Saturated organic compounds containing a hydrogen atom bound to a tertiary carbon atom may be electrophilically fluorinated by reaction with an electrophilic fluorinating agent such as molecular fluorine or trifluoromethyl hypofluorite under conditions whereby the formation of free fluorine radicals is suppressed, e.g. by the presence of a free radical inhibitor such as oxygen or nitrobenzene, the reactants being substantially homogeneously dispersed in a liquid medium, e.g. a solvent medium such as fluorotrichloromethane or chloroform/fluorotrichloromethane, so that the said hydrogen atom is electrophilically replaced by a fluorine atom. The fluorination is highly selective and, in the case of complex substrates such as saturated steroids which contain a number of tertiary C--H bonds, may be substantially completely confined to replacement of the hydrogen atom at the tertiary carbon atom which has the highest electron density about the C--H bond. The electron density and thus the direction of the fluorination may be controlled by appropriate selection of substituent groupings in the substrate molecule. Novel 14.alpha.-fluorosteroids are also disclosed, including compounds having valuable androgenic or progestational activity and useful synthetic intermediates.
含有氢原子与三级碳原子结合的饱和有机化合物可以通过与亲电性
氟化剂(如分子
氟或三
氟甲基
次氟酸盐)反应,在抑制自由
氟自由基形成的条件下,例如通过存在自由基
抑制剂(如
氧气或
硝基苯),使反应物在液体介质中(例如溶剂介质如
氟三
氯甲烷或
氯仿/
氟三
氯甲烷)被均匀分散,从而使所述氢原子被电泳取代为
氟原子。
氟化反应高度选择性,在复杂的底物(如含有多个三级碳-氢键的饱和类
固醇)中,可以完全限制在具有最高电子密度的三级碳原子上的氢原子的取代中。通过适当选择底物分子中的取代基,可以控制电子密度和因此
氟化的方向。此外,还披露了新型的14α-
氟类
固醇,包括具有有价值的雄激素或孕激素活性和有用的合成中间体。