Categories: C-H Bond Formation >
Direct electrolysis of primary alcohols leads smoothly to the formation of the corresponding deoxygenated product in high yield in the presence of methyl toluate.
K. Lam, I. E. Markő, Synlett, 2012, 23, 1235-1239.
Whereas an Ir-catalyzed alcohol deoxygenation on basis of dehydrogenation/Wolff-Kishner reduction is efficient mainly with activated alcohols under harsh reaction conditions, a Ru-catalyzed aliphatic primary alcohol deoxygenation offers good functional group tolerance and excellent efficiency under practical reaction conditions. Its synthetic utility is further illustrated by complete chemo- and regio-selectivity in complex molecular settings.
X.-J. Dai, C.-J. Li, J. Am. Chem. Soc., 2016, 138, 5344-5440.
Primary alcohols and ethers were effectively reduced to the corresponding hydrocarbons by HSiEt3 in the presence of catalytic amounts of B(C6F5)3. Secondary alkyl ethers are cleaved under similar reaction conditions to produce silyl ethers or alcohols upon subsequent deprotection with TBAF. The following relative reactivity order of substrates was found: primary >> secondary > tertiary.
V. Gevorgyan, M. Rubin, S. Benson, J.-X. Liu, Y. Yamamoto, J. Org. Chem., 2000, 65, 6179-6168.
Primary alcohols can be deoxygenated cleanly and in good yields by reduction of derived diphenyl phosphate esters with lithium triethylborohydride in THF at room temperature. Primary alcohols can selectively be reduced in the presence of secondary alcohols. An additional one pot two-step process makes the process simple and convenient.
S. Chowdhury, R. F. Standaert, J. Org. Chem., 2016, 81, 9957-9963.
A direct reduction of alcohols to the corresponding alkanes using chlorodiphenylsilane as hydride source in the presence of a catalytic amount of InCl3 showed high chemoselectivity for benzylic alcohols, secondary alcohols and tertiary alcohols while not reducing primary alcohols and functional groups that are readily reduced by standard methods such as esters, chloro, bromo, and nitro groups.
M. Yasuda, Y. Onishi, M. Ueba, T. Miyai, A. Baba, J. Org. Chem., 2001, 7741-7744.
Mitsunobu displacement of an alcohol with o-nitrobenzenesulfonylhydrazide followed by in situ elimination of o-nitrobenzenesulfinic acid generates monoalkyl diazenes, which decompose by a free-radical mechanism to form deoxygenated products.
A. G. Myers, M. Movassaghi, B. Zheng, J. Am. Chem. Soc., 1997, 119, 8572-8573.
Proper solvent selection between Cl(CH2)2Cl and CF3CH2OH was the key to high yields in a deoxygenation of propargyl alcohols in the presence of Et3SiH and H3[PW12O40]ˇnH2O as catalyst. Under similar conditions, the deoxygenation of allyl alcohols proceeded to give thermodynamically stable alkenes with migration of the double bonds in good yields.
M. Egi, T. Kawai, M. Umemura, S. Akai, J. Org. Chem., 2012, 77, 7092-7097.
Treatment of 1,2-O-isopropylidenefuranose derivatives with triethylsilane/boron trifluoride etherate provides tetrahydrofurans. The removal of the 1,2-O-isopropylidene group is accompanied by deoxygenation at the anomeric position. This process is compatible with several hydroxyl protecting groups.
G. J. Ewing, M. J. Robins, Org. Lett., 1999, 1, 635-636.
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.
In the presence of a phenol ligand, a cationic ruthenium hydride complex exhibited high catalytic activity for the hydrogenolysis of carbonyl compounds to yield the corresponding aliphatic products. The reaction showed exceptionally high chemoselectivity toward the carbonyl reduction over alkene hydrogenation.
N. Kalutharage, C. S. Yi, J. Am. Chem. Soc., 2015, 137, 11105-11114.
A tandem catalyst composed of heterogeneous Pd/TiO2 + homogeneous FeCl3 enables a rapid and practical protocol for the chemoselective deoxygenation of various aromatic ketones and aldehydes using polymethylhydrosiloxane (PMHS) as a green hydrogen source.
Z. Dong, J. Yuan, Y. Xiao, P. Mao, W. Wang, J. Org. Chem., 2018, 83, 11067-11073.
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.
A pyridinylidene carbene dimer effects reductive cleavage of C-O σ-bonds in acyloin derivatives, which represents the first cleavage of C-O σ-bonds by a neutral organic electron-donor. The methodology is applicable to a large array of substrates and the reduced products were isolated in good to excellent yields.
S. P. Y. Cutulic, N. J. Findlay, S.-Z. Zhou, E. J. T. Chrystal, J. A. Murphy, J. Org. Chem., 2009, 74, 8713-8718.
A sequential installation of a carbenoid and a hydride into a carbonyl provides halomethyl alkyl derivatives with uniformly high yields and chemocontrol. The tactic is flexible and is not limited to carbenoids. Also, diverse carbanion-like species can act as nucleophiles.
M. Miele, A. Citarella, T. Langer, E. Urban, M. Zehl, W. Holzer, L. Ielo, V. Pace, Org. Lett., 2020, 22, 7629-7634.
Acetates of benzoin derivatives can be effectively reduced using catalytic amounts of [Ru(bpy)3]Cl2 as photoredox catalyst in combination with Hantzsch ester and triethylamine as a sacrificial electron donor. This mild and operationally simple method is applicable to a broad range of substrates providing deoxygenated counterparts in good yields.
E. Speckmeier, C. Padié, K. Zeitler, Org. Lett., 2015, 17, 4818-4821.
A combination of chlorotrimethylsilane with NaI enables a selective reduction of several unsymmetrically benzil derivatives in good yields at room temperature. Identification of benzoin intermediates is achieved, and a mechanistic radical process is proposed.
L.-Z. Yuan, D. Renko, I. Khelifi, O. Provot, J.-D. Brion, A. Hamze, M. Alami, Org. Lett., 2016, 18, 3238-3241.
An electrochemical reduction of diphenylphosphinate esters leads smoothly and in high yields to the corresponding deoxygenated products. The electrolysis could be performed at low temperature and with a high current density, resulting in a short reaction time.
K. Lam, I. E. Markó, Org. Lett., 2011, 13, 406-409.
An efficient and economical electrolysis of toluate esters leads smoothly to the corresponding deoxygenated alcohols while a wide variety of functionalities are tolerated. In contrast to previous methods, unstable xanthates, expensive metals and toxic co-solvents are no longer required.
K. Lam, I. E. Markó, Chem. Commun., 2009, 95-97.
A new, easy and versatile methodology for the deoxygenation of alcohols via the corresponding toluates offers a broad scope using simple and commercially available reagents such as toluolyl chloride and samarium(II) iodide. In addition, this methodology is also useful for radical cyclizations directly from toluate precursors.
K. Lam, I. E. Markó, Org. Lett., 2008, 10, 2919-2922.
The reduction of a series of alkyl sulfonates to the corresponding hydrocarbons was efficiently performed using a reducing system composed of CuCl2ˇ2H2O, an excess of lithium sand and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB), in tetrahydrofuran at room temperature. The process was also applied to enol and dienol triflates affording alkenes and dienes, respectively.
G. Radivoy, F. Alonso, Y. Moglie, C. Vitale, M. Yus, Tetrahedron, 2005, 61, 3859-3864.
Aliphatic carboxyl derivatives (acids, acyl chlorides, esters) and aldehydes were efficiently reduced to the methyl group by HSiEt3 in the presence of catalytic amounts of B(C6F5)3.
V. Gevorgyan, M. Rubin, J.-X. Liu, Y. Yamamoto, J. Org. Chem, 2001, 66, 1672-1675.
A new convenient and scalable synthesis of phenylacetic acids via iodide catalyzed reduction of mandelic acids relies on in situ generation of hydroiodic acid from catalytic sodium iodide, employing phosphorus acid as the stoichiometric reductant.
J. E. Milne, T. Storz, J. T. Colyer, O. R. Thiel, M. D. Seran, R. D. Larsen, J. A. Murry, J. Org. Chem., 2011, 76, 9519-9524.
Salicylic acids and alcohols can be reduced to 2-methylphenols by a simple two steps procedure. Reaction conditions were optimized carrying out a study on the solvent effect and the amount of the reducing agent. The improved procedure resulted particularly useful in the synthesis of deuterated building blocks of biological interest.
F. Mazzini, P. Salvadori, Synthesis, 2005, 2479-2481.
An indium(III) hydroxide-catalyzed reaction of carbonyls and chlorodimethylsilane afforded the corresponding deoxygenative chlorination products. Ester, nitro, cyano, or halogen groups were not affected during the reaction course. Typical Lewis acids such as TiCl4, AlCl3, and BF3ˇOEt2 showed no catalytic activity. The reaction mechanism is discussed.
Y. Onishi, D. Ogawa, M. Yasuda, A. Baba, J. Am. Chem. Soc., 2002, 124, 13690-13691.