Copper hydride
Recent Literature
Optimizations to generate CuH in situ have led to an efficient and
inexpensive hydrosilylation method for dialkyl ketones.
B. H. Lipshutz, C. C. Caires, P. Kuipers, W. Chrisman, Org. Lett., 2003, 5, 3085-3088.
A complex of CuH and Takasago's nonracemic ligand, DTBM-SEGPHOS, is an
especially reactive reagent for asymmetric hydrosilylation of
heteroaromatic ketones under very mild conditions. PMHS serves as an
inexpensive source of hydride for the in situ generation of CuH.
B. H. Lipshutz, A. Lower, K. Noson, Org. Lett., 2002, 4, 4045-4048.
The use of (R)-(−)-(DTBM-SEGPHOS)CuH effects a highly enantioselective
1,2-hydrosilylation of prochiral diaryl ketones to yield nonracemic
diarylmethanols in excellent yields.
C.-T. Lee, B. H. Lipshutz, Org. Lett.,
2008,
10, 4187-4190.
Asymmetric ligand-accelerated catalysis by copper hydride allows the synthesis
of valued nonracemic allylic alcohols in very good yields.
R. Moser, Ž. V. Bošković, C. S. Crowe, B. H. Lipshutz, J. Am. Chem. Soc., 2010,
132, 7852-7853.
A ligand-modified, economical version of Stryker's reagent is based on a
bidentate, achiral bis-phosphine. Generated in situ, “(BDP)CuH” smoothly effects
conjugate reductions of a variety of unsaturated substrates, including those
that are normally unreactive toward Stryker's reagent.
B. A. Baker, Ž. V. Bošković, B. H. Lipshutz, Org. Lett., 2008,
10, 289-292.
Taking advantage of micellar catalysis in water, asymmetric hydrosilylation
reactions can be conducted at ambient temperatures using water as the global
medium.
S. Huang, K. R. Voigtritter, H. B. Unger, B. H. Lipshutz, Synlett, 2010,
2041-2044.
A complex of catalytic amounts of CuH with a nonracemic JOSIPHOS or SEGPHOS
ligand leads to exceedingly efficient and
highly enantioselective 1,4-reductions of α,β-disubstituted enoates and
lactones using PMHS as the stoichiometric reducing agent.
B. H. Lipshutz, J. M. Servesko, B. R. Taft, J. Am. Chem. Soc., 2004, 126, 8352-8353.
Catalytic amounts of copper hydride ligated by a nonracemic SEGPHOS
ligand leads in situ to an extremely reactive species capable of
effecting asymmetric hydrosilylations of conjugated cyclic enones with
very high enantioselectivity.
B. H. Lipshutz, J. M. Servesko, T. B. Petersen, P. P. Papa, A. A. Lover, Org. Lett., 2004, 6, 1273-1275.
Treatment of β,β-disubstituted-α,β-unsaturated ketones bearing a ketone residue
with in situ generated, catalytic CuH ligated by a nonracemic ligand leads to
cyclic aldol products with three newly created adjacent chiral centers.
Excellent diastereoselectivities and enantioselectivities are obtained for
several examples studied.
B. H. Lipshutz, B. Amorelli, J. B. Unger, J. Am. Chem. Soc., 2008,
130, 14378-14379.
A copper hydride-catalyzed SN2′-reduction of propargylic carbonates
provides functionalized allenes in good yields. The method takes advantage of
the stabilizing effect of NHC ligands on CuH and offers high reactivity,
stereoselectivity, and functional group tolerance.
C. Deutsch, B. H. Lipshutz, N. Krause, Org. Lett., 2009,
11, 5010-5012.
A novel process for the efficient, enantioselective hydrosilylation of
ketimines based on catalytic amounts of copper hydride, (R)-DTBM-SEGPHOS,
and an inexpensive silane (tetramethyldisiloxane, TMDS) has been developed.
The resulting products are converted to their free-base form upon mild
hydrolysis.
B. H. Lipshutz, H. Shimizu, Angew. Chem. Int. Ed., 2004,
43, 2228-2230.
A highly enantioselective reduction of α,β-unsaturated nitriles can be
conducted by using a Cu(OAc)2/josiphos complex as the catalyst under
hydrosilylation conditions. The reaction provides access to valuable
β-aryl-substituted chiral nitriles in good yields and with excellent
enantioselectivities.
D. Lee, D. Kim, S. Yun, Angew. Chem. Int. Ed., 2006,45, 2785-2787.
A range of 3-aryl-3-pyridylacrylonitriles were reduced with high levels of
enantioselectivity under optimal conditions employing a copper/Josiphos complex
in the presence of polymethylhydrosiloxane (PMHS).
D. Lee, Y. Yang, J. Yun, Org. Lett., 2007,
9, 2749-2751.
Cu-catalyzed asymmetric conjugate reduction of
β-substituted ketones leads to enantiomerically enriched
diphenylsilyl enol ethers, which are utilized in a diastereoselective Pd-catalyzed
α-arylation of various aryl bromides to yield disubstituted cycloalkanones with
excellent levels of enantiomeric and diastereomeric purity. The procedure can be
carried out in one-pot.
J. Chae, J. Yun, S. L. Buchwald, Org. Lett., 2004, 6, 4809-4812.
