Amijs et al.
SCHEME 1
propargylic carboxylates with alkenes. Interestingly, a gold
carbene has been recently formed in the gas phase that undergoes
cyclopropanation and cross-metathesis reactions.29
Additions of nucleophiles to 1,6-enynes catalyzed by gold8,9,30
or other electrophilic metal complexes31-34 have been restricted
until recently to water or alcohols. 1,5-Enynes react similarly
with ROH nucleophiles in the presence of Au(I).35-39 The
intramolecular amination of 1,5-enynes with tosylamides35 and
the intermolecular addition of carbamates RO2CNH2 or anilines
ArNH2 to 1,6-enynes have also been reported.40
Addition of electron-rich arenes and heteroarenes to enynes
has been recently reported by the group of Geneˆt41 and by our
group42 using different gold(I) catalysts.43 This addition affords
adducts of type 5 by attack of the carbon nucleophile to
intermediates of type 3 (Scheme 1) in a reaction that is
mechanistically similar to the intramolecular reaction of arylenynes
that results in a formal [4 + 2] cycloaddition reaction.44
However, using indoles as carbon nucleophiles,45 we found that
the attack can also take place at the carbene carbon of
intermediates 3.42 Attack at the carbene carbon of intermediates
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propanation of the alkene by the alkyne. Addition of hetero-
nucleophiles at the terminal alkene carbon by cleavage of the
bond labeled a in intermediate 4 has been observed using PtCl2
or AuCl3 as catalysts, which leads to adducts of type 8.19
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give rise to cyloheptadienes 9.20
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discussed, stressing their carbocationic character.21 It is impor-
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are depicted in a simplified manner as cyclopropyl gold
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