Selective Synthesis of exo-Spiro[2′,2′-difluorocyclopropane-3′,2′-tropanes],Synthesis

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Selective Synthesis of exo-Spiro[2′,2′-difluorocyclopropane-3′,2′-tropanes]
Synthesis ( IF 2.2 ) Pub Date : 2020-01-02 , DOI: 10.1055/s-0039-1691560
Andrii Gerasov ₁ , Grygoriy A. Dolgonos ₂ , Aleksandr Yu. Mandzhulo _{1,

3} , Alexey Ryabitsky ₁ , Volodymyr Fetyukhin ₁ , Oleg Lukin ₁ , Alexander Shivanyuk _{1,

4}

Affiliation

Conformationally restrained exo-isomers of N-Boc-protected spiro[2′,2′-difluorocyclopropane-3′,2′-tropanes] were synthesized in 62–83% yield via absolutely diastereoselective cycloaddition of CF₂, generated in situ from Me₃SiCF₃/NaI in refluxing THF, to double bonds of 3-alkylidenetropanes. Standard removal of Boc protecting groups afforded corresponding exo-spiro[2′,2′-difluorocyclopropane-3′,2′-tropane] hydrochlorides in 82–94% yields. DFT and CCSD(T) calculations revealed that the observed exo-selectivity of difluorocarbene addition is likely to be caused by a lower activation barrier of the exo-difluorocyclopropanation compared to the endo-reaction.

中文翻译：

exo-Spiro [2'，2'-二氟环丙烷-3'，2'-托烷的选择性合成

构象限制外的异构体Ñ -Boc保护的螺[2'，2'-二氟环丙烷-3'，2'-莨菪烷]通过CF的非对映选择性绝对环加成在62-83％的产率合成了₂，选自Me原位产生的₃ SiCF ₃ / NaI在回流的THF中形成3-烷基亚烷基戊烷的双键。标准去除Boc保护基团可提供82-94％的产率的相应的exo- spiro [2'，2'-difluorocyclopropane-3'，2'-tropane]盐酸盐。DFT和CCSD（T）的计算表明，所观察到的外型二氟卡宾的加成是-选择性可能受到的下活化屏障引起的外-二氟环丙烷化与内-反应相比。

更新日期：2020-01-04

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