TBAF-Promoted Dehydrobrominations of Vicinal Dibromides Having an Adjacent O-Functional Group

Abstract

Regioselective HBr elimination of vicinal dibromides having an adjacent oxygen functional group to give the corresponding 2-bromoalk-1-enes was controlled using 1.1 equivalents of TBAF. Two-step elimination to give the corresponding alkynes was controlled using 5.0 equivalents of TBAF. High yield and high selectivity require the presence of an oxygen functional group at the neighboring position of the elimination site.

Key words

elimination - 2-bromoalk-1-enes - alkynes - TBAF - vicinal dibromides

References and Notes

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13

General Procedures for the Syntheses of 2-Bromoalk-1-ene 1 and Alkyne 2
A mixture of 1,2-dibromoalkane 3 (1.0 equiv) and TBAF (1 M in THF solution, 1.1 equiv or 5.0 equiv) in DMF (0.1 M) was stirred at 60 ˚C. The reaction was quenched with sat. aq NH₄Cl, and the reaction mixture was extracted with EtOAc, concentrated in vacuo, and purified by silica gel column chromatography to afford 1 or 2.