Deprotection of Thioacetals Using K S O =[bmim]Br
2 2 8
571
ꢁ
0
33650 (A.E.R.) from the National Institutes of Health, USA.
neutral conditions at 70–80 C in reaction times of 10–
2
Further financial support from the Center of Excellency in
Chemistry Research (IUT) is gratefully acknowledged.
5min provided products in high yields (75–90%).
To optimize the reaction conditions and evaluate
the synergy between K S O , ionic liquid, and sol-
2
2 8
vent-free conditions several experiments were done.
When we treated 1 mmol of 4-methoxyphenylthio-
lane with 1 mmol K S O in the absence of the
References
[
[
1] Groble BT, Seebach D (1977) Synthesis 357
2] Greene TW (1981) John Wiley and Sons, New York,
vol. 129, 311 pp
2
2 8
ionic liquid in refluxing acetonitrile the yield of 4-
methoxybenzaldehyde after 1 h refluxing was 45%.
Reaction of 4-methoxyphenylthiolane with 1 mmol
of K S O in the presence of a catalytic amount
[3] Guanti G, Banfi L, Brusco S, Riva R (1993) Tetrahedron
Lett 34: 8549
[4] a) Firouzabadi H, Iranpoor N, Karimi B (1999) Synth-
2
2
8
(
10 mmol%) of [bmim]Br in refluxing acetonitrile
esis 58; b) Seebach D, Corey EJ (1975) J Org Chem 40:
31; c) Groblel BT, Seebach D (1977) Synthesis 357; d)
Hatch RP, Shringarpure J, Weinreb SM (1978) J Org
Chem 43: 4172; e) Marshall JA, Belletire JL (1971)
Tetrahedron Lett 871
2
resulted in 4-methoxybenzaldehyde and 4-methoxy-
benzoic acid after 1 h in 35 and 15%. We also
reacted 1 mmol of 4-methoxyphenylthiolane with
1 mmol of K S O in the absence of ionic liquid
2 2 8
under solvent-free conditions grinding the latter re-
[5] Lebouc A, Simonet J, Gelas J, Dehbi A (1987) Synthesis
320
[
6] a) Firouzabadi H, Iranpoor N, Zolfigol MA (1998) Bull
Chem Soc Jpn 71: 2169; b)Varma RS, Saini RK (1997)
Tetrahedron Lett 38: 2633; c) Meshram HM, Reddy GS,
Yadav JS (1997) Tetrahedron Lett 38: 8891; d) Curini M,
Marcotullio MC, Pisani E, Rosati O (1997) Synlett 769;
e) Curini M, Ceccherelli P, Marcotullio MC, Epifano F,
Rosati O (1996) Synlett 767; f) Komatsu N, Taniguchi
A, Uda M, Suzuki H (1996) Chem Commun 1847;
g) Schmittel M, Levis M (1996) Synlett 315; h)
Haroutounian SA (1995) Synthesis 39; i) Hirano M,
Ukawa K, Yakabe S, Clark JH, Morimoto T (1997)
Synthesis 858; j) Lee JG, Hwang JP (1995) Chem Lett
507; k) Meshram HM, Reddy GS, Sumitra G, Yadav JS
action mixture in a mortar for 30 s and keeping it at
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7
0–80 C for 1 h. The yield of the conversion to the
corresponding benzaldehyde was 40%. Only in the
case of grinding a mixture of K S O in the presence
of a catalytic amount (10 mmol%) of [bmim]Br
2
2 8
ꢁ
at 65–70 C the deprotection of thioacetal to the
corresponding carbonyl compounds in low reaction
time was high.
In conclusion, we have developed a simple, mild,
inexpensive, and environmentally safe method for
the deprotection of S,S-acetals. High yields and short
reaction times are noteworthy features of the re-
ported method.
(1999) Synth Commun 29: 1113
[
[
[
7] Firouzabadi H, Hazarkhani H, Karimi B, Niroumand U,
Ghassamipour S (2000) Fourth International Electronic
Conference on Synthetic Organic Chemistry (ECSOC-4),
September 1–30
8] a) Tanaka K, Toda F (2000) Chem Rev 100: 1025; b)
Cave GW, Raston CL, Scott JL (2001) Chem Commun
Experimental
Typical Procedure for Dethioacetalization of p-Chlorophenyl-
2
2
159; c) Metzger JO (1998) Angew Chem Int Ed 37:
975
1
,3-dithiolane Using K S O =[bmim]Br
2 2 8
A mixture of 0.21g p-chlorophenyl-1,3-dithiolane (1mmol),
.27K S O (1mmol), and 0.03g [bmim]Br (10 mol%) was
ground for 1 min in a mortar with a pestle and kept at
9] Li CJ, Chan TH (1997) Organic Reactions in Aqueous
Media. John Wiley and Sons, New York
0
2
2 8
[
10] Oakes RS, Clifford AA, Rayner CM (2001) J Chem Soc
Perkin Trans 1: 917
11] (a) Welton T (1999) Chem Rev 99: 2071; b)
Wasserscheid P, Keim W (2000) Angew Chem Int Ed
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6
5–70 C for the time specified in Table 1. The progress of
the reaction was followed by TLC=GC. After the reaction was
completed (Table 1), filtration through a sintered glass funnel
followed by transfer into a separatory funnel and washing with
NaHCO (5%) drying (Na SO ), and removing the solvent
[
3
9: 3773
3
2
4
[
12] a) Sheldon R (2001) Chem Commun 2399; b) Namboo-
diriand VV, Varma RS (2002) Chem Commun 342; c)
Harjani JR, Nara SJ, Salunkhe MM (2002) Tetrahedron
Lett 43: 1127
under reduced pressure. The residue was purified through a
short column of silica gel (cyclohexane=EtOAc, 3=1) to obtain
0
.11g (78%) pure p-chlorobenzaldehyde.
[
13] a) Hajipour AR, Arbabian M, Ruoho AE (2002) J Org
Chem 67: 8622; b) Hajipour AR, Ruoho AE (2002) Org
Prep Proced Int 34: 647; c) Hajipour AR, Mazloumi G
(2002) Synth Common 32: 23; d) Hajipour AR, Ruoho
AE (2002) J Chem Res (s) 547; e) Hajipour AR, Adibi H,
Ruoho AE (2003) J Org Chem 68: 4553; f) Hajipour AR,
Acknowledgements
We gratefully acknowledge the funding support received for
this project from the Isfahan University of Technology (IUT),
IR Iran (A.R.H.), and Grants GM 033138, MH 065503, NS