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35.2.1.5.4.2 Variation 2: Reaction of Ethers with 9-Bromo-9-borabicyclo[3.3.1]nonane

DOI: 10.1055/sos-SD-035-00308

Braun, M.Science of Synthesis, (200735342.

A mild and regioselective cleavage of ethers with formation of alkyl bromides is possible with 9-bromo-9-borabicyclo[3.3.1]nonane. Representative examples are given in Scheme 27. As illustrated by the reaction of (R)-2-methoxyoctane, the procedure leads predominantly to an inversion of the stereogenic carbon center. By comparison of the optical rotation of starting material and 2-bromooctane obtained, the degree of inversion has been determined to be 73% (Scheme 27). In unsymmetrically substituted ethers, the higher branched residue is converted into the bromide predominantly (tertiary > secondary > primary). However, in the case of butyl isobutyl ether, 1-bromobutane (27, R1=Bu) is obtained as the major product.[‌107‌]

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