AlHujran et al.
JOCNote
FIGURE 1. X-ray structure (a) of the tetra-2-O-naphthoide 4
(dichloromethane molecules omitted for clarity) and (b) showing
the close π-π stacking between a pair of molecules of the tetramer
and the dichloromethane molecules.
FIGURE 2. X-ray structure (ORTEP 30% thermal ellipsoids) of
tri-2-O -naphthoide 5 containing a water molecule (hydrogen atoms
omitted for clarity).
SCHEME 1. Synthesis of the 2-Naphthoide Macrocycles
and hexamer 6 were obtained, in 15% and 10% yields,
respectively (Scheme 1).
The X-ray structures of 4-6 are shown below. Figure 1 is
of the tetramer, 4, which crystallized with two dichloro-
methane (DCM) molecules in a channel-type clathrate, in
which one of the DCM molecules has a close contact distance
of 2.259 A with a carbonyl oxygen.10 The structure is in a
1,3-alternate-type conformation, similar to what is com-
monly seen with many different calix[4]arenes. A similar
conformation was observed with the analogous tetra-1-
naphthoide 7, derived from 1-hydroxy-2-naphthoic acid
under similar conditions by Gerdil and Bernardinelli9 and
by Tanaka et al.6 with the tetrasalicylide obtained from the
reaction of 5-chlorosalicylic acid under similar conditions.
FIGURE 3. X-ray structure (a) space-filling and (b) packing dia-
gram viewed along the c axis of hexa-2-O-naphthoide 6 showing the
inclusion of four molecules of chloroform.
Figure 2 shows the X-ray structure of the trimer 5, which
crystallized from wet methanolic dichloromethane solution
as a water molecule-containing channel-type racemate con-
taining equal amounts of the P and M forms.11 The molecule
is propeller-shaped and has C3-symmetry and reveals short
˚
contacts of 2.619 and 2.619 A for the carbonyl oxygen atom
to a hydrogen atom of a tert-butyl group, O(2) H(13b),
and to a hydrogen atom on a naphthyl ring, O(2) H(4),
3 3 3
3 3 3
respectively. By analogy to TOT, 5 could be expected to be
potentially capable of effecting chiral discrimination with
either racemic or chiral guests. Our efforts to date, with three
different chiral reagents, however, have not succeeded in
being able to demonstrate similar properties for 5. This
finding is not unlike similar efforts which have been reported
by others to date with other TOT analogues that failed to
afford any chiral recognition properties.12
˚
The packing in 4 reveals close (3.396 A) π-π stacking of the
naphthyl rings between pairs of molecules in the crystal
lattice which could account for the fact that once crystallized,
redissolution in the same or other common solvents tested
could not easily be achieved. As a consequence possibly, in
contrast to 7, which forms clathrates with several different
solvents,10 we have been unable to produce other clathrates
with tetramer 4. Other short contacts of note from the X-ray
structure of 4, involving the DCM molecules, include 2.816,
Figure 3 is of the X-ray structure of the hexamer 6 that was
crystallized from chloroform/methanol and is in a 1,3,5-
alternate conformation.13 Four chloroform molecules are
clearly contained within the cavities of the two alternate
groups of naphthyl rings, as a cage-type clathrate. The only
significant short contacts revealed in the structure are 3.387
˚
2.944, and 3.369 A distances for the Cl(1) H(24), Cl(2)
3 3 3
3 3 3
H(15), and the Cl(3) C(13), respectively.
3 3 3
(8) Crystal data for 4: C46H28Cl4O8, M = 850.48, colorless prism
˚
(dichloromethane:methanol), space group C2/c (no. 15), a = 40.421(12) A,
o
3
˚
˚
˚
b = 11.179(3) A, c = 16.906(5) A, β = 95.979(6) , V = 7598(4) A , Z = 8,
Dc = 1.487 g/cm3, F000 = 3488.00, μ(Mo KR) = 3.699 cm-1, T = 123(1) K,
2θmax = 61.8°, 62787 reflections collected, 7442 unique (Rint = 0.0573).
Final GoF = 1.173, R1 (I > 2.00σ(I)) = 0.1071, R(all reflections) = 0.1093,
wR2(all reflections) = 0.3185.
(11) Crystal data for 5: C45H42O6 (H2O), M = 696.84, colorless prism,
3
˚
˚
˚
space group R3 (no. 148), a = 15.849(5) A, c = 26.950(9) A, V = 5863(3) A ,
Z = 6, Dc = 1.184 g/cm3, F000 = 2220, μ(Mo KR) = 0.79 cm-1, T = 153(2)
K, 2θmax = 61.8°, 25563 reflections collected, 2699 unique (Rint = 0.0307).
Final GoF = 1.128, R1 (I > 2.00σ(I)) = 0.0835, R(all reflections) = 0.0839,
wR2(all reflections) = 0.2405.
(9) (a) Gerdil, R.; Bernardinelli, G. Acta Crystallogr. 1985, C41, 1523.
Unsolvated compound 7 crystallized in the P42/n space group. (b) An
incorrect structure for this compound is shown as “Figure 7.34” In Supra-
molecular Chemistry, 2nd ed.; Steed, J. W., Atwood, J. L., Eds.; John Wiley &
Sons, Ltd.: Chichester, UK, 2009.
(12) (a) Harris, T. D.; Oruganti, S. R.; Davis, L. M.; Keehn, P. M.; Green,
B. S. Tetrahedron 1987, 43, 1519-1540 and references cited therein. (b) Ollis,
W. D.; Stoddart, J. F. Inclusion Compounds; Atwood, J. L., Davies, J. E. D.,
MacNicol, D. D., Eds.; Academic Press: London, UK, 1984; Vol. 2, p 170.
(10) Suwinska, K.; Gerdil, R. Acta Crystallogr. 1987, C43, 898. The
clathrates all crystallized in the centrosymmetric P1 space group.
972 J. Org. Chem. Vol. 76, No. 3, 2011