4
method is the capability to tritylate secondary alcohols under
mild conditions in a short time without using expensive silver
salts. Several other advantages are also significant. The reagent
used in the method is trityl alcohol, which is more stable and
potentially less expensive than the more commonly used trityl
chloride. We expect that the method find wide applications for
the protection of alcohols in organic synthesis. More importantly,
the method provides a potential solution for the formation of
trityl ether linkages between complex and sensitive substrates
where known methods do not work.
Acknowledgments
Financial support from NIH (R15GM109288), NSF
(CHE1111192 and CH0647129) and MTU SURF (T.W.); the
assistance from Mr. D.W. Seppala (electronics) and Mr. J.L. Lutz
(NMR); NSF equipment grants (CHE-1048655 and CHE-
9512455); and MSU Mass Facility (HRMS) are gratefully
acknowledged.
formed almost exclusively. The rationale is that the polar
solvents coordinate with the cation 12a and reduce its reactivity,
and therefore increase selectivity. The overall higher yield with
THF as a solvent over others (entries 1-4) is likely a result of
combined effects of substrate solubility in the solvents and the
degree to which the solvents coordinate to the cation. As to the
effect of different bases on the yields (entries 2 and 5-7, Table 1),
the more coordinating base pyridine gave much lower yield. The
non-coordinating ones including 2,6-lutidine, DIEA and DBU
gave much higher yields. The lower yield with pyridine is a result
of the lower reactivity of the cation 12a caused by coordination
to the base.
Supplementary Material
Supplementary data associated with this article can be found,
in the online version, at
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There are several reasons for trifluoroacetic anhydride to stand
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Conclusion
In summary, we have developed a new method for the
tritylation of alcohols. Both primary and secondary alcohols were
found to be good substrates for the reaction. Compared to known
tritylation methods, the most significant advantage of the new