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. 2021 Aug 6;23(15):6105-6109.
doi: 10.1021/acs.orglett.1c02186. Epub 2021 Jul 28.

Iron(II) and Copper(I) Control the Total Regioselectivity in the Hydrobromination of Alkenes

Daniel A Cruz  1 , Victoria Sinka  2 , Pedro de Armas  2 , Hugo Sebastian Steingruber  1 , Israel Fernández  3 , Víctor S Martín  1 , Pedro O Miranda  2 , Juan I Padrón  2
Affiliations

Iron(II) and Copper(I) Control the Total Regioselectivity in the Hydrobromination of Alkenes

Daniel A Cruz et al. Org Lett. .

Abstract

A new method that allows the complete control of the regioselectivity of the hydrobromination reaction of alkenes is described. Herein, we report a radical procedure with TMSBr and oxygen as common reagents, where the formation of the anti-Markovnikov product occurs in the presence of parts per million amounts of the Cu(I) species and the formation of the Markovnikov product occurs in the presence of 30 mol % iron(II) bromide. Density functional theory calculations combined with Fukui's radical susceptibilities support the obtained results.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1. Hydrobromination Addition Reaction Approaches
Figure 1
Figure 1
Reaction conditions. (a) Alkene (1.2 mmol, 1.0 equiv), TMSBr (3.0 equiv), CH2Cl2 (0.1 M), saturated H2O (Milli-Q), O2 (present in the solvent and the Milli-Q water), amylene (170 ppm), and CuBr (present in the commercial TMSBr). (b) Scope and yields of the anti-Markovnikov hydrobromination of alkenes. (c) Markovnikov and anti-Markovnikov orientations in styrene derivatives.
Figure 2
Figure 2
Preferred radical addition in the hydrobromination of AcO—(CH2)3—CH=CH2.
Figure 3
Figure 3
Reaction conditions. (a) Alkene (1.2 mmol, 1.0 equiv), FeBr2 (0.3 equiv), TMSBr (3.0 equiv), CH2Cl2 (0.1 M), O2 (present in the air, the solvent, and H2O from moisture). (b) Scope and yields of the Markovnikov hydrobromination of alkenes. (c) The Markovnikov orientation in allyl benzene.
Figure 4
Figure 4
Proposed mechanisms for the anti-Markovnikov and Markovnikov hydrobromination.
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References

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