142
B. S. Creaven et al. / Tetrahedron 60 (2004) 137–143
clip 7 (0.45 g, 0.80 mmol), 1-bromobutane (0.43 mL,
0.55 g, 4.0 mmol, 25% excess) in DMSO (20 mL) were
dissolved at 110 8C. Anhydrous potassium carbonate
(1.72 g, 12.5 mmol) was then added in one portion and
heating continued for 48 h. The reaction was poured onto
water (150 mL) and stirred for 20 min. After addition of
Hyflo-Supercel (6 g) to the solution, it was filtered and
washed thoroughly with water. Extraction with CHCl3
(50 mL£3), followed by drying with MgSO4 yielded 0.41 g
9 (65%). IR: 1674 (CvO). C48H58N4O6 theory: C, 73.26; H,
7.43; N, 7.12. Found: C, 73.67; H, 7.55; N, 7.24. Compound
10 was similarly prepared using 1-bromohexane. Yield:
1.17 g (73%); mp 260–265 8C. IR: 1657 (CvO).
C56H74N4O6 theory: C, 74.80; H, 8.29; N, 6.23. Found: C,
75.08; H, 8.33; N, 6.19.
Acknowledgements
J.F.G. to Dublin City University for the purchase of a
Siemens-Bruker P4 diffractometer; J.P.McD. to the Gradu-
ate Training Programme; B.S.C., J.Mc.G., and B.A.M. to
the Irish Higher Education Authority for its funding of the
NCSR; B.A.M. to Syntex, University College Dublin, and
Enterprise Ireland, for initial funding of this work.
References and Notes
1. Feiters, M. C. Comprehensive Supramolecular Chemistry;
¨
Atwood, J. L., Davies, J. E. D., MacNicol, D. D., Vogtle, F.,
Reinhoudt, D. N., Lehn, J.-M., Eds.; Elsevier/Pergamon:
Elmsford, 1996; Vol. 10, pp 267–360.
3.1.4. 1,6:3,4-Bis(1,2-xylylene)tetrahydro-3a,6a-bis(4-
methoxy-phenyl)imidazo[4,5-d]imidazole-2,5(1H,3H)-
dione (11). 4,40-Bis(methoxyphenyl)glycoluril (2) (0.49 g,
1.4 mmol) and freshly ground potassium hydroxide
(0.80 g, 14 mmol) in DMSO (10 mL) were heated to
120 8C with vigorous stirring for 20 min. a,a0-Dibromo-
o-xylene (0.80 g, 3.0 mmol) was added in one portion and
stirring was continued at this temperature for 2 h. On
cooling, the reaction mixture was added to water
(100 mL) and stirred for 30 min. The resulting precipitate
was collected by filtration, washed with water
(3£100 mL) and ether (3£50 mL), and reduced to dryness
under vacuum to yield 0.50 g (65%). IR: 1690 (CvO).
C34H30N4O4 theory: C, 73.10; H, 5.41; N, 10.03. Found:
C, 72.89; H, 5.36; N, 9.93.
2. Tanford, C. The Hydrophobic Effect. Wiley Interscience: New
York, 1973.
3. We prefer the term ‘aryl stacking’ to indicate binding motifs in
which there is a net attraction between aromatic surfaces, as
the label p–p interactions is potentially misleading, denoting
a repulsive effect. The model proposed by Hunter and Sanders
has been widely accepted as accurately describing and
predicting geometries in which p–s attractive terms outweigh
p–p repulsions. In particular they emphasise that it is not the
overall donor–acceptor properties of aromatic surfaces but
rather their atom-to-atom interactions at the points of contact
that determine the energy and geometry of the interaction
Hunter, C.; Sanders, J. J. Am. Chem. Soc. 1990, 112,
5525–5534.
4. (a) Rebek, J., Jr. Angew. Chem. 1990, 102, 261–272. (b)
Rotello, V. M.; Viani, E. A.; Deslongchamps, G.; Murray,
B. A.; Rebek, J., Jr. J. Am. Chem. Soc. 1993, 115, 797–798.
5. (a) Sijbesma, R. P.; Nolte, R. J. M. Top. Curr. Chem. 1995,
175, 26. (b) Rowan, A. E.; Elemans, J. A. A. W.; Nolte, R. J.
M. Acc. Chem. Res. 1999, 32, 995–1006. (c) Elemans, J. A. A.
W.; Rowan, A. E.; Nolte, R. J. M. Ind. Engng Chem. Res.
2000, 39, 3419–3428.
3.1.5. 1,6:3,4-Bis(3,6-dihydroxy-1,2-xylylene)tetrahydro-
3a,6a-bis(4-methoxyphenyl)imidazo[4,5-d]imidazole-
2,5(1H,3H)-dione (12). 4,40-Bis(methoxyphenyl)glycoluril
bisether (4) (0.34 g, 0.78 mmol), p-toluenesulfonic acid
monohydrate (0.60 g, 3.2 mmol) and 1,2-dichloroethane
(7 mL) were placed in a 25 mL round-bottomed flask fitted
˚
with a Dean and Stark apparatus containing 4 A molecular
sieves, and heated to reflux with stirring for 10 min.
Hydroquinone (0.33 g, 3.0 mmol) was added in one portion
and the reaction was further refluxed for 2 h. A brown
precipitate formed. On cooling, 1,2-dichloroethane (12 mL)
was added. The resulting solid was collected by filtration,
washed with water (2£50 mL), ethanol (2£50 mL), and
ether (3£30 mL), and dried to constant weight under
vacuum to yield 0.47 g (97%). IR: 3400 (OH), 1710
(CvO). C34H30N4O8 theory: C, 65.59; H, 4.86; N, 9.00.
Found: C, 65.17; H, 4.71; N, 8.93.
6. Holder, S. J.; Elemans, J. A. A. W.; Donners, J. J. J. M.;
´
Boerakker, M. J.; De Gelder, R.; Barbera, J.; Rowan, A. E.;
Nolte, R. J. M. J. Org. Chem. 2001, 66, 391–399.
7. Reek, J. N. H.; Kros, A.; Nolte, R. J. M. Chem. Commun. 1996,
245–247.
8. (a) Murray, B. A.; Whelan, G. S. Pure Appl. Chem. 1996, 68,
1561–1567. (b) Whelan, G. S. PhD Thesis, University College
Dublin/National University of Ireland, 1995. (c) McDonagh,
J. P. MSc Thesis, Institute of Technology Tallaght/National
Council for Educational Awards, 1999.
9. (a) Reek, J. N. H.; Elemans, J. A. A. W.; Nolte, R. J. M. J. Org.
Chem. 1997, 62, 2234–2243. (b) Reek, J. N. H.; Priem, A. H.;
Engelkamp, H.; Rowan, A. E.; Elemans, J. A. A. W.; Nolte,
R. J. M. J. Am. Chem. Soc. 1997, 119, 9956–9964.
10. Smeets, J. W. H.; Sijbesma, R. P.; van Dalen, L.; Spek, A. L.;
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3710–3717.
3.1.6. 1,6:3,4-Bis(3,6-dimethoxy-1,2-xylylene)tetrahydro-
3a,6a-bis(4-methoxyphenyl)imidazo[4,5-d]imidazole-
2,5(1H,3H)-dione (13). 4,40-Bis(methoxyphenyl)glycoluril
bis-ether (4) (0.219 g, 0.50 mmol), acetic anhydride
(0.5 mL), and trifluoroacetic acid (0.5 mL) were heated
with stirring to 95 8C for 30 min. 1,4-Dimethoxybenzene
(0.15 g, 1.1 mmol) was added in one portion; stirring and
heating were maintained for 1 h. On cooling, methanol
(2 mL) was cautiously added, and the resulting precipitate
was collected by filtration, washed with water (2£50 mL),
and reduced to dryness under vacuum: yield 0.26 g (77%).
IR: 1729 (CvO). C38H38N4O8 theory: C, 67.25; H, 5.64; N,
8.26. Found: C, 66.99; H, 5.61; N, 7.95.
11. Reek, J. N. H.; Elemans, J. A. A. W.; de Gelder, R.; Beurskens,
P. T.; Rowan, A. E.; Nolte, R. J. M. Tetrahedron 2003, 59,
175–185.
12. Crystallographic data: chemical formula C61.5H54N4O6, mol-
ecular weight 945.09 g mol21, triclinic, space group P1 (No.
¯
˚
2), a¼11.5618(16), b¼14.1207(19), c¼15.7993(19) A,
a¼88.368(10),
b¼74.618(12),
g¼86.119(12),