S. Velusamy, T. Punniyamurthy / Tetrahedron Letters 45 (2004) 4917–4920
4919
Table 2 (continued)
Entry
Aldehyde
Alcohol
EtOH
Time (h)
0.4
Product
Yielda;b (%)
CH(OEt)2
10
11
74
CHO
CH(OMe)2
MeOH
0.3
75
12
13
EtOH
0.4
3.5
70
90
CH(OEt)2
MeOH
H11C5
CHO
H11C5
H11C5
CH(OMe)2
14
EtOH
4.0
82
CH(OEt)2
a A solution of CoCl2 (5 mol %), aldehyde (1 mmol), and alcohol (4 mL) was refluxed for the appropriate time using a CaCl2 guard tube.
b Isolated yield.
OMe
MeO
<1%
O
CH(OMe)2
CoCl2
CHO
+
+
+ H2O
ROH
2 h
77%
MeO OMe
+ H2O
+
CH(OMe)2
O
-do-
+
CHO
3.5 h
88%
<1%
Scheme 2.
5. Wenkert, E.; Goodwin, T. E. Synth. Commun. 1977, 7,
409.
6. Tsunoda, T.; Suzuki, M.; Noyori, R. Tetrahedron Lett.
1980, 21, 1357.
7. Zajac, W. W.; Byrne, K. J. J. Org. Chem. 1970, 35, 3375.
8. Hassner, A.; Wiederkehr, R.; Kascheres, A. J. J. Org.
Chem. 1970, 35, 1962.
In conclusion, a simple, efficient, and eco-friendly pro-
tocol is described for the chemoselective acetalization of
aldehydes with alcohols using the cheap and water tol-
erant CoCl2 as a catalyst. It does not involve additives
and the catalyst can be recycled without loss of activity.
Removal of water is not warranted in these reactions.
9. Fife, T. H.; Jao, L. K. J. Org. Chem. 1965, 39, 2565.
10. Bornstein, J.; Bedell, S. F.; Drummond, P. E.; Kopsloski,
C. L. J. Am. Chem. Soc. 1956, 78, 83.
Acknowledgements
11. Patwardhan, S. A.; Dev, S. Synthesis 1974, 348.
12. Karimi, B.; Ashtiani, A. M. Chem. Lett. 1999, 1199.
13. Firouzabadi, H.; Iranpoor, N.; Karimi, B. Synlett 1999,
321.
This work was supported by the Department of Science
and Technology (sanction no. SR/S1/OC-092002), New
Delhi and Council of Scientific and Industrial Research
(sanction no. 01(1804)/02/EMR-II), New Delhi.
14. Rh(III)triphos moieties: (a) Ott, J.; Tombo, G. M. R.;
Schmit, B.; Venanzi, L. M.; Wang, G.; Ward, T. R.
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References and notes
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