Synthesis of functionalized diarylborinic 8-oxyquinolates via bimetallic boron-lithium intermediates

Article abstract of DOI:10.1016/j.jorganchem.2012.03.002

The simple one-pot approach to functionalized diarylborinic 8-oxyquinolates has been developed starting with selected dihalobenzenes (Hal = Br, I) and (dialkoxy)phenylboranes PhB(OR)₂ (R = Me, Et). The initial step results in halogenated diaryl

Full text of DOI:10.1016/j.jorganchem.2012.03.002

Journal of Organometallic Chemistry 711 (2012) 1e9
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Synthesis of functionalized diarylborinic 8-oxyquinolates via bimetallic
boronelithium intermediates
,
b
,
a
a
a,
Grzegorz Wesela-Bauman a
, Lech Jastrze˛bski , Pawe1 Kurach , Sergiusz Lulinski
**
*
,
ꢀ
a
b
ꢀ
Janusz Serwatowski , Krzysztof Wozniak
a Physical Chemistry Department, Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland
b Laboratory of Crystallochemistry, Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
The simple one-pot approach to functionalized diarylborinic 8-oxyquinolates has been developed
starting with selected dihalobenzenes (Hal ¼ Br, I) and (dialkoxy)phenylboranes PhB(OR)2 (R ¼ Me, Et).
The initial step results in halogenated diarylborinic “ate” complexes which are prone to halogenelithium
exchange when treated with t-BuLi. The resultant dianionic lithiated diarylborinic “ate” complexes of the
type [(LiAr)PhB(OR)2]Li were reacted with selected electrophiles followed by hydrolysis to give
unsymmetrically substituted diarylborinic acids isolated in the form of respective 8-hydroxyquinoline
complexes as the final products in moderate to good yields. The crystal structure of (2-fluoro-4-
formylphenyl)(phenyl)borinic 8-oxyquinolinate has been determined by X-ray diffraction. The alterna-
tive method involving the lithiation of B-protected bis(halophenyl)borinic N,N-dimethylethanolamine
esters followed by the quench with electrophiles has also been investigated.
Received 27 January 2012
Received in revised form
1 March 2012
Accepted 5 March 2012
Keywords:
Organoboranes
Borinic acids
Quinoline derivatives
Bimetallic reagents
Ate complex
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
Symmetrical arylborinic azaesters can also be formed in the reaction
of triarylborane with appropriate ligand due to the cleavage of one
Recently, arylborinic complexes have attracted a special attention
due to their promising applications in materials chemistry and
engineering e especially, in the construction of luminescent devices
as a part of emitting layers, electron transport materials, and as
sensors for inorganic ions [1]. There are also examples of potent
biological activity of selected borinic derivatives [2]. These
compounds were examined as ligands for lithium, zinc, and
magnesium complexes [3], as catalysts in boron-catalyzed aldol
reaction [4], and as reagents in the asymmetric synthesis [5]. In this
context, the improvement of the synthetic chemistry of diarylborinic
derivatives is highly desirable. There are various approaches to these
compounds. Classically, they can be obtained with varying yields by
reacting organolithium or organomagnesium compounds with
borate esters B(OR)3 followed by hydrolysis and esterification with
O,N-chelating ligands such as ethanolamine, 8-hydroxyquinoline
and their analogues [6] (Scheme 1a). However, the method suffers
from the selectivity problems due to the formation of other aryl-
boron products such as arylboronic esters and tetraarylborates.
phenyl group [1f,g,3] (Scheme 1b). Another method is based on the
treatment of organolithium or organomagnesium compounds with
arylboronic esters ArB(OR)2 and hydrolysis followed byesterification
[2a,7] (Scheme 1c). This approach can provide an access to unsym-
metrical borinic acid derivatives. However, the method is limited to
derivatives lacking sensitive functional groups which can react with
aryllithiums or Grignard compounds. Alternatively, diarylborinic
complexes were obtained by transmetalation of aryltin or arylsilicon
compounds with appropriate bromoborane derivatives followed by
addition of complexing agent [1d,e] (Scheme 1d). In a few cases
polymeric unsymmetrical borinic complexes were obtained using
the latter method [1hej,8a,b].
Recently, our group has focused on the generation of bimetallic
aromatic boronelithium reagents and their application to the
synthesis of functionalized arylboronic acids and esters [9]. In this
paper, we present our results concerning related bimetallic systems
and their applications in the synthesis of novel unsymmetrically
functionalized diarylborinic esters. They were isolated as well-
defined and relatively stable 8-hydroxyquinoline (Q) complexes.
* Corresponding author. Tel./fax: þ48 22 234 7575.
2. Results and discussion
** Corresponding author. Physical Chemistry Department, Faculty of Chemistry,
Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland.
E-mail addresses: grzegorz.wesela@chem.uw.edu.pl (G. Wesela-Bauman),
It was shown previously that the protection of the boron atom
against nucleophilic attack is mandatory for the successful
ꢀ
serek@ch.pw.edu.pl (S. Lulinski).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2012.03.002

2
G. Wesela-Bauman et al. / Journal of Organometallic Chemistry 711 (2012) 1e9
addition of t-BuLi, the reaction mixture was consecutively treated
with ca. 20% (v/v) THF, to promote the halogenꢀlithium intercon-
version, and then allowed to warm up to ꢀ75 ꢁC. The resultant
lithiated diarylborinic reagent ate-Li was quenched with DMF to
afford 1 in good yield. This protocol was successfully extended by
employing other electrophiles (Me2S2, TMSCl, t-BuNCO, PhB(OEt)2)
to give corresponding well-defined Q complexes. Our protocol was
successfully applied also with 1,3-diiodobenzene as well as 1,4-
dibromo-2-fluorobenzene as starting materials. The results are
collected in Table 1.
Scheme 1. Synthetic approaches to diarylborinic O,N-chelate complexes.
Specifically, the use of PhB(OEt)2 as the electrophile for
quenching the lithiated borinic “ate” complexes resulted in the
formation of symmetrical bis(diarylborinic) bis(oxyquinolinates)
PhB(Q)C6H4B(Q)Ph 11 (with central para-phenylene core) and 12
(with meta-phenylene core). They are very poorly soluble in
common solvents but their composition was confirmed unambi-
gously by photospray MS.
It should be noted that the usefulness of PhB(OMe)2 as the
borylating reagent in our protocol proved troublesome in most
cases. To our surprise we found that with an exception for ortho-
fluorinated compounds 9 and 10, all other attempts were unsuc-
cessful. This may be due to the insufficient protection of the boron
atom in dimethoxydiphenyl borinic “ate” complexes against
nuclephilic attack during the generation of bimetallic
lithiumeboron reagents.
generation of aromatic boronelithium reagents [9]. We have
investigated two different strategies of the protection. The first one
involved the in situ formation of halogenated borinic anionic “ate”
complexes, featuring the tetra-coordinate boron atom and, hence,
reasonably resistant against lithiating reagents. The second
approach relies on the formation of the halogenated diarylborinic
ester with N,N-dimethylethanolamine (DMAE) possessing BeN
dative bond as the boron protection.
2.1. Synthesis via lithiated diarylborinic “ate” complexes
We have focused especially our attention on a protocol that can
provide unsymmetrical borinic derivatives as they are in many
cases difficult to obtain using known procedures. Thus, we referred
to our previous work [9], where the protection of the boron atom in
the form of the anionic boronic “ate” complex was successfully used
to generate bimetallic lithiumeboron aromatic reagents. This one-
pot protocol was based on the formation of haloarylboronic “ate”
complex from an appropriate dihalobenzene, and subsequent
lithiation followed by reaction with an electrophile. We have
decided to check whether a similar synthetic sequence can be
employed for the synthesis of unsymmetrically functionalized
diarylborinic derivatives isolated as final product in the form of
2.2. Generation of lithiated borinic azaesters and subsequent
reactions with electrophiles
It has been reported that selected lithiated arylboronic N-
alkyldiethanolamine esters can be generated due to the effective
protection of the boron atom achieved by the intramolecular
coordination with nitrogen donor atom [10]. This has prompted us
to study the analogous approach employing selected halogenated
diarylborinic DMAE esters as starting materials. They were
obtained by combining appropriate halophenyllithiums with dia-
lkyl phenylboronates followed by a careful hydrolysis (Table 2). The
resulting crude borinic acids were subjected to the reaction with
DMAE in Et2O to give respective crystalline esters 13e17 only
sparingly soluble in this solvent, and thus, easily collected by
filtration. The tetrahedral environment of the boron atom in 13e17
was clearly evidenced by the 11B NMR spectroscopy showing the
resonances in the range 6e8 ppm.
In the next step we performed the halogenelithium exchange
reactions in halogenated azaesters 13e17 using n-BuLi as well as t-
BuLi (Scheme 3).
In our first approach we have performed bromineelithium
interconversion reactions involving dibrominated ester 13 in
order to generate dilithiated borinic intermediate en route to
symmetrically difunctionalized borinic esters. Initially, we started
with the stoichiometric amount of n-BuLi in THF at ꢀ90 ꢁC. The low
stable
Q complexes (Scheme 2). In our first approach, 4-
iodophenyllithium was obtained from 1,4-diiodobenzene and n-
BuLi in Et2O at ꢀ78 ꢁC. A subsequent reaction with diethyl phe-
nylboronate PhB(OEt)2 resulted in an efficient formation of the
iodinated diarylborinic “ate” complex ate-I. The consecutive step
involved attempted in situ lithiation of ate-I via iodine/lithium
exchange. Unfortunately, n-BuLi (Scheme 2, reaction 3a) proved
ineffective even at þ15 ꢁC. After addition of DMF followed by
hydrolysis with aq. H2SO4 and complexation with Q, we obtained
monoiodinated Q complex containing only ca. 5% of the expected
formylated derivative 1. We have modified this protocol as we have
added THF in order to promote halogen/lithium exchange. Unfor-
tunately, this modification did not improve the course of the latter
reaction. Thus we decided to use t-BuLi in order to perform
iodineelithium exchange. The addition of t-BuLi was performed at
low temperature ꢀ110 ꢁC (Scheme 2, reaction 3b). After the
Scheme 2. Synthesis of functionalized borinic 8-oxyquinolinate 1 via lithiated diarylborinic “ate” complex.

Table 1
Synthesis of borinic Q-esters via “ate” complex functionalization.
Dihalobenzene
Boron reagent/electrophile
Product
Yield [%]
PhB(OEt)2 DMF
70
1
PhB(OEt)2 TMSCl
77
2
PhB(OEt)2 Me2S2
75
3
PhB(OEt)2 t-BuNCO
PhB(OEt)2 TMSCl
PhB(OEt)2 t-BuNCO
70
4
67
5
61
(continued on next page)
6

4
G. Wesela-Bauman et al. / Journal of Organometallic Chemistry 711 (2012) 1e9
Table 1 (continued )
Dihalobenzene
Boron reagent/electrophile
Product
Yield [%]
PhB(OEt)2 Me2S2
76
7
PhB(OEt)2 DMF
81
40
72
86
8
PhB(OMe)2 t-BuNCO
PhB(OMe)2 Me2S2
PhB(OEt)2 PhB(OEt)2
9
10
11
PhB(OEt)2 PhB(OEt)2
80
12
temperature was kept in order to minimize the possibility of the
cleavage of the BeN bond. The reaction mixture was quenched with
an excess of dimethyl disulfide followed by hydrolysis and addition
of Q. We have found that the lithiation did not occur at all as the
complex of the starting bis(4-bromophenyl)borinic acid with Q was
isolated. When we repeated procedure at ꢀ70 ꢁC the reaction
occurred to give the expected disubstituted product 18 in moderate
yield (42%). It was contaminated with substantial amounts of
impurities such as monosubstituted product and dibrominated
ester, which could not be quantitatively removed by recrystalliza-
tion. A large 2.5-fold excess of n-BuLi was not sufficient to complete
the BreLi exchange. When we used the iodo precursor 14 then we

G. Wesela-Bauman et al. / Journal of Organometallic Chemistry 711 (2012) 1e9
5
Table 2
Synthesis of halogenated diarylborinic DMAE complexes 13e17.
Product
X
Y
Z
Yield [%]
13
14
15
16
17
Br
I
I
Br
I
H
H
H
F
Br
I
Br
H
H
78
78
75
76
80
H
obtained 18 in a higher yield (ca 60%) when compared with the
synthesis starting with 13 but again the product was significantly
impure. The use of TMSCl electrophile resulted in the isolation of an
impure bis(silylated) derivative 19 in 60% yield. Finally, we tried to
generate monolithiated arylborinic azaesters from the corre-
sponding monohalogenated precursors 16 and 17 using a high
(5-fold) excess of n-BuLi in THF at ꢀ70 ꢁC. Again, the Hal/Li
exchange reactions were not complete as the crude functionalized
products contained ca. 10% of halogenated esters. Similar results
were obtained with t-BuLi as the lithiating agent. Procedures
repeated in less polar solvent (Et2O) gave similar results. There may
be a few reasons of the problems encountered in the approach to
functionalized borinic derivatives via halogen/lithium exchange in
the B-protected DMAE azaesters. The low solubility of halogenated
diarylborinic azaesters at low temperature may be an important
case as it can significantly decrease the extent of lithiation.
Secondly, our previous results [11] indicated a possible labile
character of the dative BeN bond at ꢀ78 ꢁC in halogenated aryl-
boronic N-alkyldiethanolamine azaesters. In these compounds, the
boron atom is susceptible to alkylation with n-BuLi and thus,
deprotonative lithiation was performed more selectively with
weakly nucleophilic lithium amide bases (LDA and LTMP) [12]. Such
labile behaviour may also be present in DMAE diarylborinic
complexes, resulting in the competitive attack of n-BuLi or the
carbanionic centre of the generated lithiated diarylborinic complex
on the boron atom of the other molecule.
2.3. The crystal structure of compound 8
We have performed single crystal X-ray analysis of compound 8
to additionally confirm the structure of obtained product. Single
crystals suitable for structure determination were obtained by slow
evaporation of the solution of 8 in CH2Cl2. Compound crystallizes in
the triclinic Pꢀ1 space group with one molecule of compound 8 and
one molecule of the solvent in the asymmetrical part of the unit
cell. The position of the solvent molecule is strongly disordered. The
molecular structure of 8 is presented in Fig. 1.
As expected, the intramolecular coordination of the boron atom
by Q-yl nitrogen atom results in the formation of the central five-
membered ring. The tetrahedral geometry of the boron atom is
slightly disordered with the THC index of 74% [13]. The most
important structural parameters are summarized in Table 3. The
supramolecular architecture of 8 is based on CeH.O, CeH.
p
and
interactions. There are two relatively short CeH.O contacts
involving both types of oxygen atoms (Fig. 2, Table 4 ꢀ intermo-
lecular contacts). One of them connects the H atom in the position
p.
p
a
to the Q-yl N atom with the formyl O atom. The characteristic
Scheme 3. The approach to diarylborinic Q complexes via halogenelithium exchange
in the corresponding N,N-dimethylethanolamine esters.
Fig. 1. Ortep-like plot of the solid state structure of 8 showing atom numbering
scheme. Displacement ellipsoids were drawn at the 50% level of probability.

6
G. Wesela-Bauman et al. / Journal of Organometallic Chemistry 711 (2012) 1e9
Table 3
Table 4
Selected bond lengths (Å) and angles (ꢁ) for 8.
CeH.O and CeH.
p
interactions for 8 (in Å and deg.).a
d(DꢀH) d(H.A) d(D.A) DꢀH.
B(1)eO(1)
B(1)eN(1)
B(1)eC(16)
B(1)eC(10)
1.514(3)
1.619(3)
1.614(3)
1.606(4)
C(16)eB(1)ꢀC(10)
C(10)eB(1)ꢀO(1)
O(1)eB(1)ꢀN(1)
N(1)eB(1)ꢀC(16)
C(16)eB(1)ꢀO(1)
N(1)eB(1)ꢀC(10)
112.0(2)
112.7(2)
99.3(2)
111.3(2)
112.0(2)
108.8(2)
DꢀH.
A
A Symmetry operator
C(7)eH(7).O(7)
0.950(3) 2.464(2) 3.409(3) 172.7(2) ꢀx, ꢀy, 1 ꢀ z
C(1)eH(1).O(2)
0.950(3) 2.376(3) 3.016(4) 124.4(2) ꢀx, 1 ꢀ y, ꢀz
C(22)eH(22).Cg(1) 1.00(3) 2.454
3.410
3.381
159.08 ꢀx, ꢀy, ꢀz
C(3)eH(3).Cg(1)
0.949(3) 2.487
156.74 1 ꢀ x, 1 ꢀ y, 1 ꢀ z
a
Cg(1) is the centroid of the C(10)eC(15) ring.
centrosymmetric dimeric motif occurs due to the interaction
between the H atom in the ortho position to the Q-yl O atom with
the Q-yl O atom of the adjacent molecule: as a result an eight-
formation of lithiated diarylborinic DMAE azaesters as reactive
intermediates but several attempts indicate that it is less selective
resulting in the less satisfactory purity of final products.
membered ring is formed. There is also a set of CeH.
p
interac-
tions: the shortest ones involve the unsubstituted Ph ring and the
formyl H atom from one side as well as the H atom in the position
to the Q-yl N atom from the other side of the aromatic ring.
Two types of p.
stacking motifs are observed in the crystal
4. Experimental section
g
4.1. General comments
p
structure of 8. The first motif is based on a close assembly of the
pyridine rings (symmetry operator: 1 ꢀ x, 1 ꢀ y, 1 ꢀ z) of two
neighboring molecules and the other engages both 8-
hydroxyquinoline rings in such a manner that the pyridine ring
from one molecule is located near the phenol ring from the other
one, and vice-versa, the phenol ring from the latter molecule is
located near the pyridine ring from the first one (symmetry
operator: ꢀx, 1 ꢀ y, 1 ꢀ z). Vertical distances within the first and
second motifs are 3.470 Å and 3.367 Å, respectively.
All reactions involving air- and moisture-sensitive reagents
were carried out under an argon atmosphere. Et2O and THF were
stored over sodium wire before use. Starting materials: diiodo-
benzenes, 1,4-dibromo-2-fluorobenzene, and other important
reagents including tert-butyl isocyanate, N,N-dimethylformamide,
dimethyl disulfide, n-BuLi (10 M in hexanes), t-BuLi (1.7 M in
hexanes), B(OR)3 (R ¼ Me, Et) were received from Aldrich and used
without further purification. Phenylboronic esters were prepared
as described previously [14]. The NMR chemical shifts are given
relative to TMS by using known chemical shifts of residual proton
(1H) or carbon (13C) solvent resonances. In the 13C NMR spectra of
arylborinic complexes, the resonances of boron-bound carbon
atoms were not observed in most cases as a result of broadening
owing to partially relaxed 13Ce11B spinespin coupling (11B: I ¼ 3/2).
3. Conclusions
In conclusion, we have evaluated the potential of two different
approaches to functionalized diarylborinic acid derivatives. The
first one is the simple one-pot protocol which uses readily available
starting materials. It is based on the generation of bimetallic lithi-
ated diarylborinic “ate” complexes as a key step. These reagents
were successfully treated with electrophiles to produce some
4.2. Crystal structure determination of compound 8
Single crystal X-ray data collection for 8 were performed on
hitherto unknown unsymmetrical diarylborinic
Q
complexes,
a Bruker AXS Kappa APEX II Ultra diffractometer equipped with
which are not easily accessible by other methods. This includes
especially derivatives bearing reactive functionalities such as amide
and formyl groups. The alternative approach involved the
a TXS rotating anode (MoeKa radiation,
multi-layer optics and an Oxford Cryosystems nitrogen gas-flow
low temperature device (700 Series Cryostream). Single crystals
l
¼ 0.71073 Å), Helios
Fig. 2. Crystal packing motifs for 8 based on a) CeH.O; b) CeH.
p
and p.
p
interactions. Displacement ellipsoids were drawn at the 50% probability level.

G. Wesela-Bauman et al. / Journal of Organometallic Chemistry 711 (2012) 1e9
7
of suitable sizes were attached to a goniometer head using the
ParatoneÒ N oil (from Hampton Research) and maintained at
a constant temperature of 100 K. The data collection strategies were
optimized and monitored using the appropriate algorithms
7.23e7.15 (4H, m, Ar); 13C{1H}NMR (100.6 MHz, [D6]DMSO)
d: 193.3,
157.5, 141.6, 140.3, 136.3, 134.9, 132.4, 131.9, 131.3, 128.5, 128.1, 127.5,
126.8, 124.3, 113.3, 109.0; 11B NMR (64.16 MHz, CDCl3)
d: 12 (w1/
¼ 1600 Hz). Anal. Calcd. for C22H16BNO2 (337.18): C 78.37, N 4.15, H
2
implemented by the APEX2 [15] program package. Only the
u
scans
4.78%, found C 78.21, N 4.53, H 4.83%.
were taken into account using 0.5ꢁ intervals. Determination of the
unit cell parameters and integration of the raw images was per-
formed with the APEX2 suite of programs (integration was done by
SAINT [15]). The data set was corrected for Lorentz and polarization
effects. The multi-scan absorption correction, scaling and merging
of reflections were done with SADABS [15].
The structure was solved by direct methods algorithm using
SHELXS [16]. The IAM refinements, based on F2, were performed
with the SHELXL [16] program. In all cases statistical weights were
applied. Atomic scattering factors, in their analytical form, were
taken from the International Tables for Crystallography [17]. All
non-hydrogen atoms were refined anisotropically and most of the
hydrogen atoms were placed in idealized positions (with 0.96 Å for
CeH bond distances) within the riding model for ADPs (with
UiHso ¼ 1:2,UeCq). The positions of hydrogen atom were clearly
visible on the residual density maps. Positions of the solvent
molecules were strongly disordered and the refinement led to ca.
0.5:0.5 occupancies. Additional constraints covering ADPs were
applied (Table 5).
All other compounds in this section were prepared as described
for the preparation of 1.
4.3.1.2. B(4-trimethylsilylphenyl)(phenyl)Q (2). Starting materials:
1,4-diiodobenzene (3.3 g, 0.01 mol), PhB(OEt)2 (1.9 mL, 0.01 mol),
Me3SiCl (1.13 mL, 0.01 mol). Yield: 2.95 g (77%), m.p. 201ꢀ202 ꢁC 1H
NMR (400 MHz, [D6]DMSO) d: 9.13 (1H, dd, J 5.1 Hz, J 0.9 Hz, Q), 8.77
(1H, dd, J 8.4 Hz, J 0.9 Hz, Q), 8.64e8.50 (1H, m, Ar), 8.24e8.09 (1H,
m, Ar), 7.89 (1H, dd, J 8.3 Hz, J 5.1 Hz, Ph), 7.70 (1H, t, J 2.0 Hz, Ph),
7.61e7.49 (1H, m, Ar), 7.68e7.34 (3H, m, Ar), 7.27e7.14 (3H, m, Ar),
7.10e6.55 (2H, m, Ph), 0.18 (9H, s, SiMe3); 13C{1H}NMR (100.6 MHz,
[D6]DMSO) d: 157.8, 141.3, 140.0, 137.3, 136.4, 136.1, 132.4, 132.2,
131.4, 130.9, 128.0, 127.3, 126.6, 124.2, 112.9, 108.7, ꢀ1.04; 11B NMR
(64.16 MHz, CDCl3)
C24H24BNOSi (283.13): calcd. C 75.59, N 3.67, H 6.34%, found C
75.26, N 3.94, H 6.25%.
d
: 10 (w1/2 ¼ 1800 Hz). Anal. Calcd. for
4.3.1.3. B(4-methylthiophenyl)(phenyl)Q (3). Starting materials:
1,4-diiodobenzene (3.3 g, 0.01 mol), PhB(OEt)2 (1.9 mL, 0.01 mol),
Me2S2 (0.9 mL, 0.01 mol). Yield: 2.67 g (75%), m.p. 162ꢀ164 ꢁC 1H
NMR (400 MHz, CDCl3) d: 8.56 (1H, d, J 5.0 Hz, Q), 8.41 (1H, d, J
4.3. Description of syntheses and compound characterization
8.3 Hz, Q), 7.69e7.61 (2H, m, Ar), 7.44 (2H, d, J 6.4 Hz, Ar), 7.37 (2H,
d, J 7.6 Hz, Ar), 7.30e7.17 (7H, m, Ar), 2.44 (3H, s, SMe); 13C{1H}NMR
4.3.1. Syntheses of functionalized diarylborinic 8-oxyquinolates
involving lithiated diarylborinic “ate” complexes
(100.6 MHz, [D6]DMSO)
132.1, 131.4, 128.0, 127.4, 126.6, 125.4, 124.2, 113.0, 108.7, 14.8; 11B
NMR (64.2 MHz, [D6]acetone)
d: 157.7, 141.3, 140.0, 136.3, 135.9, 132.4,
4.3.1.1. B(4-Formylphenyl)(phenyl)Q(1). n-BuLi (1 mL,10 M, 0.01 mol)
was added to a stirred suspension of 1,4-diiodobenzene (3.3 g,
0.01 mol) in Et2O (50 mL) at ꢀ78 ꢁC. After 1 h PhB(OEt)2 (1.9 mL,
0.01 mol) was added and mixture was stirred for 1 h. At ꢀ110 ꢁC
t-BuLi (11.8 mL, 1.7 M, 0.02 mol) was added, followed by THF (10 mL).
The mixture was allowed to warm up to ꢀ75 ꢁC during 1 h followed
by dropwise addition of DMF (0.8 mL, 0.01 mol). After 1 h the solvent
was removed under vacuum, and the obtained residue was dissolved
in Et2O (50 mL). The mixture was cooled down to ꢀ15 ꢁC and
hydrolyzed with aq. sulfuric acid (20 mL, 1.5 M). Phases were sepa-
rated and the organic phase was added to Et2O (10 mL) solution of Q
(1.45 g, 0.01 mol). The resulting yellow solution was stirred for 2 h
and then concentrated in vacuo. The crude product was obtained by
filtration. It was washed with Et2O (20 mL) to give a green powder. It
was dried under vacuum at rt for 24 h. Yield of 1: 4.8 g (70%), m.p.
d
: 9 (w1/2 ¼ 1800 Hz). C22H18BNOS
(355.26): C 74.38, N 3.94, H 5.11%, found C 74.31, N 4.18, H 5.07%.
4.3.1.4. B(4-tert-butylcarbamoylphenyl)(phenyl)Q (4). Starting mate-
rials: 1,4-diiodobenzene (3.3 g, 0.01 mol), PhB(OEt)2 (1.9 mL,
0.01 mol), t-BuNCO (1.2 mL, 0.01 mol). Yield: 2.88 g (70%), m.p.
208ꢀ209 ꢁC 1H NMR (400 MHz, CDCl3)
d: 9.14 (1Η, J 5.0 Hz, Q) 8.55
(1H, d, J 8.2 Hz, Q), 7.91 (1H, dd, J 8.4 Hz, J 5.1 Hz, Ar), 7.71 (1H, t, J
8.0 Hz, Ar), 7.61 (2H, d, J 8.0, Ph), 7.56 (1H, s, NH), 7.43 (3H, m, Ar),
7.33e7.31 (2H, m, Ar), 7.31e7.14 (4H, m, Ar), 1.33 (9H, s, CMe3); 13
C
{1H}NMR (100.6 MHz, [D6]DMSO)
134.4, 132.4, 131.4, 130.9, 128.0, 127.4, 126.7, 126.3, 124.2, 113.1, 108.8,
50.6, 28.6; 11B NMR (64.2 MHz, [D6]acetone)
d: 166.9, 157.7, 141.4, 140.1, 136.3,
d: 9 (w1/2 ¼ 640 Hz).
Anal. Calcd. for C26H25BN2O2 (408.30): C 76.48, N 6.86, H 6.17%,
found C 76.75, N 6.53, H 6.11%.
146ꢀ147 ꢁC 1H NMR (400 MHz, [D6]DMSO)
d: 9.93 (1H, s, CHO), 9.23
(1H, dd, J 5.1 Hz, J 0.7 Hz, Q), 8.81 (1H, dd, J 8.3 Hz, J 0.8 Hz, Q), 7.93
(1H, dd, J 8.3 Hz, J 5.1 Hz, Ar), 7.76 (2H, m, Ar), 7.72 (1H, t, J 8.0 Hz, Ph),
7.64 (2H, d, J 8.1 Hz, Ph), 7.45 (1H, d, J 8.1 Hz, Ar), 7.34 (2H, m, Ar),
4.3.1.5. B(3-trimethylsilylphenyl)(phenyl)Q (5). Starting materials:
1,3-diiodobenzene (3.3 g, 0.01 mol), PhB(OEt)2 (1.9 mL, 0.01 mol),
Me3SiCl (1.3 mL, 0.01 mol). Yield: 2.56 g (67%), m.p. 167ꢀ169 ꢁC 1H
NMR (400 MHz, CDCl3) d: 9.13 (1H, dd, J 5.1, J 0.8 Hz, Q), 8.77 (1H,
dd, J 8.3 Hz, J 0.8 Hz, Q), 7.90 (1H, dd, J 8.3 Hz, J 5.1 Hz, Ar), 7.70 (1H, J
7.9 Hz, Ar), 7.55 (1H, s, Ph), 7.42 (1H, d, J 8.4 Hz, Ar), 7.39e7.28 (4H,
m, Ar), 7.28e7.11 (5H, m, Ph), 0.14 (9H, s, SiMe3); 13C{1H}NMR
Table 5
Selected crystal data for compound 8.
Chemical formula
Mr
Crystal system, space group
Temperature (K)
a, b, c (Å)
C45H32B2Cl2F2N2O4
795.25
(100.6 MHz, [D6]DMSO) d: 178.8, 157.8, 141.3, 140.0, 137.9, 136.4,
136.1,136.0, 132.4, 132.1,131.5,131.4,128.0,127.3,126.8,126.6,124.2,
Triclinic, Pꢀ1
120.8, 112.9, 108.7, ꢀ1.0; 11B NMR (64.2 MHz, CDCl3)
d: 10 (w1/
100
8.1868 (2), 9.2398 (3), 12.9267 (4)
92.856 (2), 105.140 (2), 96.713 (2)
934.12 (5)
1
0.951, 0.977
19677, 4393, 2993
¼ 1200 Hz). Anal. Calcd. for C24H24BNSiO (381.35): C 75.59, N 3.67,
2
a
,
b
,
g
(ꢁ)
H 6.34%, found, C 75.40, N 3.84, H 5.98%.
V (Å3)
Z
4.3.1.6. B(3-tert-butylcarbamoylphenyl)(phenyl)Q (6). Starting mate-
rials: 1,3-diiodobenzene (3.3 g, 0.01 mol), PhB(OEt)2 (1.9 mL,
0.01 mol), t-BuNCO (1.2 mL, 0.01 mol). Yield: 2.50 g (61%), m.p.
Tmin, Tmax
No. of measured, independent and
observed [I > 2
Rint
R[F2 > 2
Drmax
Drmin (e Åꢀ3
s
(I)] reflections
168ꢀ169 ꢁC 1H NMR (400 MHz, [D6]DMSO)
d
: 9.15 (1Η, d, J 4.8 Hz, Q)
0.038
0.058, 0.148, 1.22
0.78, ꢀ0.91
s
(F2)], wR(F2), S
8.78 (1H, d, J 8.0 Hz, Q), 7.91 (1H, dd, J 8.4 Hz, J 5.2 Hz, Ar), 7.75 (1H, s,
Ar), 7.71 (1H, t, J 8.0 Hz, Ar), 7.61 (2H, m, Ph), 7.50 (1H, m, Ar), 7.43 (1H,
,
)

8
G. Wesela-Bauman et al. / Journal of Organometallic Chemistry 711 (2012) 1e9
d, J 8.4 Hz Ar), 7.33e7.31 (2H, dd, J 8 Hz, J 2 Hz, Ar), 7.27e7.10(5H, m,
Ar),1.32 (9H, s, CMe3); 13C{1H}NMR (100.6 MHz, [D6]DMSO)
: 167.3,
4.3.1.11. 1,4-Bis[B(phenyl)Q]benzene (11). Starting materials: 1,4-
diiodobenzene (3.3 g, 0.01 mol), PhB(OEt)2 (3.8 mL, 0.02 mol).
Yield: 4.66 g (86%), m.p. 365ꢀ366 ꢁC. MS (Photospray, CH3COOC2H5):
m/z: Calcd. C36H27B2N2O2 (MHꢂ, 541.2), C30H21B2N2O2 (463.2),
C24H17B2N2O2 (387.1), C15H11BNO (232.1); found: 541.3, 463.4, 387.6,
232.2. Anal. Calcd. for C36H26B2N2O2 (540.22): C 80.04, H 4.85, N
5.19%, found C 80.32, H 4.83, N 5.12%.
d
157.7, 147.2, 141.4, 140.1, 136.4, 134.9, 134.0, 132.4, 131.4, 130.4, 128.1,
127.4, 126.9, 124.6, 125.5, 124.2, 50.6, 28.6; 11B NMR (64.2 MHz, [D6]
DMSO)
d
: 11 (w1/2 ¼ 1900 Hz). Anal. Calcd. for C26H25BN2O2 (408.30):
C 76.48, N 6.86, H 6.17%, found C 76.45, N 6.79, H 6.15%.
4.3.1.7. B(3-methylthiophenyl)(phenyl)Q (7). Starting materials:
1,3-diiodobenzene (3.3 g, 0.01 mol), PhB(OEt)2 (1.9 mL, 0.01 mol),
Me2S2 (0.9 mL, 0.01 mol). Yield: 2.71 g (76%), m.p. 142ꢀ143 ꢁC.
4.3.1.12. 1,3-Bis[B(phenyl)Q]benzene (12). Starting materials: 1,3-
diiodobenzene (3.3 g, 0.01 mol), PhB(OEt)2 (3.8 mL, 0.02 mol).
Yield: 4.32 g (80%), m.p.149ꢀ150 ꢁC. MS (Photospray, CH3COOC2H5):
m/z: Calcd. C36H27B2N2O2 (MHꢂ, 541.2), C30H21B2N2O2 (463.2),
C24H17B2N2O2 (387.1), C15H11BNO (232.1); found. 541.5, 463.4, 387.5,
232.2 Anal. Calcd. for C36H26B2N2O2 (540.22): C 80.04, H 4.85, N
5.19%, found C 79.95, H 4.80, N 5.17%.
1H NMR (400 MHz, [D6]DMSO)
d: 9.16 (1H, d, J 5.1 Hz, Q), 8.77
(1H, d, J 8.0 Hz, Q), 7.90 (1H, dd, J 8.3 Hz, J 5.1 Hz, Ar), 7.70 (1H, t, J
8.0 Hz, Ar), 7.42 (1H, d, J 8.4 Hz, Ar),7.37e34 (2H, m, Ar), 7.24e7.16
(7H, m, Ar), 7.09e7.06 (1H, m, Ar), 2.36 (3H, s, SMe); 13C{1H}NMR
(100.6 MHz, [D6]DMSO)
131.8, 129.4, 128.2, 128.0, 127.4, 127.3, 126.6, 124.3, 124.2, 113.1,
108.8, 14.8; 11B NMR (64.2 MHz, [D6]DMSO)
d: 157.7, 141.5, 140.1, 136.6, 136.3, 132.4,
4.3.2. Synthesis of halogenated diarylborinic DMAE azaesters
d
: 10 (w1/2 ¼ 1200 Hz).
4.3.2.1. B(4-bromophenyl)2(N,N-dimethylethanolamine) (13). n-BuLi
(5 mL,10 M, 0.05 mol) was added dropwise to a stirred suspension of
1,4-dibromobenzene (11.8 g, 0.05 mol) in Et2O (50 mL) at ꢀ70 ꢁC.
The mixture was stirred for 1 h followed by a dropwise addition of
dimethyl 4-bromophenylboronate (11.5 g, 0.05 mol). The mixture
was stirred for 1 h at ꢀ70 ꢁC and then warmed up to 0 ꢁC. After
addition of aq. H2SO4 (15 mL, 1.5 M) the organic phase was sepa-
rated. The aqueous phase was extracted with Et2O (2 ꢃ 15 mL) and
the extract was combined with the organic phase. DMAE (4.45 g,
0.05 mol) was added to the organic phase to give a white slurry. It
was stirred at rt for 6 h and filtered. The product was washed with
Et2O and dried under vacuum at rt for 24 h. Yield 15.9 g (78%), m.p.
C22H18BNOS (355.26): C 74.38, N 3.94, H 5.11%, found C 74.11, N 3.59,
H 5.10%.
4.3.1.8. B(2-fluoro-4-formylphenyl)(phenyl)Q (8). Starting mate-
rials: 1,4-dibromo-2-fluorobenzene (2.54 g, 0.01 mol), PhB(OEt)2
(1.5 mL, 0.01 mol), DMF (0.8 mL, 0.01 mol). Yield: 2.87 g (81%),
m.p. 158e160 ꢁC 1H NMR (400 MHz, [D6]DMSO)
d: 9.93 (1H, s,
CHO), 9.11 (1H, d, J 4.8 Hz, Q), 8.82 (1H, dd, J 8.6 Hz, J 0.8 Hz, Q),
7.94 (1H, dd, J 8.3 Hz, J 5.2 Hz, Ar), 7.71 (1H, t, J 8.0 Hz, Ar),
7.66e7.64 (1H, m, Ar), 7.60e7.57 (1H, m, Ar), 7.47e7.45 (2H, m, Ar),
7.32 (2H, dd, J 7.9 Hz, J 1.6 Hz, Ar), 7.27e7.14 (4H, m, Ar); 13C{1H}
NMR (100.6 MHz, [D6]DMSO) d: 192.3, 165.8 (d, J 242 Hz), 157.3,
164ꢀ165 ꢁC 1H NMR (400 MHz, [D6]DMSO)
d: 7.56 (4H, d, J 8.0 Hz,
Ph), 7.34 (4H d, J 8.0 Hz, Ph), 4.07 (2H, s, br, CH2), 2.93 (2H, m, CH2),
142.3 (d, J 6 Hz), 140.6, 137.7 (d, J 7 Hz), 136.5, 135.3 (d, J 11 Hz),
132.3, 131.0, 128.0, 127.6, 127.0, 125.1 (d, J 2 Hz), 124.4, 114.7 (d, J
2.49 (6H, s, NMe2); 13C{1H}NMR (100.6 MHz, [D6]DMSO)
129.6, 119.5, 60.1, 46.6, 39.5; 11B NMR (64.16 MHz, [D6]DMSO)
d: 134.5.
26 Hz), 113.5, 109.1; 11B NMR (64.2 MHz, [D6]DMSO)
d: 12. Anal.
d: 10
Calcd. for C22H15BFNO2 (355.17): C 74.40, N 3.94, H 4.26%, found C
73.95, N 3.87, H 4.65%.
(w1/2 ¼ 960 Hz). Anal. Calcd. for C16H18BBr2NO (410.94): C 46.76, N
3.41, H 4.41%. Found: C 46.64, N 3.45 H, 4.40%.
4.3.1.9. B(2-fluoro-4-tert-butylcarbamoylphenyl)(phenyl)Q
(9).
4.3.2.2. B(4-iodophenyl)2(N,N-dimethylethanolamine) (14). The syn-
Starting materials: 1,4-dibromo-2-fluorobenzene (2.54 g, 0.01 mol),
PhB(OMe)2 (1.5 mL, 0.01 mol), t-BuNCO (1.2 mL, 0.01 mol). Yield:
thesis was performed as described for
1 starting with 1,4-
diiodobenzene (16.5 g, 0.05 mol) and dimethyl 4-
iodophenylboronate (13.8 g, 0.05 mol). Yield: 19.6 g (78%), m.p.
1.7 g (40%), m.p. 183ꢀ185 ꢁC 1H NMR (400 MHz, [D6]DMSO)
d: 9.04
202ꢀ203 ꢁC 1HNMR (400 MHz, [D6]DMSO)
d:7.52 (4H, d, J 8.4 Hz, Ph),
7.41 (4H, d, J 8.0 Hz, Ph), 4.05 (2H, t, J 6.8 Hz, CH2), 2.92 (2H, t, J 6.8 Hz,
(1H, d, J 5.2 Hz, Q), 8.81 (1H, dd, J 8.4 Hz, J 0.9 Hz, Q), 7.93 (1H, dd, J
8.34 Hz, J 5.2 Hz, Ar), 7.79e7.64 (2H, m, Ar), 7.57e7.42 (2H, m, Ar),
7.42e7.34 (2H, m, Ar), 7.34e7.27 (2H, m, Ar), 7.13e6.99 (3H, m, Ar),
CH2), 2.49 (6H, s, NMe2); 13C{1H}NMR (100.6 MHz, [D6]DMSO)
d
:
:
1.33 (9H, s, t-Bu); 13C{1H}NMR (100.6 MHz, [D6]DMSO)
d: 165.4,
135.5,134.7, 92.4, 60.1, 46.6, 39.5; 11B NMR (64.16 MHz, [D6]DMSO)
d
165.2 (d, J 237 Hz), 157.4, 148.2, 142.0 (d, J 7 Hz), 140.4, 137.3 (d, J
7 Hz), 136.5, 134.1 (d, J 11 Hz), 132.4, 131.1, 128.0, 127.4, 126.8, 124.3,
122.5 (d, J 2 Hz), 113.6 (d, J 28 Hz), 113.3, 108.9, 50.8, 28.5; 11B NMR
9 (w1/2 ¼ 640 Hz). Anal. Calcd. for C16H18BI2NO (504.94): C 38.06, N
2.77, H 3.59%, found: C 38.04, N 2.71, H 3.50%.
(64.2 MHz, [D6]DMSO)
C26H24BFN2O2 (426.29): calcd. C 73.25, N 6.57, H 5.67%, found C
72.92, N 6.38, H 5.78%.
d
: 10 (w1/2 ¼ 1800 Hz). Anal. Calcd. for
4.3.2.3. B(4-bromophenyl)(4-iodophenyl)(N,N-dimethylethanolamine)
(15). The synthesis was performed as described for 1 starting with
1,4-diiodobenzene (16.5 g, 0.05 mol) and dimethyl 4-
bromophenylboronate (11.4 g, 0.05 mol). Yield: 17.1 g (75%), m.p.
179ꢀ181 ꢁC 1H NMR (400 MHz, [D6]DMSO)
d: 7.55 (4H, m, Ph), 7.42
4.3.1.10. B(2-fluoro-4-methylthiophenyl)(phenyl)Q
materials: 1,4-dibromo-2-fluorobenzene (2.54 g, 0.01 mol),
(10). Starting
(2H, d, J 7.2 Hz, Ph), 7.34 (2H, d, J 8.0 Hz, Ph), 4.06 (2H, s, br, CH2), 2.92
(2H, s, br, CH2), 2.49 (6H, s, NMe2); 13C{1H}NMR (100.6 MHz, [D6]
PhB(OMe)2 (1.5 mL, 0.01 mol), Me2S2 (0.9 mL, 0.01 mol). Yield: 2.69 g
(72%), m.p.164ꢀ166 ꢁC 1H NMR (400 MHz, [D6]DMSO)
d: 9.03 (1H, d,
DMSO)
(64.16 MHz, [D6]DMSO)
C16H18BBrINO (457.94): C 41.96, N 3.06, H 3.96%, found: C 41.64, N
2.71, H 3.59%.
d
: 135.5, 134.7, 134.5, 129.6, 119.5, 92.4, 39.5; 11B NMR
J 5.1 Hz, Q), 8.78 (1H, dd, J 8.4 Hz, J 0.8 Hz, Q), 7.90 (1H, dd, J 8.3 Hz, J
5.1 Hz, Ar), 7.69 (1H, t, J 7.9 Hz, Ar), 7.42 (1H, d, J 7.9 Hz, Ar), 7.33 (2H,
dd, J 7.9 Hz, J 1.5 Hz, Ar), 7.24e7.14 (5H, m, Ar), 6.96 (1H, dd, J 7.9 Hz, J
1.7 Hz, Ar), 6.86 (1H, dd, J 10.0 Hz, J 1.7 Hz, Ar), 2.42 (3H, s, SMe); 13C
d: 6 (w1/2 ¼ 1200 Hz). Anal. Calcd. for
{1H}NMR (100.6 MHz, [D6]DMSO)
d: 166.0 (d, J 242 Hz), 157.5, 141.8
4.3.2.4. B(4-bromo-2-fluorophenyl)(phenyl)(N,N-dimethylethanol-
amine) (16). The synthesis was performed as described for 1 starting
with 1,4-dibromo-2-fluorobenzene (15.1 g, 0.05 mol) and dimethyl
phenylboronate (7.5 g, 0.05 mol). Yield: 13.2 g (76%), m.p.194ꢀ196 ꢁC
(d, J 6 Hz),140.2,139.5 (d, J 9 Hz),136.5,135.0 (d, J 12 Hz),132.3,131.1,
127.9, 127.4, 126.7, 124.2, 121.1 (d, J 2 Hz), 113.2, 112.0 (d, J 28 Hz),
108.8, 14.5; 11B NMR (64.2 MHz, [D6]DMSO)
d: 12 (w1/2 ¼ 1400 Hz).
1H NMR (400 MHz, [D6]DMSO)
d: 7.61 (2H, dd, J 8.4 Hz, J 1.6 Hz, Ph),
Anal. Calcd. for C22H17BFONS (373.25): C 70.79, H 4.59, N 3.75%,
found C 70.62, H 4.75, N 3.83%.
7.52 (2H, d, J 8.0, Ph), 7.45 (2H, d, J 7.5, Ph), 7.17 (2H, d, J 7.2 Hz, Ph), 7.08

G. Wesela-Bauman et al. / Journal of Organometallic Chemistry 711 (2012) 1e9
9
(1H, t, J 7.2 Hz, Ph), 4.08 (2H, t, J 6.4 Hz, CH2), 2.92 (2H, t, J 6.4 Hz, CH2),
2.48 (6H, s, NMe2); 13C{1H}NMR (100.6 MHz, [D6]DMSO)
:163.7 (d, J
241 Hz),137.2(d, J 14 Hz),132.4,126.8,126.7,119.3,117.5, 60.5, 39.5;11B
NMR (64.2 MHz, [D6]DMSO)
C16H18BBrFNO (350.03): C 54.90, N 4.00, H 5.18%, found: C 54.55, N
3.69, H 4.99%.
(Grant No. N N205 055633). The support by Aldrich Chemical Co.,
Milwaukee, WI, U.S.A., through continuous donation of chemicals
and equipment is gratefully acknowledged. G. W.-B. thanks the
Foundation for Polish Science for financial support within the
International PhD Program.
d
d
: 7 (w1/2 ¼ 1400 Hz). Anal. Calcd. for
Appendix A. Supplementary material
4.3.2.5. B(4-iodophenyl)(phenyl)(N,N-dimethylethanolamine) (17).
The synthesis was performed as described for 1 starting with
CCDC 856215 (8) contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.
uk/data_request/cif.
bromobenzene
(7.85
g,
0.05
mol)
and
dimethyl
4-bromophenylboronate (11.4 g, 0.05 mol). Yield: 15.1 g (80%), m.p.
165ꢀ166 ꢁC 1H NMR (400 MHz, [D6]DMSO)
d: 7.61 (2H, dd, J 8.4 Hz,
J 1.6 Hz, Ph), 7.52 (2H, d, J 8.1 Hz, Ph), 7.45 (2H, d, J 7.6 Hz, Ph), 7.17
(2H, d, J 7.2 Hz, Ph), 7.08 (1H, t, J 7.2 Hz), 4.08 (2H, t, J 6.4 Hz, CH2),
2.92 (2H, t, J 6.4 Hz, CH2), 2.49 (6H, s, NMe2); 13C{1H}NMR
References
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halogen/Li exchange in halogenated diarylborinic DMAE azaesters
4.3.3.1. B(4-(methylthio)phenyl)2Q (18). Compound 13 (1.23 g,
3.0 mmol) was dissolved in 50 mL of THF and cooled to ꢀ78 ꢁC
followed by dropwise addition of n-BuLi (1.5 mL, 10 M, 15 mmol).
The mixture was stirred for 1 h at ꢀ75 ꢁC, followed by dropwise
addition of Me2S2 (1.50 g, 16 mmol). After 1 h the mixture was
warmed up to 0 ꢁC. The solvent was removed under vacuum. The
residue was dissolved in 50 mL of Et2O and the solution was cooled
to ꢀ20 ꢁC followed by hydrolysis with aq. H2SO4 (6 mL, 1.5 M). The
aqueous phase was extracted with Et2O (2 ꢃ 15 mL) and the extract
was combined with the organic phase. Q was added (0.44 g,
3.0 mmol) to the organic phase. The resulting yellow solution was
stirred at rt for 2 h and concentrated in vacuo. The crude product
was obtained by filtration. It was washed with dichloromethane
(5 mL) and dried in vacuo at rt for 24 h. Yield: 0.51 g (42%). 1H NMR
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[D6]DMSO) d: 9.13 (1H, d, J 6.8 Hz, Q), 8.77 (1H, d, J 7.8 Hz, Q), 7.89
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(1H, dd, J 6.8 Hz, J 4.8 Hz, Ar), 7.70 (1H, t, J 8.0 Hz, Ar), 7.42 (1H, d, J
8.4 Hz, Ar), 7.36e7.05 (8H, m, Ar), 7.17 (1H, d, J 7.6 Hz, Ar), 0.18 (18H,
ꢀ
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Acknowledgements
This work was supported by the Warsaw University of Tech-
nology and by the Polish Ministry of Science and Higher Education