Angewandte
Chemie
then dried over anhydrous magnesium sulfate. Filtration through a
pad of celite and evaporation of the solvent followed by column
chromatography on silica gel gave the corresponding coupling
products as a mixture of isomers. Further isolation was performed
with preparative recycling column chromatography on silica gel.
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[4] All new compounds were characterized by 1H and 13C NMR
spectroscopy and HRMS. For details, see supporting informa-
tion.
[5] By-products based on 1a were detected by GC–MS analysis as 1-
methylisatin (1-methylindole-2,3-dione), a dimer of 1a, and a
trimer of 1a that bears a carbonyl function.
Received: April 23, 2004 [Z460429]
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À
Keywords: C C coupling · heteroarenes · lactams · Lewis acids ·
zirconium
.
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[3] Late transition metals such as Pd, Ru, and Rh are known to
catalyze the dehydrogenative coupling reaction between two
2
À
[11] Electrophilic substitution of indoles is well known to take place
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