1- Bromo-2-fluorocyclohexanes, reaction with

Tertiary hydrogens in substrates which readily form carbocation.s. such as adamantane, dimantane, and triphenylmethanc, are selectively fluorinated by treatment with a mixture of nitrosyl tetrafluoroborate and 70% hydrogen fluoride in pyridine in excellent yield.28 This reaction has been extended to secondary hydrogens ji to a bromine atom in a series of bro-moalkanes, e.g. fluorination of bromocyclohexane to give nwrv-l-bromo-2-fluorocyclohexane (8).26... 

Scheme 7.2. A representation of the radical reduction of l-bromo-2-fluorocyclohexane with tri-l-butyltm hydride (tri-n-butyltin hydride, [CH3CH2CH2CH2]3SnH) in a radical reaction initiated by azobisisobutyronitrile ([(CH3)2C(CN)N=N(CN)C(CH3)2], AIBN). It is important to note that the bromine (Br) is replaced in preference to the fluorine and that the amount of the one termination product shown (the dicyclohexanedifluoride) is minor.

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