ORGANIC
LETTERS
2010
Vol. 12, No. 19
4348-4351
Ni(0)-Catalyzed 1,4-Selective Diboration
of Conjugated Dienes
Robert J. Ely and James P. Morken*
Department of Chemistry, Merkert Chemistry Center, Boston College,
Chestnut Hill, Massachusetts 02467
Received August 2, 2010
ABSTRACT
A catalytic stereoselective 1,4-diboration of conjugated dienes with B2(pin)2 was accomplished with Ni(cod)2 and PCy3 as the catalyst. This
reaction broadens the substrate scope of current methods for catalytic diene diboration by including internal and sterically hindered dienes,
and it proceeds efficiently at low catalyst loadings. The intermediate allylboronate was oxidized to the stereodefined allylic 1,4-diol.
The catalytic diboration of unactivated unsaturated hydro-
carbons can be accomplished with many transition metals
including Pt, Pd, Rh, Cu, Au, and Ag.1 The 1,4-diboration
of 1,3-dienes, in particular, allows for the transformation of
simple hydrocarbons to synthetically useful allylic diboronate
intermediates.2 Recently, we developed the first catalytic
enantioselective version of this type of diboration. This
reaction employs a platinum catalyst in conjunction with
chiral TADDOL-derived phosphonite ligands and delivers
the 1,4-diborylated product in high enantiomeric excess.3 The
resultant bis(boronate) esters can be utilized in carbonyl
allylation and, through appropriate oxidation strategies, can
be converted to butenolides and 2-alkene-1,4-diols. A current
limitation of both the enantioselective and the nonenanti-
oselective processes is that they have only been demonstrated
with terminal dienes or cyclic dienes and require the use of
moderately expensive catalyst precursors. In this publication,
we address these issues and describe a convenient, inexpen-
sive catalytic diene diboration that operates on an expanded
substrate scope.
During development of the Ni-catalyzed borylative cou-
pling of dienes and aldehydes,4 we found that Ni(cod)2, in
the presence of tricyclohexylphosphine, promotes the 1,4-
diboration of a 1,3-diene by bis(pinacolato)diboron (B2(pin)2).
The fact that the reaction delivered a single regio- and
stereoisomer of product and that it employed a simple
inexpensive catalyst and reagents prompted us to further
study this transformation. Our investigation of the reaction
began with a brief analysis of ligand effects in the reaction.
As depicted in Scheme 1, the diboration of trans-1,3-
decadiene was examined in the presence of 2.5 mol %
Ni(cod)2 and a near-stoichiometric quantity of B2(pin)2. This
survey revealed that strongly donating monodentate phos-
phine ligands, including both PCy3 and hexamethylphos-
phorous triamide (HMPT),5 are highly effective in the
reaction and after only 15 min catalyze complete conversion
to the 1,4-bis(boronate) product; oxidation delivered the (Z)-
2-alkene-1,4-diol in good yield.
(1) (a) For a review of Pt- and Rh-catalyzed diboration: Norman, N. C.;
Marder, T. B. Top. Catal. 1998, 5, 63. For Pd: (b) Yang, F. Y.; Cheng, H.
J. Am. Chem. Soc. 2001, 123, 761. (c) Woodward, A. R.; Burks, H. E.;
Sieber, J. D.; Morken, J. P. J. Am. Chem. Soc. 2004, 126, 16328. (d) Lillo,
V.; Mas-Marza´, E.; Segarra, A.; Carbo´, J. J.; Bo, C.; Peris, E.; Fernandez,
E. Chem. Commun. 2007, 3380. For Cu: (e) Lillo, V.; Fructos, M. R.; Braga,
A. A. C.; Maseras, F.; Reguejo, M. M.; Pe´rez, P. J.; Fernandez, E.
Chem.sEur. J. 2007, 13, 2614. (f) Lee, Y.; Jang, H.; Hoveyda, A. H. J. Am.
Chem. Soc. 2009, 131, 16630. For Au: (g) Baker, R. T.; Nguyen, P.; Marder,
T. B.; Westcott, S. A. Angew. Chem., Int. Ed. 1995, 34, 1336. (h) Corberan,
R.; Ramirez, J.; Sanau, M.; Peris, E.; Fernandez, E. Tetrahedron: Asymmetry
2006, 17, 1759. (i) Ramirez, J.; Sanau, M.; Fernandez, E. Angew. Chem.,
Int. Ed. 2008, 47, 5194. For Ag: (j) Corberan, R.; Ramirez, J.; Poyatos,
M.; Peris, E.; Fernandez, E. Chem. Commun. 2005, 3056.
(2) (a) Ishiyama, T.; Yamamoto, M.; Miyaura, N. Chem. Commun. 1996,
2073. (b) Clegg, W.; Thorsten, J.; Marder, T. B.; Norman, N. C.; Orpen,
A. G.; Peakman, T. M.; Quayle, M. J.; Rice, C. R.; Scott, A. J. J. Chem.
Soc., Dalton Trans. 1998, 1431.
(4) Cho, H. Y.; Morken., J. P. J. Am. Chem. Soc. 2008, 130, 16140.
(5) For an excellent description of the electronic properties of HMPT,
see: Moloy, K. G.; Petersen, J. L. J. Am. Chem. Soc. 1995, 117, 7696.
(3) Burks, H. E.; Kliman, L. T.; Morken, J. P. J. Am. Chem. Soc. 2009,
131, 9134.
10.1021/ol101797f 2010 American Chemical Society
Published on Web 09/09/2010