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. 2017 Jul 12;139(27):9148-9151.
doi: 10.1021/jacs.7b05149. Epub 2017 Jun 30.

Enantioselective Rhodium(III)-Catalyzed Markovnikov Hydroboration of Unactivated Terminal Alkenes

James R Smith  1 , Beatrice S L Collins  1 , Matthew J Hesse  1 , Mark A Graham  2 , Eddie L Myers  1 , Varinder K Aggarwal  1
Affiliations

Enantioselective Rhodium(III)-Catalyzed Markovnikov Hydroboration of Unactivated Terminal Alkenes

James R Smith et al. J Am Chem Soc. .

Abstract

We report the first enantioselective Rh-catalyzed Markovnikov hydroboration of unactivated terminal alkenes. Using a novel sp2-sp3 hybridized diboron reagent and water as a proton source, a broad range of alkenes undergo hydroboration to provide secondary boronic esters with high regio- and enantiocontrol.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1. Diverting Diboration into Hydroboration
Scheme 2
Scheme 2. Scope of the Hydroboration Reaction
Reactions were conducted with 0.38 mmol of 2. Quoted yields are those of isolated product and are based on an average of values obtained from two experiments. Regioselectivity (rr) was determined by GC–MS analysis of the crude reaction mixtures, unless otherwise stated. Enantioselectivity (er) was determined by either chiral HPLC, SFC or GC analysis following oxidation (and in some cases further derivatization–see SI) of the isolated products (3), unless otherwise stated. Determined by 1H NMR analysis of the crude reaction mixture. Determined by chiral SFC or HPLC analysis of the boronic ester (3). Alcohol 3i was obtained following an oxidative work up using H2O2/NaOH. Determined by LCMS analysis of the crude reaction mixture.
Scheme 3
Scheme 3. Hydroboration of an Enantioenriched Substrate
Determined by GCMS analysis of the crude reaction mixture. Determined by 13C NMR analysis of isolated material.
Scheme 4
Scheme 4. Mechanistic Studies
See this image and copyright information in PMC

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