Preparation of C3-Symmetric Homochiral syn-Trisnorbornabenzenes
3). The combined extracts were washed with brine, dried over Na2SO4,
filtered through celite, and evaporated. The residue was purified by silica
gel chromatography (10% AcOEt/hexane) to give vinyl iodide 17 (2.07 g,
83% from 14) as a yellowish oil. ½aꢂ2D3 =ꢀ312.08 (c=0.50, CHCl3); IR
(neat): n˜ =2979, 2944, 2880, 1566, 1314, 1180, 1090, 1047, 1022, 976, 810,
Conclusions
As described above, we have succeeded in the development
of regioselective cyclotrimerization for formation of syn-tris-
norbornabenzene derivatives using palladium nanoclusters
and the efficient preparation of novel C3-symmetric homo-
chiral (ꢀ)-syn-trisoxonorbornabenzene 1. The thus-prepared
homochiral (ꢀ)-syn-1 can be a useful intermediate for the
synthesis of C3-symmetric homochiral cup-shaped molecules.
We have demonstrated the utility of the homochiral (ꢀ)-
syn-1 as a platform for C3-symmetric homochiral molecules
with several types of substituents in a helical form through
palladium-catalyzed coupling reactions. Such C3-symmetric
homochiral cup-shaped molecules with a helical arrange-
ment of substituents will serve as homochiral host molecules
or a building block for homochiral caged compounds.
703 cmꢀ1 1H NMR (CD2Cl2): d=6.42 (d, J=3.6 Hz, 1H), 4.00–3.80 (m,
;
4H), 2.87 (s, 1H), 2.58 (m, 1H), 1.85 (m, 1H), 1.79 (dd, J=12.4, 3.6 Hz,
1H), 1.69 (d, J=8.8 Hz, 1H), 1.47 ppm (dd, J=12.4, 3.6 Hz, 1H);
13C NMR (CD2Cl2): d=142.1, 118.5, 101.7, 65.5, 65.0, 53.3, 52.5, 48.8,
39.6 ppm; HRMS (EI): m/z calcd for C9H11IO2 [M+]: 277.9804; found:
277.9808.
18: To a solution of 17 (2.07 g, 7.42 mmol) in acetone (67 mL) was added
1m aq. HCl (7.4 mL). After stirring at 568C for 10 h, the solvent was
evaporated. Aqueous NaHCO3 was added to the residue, and the mixture
was extracted with AcOEt (30 mlꢂ3). The combined extracts were
washed with brine, dried over Na2SO4, filtered through celite, and evapo-
rated. The residue was purified by silica gel chromatography (10%
AcOEt/hexane) to give vinyl iodide 18 (1.44 g, 83%) as a yellowish oil.
The identical data were reported in reference [7b].
25: To a solution of triketone syn-1 (200 mg, 0.628 mmol) and P(O)-
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
Experimental Section
After stirring for 30 min, 2-ClPyNTf2 (863.3 mg, 2.20 mmol) in THF
(2 mL) was added to the reaction mixture at ꢀ808C. After stirring for
30 min, the reaction was quenched with aq. NaHCO3. The mixture was
extracted with EtOAc (20 mlꢂ3). The combined organic extracts were
washed with 1m aq. NaOH, brine, dried over Na2SO4, filtered through
celite, and evaporated. The residue was purified by aluminum oxide
General
Melting points were determined on
a Stanford Research Systems
MPA100 and are uncorrected. Optical rotations were measured on a
JASCO P-1020 polarimeter. IR and UV spectra were recorded on a
JASCO FT IR-4100 spectrometer and a JASCO V-670 spectrometer. 1H
and 13C NMR spectra were measured on JEOL JMN LAMBDA 400
spectrometer at 238C at 400 and 100 MHz, respectively. CDCl3 and
CD2Cl2 were used as a solvent and the residual solvent peaks were used
as an internal standard (1H NMR: CDCl3 7.26 ppm, CD2Cl2 5.32 ppm;
13C NMR: CDCl3 77.0 ppm, CD2Cl2 53.5 ppm). Circular dichroism (CD)
spectra were recorded on a JASCO J-720w spectropolarimeter. High res-
olution mass spectra (HRMS) were measured on a JEOL JMS-777 V
spectrometer using electron ionization (EI) or fast atom bombardment
(FAB) methods. Silica gel or aluminum oxide chromatography was per-
formed on Wako Wakosil C-300 or Merck aluminum oxide 90 standar-
dized using a Yamazen preparative medium pressure liquid chromatogra-
phy system. TLC analysis was performed using Merck Silica gel 60 F254
and aluminum oxide. Preparative TLC (PTLC) was conducted using
Merck aluminum oxide F254, basic. Air- and/or moisture-sensitive reac-
tions were carried out under an argon atmosphere with commercially
available anhydrous solvents. All reagents and solvents were commercial-
ly purchased and further purified according to the standard methods, if
necessary.
short-column chromatography (0–5% EtOAc/hexane) to give triflate 25
23
(336.7 mg, 75%) as a colorless solid. M.p.:56–588C (decomp); ½aꢂD
=
ꢀ5.88 (c=0.40, CHCl3); IR (KBr): n˜ =3435, 2992, 2947, 1620, 1426, 1219,
1140, 1095, 903, 865, 611 cmꢀ1 1H NMR (CDCl3): d=6.23 (d, J=3.6 Hz,
;
3H), 3.96 (m, 3H), 3.91 (m, 3H), 2.64 (ddd, J=7.4, 1.6, 1.6 Hz, 3H),
2.20 ppm (d, J=7.4 Hz, 3H); 13C NMR (CDCl3): d=164.0, 138.6, 136.0,
125.2, 118.3 (q, J=320 Hz), 66.3, 49.2, 46.1 ppm; HRMS (EI): m/z calcd
for C24H15F9O9S3 [M+]: 713.9734; found: 713.9730.
27: To a solution of triflate 25 (40 mg, 0.056 mmol), [PdACTHUNTRGNE(UNG PPh3)4] (19.4 mg,
0.017 mmol), and LiCl (9.5 mg, 0.224 mmol) in THF (3 mL) under Ar at-
mosphere was added 1.08m phenylmagnesium bromide in THF
(233.0 mL, 0.252 mmol) at ambient temperature. The reaction mixture
was stirred at 608C for 3 h. The reaction was quenched at 08C with aq.
NH4Cl and extracted with EtOAc (5 mlꢂ3). The combined organic ex-
tracts were washed with brine, dried over Na2SO4, filtered through celite,
and evaporated. The residue was purified by aluminum oxide short-
column chromatography (5% EtOAc/hexane) to give 27 (22.3 mg, 80%)
as a colorless solid. ½aꢂ2D3 =ꢀ252.78 (c=0.51, CH2Cl2); IR (KBr): n˜ =3435,
2974, 2931, 1710, 1686, 1600, 1493, 1446, 1266, 1073, 755, 693 cmꢀ1
;
1H NMR (CD2Cl2): d=7.33–7.27 (m, 6H), 7.27–7.20 (m, 6H), 7.15–7.08
(m, 3H), 6.57 (d, J=3.2 Hz, 3H), 4.27 (m, 3H), 4.20 (m, 3H), 2.40 (ddd,
J=7.6, 1.6, 1.6 Hz, 3H), 2.24 ppm (d, J=7.6 Hz, 3H); 13C NMR
(CD2Cl2): d=154.2, 137.4, 136.3, 135.3, 133.6, 127.8, 126.5, 124.0, 63.8,
48.6, 47.9 ppm; HRMS (EI): m/z calcd for C39H30 [M+]: 498.2348; found:
498.2349.
Synthesis
17: A solution of ketone 14 (1.49 g, 8.88 mmol) and hydrazine monohy-
drate (1.72 mL, 35.5 mmol) in MeOH (45 mL) was stirred at ambient
temperature overnight. The evaporation of solvent and addition of
MeOH were repeated three times to remove the excess hydrazine. After
evaporation of the solvent, crude hydrazone 15 was obtained as white
28: To a solution of triflate 25 (30 mg, 0.042 mmol), [PdACHTUNGTRENNUNG(PPh3)2Cl2]
(4.4 mg, 0.006 mmol), and CuI (1.2 mg, 0.006 mmol) in DMF (4 mL)
under Ar atmosphere were added triethylamine (20.5 mL, 0.147 mmol)
and MeSi3CꢁCH (20.8 mL, 0.147 mmol) successively. The reaction mix-
ture was stirred at 558C for 4 h. The reaction mixture was quenched at
08C with aq. NH4Cl and extracted with EtOAc (5 mlꢂ3). The combined
organic extracts were washed with brine, dried over Na2SO4, filtered
through celite, and evaporated. The residue was purified by aluminum
oxide PTLC (5% EtOAc/hexane) to give 28 (7.1 mg, 30%) as a light-
yellow solid. ½aꢂ2D3 =ꢀ67.38 (c=0.27, CH2Cl2); IR (KBr): n˜ =3436, 2960,
solid. To
a solution of crude hydrazone 15 and NEt3 (12.4 mL,
88.9 mmol) in toluene (39 mL) at 08C under Ar atmosphere was added a
solution of iodine (4.96 g, 19.5 mmol) in toluene (50 mL). After stirring
at 08C for 10 min, the reaction was quenched with aq. Na2S2O3 until the
color of excess iodine disappeared. Water (50 mL) was added to the reac-
tion mixture, and the mixture was extracted with AcOEt (50 mlꢂ3). The
combined extracts were washed with 1m aq. HCl and brine, dried over
Na2SO4, filtered through celite, and evaporated. The residue was purified
by silica gel chromatography (10% AcOEt/hexane) to give a mixture of
gem-diiodide 16 and vinyl iodide 17 (2.83 g) as a yellowish solid. The
mixture was dissolved in THF (70 mL) under Ar atmosphere. tBuOK
(1.57 g, 14.0 mmol) was added to the solution at 08C, and the reaction
mixture was stirred at 08C for 30 min. The reaction was quenched with
aq. NH4Cl and the reaction mixture was extracted with AcOEt (50 mlꢂ
2933, 2141, 1655, 1250, 1098, 860 cmꢀ1 1H NMR (CD2Cl2): d=6.66 (s,
;
3H), 3.96 (s, 3H), 3.82 (s, 3H), 2.30 (d, J=7.6 Hz, 3H), 2.08 (d, J=
7.6 Hz, 3H), 0.15 ppm (s, 9H); 13C NMR (CD2Cl2): d=146.6, 136.94,
136.91, 136.1, 101.8, 100.5, 64.4, 47.9, 29.4, ꢀ0.8 ppm; HRMS (EI): m/z
calcd for C36H42Si3 [M+]: 558.2594; found: 558.2589.
Chem. Asian J. 2009, 4, 1329 – 1337
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1335