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Addition of N-bromophthalimide (1) to alkynes 3 via can be explained by the Curtin-Hammett principle. When this free-radical addition is applied to the medium-sized phthalimidyl radicals 2 introduces a bromine atom and an imidyl moiety to vicinal C atoms, and highly functionalized cycloalkyne 8, the regular addition product 9 is obtained in addition to products resulting from a transannular alkenes 5 are generated. The regioselectivity of the radical attack is controlled by steric and electronic effects, whereas cyclization. Furthermore, a parallel bromine radical chain is initiated to yield the highly brominated products 11 and 12. the stereochemistry at the newly formed C=C double bond [ ] Part 3: Ref. [4d] Scheme 1. Radical addition of N-bromophthalimide (1) to linear [a] Institut für Organische Chemie der alkynes 3 Christian-
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N-Haloimides (1 -5) are used in two types of radical chain reactions: (i) the selective Ziegler bromination of allylic and benzylic positions [1], which are bromine atom chain reactions [2] and (ii) imidyl radical [3, 4] chain reactions like substitutions and especially additions to double bonds [5,
Me = Et > i-Pr & t-Bu"]. I-tert-Butoxy-2,7-octadiene, which was not obtained with conventional catalysts, is also formed. Higher telomers are formed in all cases except with t-BuOH. The presence of large amounts of phenoxy-C,2-derivatives may reflect an alteration in the reaction mechanism. The rea
Restmann on the occasion of his 60th birthday Addition of lithium to diphenylacetylene affords, depending on the conditions, either the unstable cis-dilithiostilbenel'] or the dimeric 1,4-dilithio-l,2,3,4-tetraphenyl-1,3-b~tadiene. [~] Only the latter has found applications as a difunctional organol