Bromination of cyclopropanes

In a preliminary study, it was shown that the bromination of cyclopropane in the presenee of iron gives a mixture of bromination products 1-3. The main adducts were 1,2- (2) and 1,3-dibromopropane (3) with a ratio of 46 39 at a reaction temperature of — 15°C and 60 10 at 60 °C. In mechanistic studies, bromine underwent addition to deuterated cyclopropanes (lrans-cyclopropane-l,l,2,3-d4 and ds-cyclopropane-l,2,3-dj) and gave almost exclusively the meio-l,3-dibromopropane derivatives as the result of a primary attack of the bromo cation at the edge with retention and the secondary addition of the bromide to the four-membered bromonium ion with inversion of configuration. ... 

Bromination of Cyclopropanes. NBS gives bromination of donor-acceptor cyclopropanes by an electron-transfer (ET) mechanism (eq 30)7 ... 

Whereas photosensitized bromination of cyclopropane affords 1,3-dibromo-propane, bromination with NBS gives cyclopropyl bromide. Thus, whereas Br reacts exclusively by attack on carbon to give ring-opening, the succinimidyl radical abstracts hydrogen to give a cycloprop radical, which rapidly combines with a bromine atom. ... 

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