Selective Transdithioacetalization of Acetals, Ketals, Oxathioacetals and Oxathioketals Catalyzed by Envirocat EPZ10 R

Article abstract of DOI:10.1039/a800864g

Envirocat EPZ10^R has been found to be a remarkable reusable heterogeneous catalyst for selective transdithioacetalization of acetals, ketals, oxathioacetals and oxathioketals with HSCH₂CH₂SH and HSCH₂CH₂

Full text of DOI:10.1039/a800864g

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452 J. CHEM. RESEARCH (S), 1998
J. Chem. Research (S),
1998, 452±453$
Selective Transdithioacetalization of Acetals, Ketals,
Oxathioacetals and Oxathioketals Catalyzed by
Envirocat EPZ10R$
A. S. Gajare,a M. S. Shingarea and B. P. Bandgar*b
aDept. of Chem., Dr. B.A.M.U., Aurangabad
bOrganic Chem. Res. Lab., School of Chemical Sciences, Swami Ramanand Teerth
Marathwada University, Dnyanteerth, Vishnupuri, Nanded - 431 602, India
Envirocat EPZ10R has been found to be a remarkable reusable heterogeneous catalyst for selective transdithio-
acetalization of acetals, ketals, oxathioacetals and oxathioketals with HSCH2CH2SH and HSCH2CH2CH2SH.
The protection of carbonyl group as a thioacetal is quite
often a necessary requirement in the synthesis of complex
multifunctional organic molecules1 since these sulfur func-
Scheme 1 R1, R2 ˆ alkyl, aryl, H, cyclic; X ˆ O, S; n ˆ 1, 2
tionalities are quite stable towards
a wide variety of
reagents.2 Dithioacetals are also useful in organic synthesis
as acyl carbanion equivalents in C0C bond-forming
reactions2 and as intermediates for the conversion of the
carbonyl function to the parent hydrocarbon.3 Numerous
methods have been reported for this conversion.
However, some of these methods su€er from harsh
conditions, expensive and hazardous reagents, sometimes
cumbersome extraction procedures and are ine€ective in the
case of hindered ketones. Although, there are chemoselective
methods for thioacetalization of aldehydes in the presence
of ketones, very little is known about transthioacetalisation
of acetals and ketals which is gaining prominence as a
newer method of choice.6 In this context, a solid supported
reusable catalyst would be more advantageous over classical
acids.
reagents supported on high surface area inorganic
materials.7 EnvirocatR, a new family of supported reagents,
is a breakthrough in environmentally friendly chemistry.8
Envirocat EPZ10R (clayzic) is such a supported catalyst
which exhibits both Bronsted and Lewis acid charac-
teristics.8
Here we report the application of Envirocat EPZ10R as
an ecient catalyst for selective transdithioacetalization of
acetals, ketals, oxathioacetals and oxathioketals with
ethane-1,2-dithiol and propane-1,3-dithiol (Scheme 1).
Envirocat EPZ10R catalyzes transdithioacetalization of
a variety of acetals and ketals (aliphatic, aromatic, a,b-
unsaturated) with ethane-1,2-dithiol (Table 1, entries 1±7,
9±13 and 15±20) in good yields. This method is not only
useful for transdithioacetalization of acetals and ketals but
also for oxathioacetal (entry 13) and oxathioketals (entries
In recent years, there has been a considerable growth in
interest in the catalysis of organic reactions by inorganic
Table 1 Transdithioacetalization of acetals, ketals and oxathioacetals with ethane-1,2-dithiol or propane-1,3-dithiol catalyzed by
Envirocat EPZ10R
Yielda
(%)
‡
Entry
1
Substrate
Product
MS (70 eV, 130 8C): M ˆ m/z (% rel. intensity)
85
61 (40), 69 (42), 79 (53), 105 (100), 148 (48)
2
72
59 (28), 71 (100), 103 (100), 132 (75)
3
4
90
91
58 (32), 105 (100), 147 (37), 162 (100)
74 (42), 106 (38), 119 (44), 134 (54)
5
6
95
65
58 (30), 71 (41), 81 (87), 131 (100), 146 (52), 173 (39)
77 (50), 93 (100), 126 (65), 158 (79), 186 (48)
7
68
59 (44), 105 (51), 117 (76), 161 (100), 176 (51), 199 (65), 268 (43)
11 and 20). The transdithioacetalization of acetal (entry 14)
and ketal (entry 8) was also achieved with propane-1,3-
dithiol in good yields. A special feature of this catalytic pro-
cess is that a,b-unsaturated acetals (entries 2 and 18) and
*To receive any correspondence.
$This is a Short Paper as de®ned in the Instructions for Authors,
Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there-
fore no corresponding material in J. Chem. Research (M).

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J. CHEM. RESEARCH (S), 1998 453
Table 1 Continued
Yielda
(%)
‡
Entry
8
Substrate
Product
MS (70 eV, 130 8C): M ˆ m/z (% rel. intensity)
83
81 (69), 95 (56), 137 (75), 159 (84), 244 (100)
9
78
84
55 (52), 131 (100), 197 (61), 230 (23)
10
60 (40), 71 (43), 83 (48), 98 (55), 115 (70), 131 (100), 197 (52),
258 (30)
11
12
73
75
77 (50), 92 (34), 135 (100), 212 (4)
100 (16), 121 (22), 151 (90), 226 (100)
13
14
89
91
58 (50), 120 (50), 166 (100), 196 (59), 227 (32)
75 (64), 112 (82), 155 (100), 216 (34)
15
16
17
95
92
91
103 (48), 115 (100), 147 (85), 179 (32), 208 (84)
60 (89), 77 (83), 105 (100), 121 (69), 165 (23), 196 (18)
60 (89), 77 (83), 105 (100), 121 (69), 165 (23), 196 (18)
aIsolated yield, characterized by IR, 1H NMR and MS.
Received, 2nd February 1998; Accepted, 5th May 1998
Paper E/8/00864G
ketals (entries 6 and 7) underwent transdithioacetalization
without a double bond shift or 1,4-addition. It is also note-
worthy that keto acetals undergo chemoselective trans-
dithioacetalization in preference to ketone protection in
excellent yield (entry 3). Even sterically hindered ketals
(entries 8 and 19) and oxathioketal (entry 20) have been
successfully transformed into dithioacetals in high yields.
The Envirocat EPZ10R catalyst was recovered and reused at
least four times without any loss of activity.
References
1 T. W. Greene amd P. G. M. Wuts, Protective Groups in Organic
Synthesis, John Wiley and Sons Inc., New York, 2nd edn., 1991.
2 D. Seeback and E. J. Corey, J. Org. Chem., 1975, 40, 231;
H. Hauptmann and M. M. Campos, J. Am. Chem. Soc., 1950, 72,
1405.
3 G. R. Petit and E. E. van Tamelen, Org. React., 1962, 12, 356.
4 P. K. Mandal and S. C. Roy, Tetrahedron Lett., 1995, 51, 7823
and references therein.
5 A. K. Maiti, K. Basu and P. Bhattacharyya, J. Chem. Res. (S),
1995, 108.
6 R. A. Moss and C. B. Mallon, J. Org. Chem., 1975, 40, 1368;
T. Satoh, S. Uwaya and K. Yamakawa, Chem. Lett., 1983, 667;
F. Bellesia, M. Boni, F. Ghel® and U. M. Pegnoni, Tetrahedron,
1993, 49, 199.
7 J. H. Clark, A. P. Kybett and D. J. Macquarrie, Supported
Reagents, VCH, New York, 1992.
8 J. H. Clark and D. J. Macquarrie, Chem. Soc. Rev., 1996, 303;
Product information of Contract Chemicals, England, 1994;
Envirocat EPZ10R was supplied by Contract Chemicals,
Experimental
Envirocat EPZ10R was procured from Contract Chemicals,
Merseyside, England, and activated 1 h prior to use by using a
Dean±Stark apparatus.
Typical Reaction Procedure.ÐA mixture of cinnamyl acetal
(5 mmol), ethane-1,2-dithiol (5 mmol) and Envirocat EPZ10R
(100 mg) in CH2Cl2 (15 ml) was re¯uxed for 4 h. After the reaction
was complete (TLC), the Envirocat EPZ10R catalyst was ®ltered o€
and washed with CH2Cl2 (3Â5 ml). The ®ltrate was washed with
5% NaOH and water. The organic layer was dried over anhydrous
sodium sulfate, concentrated and puri®ed by ¯ash chromatography
to give the 1,3-dithioacetal derivative (entry 18) in excellent yield
(95%).9
Merseyside, England.
9 Mp 59 8C; IR 2900±2800, 1440, 1370, 970 cm
1
;
1H NMR
(300 MHz, CDCl3) ꢀ 3.22±3.42 (m, 4 H), 5.22 (d, J ˆ 1, Hz, 1 H),
6.15±6.22 (dd, J ˆ 1, 2 Hz, 1 H), 6.52 (d, J ˆ 2 Hz, 1 H), 7.2±7.4
(m, 5 H); MS (70 eV, 130 8C); m/z (% rel. intensity): 208 (84), 179
(32), 147 (85), 115 (100), 103 (48).
We thank Contract Chemicals, England, for the generous
gift of Envirocat EPZ10R.