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S.-S. Weng et al.
PAPER
was removed by filtration though a short pad of Celite®. The green
filtrate was concentrated and dried under reduced pressure at
100 °C to give Cu(DS)2 (C24H50CuO8S2, MW = 593) as a fine solid
powder, which was used directly for the thioacetalization reactions.
001-MY2). We thank Professor Chien-Tien Chen for providing
chemicals and for useful discussions.
References
ESI-MS: m/z = 616 [M + Na]+.
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General Procedure for the Thioacetalization of Aldehydes
To a suspension of an aldehyde (10 mmol) and 1,3-propanedithiol
(1136 mg, 10.5 mmol) in H2O (20 mL) was added Cu(DS)2 (5
mol%; 296 mg, 0.5 mmol) at r.t. under N2 atmosphere and vigorous
stirring (>1200 rpm). The resulting colloidal dispersion was stirred
at r.t. for an appropriate time (see Table 3) and the reaction was
monitored by TLC, 1H NMR spectroscopy, or GC-MS. After com-
pletion of the reaction, additional H2O (30 mL) was added to dilute
the reaction mixture. The diluted reaction mixture was centrifuged
for 30 min (4500 rpm) at r.t. and allowed to stand for a further 20
min. The supernatant aqueous solution was separated from the solid
(or syrup-like) product by filtration on a glass filter. The crude prod-
uct was washed, resuspended, and centrifuged with H2O (50 mL)
twice. The analytically pure product was obtained by high-vacuum
drying or by a Kugelrohr apparatus distillation (or sublimation) un-
1
der reduced pressure. The products were characterized by H and
13C NMR spectroscopy, and MS analysis, and the data were identi-
cal with those of authentic samples.15,26 The filtrated aqueous layer
contains the Cu(DS)2 which can be reused in subsequent thioacetal-
ization reactions.
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General Procedure for the Thioacetalization of Ketones or the
Transthioacetalization of O,O-Acetals
To a suspension of a ketone or an O,O-acetal (1 mmol) and 1,3-pro-
panedithiol (114 mg, 1.05 mmol) in H2O (2 mL) was added
Cu(DS)2 (5 mol%; 29.6 mg, 0.05 mmol) at r.t. (or 50 °C) under N2
atmosphere and vigorous stirring (>1200 rpm). The resulting colloi-
dal dispersion was stirred for an appropriate time (see Tables 4
and 5) and the reaction was monitored by TLC or 1H NMR spectros-
copy. After completion of the reaction, additional H2O (5 mL) was
added to dilute the reaction mixture. The diluted reaction mixture
was centrifuged for 30 min (4500 rpm) at r.t. and allowed to stand
for a further 20 min. The supernatant aqueous solution was separat-
ed from the solid (or syrup-like) product by filtration on a glass fil-
ter. The crude product was washed, resuspended, and centrifuged
with H2O (20 mL) twice. The analytically pure product was ob-
tained by high-vacuum drying or by a Kugelrohr apparatus distilla-
tion (or sublimation) under reduced pressure.
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Typical Procedure for the Competitive Thioacetalization of Al-
dehyde and Ketone
To a suspension of 4-acetylbenzaldehyde (148 mg, 1.0 mmol) and
Cu(DS)2 (5 mol%; 29.6 mg, 0.05 mmol) in H2O (2 mL) was added
1,3-propanedithiol (108 mg, 1.0 mmol) at r.t. under N2 atmosphere
and vigorous stirring (>1200 rpm), and the reaction was monitored
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min until the formyl group of the 4-acetylbenzaldehyde was totally
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1
consumed (determined by H NMR spectroscopy). The reaction
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(23) Firouzabadi, H.; Iranpoor, N.; Karimi, B. Synlett 1998, 739.
(24) Kazahaya, K.; Tsuneo, S.; Sato, T. Synlett 2004, 1640.
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mixture was diluted with H2O (30 mL) and centrifuged for 30 min
(4500 rpm) at r.t. The crude product was collected by filtration, then
washed with H2O, resuspended, and vacuum dried under reduced
pressure. The formyl-protected dithiane was obtained in 99% yield
and was identified by a comparison of its spectroscopic data with
those of an authentic sample.15
(27) De S, K. J. Mol. Catal. A: Chem. 2005, 232, 77.
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Acknowledgment
We acknowledge the National Science Council of the Republic of
China for financially supporting this research (98-2119-M-145-
Synthesis 2010, No. 9, 1493–1499 © Thieme Stuttgart · New York