Polyethylene Glycols as Efficient Media for Decarboxylative Nitration of α,β-Unsaturated Aromatic Carboxylic Acids by Ceric Ammonium Nitrate in Acetonitrile Medium: A Kinetic and Mechanistic Study
Polyethylene glycols (PEGs) were found to be efficient media for decarboxylative nitration of α,β-unsaturated aromatic carboxylic acids by ceric ammonium nitrate (CAN) in acetonitrile to give β-nitrostyrene derivatives. Kinetics of the reaction exhibited second order kinetics with a first order dependence on [CAN] and [substrate]. Reactions were too sluggish to be studied in the absence of PEG; therefore detailed kinetics were not taken up. Reaction times were reduced from 24 hrs to few hours. The catalytic activity was found to be in the increasing order PEG-300 > PEG-400 > PEG-600 > PEG-200. Mechanism of PEG-mediated reactions was explained by Menger-Portnoy's scheme as applied in micellar kinetics. 1. Introduction Cerium (IV) ammonium nitrate (CAN) is one of the most important reagents used for organic synthesis [1–4]. The formula of cerium (IV) ammonium nitrate, [(NH4)2[Ce(NO3)6], reflects that the cerium (IV) ion is surrounded by six nitrate groups and the ammonium ions are counterions to compensate for the negative charge of the hexanitratocerate (IV) coordinating unit. CAN is a one-electron oxidation reagent. Cerium (IV) ammonium nitrate can also be used as a nitrating agent [5, 6], initiator for radical polymerization reactions [7], and also as a reagent to remove protecting groups [8]. Even though cerium (IV) reagents are milder oxidation reagents than the other metal-based oxidation reagents such as Mn(VII) and Cr(VI) salts, they are relatively much less toxic. Because of their high molecular mass, large quantities of cerium (IV) salts are required for stoichiometric reactions. Therefore, indirect and catalytic reactions using Ce(IV) have been developed [9, 10]. The main advantage of CAN over other cerium (IV) reagents is its higher solubility in organic solvents. The most popular solvents are (in decreasing order of importance) water, acetonitrile, dichloromethane, THF, and methanol [11]. Often mixtures of these solvents are also used as reaction medium. Other solvents have found only marginal use for this type of reactions. Being good Michael acceptors, α,β-unsaturated nitroalkenes are widely applied in organic synthesis [12]. Among various methods reported for their preparation, a method involving the use of CAN provides a practical way to the synthesis of α,β-unsaturated “nitroalkenes” in good-to-excellent yields [13–23]. Recently polyethylene glycols (PEGs) have been used as catalysts and catalyst supports and also have been found to be an inexpensive, nontoxic, and environmentally friendly reaction medium, which avoid the use of acid or
References
[1]
T. L. Ho, “Ceric ion oxidation in organic chemistry,” Synthesis, vol. 6, pp. 347–354, 1973.
[2]
V. Nair, L. Balagopal, R. Rajan, and J. Mathew, “Recent advances in synthetic transformations mediated by cerium(IV) ammonium nitrate,” Accounts of Chemical Research, vol. 37, no. 1, pp. 21–30, 2004.
[3]
J. R. Hwu and K. Y. King, “Versatile reagent ceric ammonium nitrate in modern chemical synthesis,” Current Science, vol. 81, no. 8, pp. 1043–1053, 2001.
[4]
V. Nair and A. Deepthi, “Cerium(IV) ammonium nitrate—a versatile single-electron oxidant,” Chemical Reviews, vol. 107, no. 5, pp. 1862–1891, 2007.
[5]
V. Singh, V. Sapehiyia, and G. L. Kad, “Ultrasonically activated oxidation of hydroquinones to quinones catalysed by ceric ammonium nitrate doped on metal exchanged K-10 clay,” Synthesis, no. 2, pp. 198–200, 2003.
[6]
H. M. Chawla and R. S. Mittal, “Oxidative nitration by silica gel-supported cerium(IV) ammonium nitrate,” Synthesis, vol. 1, pp. 70–72, 1985.
[7]
S. Dincturk and J. H. J. Ridd, “Nitration of an electron-rich aromatic compound by CAN-SiO2,” Journal of the Chemical Society, Perkin Transactions, vol. 2, pp. 965–969, 1982.
[8]
A. S. Sarac, “Redox polymerization,” Progress in Polymer Science, vol. 24, no. 8, pp. 1149–1204, 1999.
[9]
I. E. Marko, A. Ates, A. Gautier et al., “Cerium(IV)-catalyzed deprotection of acetals and ketals under mildly basic conditions,” Angewandte Chemie International Edition, vol. 38, no. 21, pp. 3207–3209, 1999.
[10]
N. Maulide, J. C. Vanherck, A. Gautier, and I. E. Markó, “Mild and neutral deprotections catalyzed by cerium(IV) ammonium nitrate,” Accounts of Chemical Research, vol. 40, no. 6, pp. 381–392, 2007.
[11]
J. Christoffers, T. Werner, and M. R？ssle, “Cerium-catalyzed oxidative C–C bond forming reactions,” Catalysis Today, vol. 121, no. 1-2, pp. 22–26, 2007.
[12]
M. R？ssle, T. Werner, W. Frey, and J. Christoffers, “Cerium-catalyzed, aerobic oxidative synthesis of 1,2-dioxane derivatives from styrene and their fragmentation into 1,4-dicarbonyl compounds,” European Journal of Organic Chemistry, no. 23, pp. 5031–5038, 2005.
[13]
E. Ganin and I. Amer, “Cerium-catalyzed selective oxidation of alkylbenzenes with bromate salts,” Synthetic Communications, vol. 25, no. 20, pp. 3149–3154, 1995.
[14]
K. Auty, B. C. Gilbert, C. B. Thomas, S. W. Brown, C. W. Jones, and W. R. Sanderson, “The selective oxidation of toluenes to benzaldehydes by cerium(III), hydrogen peroxide and bromide ion,” Journal of Molecular Catalysis A, vol. 117, no. 1–3, pp. 279–287, 1997.
[15]
R. P. Kreh, R. M. Spotnitz, and J. T. Lundquist, “Mediated electrochemical synthesis of aromatic aldehydes, ketones, and quinones using ceric methanesulfonate,” Journal of Organic Chemistry, vol. 54, no. 7, pp. 1526–1531, 1989.
[16]
H. Feuer and A. T. Nielsen, Nitro Compounds Recent Advances in Synthesis and Chemistry, vol. 9, VCH Publishers, New York, NY, USA, 1990.
[17]
A. G. M. Barrett, “Heterosubstituted nitroalkenes in synthesis,” Chemical Society Reviews, vol. 20, no. 1, pp. 95–127, 1991.
[18]
R. S. Varma and G. W. Kabalka, “Nitroalkenes in the synthesis of heterocyclic compounds,” Heterocycles, vol. 24, no. 9, pp. 2645–2677, 1986.
[19]
S. E. Denmark and L. R. Marcin, “A general method for the preparation of 2,2-disubstituted 1-nitroalkenes,” Journal of Organic Chemistry, vol. 58, no. 15, pp. 3850–3856, 1993.
[20]
M. Node, A. Itoh, K. Nishide et al., “Preparation of nitroalkenes: Substitution reaction via addition-elimination using β-nitrovinyl sulfoxides,” Synthesis, no. 11, pp. 1119–1124, 1992.
[21]
R. Ballini, R. Castagnani, and M. Petrini, “Chemoselective synthesis of functionalized conjugated nitroalkenes,” Journal of Organic Chemistry, vol. 57, no. 7, pp. 2160–2162, 1992.
[22]
S. S. Jew, H. D. Kim, Y. S. Cho, and C. H. Cook, “A practical preparations of conjugated nitroalkenes,” Chemistry Letters, vol. 1986, no. 10, pp. 1747–1748.
[23]
W. W. Sy and A. W. By, “Nitration of substituted styrenes with nitryl iodide,” Tetrahedron Letters, vol. 26, no. 9, pp. 1193–1196, 1985.
[24]
V. V. Namboodiri and R. S. Varma, “Microwave-accelerated Suzuki cross-coupling reaction in polyethylene glycol (PEG),” Green Chemistry, vol. 3, no. 3, pp. 146–148, 2001.
[25]
A. Haimov and R. Neumann, “Polyethylene glycol as a non-ionic liquid solvent for polyoxometalate catalyzed aerobic oxidation,” Chemical Communications, no. 8, pp. 876–877, 2002.
[26]
L. Heiss, “Polyethylene glycol monomethyl ether-modified pig liver esterase: Preparation, characterization and catalysis of enantioselective hydrolysis in water and acylation in organic solvents,” Tetrahedron Letters, vol. 36, no. 22, pp. 3833–3836, 1995.
[27]
S. Chandrasekhar, C. Narsihmulu, S. S. Sultana, and N. R. Reddy, “Osmium tetroxide in poly(ethylene glycol) (PEG): a recyclable reaction medium for rapid asymmetric dihydroxylation under sharpless conditions,” Chemical Communications, vol. 9, no. 14, pp. 1716–1717, 2003.
[28]
K. Tanemura, T. Suzuki, Y. Nishida, and T. Horaguchi, “Aldol condensation in water using polyethylene glycol 400,” Chemistry Letters, vol. 34, no. 4, pp. 576–577, 2005.
[29]
R. Kumar, P. Chaudhary, S. Nimesh, and R. Chandra, “Polyethylene glycol as a non-ionic liquid solvent for Michael addition reaction of amines to conjugated alkenes,” Green Chemistry, vol. 8, no. 4, pp. 356–358, 2006.
[30]
J. R. Johnson, “The perkin reaction and related reactions,” Organic Reactions, vol. 1, p. 210, 1942.
[31]
C. I. Chiriac, F. Tanasa, and M. Onciu, “A novel approach in cinnamic acid synthesis: direct synthesis of cinnamic acids from aromatic aldehydes and aliphatic carboxylic acids in the presence of boron tribromide,” Molecules, vol. 10, no. 2, pp. 481–487, 2005.
[32]
H. A. Benesi and J. H. Hildebrand, “Ultraviolet absorption bands of iodine and aromatic hydrocarbons,” Journal of the American Chemical Society, vol. 71, pp. 1832–1833, 1949.
[33]
M. Santappa and B. Sethuram, “Oxidation studies. IV. Kinetics of oxidation of HCHO and some alcohols by ceric salts in HNO3 medium,” Proceedings of the Indian Academy of Sciences Section A, vol. 67, no. 2, pp. 78–89, 1968.
[34]
K. V. Rao and S. S. Muhammed, “Oxidation of alcohols by cerium(IV). I. Oxidation of methanol by ceric perchlorate,” Bulletin of the Chemical Society of Japan, vol. 36, no. 8, pp. 943–949, 1963.
[35]
S. S. Muhammed and B. Sethuram, “Oxidation of alcohols by cerium(IV). I. Oxidation of isopropanol and secondary butanol by ceric nitrate,” Acta Chimica Hungarica, vol. 46, pp. 115–124, 1965.
[36]
N. Dutt, R. R. Nagori, and R. N. Mehrotra, “Kinetics and mechanisms of oxidations by metal ions. Part VI. Oxidation of α-hydroxyl acids by cerium (IV) in aqueous nitric acid,” Canadian Journal of Chemistry, vol. 64, no. 1, pp. 19–23, 1986.
[37]
F. M. Menger and C. E. Portnoy, “Chemistry of reactions proceeding inside molecular aggregates,” Journal of the American Chemical Society, vol. 89, no. 18, pp. 4698–4730, 1967.
[38]
K. A. Connors, Chemical Kinetics: The Study of Reaction Rates in Solution, VCH, New York, NY, USA, 1990.
[39]
J. H. Espenson, Chemical Kinetics and Reaction Mechanism, McGraw-Hill, New York, NY, USA, 1981.
[40]
V. Jagannadham, “The change in entropy of activation due to solvation (hydration) of ions: proton versus carbocation,” Chemistry (the Bulgarian Journal of Chemical Education), vol. 18, p. 89, 2009.
