G. Sabitha et al. / Tetrahedron Letters 42 (2001) 3955–3958
3957
reaction was found to be highly regioselective giving the
Acknowledgements
corresponding 1-chloro- and 1-iodo-2-alkanols exclu-
sively in quantitative yields. This demonstrates the pre-
dominant attack of the reagent on the less hindered
carbon of the epoxides. As expected in the case of styrene
oxide (Table 1, entry 4), 2-chloro- and 2-iodo-2-
phenylethanols were obtained as the major products due
to the formation of the stabilized benzylic cation during
the reaction. The corresponding diol was also isolated in
5–8% yield by refluxing in acetonitrile with CeCl3·7H2O.
The ring opening reaction of cyclic epoxides such as
cyclopentene oxide, cyclohexene oxide and cyclooctene
oxide was completely anti-stereoselective in both cases
giving only the trans isomers.
R.S.B. and M.R. thank CSIR and Ch.S.R. thanks UGC,
New Delhi for the award of fellowships.
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In conclusion, we have demonstrated a highly efficient
and regioselective conversion of epoxides and aziridines
to the corresponding b-halohydrins and b-haloamines
under neutral conditions19 using water tolerant
CeCl3·7H2O and the CeCl3·7H2O/NaI system. Our
methodology presents several advantages like the stabil-
ity and availability of the catalyst, its ease of handling,
shorter reaction times and excellent yields of the prod-
ucts. Further, the method is equally applicable to both
epoxides and aziridines, hence we believe that this
protocol makes a valuable addition to organic synthesis.