Chemical consequences of fluorine substitution. Part 4. Diels–Alder reactions of fluorinated p-benzoquinones with Dane's diene. Synthesis of fluorinated D-homosteroids
作者:Michael Essers、Günter Haufe
DOI:10.1039/b208001j
日期:——
depends on the fluorine substitution pattern of the corresponding fluorinated p-benzoquinones. If the p-benzoquinone (2) contains an unfluorinated double bond, this bond reacts faster with diene 1 yielding endo-products selectively. In contrast, [4+2]cycloadditions with 2,6-difluoro (2c) and 2,3,5,6-tetrafluorobenzoquinone (2d) gave the products with exo-orientation of the carbonyl part preferably.
在Diels-Alder反应中,四个氟化的对苯醌(2)与Dane的二烯(1)反应,并对形成的氟化D-类固醇进行了表征。产品的数量,其立体化学和稳定性取决于相应的氟化对苯醌的氟取代模式。如果对苯醌(2)包含未氟化的双键,则该键与二烯1的反应更快,选择性地产生内产物。相反,[4 + 2]环加成有2,6-二氟(2c)和2,3,5,6-四氟苯醌(2d)给出了具有外向取向的产品羰 最好是一部分。