PAPER
A Stable Chiral C2-Symmetric Diimidazolidinylidene and an Electron-Rich Tetraazafulvalene
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4.1 mmol) was heated at 65 °C for 18 h. Once cooled to r.t., the mix-
ture was opened to H2O (50 mL) and extracted with CHCl3 (3 × 20
mL). The combined extracts were dried over MgSO4, filtered and
concentrated under reduced pressure to leave a brown residue. The
residue was purified by column chromatography (EtOAc–PE, 1:1,
loaded as a solution in CH2Cl2) to give the dithione (0.39 g, 54%) as
a colourless solid, which can be recrystallised from MeOH to give
colourless needles.
Mp 228–226 °C; [a]D25 +42.3 (c 1.87, CH2Cl2).
IR (KBr) 2983, 2909, 1610, 1486, 1448, 1411, 1375, 1081 cm–1.
1H NMR (250 MHz, CDCl3): d = 1.47 (s, 6 H,CH3), 2.19 (s, 6 H,
ArCH3), 2.22 (s, 6 H, ArCH3), 2.27 (s, 6 H, ArCH3), 3.71–4.13 (m,
12 H, NCH2), 4.45 (m, 2 H, OCH), 6.92 (s, 4 H, ArH).
13C NMR (62.9 MHz, C6D6): d = 18.6, 20.9, 21.3, 28.2, 52.0, 54.5,
55.5, 79.2, 109.2, 122.4, 129.7, 130.2, 133.2, 133.3, 136.4, 143.5.
(4S,5S)-4,5-Bis[1-(2,6-diisopropylphenyl)imidazolidin-2-
ylidene-3-methyl]-2,2-dimethyl-1,3-dioxolane (7b)
The procedure for 8a was followed using Na (0.05 g, 2.2 mmol), K
(0.16 g, 4.2 mmol), toluene (20 mL) and (4S,5S)-4,5-bis[1-(2,6-di-
isopropylphenyl)imidazolidin-2-thio-3-methyl]-2,2-dimethyl-1,3-
dioxolane (6b) (0.20 g, 0.31 mmol), which gave the diylidene as a
viscous orange oil.
1H NMR (250 MHz, C6D6): d = 1.37 (m, 24 H, CH3), 1.55 (s, 6 H,
CH3), 2.82 (m, 2 H, CH), 2.98 (m, 2 H, CH), 3.20–3.80 (m, 12 H,
NCH2), 4.78 (app br t, 2 H, OCH), 7.30 (m, 6 H, ArH).
13C NMR (62.9 MHz, C6D6): d = 24.5, 25.0, 25.8, 27.8, 28.5, 29.1,
51.4, 52.3, 54.8, 78.3, 108.7, 129.7, 139.9, 143.4, 147.7, 147.9,
242.2.
13C NMR (62.9 MHz, CDCl3): d = 17.9, 18.0, 21.1, 27.0, 47.3, 49.2,
49.6, 77.3, 108.9, 129.5, 134.9, 136.4, 136.7, 138.2, 183.0.
ESI-MS: m/z (%) = 589.2 (95) [M + Na]+, 567.2 (100) [M + H]+.
HRMS–ESI: m/z [M + H]+ calcd for C31H43N4O2S2: 567.2827;
found 567.2824.
References
(1) (a) Perry, M. C.; Burgess, K. Tetrahedron: Asymmetry 2003,
14, 951. (b) Zang, T. Y.; Zang, H. Tetrahedron Lett. 2002,
43, 193. (c) Herrmann, W. A.; Kocher, C. Angew. Chem.,
Int. Ed. Engl. 1997, 36, 2162.
(2) (a) Weskamp, T.; Schattenmann, W. C.; Spiegler, M.;
Herrmann, W. A. Angew. Chem. Int. Ed. 1998, 37, 2490.
(b) Herrmann, W. A.; Reisinger, C. P.; Spiegler, M. J.
Organomet. Chem. 1998, 557, 93. (c) Haung, J.; Nolan, S.
P. J. Am. Chem. Soc. 1999, 121, 9889.
(3) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G.
Principles and Applications of Organotransition Metal
Chemistry; University Science Books: Mill Valley, 1987.
(4) (a) Herrmann, W. A.; Goossen, L. J.; Artus, G. R. J. Angew.
Chem., Int. Ed. Engl. 1996, 35, 2805. (b) Haung, J.;
Stevens, E. D.; Nolan, S. P.; Petersen, J. L. J. Am. Chem.
Soc. 1999, 121, 2674. (c) Weskamp, T.; Kohl, F. J.;
Hieringer, W.; Gleich, D.; Herrmann, W. A. Angew. Chem.
Int. Ed. 1999, 38, 2416. (d) Grasa, G. A.; Moore, Z.; Martin,
K. L. J. Organomet. Chem. 2002, 658, 126.
(5) (a) Enders, D.; Gielen, H.; Raabe, G.; Runsink, J.; Teles, J.
H. Chem. Ber. 1996, 129, 1483. (b) Herrmann, W. A.;
Goossen, L. J.; Artus, G. R. J.; Köcher, C. Organometallics
1997, 16, 2472. (c) Seiders, T. J.; Ward, D. W.; Grubbs, R.
H. Org. Lett. 2001, 3, 3325.
Anal. Calcd for C31H42N4S2O2: C, 65.69; H, 7.47; N, 9.88; S, 11.31.
Found: C, 65.42; H, 7.11; N, 9.62; S, 11.25.
(4S,5S)-4,5-Bis[1-(2,6-diisopropylphenyl)imidazolidin-2-thio-3-
methyl]-2,2-dimethyl-1,3-dioxolane (6b)
The procedure for 7a was followed using (4S,5S)-4,5-bis[1-(2,6-di-
isopropylphenyl)imidazolidinium-2-methyl]-2,2-dimethyl-1,3-di-
oxolane dibromide (5b) (1.15 g, 1.54 mmol), MeOH (20 mL),
pyridine (1.8 mL), 1,8-diazabicyclo[5.4.0]undec-7-ene (1.03 g,
6.76 mmol) and sulfur (0.15 g, 4.6 mmol). The crude product was
purified by column chromatography (EtOAc–PE, 1: 2, loaded as a
solution in CH2Cl2) to give the dithione (0.63 g, 63%).
Mp 188 °C (from Et2O–PE, 1:2); [a]D25 +50.3 (c 2.04, CH2Cl2).
IR (KBr): 2965, 2868, 1492, 1458, 1404, 1347, 1083 cm–1.
1H NMR (250 MHz, CDCl3): d = 1.20 (4 d, J = 6.5, 5.0 Hz, 24 H,
CH3), 1.49 (s, 6 H, CH3), 2.88 (sept, J = 7.5 Hz, 2 H, CH), 3.02
(sept, J = 7.5 Hz, 2 H, CH), 3.99 (m, 12 H, NCH2), 4.52 (app br t, 2
H, OCH), 7.21 (m, 4 H, ArH), 7.34 (t, J = 7.5 Hz, 2 H, ArH).
13C NMR (62.9 MHz, CDCl3): d = 24.2, 24.4, 24.6, 24.7, 28.6, 28.7,
49.1, 49.3, 49.8, 77.4, 108.6, 124.4, 129.2, 135.1, 147.3, 147.7,
184.5.
ESI-MS: m/z (%) = 651.4 (100) [M + H]+, 619.3 (15) [M – S]+.
HRMS–ESI: m/z [M + H]+ calcd for C37H55N4O2S2: 651.3784;
(6) (a) Marshall, C.; Ward, M. F.; Harrison, W. T. A.
Tetrahedron Lett. 2004, 45, 5703. (b) Duan, W. L.; Shi, M.;
Rong, G. B. Chem. Commun. (Cambridge) 2003, 2976.
(c) Clyne, D. S.; Jin, J.; Genest, E.; Gallucci, J. C.; Rajan
Babu, T. V. Org. Lett. 2000, 2, 1125. (d) Perry, M. C.; Cui,
X.; Burgess, K. Tetrahedron: Asymmetry 2002, 13, 1969.
(e) Bonnet, L. G.; Douthwaite, R. E.; Hodgson, R.
Organometallics 2003, 22, 4384.
found: 651.3766.
Anal. Calcd for C37H54N4O2S2: C, 68.2; H, 8.5; N, 8.4; S, 9.5.
Found: C, 68.3; H, 8.4; N, 8.6; S, 9.9.
(4S,5S)-4,5-Bis[1-(2,4,6-trimethylphenyl)tetraazafulvalene]-
2,2-dimethyl-1,3-dioxolane (7a)
(7) (a) Hitchcock, P. B.; Lappert, M. F.; Terrenos, P.;
Wainwright, K. P. J. Chem. Soc., Chem. Commun. 1980,
1180. (b) Coleman, A. W.; Hitchcock, P. B.; Lappert, M. F.;
Maskell, R. K.; Müller, J. H. J. Organomet. Chem. 1983,
250, C9.
To a mixture of sodium (0.05 g, 2.3 mmol) and potassium (0.18 g,
4.7 mmol) in toluene (20 mL) was added (4S,5S)-4,5-bis[1-(2,4,6-
trimethylphenyl)imidazolidin-2-thio-3-methyl]-2,2-dimethyl-1,3-
dioxolane (6a) (0.20 g, 0.35 mmol), and the mixture was heated to
50 °C for 18 h. After cooling to r.t., the toluene was separated from
the suspension via cannular filtration and removed under reduced
pressure to give the dimer of the desired product as a light yellow
solid.
1H NMR (250 MHz, C6D6): d = 1.56 (s, 6 H, CH3), 1.73 (s, 6 H,
ArCH3), 2.35 (s, 6 H, ArCH3), 2.48 (s, 6 H, ArCH3), 2.64–2.70 (m,
4 H, NCH2), 3.02–3.11 (m, 4 H, NCH2), 3.21–3.27 (dd, J = 7.0, 5.0
Hz, 2 H, NCH2), 3.92–3.97 (dd, J = 7.0, 5.0 Hz, 2 H, NCH2), 4.84
(app br t, 2 H, OCH), 6.77–6.80 (2 s, 4 H, ArH).
(8) Arduengo, A. J. III; Krafczyk, R.; Schmutzler, R.
Tetrahedron 1999, 55, 14523.
(9) (a) Mash, E. A.; Neilson, K. A.; Van Deusen, S.; Hemperly,
S. B. Org. Synth. 1990, 68, 92. (b) Fujimara, O.; de la Mata,
F. J.; Grubbs, R. H. Organometallics 1996, 15, 1865.
(10) Karkhanis, D. W.; Field, L. Phosphorus Sulphur Relat.
Elem. 1985, 22, 49.
(11) Crystallographic data (excluding structure factors) for the
structure in this paper were deposited with the Cambridge
Crystallographic Data Centre as supplementary publication
Synthesis 2006, No. 6, 1040–1044 © Thieme Stuttgart · New York