References
1
Hudlicky M.
Oxidations in Organic Chemistry
American Chemical Society;
Washington DC:
1990.
2
Degonneau M.
Kagan ES.
Mikhailov VI.
Rozantsev EG.
Sholle VD.
Synthesis
1984,
895
3 LD50 (oral rat, 4-hydroxy-TEMPO) = 1053 mg Kg21; CAS database.
4
de Nooy A.
Besemer A.
van Bekkum H.
Synthesis
1996,
35:
1153
5
Anelli PL.
Biffi C.
Montanari F.
Quici S.
J. Org. Chem.
1987,
52:
2559
6
Zhao M.
Li J.
Mano E.
Song Z.
Tschaen DM.
Grabowski EJJ.
Reider PJ.
J. Org. Chem.
1999,
64:
2564
7
Einhorn J.
Einhorn C.
Ratajczak F.
Pierre JL.
J. Org. Chem.
1996,
61:
7452
8a
Cella JA.
Kelley JA.
Kenehan EF.
J. Org. Chem.
1975,
40:
1860
8b
Cella JA.
McGrath JP.
Kelley JA.
El Soukkary O.
Hilpert L.
J. Org. Chem.
1977,
42:
2077
9a
Anelli PL.
Biffi C.
Montanari F.
Quici S.
J. Org. Chem.
1989,
54:
2970
9b
Anelli PL.
Montanari F.
Quici S.
Org. Synth.
1990,
69:
212
10a
Heeres A.
van Doren HA.
Gotlieb KF.
Bleeker IP.
Carbohydr. Res.
1997,
299:
221
10b
Bolm C.
Fey T.
Chem. Commun.
1999,
1795
10c
Brunel D.
Lentz P.
Sutra P.
Fajula F.
Nagy JB.
Stud. Surf. Sci. Catal.
1999,
125:
237
10d
Verhoef MJ.
Peters JA.
van Bekkum H.
Stud. Surf. Sci. Catal.
1999,
125:
465
10e
Ciriminna R.
Blum J.
Avnir D.
Pagliaro M.
Chem. Commun.
2000,
1441
10f
Fey T.
Fischer H.
Bachmann S.
Albert K.
Bolm C.
J. Org. Chem.
2001,
66:
8154
11
Dijksman A.
Arends IWCE.
Sheldon RA.
Chem. Commun.
2000,
271
12a
Cornils B.
Catalysis from A to Z: A Concise Encyclopedia
Wiley-VCH;
Weinheim:
2000.
12b
Czarnik AW.
Solid Phase Organic Synthesis
Wiley;
New York:
2001.
13
Dijksman A.
Arends IWCE.
Sheldon RA.
Chem. Commun.
2000,
271
14
Tanyeli C.
Gümüs A.
Tetrahedron Lett.
2003,
44:
1639
15
Pozzi C.
Cavazzini M.
Quici S.
Benaglia M.
Dell’Anna G.
Org. Lett.
2004,
6:
441
16
Wasserscheid P.
Welton T.
Ionic Liquids in Synthesis
Wiley-VCH;
Weinheim:
2003.
17
Wierzbicki A.
Davis JH.
Proceedings of the Symposium on Advances in Solvent Selection and Substitution for Extraction, 5-9 March 2000
AIChE;
New York:
2000.
18
Fuller RT.
Carlin HC.
de Long HC.
Haworth D.
J. Chem. Soc., Chem. Commun.
1994,
299
19
General Procedure for the Attachment of One TEMPO Unit.
To a stirred solution of 4-hydroxy-2,2,6,6-tetramethyl-piperdine-1-oxyl (1, 0.86 g, 5 mmol) and chloroactic acid (0.40 g, 5 mmol) in CH2Cl2 (25 mL) at 0 °C under argon, DCC (1.03 g, 5 mmol) and DMAP (0.15 g, 1.25 mmol) were added and the reaction mixture was stirred for 12 h at r.t. The solid materials formed were filtered off and the filtrate was washed with 1 M HCl (5 mL) followed by sat. NaHCO3 (10 mL) and brine (10 mL). The organic phase was dried over MgSO4 and evaporated under reduced pressure, and then filtered through a short flash chromatography (EtOAc-hexanes 1:4) providing chloroacetic acid 2,2,6,6-tetra-methyl-1-oxy-piperidin-4-yl ester(2) as a red powder (1.14 g, 92%). Then 1-methylimidazole (0.46 g, 5.6 mmol) was added to a solution of 2 (1.00 g, 4 mmol) in MeCN (30 mL) and the resulting solution was stirred for 48 h at 80 °C. After that, the solvent was removed in vacuum and the residue was washed with acetone to give 3 as a light red powder (1.30 g, 98%). Compound 4 was prepared by stirring 3 (1.00 g, 3 mmol) with KPF6 (0.66 g, 3.6 mmol) in acetone (30 mL) at r.t. for 48 h. After this, the insoluble by-products were filtered off and the acetone was removed in vacuum to afford 4 as a pink powder (1.27 g, 96%). As excepted, this charged TEMPO 4 is preferentially soluble in [bmim]PF6 and insoluble in water. All these novel compounds were stable in air and characterized by 1H NMR, 13C NMR, FTIR spectro-metry, mass spectrometry and elemental analyses ref. 20.
20 To samples containing nitroxyl radical residues was added one drop of neat phenylhydrazine to the NMR sample tube immediately prior to analysis in order to reduce in situ the paramagnetic center to the corresponding hydroxylamine species.
Compound 2: mp 55 °C. 1H NMR (400 MHz, CDCl3): δ = 5.14 (s, 1 H), 4.10 (s, 2 H), 1.97 (t, 2 H, J = 0.8 Hz), 1.83 (t, 2 H, J = 1.2 Hz), 1.28 (s, 6 H), 1.14 (s, 6 H). 13C NMR (400 MHz, CDCl3): δ = 20.37, 31.93, 41.21, 43.29, 68.47, 166.79. IR (KBr, selected data): 1751.93, 1204.23, 1161.84, 791.67 cm-1. Anal. Calcd for C11H19ClNO3: C, 53.12; H, 7.70; Cl, 14.25; N, 5.63. Found: C, 53.17; H, 7.74; N, 5.67. MS (ESI): m/z calcd [M]+: 248.73; found: 248.40.
Compound 3: mp 191 °C. 1H NMR (400 MHz, DMSO): δ = 9.14 (s, 1 H), 7.54 (s, 1 H), 7.36 (s, 1 H), 5.24 (s, 2 H), 5.04 (s, 3 H), 3.90 (s, 3 H), 1.90 (t, 2 H, J = 0.8 Hz), 1.50 (t, 2 H, J = 1.2 Hz), 1.10 (s, 6 H), 1.07 (s, 6 H). 13C NMR (400 MHz, DMSO): δ = 166.43, 137.73, 123.66, 123.27, 68.92, 57.93, 49.54, 43.37, 35.89, 32.06, 20.32. IR (KBr, selected data): 1745.13, 1175.20, 1221.89 cm-1. Anal. calcd for C15H25ClN3O3: C, 54.46; H, 7.62; N, 12.70. Found: C, 54.58; H, 7.59; N, 12.72. MS (FAB): m/z calcd [M]+: 295.38; found: 294.7.
Compound 4: mp 53 °C. 1H NMR (400 MHz, DMSO): δ = 9.04 (s, 1 H), 7.36 (s, 1 H), 7.27 (s, 1 H), 5.20 (s, 2 H), 5.04 (s, 3 H), 3.89 (s, 3 H), 1.91 (t, 2 H, J = 0.8 Hz), 1.50 (t, 2 H, J = 1.2 Hz), 1.10 (s, 6 H), 1.08 (s, 6 H). 13C NMR (400 MHz, DMSO): δ = 166.38, 137.69, 123.68, 123.29, 69.09, 58.03, 49.59, 43.41, 35.87, 32.09, 20.37. IR (KBr, selected data): 1745.13, 1225.18, 1178.83, 839.76 cm-1. Anal. calcd for C15H25F6N3O3P: C, 40.91; H, 5.72; N, 9.54; P, 7.03. Found: C, 40.81; H, 5.62; N, 9.30; P, 7.23. MS (FAB): m/z calcd [M]+: 295.38; found: 294.9.
21
Anelli PL.
Biffi C.
Montanari F.
Quici S.
J. Org. Chem.
1987,
52:
2559
22
General Procedure for all Oxidation Runs.
An alcohol (0.80 mmol), 4 (0.008 mmol, 3.54 mg) and dodecane (0.24 mmol) used as the internal standard in GC-analysis were dissolved in [bmim]PF6 (2 mL) followed by 0.16 mL aq KBr (0.5 M). After cooling the mixture at 0 °C, 2.7 mL of aq NaOCl diluted to a concentration of 0.37 M and buffered to pH 8.6 by NaHCO3 was added and the reaction mixture stirred vigorously. After the oxidation, the IL phase was separated and the resultant carbonyl compounds could easily be separated from the IL medium by simple extraction with Et2O (4 × 5 mL), which was analyzed by GC. The IL containing catalyst can subsequently be re-used for a new reaction cycle. The combined organic extracts were dried with Na2SO4, and evaporated to dryness. The residue was purified by silica gel flash chromatography eluting with EtOAc-petroleum ether.