1598
D. Geißlmeir et al.
higher reactivity of allyl and benzyl alcohols connected to the stabilization of the
intermediary formed radical species and the observed diastereomerization of allyl
alcohols favor the Sheldon radical mechanism.
Experimental
All chemicals were obtained from commercial suppliers and were used without further purification.
Reaction products were identified and quantified by GC analysis using a Hewlett Packard 5890 series II
gas chromatograph with FID detection equipped with a DB-1 column (30 m ꢂ 0.53 mm) or by HPLC
analysis using a Hewlett Packard 1050 LC system with UV detection (210nm) equipped with a Zorbax
Eclipse-XDB C8 column (4.6ꢂ 150 mm). Compounds were identified by comparison of the retention
times with commercially available references and quantified using nitrobenzene as internal standard, or
by external calibration.
Typical Oxidation Procedure
The oxidation of the alcohols was carried out under O2 in a 100 cm3 double jacketed vessel, thermo-
stated at 25ꢁC and equipped with a magnetic stirrer, thermometer, and pH-electrode. Cu powder
(16 mg, 0.25 mmol) were suspended in 60cm3 CH3CN=H2O 2=1, 195.5 mg 2,20-bipyridine
(1.25 mmol) were added, and the reaction mixture was stirred for 30min whereby it turned deep
red. Then 390 mg TEMPO (2.5mmol) and 200mm3 NaOH 40% were added and the reaction was
started by addition of 50mmol alcohol. During the reaction the pH-value was kept between 12.5 and
13.5 by addition of small amounts of NaOH 40%. Samples to monitor the progress of the reaction were
taken out regularly, acidified with acetic acid, and extracted with CH2Cl2 followed by derivatization
with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) if necessary.
Oxidation Procedure Using Immobilized TEMPO
The oxidation was carried out in a 500 cm3 double jacketed vessel (Schmizo), thermostated at 25ꢁC,
and equipped with reflux condenser, KPG stirrer, gas tube with frit por. 1, and pH-electrode. (TEMPO-
4-oxymethyl)polystyrene (7.5g, 2.5mmol TEMPO=g), 596 mg Cu (9.34 mmol), and 2.93g 2,20-bipyr-
idine (18.76mmol) were suspended in 500 cm3 CH3CN=H2O 2=1 and stirred for 45min. Then
40.6g benzylalcohol (375mmol) were added and O2 was bubbled through the reaction mixture
(0.3dm3=min). During the reaction the pH-value was kept between 12.5 and 13.5 by addition of small
amounts of NaOH 40%. Samples to monitor the progress of the reaction were taken out regularly,
acidified with acetic acid, and extracted with CH2Cl2 followed by derivatization with BSTFA. Reac-
tions were stopped at a conversion between 80% and 90% and the reaction mixture was removed.
(TEMPO-4-oxymethyl)polystyrene was washed with 300 cm3 CH3CN=H2O 2=1 and reused for suc-
ceeding experiments.
References
[1] Hudlicky M (1990) Oxidations in Organic Chemistry. ACS, Washington DC
[2] Mancuso AJ, Huang SL, Swern D (1978) J Org Chem 43: 2480
[3] Dess DB, Martin JC (1983) J Org Chem 48: 4155
[4] Dess DB, Martin JC (1991) J Am Chem Soc 113: 7277
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[5] Semmelhack MF, Schmid CR, Cortes DA, Chou CS (1984) J Am Chem Soc 106: 3374
[6] Betzemeier B, Cavazzini M, Quici S, Knochel P (2000) Tetrahedron Lett 41: 4343
[7] Ragagnin G, Betzemeier B, Quici S, Knochel P (2002) Tetrahedron 58: 3985
[8] (a) Ansari IA, Gree R (2002) Organic Letters 4: 1507; (b) Jiang N, Ragauskas AJ (2005)
Tetrahedron Lett 46: 3323
[9] Cecchetto A, Fontana F, Minisci F, Recupero F (2001) Tetrahedron Lett 42: 6651