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.
Stannous chloride catalyzes a chemoselective reductive amination of various carbonyl compounds with aromatic amines using inexpensive polymethylhydrosiloxane as reducing agent in methanol. The present method is applicable for the synthesis of tertiary and secondary amines.
O. S. Nayal, V. Bhatt, S. Sharma, N. Kumar, J. Org. Chem., 2015, 80, 5912-5918.
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.
Copper N-heterocyclic carbene complexes serve as catalysts for both aerobic oxidation of alcohols to aldehydes and reduction of imines to amines. A one-pot tandem synthetic strategy affords useful secondary amines from benzylic alcohols and anilines via an oxidation-reduction strategy.
L.-W. Zhan, L. Han, P. Xing, B. Jiang, Org. Lett., 2015, 17, 5990-5993.
A copper-catalyzed ring-opening hydroamination of methylenecyclopropanes with polymethylhydrosiloxane and O-benzoylhydroxylamines provides homoallylamines in very good yields. The cyclopropane C-C bond cleavage occurs selectively at the more congested proximal position.
D. Nishikawa, R. Sakae, Y. Miki, K. Hirano, M. Miura, J. Org. Chem., 2016, 81, 12128-12134.
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.
Ketones can efficiently be reduced to the corresponding methylene compound using the convenient and inexpensive combination of PMHS and FeCl3.
C. Dal Zotto, D. Virieux, J.-M. Campagne, Synlett, 2009, 276-278.
Catalytic Pd(OAc)2 and polymethylhydrosiloxane (PMHS) effects the chemo-, regio-, and stereoselective deoxygenation of benzylic oxygenated substrates in the presence of aqueous KF and a catalytic amount of an aromatic chloride involving palladium-nanoparticle-catalyzed hydrosilylation followed by C-O reduction. The chloroarene facilitates the hydrogenolysis through the slow controlled release of HCl.
R. J. Rahaim, Jr., R. E. Maleczka, Jr., Org. Lett., 2011, 13, 584-587.
Diethylzinc (Et2Zn) is an efficient and chemoselective catalyst for the reduction of tertiary amides under mild reaction conditions employing polymeric silane (PMHS) as a cost-effective hydride source. Crucial for the catalytic activity was the addition of a substoichiometric amount of lithium chloride. A series of amides containing different additional functional groups were reduced to their corresponding amines in very good yields.
O. O. Kovalenko, A. Volkov, H. Adolfsson, Org. Lett., 2015, 17, 446-449.
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.
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.
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.
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.
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.
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.
Using small amounts of a copper catalyst, an efficient semireduction of alkynes can be accomplished with a wide range of substrates, including both internal and terminal alkynes without over-reduction. The new method has excellent chemoselectivity and tolerates nitro and aryl iodo groups. Finally, commercial availability of a catalyst precursor adds to the appeal of the new catalytic system.
A. M Whittaker, G. Lalic, Org. Lett., 2013, 15, 1112-1115.
The hydroallylation of terminal alkyl and aryl alkynes with simple allyl phosphates and 2-substituted allyl phosphates provides skipped dienes. The hydroallylation of functionalized internal alkynes enables the synthesis of complex trisubstituted alkenes.
M. Mailig, A. Hazra, M. K. Armstrong, G. Lalic, J. Am. Chem. Soc., 2017, 139, 6969-6977.
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 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.
The use of various o-phenylenediamines and N-substituted formamides as C1 sources in a zinc-catalyzed cyclization in the presence of poly(methylhydrosiloxane) provides benzimidazoles in good yields. Benzoxazole and benzothiazole derivates can also be synthesized.
D. B. Nale, B. M. Bhanage, Synlett, 2015, 26, 2831-2834.
A silane-promoted nickel-catalyzed amination of aryl chlorides with a catalytic amount of Ni(acac)2 and 3,5,6,8-tetrabromo-1,10-phenanthroline as ligand in the presence of polymethylhydrosiloxane gives the desired (het)arylamines in good yields. The reaction is sensitive to the nature and amount of the silane promoter.
G. Manolikakes, A. Gavryushin, P. Knochel, J. Org. Chem., 2008, 73, 1429-1434.