1,1,2-Triphenyl-1,2-ethanediol: A host for carboxylic acids and amides in coordinatoclathrates

Article abstract of DOI:10.1002/(SICI)1099-0690(199806)1998:6<1071::AID-EJOC1071>3.0.CO;2-5

The chiral diols (R)- and (S)-1 are found to form inclusion compounds with carboxylic acids and amides, as indicated by the relevant IR spectra. Two clathrates, (R)-1 · CH₃CO₂H and (S)-1 · CH₃NHCHO have been characterized

Full text of DOI:10.1002/(SICI)1099-0690(199806)1998:6<1071::AID-EJOC1071>3.0.CO;2-5

FULL PAPER
1
,1,2-Triphenyl-1,2-ethanediol: A Host for Carboxylic Acids and Amides in
Ƞ
Coordinatoclathrates
a
b
a
Daniel Ridder , Hartmut Wunderlich , and Manfred Braun*
a
Institut für Organische Chemie und Makromolekulare Chemie,
Institut für Anorganische Chemie und Strukturchemie,b
Universität Düsseldorf, Universitätsstraße 1, D-40225 Düsseldorf, Germany
Fax: (internat.) ϩ 49(0)211/81-13085
E-mail: braunm@uni-duesseldorf.de
Received January 29, 1998
Keywords: Chirality / Crystal structures / Hydrogen bonds / Inclusion compounds / Supramolecular chemistry
The chiral diols (R)- and (S)-1 are found to form inclusion
compounds with carboxylic acids and amides, as indicated
crystal structures. The interaction between the diol 1, which
functions as the host compound, and the guest compounds,
is based on hydrogen bonds. Enantiomerically pure 1 can
serve as chiral solvating agent in NMR spectroscopy.
by the relevant IR spectra. Two clathrates, (R)-1 · CH
3 2
CO H
and (S)-1 · CH NHCHO have been characterized by their
3
Inclusion compounds formed by crown ethers and cryp-
tands are the most prominent representatives of the supra-
[1]
molecular structures that rely on non-covalent bonding.
In addition, clathrates, which exist only in the solid state,
have attracted considerable interest in recent years.[ Clath-
rates are becoming more and more important, not only be-
cause of their novel and unprecedented structures, but also
due to their potential application in the separation of differ-
ent compounds or isomers. Chiral host molecules, which
are either found among natural products or are designed
and synthesized, have proved to be suitable for performing
2]
a mixture of organic compounds.[10] We learned that this is
easily accomplished by the addition of acetic acid, which
causes the precipitation of the diol 1. It was this unexpected
reaction that prompted the present study.
[2f][2i]
enantioselective reactions
and for the resolution of ra-
[
2b][2c][2i][2j][2k]
cemates,
as a result of enantio-differentiating
clathration. Many of the synthetic host compounds used for
[7]
The crystal structure of racemic (R)-1·(S)-1 reveals
these purposes are C -symmetric. The tartaric acid derived
2
that the vicinal hydroxy groups are orientated in a gauche
conformation, so that one of the phenyl groups of the di-
phenylhydroxymethyl moiety and the phenyl group at the
stereocenter occupy antiperiplanar positions. Hydrogen
bonds are directed from the tertiary OH group of one mol-
ecule of the diol 1 to the oxygen atom of the secondary OH
group in its enantiomer, and vice versa. We have found the
IR spectrum, measured in KBr, to be in accordance with
this arrangement; only two absorptions due to OH stretch-
ing vibrations are seen, one attributable to the non-asso-
α,α,αЈ,αЈ-tetraaryl-1,3-dioxolane-4,5-dimethanols (“TAD-
[
3]
DOLs”)
have found particularly widespread appli-
[
4]
cation. Although 1,1-diaryl-1,2-propanediols lack a moi-
ety similar to the rigid backbone of the TADDOLs, they
also form clathrates with various types of compounds and
[5]
facilitate the separation of enantiomers. It seems that the
diarylhydroxymethyl group[ present in both the TAD-
DOLs and the 1,1-diaryl-1,2-propanediols plays a crucial
role. Recently, methanol has been shown to form clathrates
with the diol 1, and the crystal structures of rac-1 and (R)-
6]
Ϫ1
ciated secondary (3559 cm ) and the other due to the asso-
1
have been determined.[7] In this paper, we report for the
Ϫ1
ciated tertiary (3458 cm ) hydroxy group.
first time on the preparation, spectroscopy and X-ray struc-
ture determination of clathrates in which (R)- or (S)-1,1,2-
triphenyl-1,2-ethanediol (1) serves as the host compound.
However, the crystal structure of enantiomerically pure
[7]
(
R)-1, determined independently by WeberЈs group and
ourselves, reveals that diol 1 does not show a preference
Monoesters derived from triphenylglycol 1, available in for one single conformation. Both the anti and the gauche
both enantiomeric forms from (R)- and (S)-mandelic acid, conformations are found in the asymmetric unit, as shown
have found wide application in asymmetric aldol ad- in Figure 1. There are both hydrogen-bonded and free
ditions and ester enolateϪimine condensations.[9] When hydroxy groups, a result which again corresponds to the IR
[8]
these reactions are performed, the chiral auxiliary reagent spectrum of (R)-1 measured in KBr. The spectrum shows
1
is usually liberated at the end and has to be removed from sharp absorption peaks due to the free secondary and ter-
Eur. J. Org. Chem. 1998, 1071Ϫ1076

WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
1434Ϫ193X/98/0606Ϫ1071 $ 17.50ϩ.50/0
1071

D. Ridder, H. Wunderlich, M. Braun
FULL PAPER
tiary OH groups (3564 and 3536 cmϪ1), which are assigned Figure 2. Crystal structure of (R)-1 · CH
CO
aromatic H atoms are omitted for the sake of clarity
3
2
H; displacement el-
lipsoids at 25% probability level for all non-hydrogen atoms; the
to the anti conformer, as well as broad absorptions at 3449
[
a]
Ϫ1
(
tertiary OH group) and 3328 cm (secondary OH group)
due to the gauche conformer. No cavities can be detected in
the crystal structure of (R)-1 and thus, at first glance, this
molecule does not appear to be capable of acting as a suit-
able host for the formation of inclusion compounds.
Figure 1. Crystal structure of (R)-1; displacement ellipsoids at 25%
probability level for all non-hydrogen atoms; in the second mole-
cule of the asymmetric unit only the OH groups are labelled
[
a]
˚
Selected distances [A] and angles [°]: O1ϪHO1 0.95(7), O1···O4
.855(3), HO1···O4 2.02(9), O2ϪHO2 0.83(3), O2···O4a 2.699(3),
2
HO2···O4a 1.87(3), O3ϪHO3 0.95(10), O3···O2 2.631(3), HO3···O2
2
.24(7);
O1ϪHO1···O4
154(3),
O2ϪHO2···O4a
175(3),
O3ϪHO3···O2 174(4).
3 2
Figure 3. View along the a axis of (R)-1 · CH CO H showing stacks
and channels; displacement ellipsoids at 25% probability level for
all non-hydrogen atoms; the aromatic H atoms are omitted for the
sake of clarity
When, however, acetic acid is added to solutions of (R)-
1
in aprotic solvents (cyclohexane or diethyl ether), a vo-
1
luminous, white precipitate forms immediately. The H-
NMR spectra, measured in CDCl , of all samples thus pre-
3
pared, reveal a 1:1 ratio of (R)-1 and acetic acid. The crystal
structure unambiguously confirms this stoichiometric ratio
of the clathrate (R)-1 · CH CO H, three asymmetric units
3
2
of which are shown in Figure 2. Clearly, a nine-membered
ring is formed as a result of two hydrogen bonds between
the diol and the carboxyl moiety. The carboxylic proton
bonds to the oxygen atom of the secondary hydroxy group,
while the tertiary hydroxy proton is linked to the carbonyl
oxygen atom. Since the proton of the secondary alcohol is
not involved in the nine-membered ring, it is able to form
another, even stronger hydrogen bond, directed toward the
carbonyl oxygen atom of the neighboring triphenylgly-
colϪacetic acid unit, and thereby connects the (R)-1 ·
CH CO H chelate units together. A view along the a axis
The low vibrational frequency of the secondary OH
Ϫ1
group (3255 cm ) in the IR spectrum of (R)-1 · CH CO H
3
2
3
2
measured in KBr also points to clathrate formation. Fur-
of the resulting stacks is given in Figure 3. The acetic acid
is located in channels, and each molecule of the acid is sur-
rounded by five phenyl groups of the staggered diol (R)-1.
The distance between the guest molecule and the nearest
Ϫ1
thermore, the carbonyl frequency is lowered to 1678 cm
compared to the values documented for monomeric acetic
Ϫ1
[11a]
acid (1788 cm in the gas phase)
and the dimeric acid
Ϫ1
[11a][11b]
(
1747 in the gas phase; 1715 cm for the liquid).
carbon atom of the respective host molecule ranges from
˚
The structure shown in Figure 3 suggests that other car-
2
.916 to 3.847 A.
boxylic acids might also be incorporated in the channels.
Indeed, on the basis of characteristic IR shifts, we were able
to prove the formation of clathrates between (R)-1 and
cyclohexyl-, phenyl-, 4-hydroxyphenyl-, chloro-, bromo-,
iodo-, and dichloroacetic acid, cinnamic and propionic
acid, as well as 2-chloro- and 2-bromopropionic acid. The
short hydrogen bond of the secondary OH group is con-
sidered to make a key contribution to the stability of the
coordinatoclathrates. Thus, the wavenumber ν˜ of the OϪH
1
1072
Eur. J. Org. Chem. 1998, 1071Ϫ1076

1,1,2-Triphenyl-1,2-ethanediol: A Host for Carboxylic Acids and Amides in Coordinatoclathrates
FULL PAPER
stretching vibration of the associated secondary hydroxy bonds is seen in both clathrates. Therefore, it is assumed
group in a gauche conformation gives an indication of clath- that the lattice of the host, diol 1, is similar in both cases,
rate formation when compared with the vibration of the apart from the fact that (R)-glycol 1 is used for clathration
non-associated secondary hydroxy group. The latter value ν˜ 2 of acetic acid, whereas the N-methylformamide adduct is
is taken from the IR data of the racemic diol rac-1, which formed with (S)-1. Indeed, isotypy results by transfor-
contains such a free secondary OH group, as indicated by mation into the clathrates with identical isomers. Besides
the crystal structure. The differences in wavenumber ∆ ν˜ ϭ N-methylformamide, N,N-dimethylformamide also forms a
ν˜ Ϫ ν˜ for the various clathrates are given in Table 1; the clathrate when treated with diol (S)-1; it is characterized
1
2
Ϫ1
values are seen to range from 148 to 304 cm
.
by the relatively low frequencies of the hydrogen-bonded
hydroxy groups in the IR spectrum (see Table 1 and the
Experimental Section).
Table 1. Differences between the wavenumbers of the secondary
OH vibration in the clathrates and that in diol 1
Ϫ ν˜ [
a]
Clathrate
∆ ν˜ ϭ ν˜
1
2
Figure 4. Crystal structure of (S)-1 · CH NHCHO; displacement
3
ellipsoids at 25% probability level for all non-hydrogen atoms; the
[
a]
aromatic H atoms are omitted for the sake of clarity
(
(
(
(
(
(
(
(
(
(
(
(
(
(
R)-1 · CH
R)-1 · PhCH
S)-1 · 4-HOC
R)-1 · c-C 11-CH
R)-1 · ClCH CO
R)-1 · BrCH CO
R)-1 · ICH CO
R)-1 · Cl CHCO
CH CO
3
CO
2
2
H
2
Ϫ304
Ϫ265
Ϫ312
Ϫ299
Ϫ193
Ϫ211
Ϫ222
Ϫ148
Ϫ252
Ϫ155
Ϫ172
Ϫ267
Ϫ199
Ϫ189
CO
H
6
H
4
CH
2
CO
2
2
H
H
6
H
2
CO
2
2
H
2
2
H
2
2
H
2
2
H
R)-1 · CH
3
2
2
H
R)-1 · rac-CH
R)-1 · rac-CH
3
CH(Cl)CO
CH(Br)CO
2
H
3
2
H
2
R)-1 · PhCHϭCHCO H
S)-1 · CH
3
NHCHO
NHCHO
S)-1 · (CH )
3 2
[
a]
ν˜
ϭ associated sec. OH in clathrate (gauche conformation); ν˜
ϭ
2
1
non-associated sec. OH in rac-1 (gauche conformation) ϭ 3559
cm
Ϫ1
.
[
a]
˚
Selected distances [A] and angles [°]: O1ϪHO1 0.78(3), O1···O3
.847(2), HO1···O3 2.11(4), O2ϪHO2 0.80(3), O2···O3a 2.762(2),
2
Coordinatoclathrates were also formed between the en-
antiomerically pure diol 1 and carboxylic amides. In the 2.46(3);
C3ϪH3···O2 124(2).
HO2···O3a 1.96(3), C3ϪH3 0.99(3), C3···O2 3.131(3), H3···O2
O1ϪHO1···O3
156(3),
O2ϪHO2···O3a
173(3),
case of N-methylformamide, the host/guest ratio of 1:1 (S)-
1
1
· CH NHCHO was not only proved by H-NMR spec-
3
troscopy, but also by thermogravimetry, which indicated the
loss of 17 mass percent for N-methylformamide. A differen- phenylglycol 1 on the one hand, and the clathrates (R)-1 ·
tial thermoanalysis (DTA) shows a sharp melting point at CH CO H and (S)-1 · CH NHCHO on the other, is clearly
3Ϫ84°C, indicating considerable thermostability of the evident. The host, diol 1, does not itself contain tubular
The fundamental difference between rac- or (R)-tri-
3
2
3
8
clathrate.
voids or channels into which the guest molecules can fit.
Instead, the particular structure of the corresponding in-
clusion compound is only formed when host and guest are
combined. Since it is the guest molecule which shapes the
structure, the term “coordinatoclathrates”, introduced by
Weber,[ is applied to the adducts (R)-1 · CH CO H and
13]
3
2
(
S)-1 · CH NHCHO investigated here.
3
In our search for applications of the interaction that
takes place between triphenylglycol 1 and compounds suit-
1
able for clathration, the H-NMR spectra of several chiral
Unambiguous proof of the structure of the inclusion compounds were recorded in the presence of (R)-1. It was
compound (S)-1 · CH NHCHO was again provided by the found that enantiomeric 2-chloropropanoic acid (2a) and
3
crystal structure (Figure 4). A remarkable hydrogen bond its amide 2b, as well as mandelic acid (3) and hydroxyphos-
between the formyl proton[ and the oxygen atom at the phonate 4, show non-equivalence in their spectra; charac-
stereocenter, and a second hydrogen bond of the tertiary teristic shift differences are given in the formulae. The
hydroxy group to the carbonyl oxygen, result in the forma- ability of (R)-1 to function as a chiral solvating agent is
12]
1
tion of an eight-membered ring. Here again, the stability of demonstrated in Figure 5, which shows sections of the H-
the clathrate is distinctly enhanced by a hydrogen bond of NMR spectra of racemic as well as (S)- and (R)-mandelic
the secondary hydroxy group directed toward the carbonyl acid (3) in the presence of (R)-1. Remarkably, the determi-
oxygen atom of the neighboring chelate. Despite the differ- nation of enantiomeric excesses based thereon is possible
1
ent character of the guest molecules, acetic acid and N- simply from 300-MHz H-NMR spectra, in contrast to the
methylformamide, a similar arrangement of hydrogen TADDOLs, for which 13C- or F-NMR spectroscopy is
19
Eur. J. Org. Chem. 1998, 1071Ϫ1076
1073

D. Ridder, H. Wunderlich, M. Braun
generally required when they are used for resolutions of al- spectra were recorded with a Varian VXR 300 instrument, FT-IR
FULL PAPER
[
14]
spectra with Bruker Vektor 22 or Bruker IFS 66 spectrometers, and
differential thermoanalyses with a Mettler TG-DTA TA 1 appa-
ratus. Melting points (uncorrected) were determined with a Büchi
B-540 melting point apparatus.
cohols.
(
R)-1,1,2-Triphenylethane-1,2-diol [(R)-1] or (S)-1,1,2-Triphenyl-
[15]
ethane-1,2-diol [(S)-1]: Obtained according to ref.
crystals, m.p. 127Ϫ128°C; (R)-1: [α]
form); (S)-1: [α]
as colorless
ϭ ϩ219 (c ϭ 1.0, chloro-
2
0
D
2
0
D
ϭ Ϫ220 (c ϭ 1.0, chloroform). We do not rec-
[
7]
ommend reaction of methyl mandelate with phenyllithium in-
stead of phenylmagnesium bromide because the lithium reagent
causes partial racemization. This is clearly shown by the low optical
rotation of (R)-1 obtained in ref.[ . Ϫ IR (KBr): ν˜ ϭ 3564 cm
7]
Ϫ1
(
m, sec. OH, non-associated), 3536 (m, tert. OH, non-associated),
3
449 (m, tert. OH, associated), 3328 (m, sec. OH, associated), 3056
(
m), 3026 (m), 1491 (m), 1446 (s), 1166 (m), 1061 (m), 1007 (m),
1
7
66 (m), 750 (m), 736 (s), 715 (m), 697 (s), 613 (m). Ϫ H NMR
300 MHz, CDCl ): δ ϭ 2.6 [d, J(H,H) ϭ 3 Hz, 1 H, CH(OH)],
3.2 [s, 1 H, C(OH)Ph ], 5.5 [d, J(H,H) ϭ 3 Hz, 1 H, CH(OH)Ph],
7.0Ϫ7.4 (m, 13 H, Ar-H), 7.5Ϫ7.6 (m, 2 H, Ar-H). Ϫ C NMR
75 MHz, CDCl ): δ ϭ 77.44 [CH(OH)Ph], 80.70 [C(OH)Ph ],
26.13 (C of Ar), 126.65 (para-C of Ar), 127.01 (C of Ar), 127.29
para-C of Ar), 127.38 (C of Ar), 127.55 (C of Ar), 127.62 (para-C
of Ar), 128.06 (C of Ar), 128.37 (C of Ar), 138.78, 143.32 and
(
3
1
Figure 5. Sections of the H-NMR spectra (δ values) of mandelic
acid (3) in the presence of (R)-1; left: (S)-3; middle: rac-3; right:
2
1
3
(R)-3
(
1
(
3
2
1
45.07 (3 ipso-C of Ar).
rac-1,1,2-Triphenylethane-1,2-diol (rac-1): Prepared from racemic
methyl mandelate according to the procedure given in ref.[ , color-
15]
less needles, yield 66%, m.p. 165.5Ϫ167°C. Ϫ IR (KBr): ν˜ ϭ 3559
Ϫ1
cm (s, sec. OH, non-associated), 3458 (m, tert. OH, associated),
3
059 (m), 3027 (m), 1492 (m), 1448 (s), 1186 (m), 1059 (m), 1039
(
s), 1020 (m), 764 (m), 747 (s), 699 (s), 614 (m).
General Procedures for the Preparation of Clathrates from (R)- or
S)-1. Ϫ Procedure A: (R)- or (S)-1,1,2-triphenylethane-1,2-diol (1;
(
2
90.3 mg, 1.0 mmol) was dissolved in the minimum amount of dry
In conclusion, inclusion compounds with novel struc- diethyl ether and 1.0 mmol of the respective neat guest compound
was added. After slow, partial evaporation of the solvent, a crystal-
tures are obtained from 1,1,2-triphenyl-1,2-ethanediol (1)
line or amorphous precipitate formed, which was filtered off,
and polar guest molecules, namely carboxylic acids and
washed with a small amount of dry diethyl ether, and dried at room
amides. The interaction between host and guest molecules
temp. at oil-pump pressure (1 mbar). The formation of the clathrate
is largely determined by hydrogen bonding, as indicated by
was verified by FT-IR spectroscopy and/or crystal-structure analy-
crystal-structure analyses as well as IR spectroscopy. Com-
parison of the crystal structures of the diol (R)-1 with those
1
ses, and the host/guest ratio was determined by H-NMR spec-
troscopy (300 MHz, CDCl ). Ϫ Procedure B: A mixture of (R)- or
(S)-1,1,2-triphenylethane-1,2-diol (1; 290.3 mg, 1.0 mmol) and 1.0
3
of the adducts (R)-1 · CH CO H and (S)-1 · CH NHCHO
3
2
3
shows the latter to be coordinatoclathrates, in which the mmol of the appropriate guest compound was stirred in 20 ml of
polar guests are incorporated in channels formed by the cyclohexane. The resulting amorphous and voluminous precipitate
host due to aryl stacking and hydrogen bonding between was filtered off, washed twice with cyclohexane, and dried at room
temp. at oil-pump pressure (1 mbar). The clathration was verified
the chelates.
by FT-IR spectroscopy, and the host/guest ratio was determined
This work was supported by the Fonds der Chemischen Industrie.
as described above. ϪAccording to these procedures, the following
We would like to thank Dr. Ralf Devant (Merck AG, Darmstadt)
for helpful discussions. Special thanks go to Dr. Delia Waldmüller
were obtained:
for preliminary crystal-structure analyses.
3 2
(R)-1 · CH CO H (Procedure A): The product crystallized in col-
orless needles; yield: 290 mg (83%), m.p. 121Ϫ124°C; molar host/
Ϫ1
guest ratio ϭ 1:1. Ϫ IR (KBr): ν˜ ϭ 3459 cm (s, tert. OH, associ-
Experimental Section
ated), 3255 (m, sec. OH, associated), 1678 (s), 1450 (m), 1289 (m),
035 (m), 898 (m), 755 (m), 743 (s), 698 (s), 612 (m).
(
R)-, (S)- and rac-1,1,2-triphenyl-1,2-ethanediol (1) were pre-
1
[15]
pared according to ref.
Hydroxyphosphonate 4 was obtained by
the addition of diethyl phosphite to benzaldehyde; for non-racemic
samples of 4, the reaction was mediated by chiral additives.[ Di-
ethyl ether was distilled from sodium and stored under nitrogen.
Cyclohexane p.a. was purchased from Janssen Chimica. All chemi-
(R)-1 · PhCH CO H (Procedure B): Colorless, amorphous prod-
2
2
16]
uct was obtained; yield: 360 mg (84%), m.p. 105.5Ϫ106.5°C; molar
Ϫ1
host/guest ratio ϭ 1:1. Ϫ IR (KBr): ν˜ ϭ 3508 cm (m, tert. OH,
weakly associated), 3294 (m, sec. OH, associated), 1677 (s), 1495
cals used for clathrate formation are commercially available. They (m), 1449 (m), 1013 (m), 752 (m), 748 (m), 745 (m), 725 (m), 697
1
13
were purified by distillation or recrystallization. H- and C-NMR
(s), 611 (m).
1074
Eur. J. Org. Chem. 1998, 1071Ϫ1076

1,1,2-Triphenyl-1,2-ethanediol: A Host for Carboxylic Acids and Amides in Coordinatoclathrates
FULL PAPER
(S)-1 · 4-HOC
6
H
4
CH
2 2
CO H (Procedure A): Thin, colorless
(S)-1 · CH
NHCHO (Procedure A): Crystallization yielded 310
3
needles were obtained; yield: 410 mg (93%), m.p. 142.5Ϫ143.5°C; mg (89%) of colorless needles, m.p. 89Ϫ90°C; molar host/guest
Ϫ1
molar host/guest ratio ϭ 1:1 (300 MHz, [D
6
]DMSO). Ϫ IR (KBr): ratio ϭ 1:1. Ϫ IR (KBr): ν˜ ϭ 3403 cm (s, tert. OH, associated),
ν˜ ϭ 3489 cm (s, tert. OH, associated), 3294 (s, sec. OH, associ-
3360 (s, sec. OH, associated), 1664 (s), 1536 (m), 1493 (m), 1449
ated), 1672 (s), 1511 (s), 1448 (m), 1235 (s), 1171 (m), 896 (m), 752 (m), 1391 (m), 1172 (m), 1047 (m), 756 (s), 746 (s), 699 (s), 618 (m).
m), 742 (m), 698 (s), 612 (m).
Ϫ1
(
(
S)-1 · (CH
3 2
) NCHO: According to procedure A, a colorless,
(
R)-1 · c-C 11-CH CO H (Procedure A): The product crys-
tallized in thin, colorless needles; yield: 320 mg (74%), m.p. molar host/guest ratio ϭ 1:1. Ϫ IR (KBr): ν˜ ϭ ca. 3400 cm
21.5Ϫ123°C; molar host/guest ratio ϭ 1:1. Ϫ IR (KBr): ν˜ ϭ 3508 (shoulder, tert. OH, associated), 3370 (m, sec. OH, associated),
6
H
2
2
amorphous product (320 mg, 88%) was obtained, m.p. 86Ϫ88°C;
Ϫ1
1
Ϫ1
cm (m, tert. OH, weakly associated), 3260 (m, sec. OH, associ-
ated), 2924 (s), 2852 (m), 1684 (s), 1666 (m), 1449 (m), 1167 (m), 697 (s), 613 (m).
064 (m), 748 (m), 743 (m), 698 (s), 613 (m).
1658 (s), 1495 (m), 1448 (m), 1169 (w), 1062 (m), 751 (m), 701 (s),
1
Crystal-Structure Analyses: The crystals were grown as described
(
R)-1 · ClCH CO
H (Procedure A): The clathrate crystallized in above. All X-ray diffraction experiments were performed at room
thin, colorless needles; yield: 320 mg (86%), m.p. 98Ϫ101°C; molar
2
2
temp. using a four-circle diffractometer (Siemens P3) with graphite-
˚
Ϫ1
α
host/guest ratio ϭ 1:1. Ϫ IR (KBr): ν˜ ϭ 3495 cm (m, tert. OH, monochromated Mo-K radiation (λ ϭ 0.71073 A). The intensities
associated), 3366 (s, sec. OH, associated), 1700 (s), 1495 (m), 1448 were collected in ω/2Θ scan mode. No absorption correction was
Ϫ1
Ϫ1
(
m), 1213 (s), 1063 (m), 895 (m), 753 (s), 746 (s), 699 (s), 611 (s).
applied (0.078 mm < µ < 0.085 mm ). The structures were
[17a]
solved by direct methods with SHELXTL-PLUS
full-matrix least squares on F using SHELXL-93
and refined by
or SHELXL-
(
R)-1 · BrCH CO H: According to procedure B, a colorless,
2
2
2
[17b]
amorphous product (350 mg, 82%) was isolated, m.p. 95Ϫ96°C;
molar host/guest ratio ϭ 1:1. Ϫ IR (KBr): ν˜ ϭ 3516 cm (m, tert.
OH, weakly associated), 3348 (m, sec. OH, associated), 1680 (s),
1
7
[17c]
9
7
[(R)-1 only]. All non-H atoms were refined with anisotropic
Ϫ1
displacement parameters. Crystallographic data (excluding struc-
ture factors) for the structures reported in this paper have been
deposited with the Cambridge Crystallographic Data Centre as
supplementary publication no. CCDC-100801. Copies of the data
449 (s), 1185 (m), 1172 (m), 1062 (m), 1014 (m), 896 (m), 754 (s),
43 (s), 699 (s), 613 (s).
(R)-1 · ICH
2 2
CO H: According to procedure A, a colorless, can be obtained free of charge on application to CCDC, 12 Union
amorphous product (390 mg, 82%) was obtained, m.p. Road, Cambridge CB2 1EZ, U.K. [Fax: (internat.) ϩ44(0)1223/
1
02.5Ϫ104°C; molar host/guest ratio ϭ 1:1. Ϫ IR (KBr): ν˜ ϭ 3513
336033; e-mail: deposit@ccdc.cam.ac.uk].
Ϫ1
cm (m, tert. OH, weakly associated), 3337 (m, sec. OH, associ-
ated), 1674 (s), 1449 (m), 1284 (m), 1263 (m), 1171 (m), 1062 (m),
3 2 22 4
Crystal Structure Data of (R)-1 · CH CO H: C22H O , mol.
mass: 350.4 crystal dimensions: 0.20 ϫ 0.40 ϫ 1.00 mm, crystal
1
012 (m), 897 (w), 752 (m), 744 (s), 699 (s), 613 (m).
R)-1 · Cl CHCO H: Procedure B gave 330 mg (79%) of a color-
less, amorphous product, m.p. 91Ϫ92°C; molar host/guest ratio ϭ 938.0(3) A , ρ
system: monoclinic, space group: P2
1
(no. 4), Z ϭ 2, unit cell: a ϭ
˚
(
2
2
5.857(1), b ϭ 18.043(4), c ϭ 9.048(2) A, β ϭ 101.19(2)°, V ϭ
˚
3
Ϫ3
calcd.
ϭ 1.241 mg mm . Number of reflections meas-
Ϫ1
1
:1. Ϫ IR (KBr): ν˜ ϭ 3526 cm (m, tert. OH, weakly associated), ured: 2430 (2Θmax ϭ 55°); 2237 unique reflections, of which 1791
3
411 (m, sec. OH, associated), 1709 (s), 1449 (s), 1194 (m), 1062
with I > 2σ(I) were used for the structure solution. All H atoms
were refined freely with isotropic U. The refinement finally con-
verged at R1 ϭ 0.0374, wR2 ϭ 0.2128, 322 parameters. Residual
(m), 1015 (m), 754 (m), 741 (s), 699 (s), 613 (s).
(
R)-1 · CH CH CO H (Procedure A): The product crystallized
3
2
2
˚
Ϫ3
electron density: Ϫ0.154 < ∆ρ < 0.145 e A
.
in colorless needles; yield: 350 mg (96%), m.p. 112.5Ϫ114°C; molar
host/guest ratio ϭ 1:1. Ϫ IR (KBr): ν˜ ϭ 3497 cm (m, tert. OH,
Ϫ1
Crystal Structure Data of (S)-1 · CH NHCHO: C H NO , mol.
3
22 23
3
weakly associated), 3307 (m, sec. OH, associated), 3300 (m), 2984
mass: 349.4 crystal dimensions: 0.35 ϫ 0.60 ϫ 0.80 mm, crystal
(
7
m), 1686 (s), 1668 (s), 1450 (s), 1173 (s), 1062 (s), 1019 (s), 896 (s), system: monoclinic, space group: P2 (no. 4), Z ϭ 2, unit cell: a ϭ
1
˚
5.895(2), b ϭ 17.990(5), c ϭ 9.168(2) A, β ϭ 105.02(2)°, V ϭ
55 (s), 744 (s), 699 (s), 613 (s).
R)-1 · rac-CH CH(Cl)CO H: According to procedure A, (R)-
(290.3 mg, 1.0 mmol) and rac-CH CH(Cl)CO H (217.0 mg, 2.0
˚
3
Ϫ3
9
39.1(5) A , ρcalcd. ϭ 1.236 mg mm . Number of reflections meas-
(
3
2
ured: 2545 (2Θmax ϭ 56°); 2342 unique reflections, of which 2039
with I > 2σ(I) were used for the structure solution. All H atoms
were refined freely with isotropic U. The refinement finally con-
verged at R1 ϭ 0.0310, wR2 ϭ 0.0857, 328 parameters. Residual
1
3
2
mmol) were combined to afford 370 mg (93%) of a colorless,
amorphous product, m.p. 98.5Ϫ99.5°C; molar host/guest ratio ϭ
1
3
Ϫ1
:1. Ϫ IR (KBr): ν˜ ϭ 3504 cm (m, tert. OH, weakly associated),
404 (m, sec. OH, associated), 1699 (m), 1449 (m), 1204 (m), 1172
˚
Ϫ3
electron density: Ϫ0.130 < ∆ρ < 0.147 e A
.
(
m), 1061 (m), 1019 (m), 896 (m), 754 (m), 741 (s), 699 (s), 613 (m).
R)-1 · rac-CH CH(Br)CO H: According to procedure B, (R)-1
290.3 mg, 1.0 mmol) and rac-CH CH(Br)CO H (306.0 mg, 2.0
Ƞ
Dedicated to Professor Dietrich Mootz on the occasion of his
5th birthday.
(
3
2
6
(
3
2
[1] [1a]
F. Vögtle, Supramolekulare Chemie, 2nd ed., Teubner,
[1b]
mmol) were stirred in cyclohexane to afford a colorless, amorphous
Stuttgart, 1992. Ϫ
F. Ebmeyer, F. Vögtle in Inclusion Com-
pounds, vol. 4 (Eds.: J. L. Atwood, J. E. D. Davies, D. D.
McNicol), Oxford University Press, Oxford, 1991, pp. 263Ϫ282.
Ϫ [ G. W. Gokel, in Inclusion Compounds, vol. 4 (Eds.: J. L.
Atwood, J. E. D. Davies, D. D. McNicol), Oxford University
product; yield: 400 mg (90%), m.p. 86Ϫ87°C; molar host/guest ra-
tio ϭ 1:1. Ϫ IR (KBr): ν˜ ϭ 3491 cm (m, tert. OH, weakly associ-
ated), 3387 (m, sec. OH, associated), 1676 (s), 1449 (s), 1174 (s),
Ϫ1
1c]
[1d]
1
061 (s), 1018 (m), 897 (m), 753 (s), 740 (s), 699 (s), 613 (s).
R)-1 · PhCHϭCHCO H (Procedure A): Crystallization gave
90 mg (89%) of thin, colorless needles, m.p. 115Ϫ116.5°C; molar
Press, Oxford, 1991, pp. 283Ϫ324. Ϫ
T. W. Bell, S. K. Sahni,
in Inclusion Compounds, vol. 4 (Eds.: J. L. Atwood, J. E. D.
Davies, D. D. McNicol), Oxford University Press, Oxford, 1991,
(
2
3
pp. 325Ϫ390.
[2]
[2a]
Ϫ1
Comprehensive reviews on clathrates:
E. Weber, Top. Curr.
D. Worsch, F. Vögtle, Top. Curr.
F. Toda, Top. Curr. Chem. 1987,
host/guest ratio ϭ 1:1. Ϫ IR (KBr): ν˜ ϭ 3457 cm (m, tert. OH,
associated), 3292 (m, sec. OH, associated), 1693 (s), 1672 (s), 1628
[2b]
Chem. 1987, 140, 1Ϫ20. Ϫ
Chem. 1987, 140, 21Ϫ41. Ϫ
[2c]
(s), 1449 (s), 1284 (s), 1204 (m), 972 (m), 748 (s), 741 (s), 696 (s),
[2d]
1
40, 43Ϫ69. Ϫ
I. Goldberg, Top. Curr. Chem. 1988, 149,
[
2e]
674 (m), 612 (m).
1Ϫ44. Ϫ
E. Weber, M. Czugler, Top. Curr. Chem. 1988, 149,
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[2h]
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This happens, for example, when triphenylglycol-derived esters
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2k]
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[
[
[
[
5]
6]
7]
8]
[16]
17] [17a]
[
SHELXTL-PLUS Release 4.21/V, Siemens Analytical X-
[17b]
ray Instruments Inc., Madison, WI, USA, 1990. Ϫ
G. M.
G. M. Sheldrick, SHELXL-97, University of
Sheldrick, SHELXL-93, University of Göttingen, Germany,
[17c]
1993. Ϫ
Göttingen, Germany, 1997.
[98034]
1076
Eur. J. Org. Chem. 1998, 1071Ϫ1076