In the presence of Co(PPh3)2I2, PPh3, water, and zinc powder, the reductive coupling of alkynes with alkenes having an electron-withdrawing substituent proceeded smoothly in acetonitrile to give the corresponding reductive coupling products in fair to excellent yields. Possible mechanisms for this highly regio- and stereoselective ene-yne reaction are proposed.
C.-C. Wang, P.-S. Lin, C.-H. Cheng, J. Am. Chem. Soc., 2002, 124, 9696-9697.
A nonionic amphiphile enables a simple approach to Pd-catalyzed stereoselective sp3-sp2 cross-couplings between alkyl and alkenyl bromides in the presence of zinc powder in water to give coupled products in good yields without prior formation of the organozinc reagents. The reaction is conducted at room temperature and tolerates various functional groups.
A. Krasovskiy, C. Duplais, B. H. Lipshutz, Org. Lett., 2010, 12, 4742-4744.
Zn-Mediated, Pd-Catalyzed Cross-Couplings in Water at Room Temperature Without Prior Formation of Organozinc Reagents
A. Krasovskiy, C. Duplais, B. H. Lipshutz, J. Am. Chem. Soc., 2009, 131, 15592-15593.
In the presence of a Ni catalyst and Zn, various aryl and vinyl bromides are reductively coupled with alkyl bromides in high yields. Under similar conditions, activated aryl chlorides can also be coupled with bromoalkanes. The protocols are highly functional-group tolerant, and the reactions are assembled on the benchtop with no special precautions to exclude air or moisture.
D. A. Everson, B. A. Jones, D. J. Weix, J. Am. Chem. Soc., 2012, 134, 6146-6159.
A room-temperature Ni-catalyzed reductive coupling of aryl bromides with secondary alkyl bromides provides products in good to excellent yields. Slight modification of this protocol allows efficient coupling of activated aryl chlorides with cyclohexyl bromide and aryl bromides with allylic acetate.
S. Wang, Q. Qian, H. Gong, Org. Lett., 2012, 14, 3352-3355.
Simple and mild indium- and zinc-mediated dehalogenation reactions of vicinal dihalides in an aqueous solvent enable the synthesis of various allenylmethyl aryl ethers and monosubstituted allenes in very good yields.
M.-H. Lin, W.-S. Tsai, L.-Z. Lin, S.-F. Hung, T.-H. Chuang, Y.-J. Su, J. Org. Chem., 2011, 76, 8518-8523.
A NiCl2(DME)/dppp/Zn system catalyzed an intermolecular insertion of aryl iodides to nitriles to afforded variously substituted arylketone derivatives in good yields with tolerance of a wide variety of functional groups.
J.-C. Hsieh, Y.-C. Chen, A.-Y. Cheng, H.-C. Tseng, Org. Lett., 2012, 14, 1282-1285.
A Mannich-like zinc-mediated three-component reaction of aromatic halides, amines, and paraformaldehyde allows the straightforward synthesis of a range of functionalized tertiary benzylamines. This procedure involves the in situ formation of arylzinc reagents.
E. Le Gall, A. Decompte, T. Martens, M. Troupel, Synthesis, 2010, 249-254.
A straightforward three-component reaction of preformed aromatic or in situ generated benzylic organozinc reagents with amines and ethyl glyoxylate allows the synthesis of a range of α-amino esters in very good yields. The procedure, which is characterized by its simplicity, allows the concise synthesis of esters bearing a phenylglycine or a phenylalanine scaffold.
C. Haurena, E. Le Gall, S. Sengmany, T. Martens, M. Troupel, J. Org. Chem., 2010, 75, 2645-2650.
In acetonitrile as solvent and in the presence of a simple cobalt halide as catalyst, the reduction by zinc dust of a mixture of aldehydes or ketones and allylic acetates affords the corresponding homoallylic alcohols in good yields.
P. Gomes, C. Gosmini, J. Périchon, Synthesis, 2003, 1909-1915.
A rapid and efficient procedure for the solvent-free synthesis of homoallylic and homopropargyl alcohols has been achieved by zinc-mediated Barbier-type reaction of carbonyl compounds at room temperature.
J.-X. Wang, X. Jia, T. Meng, L. Xin, Synthesis, 2005, 2669-2672.
A highly α-regioselective prenylation of imines enables the conversion a wide range of substrates including N- and C-aryl aldimines, N-alkyl aldimines, C-alkyl aldimines, and N- and C-aryl ketimines. The approach uses prenyl bromide as prenyl source and inexpensive zinc as mediator as well as environmentally benign 1,3-dimethyl-2-imidazolidinone (DMI) as solvent.
L.-M. Zhao, S.-Q. Zhang, H.-S. Jin, L.-J. Wan, F. Dou, Org. Lett., 2012, 14, 886-889.
Titanocene dichloride catalyzes the formation of an organozinc species via catalytic activation of allyl halides. Nucleophilic addition to carbonyl derivatives provides the desired homoallylic alcohols in very good yields in short reaction times. This discovery will have wide ranging applicability in the generation of highly reactive organometallic reagents.
L. M. Fleury, B. L. Ashfeld, Org. Lett., 2009, 11, 5670-5673.
Zinc-promoted reduction of 2-(bromomethyl)alkenoates derived from Baylis–Hillman adducts gave (E)-2-methylacrylates in good yield and high stereoselectivity. Synthesis of the male ant pheromone (E)-2,4-dimethyl-2-hexenoic acid was performed using this simple methodology.
L. Fernandes, A. J. Bortoluzzi, M. M. Sa, Tetrahedron, 2004, 60, 9983-9989.
An efficient cobalt-catalyzed reductive coupling reaction of alkyl halides with alkenes bearing electron-withdrawing groups in the presence of water and zinc powder in acetonitrile gave the corresponding Michael-type addition products in high yields. The mechanism is discussed.
P. Shukla, Y.-C. Hsu, C.-H. Cheng, J. Org. Chem., 2006, 71, 655-658.
Cobalt complex/Zn systems effectively catalyze the reductive coupling of activated alkenes with alkynes in the presence of water to give substituted alkenes with very high regio- and stereoselectivity in excellent yields.
H.-T. Chang, T. T. Jayanth, C.-C. Wang, C.-H. Cheng, J. Am. Chem. Soc., 2007, 129, 12032-12041.
A range of polysubstituted allylic zinc chlorides were obtained in good yield using a LiCl-mediated zinc dust insertion in polysubstituted allylic chlorides. A highly diastereoselective synthesis of homoallylic alcohols bearing up to two adjacent quaternary centers by the addition of polysubstituted allylic zinc reagents to carbonyl compounds.
H. Ren, G. Dunet, P. Mayer, P. Knochel, J. Am. Chem. Soc., 2007, 129, 5376-5377.
A dizinc reagent, which acts as an effective bidentate Lewis acid, is easily prepared from diiodomethane and zinc powder.
K. Nomura, K. Oshima, S. Matsubara, Angew. Chem. Int. Ed., 2005, 44, 5860-5863.
Efficient, simple, cheap, and environmentally benign preparations of cyclopropanes were achieved. One method is based on a 3-exo-trig cyclisation of various electron-deficient 2-iodoethyl-substituted olefins with zinc powder in a mixture of t-butyl alcohol and water, and the other on a 3-exo-tet cyclisation of various 1,3-dihalopropanes with zinc powder in ethanol.
D. Sakuma, H. Togo, Tetrahedron, 2005, 61, 10138-10145.
The CoI2(dppe)-catalyzed diastereoselective reductive [3 + 2] cycloaddition of allenes and enones gives cyclopentanols in very good yields in the presence of zinc, zinc iodide, and water.
H.-T. Chang, T. T. Jayanth, C.-H. Cheng, J. Am. Chem. Soc., 2007, 129, 4166-4167.
A zinc/indium chloride-mediated pinacol cross-coupling reaction between aldehyde and α,β-unsaturated ketone in aqueous media gives 1,2-diols in good yields with up to 93:7 diastereoselectivity.
Y.-S. Yang, Z.-L. Shen, T.-P. Loh, Org. Lett., 2009, 11, 2213-2215.
A mild and convenient free-radical cyclization of organohalides in the presence of a NiCl2 • DME/Pybox complex as the catalyst and zinc powder in methanol efficiently gives carbo-, oxa-, and azacycles as products in high yields from unsaturated alkyl halides.
H. Kim, C. Lee, Org. Lett., 2011, 13, 2050-2053.
CuI-nanoparticles catalyze a selective synthesis of phenols, anilines, and thiophenols from aryl halides in the absence of both ligands and organic solvents. Anilines were formed selectively with ammonia competing with hydroxylation and thiophenols were generated selectively with sulfur powder after subsequent reduction competing with hydroxylation and amination.
H.-J. Xu, Y.-F. Liang, Z.-Y. Cai, H.-X. Qi, C.-Y. Yang, Y.-S. Feng, J. Org. Chem., 2011, 76, 2296-2300.
An efficient one-pot procedure for the zinc-mediated reduction of nitroarenes in the presence of chloroformates leads to the corresponding N,O-bisprotected hydroxylamines in good yield under ambient conditions in THF-water mixtures. Solvolysis of the bisprotected hydroxylamines with sodium methoxide at room temperature provides access to synthetically versatile N-aryl-N-hydroxy carbamates in excellent yields.
A. Porzelle, M. D. Woodrow, N. C. O. Tomkinson, Synlett, 2009, 798-802.
Upon treatment with aqueous sodium hydroxide in DMF, a range of chalcones underwent Michael addition reactions with nitroalkanes. The resulting adducts were reduced in situ with Zn/HCl (aq) to afford substituted Δ1-pyrrolines in high yields after a cyclization.
Y. Liang, D. Dong, Y. Lu, Y. Wang, W. Pan, Y. Chai, Q. Liu, Synthesis, 2006, 3301-3304.
A convenient and highly regioselective method allows the synthesis of 5-methylenepyrrolidinone derivatives from various nitriles and acrylamides via a cobalt-catalyzed reductive coupling reaction. A possible mechanism involves the formation of a cobaltaazacyclopentene intermediate from nitrile and acrylamide, protonation, keto-amide cyclization, and dehydration.
Y.-C. Wong, K. Parthsarathy, C.-H. Cheng, J. Am. Chem. Soc., 2009, 131, 18252-18253.
An efficient and convenient nickel-catalyzed cyclization of 2-iodoanilines with alkynyl aryl ketones gives 2,4-disubstituted quinolines. Naturally occurring quinoline derivatives have been prepared in good yields. The mechanism is discussed.
R. P. Korivi, C.-H. Cheng, J. Org. Chem., 2006, 71, 7079-7082.
The highly active mixed-ligand catalytic system NiCl2(dppp)/dppf combined with the reducing effect of zerovalent Zn enables a dramatic acceleration of the rate of the neopentylglycolborylation of aryl halides. A diversity of electron-rich and electron-deficient aryl iodides, bromides, and chlorides were efficiently neopentylglycolborylated in very good yields, typically in 1 h or less.
P. Leowanawat, A.-M. Resmerita, C. Moldoveanu, C. Liu, N. Zhang, D. A. Wilson, L. M. Hoang, B. M. Rosen, V. Persec, J. Org. Chem., 2010, 75, 7822-7828.
The mixed-ligand system NiCl2(dppp)/dppf is an effective catalyst for the neopentylglycolborylation of ortho-, meta-, and para-substituted electron-rich and electron-deficient aryl mesylates and tosylates. The addition of Zn powder as a reductant dramatically increases the reaction yield and reduces the reaction time, providing complete conversion in 1-3 h.
D. A. Wilson, C. J. Wilson, C. Moldoveanu, A.-M. Resmerita, P. Corcoran, L. M. Hoang, B. M. Rosen, V. Percec, J. Am. Chem. Soc., 2010, 132, 1800-1801.