H. Firouzabadi et al.
Bull. Chem. Soc. Jpn., 74, No. 12 (2001) 2405
Scheme 4.
NMR (CDCl3, 62.90 MHz) δ 25.69, 33.55, 44.23, 56.15, 56.85,
112.55, 114.44, 114.93, 128.58, 149.99, and 154.29.
rates, easy work-up, high chemoselectivity of the method, and
high yields of the products are worth mentioning as advantages
of the presented method.
2-(2-Methoxyphenyl)-1,3-dithiane: 1H NMR (CDCl3, 250
MHz) δ 1.84–2.08 (m, 2H), 2.79–3.06 (m, 4H), 3.74 (s, 3H), 5.61
(s, 1H), 6.78 (d, 1H), 6.90 (t, 1H), 7.16 (t, 1H), and 7.50 (d, 1H).
13C NMR (CDCl3, 62.90 MHz) δ 25.75, 32.81, 44.04, 56.16,
111.17, 121.42, 127.73, 129.56, 129.81, and 155.83.
Experimental
General. All chemicals were either prepared in our laborato-
ries or were purchased from Fluka and Merck Companies. Be-
cause the products are known compounds, the elemental analyses
are not given in the text. Most of the products were purified by
column chromatography on silica gel 60 Mesh ASTM or recrystal-
lization from appropriate solvents and identified by comparisons
of their mp, IR, NMR, and mass spectra with those reported for
authentic samples. The progress of the reactions was followed by
TLC using silica-gel polygrams SIL G/UV 254 plates or by GC
using a Shimadzu gas chromatograph GC-14A, equipped with a
flame-ionization detector and a glass column packed with DC-200
stationary phase and nitrogen as the carrier gas. NMR spectra
were run on a Bruker Avance DPX 250 MHz instrument. Mass
spectra were recorded by GCMS-QP 1000 EX at 20 eV (Shimad-
zu).
2-(4-Bromophenyl)-1,3-dithiane:
1H NMR (CDCl3, 250
MHz) δ 1.86–2.11 (m, 2H), 2.81–3.03 (m, 4H), 5.05 (s, 1H), 7.32
(d, 2H), and 7.41 (d, 2H). 13C NMR (CDCl3, 62.90 MHz) δ 25.38,
32.30, 51.07, 122.73, 129.95, 132.22, and 138.50.
2-(4-Methylphenyl)-1,3-dithiane:
1H NMR (CDCl3, 250
MHz) δ 1.65 (s, 3H), 1.92–2.30 (m, 2H), 2.77–2.96 (m, 4H), 5.08
(s, 1H), 7.16 (d, 2H), and 7.28 (d, 2H). 13C NMR (CDCl3, 62.90
MHz) δ 21.59, 25.52, 32.54, 51.59, 128.00, 129.80, 136.57, and
138.60.
2-(5-Methylfuryl)-1,3-dithiane:
1H NMR (CDCl3, 250
MHz) δ 1.87–2.14 (m, 2H), 2.27 (s, 3H), 2.85–2.96 (m, 4H), 5.14
(s, 1H), 5.88 (d, 2H), and 6.21 (d, 2H). 13C NMR (CDCl3, 62.90
MHz) δ 14.41, 25.65, 30.77, 42.88, 106.98, 108.34, 150.16, and
152.39.
General Procedure for the Functional Group Transforma-
tion of Carbonyl Compounds, Acetals, and Acylals to the Cor-
responding 1,3-Dithianes. To a stirred mixture of the carbonyl
compound/acetal/acylal (10 mmol) and dithiol (11–17 mmol) or
monothiol (21 mmol), anhydrous LiOTf (0.5–3 mmol) was added.
The mixture was heated at 90 °C (or 110 °C for ketones) while
stirring was continued, and the progress of the reaction was fol-
lowed by TLC. After completion of the reaction, CH2Cl2 (20 mL)
was added to the mixture and was continuously extracted by a
continuous extractor. The resulting mixture was washed succes-
sively with a 10% NaOH solution (2 × 5 mL), brine (5 mL), and
water (10 mL). The organic layer was separated and dried over
anhydrous Na2SO4. Evaporation of the solvent under reduced
pressure gave an almost pure product. Further purification was
achieved by column chromatography on silica gel or recrystalliza-
tion from an appropriate solvent to give the desired product(s) in
good-to-excellent yield(s) (Table 1, and 3). The resulting 1,3-
dithianes were known compounds3f,t,4d,6 and were easily character-
ized by a comparison of their physical data with those of authentic
samples (spectroscopic data, mp). However, some spectroscopic
data for some of the isolated 1,3-dithianes (Table 3, entries 3, 18,
19, 20, 24) are given bellow:
The authors are thankful to the Shiraz University Research
Council for the partial support of this work.
References
1
a) T. W. Greene and P. G. M. Wuts, “Protective Groups in
Organic Synthesis,” 2nd ed, Wiley, New York (1991), pp. 178–
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B. M. Trost, Thieme, Stuttgart (1994).
2
a) E. J. Corey and D. Seebach, Angew. Chem., Int. Ed. En-
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3
For leading references for dithioacetalization of carbonyl
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2-(2,5-Dimethoxyphenyl)-1,3-dithiane: 1H NMR (CDCl3,
250 MHz) δ 1.91–2.15 (m, 2H), 2.81–3.18 (m, 4H), 3.67 (s, 3H),
3.75 (s, 3H), 5.60 (s, 1H), 6.74 (s, 2H), and 7.09 (s, 1H). 13C