J. CHEM. RESEARCH (S), 1999 287
eluting with EtOAc^light petroleum (bp 30^60 ꢁC) (10/90). The
oxidized compounds were identi¢ed by comparison with commercial
samples (TLC, IR, 1H NMR).
groups forms a new chromium complex which is soluble in
DCE.15 Similarly, PDC is insoluble in BTF, even at 100 8C,
but is dissolved by the addition of 2 equiv. of Adogen 464.
Our ¢rst experiments, carried out on secondary benzylic
alcohols, were encouraging (runs 1^3 in Table 1); using
BTF rather than DCE, conversions and yields were indeed
increased, and high selectivities18 were preserved. Similar
observations were made in the oxidation of primary benzylic
alcohols: the corresponding aldehydes were cleanly obtained
and the overoxidation to acids was negligible (runs 4 and
5). As previously noted,16 the oxidation of an
a-functionalized benzylic alcohol such as methyl mandelate
led mainly to cleavage compounds (run 6). The oxidation
of primary and secondary allylic alcohols yielded aldehydes
and ketones, respectively, with good selectivities (runs 7^9).
As in DCE,4 saturated secondary alcohols were resistant to
oxidation in BTF (runs 10 and 11). In contrast, the oxidation
of hexadecan-1-ol was much more e¡ective under these
new conditions and, furthermore, highly selective (run 12).
We are grateful to S. A|t-Mohand for preliminary studies17
and to Rhone-Poulenc Industrialisation for a generous gift
of benzotri£uoride. We thank Dr. G. Bird (Zeneca Pharma,
Reims) for help with the text of the manuscript.
Received, 26th October 1998; Accepted, 18th December 1998
Paper F/8/09937E
Reference and notes
1
Part of this work was presented as a poster at XIth Inter-
national Symposium on Homogeneous Catalysis; 12^17 July,
1998; St Andrews, Scotland.
2
For reviews including parts of our studies: ꢀa J. Muzart,
Chem. Rev., 1992, 92, 113; ꢀb J. Muzart, Synthesis, 1993,
11; ꢀc J. Muzart, Synthesis, 1995, 1325.
3
4
5
S. Bouquillon, S. A|t-Mohand and J. Muzart, Eur. J. Org.
Chem., 1998, 2599.
When
a smaller ammonium salt such as tetrabutyl-
J. Muzart and S. A|t-Mohand, Tetrahedron Lett., 1994, 35,
1989.
J. Muzart and S. A|t-Mohand, Tetrahedron Lett., 1995, 36,
5735.
ammonium bromide was used instead of Adogen 464, the
oxidation of indan-1-ol was less e¡ective (run 13). The
presence of a long alkyl substituent on the nitrogen atom
of the ammonium salt was already required for good
e¤ciency of the procedure in DCE.15
When indane, tetraline and £uorene were subjected to
similar experimental conditions, we observed the ready
oxidation of their benzylic methylene groups, a¡ording the
corresponding ketones with fair yields (runs 14 to 16).
However, the same procedure induced only a low conversion
of diphenylmethane (run 17). Surprisingly, the oxidation of
ethylbenzene led to many compounds.
In conclusion, the use of BTF is compatible with that of
SPC and chromium oxides, even at its re£ux temperature.
Furthermore, we can state that BTF is not only a replacement
for 1,2-dichloroethane but it can also improve the e¤ciency of
the chromium-catalyzed oxidations by sodium percarbonate.
6
7
E. J. Corey and G. Schmidt, Tetrahedron Lett., 1979, 20, 399.
Adogen 464 is a registered trademark of Ashland Chemical Co.
for methyltrialkyl(C8 C10) ammonium chloride.
A. Ogawa and D. P. Curran, J. Org. Chem., 1997, 62, 450.
ꢀa D. P. Curran, Chemtracts-Org. Chem., 1996, 9, 75; ꢀb D.
P. Curran and S. Hadida, J. Am. Chem. Soc., 1996, 118, 2531;
ꢀc D. P. Curran and M. Hoshim, J. Org. Chem., 1996, 61,
6480.
8
9
10 Chem. Eng. News, 1997, 75 (Feb. 24), 31.
11 K. S. Ravikumar, J. P. Begue and D. Bonnet-Delpon,
Tetrahedron Lett., 1998, 39, 3141.
12 K. S. Ravikumar, F. Barbier, J. P. Begue and D.
Bonnet-Delpon, Tetrahedron, 1998, 54, 7457.
13 A. Hanyu, E. Takezawa, S. Sakaguchi and Y. Ishii,
Tetrahedron Lett., 1998, 39, 5557.
14 The boiling point of BTF is 102 8C while DCE boils at 83 8C.
Preliminary experiments using BTF as solvent have shown that
reactions carried out at 83 or 102 8C lead to similar results.
15 J. Muzart and S. A|t-Mohand, New. J. Chem., 1995, 19, 207.
16 S. A|t-Mohand, A. Levina and J. Muzart, Synth. Commun.,
1995, 25, 2051.
Experimental
Reagents and commercial substrates were used as received. Some
alcohols were obtained by reduction of the corresponding ketones
by NaBH4 in MeOH. Home-made plates (silica gel 60 PF254366 from
Merck) were used for preparative thin-layer chromatography.
17 S. A|t-Mohand, Ph.D. Thesis, University of Reims
Champagne-Ardenne, 1997.
Typical Oxidation Procedure.öIn a 25 ml round-bottomed £ask
containing PDC (38 mg, 0.1mmol) and Adogen 464 (81mg,
*0:2 mmol) was added BTF (10 ml). After complete dissolution
of the chromium complex at re£ux temperature were added SPC
[either 628 or 1256 mg, 4 or 8 mmol, see reactions (1) and (2)]
and the substrate (1mmol). The mixture was stirred and boiled under
re£ux in an atmosphere of air for 24 h, then cooled to room tem-
perature and ¢ltered. The ¢ltrate was evaporated under reduced
pressure.19 The residue was taken up with a small amount of
CH2Cl2 and then subjected to preparative thin-layer chromatography,
18 Selectivity represents the yield based on the amount of
substrate consumed.
19 Following a referee's remark regarding the recoverability of the
solvent, preparative experiments were carried out using 8 mmol
of indan-1-ol in 80 ml of BTF. Some BTF (55^60 ml) was thus
recovered by distillation of the ¢ltrate under atmospheric
pressure. After complete evaporation of the solvent under
reduced pressure, the residue was subjected to £ash
chromatography, eluting with EtOAc^light petroleum (bp
30^60 8C) (20/80).
Delaval, Nicolas
