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Please login to access the full content or check if you have access via35.2.1.4.2.2 Variation 2: Reactions of Chloroalkanes with Gaseous Hydrogen Bromide in the Presence of Iron(III) Bromide
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Braun, M., Science of Synthesis, (2007) 35, 315.
Secondary and tertiary chloroalkanes, as well as 4-chlorobenzyl chloride, are converted into the corresponding bromoalkanes 4 (Scheme 5) by treatment with gaseous hydrogen bromide in the presence of a catalytic amount of iron(III) bromide. Strictly anhydrous conditions are necessary as complications due to elimination reactions can then be suppressed [anhydrous iron(III) bromide required in these reactions is generated by irradiating a mixture of pentacarbonyliron(0) and bromine with light (λ = 360 nm)].[4,5] Retention of configuration is observed in the conversions of vicinal dichlorides into their dibromides. The diastereomers of 2-bromo-3-chlorobutane react similarly, but generally the chlorine atoms of other chloroalkanes are not replaced in such a stereoselective manner. Thus, exo-2-chloronorbornane leads to a 4:1 mixture of exo- and endo-2-bromonorbornanes. In the main, the substitution reactions of primary chloroalkanes fail to give satisfactory results.
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M8Me | M8Me | Meee (e) | Meeee (%) | Mee |
---|---|---|---|---|
MeMe | MeMe | 8.8 | 88 | [8] |
8.8 | 88/88e | [8] | ||
8.8 | 88 | [8] | ||
MeMM(Me)Me | MeMM(Me)Me | 8 | 88e | [8] |
8 | 88e,e | [8] | ||
8 | 88 | [8] | ||
8 | 88e,e,e | [8] | ||
88 | 88/8e | [8] | ||
8.8 | 88 | [8] |
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Meeeeeeeeeee 8; Meeeeee Meeeeeeee:[8]
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References
[2] | Meeeeeee, M.; Meeeeeeeeee, M.; Meeeee, M. M.; Meeeee, M. M., Meeeeeeeeee Meee., (8888) 88, 8888. |
[4] | Meee, M. M.; Meeee, M. M., M. Meee. Mee., Meee. Meeeee., (8888), 8888. |
[5] | Meee, M. M.; Meeee, M. M., M. Mee. Meee., (8888) 88, 8888. |