Tetrabutylammonium Fluoride in Dimethyl Sulfoxide: A Reagent Combination­ for the Twofold Dehydrobromination of Vicinal Dibromides

Abstract

Exhaustive dehydrobromination of vicinal dibromides contained in cyclic systems of different ring sizes and containing diverse types of functionalities occurred for a variety of substrates when heated with tetrabutylammonium fluoride in dimethyl sulf­oxide.

Key words

fluoride ion - dehydrobromination - dimethyl sulfoxide - unsaturated heterocycles - valence isomerization

References

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10

Paquette, L. A.; Dura, R. D.; Fosnaugh, N.; Stepanian, M. submitted for publication.

18

The reaction outcome of the dibromide in run 10 (Table [1] ) is exemplary for the following reagents and conditions: (i) DBU, MeCN, sealed tube, 110 °C, 48 h (42% yield); (ii) NaH, THF, r.t. (no reaction); (iii) NaH, THF, reflux (no reaction); (iv) 1 M TBAF in THF (no DMSO) (24% yield); (v) pyridine (neat), reflux (no reaction); (vi) DABCO, benzene, reflux (no reaction); (vii) DABCO, DMSO, reflux (no reaction).

19

The removal of Bu₄N⁺ is trivial: a solvent into which DMSO does not partition well, for example Et₂O, needs to be used and the soln should be washed with aq NH₄Cl soln.