Carbon-to-Carbon Anion Relay Chemistry
tively. Nevertheless, these barriers are low from the perspec-
tive of reaction rate and rearrangement is expected to be
rapid, even at –78 °C.
Acknowledgments
This work was supported by a grant from the National Science
Foundation to whom we are grateful. Thanks to Advanced Asym-
metrics, Inc. for a gift of the chiral sulfinamide precursor to 41.
The computational studies along with our experimental
work strongly support the idea that pentaorganosilicates
need not be invoked as intermediates in this reaction. Full
silicon transfer and a real allylic organolithium best de-
scribe what becomes of 19 after halogen/metal exchange.
Although this picture may be subject to modification as we
explore other systems, it appears that for 19 the structure
most resembling a pentaorganosilicate is a transition state
and not an intermediate.
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Conclusions
We have discovered a convenient and novel way to syn-
thesize 2-aryl-substituted allyllithium species by a carbon-
to-carbon silicon 1,4-shift.[21] The efficiency of this process
is surprising given that benzene and propene have been esti-
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cess was observed, but no attempt has yet been made to drive
the reaction.
Experimental Section
A flame-dried 25 mL round-bottomed flask was charged with bro-
moalkene 19 (400 mg, 1.48 mmol), 4-tert-butylanisole (260 μL,
1.48 mmol, internal standard), and THF (7.5 mL). The solution
was cooled to –78 °C before tBuLi (1.06 m, 2.9 mL) was added
dropwise. After this, the clear orange solution was stirred for
15 min at –78 °C and the reaction was quenched by the slow ad-
dition of nBuBr (190 μL, 1.77 mmol). The reaction was monitored
by GC–MS. After being stirred for 30 min, it was diluted with di-
ethyl ether, washed with water, and dried with MgSO4. The solvent
was concentrated in vacuo to provide 342 mg of the crude product.
NMR analysis of the crude showed the ratio of the product 23 and
tert-butylanisole was 1:1. The NMR yield was calculated to be 94%
based on the NMR ratio of the product and internal standard and
corrected based on recovered mass. Analytical samples were ob-
tained by careful column chromatography (SiO2, hexanes). For 23:
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hypervalent silicon species as assessed by 29Si NMR analysis.
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M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B.
Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li,
H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Son-
nenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hase-
gawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai,
T. Vreven, J. A. Montgomery Jr., J. E. Peralta, F. Ogliaro, M.
Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Starov-
erov, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell,
IR: ν = 2953, 2925, 1462, 1246, 1115, 898, 837, 727 cm–1. 1H NMR
˜
(500 MHz, CDCl3): δ = 7.58, (dd, J = 7.1, 1.4 Hz, 1 H); 7.26–7.35
(m, 2 H), 7.14 (dd, J = 7.5, 1.0 Hz), 5.16 (q, J = 1.7 Hz, 1 H), 4.93
(m, 1 H), 2.34 (t, J = 7.9 Hz, 2 H), 1.55–1.58 (m, 2 H), 1.36–1.40
(m, 4 H), 0.93–0.96 (m, 3 H), 0.31 (s, 9 H) ppm. 13C NMR
(125 MHz, CDCl3): δ = 152.1, 150.8, 137.1, 134.8, 128.3, 127.9,
125.8, 113.3, 38.7, 31.7, 27.0, 22.5, 14.0. 0.9 ppm.
Supporting Information (see footnote on the first page of this arti-
cle): Experimental procedures and characterization data for new
compounds.
Eur. J. Org. Chem. 2011, 5255–5260
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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