1770
D. Ma et al.
CLUSTER
that the coupling of 1-iodocyclohexene with three select-
ed o-iodophenols delivered the corresponding coupled
products, which were subjected to Heck reaction14 to pro-
duce tricyclic benzofurans (Table 2, entries 1–3). Addi-
tion of n-Bu4NHSO4 in the Heck reaction was important,
a low yield was observed in the absence of this reagent
(Table 2, entry 1).15 Further exploration demonstrated 3-
iodo-2-hexen-1-one was compatible with the above pro-
cess to give the corresponding tricyclic benzofurans
(Table 2, entries 4–6). In this case Et3N was used as the
base in the Heck reaction step because no product was ob-
tained when NaHCO3 was used. However, poor conver-
sion was encountered when two acyclic vinyl iodides
were employed mainly due to steric hindrance (Table 2,
entries 7 and 8). It is notable that a moderate yield was ob-
tained from the coupling of (Z)-3-iodo-2-octenoic ethyl
ester with 2-iodophenol to a 2,3-disubstrated benzofuran
(Table 2, entry 7).
Acknowledgment
The authors are grateful to the Chinese Academy of Sciences,
National Natural Science Foundation of China (grant 20132030),
and the Science and Technology Commission of Shanghai Munici-
pality (grant 02JC14032) for their financial support.
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Cross-coupling: A mixture of vinyl halide (1.0 mmol), phenol (1.5
mmol), Cs2CO3 (2.1 mmol), CuI (0.1 mmol), N,N-dimethylglycine
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Synlett 2005, No. 11, 1767–1770 © Thieme Stuttgart · New York