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Scheme 2 Proposed mechanism for the cascade reaction.
for the treatment of tumors of the blood. The reaction of vinyl
sulfonium 4 with substituted (1H-indole-2-yl)methanol 9 under
our standard conditions generated 10 in 77% yield (eqn (3)).
Compared with a conventional three-step synthesis of 10 (49%
yield),3b the current one-step procedure represents a significant
improvement in terms of the criteria of green chemistry.
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ð3Þ
In summary, we have developed an addition-cyclization
reaction of (1H-indole-2-yl)methanols and vinyl sulfonium
salts, providing biologically and pharmaceutically important
oxazino[4,3-a]indoles in good to excellent yields. This methodology
can also be used in the preparation of pyrazino[1,2-a] indole
derivatives.
We are grateful to the National Science Foundation of
China (20872043) for support of this research.
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