LETTER
Immobilization of TEMPO Derivatives in Saponite
1113
1
4
-Ammonia-2,2,6,6-tetramethyl-piperidine-1-oxyl Radical
chromatography or H NMR spectroscopy. The catalyst was subse-
quently reused.
Chloride (1)
4
9
-Amino-2,2,6,6-tetramethyl-piperidine-1-oxyl radical (1.61 g,
.39 mmol) was diluted in Et O (30 mL) and was washed with HCl
Typical Oxidation of Benzyl Alcohol Using Catalyst System
1@saponite
2
(
aq, 1 M, 3 × 5 mL). The aqueous layers were combined, and the
solvent was removed under reduced pressure. Compound 1 was ob-
According to GP2 with 1@saponite (45% CEC, 0.45 mmol/g, 50.0
mg, 22.5 mmol 1, 4.5 mol%), 1.25 mL of a solution of benzyl alco-
hol (0.400 M, 0.500 mmol) and hexadecane (0.400 M, 0.500 mmol)
in CH Cl , KBr (aq, 0.500 M, 0.100 mL, 50.0 mmol) and NaOCl (aq,
tained as red solid and was used without further purification.
IR (neat): 2926 (br s), 2365 (m), 2356 (m), 2339 (m), 1622 (m),
1
2
2
611 (m), 1522 (m), 1479 (m), 1391 (s), 1352 (w), 1243 (m), 1223
0
.350 M, buffered with NaHCO to a pH of 9.1, 1.79 mL, 0.627
3
(
(
w), 1178 (w), 1095 (m), 1057 (w9, 1018 (w), 953 (w), 886 (w), 744
m) cm .
–1
mmol). The reaction mixture was then shaken for 3 h. The conver-
sion of the reaction was determined by means of GC chromatogra-
phy. The catalyst was reused 10 times.
+
+
HRMS (ESI ): m/z calcd for [M – Cl] : 172.1570; found:
1
72.15685.
4
-Ethylammonia-2,2,6,6-tetramethyl-piperidine-1-oxylRadical
Acknowledgment
Iodide (2)
A.S. thanks Novartis Pharma AG for financial support (Novartis
Young Investigator Award). Support by the IRTG ‘Complex
Functional Systems in Chemistry’ (WWU Münster-Nagoya Uni-
versity) and the SFB 858 are most gratefully acknowledged. W.H.
thanks the Fonds der Chemischen Industrie for a doctoral fel-
lowship.
4
4
-Amino-2,2,6,6-tetramethyl-piperidine-1-oxyl radical (700 mg,
.09 mmol) was dissolved in ethyl iodide (5.00 mL, 62.5 mmol) and
was stirred at r.t. for 72 h. The resulting solid was filtered off. Re-
crystallization (MeCN–PhMe) gave 2 as red crystalline solid (913
mg, 2.79 mmol, 68%).
IR (neat): 2971 (s), 2947 (s), 2850 (m), 2823 (m), 2361 (w), 1572
(
1
w), 1441 (m), 1321 (w), 1369 (w), 1329 (w), 1314 (w), 1243 (m),
192 (m), 1031 (m), 923 (w) cm .
–
1
References
+
+
HRMS (ESI ): m/z calcd for [M – I] : 200.1883; found: 200.1900.
(
1) Immobilization of catalysts: (a) Fraile, J. M.; García, J. I.;
Mayoral, J. A. Chem. Rev. 2009, 109, 360. (b) Trindade, A.
F.; Gois, P. M. P.; Afonso, C. A. M. Chem. Rev. 2009, 109,
4
-Diethyl-methyl-ammonia-2,2,6,6-tetramethyl-piperidine-1-
oxyl Radical Iodide (3)
Iodomethane (2.30 mL, 36.9 mL) was added to 4-diethylamino-
,2,6,6-tetramethylpiperidine-1-oxyl radical (677 mg, 2.98 mmol).
The mixture was stirred 12 h at r.t. The resulting solid was suspend-
ed in Et O (10 mL), filtered off and washed with Et O (5 × 10 mL).
Recrystallization (MeCN–PhMe) gave 3 as a red crystalline solid
836 mg, 2.27 mmol, 76%).
418. (c) Akiyama, R.; Kobayashi, S. Chem. Rev. 2009, 109,
594.
2
(
2) Immobilization of organocatalysts: (a) Benaglia, M.;
Puglisi, A.; Cozzi, F. Chem. Rev. 2003, 103, 3401.
2
2
(b) Benaglia, M. New J. Chem. 2006, 30, 1525. (c) Cozzi,
F. Adv. Synth. Catal. 2006, 348, 1367. (d) Gruttadauria, M.;
Giacalone, F.; Noto, R. Chem. Soc. Rev. 2008, 37, 1666.
(
IR (neat): 2992 (w), 2361 (w), 1608 (m), 1478 (m), 1454 (s), 1438
m), 1410 (w), 1396 (w), 1370 (m), 1345 (m), 1329 (m), 1273 (m),
(3) Review on the use of TEMPO in synthesis: (a) Vogler, T.;
Studer, A. Synthesis 2008, 1979. Reviews on
(
1
8
244 (s), 1202 (s), 1184 (m), 1135 (w), 1101 (w), 1018 (s), 923 (w),
98 (s), 827 (s), 795 (m) cm .
immobilization of catalyst into nanostructured supports,
see: (b) Fraile, J. M.; García, J. I.; Herrerías, C. I.; Mayoral,
J. A.; Pires, E. Chem. Soc. Rev. 2009, 38, 695. (c) Fraile, J.
M.; García, J. I.; Mayoral, J. A. Chem. Rev. 2009, 109, 360.
–
1
+
+
HRMS (ESI ): m/z calcd for [M – I] : 242.2351; found: 242.2353.
(
4) Immobilization of TEMPO: (a) Bolm, C.; Fey, T. Chem.
Commun. 1999, 1795. (b) Dijksman, A.; Arends, I. W. C. E.;
Sheldon, R. A. Chem. Commun. 2000, 271. (c) Fey, T.;
Fischer, H.; Bachmann, S.; Albert, K.; Bolm, C. J. Org.
Chem. 2001, 66, 8154. (d) Dijksman, A.; Arends, I. W. C.
E.; Sheldon, R. A. Synlett 2001, 102. (e) Weik, S.;
General Procedure for the Intercalation of TEMPO Salts into
Layered Saponite Clay (GP1)
The intercalation was carried out by suspending the clay (500 mg,
1
.1 mmol, 0.5 mequiv) in an aqueous solution of the nitroxide am-
monium salt (60 mL, 1.25 mmol) and stirring for 4 h at r.t. That
means that 1.25 mmol of nitroxide was offered to saponite clay, cor-
responding to 250% CEC. The clay was filtered off and dried for 48
h in vacuo. The amount of intercalated material was quantified by
CHN elemental analysis.
Nicholson, G.; Jung, G.; Rademann, J. Angew. Chem. Int.
Ed. 2001, 40, 1436. (f) Ciriminna, R.; Bolm, C.; Fey, T.;
Pagliaro, M. Adv. Synth. Catal. 2002, 344, 159. (g) Ansari,
I. A.; Gree, R. Org. Lett. 2002, 4, 1507. (h) Testa, M. L.;
Ciriminna, R.; Hajji, C.; Garcia, E. Z.; Ciclosi, M.; Arques,
J. S.; Pagliaro, M. Adv. Synth. Catal. 2004, 346, 655.
General Procedure for Oxidation Reactions of Alcohols by
Using TEMPO Ammonium Salts that Are Immobilized into
Layered Saponite Clay (GP2)
The immobilized TEMPO ammonium salt (4.1–5.0 mol%) was
added to a reaction vessel which was equipped with a frit to filter
off the reaction mixture directly. A solution of the alcohol (0.400 M,
(
i) Ferreira, P.; Phillips, E.; Rippon, D.; Tsang, S. C.; Hayes,
W. J. Org. Chem. 2004, 69, 6851. (j) Pozzi, G.; Cavazzini,
M.; Quici, S.; Benaglia, M.; Dell’Anna, G. Org. Lett. 2004,
6, 441. (k) Ferreira, P.; Hayes, W.; Phillips, E.; Rippon, D.;
Tsang, S. C. Green Chem. 2004, 6, 310. (l) Gilhespy, M.;
Lok, M.; Baucherel, X. Chem. Commun. 2005, 1085.
1
.0 equiv) and hexadecane (0.400 M, 1.0 equiv; as internal stan-
dard) in CH Cl , a solution of KBr (aq, 0.500 M, 0.10 equiv) and a
solution of NaOCl (0.350 M, buffered with NaHCO to a pH of 9.1,
1
shaken for 3–5 h at 0 °C. The reaction was stopped simply by filter-
ing off the catalyst from reaction mixture and washing with CH Cl
2
2
(
3
m) Jiang, N.; Ragauskas, A. Tetrahedron Lett. 2005, 46,
323. (n) Holczknecht, O.; Cavazzini, M.; Quici, S.;
Shepperson, I.; Pozzi, G. Adv. Synth. Catal. 2005, 347, 677.
o) Benaglia, M.; Puglisis, A.; Holczknecht, O.; Quici, S.;
3
.25 equiv) were added at 0 °C. The reaction mixture was then
(
2
2
Pozzi, G. Tetrahedron 2005, 61, 12058. (p) Geneste, F.;
Moinet, C.; Ababou-Girard, S.; Solal, F. New J. Chem. 2005,
(
3 × 2 mL). The phases were separated and the organic layer was
dried over MgSO . The conversion was determined by means of GC
4
29, 1520. (q) Kubota, J.; Ido, T.; Kuroboshi, M.; Tanaka, H.;
Synlett 2010, No. 7, 1110–1114 © Thieme Stuttgart · New York