Multifold ring closing metathesis reactions in the formation of resorcin[4]arene cavitands

Article abstract of DOI:10.1039/c5ra00760g

The formation of the resorcin[4]arene cavitands using the ring closing metathesis reaction (RCM) in perallylated resorcin[4]arenes was investigated. The formation of resorcinarene cavitands offers unique molecular platforms for host-guest chemistries, sen

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Multifold Ring Closing Metathesis
Reactions in the Formation of
Resorcin[4]arene Cavitands
Cite this: DOI: 10.1039/x0xx00000x
Sumedh Parulekar, Kirankirti Muppalla, Ali Husain, and Kirpal S. Bisht*
Received 00th January 2015,
Accepted 00th January 2015
The formation of the resorcin[4]arene cavitands using the ring closing metathesis reaction (RCM) in
perallylated resorcin[4]arenes was investigated. The formation of resorcinarene cavitands offer unique
molecular platforms for host-guest chemistries, sensor development, metal complexation, as well as new
polymers and self-assembled systems, and as potential reaction sites, and novel catalytic platforms. In
this manuscript we show that the cavitand formation by the RCM reaction depends, to a large extent, on
the conformation and the substituents on the upper and lower rim of the perallylated resorcin[4]arenes.
The perallylation of the octahydorxy compounds disrupted the intramolecular hydrogen bonds causing a
dynamic shift in the conformer equilibrium.
DOI: 10.1039/x0xx00000x
www.rsc.org/
have greatly contributed to the popularity of the RCM reaction.
Consequently, it has found applicability in the synthesis of novel
Introduction
Encapsulating molecules in closed surface spherical molecules was
proposed by D. J. Cram in 1982.1 Calixꢀ and resorcin[4]arene
cavitands have since been used as precursors to carceplexes,
carcerands, hermicarcerands and for encapsulating guest molecules
and ions, largely because of their rigidity, enforced cavities and
synthetic viability. The ability of resorcin[4]arenes to act as a
platform for the synthesis of a multitude of supramolecular
structures has been of growing interest.2 Consequently,
resorcin[4]arenes and their derivatives have been used as metal
complexing agents, sensors, receptors, molecular reaction vessels
and catalytic chambers.3
The conformation of the resorcin[4]arenes can be rigidified into a
crown conformation by bridging the hydroxyl groups of the upper
rim to a cavitand structure leading up to a conformationally locked
encapsulating platform.4 The covalent linkage of the phenolic
groups on the adjacent phenyl rings is generally exploited for
synthesis of the rigid 'bowl' shaped cavity. The methylenedioxy
bridged cavitand, formed by the treatment of the octahydroxy
resorcin[4]arene with excess CH2ClBr in the presence of a base, is
the most common covalent linkage reported.2 The ethyleneꢀ,
macrocyclic hosts11 and also in the construction of supramolecular
assemblies with specific structures.12 However, the examples of
multifold metathesis reactions are still limited for their synthetic
challenges.10–12
We reported the synthesis and Xꢀray crystal structure of the first
resorcin[4]arenes cavitand by ring closing metathesis (RCM)
reaction.2a The ring closing metathesis reaction on perallylated
resorcin[4]arenes, where allyl groups on adjacent phenyl rings serve
as acyclic diene precursors for RCM, led to the formation of
ethenylenedioxyꢀbridged resorcin[4]arene cavitands (Scheme 1).2a In
this manuscript we report our finding on the multifold RCM reaction
with different groups on the upper and lower rim of the
resorcin[4]arenes to investigate the formation of the resorcin[4]arene
cavitands. Interestingly, the multifold metathesis reaction were
dependent on the conformation and the substituents on the upper and
lower rim of the resorcin[4]arene.
propyleneꢀ,
dialkylsiliconꢀ,
phosphorylꢀ,
heterophenyleneꢀ,
phosphonateꢀ and quinoxalineꢀbridged cavitands have also been
reported (Figure 1).5ꢀ8 Clearly the bridging reaction can be used to
manipulate the cavity size and hence can be used to alter the
properties of the cavitand.9
Scheme 1 Ring-Closing metathesis of allyloxy resorcin[4]arene to
bridged resorcin[4]arene cavitands.2a
Results and Discussion
Octaallyl resorcin[4]arenes precursors- Condensation of
resorcinol, 2ꢀmethyl resorcinol or 2ꢀbromo resorcinol with ethanal,
2ꢀethylbutanal, nꢀheptanal, nꢀdecanal, benzaldehyde, and 4ꢀ
bromobenzaldehyde in a refluxing 1:1 mixture of ethanol and HCl
(37% water) afforded 48ꢀ90% yield of the corresponding
octahydroxy resorcin[4]arenes, 1ꢀ14.2b Resorcin[4]arenes were
characterized from their NMR and mass spectral analysis, and
whenever possible with the data reported in the literature.4b,8
Figure 1. Bridged-resorcin[4]arenes.
Ringꢀclosing metathesis (RCM) has been rapidly established as an
efficient methodology for synthesis of medium to large ring
systems.10 Remarkable functional group tolerance, high stability, and
commercial availability of the catalyst and the operational simplicity
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Although, the resorcin[4]arenes can have four stereoisomers, improved yields. The perallylated compounds 15-28 were
1
namely, cisꢀcisꢀcis (Crown, rccc, C4v), cisꢀtransꢀtrans (chair, rctt, characterized from their Hꢀ, 13Cꢀ NMR, and mass spectral analysis.
1
C2h), cisꢀcisꢀtrans (diamond, rcct, Cs), and transꢀcisꢀtrans (saddle, In the HꢀNMR spectra, the allyl group resonances were quantified
rtct, D2d) (Figure 2),4b only two, rccc and rctt, are predominantly and the respective integrals confirmed perallylation.
formed. Compounds 1, 3, 4, 7, 9, 10, 13 and 14 were isolated as the
rccc isomers and compounds 5, 6, 11, and 12 were isolated as the
rctt isomers. The resorcin[4]arenes 2 and 8, (resulting upon
condensation of 2ꢀethylbutanal with resorcinol or methyl resorcinol)
were observed in the rcct conformation, which has only been
reported sparsely in the literature.13 The isomeric forms (rccc, rctt
and rcct) were distinguished upon comparison of their 1HꢀNMR
1
spectra.8 For example, the HꢀNMR spectrum of the rccc isomers
showed characteristic single resonance for the resorcin[4]arene
aromatic hydrogens while the rctt isomers had two resonances for
the resorcin[4]arene aromatic hydrogens. Figure 3 below shows the
Scheme 2 Perallylation of the resorcin[4]arenes.
representative spectra for compound 1, 5 and 2 which adopt the
crown, the chair and the diamond conformations, respectively.
Cram et. al.3a have previously described the conformational
dynamics of alkylated resorcin[4]arenes.
In hydroxy
resorcin[4]arenes the intramolecular hydrogen bonds rigidify the
conformer but in perallylated compounds, which lack intramolecular
hydrogen bonds, the flexibility of the skeleton increases and an
equilibrium exists between the conformers, e.g., for the C4v (crown)
and C2v (boat) symmetries, the barrier to interconversion is
reportedly 17ꢀ19 kcal/mol,3a increasing with the bulkier alkyl
substituents on the lower rim.
For example, perallylated
resorcin[4]arenes 18 preferred the boat (C2v) conformer in solution
(CDCl3); in its 1HNMR spectrum two sets of aromatic resonances at
6.5 and 7.6 ppm were observed (Figure 4). The single crystal Xꢀray
analysis showed that perallylated resorcin[4]arene 28 exists, in the
solid state, in a C2v 'boat' conformation.2a
f
a
e
c
f, f'
O
*
O
Figure 2 Stereoisomers of resorcin[4]arenes.
d
b, c, c'
d'
b
*
e
4
d
C9H19
ppm
7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0
Figure 4 Partial 1H-NMR (250 MHz, CDCl3) of compound 18.
Compound 5, 6, 11, and 12, which exist in the chair conformation
(C2h);2b upon perallylation yielded compounds 19, 20, 25 and 26,
respectively, which were analyzed from their NMR and mass
1
spectral data and their chair conformation was evident in their H
NMR spectrum where two resonances for benzylic protons were
observed in accordance with C2h symmetry. The Xꢀray crystal
structure of compound 20 confirmed its chair conformation (C2h).2a
Likewise, perallylation of the resorcin[4]arenes 2 and 8, resulted in
compounds 16 and 22, respectively which maintained the diamond,
rcct configuration.
1
The RCM reactionꢀ The RCM reactions on octaallyl
resorcin[4]arenes 15-28 were investigated using 5ꢀ10 mole % of
generationꢀI Grubb’s catalyst. The reaction was carried out under
nitrogen atmosphere in dry dichloromethane as a solvent at room
temperature. The reactions were slow and the effect of upper and
lower rim resorcin[4]arene substituents was significant on the RCM
reaction (Table 1). With progression of the RCM reaction, thin layer
chromatography (ethyl acetate and hexane, 1:4) showed the
appearance of product(s) at lower Rf value compared to the starting
perallylated resocin[4]arene. The product was separated using silica
gel column chromatography using an ethyl acetate/hexane gradient
Figure 3 H-NMR (250 MHz, DMSO-d6) spectra for conformationally
different resorcin[4]arenes 1,5 and 2.
Perallylation of the resorcin[4]arenes- The perallylation of the
octahydroxy resorcin[4]arenes was carried out to yield 20ꢀ78% of
the perallylated products (Scheme 2, Table 1). Importantly, the
perallylation in acetone or DMF with allyl bromide using potassium
carbonate as a base, under standard reflux conditions did not always
give the best yield. The allylation reaction performed in a pressure
o
vessel at increased reaction temperature (120 C) and pressure gave
2 | RSC Adv., 2015, 00, x-x
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Table 1 RCM reaction on perallylated resorcin[4]arenes.
Octahydroxy
Allyl resorcin-
arenes#
RCM product+
4-bridge 2-bridge 1-bridge
Resorcinol
Aldehydes
Resorcinarenes
Ethanal
1 (67%)
15 (70%)
38 (13%)
2ꢀEthylbutanal
Heptanal
2 (80%)
3 (88%)
16 (40%)
17 (60%)
29 (35%)
30 (59%)
2ꢀMethyl
resorcinol
Decanal
4 (85%)
5 (88%)
6 (90%)
7 (48%)
8 (57%)
9 (78%)
10 (62%)
11 (56%)
12 (67%)
13
18 (55%)
19 (48%)
20 (68%)
21 (78%)
22 (15%)
23 (22%)
24 (20%)
25 (46%)
26 (65%)
27(68%)
28(35%)
31 (61%)
39 (10%)
40 (10%)
Benzaldehyde
Bromobenzaldehyde
Ethanal
2ꢀEthylbutanal
Heptanal
Resorcinol
34 (32%)
35 (35%)
36 (22%)
Decanal
Benzaldehyde
Bromobenzaldehyde
Heptanal
37 (17%)
2ꢀBromo
32(23%)
33(32%)
resorcinol
Decanal
3 at reflux in
14
#Acetone/K2CO
a sealed tube. +Isolated yield in parenthesis.
system with increasing ethyl acetate in the eluent (6%ꢀ10%) and vinylic CH2 in the DEPT NMR and the molecular weight confirmed
1
isolated products were analyzed by Hꢀ and 13Cꢀ NMR, 2DꢀNMR the formation of the four bridged cavitand.
spectral data and mass spectrometric measurements.
Formation of the four bridge cavitand- Intramolecular ring
closing metathesis in perallylated resorcin[4]arenes 16, 17, 18, 27
and 28 at 25 oC for 96 h using 5 mol % of Grubb's catalyst led to the
product cavitands 29-33 in 35ꢀ61 % yield with all four 2ꢀbutylene
bridges formed on the upper rim (Scheme 3). Reactions repeated
with higher amount of catalyst (up to 8 mole %) did not lead to
higher product yield. In a batch addition experiment, an additional
amount (5 mol %) of catalyst was added after 48 h, but without
higher conversion. The respective four bridge cavitands 29-33 were
the only products isolated and the unreacted substrate perallylated
resorcin[4]arene 17 was recovered after column chromatography to
be reused in the reaction to increase overall yield of the cavitand.
Figure 5 1H-NMR (250 MHz, CDCl3) of compounds 32 and 18.
The compound 30 could be crystallized from a methanol and
ethyl acetate (70:30) solvent system. The crystal structure showed
the formation of all four bridges in the upper rim and confirmed the
tetrameric rigid structure with crown conformation (C4v symmetry)
and the cisꢀgeomerty of the double bond.2a The crystal structure of
compound 30 also confirmed that RCM reaction involved two allyl
groups on the adjacent phenyl rings rather than those on the same
Scheme 3 Ring closing metathesis for formation of four bridge
cavitands.
phenyl ring.2a
Molecular weight of the compound 30 was
determined to be 1032 g/mol [Observed m/z = 1033 (M+H+)] from it
APCI MS analysis.
The structure of the cavitand 29-33 was established from detailed
1
1
analysis of the Hꢀ and 13Cꢀ NMR data. In the H NMR spectrum,
the resonances for the terminal vinylic protons (CH=CH2) observed
in the 1H NMR of the starting perallylated resorcin[4]arene were
replaced by the resonance of the bridge alkene protons (HC=CH)
(Figure 5). In the 13C NMR spectrum, the resonances that appeared
at 116.0ꢀ118.0 ppm for terminal vinylic carbons (CH=CH2)
disappeared while new resonances for the formed bridge (HC=CH)
were at 125.0ꢀ130.0 ppm after ringꢀclosing metathesis. The presence
of one resonance for a set four carbons in the 13CꢀNMR spectrum
suggested a C4v symmetric crown conformation for the compounds
30-33. The mass spectrum confirmed the molecular integrity of the
Formation of the two bridge compounds- RCM reaction catalyzed
by the Grubb's generation I catalyst in compounds 23-26 led to
partially bridged products 34-37, respectively, with 17ꢀ35% yield
(Scheme 4). Even at higher concentration of the Grubb's catalyst (8ꢀ
10 mole %), formation of only two bridges was observed after 4
days of reaction monitoring. Unreacted starting compound could be
recovered during column chromatographic separation/isolation and
reused to increase the overall yield.
Compounds 23 and 24, which lack a substituent on the upper rim
led to partially bridged products 34 and 35, respectively with 32ꢀ
35% yield. The structures of compounds 34 and 35 were established
by 13Cꢀ and DEPT NMR data. The molecular weight of compound
34 was determined to be 1088 g/mol [Observed m/z = 1089 (M+H+)]
resulting cavitands.
In compound 29, the unsymmetrical
conformation was evident in the NMR and the disappearance of the
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and that of compound 35 was determined to be 1256 g/mol 26 prefer the chair conformation (C2h symmetry) in which two
[Observed m/z = 1257 (M+H+)] from APCI MS analysis.
adjacent phenyl rings have equatorial orientation and while the other
two phenyl rings have axial orientation.2a The chair conformation
(C2h symmetry) of the compounds seems to have had significant
effect on the ring closing metathesis. Although, the bowl shaped
cavitand formation has been accomplished for the compound
existing in the chair conformation by the methylenedioxy bridge,4b
the steric strain seems to have prevented the formation of a bowl
cavitand in the RCM condition investigated in here. The reactions
repeated with higher concentration of Grubb’s catalyst (10 mole %)
only resulted in the two bridge formation even after 4 days (Scheme
4). Unreacted starting compounds 25 and 26 were recovered during
column chromatographic separation/ isolation. 13C NMR data of 36
and 37 showed that bridged alkene carbons (CH=CH) appeared at
130.0 ppm. Two resonances for the aromatic carbon Ca were
observed between 95.0ꢀ100.0 ppm and those for Cd were observed
between 132.0ꢀ133.0 ppm. Unreacted vinylic carbons (ꢀCH= and
=CH2) showed resonances at 125.0 ppm and 116.0 ppm respectively.
The resonances for allylic carbon (OꢀCH2ꢀCH=) was observed
between 65.0ꢀ75.0 ppm. It was concluded that compounds 36 and
37 had two intramolecular 2ꢀbutylene bridges but in opposite rim
sides of the resorcin[4]arene cavity retaining their chair
conformation (C2v symmetry). The molecular weight of compound
36 was determined to be 1056 g/mol [Observed m/z = 1056 (M+)]
and that of compound 37 was determined to be 1368 g/mol
[Observed m/z = 1386 (M+H2O)] from MALDI MS analysis.
Scheme 4 Ring closing metathesis for formation of A,C- di-bridged
cavitands.
1
In HꢀNMR spectra of 35 (Figure 6), two different alkene proton
resonances originating from unreacted allyl groups (5.1ꢀ5.4 ppm for
the =CH2; 6.1 ppm for the =CH) and the alkene bridge (5.9 ppm for
HC=CH) were observed. The appearance of only two sets of
resonances for the alkenyl protons (unreacted and in the bridge)
suggested a twoꢀfold symmetry in compounds 34 and 35. Also, the
appearance of only one sharp resonance for the upper rim ArꢀH (Ha;
6.4 ppm) confirmed its chemical shift equivalence and the proposed
structure as 35. Similar observations could also be made in the 13C
NMR data of compound 35, in which the two sets of resonances
were observed for the alkenyl carbons (115.0 ppm for the =CH2;
133.0 ppm for the =CH from unreacted allyl group; 127.0 ppm C=C
in the bridge) further establishing a twoꢀfold symmetry in the
compounds. Thus it was concluded that the compounds 34 and 35
were A,Cꢀ diꢀbridged, i. e., two bridges formed opposite to each
Formation of one bridge compound- In allyl compounds 15, 19,
and 20 the RCM reaction led to formation of compounds 38, 39, and
40 respectively (Scheme 5) in 10ꢀ13% yield. After column
chromatography only one compound could be isolated and attempts
at increasing the product yield with higher concentration of Grubb’s
catalyst (10 mole %) and longer reaction times were unsuccessful.
5c
other on the upper rim side. Interestingly, Cram et. al. reported
that bridging reaction of an octa hydroxyl resorcinol, prepared from
condensation of resorcinol and hexanal, using CH2ClBrꢀ K2CO3ꢀ
(CH3)2SO, led to the formation of the A,Bꢀdiꢀbridged tetraol along
with other monoꢀ, triꢀ and tetraꢀbridged compounds but no A,Cꢀdiꢀ
bridged compound was reported. The A,Bꢀdi bridged, as expected
and unlike 34 and 35, showed multiple resonances for the upper and
lower rim ArꢀH owing to its asymmetry.5c
Scheme 5 Ring closing metathesis for formation of mono-bridged
cavitands.
The 1HꢀNMR spectra of the monoꢀbridged compounds 38ꢀ41
revealed the molecular structure as being highly unsymmetrical
(Figure 7). We observed four different carbon resonances for the
upper rim methyl groups on aromatic ring, and four different
resonances for each aromatic Hd proton, two in the shielding zone at
5.6 and 5.8 ppm and two in the deshielding zone at 6.3 and 6.5 ppm.
The molecular weight of the compounds also confirmed the
formation of the single bridge in compounds 38ꢀ41. Molecular
weights of the compounds 38 [Observed m/z = 893 (M+H+)], 39
[Observed m/z = 1163 (M+Na+)]; and 40 [Observed m/z = 1480
(M+Na+)] suggested the formation of a single bridge by reaction of
the two allyl groups on the adjacent phenyl rings.
Figure 6 Regions of the 1H NMRs (250 MHz, CDCl3) of A-C di-bridged
compound 35 and its precursor 24.
Perallylated compounds 25 and 26 also led to the formation of two
bridges in products 36 and 37 in 17ꢀ22% yield. Compounds 25 and
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Experimental
General information
All solvents and reagents were commercially available. Heptanal
was purified by distillation. NMR spectra were recorded on 250
MHz and 400 MHz spectrometers at 398 K. Mass spectra were
recorded in APCI mode and MALDI. Compounds 1, 3ꢀ7, 9ꢀ14, 17ꢀ
20, 27, 28, 30ꢀ33, and 41 have previously been reported in the
literature.2a, 2b, 2i, 4a, 5a
Synthesis of octahydroxy resorcin[4]arene (1-14)
Following the literature methods the hydroxy resorcin[4 arenes were
synthesized. In a typical procedure, resorcinol, 2-methylresorcinol
or 2ꢀBromo resorcinol (8 mmol) was dissolved in anhydrous ethanol
(775 mL/mol) and 37% aqueous HCl (185 mL/mol). The solution
was cooled in an ice bath and the aldehyde (8.1 mmol) was added to
above solution slowly over a period of 30 min. Then the mixture was
allowed to warm to room temperature. The reaction was then
maintained at temperature of 80oC for nearly 12 hrs after which the
1
Figure 7 Regions of the H-NMR spectra (250 MHz, CDCl3) of mono precipitate was filtered through Buchner funnel and washed several
times until it turned neutral to pH paper. It was dried and the NMR
spectrum was taken and the date was compared with that in reported
literature.
bridged compound 39 and its precursor 19.
The RCM reaction on 21 and 22 did not led to the isolation of a
wellꢀdefined product but the TLC chromatography indicated mostly
unreacted starting compound and some compound decomposition
(streak). The small alkyl subsequent on the lower rim and lack of a
substituent on the upper rim in 21 and 22, along with the
perallylation, may reduce the energy barrier to the conformer
equilibrium to an extent that the RCM reaction was not possible.
1
Compound (2): 80%; H NMR (250 MHz, DMSOꢀd6) δ 0.77 (m,
24H), 1.22 (m, 16H), 1.35 (m, 4H), 1.93 (s, 12H), 1.95 (s, 6H), 3.99
(m, 4H), 7.27 (s, 2H), 7.33 (s, 2H), 8.48 (s, 2H), 8.54 (s, 2H), 8.82
(s, 4H), 9.14 (s, 4H); 13C NMR δ in ppm 9.9, 10.9, 21.5, 22.0, 56.0,
112.3, 112.6, 123.9, 124.7, 125.1, 129.2, 149.5, 149.9, 150.5. ESIꢀ
MS (m/z): M + Na+, found 847.517. C52H72O8Na requires 847.511.
Conclusions
1
Compound (8): 57%; H NMR (250 MHz, DMSOꢀd6) δ 0.76 (m,
In this manuscript, we have investigated the formation of the
resorcin[4]arene cavitands using the ring closing metathesis reaction
(RCM) in perallylated resorcin[4]arenes. The cavitand formation by
the RCM reaction is shown to depend, to a large extent, on the
conformation and the upper and the lower rim substituents on the
resorcin[4]arenes. It was observed that allylation of the octahydorxy
compounds disrupted the intramolecular hydrogen bonds between
24H), 1.10ꢀ1.47 (m, 20H), 3.91ꢀ4.05 (m, 4H), 6.09 (s, 2H), 6.18 (s,
2H), 7.34 (s, 2H), 7.44 (s, 2H), 8.85 (s, 2H), 8.93 (s, 2H), 9.10 (s,
2H), 9.25 (s, 2H), 9.59 (s, 2H); DEPT NMR (DMSOꢀd6) δ in ppm
9.9, 10.8, 21.6, 21.9, 38.2ꢀ40.9, 56.2, 103.6ꢀ104.3, 129.3, 133.6.
ESIꢀMS (m/z): M + H+, found 769.466. C48H65O8 requires 769.467.
Synthesis of octaallyloxy resorcin[4]arene: -
adjacent phenolic hydroxyl and caused
a dynamic shift in
Method A- 1.0 g of Octahydroxy compound was dissolved in
equilibrium between the crown and boat conformers. The crown
conformation with larger alkyl substituents (pentyl, hexyl or nonyl)
on the lower rim and a methyl or bromo substituent on the upper rim
were a prerequisite for formation of the tetra bridged bowl shaped
cavitand, e.g. 29ꢀ33. In compounds with hydrogen (no CH3 or Br)
on the upper rim but with longer alkyl chains on the lower rim
(hexyl and nonyl) it was observed that only diꢀbridged compounds
could be formed, e.g., 34 and 35. For resorcin[4]arenes with lower
rim aromatic substituents, which exist in the chair (C2h)
conformation, the crown conformers are energetically much less
favored because of the repulsion between equatorial aryl ring and the
allyloxy groups. The RCM reaction in the perallyalated chairꢀ
resorcin[4]arenes with hydrogen on the upper rim resulted in the
ACꢀdiꢀbridged resorcin[4]arenes 36 and 37, while a CH3 on the
upper rim only resulted in a monoꢀbridged resorcin[4]arenes, i.e., 39
and 41. Though tetraꢀbridged cavitand formation has been reported
in chairꢀresorcin[4]arenes, most probably a result of ringꢀinversion
to the corresponding cone conformation which is stabilized by the
intramolecular hydrogen bonds,4b but such ring inversion in
perallyated chairꢀresorcin[4]arenes is not possible due the size of the
allyoxy group. For perallyated compounds with CH3 group on the
lower rim the dynamic equilibrium between the conformers appear
to quite rapid in the solution and only mono bridged compound (38)
could be synthesized when the upper rim had a methyl subsequent;
with a hydrogen on the upper rim, i.e., 21 and 22, no wellꢀdefined
RCM product could be isolated.
acetone (20 ml/mol) in a roundꢀbottomed flask. The reaction
mixture was cooled to 0 C in an ice bath and potassium carbonate
o
(30eq) was slowly added over a period of half an hour during which
the solution changed color to purple. Then the reaction mixture was
brought to room temperature and allyl bromide (30eq) was added.
The reaction mixture was refluxed and monitored using TLC. Upon
completion, the reaction mixture was filtered and the filtrate was
concentrated in vacuo to yield the crude product. Recrystallization
from a mixture of acetone and methanol (50:50) resulted in the pure
perallylated product.
Method B- 1.0 g of Octahydroxy compound was taken into high
pressure reaction tube and dissolved in acetone (20 ml/mol). Then
potassium carbonate (30eq) was added to the reaction tube; the
solution color changed to purple and then allyl bromide (30eq) was
added and the reaction tube was sealed with a threaded Teflon plug.
The high pressure reaction tube was then heated to temperature of
80oC in an oil bath for 24ꢀ48 hrs. Upon completion, the reaction
mixture was filtered and the filtrate was concentrated in vacuo to
yield the crude product. Recrystallization from a mixture of acetone
and methanol (50:50) resulted in the pure perallylated product.
1
Compound (15): 60%; H NMR (250 MHz, CDCl3) δ 1.45 (t, 12H,
J = 6.6 Hz), 1.85 (bs, 6H), 2.24 (bs, 6H), 3.41 (bs, 8H), 3.82 (bs,
8H), 4.44 (bs, 4H), 4.46ꢀ4.51 (m, 8H), 5.01ꢀ5.18 (m, 8H), 5.48 (s,
2H), 6.07 (s, 2H); 13C NMR (CDCl3) δ in ppm 10.5, 20.9, 32.8, 73.2,
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VJieowuArrtnicalelONnlainme e
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DOI: 10.1039/C5RA00760G
90.5, 116.12, 123.6, 133.0, 134.5, 155.0. ESIꢀMS (m/z): M + Na+, crude product was column chromatographed over silica gel using
found 943, C60H72O8Na requires 943.
ethyl acetate : hexane (1:9) eluent.
Compound (16): 40%; 1H NMR (250 MHz, CDCl3) δ 0.21 (t, 6H, J
= 6.6 Hz), 0.58ꢀ0.89 (m, 24H), 1.09ꢀ1.74 (m, 14H), 2.13 (s, 6H),
2.20 (s, 6H), 3.62ꢀ3.69 (m, 2H), 3.96ꢀ4.03 (m, 2H), 4.10ꢀ4.33 (m,
6H), 4.38ꢀ4.56 (m, 5H), 4.67ꢀ4.72 (m, 4H), 4.97ꢀ5.55 (m, 18H),
5.85ꢀ6.29 (m, 8H), 6.72 (s, 2H), 7.85 (s, 2H). 13C NMR δ in ppm
10.4, 11.2, 11.3, 12.7, 22.3, 23.5, 24.3, 36.5, 37.4, 40.3, 45.1, 48.3,
73.1, 73.5, 116.3, 116.5, 116.6, 116.8, 125.9, 127.4, 125.9, 127.4,
134.4, 134.8, 135.1, 135.2. ESIꢀMS (m/z): M + H+, found 1145.779.
C76H105O8 requires 1145.
Compound (29): 35%; 1H NMR (400 MHz, CDCl3) δ 0.06 (t, 6H, J
= 7.3 Hz), 0.68 (m, 18H), 0.94 (t, 6H, J = 7.5 Hz), 1.25ꢀ1.31 (m,
10H), 1.47 ꢀ1.74 (m, 4H), 2.20 (s, 6H), 2.28 (s, 6H), 4.08ꢀ4.16 (m,
4H), 4.37ꢀ4.48 (m, 4H), 4.54ꢀ4.57 (m, 4H), 4.70ꢀ4.86 (m, 6H), 5.24
(t, 2H, J = 8.4 Hz), 5.63ꢀ5.73 (m, 2H), 5.92ꢀ6.21 (m, 7H), 7.00 (s,
2H), 8.02 (s, 2H) ; 13C NMR (CDCl3) δ in ppm 8.8, 8.9, 9.2, 10.4,
10.5, 10.6, 10.7, 20.3, 20.8, 21.2, 21.9, 22.2, 36.4, 40.3, 42.2, 43.5,
48.6, 50.5, 67.2, 67.3, 67.9, 72.3, 122.5, 122.6, 122.7, 124.4, 126.6,
129.9, 130.0, 131.0, 131.4, 132.0, 131.1, 132.6, 153.6, 153.8, 154.1,
154.6, 155.0; ESIꢀMS (m/z): M + H+, found 1033, C68H89O8 requires
1033.
Compound (21): 78%; 1H NMR (250 MHz, CDCl3) δ 0.89ꢀ1.57 (m,
44H), 2.16 (s, 6H), 2.67 (s, 6H), 3.11ꢀ4.86 (m, 20H), 4.89ꢀ5.51 (m,
16H), 5.72ꢀ6.64 (m, 8H), 6.98 (s, 4H); DEPT NMR (CDCl3) δ in
ppm 20.9, 32.8, 73.2, 116.1, 123.7, 134.5.
1
Compound (34): 32%; H NMR (250 MHz, CDCl3) δ 0.77 (t, 12H,
J = 6.2 Hz), 1.13ꢀ1.73 (m, 32H), 1.85 (m, 8H), 4.25 (m, 16H), 4.55
(d, 2H, J = 2.5 Hz), 4.62 (s, 2H), 5.18 (dd, 4H, J = 1.2 Hz, J = 10.5
Hz), 5.41 (dd, 4H, J = 1.5 Hz, J = 17.5 Hz), 5.86 (s, 2H), 5.93 (s,
2H), 6.12 (m, 4H), 6.45 (s, 4H), 7.12 (s, 4H); 13C NMR (CDCl3) δ in
ppm 13.0, 21.7, 27.2, 28.7, 30.9, 33.4, 34.5, 63.6, 68.9, 96.8, 98.2,
115.3, 122.3, 125.3, 125.6, 127.0, 128.2, 133.3, 152.0, 153.1; ESIꢀ
MS (m/z): M + H+, found 1090, C72H97O8 requires 1089.
Compound (22): 15%; 1H NMR (250 MHz, CDCl3) δ 0.77 (m,
24H), 1.12ꢀ1.61 (m, 16H), 1.88ꢀ2.37 (m, 4H), 4.22ꢀ4.54 (m, 19H),
5.06ꢀ5.47 (m, 16H), 5.84ꢀ6.18 (m, 8H), 6.20ꢀ6.39 (m, 5H), 7.01ꢀ7.28
(m, 4H); 13C NMR (CDCl3) δ in ppm 9.0ꢀ11.0, 44.1, 44.6, 68.8ꢀ69.9,
73.9, 98.1ꢀ99.7, 101.2ꢀ101.4, 115.9ꢀ117.8, 127.8, 129.8ꢀ130.8,
134.0ꢀ135.7. ESIꢀMS (m/z): M + H+, found 1089. C72H97O8 requires
1089.
1
Compound (35): 35%; H NMR (250 MHz, CDCl3) δ 0.79 (t, 12H,
1
J = 6.2 Hz), 1.12ꢀ1.75 (m, 56H), 1.98 (m, 8H), 4.34 (m, 16H), 4.68
(s, 2H), 4.77 (s, 2H), 5.19 (dd, 4H, J = 1.2 Hz, J = 10.2 Hz), 5.43
(dd, 4H, J = 1.5 Hz, J = 17.0 Hz), 5.88 (s, 2H), 5.95 (s, 2H), 6.11 (m,
4H), 6.45 (s, 4H), 7.12 (s, 4H); 13C NMR (CDCl3) δ in ppm 13.0,
21.6, 27.2, 28.3, 28.7, 29.0, 30.9, 33.4, 34.4, 34.5, 63.5, 68.9, 96.8,
98.1, 115.3, 122.7, 125.3, 125.6, 127.0, 128.7, 133.3, 152.0, 153.2;
ESIꢀMS (m/z): M + H+, found 1257, C84H121O8 requires 1257.
Compound (23): 22%; H NMR (250 MHz, CDCl3) δ 0.73 (t, 12H,
J = 7.2 Hz), 1.12ꢀ1.23 (m, 32H,), 1.72 (m, 8H), 4.11 (d, 8H, J = 12.0
Hz), 4.28 (d, 8H, J = 12.0 Hz), 4.51 (t, 4H, J = 4.0 Hz), 5.11 (d, 8H,
J = 8.0 Hz), 5.29 (d, 8H, J = 16.0 Hz), 5.82 (m, 8H), 6.11 (s, 4H,),
6.52 (s, 4H); 13C NMR δ in ppm 14.1, 22.8, 28.3, 29.7, 31.9, 34.7,
35.8, 69.6, 99.3, 116.1, 125.9, 126.8, 134.1, 154.8. ESIꢀMS (m/z): M
+ H+, found 1145. C76H105O8 requires 1145.
1
Compound (24): 20%; H NMR (250 MHz, CDCl3) δ 0.89 (t, 12H, Compound (36): 22%; HꢀNMR (250 MHz, CDCl3) δ in ppm 4.22ꢀ
J = 7.2 Hz), 1.26ꢀ1.31 (m, 56H), 1.85 (m, 8H), 4.13 (d, 8H, J = 12.0 4.62 (m, 16H), 5.04ꢀ5.20 (m, 12H), 5.72ꢀ5.91 (m, 10H), 6.16ꢀ6.25
Hz), 4.31 (d, 8H, J = 12.0 Hz), 4.59 (t, 4H, J = 4.0 Hz), 5.13 (d, 8H,
J = 8.0 Hz), 5.31 (d, 8H, J = 16.0 Hz), 5.94 (m, 8H), 6.35 (s, 4H),
6.65 (s, 4H); 13C NMR δ in ppm 14.1, 22.9, 28.3, 29.4, 29.8, 30.1,
31.9, 34.7, 35.7, 36.8, 69.6, 99.3, 116.1, 126.3, 126.8, 134.1, 154.7.
ESIꢀMS (m/z): M + Na+, found 1335, C88H128O8Na requires 1335.
(m, 4H), 6.44 (s, 2H), 6.83ꢀ7.03 (m, 22H); CꢀNMR (CDCl3) δ in
ppm 41.8, 63.8, 68.6, 96.2, 101.2, 115.3, 124.4ꢀ125.9, 126.8, 127.3,
127.9, 128.1, 132.1, 132.7, 140.9, 141.7, 143.1, 143.9, 151.8, 154.4;
DEPT NMR (CDCl3) δ in ppm 41.8, 63.8, 68.6, 96.2, 98.9, 115.3,
124.3, 126.6, 126.8, 127.3, 127.9, 128.1, 132.1, 132.7, 140.9, 141.7,
151.8, 154.4; ESIꢀMS (m/z): M + H+, found 1057, C72H65O8 requires
1057.
Compound (25): 46%; 1H NMR (250 MHz, CDCl3) δ 3.81ꢀ4.33 (m,
16H), 4.95ꢀ5.20 (m, 16H), 5.53ꢀ5.76 (m, 8H), 5.76ꢀ5.81 (m, 4H),
5.91 (m, 4H), 6.13ꢀ6.17 (d, 2H, J = 9.6 Hz), 6.30 (s, 2H), 6.73ꢀ6.77
(m, 16H), 6.89ꢀ6.96 (m, 4H); 13C NMR (CDCl3) δ in ppm 69.5,
116.2, 125.3, 125.6, 127.7, 128.9, 133.9, 143.5, 155.6. ESIꢀMS
(m/z): M + H+, found 1113, C76H73O8 requires 1113.
Compound (37): 17%; 1H NMR (400 MHz, CDCl3) δ 4.19ꢀ4.71 (m,
16H), 4.87ꢀ5.31 (m, 8H), 5.53ꢀ5.84 (m, 6H), 5.98ꢀ6.24 (m, 4H), 6.39
(s, 2H), 6.52ꢀ6.71 (m, 8H), 7.21ꢀ7.56 (m, 16H). DEPT NMR
(CDCl3) δ in ppm 41.2, 63.8, 68.3, 96.4, 98.1, 115.5, 123.3, 123.5,
127.2, 127.3, 129.7, 130.2, 131.5, 132.4, 140.9, 141.7, 151.8, 154.4;
ESIꢀMS (m/z): M+ + H2O, found 1385 (100%), 1386 (80 %),
C72H62Br4O9 requires 1386.
Compound (26): 65%; 1H NMR (250 MHz, CDCl3) δ 3.32ꢀ4.62 (m,
16H), 4.99ꢀ5.33 (m, 16H), 5.62ꢀ5.93 (m, 8H), 6.11ꢀ6.23 (m, 4H),
6.29ꢀ6.36 (m, 4H), 6.45ꢀ6.62 (m, 8H), 6.64ꢀ6.73 (m, 4H) 7.10ꢀ7.31
(d, 8H, J=7.0Hz); DEPT NMR (CDCl3) δ 42.7, 69.0, 69.3, 69.6,
116.5, 130.5, 130.7, 132.9, 133.3, 133.5. ESIꢀMS (m/z): M + H+,
found 1425, C76H69Br4O8 requires 1425.
Compound (38): 13%; 1H NMR (400 MHz, CDCl3) δ 0.89 (t, 3H, J
= 6.6 Hz), 1.26ꢀ1.37 (m, 9H), 1.78ꢀ2.38 (m, 12), 4.16 (m, 2H), 4.22ꢀ
4.64 (m, 16H), 4.82 (m, 2H), 4.99ꢀ5.34 (m, 12H), 5.62ꢀ6.21 (m, 8H);
13C NMR (CDCl3) δ 10.2, 20.2ꢀ23.8, 29.8, 32.1, 69.2, 69.9, 71.8,
72.4, 115.9ꢀ116.4, 122.0,ꢀ126.0, 130.1, 132.2, 134.4, 136.2; MALDI
m/z 893 (M+H+), C58H69O8 requires 893.
Ring closing metathesis reaction synthesis of bridged-
resorcin[4]arene:- To
a
stirred solution of octaallyloxy
resorcin[4]arene (1.0 g, 1.086 mmole) in dry methylene chloride
(114 ml) was added Grubb’s catalyst (8 mole%, 0.071 gm, 0.087
mmol) in dry methylene chloride (25ml) at room temperature. The
reaction mixture was stirred and monitored by TLC. When no
increase in the amount of the product was observed over 8 hrs, the
reaction mixture was concentrated in vacuo to remove solvent. The
Compound (39): 10%; 1H NMR (250 MHz, CDCl3) δ 2.12 (s, 3H),
2.15 (s, 3H), 2.29 (s, 6H), 3.80ꢀ3.96 (m, 6H), 4.10ꢀ4.28 (m, 6H),
4.49ꢀ4.65 (m, 4H), 5.08ꢀ5.26 (m, 12H), 5.62 (s, 1H), 5.81 (s, 1H),
5.83ꢀ5.99 (m, 8H), 6.05 (s, 1H), 6.15 (s, 1H), 6.26 (s, 1H), 6.48 (s,
1H), 6.50ꢀ6.57 (m, 3H), 6.63ꢀ6.68 (m, 4H), 6.80ꢀ6.93 (m, 12); 13C
NMR (CDCl3) δ in ppm 10.8, 10.9, 24.9, 36.8, 44.7, 44.9, 73.3, 73.4,
6 | RSC Adv., 2015, 00, x-x
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DOI: 10.1039/C5RA00760G
73.7, 73.9, 116.4, 116.6, 116.8, 117.0, 123.8, 124.1, 125.3, 125.8,
125.9, 126.3, 127.4, 127.8, 128.3, 129.0, 129.2, 130.1, 131.2, 132.7,
132.8, 133.1, 133.2, 134.1, 134.2, 134.3, 134.4, 141.4, 143.6, 154.3,
154.8, 154.9, 155.0. ESIꢀMS (m/z): M + Na+, found 1163.
C78H76O8Na requires 1163.
1988, 110, 2229ꢀ2237. (b) P. Timmerman, H. Boerrigter, W.
Verboom, G. J. Van Hummel, S. Harkema, D. N. Reinhoudt, J.
Inclusion Phenom. 1995, 18, 1. (c) D. J. Cram, L. M. Tunstad, C.
B. Knobler, J. Org. Chem. 1992, 57, 528. (d) T. N. Sorrell, F. C.
Pigge, J. Org. Chem. 1993, 58, 784ꢀ785.
6. (a) D. J. Cram, K. D. Stewart, I. Goldberg, K. N. Trueblood, J.
Am. Chem. Soc. 1985, 107, 2574. (b) J.A. Tucker, C.B. Knobler,
K. N. Trueblood, D. J. Cram, J. Am. Chem. Soc. 1989, 111,
3688ꢀ3699.
7. (a) W. Xu, J. V. Jadagese, R. J. Puddephatt, J. Am. Chem. Soc.
1993, 115, 6456. (b) W. Xu, J. J. Vittal, R. J. Puddephatt, J. Am.
Chem. Soc. 1995, 117, 8362ꢀ8371. (c) T. Lippmann, H. Wilde,
E. Dalcanale, L. Minlla, G. Mann, U. Heyer, S. Spera, J. Org.
Chem. 1995, 60, 235.
8. (a) D. J. Cram, H. J. Choi, J. A. Bryant, C. B. Knobler, J. Am.
Chem. Soc. 1992, 114, 7748. (b) M. Vincenti, E. Dalcanale, P.
Soncini, G. Guglielmetti, J. Am. Chem. Soc. 1990, 112, 445ꢀ447.
(c) J. R. Moran, J. L. Ericson, E. Dalcanale, J. A. Bryant, C. B.
Knobler, D. J. Cram, J. Am. Chem. Soc. 1991, 113, 5707ꢀ 5714.
(d) J. A. Bryant, J. L. Ericson, D. J. Cram, J. Am. Chem. Soc.
Compound (40): 10%; 1H NMR (250 MHz, CDCl3) δ 2.16 (s, 6H),
2.27 (s, 6H), 3.81ꢀ3.97 (m, 6H), 4.08ꢀ4.34 (m, 6H), 4.40ꢀ4.65 (m,
4H), 5.10ꢀ5.29 (m, 12H), 5.52 (s, 1H), 5.67 (s, 1H), 5.79 (s, 1H),
5.82ꢀ5.96 (m, 6H), 6.00 (s, 1H), 6.09 (s, 1H), 6.12 (s, 1H), 6.37ꢀ6.53
(m, 8H), 7.04ꢀ7.13 (m, 8H); 13C NMR (CDCl3) δ in ppm 10.9, 11.0,
14.4, 29.9, 43.7, 44.3, 70.8, 73.5, 73.8, 74.5, 110.0, 116.6, 116.8,
117.3, 117.8, 120.0, 120.1, 124.3, 125.8, 126.4, 128.2, 130.6, 130.9,
131.4, 132.1, 132.4, 132.5, 133.8, 134.0, 140.5, 142.9, 143.6, 154.3,
154.8, 155.0, 155.4. ESIꢀMS (m/z): M + Na+, found 1479 (100%)
1480 (80%). C78H72Br4O8Na requires 1480.
Acknowledgements
Financial support for this work from the Herman Frasch Foundation,
and the USF internal awards is greatly appreciated.
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Notes and references
a
Department of Chemistry, University of South Florida, 4202 East
Fowler Avenue, Tampa, FL 33620, USA. *Corresponding author. eꢀmail
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DOI: 10.1039/C5RA00760G
Multifold Ring Closing Metathesis Reactions in the Formation of Resorcin[4]arene
Cavitands.
Sumedh Parulekar, Kirankirti Muppalla, Ali Husain, and Kirpal S. Bisht.
The formation of the resorcin[4]arene cavitands by the ring closing metathesis (RCM) reaction
depends, to a large extent, on the conformation and the substituents on the upper and lower rim
of the perallylated resorcin[4]arenes.