[closo-1-CB11H11-1-Ph]- as a structural element for ionic liquid

Article abstract of DOI:10.1016/j.jorganchem.2013.05.034

Ion pairs 2[Pyr] and 3[Pyr] containing [closo-1-CB₁₁H ₁₁-1-Ph]^- as the structural element were synthesized and their liquid crystalline properties were investigated by thermal and optical methods. Their mesogenic behavior was compared to that of the analogous series 1[Pyr] having a COO linking group between the benzene ring and the cluster, and the observed structure-property relationships are discussed in the context of general trends in related non-ionic liquid crystals.

Full text of DOI:10.1016/j.jorganchem.2013.05.034

Journal of Organometallic Chemistry 747 (2013) 195e200
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Journal of Organometallic Chemistry
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[closo-1-CB11H11-1-Ph]ꢀ as a structural element for ionic liquid
crystals
,
,
c
,
b
Aleksandra Jankowiak a, Junichiro Kanazawa a b, Piotr Kaszynski a , Ryo Takita ,
*
Masanobu Uchiyama b
a Organic Materials Research Group, Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
b Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
c
ꢀ
ꢀ
Section of Heteroorganic Compounds, University of Łódz, Tamka 12, 91403 Łódz, Poland
a r t i c l e i n f o
a b s t r a c t
Ion pairs 2[Pyr] and 3[Pyr] containing [closo-1-CB11H11-1-Ph]ꢀ as the structural element were synthe-
sized and their liquid crystalline properties were investigated by thermal and optical methods. Their
mesogenic behavior was compared to that of the analogous series 1[Pyr] having a COO linking group
between the benzene ring and the cluster, and the observed structureeproperty relationships are dis-
cussed in the context of general trends in related non-ionic liquid crystals.
Article history:
Received 20 March 2013
Received in revised form
23 May 2013
Accepted 24 May 2013
Ó 2013 Elsevier B.V. All rights reserved.
Dedicated to Professor Vladimir Bregadze
on the occasion of his 75th birthday.
Keywords:
Boron clusters
Ion pairs
Liquid crystals
Structureeproperty relationship
1. Introduction
as 2[Pyr] and 3[Pyr], including those lacking the ester group and,
consequently, with increased chemical stability. The first two
A recꢀently developed method for C-arylation of the [closo-1-
members of this new family of ILC, 2c[Pyr] and 2f[Pyr], were re-
ported recently [1].
CB11H12
] cluster [1] has opened up possibilities for synthesis of
new materials with improved properties. One such class of mate-
rials are ionic liquid crystals (ILC), in which the mesogenic prop-
erties are driven by the anisometric anion. These compounds are
capable of anisotropic cation transport [2e6] and are of interest for
Here we describe the synthesis and characterization of meso-
genic ion pairs 2[Pyr], derived from the [closo-1-CB11H11-1-Ph]ꢀ,
with the C6H13 chain and one derivative 3c[Pyr] with double length
of the alkyl chain. Properties of the new compounds are compared
to those of series 1[Pyr] and are used for structureeproperty
relationship analysis.
ion batteries [7] and solar cell applications [8]. In this context we
ꢀ
have demonstrated that closo-carbaborates [closo-1-CB9H10
]
(A,
ꢀ
Fig. 1) and [closo-1-CB11H12
]
(B) are suitable structural elements
for ILC, such as IA and IB in Fig. 1 [9e11], and ion pairs 1[Pyr]
containing [closo-1-CB11H12
]
ꢀ (B), exhibit SmA and nematic phases
[11]. The new synthetic method [1] opens access to C-aryl de-
rivatives of cluster B and enables synthesis of new series of ILC such
* Corresponding author. Organic Materials Research Group, Department of
Chemistry, Vanderbilt University, Box 1822 Station B, Nashville, TN 37235, USA.
Tel.: þ1 615 322 3458; fax: þ1 615 343 1234.
E-mail addresses: aleksandra.jankowiak@Vanderbilt.Edu (A. Jankowiak),
1727407712@mail.ecc.u-tokyo.ac.jp (J. Kanazawa), piotr.kaszynski@vanderbilt.edu
(P. Kaszynski), takita@mol.f.u-tokyo.ac.jp (R. Takita), uchiyama@mol.f.u-tokyo.ac.jp
(M. Uchiyama).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.05.034

196
A. Jankowiak et al. / Journal of Organometallic Chemistry 747 (2013) 195e200
ꢀ
ꢀ
Fig. 1. The structures of the [closo-1-CB9H10
]
(A) and [closo-1-CB11H12
]
(B) clusters,
Scheme 1. Reagents and conditions: i) (COCl)2, cat. DMF, CH2Cl2; ii) ROH 7, Pyr, CH2Cl2,
rt; iii) ROH 8, Pyr, 90 ꢁC, 2 d.
and ion pairs of their 1,10- (IA) and 1,12-disubstituted (IB) derivatives with the
counterion Qþ. Each vertex represents a BH fragment and the sphere is a carbon atom.
2. Results and discussion
2.1. Synthesis
Esters 1b, 1d, 2b, 2c, and 3c were prepared from appropriate
carboxylic acids 4[NEt4]e6[NEt4]. Thus, carboxylic acids were
converted to acid chlorides with (COCl)2 and treated with appro-
priate phenol 7 or trans-4-pentylcyclohexanol [12] (8) to give
desired esters as the [NEt4]þ salts (Scheme 1). The reaction with the
cyclohexanol was conducted with five-fold excess alcohol, and at
high concentration and temperature to assure formation of the es-
ters. Esters 2d[NMe4] and 2e[NMe4] were obtained by esterification
of phenol 9[NMe4] with 4-pentylbenzoyl chloride and trans-4-
pentylcyclohexanecarbonyl chloride, respectively (Scheme 2).
Finally, alkylation of phenol 9[NMe4] with tosylate 10 [13] in DMF in
the presence of K2CO3 resulted in derivative 2f[NMe4] isolated in
76% yield. The ion pairs 1[Pyr]e3[Pyr] were prepared by exchange
of the [NEt4]þ or [NMe4]þ cation for N-butyl-4-heptyloxypyridinium
[9,14] (Pyr) in a biphasic CH2Cl2/H2O system following the proce-
dure previously reported for the preparation of ion pair 1a[Pyr] [11].
Carboxylic acid 6[NEt4] was obtained by Negishi coupling [15,16]
of iodo acid [closo-1-CB11H10-1-(4-C6H4COOH)-12-I]ꢀ [NMe4]þ (11
[NMe4]) [1] with 12-fold excess dodecylzinc chloride in the pres-
ence of Pd(0) and PCy3 ligand generated in-situ (Scheme 3), as
Scheme 2. Reagents and conditions: i) C5H11-A-COCl, Pyr, CH2Cl2; ii) C5H11-Chx-
CH2OTs (10), K2CO3, DMF.
microdroplet (Fig. 2b), while the second phase was detected in
some DSC scans (Fig. 3b). Nematic phase is rarely observed in ILC
and ion pair 1b[Pyr] represent the second example of a nematic ILC
found among boron cluster derivatives [11].
Analysis of data in Table 1 demonstrates that moving the car-
boxylic group from the {closo-CB11} cluster in 1a[Pyr] tothe benzene
ring lowers the melting point by 70 K in 2c[Pyr]. Inversion of the
direction of the carboxyl group in 2c[Pyr] significantly increases
stability of the SmA by 47 K in 2e[Pyr]. In contrast, the same change
of the COO group orientation in the benzene analogues 2b[Pyr] and
2d[Pyr] and also in 1b[Pyr] and 1d[Pyr] results in a much smaller
increase of mesophase stability by 8 K and 22 K, respectively.
Replacement of the COO group in 2e[Pyr] with the CH2O group
in 2f[Pyr] has little effect on the phase stability but significantly
lowers the melting point by 31 K.
Compounds with the cyclohexyl ring appear to exhibit more
stable SmA phase than their benzene analogues. Thus, replacement
of the benzene ring with the cyclohexyl ring moderately increases
the SmA-I transition in the pair 2b[Pyr] and 2c[Pyr], while the
same replacement in pairs 1d[Pyr] and 1e[Pyr], and 2d[Pyr] and 2e
[Pyr] stabilizes the SmA phase by 46 K and 57 K, respectively.
A comparison of the clearing temperatures Tc in series 1[Pyr]
and 2[Pyr] shows that insertion of a COO group between the {closo-
1-CB11} and Ph groups increases stability of the mesophase by an
described previously for the preparation of acids [closo-1-CB11H10
1-COOH-12-C6H13
ꢀ [NMe4]þ (4[NMe4]) [11] and [closo-1-CB11H10
1-(4-C6H4COOH)-12-C6H13
-
-
]
]
ꢀ [NEt4]þ (5[NEt4]) [1]. A similar Negishi
coupling of iodo phenol [closo-1-CB11H10-1-(4-C6H4OH)-12-I]ꢀ
[NMe4]þ (12[NMe4]) gave the hexyl phenol 9[NMe4] [1].
Preparation of iodo acid 11[NMe4] and iodo phenol 12[NMe4] is
described elsewhere [1] and involves arylation of [closo-1-CB11H11
-
12-I]ꢀ [NMe4]þ (13[NMe4]) with substituted iodobenzene through
a carboranylcopper reagent, followed by deprotection of acid or
phenol functionality (Scheme 3).
Phenol 7c (Scheme 1) was obtained according to a literature
procedure [17], while synthesis of 7b was reported before [18].
2.2. Liquid crystalline properties
Transition temperatures for compounds 1[Pyr] and 2[Pyr] are
shown in Table 1. Phase structures were assigned by comparison of
POM results with published textures for reference compounds [19].
Compounds in series 2[Pyr] and 3c[Pyr] exhibit a SmA phase
identified by the characteristic textures observed in polarized light
(Fig. 2a). In ester 2e[Pyr] and ether 2f[Pyr] the smectic phase is
enantiotropic with a tendency for supercooling (Fig. 3a), while in
the remaining esters the SmA phase is monotropic appearing as
much as 26 K below melting for ester 2d[Pyr] (Table 1). Compounds
in series 1[Pyr], including the newly synthesized phenyl benzoates
1b[Pyr] and 1d[Pyr], exhibit similar phase behavior. Surprisingly,
ester 1b[Pyr] also displays a nematic phase above presumably a
SmA phase. The former phase was observed in a supercooled
Scheme 3. Reagents and conditions: i) BuLi, THF; ii) CuI; iii) I-C6H4-X0, Pd(OAc)2, (o-
MeOC6H4)3P; iv) deprotection X0 / X; v) CnH2nþ1ZnCl, Pd2(dba)3, [HPCy3]þ[BF4]ꢀ, THF.

A. Jankowiak et al. / Journal of Organometallic Chemistry 747 (2013) 195e200
197
Table 1
cyclohexanol or replacement of the ArOCH2 group with a ArOOC
group in cyclohexane derivatives 14d and 14e, significantly increases
the N phase stability by about 40 K. Similarly, in isostructural ana-
logues of p-carborane 15, that are closely related to 2d and 2e, the
cyclohexyl derivative 15a exhibits higher stability of the nematic
phase by 16 K than its benzene analogue 15b (Fig. 6) [21]. Finally,
inserting a COO group between 4-pentylbicyclo[2.2.2]octane group
and benzene ring in 14f increases the mesophase stability by 21 ꢂ8 K,
which is nearly identical to that observed for three pairs 1[Pyr]/2
[Pyr].
Transition temperatures (ꢁC) and enthalpies (kJ/mol, in parentheses) for 1[Pyr] and
2[Pyr].a
3. Summary and conclusions
L
A
1[Pyr]
2[Pyr]
We have demonstrated that [closo-1-CB11H11-1-Ph]ꢀ group is a
viable structural element of ionic liquid crystals. The removal of the
esters linking group between the cluster and the benzene ring in
series 1[Pyr] destabilizes the mesophase by about 20 K, but leads to
more chemically stable derivatives, such as 2f[Pyr] that are resis-
tant to hydrolytic conditions. Increasing the length of the chain has
a favorable effect on phase stability and range, which is important
for further optimization of properties.
Structureeproperty relationships observed in series 1[Pyr] and
2[Pyr] follow those established for non-ionic liquid crystals, which
provides good design tool for new mesogens with desired
properties.
e
a
b
c
Chx
Cr1 162 Cr2 178 Ib
NA
(9.8)
(24.3)
eCOOe
eOOCe
Ben
Chx
Cr 104 (SmX 87 N 93)c,d I
Cr 92 (SmA 75)c
(59.6) (1.0)
I
(64.4)
NA
(0.7) (1.7)
Cr 108 (SmA 92)c Ie
(45.4)
(3.9)
d
e
f
Ben
Chx
Chx
Cr 125 (SmA 115)c,f
(44.7)
I
Cr 109 (SmA 83)c
(72.7) (3.6)
Cr 136 SmA 139 I
(56.9)g
I
Cr1 109 Cr2 119 SmA 161 Ib
(7.7) (14.9) (6.2)
NA
eOCH2e
Cr 105 SmA 141 Ie
(40.9)
(7.7)
a
Transition temperatures obtained on heating.
Ref. [11].
Monotropic transition.
Obtained on cooling.
Ref. [1].
b
c
d
e
f
4. Experimental section
Optical determination.
Combined enthalpy.
4.1. General procedures
g
NMR spectra were obtained at 400 MHz (1H) and 128 MHz (11B)
1H,
average of 22 K with the smallest effect for the 1b[Pyr]/2b[Pyr] pair
in CD3CN. Chemical shifts were referenced to the solvent (
d
1.93 ppm) or to an external sample of B(OH)3 in MeOH (
d
11B,
(
D
Tc
¼
18 K) and the largest for the 1d[Pyr]/2d[Pyr] pair
(D
Tc ¼ 32 K).
18.1 ppm). Mass spectrometry was acquired in the ESI mode. Optical
microscopy and phase identification was performed using a PZO
“Biolar” polarized microscope equipped with a HCS250 Instec hot
stage. Thermal analysis was obtained using a TA Instruments 2920
DSC. Transition temperatures (onset) and enthalpies were obtained
using small samples (0.3e1 mg) and a heating rate of 5 K minꢀ1
under a flow of nitrogen gas. For DSC and combustion analyses, each
compound was additionally purified by filtering solutions in CH2Cl2
to remove particles, followed by recrystallization from appropriate
solvent until constant transition temperatures. The resulting crys-
tals were dried in vacuum at ambient temperature.
Increasing the chain length has a desired effect on thermal prop-
erties of the ILC: it lowers the melting point by 37 K and increases
stability of the SmA phase by 45 K leading to a broad range enantio-
tropic mesophase (Fig. 4). This change is presumably due to better
matching of the length of substituents at the B(12) and C(1) positions
of the {closo-CB11} cluster and consequently better filling space in
head-to-tail moleculararrangement in the SmA phase in 3cthan in 2c.
Structureeproperty relationships found in series 1[Pyr] and 2
[Pyr] are consistent with trends observed for the NeI transition in
non-ionic structurally related calamitic mesogens of the general
structure 14 (Fig. 5) [20]. Thus, statistical analysis of the difference in
TNI for 16 pairs of isostructuralmesogenic esters 14a and 14b, and four
pairs of ethers 14c shows that replacement of the benzene ring with
cylcohexane increases the nematic phase stability by 18 ꢂ 8 K,
20 ꢂ 7 K and 46 ꢂ 2 K, respectively. On the other hand, changing
orientation of the ester group from ester of phenol to ester of
4.2. Synthesis of esters 1[NEt4]e3c[NEt4]. General procedure
4.2.1. Method A
[closo-1-CB11H10-1-COOH-12-C6H13]ꢀ[NEt4]þ (4[NEt4]) [11].
[closo-1-CB11H10-1-C6H4COOH-12-C6H13]ꢀ[NEt4]þ (5[NEt4]) [1] or
Fig. 2. Optical textures of a SmA phase for 2f[Pyr] (a) and a nematic phase for 1b[Pyr] in a supercooled microdroplet (b). Magnification ꢃ50.

198
A. Jankowiak et al. / Journal of Organometallic Chemistry 747 (2013) 195e200
cooling
Cr
Cr
SmA
I
I
heating
SmA
140
100
110
120
130
150
temperature /oC
a)
b)
Fig. 3. DSC trace of ester a) 2e[Pyr] and b) 1b[Pyr]; heating rate 5 K minꢀ1
.
Fig. 4. A comparison of the transition temperatures for two homologues.
Fig. 6. A comparison of the transition temperatures for two isostructural analogues.
ꢀ
[NMe4]þ (9[NMe4], 50 mg, 0.13 mmol) were added. After
ꢀ
[closo-1-CB11H10-1-C6H4COOH-12-C12H25
]
[NMe4]þ (6[NEt4])
C6H13
]
stirring overnight, the reaction was worked up and pure esters
were isolated as described in Method A.
(0.12 mmol) was dissolved in CH2Cl2 (2 mL), oxalyl chloride (COCl)2
(226 mg, 1.78 mmol) and catalytic amounts of DMF were added.
The reaction mixture was stirred for 30 min and volatiles were
removed in vacuo. For the preparation of phenol esters 1b[NEt4], 1d
[NEt4], 2b[NEt4], crude acid chloride was dissolved in CH2Cl2
(1 mL), pyridine (24 mg, 0.3 mmol) was added followed by phenol 7
(0.12 mmol) and stirred at ambient temperature overnight. For the
preparation of esters 2c[NEt4] and 3c[NEt4], the acid chloride was
dissolved in pyridine (48 mg, 0.6 mmol), trans-pentylcyclohexanol
[12] (102 mg, 0.6 mmol) was added and the reaction mixture was
stirred at 90 ꢁC for 2 days followed by removal of volatiles in vacuo.
The resulting reaction mixture was diluted with CH2Cl2 and washed
twice with 10% HCl. The organic layer was separated, and the
aqueous layer was extracted (CH2Cl2). Combined CH2Cl2 layers
were dried (Na2SO4) and solvent evaporated giving a white crys-
talline solid of esters as the [NEt4]þ salt. The crude ion pair was
passed through a silica gel plug (CH2Cl2/MeCN, 5:1) and used for
the subsequent cation exchange.
4.3. Preparation of 1[Pyr]e3[Pyr]. General procedure
The ion pair 1[NEt4], 2[NEt4] or 3[NEt4] was dissolved in CH2Cl2
and N-butyl-4-heptyloxypyridinium bromide [9] (2.0 equiv) was
added resulting in formation of a precipitate. Water was added and
the biphasic system was stirred vigorously until all the precipitate
had dissolved. The CH2Cl2 layer was separated, and the aqueous
layer was extracted with additional CH2Cl2. The CH2Cl2 layers were
combined, dried (Na2SO4), evaporated and the resulting product
was passed through a short silica gel plug (CH2Cl2) giving a white
crystalline solid product. Further purification was achieved by
repeating recrystallization from EtOH/H2O mixtures (3e5ꢃ), and
AcOEt/n-hexane mixtures (2ꢃ) providing pure product as white
crystalline material.
4.3.1. Ester 1b[Pyr]
Obtained in 55% overall yield according to Method A: 1H NMR
4.2.2. Method B
4-Pentylbenzoic acid or trans-4-pentylcyclohexanecarboxylic
acid (0.15 mmol) was dissolved in excess SOCl2 (1 mL), stirred at
75 ꢁC for 2 h and evaporated to dryness in vacuo. The resulting
crude acid chloride was dissolved in anhydrous CH2Cl2 (2 mL),
pyridine (24 mg, 0.30 mmol) and [closo-1-CB11H10-1-C6H4OH-12-
(400 MHz, CD3CN) d 0.40e2.50 (m, 10H, BeH), 0.47e0.58 (m, 2H, B-
CH2), 0.88 (t, J ¼ 6.7 Hz, 3H, CH3), 0.91 (t, J ¼ 6.8 Hz, 6H, CH3), 0.96 (t,
J ¼ 7.4 Hz, 3H, CH3), 1.13e1.41 (m, 20H, CH2), 1.42e1.50 (m, 2H, CH2),
1.60e1.68 (m, 2H, CH2), 1.77e1.92 (m, 4H, CH2), 2.64 (t, J ¼ 7.8 Hz,
2H, Benz-CH2), 4.29 (t, J ¼ 6.7 Hz, 2H, O-CH2), 4.31 (t, J ¼ 8.1 Hz, 2H,
N-CH2), 7.13 (d, J ¼ 8.5 Hz, 2H, Benz-H), 7.19 (d, J ¼ 8.7 Hz, 2H, Benz-
H), 7.28 (d, J ¼ 8.5 Hz, 2H, Benz-H), 7.34 (d, J ¼ 7.4 Hz, 2H, Pyr-H),
8.17 (d, J ¼ 8.7 Hz, 2H, Benz-H), 8.39 (d, J ¼ 7.3 Hz, 2H, Pyr-H); 13C
{1H} NMR (100 MHz, CD3CN)
d 13.8, 14.4, 14.5, 14.6, 20.0, 21.2 (br),
23.2, 23.3, 23.6, 26.3, 29.2, 29.6, 31.2, 31.3, 31.7, 32.2, 32.5, 32.9, 33.6,
33.8, 36.6, 60.6, 72.4, 114.8, 123.3, 123.9, 127.7, 129.8, 131.0, 146.4,
149.6, 149.7, 150.8, 163.8, 166.1, 167.6, 171.7. Anal. Calcd for
C42H70B11NO5: C, 64.02; H, 8.95; N, 1.78. Found: C, 64.32; H, 8.95; N,
1.82.
4.3.2. Ester 1d[Pyr]
Fig. 5. Statistical analysis of difference in TNI for series of n isostructural pairs of
mesogens. Chx stands for the cyclohexane ring, Ben for benzene and BCO for bicyclo
[2.2.2]octane.
Obtained in 56% overall yield according to Method A: 1H NMR
(400 MHz, CD3CN) d 0.40e2.50 (m, 10H, B-H), 0.47e0.58 (m, 2H, B-

A. Jankowiak et al. / Journal of Organometallic Chemistry 747 (2013) 195e200
199
CH2), 0.88 (t, J ¼ 6.3 Hz, 3H, CH3), 0.907 (t, J ¼ 6.1 Hz, 3H, CH3), 0.909
(t, J ¼ 6.0 Hz, 3H, CH3), 0.96 (t, J ¼ 7.4 Hz, 3H, CH3), 1.13e1.41 (m,
20H, CH2), 1.42e1.50 (m, 2H, CH2), 1.67 (quint, J ¼ 7.4 Hz, 2H, CH2),
1.75e1.92 (m, 4H, CH2), 2.72 (t, J ¼ 7.7 Hz, 2H, Benz-CH2), 4.29 (t,
J ¼ 6.6 Hz, 2H, O-CH2), 4.31 (t, J ¼ 7.4 Hz, 2H, N-CH2), 7.06 (d,
J ¼ 8.9 Hz, 2H, Benz-H), 7.24 (d, J ¼ 8.9 Hz, 2H, Benz-H), 7.34 (d,
J ¼ 7.5 Hz, 2H, Pyr-H), 7.40 (d, J ¼ 8.3 Hz, 2H, Benz-H), 8.08 (d,
J ¼ 8.2 Hz, 2H, Benz-H), 8.39 (d, J ¼ 7.5 Hz, 2H, Pyr-H). Anal. Calcd for
C42H70B11NO5: C, 64.02; H, 8.95; N, 1.78. Found: C, 64.20; H, 8.91; N,
1.87.
(d, J ¼ 7.4 Hz, 2H, Pyr-H); 13C{1H} NMR (100 MHz, CD3CN)
d
13.7,
14.36, 14.39, 14.41, 19.9, 23.3, 23.38, 23.40, 26.2, 27.6, 29.1, 29.5, 30.1,
30.39, 30.44, 30.50, 30.56, 31.5, 31.7, 32.39, 32.42, 32.7, 32.9, 33.52,
34.1, 37.3, 37.4, 60.6, 72.3, 74.9,114.8,129.2, 129.9, 146.4, 147.7,166.4,
171.7. Anal. Calcd for C47H88B11NO3: C, 67.68; H, 10.63; N, 1.68.
Found: C, 67.96; H, 10.52; N, 1.76.
ꢀ
4.4. [closo-1-CB11H10-1-C6H4COOH-12-C12H25
]
[NEt4]þ (6[NEt4])
To a solution of anhydrous ZnCl2 (2.10 g, 15.4 mmol) in anhy-
drous THF (6 mL) under Ar was added C12H25MgBr (14.3 mL,
14.3 mmol, 1.0 M in Et2O) at 0 ꢁC forming a white, thick slurry,
which was stirred for 15 min. Anhydrous NMP (6 mL),
Pd2(dba)3$CHCl3 (24.6 mg, 2 mol %), and, [HPCy3](BF4) (35.1 mg,
8 mol %) were then added and the reaction mixture turned dark
4.3.3. Ester 2b[Pyr]
Obtained in 47% overall yield according to Method A: 1H NMR
(400 MHz, CD3CN) d 0.40e2.50 (m, 10H, B-H), 0.50e0.55 (m, 2H, B-
CH2), 0.88 (t, J ¼ 6.9 Hz, 3H, CH3), 0.91 (t, J ¼ 6.8 Hz, 6H, CH3), 0.96 (t,
J ¼ 7.4 Hz, 3H, CH3), 1.15e1.53 (m, 22H, CH2), 1.64 (quint, J ¼ 7.5 Hz,
2H, CH2), 1.80e1.92 (m, 4H, CH2), 2.64 (t, J ¼ 6.6 Hz, 2H, Benz-CH2),
4.29 (t, J ¼ 6.6 Hz, 2H, O-CH2), 4.31 (t, J ¼ 7.5 Hz, 2H, N-CH2), 7.11 (d,
J ¼ 8.5 Hz, 2H, Benz-H), 7.27 (d, J ¼ 8.4 Hz, 2H, Benz-H), 7.34 (d,
J ¼ 7.5 Hz, 2H, Pyr-H), 7.69 (d, J ¼ 8.6 Hz, 2H, Benz-H), 7.92 (d,
J ¼ 8.6 Hz, 2H, Benz-H), 8.39 (d, J ¼ 7.5 Hz, 2H, Pyr-H); 13C{1H} NMR
green but slowly faded to red/orange. After 5 min, [closo-1-CB11H10
-
1-[4-C6H4COOH]-12-I]ꢀ [NMe4]þ [1] (11[NMe4], 583 mg,
1.18 mmol) was added, and the reaction mixture was stirred at
90 ꢁC until ESI-MS spectrum of a small aliquot (quenched in sat.
NH4Cl and extracted into AcOEt) showed complete conversion to
product (about 24 h; if not completed, the palladium source and
ligand were further added.). Sat. NH4Cl (50 mL) was added and the
remaining aqueous layer was extracted with Et2O twice. The
organic layers were combined, dried over Na2SO4, and solvent was
removed giving a black sludge. This material was purified by col-
umn chromatography (SiO2, CH2Cl2/CH3CN 9:1 then CH2Cl2/
CH3CN/MeOH 9:3:1). The purity of fractions was confirmed by TLC
and ESI-MS analyses. The resulting product was dissolved in AcOEt
the solution was washed with 1 N HCl (ꢃ2), then with aq. Et4NBr
twice, and dried (Na2SO4). The solvent was removed, and the
resulting material was dried in vacuo giving 426 mg (64% yield) of
the 12-dodecyl acid 6[NEt4] as a pale solid material: 1H NMR
(100 MHz, CD3CN)
d 13.7, 14.3, 14.4, 14.5, 19.9, 21.0 (br), 23.2, 23.3,
23.5, 26.2, 29.1, 29.5, 31.2, 32.0, 32.2, 32.4, 32.8, 33.5, 33.7, 35.8, 60.5,
72.3, 114.8, 122.5, 122.8, 128.3, 130.3, 132.5, 141.8, 146.4, 149.9, 156.2,
165.4, 167.0, 171.6; 11B{1H} NMR (128 MHz, CD3CN)
d
ꢀ13.4
(5B), ꢀ11.6 (2B), 3.9 (br, 1B). Anal. Calcd for C41H70B11NO3: C, 66.20;
H, 9.48; N, 1.88. Found: C, 66.52; H, 9.42; N, 1.91.
4.3.4. Ester 2d[Pyr]
Obtained in 62% overall yield according to Method B: 1H NMR
(400 MHz, CD3CN)
d 0.4e2.5 (m, 10H, B-H), 0.45e0.55 (m, 2H, B-
CH2), 0.88 (t, J ¼ 7.1 Hz, 3H, CH3), 0.91 (t, J ¼ 6.7 Hz, 3H, CH3), 0.91 (t,
J ¼ 6.7 Hz, 3H, CH3), 0.96 (t, J ¼ 7.3 Hz, 3H, CH3), 1.13e1.53 (m, 22H,
CH2), 1.59e1.68 (m, 2H, CH2), 1.64 (quint, J ¼ 7.5 Hz, 2H, CH2), 1.86e
1.92 (m, 4H, CH2), 2.64 (t, J ¼ 7.6 Hz, 2H, Benz-CH2), 4.29 (t,
J ¼ 6.6 Hz, 2H, O-CH2), 4.31 (t, J ¼ 7.5 Hz, 2H, N-CH2), 7.11 (d,
J ¼ 8.5 Hz, 2H, Benz-H), 7.27 (d, J ¼ 8.4 Hz, 2H, Benz-H), 7.34 (d,
J ¼ 7.5 Hz, 2H, Pyr-H), 7.69 (d, J ¼ 8.6 Hz, 2H, Benz-H), 7.92 (d,
J ¼ 8.6 Hz, 2H, Benz-H), 8.39 (d, J ¼ 7.5 Hz, 2H, Pyr-H); 11B{1H} NMR
(400 MHz, CD3CN) d 0.40e2.50 (m, 10H, B-H), 0.48e0.57 (m, 2H, B-
CH2), 0.89 (t, J ¼ 6.8 Hz, 3H, CH3), 1.15e1.35 (m, 32H, CH2), 3.17 (q,
J ¼ 7.3 Hz, 8H, CH2), 7.60 (d, J ¼ 8.6 Hz, 2H, Benz-H), 7.76 (d,
J ¼ 8.6 Hz, 2H, Benz-H); 13C{1H} NMR (124.5 MHz, acetone-d6)
d 7.7,
14.4, 21.2 (br), 23.3, 29.4, 30.09, 30.16, 30.31, 30.39, 30.46, 30.54,
30.63, 30.68, 32.6, 53.0 (t, JCN ¼ 3.0 Hz), 129.2, 129.3, 129.5, 148.3,
167.5; 11B{1H} NMR (128 MHz, CD3CN)
d
ꢀ13.3 (5B), ꢀ11.6 (5B), 3.4
(br, 1B); 11B{1H} NMR (159 MHz, acetone-d6)
d
ꢀ12.9 (5B), ꢀ11.1
(128 MHz, CD3CN)
for C41H70B11NO3: C, 66.20; H, 9.48; N, 1.88. Found: C, 66.42; H,
9.46; N, 1.85.
d
ꢀ13.4 (5B), e11.6 (5B), 3.9 (br, 1B). Anal. Calcd
(5B), 4.0 (1B); EIS-MS, m/z 431 (M, 100%). Anal. Calcd for
C28H60B11NO2: C, 59.87; H, 10.77; N, 2.49. Found: C, 60.26; H, 10.53;
N, 2.39.
4.3.5. Ester 2e[Pyr]
Obtained in 87% overall yield according to Method B: 1H NMR
Acknowledgments
(400 MHz, CD3CN)
d 0.4e2.5 (m, 10H, B-H), 0.45e0.55 (m, 2H, B-
CH2), 0.87e0.93 (m, 6H, CH3), 0.88 (t, J ¼ 6.9 Hz, 3H, CH3), 0.96 (t,
J ¼ 7.4 Hz, 3H, CH3), 0.98e1.06 (m, 2H, CH2), 1.12e1.59 (m, 29H, CH
and CH2), 1.80e1.91 (m, 6H, CH2), 2.09e2.12 (m, 2H, CH2), 2.46 (tt,
J1 ¼ 12.2 Hz, J2 ¼ 3.6 Hz, 1H, CHeCOO), 4.29 (t, J ¼ 6.9 Hz, 2H, Oe
CH2), 4.31 (t, J ¼ 7.5 Hz, 2H, N-CH2), 6.81 (d, J ¼ 8.8 Hz, 2H, Benz-H),
7.33 (d, J ¼ 7.5 Hz, 2H, Pyr-H), 7.50 (d, J ¼ 8.8 Hz, 2H, Benz-H), 8.39
This project was supported by the NSF grant (DMR-1207585)
and JSPS KAKENHI (S) (No. 24229001) (to M.U.), Grant-in-Aid for
Young Scientists (A) (No. 25713001) and Astellas Foundation for
Research on Metabolic Disorders (to R.T.).
References
(d, J ¼ 7.5 Hz, 2H, Pyr-H); 11B{1H} NMR (128 MHz, CD3CN)
d
ꢀ13.3
(5B), ꢀ11.7 (5B), 3.4 (1B). Anal. Calcd for C41H76B11NO3: C, 65.66; H,
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(400 MHz, CD3CN) d 0.40e2.50 (m, 10H, B-H), 0.50e0.63 (m, 2H, B-
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7.59 (d, J ¼ 8.6 Hz, 2H, Benz-H), 7.74 (d, J ¼ 8.5 Hz, 2H, Benz-H), 8.39

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[14] 13C NMR (100 MHz, CD3CN)
d
13.7, 14.3, 19.8, 23.2, 26.2, 29.0, 29.5, 32.3, 33.6,
60.1, 72.3, 114.7, 146.8, 171.5