The Journal of Organic Chemistry
ARTICLE
was allowed to warm to room temperature. The solution changed from
dark brown-orange to clear or pale yellow. The reaction mixture was
neutralized with 10% HCl (2 mL); water (40 mL) was added. The
solution was extracted with 3 ꢁ 10 mL of Et2O, and the combined
organic layers were washed with 2 ꢁ 10 mL of sat. aq. NaHCO3. The
solvent was removed under vacuum to give a white powder. The samples
were purified with a silica plug with hexanes, and solvent was removed
under vacuum. Solutions of the quench products in Et2O (1%) were
analyzed via GC/mass spectrometry (see Supporting Information for
details and mass spectral data).
Computational Methods. Geometries were optimized at B3LYP/
6-31G(d) density functional theory levels with the Gaussian 03 program
package.45 The chemical shifts were calculated at B3LYP/6-311þG(d,p)
using the GIAO method on the geometries optimized with lithium
counterions with the Gaussian 09 program.46 The best agreement
between experimental and calculated shifts was found when the effect
of solvent was included in the calculation through the polarization
continuum method, PCM, with the ε value of 7.4257, the default value
for THF in Gaussian 03. The nucleus-independent chemical shifts
(NICS(1)zz)4,17 were obtained from the chemical shift tensor perpendicular
to the ring for a ghost atom placed 1 Å above the center of each ring on
geometries optimized without counterions. Magnetic susceptibility
exaltation was determined from the magnetic susceptibility calculated
for the substituted 12ꢀ using the CSGT method with basis set B3LYP/
6-311þG(d,p) by subtraction of the magnetic susceptibility for the localized
system. Areas were calculated from the Cartesian coordinates for each
ring system oriented in the xy plane. See Supporting Information for
specific details of the calculation. TD-DFT calculations were done with
the B3LYP/6-311þG(d,p) on the geometries optimized at the B3LYP/
6-31G(d) level. See the Supporting Information for the discussion of the
validity of geometry optimization with B3LYP/6-31G(d) vs that with
functionals with long-range correction, such as LC-BLYP/6-31þG(d).
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’ ASSOCIATED CONTENT
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S
Supporting Information. Details on the calculation of
b
magnetic susceptibility, ring areas, and Cartesean coordinates,
frequencies, and energies of the optimized geometries of
1a2ꢀꢀ1f2ꢀ, Li2[1bꢀf], with and without explicit THF, and
Li41b and Li4[1dꢀf], and Li41d, with and without explicit THF,
at varying levels of theory; 1H NMR spectra of reduction of 1b,
1d (full spectrum), 1e, and 1f; 13C NMR, COSY, and HMQC
spectra of the reduction mixture of 1d; calculated chemical shifts
of dianions of Li41b and Li41dꢀf; mass spectra of the tetra-
silylated product and tetradeuterated product; diagram of the
insert used for reduction of 1. This material is available free of
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’ AUTHOR INFORMATION
(34) Mills, N. S.; Levy, A.; Plummer, B. F. J. Org. Chem. 2004, 69,
6623–6633.
(35) Roesch, N.; Trickey, S. B. J. Chem. Phys. 1997, 106, 8940–8941.
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Corresponding Author
’ ACKNOWLEDGMENT
We thank the Welch Foundation (Grant W-794), the National
Science Foundation (Grants CHE-0126417, CHE-0553589,
CHE-0957839, and CHE-0948445), and the Dr. John A. Burke, Jr.
research fund for their support of this research and Dr. Cheryl
Stevenson for helpful discussions.
(41) Mills, N. S. J. Org. Chem. 2002, 67, 7029–7036.
(42) Black, M.; Woodford, C.; Mills, N. S. J. Org. Chem. 2011,
76, 2286–2290.
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