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observations, this is important circumstantial evidence that no
rapid reduction by a second equivalent of TiIII reagent takes
place, and that in the case of b-phosphinoyl radicals, radical
elimination is observed. If this were not the case, we would
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In conclusion, we were able to observe for the first time a
titanium-mediated intramolecular vinylation based upon the
previously unknown elimination of b-phosphinoyl radicals.[34]
Work to examine the full scope and limitations of this method,
as well as the development of an asymmetric version, is
currently underway.
Received: March 23, 2004
Revised: May 25, 2004 [Z460099]
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[34] Note that phosphinoyl derivatives have one additional advan-
tage: when subjected to the titanium-mediated sequence, sulf-
oxides lead to both low yields and reduction to the correspond-
ing sulfides. We did not study this further, but to some extent this
precludes part of the asymmetric version, since initial reduction
would eliminate any stereochemical information present on the
sulfur atom.
Keywords: cyclization · domino reactions · phosphorus ·
radical reactions · titanium
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