Secondary bonding-directed self-assembly of amino acid derived benziodazoles: Synthesis and structure of novel hypervalent iodine macrocycles

Full text of DOI:10.1021/ja0155276

J. Am. Chem. Soc. 2001, 123, 4095-4096
4095
Scheme 1. Preparation of Hypervalent Iodine Macrocycles 1
Secondary Bonding-Directed Self-Assembly of Amino
Acid Derived Benziodazoles: Synthesis and Structure
of Novel Hypervalent Iodine Macrocycles
Viktor V. Zhdankin,* Alexey E. Koposov, and Jason T. Smart
Department of Chemistry, UniVersity of Minnesota Duluth
Duluth, Minnesota 55812
Rik R. Tykwinski,* Robert McDonald, and
Angelina Morales-Izquierdo
Department of Chemistry, UniVersity of Alberta
Edmonton, Alberta T6G 2G2, Canada
ReceiVed January 9, 2001
Self-assembly of molecular subunits into supramolecular
structures via hydrogen bonding or a transition-metal coordination
is a well-documented phenomenon of exceptional significance.1
Secondary bonding between heavier main-group atoms has also
been recognized as an important noncovalent interaction that can
be exploited for the rational design of supramolecular structures.2
Secondary I‚‚‚O bonds represent an essential feature of structural
chemistry of hypervalent iodine.3 Recently, such secondary bond
interactions have been utilized to construct new soluble derivatives
of (tosyliminoiodo)benzene and iodosylbenzene.4 In the present
communication, we describe a novel self-assembly of organoio-
dine(III) molecules into chiral and optically pure hypervalent
iodine macrocycles (1, Scheme 1), which is directed by secondary
bonding between hypervalent iodine and oxygen atoms of the
amino acid fragment.
Macrocycles 1 were characterized by elemental analysis,
spectroscopic data,5 and single-crystal X-ray analyses for 1c and
1d.7 Single crystals of 1c suitable for X-ray crystallographic
analysis were obtained from CHCl3 or C2H2Cl4 and were analyzed
as the respective solvates; crystals of 1d were grown from
chloroform.7 Molecular diagrams of all three products (1c‚CHCl3,
1c‚C2H2Cl4, and 1d‚CHCl3) are quite similar with only slight
variations in the geometry and planarity. The ORTEP of 1c‚CHCl3
(one of the two crystallographically independent molecules) from
two different perspective views is shown in Figure 1.
Molecule 1c‚CHCl3 consists of a slightly distorted planar
macrocyclic system with three oxygens of the amino acid
carboxyls (O3, O3′, and O3′′) inside the ring and all three alkyl
groups above the plane (Figure 1). The incorporated CHCl3
solvent molecule is situated above the macrocycle on the 3-fold
axis such that the H is directed toward the center of the macrocycle
with a H‚‚‚O(3) distance of ca. 2.6 Å. Each iodine atom is
covalently bonded to carbon [I-C1 ) 2.092(12) Å] and nitrogen
[I-N ) 2.064(11) Å] and has three longer intramolecular contacts
with oxygen atoms [I-O2 ) 2.368(9) Å, I-O3 ) 2.524(9) Å,
and I-O3′ ) 2.877(9) Å]. With the consideration of primary and
secondary bonds, iodine atoms in 1 have the pentagonal-planar
geometry, which is analogous to that found in the solid state for
PhI(OAc)2.8 Secondary bonding between iodine and oxygen atoms
of the neighboring molecular subunits provides the driving force
for self-assembly of monomeric benziodazoles 3 into macrocyclic
molecules 1. The effects of secondary interactions between
carboxylate oxygens and the electron-deficient iodine centers are
evidenced by the small disparity between carboxylate C-O bond
lengths. Averaging the values for the two independent molecules
in 1c‚CHCl3 shows that C9-O3 at 1.251 Å is only slightly shorter
than C9-O2 at 1.287 Å. The internuclear distance between
oxygen atoms directed toward the center of the macrocycle 1c‚
CHCl3 (O3, O3′, and O3′′) is 3.31 Å, and ranges from 3.31 to
Macrocyclic products 1 were prepared by oxidation of the
corresponding N-(2-iodobenzoyl) amino acids 2 with dimethyl-
dioxirane in 76-90% yield (Scheme 1).5 We assume that the
initial products in this reaction are monomeric N-substituted
benziodazoles 3, subsequent trimerization of which affords the
final products 1.6
(1) (a) ComprehensiVe Supramolecular Chemistry; Lehn, J.-M., Chair Ed.;
Atwood, J. L., Davis, J. E. D., MacNicol, D. D., Vo¨gtle, F., Exec. Eds.;
Pergamon: Oxford, UK, 1987-1996; Vols. 1-11. (b) Leininger, S.; Olenyuk,
B.; Stang, P. J. Chem. ReV. 2000, 100, 853.
(2) Starbuck, J.; Norman, N. C.; Orpen, A. G. New J. Chem. 1999, 23,
969.
(3) (a) Batchelor, R. J.; Birchall, T.; Sawyer, J. F. Inorg. Chem. 1986, 25,
1415. (b) Boucher, M.; Macikenas, D.; Ren, T.; Protasiewicz, J. D. J. Am.
Chem. Soc. 1997, 119, 9366.
(4) (a) Macikenas, D.; Skrzypczak-Jankun, E.; Protasiewicz, J. D. Angew.
Chem., Int. Ed. 2000, 39, 2007. (b) Macikenas, D.; Skrzypczak-Jankun, E.;
Protasiewicz, J. D. J. Am. Chem. Soc. 1999, 121, 7164.
(5) Representative procedure: A freshly prepared 0.1 M solution of
dimethyldioxirane in acetone (40 mL, 4 mmol) was added to a stirred mixture
of N-(2-iodobenzoyl) leucine 2d (0.18 g, 0.5 mmol) in 5 mL of dry methylene
chloride at 0 °C. The color of the solution immediately changed from colorless
to light yellow. The reaction mixture was stirred at room temperature for an
additional 8 h, then the resulting white precipitate was collected by filtration,
washed with ether and methylene chloride, and dried in a vacuum to afford
0.14 g (78%) of product 1d, mp 155-156 °C dec. IR (KBr): 3082, 2958,
(7) Compound 1c‚CHCl3 (C37H37Cl3I3N3O9; formula weight 1154.75)
crystallized in the trigonal space group P3 (no. 143) with a ) 16.8651(12)
Å, c ) 9.6356(11) Å; V ) 2373.5(4) Å3, Z ) 2; R ) 0.0498 (3230 reflections
1
2366, 1716, 1643, 1560, 1280 cm-1. H NMR (DMSO-d6): δ 8.28 (d, 1H),
8.18 (d, 1H), 7.82 (t, 1H), 7.68 (t, 1H), 5.08 (m, 1H), 2.17 (t, 2H), 1.86 (m,
1H), 1.14 (d, 3H), 0.98 (d, 3H). 13C NMR (CDCl3): δ 179.2, 167.4, 134.9,
133.6, 131.2, 130.8, 130.3, 120.0, 62.6, 39.4, 27.6, 15.1, 12.4. Anal. Calcd
for C39H42I3N3O9: C, 43.47; H, 3.93; N, 3.90. Found: C, 43.37; H, 4.06; N,
3.71. ESI MS: m/z (%) 1100 (100), [M + Na]+. Additional synthetic and
characterization details are provided as Supporting Information.
2
2
2
with Fo2 g 2σ(Fo )), Rw ) 0.1339 for 4079 unique reflections with Fo
g
-3σ(Fo ). Compound 1c‚0.75C2H2Cl4 (C37.5H34.5Cl3I3N3O9; formula weight
1158.23) crystallized in the orthorhombic space group P212121 (no. 19) with
a ) 10.9591(12) Å, b ) 14.6367(17) Å, c ) 52.962(6) Å; V ) 8495.3(17)
Å3, Z ) 8; R ) 0.0578 (14777 reflections with Fo2 g 2σ(Fo )), Rw ) 0.1462
2
2
2
(6) The preparation and structure of several monomeric benziodazoles have
previously been reported in the literature, see: (a) Zhdankin, V. V.; Arbit, R.
M.; McSherry, M.; Mismash, B.; Young, V. G., Jr. J. Am. Chem. Soc. 1997,
119, 7408. Zhdankin, V. V.; Arbit, R. M.; Lynch, B. J.; Kiprof, P.; Young,
V. G., Jr. J. Org. Chem. 1998, 63, 6590. Zhdankin, V. V.; Smart, J. T.; Zhao,
P.; Kiprof, P. Tetrahedron Lett. 2000, 41, 5299. (b) Barber, H. J.; Henderson,
M. A. J. Chem. Soc. (C) 1970, 862. (c) Balthazar, T. M.; Godaz, D. E.; Stults,
B. R. J. Org. Chem. 1979, 44, 1447. Naae, D. G.; Gougoutas, J. Z. J. Org.
Chem. 1975, 40, 2129.
for 17413 unique reflections with Fo g -3σ(Fo ). Compound 1d‚CHCl3
(C40H43Cl3I3N3O9; formula weight 1196.82) crystallized in the monoclinic
space group P21 (no. 4) with a ) 11.0940(6) Å, b ) 17.3082(10) Å, c )
12.0815(7) Å; â ) 105.3626(10)o; V ) 2237.0(2) Å3, Z ) 2; R ) 0.0260
(8412 reflections with Fo2 g 2σ(Fo )), Rw ) 0.0617 for 8866 unique reflections
2
2
2
with Fo g -3σ(Fo ).
(8) Alcock, N. W.; Countryman, R. M.; Esperas, S.; Sawyer, J. F. J. Chem.
Soc., Dalton Trans. 1979, 854. Lee, C.-K.; Mak, T. C. W.; Li, W.-K.; Kirner,
J. F. Acta Crystallogr. 1977, B33, 1620.
10.1021/ja0155276 CCC: $20.00 © 2001 American Chemical Society
Published on Web 04/06/2001

4096 J. Am. Chem. Soc., Vol. 123, No. 17, 2001
Communications to the Editor
Figure 2. ESI-MS for macrocycle 1d comparing complexation with H+,
Na+, and K+ (nitromethane solvent).
[M + K]+ and [M + H]+ are also observed. Less intense patterns
are present for H+, Na+, and K+ complexes of the oligomers of
3d, including the tetrameric, dimeric, and monomeric species.
Addition of both NaCl and KCl to a nitromethane solution of
1d followed by MS analysis shows an increased signal for [1d
+ K]+ at the expense of [1d + Na]+, and this change is concurrent
with increased signals for the dimeric and monomeric species.
Analysis of solutions of 1d following addition of either LiCl or
Pb(ClO4)2 showed no evidence of complexation with these cations.
Addition of AgOTf under similar conditions afforded weak signals
for both [1d + Ag]+ and [dimer + Ag]+.
In conclusion, we have reported the first example of self-
assembly of organoiodine(III) molecules into a hypervalent iodine
macrocycle, which is directed by secondary bonding between
trivalent iodine and oxygen. X-ray data on macrocycles 1 clarify
the structure of these synthetically useful benziodazoles.6 Fur-
thermore, these novel hypervalent iodine macrocycles 1 are
potentially useful ligands for selective binding of metal cations.
Figure 1. Top: Perspective view of one of two crystallographically
independent molecules of 1c‚CHCl3 (CHCl3 removed for clarity). Se-
lected distances [Å] and angles [deg]: I-N 2.064(11), I-C1 2.092(12),
I-O2 2.368(9), I-O3 2.524(9), I-O3′ 2.877(9); O2-I-N 164.6(4),
O2-I-C1 85.0(4). Bottom: Edge-on view of 1c showing orientations
of the isopropyl groups and the CHCl3 solvent molecule. Hydrogen atoms
are omitted.
3.42 Å in 1c‚C2H2Cl4 and 1d‚CHCl3. These three oxygens
therefore circumscribe a relatively small cavity within the
macrocycle. The secondary bonding I-O3 interactions likely
dissipate a fair amount of charge density from the oxygens such
that electrostatic repulsions are diminished. It is still somewhat
surprising, however, that the formation of macrocycle 1 is favored
over that of the monomer 3 or a polymer species,4 situations in
which any negative electrostatic interactions could be reduced or
eliminated.
Acknowledgment. This work was supported by a research grant from
the National Science Foundation (NSF/CHE-9802823), the National
Sciences and Engineering Research Council of Canada, and the University
of Alberta.
As a result of the central oxygens, the electron-rich cavity of
macrocycles 1 should be suitable for complexation of cations in
a manner similar to that observed for the slightly larger guanosine
quartet.9,10 ESI-MS analyses of macrocyclic compounds 1 provide
information about their structure in solution and offer empirical
evidence as to their selective cation binding.11 The ESI-MS
spectrum for 1d from a nitromethane solution is shown in Figure
2 and is typical of that observed for the macrocycles. The most
significant peak in is that of the trimeric species 1d complexed
with a single sodium cation at m/z 1100.12 Smaller signals for
Supporting Information Available: Synthetic and characterization
1
data for all new compounds, H and 13C spectra for compounds 1b and
1c, ESI MS for compounds 1c and 1d, and X-ray crystallographic details
for compounds 1c‚CHCl3, 1c‚C2H2Cl4, and 1d‚CHCl3 (PDF). This
material is available free of charge via the Internet at http://pubs.acs.org.
JA0155276
(11) Su¨ssmuth, R.; Jung, G.; Winkler, F. J.; Medina, R. Eur. Mass.
Spectrom. 1999, 5, 289. Tsuda, A.; Moriwaki, H.; Oshima, T. J. Chem. Soc.,
Perkin Trans. 2 1999, 1235. Oshima, T.; Matsuda, F.; Fukushima, K.; Tamura,
H.; Matsubayashi, G.; Arakawa, R. J. Chem. Soc., Perkin Trans. 2 1998, 145.
(12) The signal at m/z 399 is not well understood. This peak shows with
relatively low intensity at low sampling cone/skimmer lens voltages, increasing
as the voltages are increased to better tune signals at higher m/z values. Exact
mass measurement provides a good match for the addition of ammonia to the
monomer 1d, [M + Na + NH3]+, although the presence of ammonia in the
sample is yet to be explained. Similar behavior is observed for compound 1c.
(9) Forman, S. L.; Fettinger, J. C.; Pieraccini, S.; Gottarelli, G.; Davis, J.
T. J. Am. Chem. Soc. 2000, 122, 4060. Kotch, F. W.; Fettinger, J. C.; Davis,
J. T. Org. Lett. 2000, 2, 3277. Sidorov, V.; Kotch, F. W.; El-Kouedi, M.;
Davis, J. T. Chem. Commun. 2000, 2369.
(10) Andrisano, V.; Gottarelli, G.; Masiero, S.; Heijne, E. H.; Pieraccini,
S.; Spada, G. P. Angew. Chem., Int. Ed. 1999, 38, 2386.