Supporting Information
Metal-free activation of H2O2 by synergic effect of ionic liquid and microwave: Chemoselective oxidation of benzylic alcohols to carbonyls and unexpected formation of anthraquinone in aqueous condition
Rakesh Kumar, Nandini Sharma, Naina Sharma, Abhishek Sharma, and Arun K. Sinha*
Natural Plant Products Division, Institute of Himalayan Bioresource Technology (C.S.I.R.), Palampur (H.P.)-176061, India.
Molecular Diversity
Table of contents
Contents Page No.
This Page ------S1
Experimental Details ------S2-S4
Compounds Characterization data ------S5-S8
Spectral Data (H1 & C13 NMR, GC-MS, LC-MS and HPLC spectra
of some representative carbonyls)------S9-S31
Experimental Section:
Materials:
All the reagents were either obtained from commercial sources (Merck or across) or synthesized from the corresponding benzaldehydes/Grignard reagents [1] or reduction with sodium borohydride of the corresponding acetophenones/propiophenones [2]. Hydrogen peroxide was 30% aqueous solution purchased from Merck. The ionic liquid [bmim]Br, [hmim]Br were synthesized from 1-methylimidazole and corresponding alkyl bromides according to the reported method [3]. Ionic liquid [bmim]OH was obtained through metathesis reaction of [bmim]Br. Ionic liquid [bmim]BF4 and [bmim]Cl were purchased from Merck. The purity of the used ionic liquid [hmim]Br was checked by NMR spectra and matched with commercial sample purchased from Merck. The solvents used for isolation/purification of compounds were obtained from commercial sources (Merck) and used without further purification. 1H (300 MHz) and 13C (75.4 MHz) NMR spectra were recorded on a BRUKER AVANCE-300 spectrometer. GC-MS analysis was undertaken using a Shimadzu - 2010 spectrometer. CEM Discover© focused microwave (2450 MHz, 300 W) was used wherever mentioned. The temperature of reactions in microwave experiments was measured by an inbuilt infrared temperature probe that determined the temperature on the surface of reaction flask. The sensor is attached in a feedback loop with an on-board microprocessor to control the temperature rise rate.
______
1. Sharma A, Joshi BP, Sinha AK (2004) An effective system to synthesize hypolipidemic active a-asarone and related methoxylated (E)-arylalkenes. Bull Chem Soc Jpn 77: 2231-2235.
2. Botteghi C, Paganelli S, Moratti F, Marchetti M, Lazzaroni R, Settambolo R, Piccolo O (2003) Synthesis of 2-chromanol by hydroformylation of 2-hydroxystyrene derivatives. J Mol Cat A: Chem 200: 147-156.
3. Nockemann P, Binnemans K, Driesen K (2005) Purification of imidazolium ionic liquids for spectroscopic applications. Chem Phys Lett 415: 131-136.
In the case of conventional heating in an oil bath, the temperature of reaction mixture was monitored by an inner thermometer. HPLC analysis of the samples and standards was performed using a Shimadzu HPLC (Model LC-20AT pump, DGU-20A5 degasser) equipped with auto sampler (SIL-20AC), photo diode array detector (CBM-20A; Shimadzu, Kyoto, Japan) and interfaced with IBM Pentium 4 personal computer.
General procedure:
Representative Procedure for oxidation of 4-methoxyphenylpropan-1-ol (1a):
(a) Under Microwave irradiation:
4-Methoxyphenylpropan-1-ol (1a, 0.6 mmol) was dissolved in [hmim]Br (1g). Then 1ml of 30% aqueous solution of hydrogen peroxide was added and the mixture was shaken to make it homogeneous. The flask was irradiated under focused microwave system (150 W, 120 °C) fitted with reflux condenser for 8 min. After the completion of reaction, the reaction mixture was cooled and extracted with diethyl ether (3x8 mL) and the ionic liquid was recovered as a residue to be further used in the next cycle. The combined organic layer was washed with water, dried and vacuum evaporated. The crude product was purified by column chromatography on silica gel (60-120 mesh size) using n-hexane-EtOAc (25:1) mixture as eluent to give 1b (83%) as a colorless liquid [4] which was confirmed by 1H and 13C NMR spectra. This procedure was used for the oxidation of all the benzyl alcohols. For the oxidation of acetylated/benzoylated derivatives of benzyl alcohols (Table 5), in the above procedure, 1.5 ml of H2O2 (instead of 1 ml) was used.
______
4. Choudhary VR, Jana SK, Patil NS (2002) Acylation of aromatic compounds using moisture insensitive InCl3 impregnated mesoporous Si-MCM-41 catalyst. Tetrahedron Lett 43: 1105-1107.
(b) Under conventional heating:
4-Methoxyphenylpropan-1-ol (1a, 0.6 mmol) was dissolved in ionic liquid [hmim]Br (1g). Then 1ml of 30% aqueous solution of hydrogen peroxide was added and the mixture was shaken to make it homogeneous. The flask was heated in an oil bath at 120oC for 2 h. After the completion of reaction, the reaction mixture was worked up as in above procedure to give the product 1b (68%) as a colorless liquid [4] which was confirmed by 1H and 13C NMR spectra.
Characterization Data for synthesized compounds:
Compound 1b [4]; (Table 3, Entry 1); Colorless viscous liquid, dH (300 MHz, CDCl3); 8.29 (2H, d, J = 9.2 Hz), 7.27 (2H, d, J = 9.2 Hz), 4.19 (3H, s), 3.31 (2H, q, J = 7.7 Hz), 1.57 (3H, t, J = 7.7 Hz); dC (75.4 MHz, CDCl3) 199.8, 163.7, 130.5, 114.0, 55.8, 31.7 and 8.8.
Compound 2b [5]; (Table 3, Entry 2); White solid, mp 84-86 °C, dH (300 MHz, CDCl3); 8.07 (2H, d, J = 8.1 Hz), 7.71 (2H, d, J = 7.9 Hz), 7.66 (2H, d, J = 7.9 Hz), 7.51-7.39 (3H, m), 3.08 (2H, q, J = 7.3 Hz), 1.3 (3H, t, J= 6.8 Hz), dC (75.4 MHz, CDCl3) 200.7, 145.9, 140.3, 136.0, 129.3, 128.9, 128.5, 127.6, 127.5, 32.2 and 8.7.
Compound 3b [6]; (Table 3, Entry 3); Colorless liquid, dH (300 MHz, CDCl3); 7.79 (2H, d, J = 8.8 Hz), 7.39-7.24 (3H, m), 2.85 (2H, q, J = 7.3 Hz), 1.07 (3H, t, J = 7.1 Hz); dC (75.4 MHz, CDCl3) 201.1, 137.3, 133.2, 128.9, 128.3, 32.1 and 8.6.
5. Chidambaram M, Venkatesan C, Moreaub P, Finiels A, Ramaswamy AV, Singh AP (2002) Selective benzoylation of biphenyl to 4-phenylbenzophenone over zeolite H-beta. App Catal A 224: 129-140.
6. Kuhakarn C, Kittigowittana, K, Pohmakotr M, Reutrakul V (2005) Investigation of substrate-selectivity pattern in the oxidation of secondary alcohols by amino acid-derived IBX derivatives. ARKIVOC (i): 143-153.
Compound 4b [4]; (Table 3, Entry 4); viscous liquid, dH (300 MHz, CDCl3); 7.88 (2H, d, J = 8.8 Hz), 6.86 (2H, d, J = 8.8 Hz), 3.78 (3H, s), 2.83 (2H, t, J = 7.1 Hz), 1.78 (2H, m), 1.01 (3H, t, J = 7.5 Hz); dC (75.4 MHz, CDCl3) 199.1, 163.5, 130.4, 113.9, 55.6, 40.4, 18.2 and 14.1.
Compound 6b [7]; (Table 3, Entry 6); White solid, mp 48-51 °C (lit. mp 49-51 °C), dH (300 MHz, CDCl3); 7.56 (1H, d, J = 8.6 Hz), 7.49 (1H, s), 6.87 (1H, d, J = 8.6 Hz), 3.92 (6H, s), 2.54 (3H, s); dC (75.4 MHz, CDCl3) 197.2, 153.8, 149.6, 131.1, 123.7, 110.7, 110.5, 56.5 and 26.6.
Compound 7b [8]; (Table 3, Entry 7); White solid, mp 78-81 °C (lit. mp 78-80 °C), dH (300 MHz, CDCl3); 7.27 (2H, s), 3.97 (9H, s), 2.60 (3H, s); dC (75.4 MHz, CDCl3) 197.1, 153.5, 143.1, 132.9, 106.4, 61.3, 56.7 and 26.7.
Compound 8b [9]; (Table 3, Entry 8); White solid, mp 47-49 °C (lit. mp 47.9 °C), dH (300 MHz, CDCl3); 7.83 (4H, d, J = 8.1 Hz), 7.61-7.56 (2H, m), 7.50-7.45 (4H, m); dC (75.4 MHz, CDCl3) 197.0, 138.0, 132.8, 130.7 and 128.6.
7. Hajipour AR, Mallakpour SE, Baltork IM, Adibi H (2003) Microwave Assisted Conversion of Oximes and Semicarbazones to Carbonyl Compounds Using Benzyltriphenylphosphonium Peroxymonosulfate Monatsh Chem 134: 45-49.
8. Yokoyama1 T, Chang H, Reiner RS, Atalla RH, Weinstock IA, Kadla1 JF (2004) Polyoxometalate oxidation of non-phenolic lignin subunits in water: Effect of substrate structure on reaction kinetics. Holzforschung 58: 116–121.
9. Jain SL, Sharma VB, Sain B (2006) Highly efficient and selective oxidation of secondary alcohols to ketones under organic solvent and transition metal free conditions. Tetrahedron 62: 6841-6847.
Compound 9b [10]; (Table 3, Entry 9); White solid, mp 85-88 °C (lit. mp 86–89 °C) dH (300 MHz, CDCl3); 7.40 (1H, d, J = 7.7 Hz), 7.26 (1H, s), 6.70 (1H, d, J = 8.4 Hz), 5.88 (2H, s), 2.38 (3H, s); dC (75.4 MHz, CDCl3) 196.1, 151.8, 148.2, 132.2, 124.8, 108.0, 107.8, 101.9 and 26.4.
Compound 10b [11]; (Table 3, Entry 10); White solid, mp 77-80 °C (lit. mp 76–80 °C), dH (300 MHz, CDCl3); 7.43 (2H, d, J = 8.9 Hz), 7.27 (2H, d, J = 8.8 Hz), 1.83 (3H, s); dC (75.4 MHz, CDCl3) 196.6, 150.7, 141.8, 129.6, 124.1 and 27.2.
Compound 11b [12]; (Table 3, Entry 11); White solid, mp 52-56 °C (lit. mp 53–56 °C), dH (300 MHz, CDCl3); 8.13 (1H, s), 7.74 (1H, d, J = 8.8 Hz), 7.65 (1H, d, J = 7.5 Hz), 7.56 (2H, d, J = 8.4 Hz), 7.31-7.21 (2H, m), 2.40 (3H, s); dC (75.4 MHz, CDCl3) 198.3, 135.9, 134.9, 132.9, 130.5, 129.9, 128.8, 128.7, 128.1, 127.1, 124.2 and 27.0.
10. Giddens AC, Boshoff HIM, Franzblau SG, Barry CE, Coppa BR (2005) Antimycobacterial natural products: synthesis and preliminary biological evaluation of the oxazole-containing alkaloid texaline. Tetrahedron Lett 46: 7355–7357.
11. Mannam S, Alamsetti SK, Sekar G (2007) Aerobic, chemoselective oxidation of alcohols to carbonyl compounds catalyzed by a DABCO-copper complex under mild conditions. Adv Synth Catal 349: 2253-2258.
12 Chhikara BS, Chandra R, Tandon V (2005) Oxidation of alcohols with hydrogen peroxide catalyzed by a new imidazolium ion based phosphotungstate complex in ionic liquid. J Catal 230: 436-439.
Compound 12b[13] ; (Table 3, Entry 12); White solid, mp 164-167 °C, dH (300 MHz, CDCl3); 7.68 (1H, d, J = 15.7 Hz), 7.57 (1H, d, J = 8.0 Hz), 7.49-7.44 (3H, m), 7.40 (1H, d, J = 15.7 Hz), 7.31 (2H, d, J = 8.4 Hz ), 6.82 (1H, d, J = 8.0 Hz), 5.98 (2H, s); dC (75.4 MHz, CDCl3) 187.9, 151.8, 148.3, 142.7, 136.2, 133.5, 132.8, 129.5, 129.2, 124.7, 122.1, 108.4, 107.9 and 101.9. HRMS-ESI: m/z [M+H]+ for C16H11ClO3, calculated 287.0470; observed 287.0469.
Compound 24c [14]; (Table 6, Entry 24); Yellow solid, mp 284-286 °C (lit. mp 286 °C), dH (300 MHz, CDCl3); 8.32 (4H, s), 7.81 (4H, s), dC (75.4 MHz, CDCl3) 183.5, 134.3, 133.7 and 127.4. HRMS-ESI: m/z [M+H]+ for C14H8O2, calculated 209.0597; observed 209.0592.
Compound 30 [15]; (Table 6, Entry 30); White solid, mp 178-181 °C (lit. mp 179-182 °C), dH (300 MHz, CDCl3); 7.79 (1H, d, J = 8.2 Hz), 7.60 (1H, s), 6.93 (1H, d, J = 8.2 Hz), 3.96 (6H, s); dC (75.4 MHz, CDCl3) 171.7, 153.9, 148.9, 124.7, 122.0, 112.6, 110.5 and 56.2.
13. Kumar R, Mohanakrishnan D, Sharma A, Kaushik NK, Kalia K, Sinha AK, Sahal D (2010) Reinvestigation of structure-activity relationship of methoxylated chalcones as antimalarials: Synthesis and evaluation of 2,4,5-trimethoxy substituted patterns as lead candidates derived from abundantly available natural b-asarone. Eur J Med Chem 45:5292-5301.
14. Martin JMC, Brieva GB, Fierro JLG (2006) Hydrogen peroxide synthesis: An outlook beyond the anthraquinone process. Angew Chem Int Ed 45: 6962-6984.
15. Buffin BP, Clarkson JP, Belitz, NL, Kundu A (2005) Pd(II)-biquinoline catalyzed aerobic oxidation of alcohols in water. J Mol Catal A: Chem 225: 111-116.
Table 3/ 1b, 1H NMR (in CDCl3)
Table 3/1b, 13C NMR (in CDCl3)
Table 3/ 2b, 1H NMR (in CDCl3)
Table 3/2b, 13C NMR (in CDCl3)
Table 3/ 4b, 1H NMR (in CDCl3)
Table 3/4b, 13C NMR (in CDCl3)
Table 3/ 11b, 1H NMR (in CDCl3)
Table 3/11b, 13C NMR (in CDCl3)
Table 3/12b, 1H NMR (in CDCl3)
Table 3/12b, 13C NMR (in CDCl3)
Table 3/ 12b, HRMS Spectrum
Table 6/ 24c, 1H NMR (in CDCl3)
Table 6/24c, 13C NMR (in CDCl3)
Table 6/24c, DEPT (135°) (in CDCl3)
Table 6/ 24c, HMBC (in CDCl3)
Table 6/ 24c, HMQC (in CDCl3)
Table 6/ 24c, HRMS Spectrum
Table 3/ 5b, GCMS Spectrum
Table 3/ 13b, GCMS Spectrum
Table 3/13b’, GCMS Spectrum
Table 3/ 14b, GCMS Spectrum
Table 3/ 14b’, GCMS Spectrum
Oxidation of anthracene (28a) to anthraquinone (24c) monitored by
HPLC (at 280 nm):
Table 6/ Entry-28, HPLC chromatogram
HPLC chromatogram of standard 9,10-anthraquinone
3