Chemistry Letters 2001
581
Because N-tert-butylmethanesulfinamide (4c) gave the best
results concerning both O-alkylation and oxidation among sulfi-
namides examined, 4c has been used in the oxidation of alkyl
triflates since then. On the other hand, when O-alkylation of
dimethyl sulfoxide with octyl triflate was tried, the correspon-
ding dimethyl(octyloxy)sulfonium triflate was obtained in a
lower yield and a lower purity (70% yield, 73% purity). This
result indicated that O-alkylation of 4c proceeded more effi-
ciently than that of dimethyl sulfoxide. It was also advanta-
geous that the present oxidation proceeded smoothly at room
temperature, considering the fact that higher temperatures such
that ranging from 100 to 150 °C were required in the similar
oxidation by Kornblum using dimethyl sulfoxide.4
h at room temperature, the solvent was removed, and the
residue was washed with petroleum ether (5 mL × 5) and dried
in vacuo to afford 3c5 as a colorless oil (4.31 g). Purity of the
1
obtained 3c (99.8 wt% purity) was checked by H NMR analy-
sis using triphenylmethane as an internal standard and its yield
was estimated to be 95%.
To a stirred suspension of 3c (99.8% purity, 205 mg, 0.51
mmol) in toluene (1.5 mL) was added a solution of DBU (86
mg, 0.57 mmol) in toluene (2 mL) at room temperature and the
reaction mixture was stirred for 1 h at the same temperature.
Then, it was quenched with 1% aqueous HCl solution and the
resulting mixture was extracted with CH2Cl2. The yield of
octanal (5, 0.45 mmol, 88%) was determined by GC analysis
using an internal standard.
References and Notes
1
a) T. Mukaiyama, J. Matsuo, and M. Yanagisawa, Chem. Lett.,
2000, 1072. b) J. Matsuo, H. Kitagawa, D. Iida, and T.
Mukaiyama, Chem. Lett., 2001, 150.
Oxidation of various primary alkyl triflates to the corre-
sponding aldehydes was performed in two reactions, i. e. the
initial formation of alkoxy(N-tert-butylamino)(methyl)sulfoni-
um salts by the reaction of 4c, and the successive oxidation step
by using DBU (Table 2). In the cases of simple primary alkyl
triflates, the above oxidation proceeded very smoothly, and
alkyl triflates bearing chloro or ester functionality were also
oxidized in good yields by the present method (entries 2–6).
Thus, alkoxy(N-tert-butylamino)(methyl)sulfonium salts would
be regarded as stable precursors of the corresponding aldehy-
des. In the case of β-branched primary alkyl triflate, higher
temperature and longer reaction time (reflux, 3 h) were required
for the formation of sulfonium salt (entry 7). Also, a complicat-
ed mixture resulted when applied to phenacyl triflate (entry 8).
Typical experimental procedure is as follows (Table 1,
entry 3): to a stirred solution of N-tert-butylmethanesulfinamide
(4c, 2.99 g, 11.4 mmol) in CH2Cl2 (10 mL) was added a solu-
tion of octyl triflate (1.54 g, 11.4 mmol) in CH2Cl2 (15 mL) at
room temperature. After the reaction mixture was stirred for 42
2
a) H. Minato, K. Yamaguchi, and M. Kobayashi, Chem. Lett.,
1975, 991. b) H. Minato, K. Yamaguchi, K. Okuma, and M.
Kobayashi, Bull. Chem. Soc. Jpn., 49, 2590 (1976). c) M.
Mikolajczyk, B. Bujnicki, and J. Drabowicz, Bull. Acad. Pol.
Sci., Ser. Sci. Chim., 25, 267 (1977). d) H-U. Wagner and A.
Judelbaum, Angew. Chem., Int. Ed. Engl., 17, 460 (1978). e) H.
Minato, K. Okuma, and M. Kobayashi, J. Org. Chem., 43, 652
(1978). f) M. Haake and H. Gebbing, Synthesis, 1979, 98.
Sulfinamides (4a–i) were prepared from the corresponding
sulfinyl chlorides and amines.
3
4
5
N. Kornblum, W. J. Jones, and G. J. Anderson, J. Am. Chem.
Soc., 81, 4113 (1959).
1
3c: H NMR (270 MHz, CDCl3, Me4Si) δ 0.88 (3H, t, J = 7.1
Hz), 1.27–1.48 (10H, m), 1.42 (9H, s), 1.66–1.76 (2H, m), 3.39
(3H, s), 4.09 (1H, td, J = 6.4, 9.2 Hz), 4.27 (1H, td, J = 6.4, 9.2
Hz), 8.34 (1H, bs). 13C NMR (68 MHz, CDCl3) δ 13.78, 22.33,
25.12, 28.76, 28.90, 29.59, 31.42, 34.06, 34.11, 57.40, 69.08,
120.20 (q, J = 319 Hz). MS (FAB+) m/z 248 ([n-
BuOSMeNHtBu]+). MS (FAB–) m/z 149 (OTf–).