Selective Synthesis of ω-Hydroxyalkoxy Derivatives of Binor-S with the Use of a Binary Catalytic System FeCl3 – TsOH*H2O

Binor-S (heptacyclo[8.4.0.0(2,12).0(3,8).0(4,6).0(5,9).0(11,13)]tetradecane is a strained polycyclic hydrocarbon attracting wide interest as a precursor of diamantane and a starting compound for the synthesis of functionalized polycyclic structures. We report an efficient and selective method for the regioselective alcoholysis of binor-S with α,ω-diols with the use of the binary catalytic system FeCl3–TsOH H2O (2 mol%). The reaction proceeds with regioselective cleavage of the C4–C5 bond of the cyclopropane ring of binor-S at 120°C in 3 h. The mechanism involves the activation of the cyclopropane bond by the Lewis acid (FeCl3), while the Bronsted acid (TsOH) enhances the electrophilicity of the system. This synergy allows for the synthesis of various ω-hydroxyalkoxy derivatives from α,ω-diols with high yields (up to 98%). Notably, this method provides a significant practical advantage over previous methods that required high-pressure autoclaves or sealed tubes at 120–150oC. The study demonstrates that for diols with four or more methylene groups, the FeCl3–TsOH system provides yields comparable to those achieved using ionic liquids. For shorter diols prone to acid-catalyzed dehydration (ethylene glycol, 1,3-propanediol) catalysis with ionic liquids remains preferable. However, it should be noted that our methodology uses only 2 mol% of the catalyst system, while the alternative method uses 10 mol% of the ionic liquid. The developed methodology continues our development of the direction of targeted functionalization of polycyclic framework compounds, including those with an adamantane skeleton, with the aim of creating new derivatives with promising physicochemical properties.