Design of New Efficient Carborane Molecular Scaffolds Utilizing Functionalization of C=C Double Bonds in Boron‐Substituted Allylcarboranes

ABSTRACT Some synthetic transformations of the double bonds in the available boron‐substituted allylcarboranes to access a diverse range of new functionalized carborane compounds were described. Addition reactions to the C═C double bond in 9‐allyl‐ o ‐carborane or 9‐ally‐ m ‐carborane, such as bromination under the action of NBS/LiBr system or bromoazidation, proceeded under the action of NBS/Me 3 SiN 3 and Zn(OTf) 2 as a catalyst successfully provided corresponding dibromo‐ or bromoazide carborane derivatives. Further transformations of the double bond in allylcarboranes were related to oxidation reactions leading to the formation of practically important carborane epoxides under the treatment of mono‐ and diallylcarboranes with mCPBA. Nucleophilic ring opening reactions of the epoxide ring in 9‐(2,3‐epoxypropyl)‐ m ‐carborane, which was used as an example with N ‐ or S ‐nucleophiles, were performed, and a number of corresponding carborane‐substituted β‐alcohols were synthesized. The reductive opening of epoxide ring in mono‐ and diepoxypropyl‐substituted carboranes under the action of LiAlH 4 resulted in the formation of secondary boron‐substituted carborane alcohols. An efficient rearrangement of the epoxide ring in 9‐(2,3‐epoxypropyl)‐ m ‐carborane into the corresponding methylketone using Zn(OTf) 2 as a catalyst is also described. Synthesized compounds were characterized using various spectroscopic techniques like IR, 1 H, 11 B NMR, and mass spectrometry data. The structure of five compounds was supported with single‐crystal x‐ray diffraction.