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S. Chandrasekhar et al. / Tetrahedron Letters 45 (2004) 5497–5499
Table 1. Reductive etherification of carbonyl compounds with alkyl trimethylsilyl ethers using PMHS and B(C6F5)3
Entry
Substrates
Product
Yield (%)a
I
II
p-MeOC6H4CHO
C6H5CHO
C6H11CHO
R1OPMB
85
85
81
84
88
R1
OTMS
R1OBn
)
1
R1OCH2C6H11
R1OCH2C6H4-p-NO2
R1O(CH2)3C6H5
R1 =
p-NO2C6H4CHO
3-C6H5CH2CH2CHO
OTMS
2
3
C6H5COCH3
C6H5COCH3
78
70
OBn
OTMS
OTMS
OPMB
MeO
MeO
CH2OPMB
4
5
CHO
75
p-MeOC6H4CHO
C6H5CHO
C6H11CHO
R2OPMB
R2OBn
R2OCH2C6H11
80
83
82
R2
OTMS
(
OTHP
R2 =
R3
OTMS
)
6
p-MeOC6H4CHO
C6H5CHO
C6H11CHO
R3OPMB
R3OBn
R3OCH2C6H11
82
82
80
R3 =
R4
OTMS
7
p-MeOC6H4CHO
C6H5CHO
C6H11CHO
R4OPMB
R4OBn
R4OCH2C6H11
85
90
80
R4 =
(
a Isolated yields of the product is after purified by column chromatography.
furnished the corresponding ethers with both aliphatic
and aromatic aldehydes with excellent yields.
References and notes
1. (a) Robert, A. W. J.; Rose, M. E. Tetrahedron 1979, 35,
2169; (b) Brosa, C.; Ferrer, J. C.; Malet, C.; Amezaga, J.
J. Org. Chem. 1989, 54, 3984; (c) Eberle, M. K.; Nuninger,
F. Tetrahedron Lett. 1994, 35, 6477; (d) Davis, R.;
Muchowski, J. M. Synthesis 1982, 987.
2. (a) Iversion, T.; Bundle, D. R. J. C. S. Chem. Commun.
1981, 1240; (b) White, J. D.; Reddy, G. N.; Spessard, G.
D. J. Am. Chem. Soc. 1988, 110, 1624; (c) Keck, G. E.;
Andrus, M. B.; Romer, D. R. J. Org. Chem. 1991, 56, 417;
(d) White, J. D.; Kawasaki, M. J. Org. Chem. 1992, 57,
5292.
3. (a) Doyle, M. P.; DeBruyn, D. J.; Kooistra, D. A. J. Am.
Chem. Soc. 1972, 94, 3659; (b) West, C. T.; Donnelly, S. J.;
Kooistre, D. A.; Doyle, M. P. J. Org. Chem. 1973, 38,
2675; (c) Doyle, M. P.; West, C. T. J. Org. Chem. 1975, 40,
3821; (d) Doyle, M. P.; West, C. T. J. Org. Chem. 1975, 40,
3829; (e) Doyle, M. P.; West, C. T. J. Org. Chem. 1975, 40,
3835.
4. (a) Tsunoda, T.; Suzuki, M.; Noyori, R. Tetrahedron Lett.
1979, 20, 4679; (b) Tsunoda, T.; Suzuki, M.; Noyori, R.
Tetrahedron Lett. 1980, 21, 1357.
In conclusion, PMHS in the presence of 1 mol %
B(C6F5)3 has been proved to be a useful system for
reductive etherification of carbonyl compounds with
various TMS ethers.
General experimental procedure. To a stirred solution of
the carbonyl compound (2 mmol) and the TMS ether
(2 mmol) in dry dichloromethane (5 mL) was added
B(C6F5)3 (10 mg, 0.02 mmol) and PMHS (240 mg,
4 mmol). The reaction mixture was stirred at room
temperature for 5 h. After completion of the reaction,
water was added to the reaction mixture, which was
extracted with dichloromethane (3 · 5 mL). The com-
bined organic layers were washed with brine, dried over
anhydrous Na2SO4, concentrated in vacuo and purified
by column chromatography.
Acknowledgements
5. Kato, J.; Iwasawa, N.; Mukaiyama, T. Chem. Lett. 1985,
743.
G.C.S., B.N.B. and K.V. give their thank to CSIR and
S.C.S, K.V.R thanks the DST for funding the project.
6. (a) Sassaman, M. B.; Kotian, K. D.; Suryaprakash, G. K.;
Olah, G. A. J. Org. Chem. 1987, 52, 4314; (b) Hartz, N.;