Organic Letters
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To probe the mechanism of this hydroboration reaction, the
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D-2c and 2c in 71% combined yield with 10/1 ratio of D-2c/2c
(eq 6).14 There is a possibility of an alkene insertion into the
iron-hydride species and the occurrence of β-hydride elimination
during this transformation. More experimental and computa-
tional studies should be further performed to gain an accurate
understanding of the origin of the high regioselectivity.
In summary, we report an iron-catalyzed, highly Markovnikov-
selective hydroboration of styrenes using readily available
oxazolinylphenyl picolinamide ligands. A variety of styrenes
bearing both electron-donating group and electron-withdrawing
groups are suitable for this reaction system to be converted
to the branched alkylboronates in excellent regioselectivities
(>50/1 b/l in most cases). This amide-based tridentate ligand
shows a unique property for an efficient Markovnikov selectivity.
The oxazolinyl moiety also offers the possibility for asymmetric
transformation by introducing chirality. The asymmetric reaction
is being studied in our laboratory.
ASSOCIATED CONTENT
* Supporting Information
■
S
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The Supporting Information is available free of charge on the
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Experimental details, characterization data of all com-
pounds, and copies of 1H and 13C NMR spectra (PDF)
AUTHOR INFORMATION
■
Corresponding Author
ORCID
Notes
The authors declare no competing financial interest.
(13) (a) Wolinska, E. Tetrahedron 2013, 69, 7269−7278. (b) Decken,
A.; Gossage, R. A.; Yadav, P. N. Can. J. Chem. 2005, 83, 1185−1189.
(14) The reaction of D8-styrene with HBpin was presented in SI.
ACKNOWLEDGMENTS
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We thank the NSFC (21472162), the National Basic Research
Program of China (2015CB856600), and Zhejiang University for
financial support.
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