Silica supported urea-hydrogen peroxide as a source of oxygen

February 2013- April 2013, Vol. 3, No. 2, 980-987. E- ISSN: 2249 –1929Journal of Chemical, Biological and Physical SciencesAn International Peer Review E-3 Journal of SciencesAvailable online atwww.jcbsc.orgSection A: Chemical scienceCODEN (USA): JCBPATResearch ArticleSilica supported urea-hydrogen peroxide as a source ofoxygenDamandeep Kaur * and B R ChhabraDepartment of Chemistry, Punjab Agricultural University, Ludhiana, Punjab, India,Received: 9 March 2013; Revised: 18 April 2013; Accepted: 23 April 2013Abstract: Silica supported urea-hydrogen peroxide (UHP-SiO 2 ) has been successfullyused for carrying out allylic oxidation and epoxidation reactions where it acts as a sourceof active oxygen under mild, heterogenous and environmental friendly conditions.Keywords: epoxidation, allylic oxidation, urea hydrogen peroxide, terpenoids.INTRODUTIONLiquid-phase oxidations and epoxidations of organic substrates in either homogenous or biphasic systemshave been studied using a wide range of oxidants including molecular oxygen, hydrogen peroxide(H 2 O 2 ), alkyl peroxides, iodosylarenes etc. 1-5 Hydrogen peroxide is the most common reagent foroxidation of organic compounds but it has several problems such as the instability of the reagent itself. Incontrast to all such classical procedures, the use of H 2 O 2 adducts is a convenient strategy to control H 2 O 2oxidation reactions. In general, H 2 O 2 adducts are not able to oxidise organic compounds by themselves,therefore the introduction of an organic catalyst or organic mediator for active oxygen transfer of theseadducts is a necessity in oxidation systems where they are used. Among these adducts, urea hydrogenperoxide (UHP) is an inexpensive, stable, mild and easy to handle source of H 2 O 2 . The catalyticepoxidation with hydrogen bonded urea adduct (UHP) 6-8 as an oxidant might offer some advantagesbecause of its relatively high proportion of H 2 O 2 (36.2%), safe handling and smooth decomposition intoenvironmentally safe substances. In recent years, UHP has gained importance as versatile ecofriendlyoxidant for affecting various organic transformations. Its corrosive, fire-hazardous, moisture, air and lightsensitive nature limits the scope of its laboratory applications. However, these difficulties could becircumvented when UHP adsorbed on silica gel (UHP-SiO 2 ) is used alongwith retaining its oxidativepotential, which being a stable, non-corrosive and moisture insensitive reagent can be used withoutspecial precaution and attention. The active hydrogen peroxide was found to be around 11.5% by weight980 J. Chem. Bio. Phy. Sci. Sec.A, 2013, Vol.3, No.2, 980-987.

Silica...Damandeep Kaur and B.R.Chabra.(determined iodometrically) in UHP adsorbed on silica gel (cf 36.2% in UHP adduct 8 without silica gel).Considering this fact the potential use of UHP- SiO 2 containing system for the allylic oxidation andepoxidation of some monoterpenes and sesquiterpenes containing different functionalities wasinvestigated. In this report, we examined the effect of UHP adsorbed on silica gel on the activity andselectivity in the oxidation reactions using tetrahydrofuran as a solvent and it has been found that it is aninvaluable oxidising reagent.EXPERIMENTALMelting points reported are uncorrected. The IR spectra were recorded in CHCl 3 solution on a PerkinElmer model RX-1 FT-IR spectrophotometer and 1 H NMR spectra in CDCl 3 on Bruker AC 300 F (300MHz) NMR spectrometer (chemical shifts in δ, ppm) with TMS as internal standard. All thechromatographic separations were performed on silica gel.Extraction of starting compounds- Alantolides were obtained from the powdered roots of Inula racemosaby Soxhlet extraction method in hexane followed by refrigeration. The column chromatography of thesolidified material afforded pure alantolactone and isoalantolactone which were identified by comparisonof their melting point and IR and 1 H NMR spectra with that of an authentic sample 10 . Dehydrocostuslactone was obtained from the powdered roots of costus (Saussurea lappa) by similar extractionprocedure.Preparation of UHP on silica gel: A solution of urea in 30% H 2 O 2 , in the molecular ratio 2:3 (12 g ureain 40 mL H 2 O 2 ) was heated in a pyrex dish for a few minutes at temperature of about 60°C. This solutionwas then added to 50 g silica gel (60-120 mesh size). The mixture was stirred for 30 min and dried underreduced pressure. The resulting free flowing powder was then stored at room temperature.REACTION PROCEDUREAllylic oxidation: In a typical allylic oxidation reaction, isoalantolactone (3, 4.31 mmol, 1.0 g) wasdissolved in 20 ml tetrahydrofuran (THF) containing selenium dioxide (0.09 mmol, 10 mg). To this wasadded 30 g of UHP-SiO 2 and the reaction mixture was stirred at room temperature slowly. The reactionwas completed after 5 hrs stirring. The mixture was filtered over a small bed of silica gel followed bywashing with THF. The organic layer was removed on rotary evaporator and extracted withdichloromethane (2 X 50 ml). The solvent was evaporated in vacuo to furnish a crude product, which wasrecrystallised to give a pure compound (4, 0.7 g). It showed mp 157° lit 9 mp 159-160°C. Similarly,geraniol (1) and dehydrocostus lactone (5) on allylic oxidation under similar conditions gave purecompounds (2) and (6, mp 140°C) respectively. The products obtained (Table 1) in this reaction weresimilar to those reported earlier. 6Epoxidation of olefins: Isoalantolactone (3, 4.31 mmol, 1.0 g) was dissolved in 20 ml THF. To this wasadded 30 g of UHP-SiO 2 and catalytic quantity of dodeca-phosphotungstic acid (H 3 [PW 12 O 40 ]xH 2 O). Thereaction mixture was stirred at room temperature for 6 hrs. The mixture was filtered over a small bed ofsilica gel followed by washing with THF. The organic layer was removed on rotary evaporator andextracted with dichloromethane (2 X 50 ml). The solvent was evaporated in vacuo to furnish a crudeproduct, which was recrystallised to give a pure compound (7, 0.68 g). It showed mp 127° lit 10 mp126°C. Similarly, carvone (13) on treatment with UHP-SiO 2 and dodeca-phosphotungstic acid after usualwork up gave compound (14). It showed IR bands at 1660 and 1680 cm -1 confirming the presence of α,βunsaturatedsystem in 6- membered ring.Epoxidation of α,β- unsaturated ketones: To carvone (13, 0.5 ml) in THF (20 ml) was added UHP-SiO 2 (5 g) followed by NaOH solution (10%, 5 ml). The reaction mixture was kept at 4°C for 72 hrs. The981 J. Chem. Bio. Phy. Sci. Sec. A, 2013, Vol.3, No.2, 980-987.

Silica...Damandeep Kaur and B.R.Chabra.usual work up involving dilution with water, neutralization with dil. HCl and extraction with diethylether yielded a two component mixture (0.44 ml). This upon column chromatography over silica gel (25g) afforded pure compound (15, 0.41 ml). Similar reaction of dehydrocostus lactone (5) yielded epoxide(9) which showed mp 76° lit 11 mp 78°C. All the products formed have been identified by their IR, 1 HNMR and 13 C NMR spectral analysis (Table 2).Table-1: Allylic oxidations and epoxidations of alkenes withUHP-SiO 2 as oxidantAllylic oxidationsOHOH(1)CHO (2)HHOOOOHH(3)HOHH(4)HHHHHOHHHHOOO(5)O(6)EpoxidationsHHOOOOHH(3)OHH(7)982 J. Chem. Bio. Phy. Sci. Sec. A, 2013, Vol.3, No.2, 980-987.

Silica...Damandeep Kaur and B.R.Chabra.HHHHHHHOHOOO(5)O(8)HHHHHHHHOOOO(5)O(9)OOOHOHOHO(1)MajorMinor(11) (12)OOOOO(13)(14) (15)983 J. Chem. Bio. Phy. Sci. Sec. A, 2013, Vol.3, No.2, 980-987.

Silica...Damandeep Kaur and B.R.Chabra.Table-2: IR, 1 H NMR and 13 C NMR characterization data for compoundsCompoundIR Bands(ν max /cm -1 )1 H NMR (δ,CDCl 3 )13 C NMR (δ,CDCl 3 )OH3490, 2725,1620, 11209.5 (s, 1H), 6.5 (t,1H), 3.7 (t, 2H),3.3 (brs, 1H), 2.4(m, 2H), 1.8 (s,3H), 1.5 (m, 5H),1.0 (d, 3H)60.2 (t), 39.7 (t),29.4 (d), 37.7 (t),24.2 (t), 154.3 (d),138.5 (s), 192.8 (d),21.1 (q), 8.9 (q)CHO (2)HOHHHOO(4)3400, 1750,1668, 1155,1450, 932,8654.6 (m, 1H), 5.70and 6.15 (d, 1Heach), 1.04 (s, 3H),4.7 and 4.9 (d, 1Heach), 4.2 (t, 1H)33.1 (t), 31.5 (t),76.0 (d), 148.7 (s),50.5 (d), 30.4 (t),44.5 (d), 76.8 (d),44.8 (t), 28.7 (s),138.2 (s), 170.0 (s),123.9 (t), 23.1 (q),109.1 (t)HOHHHOH3600, 3082,1760, 1640,1600, 1144,8904.05 (t, 1H), 3.85(t, 1H), 5.55 and6.18 (d, 1H each),4.9 and 4.95 (brs,1H each), 5.48 and5.63 (d, 1H each)44.7 (d), 40.1 (t),81.1 (d), 155.6 (s),50.8 (d), 84.8 (d),48.2 (d), 31.4 (t),36.2 (t), 148.6 (s),138.4 (s), 170.0 (s),123.8 (t), 109.2 (t),109.0 (t)O(6)OHHHOO(7)1770, 1672,1475, 1355,1262, 890,8101.18 (3H, s), 2.80(1H each, d), 4.67(1H, m), 5.73 and6.40 (2H, brs)40.2 (t), 21.5 (t),35.9 (t), 62.1 (s),54.9 (d), 26.2 (t),41.5 (d), 77.0 (d),44.1 (t), 37.1 (s),138.5 (s), 170.1 (s),120.3 (t), 21.1 (q),50.3 (t)984 J. Chem. Bio. Phy. Sci. Sec. A, 2013, Vol.3, No.2, 980-987.

Silica...Damandeep Kaur and B.R.Chabra.OHHHOH1750, 1655,910, 8806.07 and 5.37 (1Heach, d), 3.89 (1H,dd), 5.10 and 4.90(1H each, brs),3.27 and 2.74 (1Heach, d)46.5 (d), 29.8 (t),28.1 (t), 69.7 (s),53.0 (d), 85.1 (d),46.7 (d), 30.2 (t),36.5 (t), 148.2 (s),138.5 (s), 170.2 (s),119.3 (t), 108.5 (t),50.5 (t)O(8)HHHOHO3080, 1788,1640, 1120,8954.1 (1H, t), 3.1(2H, s), 4.9 and 5.0(1H each, brs),5.63 and 6.25 (1Heach, d)43.4 (d), 34.8 (t),210.4 (s), 148.3 (s),49.4 (d), 84.6 (d),43.4 (d), 29.8 (t),32.9 (t), 144.5 (s),59.8 (s), 178.4 (s),50.8 (t), 118.4 (s),112.4(s)O(9)OOH3480, 1615,1115, 10203.79 and 3.54 (2H,dd), 2.60 (1H, t),5.20 (1H, t), 1.40(1H, t), 1.95 (2H,m)61.2 (t), 64.9 (d),63.3 (s), 38.8 (t),24.3 (t), 124.7 (d),131.3 (s), 18.6 (q),24.6 (q), 17.5 (q)(11)OOH3430, 1140,10153.75 and 3.50 (2H,dd), 2.58 (1H, t),2.51 (1H, t), 1.24(3H, s), 1.36 (3H,s), 1.29 (3H, s)60.2 (t), 64.8 (d),63.2 (s), 36.4 (t),28.0 (t), 66.5 (d),61.7 (s), 24.4 (q),25.0 (q), 17.1 (q)O(12)O1680, 1660 6.32 (1H, t), 2.01(1H, m), 1.24 (3H,s), 2.39 and 2.54(1H each, d), 2.45(3H, s)198.5 (s), 135.1 (s),145.4 (d), 28.8 (t),41.6 (d), 40.2 (t),62.5 (s), 21.8 (q),52.4 (t), 16.9 (q)O(14)985 J. Chem. Bio. Phy. Sci. Sec. A, 2013, Vol.3, No.2, 980-987.

Silica...Damandeep Kaur and B.R.Chabra.OO1720, 1685,3075, 8902.75 (1H, t), 2.51(1H, m), 1.80 (3H,s), 4.90 and 5.10(1H each, d), 1.34(3H, s)205.4 (s), 62.5 (s),62.9 (d), 29.9 (t),35.8 (d), 42.5 (t),147.8 (s), 21.5 (q),110.9 (t), 15.5 (q)(15)RESULTS AND DISCUSSIONThe results obtained under the most favorable conditions using UHP- SiO 2 as the oxidising reagent arebetter than those obtained with aqueous H 2 O 2 under the same reaction conditions. The reagent is morestable and could be stored for several months without the loss of weight or its activity when compared toUHP as such. It does not need any special handling as is required in the case of peroxides. This reagentbeing inexpensive, non toxic and easily available is quite efficient for various organic transformations.Therefore, it is recommended for use in different purposes in organic chemistry which require hydrogenperoxide, as the easy recovery of the product using this reagent make these processes moreenvironmental friendly.List of abbreviations used:Silica supported urea-hydrogen peroxide UHP-SiO 2Hydrogen peroxide H 2 O 2Urea hydrogen peroxideUHPtetrahydrofuranTHFACKNOWLEDGEMENTThe authors thank the Punjab Government for financial support under the project ‘Chemistry andpotential of some natural products and synthetic heterocyclics as agrochemicals’.REFERENCES1. C. L. Hill, C. M. Prosser-McCartha, Coordination. Chem. Rev., 1995, 143, 407.2. I. V. Kozhevnikov, Chem. Rev., 1998, 98, 171.3. T. Okuhara, N. Mizuno, M. Misono, Adv. Catal., 1996, 41, 113.4. D. K. Lyon, W. K. Miller, T. Novet, P. J. Domaille, E. Evitt, D. C. Johnson, R. G. Finke, J. Am. Chem.Soc., 1991, 113, 7209.5. D. Mansuy, J. F. Bartoli, P. Battioni, D. K. Lyon, R. G. Finke, J. Am. Chem. Soc., 1991, 113, 7222.6. R. Manktala, R. S. Dhillon, B. R. Chhabra, Ind. J. Chem., 2006, 45B, 1591.7. N. K. Kala Raj, A. V. Ramaswamy, P. Manikandan, J. Mol. Catal. A : Chem., 2005, 227, 37.8. C. Lu, E. W. Hughes, P. A. Giguere, J. Am. Chem. Soc., 1941, 63, 1507.9. R. B. Milller, E. D. Behare, J Am Chem Soc, 1974, 96, 8102.986 J. Chem. Bio. Phy. Sci. Sec. A, 2013, Vol.3, No.2, 980-987.

Silica...Damandeep Kaur and B.R.Chabra.10. P. S. Kalsi, R. Goyal, K. K. Talwar, B. R. Chhabra, Phytochemistry, 27, 1988, 2079.11. B. R. Chhabra, S. Gupta, R. S. Dhillon, P. S. Kalsi, Fitoterapia, 1997, 68, 470.Corresponding author: Damandeep KaurDepartment of Chemistry, Punjab Agricultural University, Ludhiana, Punjab, India,987 J. Chem. Bio. Phy. Sci. Sec. A, 2013, Vol.3, No.2, 980-987.