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stirred for 18 h at room temperature. Upon concentration under
reduced pressure, the crude product was poured into water and
extracted twice with Et2O (100 mL each). The combined organic
layers were washed three times with a solution of ceric ammonium
nitrate (100 mL each), dried over Na2SO4, and evaporated in vacuum.
Flash column chromatography (gradient, 9:1 to 85:15 hexane/AcOEt)
afforded 192 mg (0.23 mmol, 42% yield) of diester 6 as a white
crystalline material: mp 215−217 °C (hexane/AcOEt); Rf = 0.49
(hexane/AcOEt 7:3); IR (cm−1, CHCl3) ν 3597, 2937, 2858, 1722,
ASSOCIATED CONTENT
* Supporting Information
■
S
Spectroscopic data for compounds 3−7, X-ray powder
diffraction patterns, 13C CPMAS and 13C CPMAS non-
quaternary suppression spectra of compounds 7E and 7Z,
thermogravimetric traces of 7E and 7Z, crystallographic
parameters and crystallographic information files (cif) for
compounds 7E and 7Z, alternative line shape comparisons
using the ACBD array, Eyring plot of ln(krot/T) over 1000/T
with activation enthalpy and entropy. This material is available
1
1184, 1160, 988; H NMR (ppm, CDCl3) δ 7.40 (s, 4H), 6.00−5.90
(m, 2H), 5.20−5.16 (m, 2H), 5.15−5.13 (m, 2H), 5.05 (m, 2H), 3.09
(dt, J = 6.9, 1.4 Hz, 4H), 2.40−2.33 (m, 2H), 2.09−2.02 (m, 4H), 0.90
(s, 6H), 0.83 (s, 6H); 13C NMR (ppm, CDCl3) δ 171.0 (2 × C), 131.5
(4 × CH), 130.6 (2 × CH), 122.9 (2 × C), 118.2 (2 × CH2), 94.8 (2
× C), 85.4 (2 × C), 80.4 (2 × C), 70.3 (2 × CH), 53.9 (2 × CH), 50.8
(2 × CH), 47.4 (2 × C), 40.0 (2 × CH), 39.6 (2 × CH2), 39.1 (2 ×
CH2), 36.2 (2 × CH), 35.9 (2 × C), 33.0 (2 × CH2), 32.9 (2 × CH2),
32.8 (2 × CH2), 31.4 (2 × CH2), 28.2 (2 × CH2), 26.1 (2 × CH2),
23.2 (2 × CH2), 20.5 (2 × CH2), 13.0 (2 × CH3), 11.3 (2 × CH3);
HRMS (ESI) calcd for m/z C56H74O6Na+ requires m/z 865.5383,
found 865.5347.
AUTHOR INFORMATION
Corresponding Author
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
Financial support from the Polish National Science Centre
(DEC-2011/02/A/ST5/00459) and CONACyT Mex
gratefully acknowledged. Work at UCLA was supported by
National Science Foundation Grant Nos. DMR1101934 and
CHE0-844455.
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Ring-Closing Metathesis: Synthesis of Rotors 7E and 7Z. A
solution of diester 6 (30 mg, 0.04 mmol) in dry toluene (200 mL) was
placed under argon atmosphere in a flame-dried 500 mL round-
bottomed flask, and then the reaction was heated to 80 °C. After 5
min, Grubbs second-generation catalyst (5 mg, 0.06 mmol, 15 mol %)
was added. The reaction mixture was stirred for 3 h at 80 °C, cooled to
room temperature, and quenched with ethylvinyl ether (1 mL). The
solvents were removed under reduced pressure, and the residue was
extracted three times with AcOEt (100 mL each). The combined
organic layers were dried over Na2SO4 and evaporated in vacuo. The
separation of rotors (7a and 7b) from the catalyst and/or its
decomposition products was performed by flash column chromatog-
raphy (gradient, 85:15 to 8:2 hexane/AcOEt, on 230−400 mesh silica
gel). The mixture of isomeric rotors 7a and 7b was obtained (19 mg,
́
ico is
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1
0.023 mmol, 67% yield; E/Z ratio −1:1, determined by H NMR).
The separation of the rotors was achieved by HPLC.
Molecular Rotor 7E. White crystalline material: dec above 305 °C
(CH2Cl2); Rf = 0.41 (hexane/AcOEt 7:3); HPLC tR (9:1 CH3CN/
CH2Cl2) 10.91 min; IR (cm−1, CHCl3) ν 3595, 2933, 2858, 1721,
1265; IR (cm−1, ATR) ν 3538, 2922, 2858, 1737, 1267, 1153, 987,
1
850; H NMR (ppm, CDCl3) δ 7.43 (s, 4H), 5.73 (m, 2H), 5.04 (m,
2H), 3.18−3.07 (m, 4H), 2.40−2.33 (m, 2H), 2.09−1.97 (m, 4H),
0.90 (s, 6H), 0.81 (s, 6H), 0.72−0.63 (m, 2H); 13C NMR (ppm,
CDCl3) δ 171.1 (2 × C), 131.5 (4 × CH), 126.0 (2 × CH), 122.9 (2
× C), 94.9 (2 × C), 85.1 (2 × C), 80.2 (2 × C), 70.5 (2 × CH), 54.1
(2 × CH), 50.8 (2 × CH), 47.7 (2 × C), 40.2 (2 × CH), 39.0 (2 ×
CH2), 38.8 (2 × CH2), 36.2 (2 × CH), 35.8 (2 × C), 33.0 (2 × CH2),
32.9 (2 × CH2), 32.8 (2 × CH2), 31.5 (2 × CH2), 28.2 (2 × CH2),
26.0 (2 × CH2), 23.2 (2 × CH2), 20.5 (2 × CH2), 12.9 (2 × CH3),
11.4 (2 × CH3); HRMS (ESI) calcd for m/z C54H70O6Na+ requires
837.5070, found 837.5058.
Molecular Rotor 7Z. White crystalline material: mp 299−300 °C
(CH2Cl2/hexane); Rf = 0.41 (hexane/AcOEt 7:3); HPLC tR (9:1
CH3CN/CH2Cl2) 12.06 min; IR (cm−1, CHCl3) ν 3596, 2931, 2857,
1725, 1265, 1159; IR (cm−1, ATR) ν 3426, 2934, 2857, 1737, 1712,
1
1263, 1178, 1159, 1043, 834, 742; H NMR (ppm, CDCl3) δ 7.41 (s,
4H), 5.87 (m, 2H), 5.07 (m, 2H), 3.16−3.06 (m, 4H), 2.40−2.32 (m,
2H), 2.09−1.95 (m, 4H), 0.90 (s, 6H), 0.82 (s, 6H), 0.74−0.65 (m,
2H); 13C NMR (ppm, CDCl3) δ 171.0 (2 × C), 131.4 (4 × CH),
124.0 (2 × CH), 122.9 (2 × C), 94.7 (2 × C), 85.1 (2 × C), 80.2 (2 ×
C), 70.4 (2 × CH), 54.2 (2 × CH), 50.9 (2 × CH), 47.6 (2 × C), 40.2
(2 × CH), 38.8 (2 × CH2), 36.1 (2 × CH), 35.9 (2 × C), 33.3 (2 ×
CH2), 33.0 (2 × CH2), 33.0 (2 × CH2), 32.8 (2 × CH2), 31.6 (2 ×
CH2), 28.2 (2 × CH2), 26.1 (2 × CH2), 23.2 (2 × CH2), 20.5 (2 ×
CH2), 12.9 (2 × CH3), 11.4 (2 × CH3); HRMS (ESI) calcd for m/z
C54H70O6Na+ requires 837.5070, found 837.5048.
(6) Dominguez, Z.; Khuong, T.-A. V.; Sanrame, C. N.; Dang, H.;
Nunez, J. E.; Garcia-Garibay, M. A. J. Am. Chem. Soc. 2003, 125, 8827.
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10793. (b) Khuong, T.-A. V.; Nunez, J. E.; Godinez, C. E.; Garcia-
̃
̃
Garibay, M. A. Acc. Chem. Res. 2006, 39, 413.
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dx.doi.org/10.1021/jo3020402 | J. Org. Chem. 2012, 77, 9970−9978