10.1002/anie.201806169
Angewandte Chemie International Edition
COMMUNICATION
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We then demonstrated further utility by sequentially
elaborating each functional group in 3a, the product of the PCy3
method, enroute to the hypnotic sedative glutethimide[28]
(Scheme 4B). Thus, boronic ester 3a was homologated twice,[26]
oxidized to the carboxylic acid, cyclized, and finally
hydrogenated to give the target glutethimide.
In conclusion, we have discovered a simple strategy for the
regiodivergent multi-functionalization of 1,3-dienes and applied it
to a borocyanation process that delivers high value products. In
utilizing the bidentate ligand XantPhos, 2-substiuted 1,3-dienes
underwent copper catalyzed 4,1-borocupration. Upon switching
to the monodentate phosphine, PCy3, unprecedented 1,4-
borocupration occurred. The catalytically generated allyl copper
intermediates in both processes were successfully trapped with
excellent regioselectivity using the readily available cyanating
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agents,
N-cyano
sulfonamides,
to
produce
densely
functionalized and versatile 4,3- or 1,2-borocyanated products.
We envisage that this ligand controlled regiodivergent strategy
may be applied in other copper catalyzed processes involving
dienes.
Acknowledgements
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dienes, see: a) V. Liepins, J.-E. Bäckvall, Eur. J. Org. Chem. 2002,
3527; b) T. Iwasaki, R. Shimizu, R. Imanishi, H. Kuniyasu, N. Kambe,
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L.−L. Liao, T. Ju, J.-H. Ye, Z. Zhang, J. Li, D.-G. Yu, J. Am. Chem. Soc.
2017, 139, 17011.
We thank the EPSRC (EPSRC Established Career Fellowship to
D. J. P.), the Royal Society (Newton International Fellowship to
T.J.), the BBSRC (DTP Studentship to R.E.R.) and the
University of Manchester (Lectureship to A.P.P).
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dienes, see: a) H. E. Burks, L. T. Kliman, J. P. Morken, J. Am. Chem.
Soc. 2009, 131, 9134; b) R. J. Ely, J. P. Morken, J. Am. Chem. Soc.
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Keywords: copper • boron • multicomponent reactions •
catalysis • regioselectivity
[12] For examples of in situ generated allyl coppers, see references 3f, 6, 7,
8, 9, and for a recent example, see: E. Y. Tsai, R. Y. Liu, Y. Yang, S. L.
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[18] (E)-1-Phenylbuta-1,3-diene gave 4-borylated products under both
XantPhos and PCy3 conditions, and (E,E)-1,4-diphenylbuta-1,3-diene
did not react. See Supporting Information for more details and for
further optimization studies, including ligands, copper sources, diborane
reagents, and a variety of NCTS derived cyanating agents.
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