Communications
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[11] As a result of alkene migration, formation of two isomers was yet
another issue. Nevertheless, identical enantiomeric excesses
were measured for both isomers.
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693, and references therein.
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chemistry, THF and toluene worked equally well; however, the
enantioselectivity was slightly better in toluene. b) Interestingly,
catalyst loadings as low as 1.0 mol% Pd(OAc)2 precatalyst and
1.5 mol% L1 did not affect the enantioselectivity of the reaction.
[14] The absolute configuration of 14 has not been determined yet
since all attempts to derivatize and crystallize or chemically
correlate 14 have failed so far.
[15] C. Laue, G. Schrꢁder, D. Arlt (Bayer AG), DE-A1 19522293,
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reported: a) G. Trabesinger, A. Albinati, N. Feiken, R. W.
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Scheme 4. Catalyst-directinghydroxy group.
[18] Cyclization precursor 17 was prepared by a twofold palla-
dium(0)-catalyzed, Et3B-promoted C-allylation of 2-hydroxya-
cetophenone with cinnamic alcohol followed by deoxygenation:
Y. Horino, M. Naito, M. Kimura, S. Tanaka, Y. Tamaru,
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cosolvent in an asymmetric Heck reaction in order to suppress
oxidation of a secondary-alcohol-containing substrate without
affecting the level of enantioselectivity: K. Kondo, M. Sodeoka,
M. Mori, M. Shibasaki, Synthesis 1993, 920 – 930. For a general
overview on alcohols as cosolvents, see ref. [3b].
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A. H. Hoveyda, D. A. Evans, G. C. Fu, Chem. Rev. 1993, 93,
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alkene insertion into an arylpalladium alkoxide intermediate:
J. P. Wolfe, M. A. Rossi, J. Am. Chem. Soc. 2004, 126, 1620 –
1621.
Received: June 9, 2004
Keywords: asymmetric catalysis · asymmetric synthesis ·
.
ꢁ
C C coupling· palladium
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membered ring, which could potentially account for the
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