M. Mart ꢀı n et al. / Tetrahedron Letters 45 (2004) 5559–5561
mixture (70:30 ratio in CDCl
5561
0.37
In summary, the conversion of sterically congested and/
or conjugate ketoxime groups to ketones can be
3
): colourless oil; R
f
(
1
C
90:10, hexanes/EtOAc); IR (film) 3300–3200, 3150, 1660,
À1
þ
122 cm
;
HRMS (+FAB): calcd for [M + H]
1
achieved in excellent yields with Me P/PySeSePy. This
3
11
H26NO
2
Si 232.1733, found 232.1734. Isomer E:
H
reagent combination, reported here for the first time, has
advantages with regard to Bu P/PhSSPh.
3
NMR (CDCl , 400 MHz): d 8.34 (br s, 1H), 4.38 (q,
3
J ¼ 6:4 Hz, 1H), 2.4–2.73 (m, 2H), 1.28 (d, J ¼ 6:4 Hz,
3
0
2
H), 1.16 (t, J ¼ 7:4 Hz, 3H), 0.88 (s, 9H), 0.07 (s, 3H),
3
1
3
.04 (s, 3H); C NMR (CDCl
, 100.6 MHz): d 164.9, 70.1
1
Acknowledgements
5.8, 22.1, 18.1, 17.3, 11.0, )4.8, )4.9. Isomer Z: H NMR
(
1
CDCl
H), 2.4–2.3 (m, 2H), 1.27 (d, J ¼ 6:4 Hz, 3H), 1.10(t,
3
, 400 MHz): d 8.74 (br s, 1H), 5.18 (q, J ¼ 6:4 Hz,
13
Thanks are due to the Ministerio de Ciencia y Tecno-
log ꢀı a for support. The senior author (J.V.) dedicates this
work to the late Prof. Barton, whom he met in Gif-sur-
Yvette in the fall of 1979.
J ¼ 7:4 Hz, 3H), 0.90 (s, 9H), 0.08 (s, 3H), 0.05 (s, 3H);
C
NMR (CDCl , 100.6 MHz): d 166.1, 63.7, 25.8, 22.3, 21.2,
3
18.1, 10.6, )4.9, )5.2. For the preparation of the
starting ketone, see: (a) Mart ꢀı n, R.; Romea, P.; Tey, C.;
Urp ꢀı , F.; Vilarrasa, J. Synlett 1997, 1414; (b) Ferrer oꢀ , M.;
Galobardes, M.; Mart ꢀı n, R.; Montes, T.; Romea, P.;
Rovira, R.; Urp ꢀı , F.; Vilarrasa, J. Synthesis 2000,
1608.
References and notes
1
. For leading references, see: (a) Gawley, R. E. Org. React.
988, 35, 1; (b) Maruoka, K.; Yamamoto, H. In Compre-
1
8. Typical procedure for the reduction of ketoximes to
0
hensive Organic Synthesis; Trost, B. M., Fleming, I.,
Winterfeldt, E., Eds.; Pergamon: Oxford, 1991; Vol. 6,
p 763; (c) Pinnick, H. W. Org. React. 1990, 38, 655; (d)
Larock, R. C. Comprehensive Organic Transformations;
Wiley-VCH: New York, 1999; p 1227; (e) Barton, D. H.
R.; Beaton, J. M.; Geller, L. E.; Pechet, M. M. J. Am.
Chem. Soc. 1961, 83, 4076; (f) Barton, D. H. R. Pure Appl.
Chem. 1968, 16, 1.
ketones with 2,2 -dipyridyl diselenide and trimethylphos-
phine. To a stirred solution of the oxime (1.0mmol) and
0
2,2 -dipyridyl diselenide (1.1 mmol) in THF (5 mL), at rt
under nitrogen, was added trimethylphosphine (1.0M
toluene solution, 2 mL, 2.2 mmol). The reaction was
monitored by TLC until no oxime remained, and then
water (1.0mL) was added. The resulting solution was
stirred at rt for 30min before removing the solvents under
vacuum. Isolation byMethod A . The resulting crude was
purified on silica gel by flash column chromatography
2
. For a review, see: (a) Corsaro, A.; Chiacchio, U.; Pistar ꢁa ,
V. Synthesis 2001, 1903; For some very recent papers, see:
(
2
b) Li, D.; Shi, F.; Guo, S.; Deng, Y. Tetrahedron Lett.
004, 45, 265 (ionic liquids on silica gel); (c) De, S. K.
Tetrahedron Lett. 2003, 44, 9055 (SiBr /wet silica gel); (d)
Narsaiah, A. V.; Nagaiah, K. Synthesis 2003, 1881
SbCl ); (e) Imanzadeh, G. H.; Hajipour, A. R.; Mallak-
pour, S. E. Synth. Commun. 2003, 33, 735 (KMnO
(CH
CH
2
Cl
Cl
2
) to provide pure ketone. Further elution with
0
2
2
/MeOH, 98:2, afforded 2,2 -dipyridyl diselenide.
4
Isolation byMethod B. The residue was partitioned
between a saturated NaHCO3 aqueous solution and
diethyl ether. The aqueous phase was extracted three
times with ether. The ethereal phases were combined, dried
(
5
4
/
alumina); (f) Lijser, H. J. P.; Fardoun, F. H.; Sawyer, J.
R.; Quant, M. Org. Lett. 2002, 4, 2325 (chloranil, hm); (g)
Hosseinzadeh, R.; Tajbakhsh, M.; Niaki, M. Y. Tetrahe-
dron Lett. 2002, 43, 9413 (2,6-dicarboxypyridinium chlo-
rochromate), and references cited therein; (h)
Chandrasekhar, S.; Gopalaiah, K. Tetrahedron Lett.
4
(MgSO ) and evaporated under vacuum to give the ketone
in a pure condition. By bubbling air through the remaining
aqueous phase and extracting with an organic solvent,
PySeSePy was recovered.
9. On TLC, ketone 1b was immediately and exclusively
noted, that is the imine was quickly hydrolysed on silica
gel, as could be expected.
2
3 2 2
002, 43, 4023 (HIO in CH Cl ); (i) Khazaei, A.; Vaghei,
R. G. Tetrahedron Lett. 2002, 43, 3073 (polymeric N,N-
dichloro sulfonamide), and references cited therein; (j)
Shirini, F.; Zolfigol, M. A.; Mallakpour, B.; Mallakpour,
S. E.; Hajipour, A. R.; Baltork, I. M. Tetrahedron Lett.
10. Representative procedure for the deoximation of 1a with
0
substoichiometric amounts of 2,2 -dipyridyl diselenide. To
0
a stirred solution of oxime 1a (50mg, 0.21 mmol) and 2,2 -
dipyridyl diselenide (20 mg, 0.064 mmol) in THF (1.5 mL),
at rt under nitrogen, was added trimethylphosphine (1.0M
toluene solution, 520 lL, 0.52 mmol). The reaction mix-
ture stirred at rt for 30min. The solvent was removed
under reduced pressure and the residue was purified by
2
4 2 2
002, 43, 1555 (Mg(HSO ) /SiO ); (k) Salehi, P.; Khodaei,
M. M.; Goodarzi, M. Synth. Commun. 2002, 32, 1259 (c-
picolinium chlorochromate); (l) Zhou, J.-F.; Tu, S.-J.; Feg,
J.-C. Synth. Commun. 2002, 32, 959 (HCOOH/SiO /MW).
2
3
. (a) Barton, D. H. R.; Motherwell, W. B.; Simon, E. S.;
Zard, S. Z. J. Chem. Soc., Perkin Trans. 1 1986, 2243; (b)
Barton, D. H. R.; Motherwell, W. B.; Simon, E. S.; Zard,
S. Z. J. Chem. Soc., Chem. Commun. 1984, 337; (c) Barton,
D. H. R.; Motherwell, W. B.; Zard, S. Z. Tetrahedron Lett.
flash silica gel chromatography (CH
(47 mg, 100%).
2 2
Cl ) to give 1b
11. On the other hand, the method has the disadvantage that
it cannot be applied to highly branched ketoximes, such as
camphor oxime, as they gave rise to fragmentation
products (nitriles). This is a feature of ketoximes with a
quaternary a-carbon atom, since strong activation or
dehydration conditions cause fragmentations with forma-
tion of tertiary carbenic ions: (a) Suginome, H.; Furuk-
awa, K.; Orito, K. J. Chem. Soc., Perkin Trans. 1 1991,
917, and references therein; (b) Kirihara, M.; Niimi, K.;
Momose, T. J. Chem. Soc., Chem. Commun. 1997, 599. In
our case (camphor oxime), fragmentation took place even
by adding the reagents at )78 °C. Moreover, other groups
1
984, 25, 3707; For related works, see: (d) Lukin, K. A.;
Narayanan, B. A. Tetrahedron 2002, 58, 215; (e) Urp ꢀı , F.;
Vilarrasa, J. Tetrahedron Lett. 1986, 27, 4623.
. For a classical review on this class of compounds, called in
general N-sulfenylimines, or sulfenimines, see: Craine, L.;
Raban, M. Chem. Rev. 1989, 89, 689.
. Review on trialkylphosphines: Valentine, D. H.; Hill-
house, J. H. Synthesis 2003, 317.
. Toshimitsu, A.; Owada, H.; Terao, K.; Uemura, S.;
Okano, M. J. Org. Chem. 1984, 49, 3796, and Ref. 6 cited
therein.
4
5
6
3
that also react with R P/RSSR should be previously
protected; for instance, in competition experiments we
noted that primary alcohols react more rapidly than
oximes.
7
. All the oximes were known compounds, save (S)-2-tert-
butyldimethylsilyloxi-3-pentanone oxime (5a), an E–Z