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ChemComm
DOI: 10.1039/C3CC45879B
Madrid, Spain. Fax: +34 914973966; Tel: +34 914974358; E-mail:
45 diego.cardenas@uam.es
† Electronic Supplementary Information (ESI) available: experimental
procedures, data and compuational details. See DOI: 10.1039/b000000x/
are obtained as mixtures of compounds, presumably
diastereomers, which could not be separated. This unusual
regioselectivity has been recently reported, and may be
consequence of the presence of the Lewis acid.19 Oneꢀpot
reaction from 1a afforded just 35 % of 7a.20
5
1
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50
55
60
65
70
2
3
4
5
6
7
Figure 6
Finally, we employed the allylboronate 2a as nucleophilic
coupling partner in a Suzuki crossꢀcoupling reaction with pꢀ
10 cyanoiodobenzene, under the conditions stated below (Figure 7).
Reaction was not comp letely regioselective, affording a mixture
of linear and branched products. Unexpectedly, the more
hindered branched derivative 8 exerting from crossꢀcoupling of
the internal allyl carbon, was the major compound.21
8
9
V. PardoꢀRodríguez, J. MarcoꢀMartínez, E. Buñuel, D. J. Cárdenas,
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15
14 B. MartínꢀMatute, E. Buñuel, M. Méndez, C. NietoꢀOberhuber, D. J.
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Figure 7
Formation of both regioisomers can be explained by two
divergent reductive eliminations involving either terminal allyl
carbons in a putative allyl(aryl)Pd(II). Alternatively, insertion of
20 the CꢀC double bond of the allylboronate into an arylꢀPd bond,
followed by deborylation of the resulting akylꢀPd intermediate is
also feasible. This has been recently proposed for the Suzuki
reaction of 3,3ꢀdisubstituted allylboronates.22 According to the
regioselectivity observed in the formation of allylboronates from
25 allenynes in our previous work,8 as well as the regioselectivity
observed in Table 1, formation of a πꢀallyl complexes by
transmetalation is less likely, since a linear derivative 9, would
have been the preferred isomer. Therefore, insertion of the CꢀC
double bond of the allylboronate into an initially formed arylꢀPd
30 complex, and subsequent deborylation seem to take place in this
case. In conclusion, we have developed a general borylative
cyclisation of dienynes containing an allylboronate. The reaction
is general, tolerates substitution in both the diene and alkyne
fragments, and takes place under smooth conditions giving rise to
35 carboꢀ or heterocycles containing an allylboronate. These
products constitute useful synthetic intermediates and can be
further functionalised.
85
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100
105
110
We thank the MICINN (CTQ2010ꢀ15927) and the CAM
(AVANCAT PPQꢀ1634 and a fellowship to V. P.ꢀR.), and the
40 UAM for a FPI fellowship to R. L.ꢀD.
21 Compounds 8 and 9 could not be isolated from each other by column
chromatography. Nevertheless they could be separated by GCꢀMS.
This analysis revealed that 8 is a mixture of diastereoisomers in
roughly 1:1 ratio.
Notes and references
22 Y. Yang, S. L. Buchwald, J. Am. Chem. Soc. , 2013, 135, 10642. See
also: S. Sebelius, V. J. Olsson, O. A. Wallner, K. J. Szabó, J. Am.
Chem. Soc., 2006, 128, 8150.
a Departamento de Química Orgánica, Facultad de Ciencias,
Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049-
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