Bromination semibullvalene

The synthesis of an optically active semibullvalene has been realized for the first time Sequential reaction of methylcyclooctatetraene with one equivalent each of bromine and (—)-e/Kfo-bomyltriazolinedione gave a mixture of Diels-Alder adducts which when debrominated afforded 362. Photocyclization to bishomocubane 363 allowed for chromatographic separation of the two diastereomers. Silver ion-... 

The cations CH2I+ and CD2I+ were observed in the gas phase, and their electronic spectra recorded.77 Quantum chemical calculations for semibullvalene bromination... 

The mechanism for bromination of semibullvalene has been proposed, based on quantum chemical calculations. The reaction pathway involves concerted bromine addition and cyclopropane ring opening to form an allylic cation, without the intermediacy of a bromonium or a cyclopropylcarbinyl cation.18... 

Upon examining the structure of semibullvalene, shown in Figure 1, it becomes obvious how the Weiss-Cook reaction could be implemented in the construction of this framework. The preparation of the substituted semibullvalene 55 began with the Weiss-Cook diketone 11 (R = R" = Me). Bromination followed by cyclizing dehydrobromination gave rise to 54. Reduction of the ketones and conversion to the corresponding mesylates preceded a conjugate 1,4-elimination reaction to afford the substituted derivative 55. 

Paquette LA, Bimberg GH, Clardy J et al (1973) Stereoselective 1,4-bromination of semibullvalene and tri-n-butyltin hydride reduction of the dibromide. J Chem Soc Chem Commun 129-130... 

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