Electr otellu r a tion : A New Ap p r oa ch to Tr i- a n d
Tetr a su bstitu ted Alk en es
J oseph P. Marino* and Hanh Nho Nguyen
Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109
jpmarino@umich.edu
Received October 22, 2001
A novel electrotelluration process is described in which a Michael addition of an alkyl or aryl
tellurolate anion occurs onto an activated alkyne with subsequent trapping of a vinyl anion with
electrophiles (aldehydes and ketones) other than a proton. This process provides an efficient regio-
and stereospecific route to tri- and tetrasubstituted alkenes. Methodologically significant examples
of this chemistry were studied in which aryl and alkyl tellurolate anions were added to ω-keto
alkynyl esters in a Michael reaction, and the incipient vinyl anions were trapped intramolecularly
by the internal aldehydes. The reactive centers were tethered by different lengths of alkyl chains
to form highly functionalized five-, six-, seven-, and eight-membered rings in modest to good yields.
SCHEME 1. Th e Electr otellu r a tion Rea ction
In tr od u ction
Hydrometalation reactions of alkynes such as hy-
droalumination,1 hydroboration,2 and hydrozirconation3
provide direct routes to E-alkenylorganometallics which
can be further utilized to make carbon-carbon bonds via
transmetalation/cross-coupling4 reactions. In contrast to
the above hydrometalation reactions, hydrotelluration
reactions lead to exclusively a Z-alkene,5-8 thus providing
a unique route to organometallics with opposite stereo-
chemistry.
can also undergo cross-coupling reactions directly with
terminal alkynes,12 alkylzinc,13 alkynylzinc,14 and Grig-
nard reagents7 or react with carbon monoxide15 catalyzed
by a transition metal. These stereodefined tri- or tetra-
substituted alkenes bearing vinylic tellurides can be
important precursors for the synthesis of natural prod-
ucts containing alkenes and polyenes.16 Several success-
ful trapping experiments using tellurolate anions are
reported herein.
In hydrotelluration reactions,5-8 we anticipated that
a vinyl anion intermediate was formed and sequentially
trapped by a proton. In an effort to expand the scope of
the hydrotelluration reactions to include other electro-
philes, we set out to trap the “vinyl anion intermediate”
with electrophiles such as aldehydes, ketones, and tri-
alkylsilyl chlorides (Scheme 1). The expected product
would be a tri- or tetrasubstituted alkene (depending on
whether one starts with a mono- or disubstituted alkyne)
bearing a vinylic telluride that could be further trans-
metalated to lithium,9 copper,10 or zinc11 to perform other
carbon-carbon bond forming reactions. Vinylic tellurides
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10.1021/jo0110146 CCC: $22.00 © 2002 American Chemical Society
Published on Web 02/23/2002
J . Org. Chem. 2002, 67, 6291-6296
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