高达90%。在酸性介质中通过甲醇分解将获得的4-氟烷基化的二氧戊环(5a-5c)脱保护,得到4-全氟烷基-1,2丁二醇(15a-15c)转化为相应的双甲基丙烯酸酯(16a-16c)。2,2,4-三甲基-1,3-二氧戊环(17)反应,在两个中心,以产生与加合物的自由基对的优先攻击氟烷基二氧戊环的84:16区域异构体混合物在更空间受阻的叔C-H键17。讨论了全氟烷基乙烯加成物的完全区域选择性与全氟烷基化链的“尾部效应”以及使用PM3和从头算量子化学方法计算的中间加成基自由基的能量。