Organic Letters
Letter
Table 2. Use of 2-Oxo-2-arylacetate and N-Methylisatin
Substrates
This work presents the first catalytic cyclization reactions
between the Huisgen zwitterion and carbonyl substrates by in
situ recycling of the phosphine oxide. This proves the feasibility
of such a process, and these results will allow us to envisage an
extension in other phosphine-promoted reactions. We are
currently investigating the catalytic reaction of the Huisgen
zwitterion with allenes, imines, and olefins, specifically working
to develop asymmetric variants of these reactions.
ASSOCIATED CONTENT
Supporting Information
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Experimental procedures and full spectroscopic data for all new
AUTHOR INFORMATION
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Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We acknowledge the support of the French “Agence Nationale
de la Recherche” (ANR) for funding (grant no. ANR-13-JS07-
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a
Yields of isolated compounds.
0
008) and the Centre National de la Recherche Scientifique
Scheme 3. Proposed Mechanism for the Cyclization
Reaction and the Reduction of Phosphine Oxide
(CNRS).
REFERENCES
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19a
phosphate/amine, and inspired by the work of Beller, the
mechanism could be proposed as follows (Scheme 3). The
phosphate−amine salt C reacts with phenysilane to form a
phosphasilane intermediate. The latter could act as a bifunc-
tional catalyst, which activates both the silane and the
phosphine oxide. After reduction of the phosphine oxide to
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(
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3
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3
2
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mechanism could explain why the use of at least 2 equiv of
silane is necessary.
(
the addition of alkylphosphites to diethyl azocarboxylate: Morrison, D.
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C
Org. Lett. XXXX, XXX, XXX−XXX