M. Catellani et al.
dary products increase when the steric hindrance of an alkyl
group R decreases. The electronic effect shown by an ortho
CO2Me group also turns out to be positive. Thus the nature
of the effect caused by R groups deserves further study.
The secondary products derive from competing reactions
and show a different distribution depending on the ortho
substituent. Those found with o-substituted iodobenzene
and furan are reported in Scheme 4. Analogous products are
been developed taking advantage of the unique opportuni-
ties offered by the palladium/norbornene system. Further in-
vestigations are in progress to expand the scope of the reac-
tion.
Experimental Section
The general procedure is illustrated for the case of 2-isopropyliodoben-
zene and furan: 2-Isopropyliodobenzene (0.35 g, 1.43 mmol), furan
(0.49 g, 7.2 mmol), norbornene (34 mg, 0.36 mmol), PdACTHUNRGTNEUNG(OAc)2 (4 mg,
0.018 mmol), and K2CO3 (0.22 g, 1.61 mmol) in DMF (16 mL) were
stirred with a magnetic bar in a closed Schlenk-type flask under nitrogen
at 1058C for 48 h. At the end of the reaction the mixture was allowed to
cool to room temperature, diluted with EtOAc (30 mL), washed three
times with brine (3ꢂ30 mL), and dried over Na2SO4. The solvent was re-
moved under reduced pressure and the crude mixture was analyzed by
1
GC and H NMR spectroscopy. The product was isolated by flash column
chromatography on silica gel using a 95:5 mixture of hexane–EtOAc as
eluent to obtain compound 1a as a white powder in 65% yield (0.141 g).
Acknowledgements
Financial support from MIUR and University of Parma is gratefully ac-
knowledged. NMR facilities were provided by the Centro Interdiparti-
mentale dell’Universitꢀ di Parma.
Scheme 4. Secondary products found in the reaction of o-substituted io-
dobenzene and furan.
À
À
Keywords: catalysis
activation · heterocyclic compounds · palladium
· C C coupling reaction · C H
present with the other heterocycles. Apart from product 3,
which results from the direct attack of the starting aryl
iodide on the heterocycle and 6, which results from hydroge-
nolytic aryl coupling, they incorporate norbornene in differ-
ent ways as we already reported.[8] For example with R=
iPr, products 3–7 are all formed in 3–5% each. In addition
an ortho methyl group readily forms condensed cyclopen-
tane structures 8 (12%) and 9 (3%) by cyclization with nor-
bornene,[9] and also 3 (R=Me) is present in a significant
amount (12%), while the yield of 1 is 53%.
Notably the reaction can be extended to the more com-
plex case of an ortho-substituted aryl iodide, an aryl bromi-
de,[3c] instead of two molecules of aryl iodide,[3d] and a het-
erocycle. Yields and selectivities are lower, however, and
further study is required to find out the best conditions.
Thus, the following reaction gives the product in 49% yield
(Scheme 5).
[1] L. Ackerman, Modern Arylation Methods, Wiley-VCH, Weinheim,
2009.
[2] a) B. Liꢃgault, D. Lapointe, L. Caron, A. Vlassova, K. Fagnou, J. Org.
Chem. 2009, 74, 1826–1834; b) M. Lafrance, D. Lapointe, K. Fagnou,
T. Satoh, Top. Organomet. Chem. 2005, 14, 55–83; m) G. Dyker,
Handbook of C-H Transformations, Wiley, Weinheim, 2005; n) J.
Tsuji, Palladium Reagents and Catalysts, Wiley, New York, 2004;
o) M. Beller, C. Bolm, Transition Metals for Organic Synthesis: Build-
ing Blocks and Fine Chemicals, 2nd ed., Wiley-VCH, Weinheim,
2004; p) J. Hassan, M. Sevignon, C. Gozzi, E. Schultz, M. Lemaire,
In summary, a simple one-step catalytic process for the
synthesis of heteroatom-containing o-teraryl derivatives
from readily accessible aryl iodides and heterocycles has
1512–1522; b) M. Catellani, Top. Organomet. Chem. 2005, 14, 21–53;
79; d) E. Motti, G. Ippomei, S. Deledda, M. Catellani, Synthesis 2003,
2671–2678; e) E. Motti, F. Faccini, I. Ferrari, M. Catellani, R. Ferrac-
650; b) C.-S. Li, C.-H. Cheng, F.-L. Liao, S.-L. Wang, Chem.
Commun. 1991, 710–712; c) M. Portnoy, Y. Ben-David, I. Rousso, D.
Scheme 5. One-pot reaction of an o-substituted aryl iodide and an aryl
bromide with a heterocycle.
7852
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Chem. Eur. J. 2009, 15, 7850 – 7853