PMHS, Polymethylhydrosiloxane
Polymethylhydrosiloxane (PMHS) - a byproduct of the silicone industry - is a cheap, easy to handle, and environmentally friendly reducing agent. PMHS is more air and moisture stable than other silanes and can be stored for long periods of time without loss of activity.
Recent Literature
An efficient methodology for the reductive alkylation of secondary amines
with aldehydes and Et3SiH using an iridium complex as a catalyst
has been developed. In addition, a cheaper, easy-to-handle, and
environmentally friendly reducing reagent such as polymethylhydrosiloxane
(PMHS) in place of Et3SiH was also useful.
T. Mizuta, S. Sakaguchi, Y. Ishii, J. Org. Chem., 2005, 70, 2195-2199.
An efficient, directed reductive amination of β-hydroxy-ketones allows the
stereoselective preparation of 1,3-syn-amino alcohols using Ti(iOPr)4
for coordination of the intermediate imino alcohol and PMHS as the reducing
agent.
D. Menche, F. Arikan, J. Li, S. Rudolph, Org. Lett., 2007,
9, 267-270.
Palladium-catalyzed reduction of aromatic nitro groups to amines can be
accomplished in high yield, with wide functional group tolerance and short
reaction times at r.t. using aqueous potassium fluoride and
polymethylhydrosiloxane (PMHS) for aromatic nitro groups. Aliphatic nitro
compounds are reduced to the corresponding hydroxylamines using
triethylsilane instead of PMHS/KF.
R. J. Rahaim, R. E. Maleczka, Jr., Org. Lett., 2005, 7, 5087-5090.
A highly chemoselective conjugate reduction of
electron-deficient Michael acceptors, including α,β-unsaturated ketones,
carboxylic esters, nitriles and nitro compounds with PMHS in the presence of
a catalytic amount of B(C6F5)3 is described.
S. Chandrasekhar, G. Chandrasekhar, M. S. Reddy, P. Srihari, Org. Biomol. Chem., 2006, 4, 1650-1652.
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.
A complex of CuH and Takasago's nonracemic ligand, DTBM-SEGPHOS, is an
especially reactive reagent for the 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.
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.
Deprotection of allyl ethers, amines and esters to liberate hydroxyl,
amino and acid groups is achieved under mild conditions. The reagent
combination employed for this transformation is polymethylhydrosiloxane
(PMHS), ZnCl2 and Pd(PPh3)4.
S. Chandrasekhar, R. Reddy, R. J. Rao, Tetrahedron, 2001, 57, 3435-3438.
Polymethylhydrosiloxane (PMHS) under Pd(0) catalysis can efficiently reduce
aryl acid chlorides to their corresponding aldehydes in the presence of
fluoride without requiring an additional reductant.
K. Lee, R. E. Maleczka, Jr., Org. Lett., 2006, 8, 1887-1888.
An efficient, palladium-catalyzed reduction of N-(tert-butoxycarbonyl)indoles
gives N-(tert-butoxycarbonyl)indolines in good yields in the presence of
polymethylhydrosiloxane (PMHS) as reducing agent at room temperature.
S. Chandrasekhar, D. Basu, C. R. Reddy, Synthesis, 2007,
1509-1512.
