Efficient BiIII Triflate-Catalysed Intramolecular Hydroarylation
2 h in an anhydrous solvent [(CH2)2Cl2 or CH3NO2, 5 mL] under
an inert atmosphere. The reaction was quenched with ice water and
extracted with Et2O (3ϫ10 mL) and brine (3ϫ10 mL). The or-
ganic layer was concentrated under reduced pressure, and the prod-
uct was purified by flash chromatography (Pentane/Et2O 95:5).
examples of stoichiometric Lewis acid mediated reac-
tions.[5g] A single diastereomer was formed in the case of
2h, and a 1:1 mixture of isomers was obtained with 2i as a
result of the different benzyl substituents. The structures of
2h and 2i were elucidated on the basis of spectroscopic data
(NMR 2D, COSY, HMBC, HMQC, NOESY experiments).
Terminal meta-allyl olefins such as 1j also afforded
cyclisation leading to the fused six-membered ring 2j with
a moderate yield of 41% (entry 17). In the cyclisation of 1j,
a competitive process involved the formation of lactone 3j
in 52% yield (Scheme 2). This lactone is issued from the
Lewis acid catalysed reaction between the olefin and one of
the ester groups. The formation of such lactones has already
been observed in related examples.[17]
Supporting Information (see footnote on the first page of this arti-
cle): Experimental details; spectroscopic characterisation data (1H
and 13C NMR, MS, HRMS) for compounds 2a–2j, 2m, 2n and 3j.
Acknowledgments
Support of this work with a grant to B. C. by the French Ministry
of Research is gratefully acknowledged.
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constitutes a 100% atom-economic process and has large
applicability. Highly substituted nonconjugated olefins can
be used, without requiring electron-rich aromatic rings, as
it is generally the case in related processes. The reaction
could be carried out in the presence of 1–5 mol-% of the
catalyst and allowed the preparation of a large series of
tetralin structures obtained in good to excellent yields.
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Experimental Section
General Procedure: A mixture of aromatic compound 1a–1n
(1 mmol) and Bi(OTf)3 (0.05 to 0.1 mmol) was heated to reflux for
Eur. J. Org. Chem. 2011, 3710–3714
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