Herein we report the highly selective radical chlorination of 2,2-difluorobicyclo[1.1.1]pentane-1,3-dicarboxylic acid. Together with radical hydrodechlorination by TMS₃SiH, four new bicyclo[1.1.1]pentane cages carrying two fluorine and one to three chlorine atoms in bridge positions have been obtained. The exact positions of all halogen atoms have been confirmed by X-ray diffraction. The acidity constants (pK_a) for all new derivatives have been determined by capillary electrophoresis, and these experimental values show excellent agreement with pK_as predicted by DFT methods. Extensive DFT calculations have been used to rationalize the selective formation of four out of nine possible F₂Cl_1–4 isomers of bridge-halogenated bicyclo[1.1.1]pentanes and to obtain relative strain energies for all possible isomers.

中文翻译：

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多卤化双环[1.1.1]戊烷-1,3-二羧酸

在此，我们报告了 2,2-二氟双环 [1.1.1] 戊烷-1,3-二羧酸的高选择性自由基氯化。与 TMS ₃ SiH 的自由基加氢脱氯一起，获得了四个新的双环 [1.1.1] 戊烷笼，在桥位上携带两个氟和一到三个氯原子。所有卤素原子的确切位置已通过 X 射线衍射确认。所有新衍生物的酸度常数 (p K _a ) 都通过毛细管电泳确定，这些实验值与DFT 方法预测的p K _a s非常吻合。广泛的 DFT 计算已被用于合理化九种可能的 F ₂ Cl _1-4中四种的选择性形成 桥卤化双环[1.1.1]戊烷的异构体，并获得所有可能异构体的相对应变能。