Functionalization of some benzylthioarylboronic acids by benzylic lithiation of their N-butyldiethanolamine esters or lithium (triisopropoxy) borates

Article abstract of DOI:10.1002/aoc.1822

The reaction of benzylthioarylboronic acids protected as N-butyldiethanolamine esters or as triisopropoxyborates with organolithium bases or lithium diisopropylamide (LDA) has been investigated. The benzylic lithiation occurs selectively using LDA at - 68 °C. The stability of the resultant borio-lithio intermediates is strongly influenced by the position of the boron atom in the phenyl ring. The reaction with various electrophiles affords new arylboronic acids substituted in the benzylic position. Copyright

Full text of DOI:10.1002/aoc.1822

Full Paper
Received: 29 March 2011
Revised: 26 May 2011
Accepted: 1 June 2011
Published online in Wiley Online Library: 10 August 2011
(wileyonlinelibrary.com) DOI 10.1002/aoc.1822
Functionalization of some
benzylthioarylboronic acids by benzylic
lithiation of their N-butyldiethanolamine
esters or lithium (triisopropoxy)borates
a
a∗
a
´
Krzysztof Durka , Tomasz Klis , Janusz Serwatowski
and Krzysztof Woz´niakb
The reaction of benzylthioarylboronic acids protected as N-butyldiethanolamine esters or as triisopropoxyborates with
organolithium bases or lithium diisopropylamide (LDA) has been investigated. The benzylic lithiation occurs selectively using
LDA at −68 ◦C. The stability of the resultant borio-lithio intermediates is strongly influenced by the position of the boron atom
in the phenyl ring. The reaction with various electrophiles affords new arylboronic acids substituted in the benzylic position.
c
Copyright ꢀ 2011 John Wiley & Sons, Ltd.
Keywords: lithiation; boronic acid azaesters; trialkoxyborates; lithiated borates
Introduction
using LDA at −68 ◦C, deprotonation at the benzylic position
occurred. The formation of the lithiated 1 was indicated by
its precipitation from the solution. The obtained organolithium
derivativewasnexttreatedwithMeIandtheusualworkupgavethe
respectivemethylatedboronicacid1awithgoodyield(Scheme 1).
An approach similar to that for 1 also proved useful for the isomer
2 and 3. Again, lithiation proceeded at a low temperature, and
subsequent treatment with MeI gave the products 2a and 3a
methylated in a benzylic position.
The use of 1–3 for the reaction requires the previous protection
ofthecorrespondingboronicacidswithN-butyldiethanolamine.In
order to simplify the procedure we decided to check the reactivity
of the respective lithium trialkoxyborates 4ꢁ –6ꢁ (Scheme 2). We
expected that these compounds would be generated from the
corresponding bromoarenes 4–6 and used for further reaction in
a one-pot procedure.
In the case of 4, the first lithiation using 2 equiv. of t-BuLi
proceeds smoothly via Br–Li exchange to give the corresponding
lithium triisopropoxyborate 4ꢁ after addition of B(OiPr)3. Sub-
sequent treatment of this compound with n-BuLi at −68 ◦C
resulted in the formation of 4ꢁ-Li. This compound was next
treated with methyl iodide to give the respective arylboronic
acid 1a methylated in the benzylic position. However, the
reaction yield was only 15% and a significant amount of 4-
benzylthiophenylboronic acid was recovered. Apparently, the
Recently there has been significant progress in the chemistry of
metalated organoboron derivatives such as lithiated and magne-
siated boronic esters and related complexes.[1] All these reagents
have been effectively used as intermediates in the synthesis of
more elaborated organoboranes[2,3] and functionalized organic
compounds.[4,5] The majority of works are concerned with the
synthesis of sp2 and sp3-geminal borio-lithioderivatives; however,
the synthetic procedures leading to compounds containing boron
and lithium atom bonded to another carbon atom are prac-
tically unexplored.[6,7] Recently, deprotonative lithiation of var-
ious 6-butyl-2-(dihalophenyl)-(N,B)-1,3,6,2-dioxazaborocanes (N-
butyldiethanolamine esters of dihalophenylboronic acids) was
investigated.[8] It was found that LDA deprotonates selectively
the benzene ring, providing that hydrogen atoms are sufficiently
activated. The best activation was achieved for derivatives con-
taining two fluorine atoms attached to the aryl ring. Another
approach involved the halogen–lithium exchange in lithium
(halophenyl)trialkoxyborates.[9] Our work deals with benzylic
lithiation of tetravalent arylboron complexes containing sulfur-
activated benzylic hydrogen atoms. The obtained borio-lithio
derivatives can be easily converted into various functionalized
arylboronic acids that can be used in coupling reactions[10,11] or
tested as saccharides sensors.[12,13]
Results and Discussion
∗
´
Correspondence to: Tomasz Klis, Warsaw University of Technology, Faculty of
Chemistry, Noakowskiego 3, 00-664 Warsaw, Poland.
E-mail: ktom@ch.pw.edu.pl
We started our work with an attempted metalation of 6-butyl-
2-(4ꢁ-benzylthiophenyl)-(N,B)-1,3,6,2-dioxazaborocane 1. As it was
demonstrated previously, the sulfur atom activates the benzylic
position towards deprotonation.[14] For example, deprotonation
of benzyl-phenylsulfide occurs rapidly using LDA in THF at −68 ◦C.
We hence expected that 1 will be sufficiently reactive. Indeed,
a
Warsaw University of Technology, Faculty of Chemistry, Noakowskiego 3,
00-664 Warsaw, Poland
b
Warsaw University, Faculty of Chemistry, Pasteura 1, 02-093 Warsaw, Poland
c
Appl. Organometal. Chem. 2011, 25, 669–674
Copyright ꢀ 2011 John Wiley & Sons, Ltd.

K. Durka et al.
Scheme 1. Lithiation of benzylthiophenylazaesters.
Scheme 2. Lithiation of benzylthiophenyl(triisopropoxy)borates.
acid 2a in the good yield. As we demonstrated in our previous
work, lithiation of 6 should be carried out in Et2O in order to
stabilize the ortho-lithiated 6-Li.[15] However, the use of diethyl
ether results in very slow deprotonation in the benzylic position
and we isolated only traces of 3a. The slow lithiation of 4ꢁ and
5ꢁ is probably caused by the substituents carrying the negative
charge. It should be stressed that analogous lithiation of benzyl-
phenyl sulfide occurs very rapidly using n-BuLi or t-BuLi at −68 ◦C
in THF.
We next turned our attention towards lithiation of 6-butyl-2-(4ꢁ-
phenylthiomethylene-phenyl)-(N,B)-1,3,6,2-dioxazaborocane 7.
This compound contains the benzylic carbon atom bonded di-
rectly to the phenyl ring connected to the borocanyl moiety. It was
revealed that borocanyl group acts as the σ donor and it enhances
the electron density in the phenyl ring, making the hydrogen
atoms much less susceptible to abstraction.[16] We expected that
this σ donation will influence the stability of the benzyl-lithiated
7–9. The lithiation was performed using LDA in THF at −68 ◦C.
The organolithium intermediates were next quenched with MeI.
The usual workup afforded the methylated boronic acids 7a–9a
(Scheme 4) in various yields.
Scheme 3. Interconversion between n-butyllithium and 4-bromobenzyl
bromide leading to 1aꢁ.
reaction of 4ꢁ with n-BuLi is very slow at −68 ◦C. In the con-
trol experiment 4 was lithiated as described above; however,
4-bromobenzyl bromide was used as the electrophile. Unexpect-
edlyweisolatedthemixturecontainingalmostentirelyn-butylated
boronic acid 1aꢁ (ca. 90% according to the 1H-NMR spectrum). This
result confirmed that n-BuLi added for the second lithiation re-
mained unreacted. Addition of benzyl bromide resulted in fast
Br–Li exchange between n-BuLi and benzyl bromide (Scheme 3).
The obtained 4-bromobenzyllithium deprotonated 4ꢁ in benzylic
position to give 4ꢁ-Li, which reacted with n-BuBr with formation
of 1aꢁ.
In addition, a competition experiment was performed to assess
the impact of boronation on the reactivity of the benzyl–phenyl
sulfide system towards benzylic lithiation. For this purpose, a mix-
tureofbenzyl–phenylsulfide(1equiv.)and7(1equiv.)wastreated
withLDA(1equiv.)at−68 ◦CinthepresenceofMe3SiCl(1.1equiv.)
as the electrophile. The reaction mixture was next hydrolyzed and
the concominant molar ratio of unreacted 7 (in the form of
boronic acid) and benzyl–phenyl sulfide (BPS) was determined on
1
the basis of –CH2 –singlets in the H-NMR spectrum. Analogous
experiments were also performed for 8 and 9. The obtained values
of 7/BPS = 1.4, 8/BPS = 2.7 and 9/BPS = 9.7 show that 7–9 are less
reactive towards benzylic lithiation than BPS. The increase in the
amount of unreacted boron compound in the direction 7 < 8 < 9
suggests that the position of the borocanyl group (acting as the σ
donor)inthephenylringplaysanimportantroleinthestabilization
In order to increase the reaction yield, we decided to use t-BuLi
for the second lithiation. However, the result was the same as for
n-BuLi. Finally, using LDA for the second lithiation the conversion
of 4ꢁ to 4ꢁ-Li was almost quantitative, which was indicated after
reaction with MeI leading to 1a in a good yield. A similar approach
proved also succesful for 5. We isolated the methylated boronic
c
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Appl. Organometal. Chem. 2011, 25, 669–674

Functionalization of some benzylthioarylboronic acids
of the benzylic-lithiated 7–9. The high ratio for 9/BPS suggests the Experimental Section
cooperation of the σ donation and a steric effect caused by the
1H- and 13C-NMR spectra were recorded at room temperature
borocanyl group. Similarly to our previous studies, we decided to
check the reactivity of the respective lithium triisopropoxyborates.
An approach analogous to that optimized for 4 and 5 also proved
useful for 10–12. Again, lithiation proceeded at low temperature
using LDA and subsequent treatment of 10ꢁ –12ꢁ with MeI gave
the methylated boronic acids 7a–9a with the yield depending on
the distance between benzylic carbon atom and the B–C bond.
The optimized conditions for the lithiation of aryldioxazaboro-
canes and lithium aryltriisopropoxyborates were next applied for
functionalization in benzylic position with selected electrophiles
to give 1b–e, 2e, 7b and 9c (Schemes 1, 2, 4 and 5). The results
are collected in Table 1. It should be stressed that the route to
arylboronic acids described in our work, through the reversed
approach involving first the introduction of functional group in
the benzylic position and then boronation, would not be possible
in most cases. The molecular structure of 9c was determined us-
ing X-ray analysis (Fig. 1). This compound exists as the anhydride
(boroxine)[17] with Me3Si groups positioned perpendicularly to the
six-membered B3O3 ring.
In conclusion, the benzylic deprotonation of N-butyldi-
ethanolamine protected boronic acids is possible using LDA at
low temperature. However, when the boron atom and ben-
zylic carbon atom are connected to the same benzene ring,
the borocanyl group can reduce the reactivity, making the ben-
zylic hydrogen atom less susceptible to abstraction. The use of
brominated aryl-benzyl sulfides enables the facile formation of
benzyl-functionalized arylboronic acid via a one-pot, two-step
procedure. This reaction requires the use of t-BuLi for the first
lithiation and LDA for the second lithiation. The σ-donation ef-
fect caused by triisopropoxyboron moiety strongly influences the
reaction yield. The obtained lithiated derivatives can be easily
converted to the respective arylboronic acids containing various
substituents in benzylic position.
on a Bruker 400 MHz spectrometer. Chemical shifts are given in
ppm relative to TMS in 1H- and 13C-NMR spectra. All chemicals
were received from Aldrich. THF and Et2O were stored over
sodium prior to use. All reactions were carried out under dry
argon using standard Schlenk techniques. Elemental analyses
were run using a Vario ELIII GMBH apparatus. Melting points were
determined in Pyrex capillary tubes with MeI-Temp apparatus and
are uncorrected.
Typical Procedure for Lithiation of N-Butyldiethanolamine
Derivatives
Inatypicallithiation,6-butyl-2-(4ꢁ-benzylthiophenyl)-(N-B)-1,3,6,2-
dioxazaborocane 1 (1.844 g, 5 mmol) was added as a solid to the
stirred solution of freshly prepared LDA (5 mmol) in THF (30 ml)
at −68 ◦C. The resultant yellowish solution was stirred for 2 h
to give a light-brown precipitate. Electrophile, diethylcarbamyl
chloride (0.68 g, 5 mmol), was then added to the stirred slurry
to form a yellow solution, which was stirred overnight and then
hydrolyzed with water (100 ml) and dilute aqueous H2SO4 to reach
the pH slightly acidic. Et2O (50 ml) was next added and the mixture
was stirred. The organic phase was separated and the aqueous
phase was extracted with Et2O (20 ml). The combined organic
solutions were next dried with MgSO4 and evaporated to give
a solid, which was washed with hexane and recrystallized from
toluene (20 ml) to give 1b as a yellow powder, m.p. 139–141 ◦C;
1H-NMR (400 MHz, DMSO-d6): δ 8.05 (s, OH), 7.63 (d, Ar, J = 8 Hz,
2H), 7.42 (d, Ar, J = 8 Hz, 2H), 7.26 (m, Ph, 5H), 5.61 (s, S–C–H
1H), 3.37 (dq, CH2, J = 7.2 Hz, J = 15.6 Hz, 2H), 3.22 (dq, CH2,
J = 7.2 Hz, J = 15.6 Hz, 2H), 0.95 (t, CH3, J = 7.2 Hz, 3H), 0.85
1
(t, CH3, J = 7.2 Hz, 3H); 13C{ H} NMR (100.6 MHz, DMSO-d6):
167.52 (C O), 137.56 (C–Cbenzyl), 137.21(C–S), 134.52 (C–C–B),
128.93 (Cmeta), 128.45 (Cortho), 128.41 (Cpara), 127.76 (C–C–S), 52.79
Scheme 4. Lithiation of phenylthiomethylphenylazaesters.
Scheme 5. Lithiation of phenylthiomethylphenyl(triisopropoxy)borates.
c
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K. Durka et al.
Table 1. Preparation of functionalized arylboronic acids via benzylic deprotonation and subsequent treatment with various electrophiles
Starting material
Base, temperature
Electrophile
CH3I
Product
Yield (%)
LDA, −68 ◦C, 1.5 h
75
71
H3C
1
4
1a
1a
1: 2 t-BuLi, 0.5 h; 2: LDA, −68 ◦C, 1.5 h
C6H5
(HO)2B
1
4
LDA, −68 ◦C, 1.5 h
(C2H5)2NCOCl
N(C2H5)2
67
61
1: 2 tBuLi, 0.5 h; 2: LDA, −68 ◦C, 1.5 h
O
1b
1b
C6H5
(HO)2B
S
1
4
LDA, −68 ◦C, 1.5 h
tBuNCO
NHt-Bu
79
68
1: 2 tBuLi, 0.5 h; 2: LDA, −68 ◦C, 1.5 h
O
1c
1c
C6H5
(HO)2B
(HO)2B
S
LDA, −68 ◦C, 1.5 h
CO2
57
53
HOOC
1
4
C6H5
1d
S
1: 2 tBuLi, 1.5 h; 2: LDA, −68 ◦C, 1.5 h
(CH3)3SiCl
(H3C)3Si
S
1e
(HO)2B
(HO)2B
2
5
LDA, −68 ◦C, 1.5 h
CH3I
77
69
H3C
1: 2 t-BuLi, 0.5 h; 2: LDA, −68 ◦C, 1.5 h
2a
C6H5
2a
S
2
5
LDA, −68 ◦C, 1.5 h
(CH3)3SiCl
(H3C)3Si
56
49
(HO)2B
1: 2 tBuLi, 0.5 h; 2: LDA, −68 ◦C, 1.5 h
2e
2e
C6H5
S
3
6
LDA, −68 ◦C, 1.5 h
CH3I
H3C
45
10
3a
3a
1: 2 t-BuLi, Et2O, 0.5 h; 2: LDA, −68 ◦C, 1.5 h
C6H5
S
B(OH)2
7
LDA, −68 ◦C, 2 h
CH3I
79
73
S
C6H5
7a
7a
10
1: 2 t-BuLi, 0.5 h; 2: LDA, −68 ◦C, 2 h
(HO)2B
(HO)2B
(HO)2B
CH3
S
7
LDA, −68 ◦C, 2 h
tBuNCO
68
76
C6H5
O
7b
7b
10
1: 2 t-BuLi, 0.5 h; 2: LDA, −68 ◦C, 2 h
(C2H5)2N
8
LDA, −68 ◦C, 2 h
CH3I
64
55
1: 2 t-BuLi, 0.5 h; 2: LDA, −68 ◦C, 2 h
8a
8a
11
S
C6H5
CH3
c
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Functionalization of some benzylthioarylboronic acids
Table 1. (Continued)
Starting material
Base, temperature
Electrophile
CH3I
Product
Yield (%)
LDA, −68 ◦C, 4 h
33
28
B(OH)2
9
9a
9a
12
1: 2 t-BuLi, 0.5 h; 2: LDA, −68 ◦C, 4 h
S
C6H5
CH3
9
LDA, −68 ◦C, 4 h
(CH3)3SiCl
B(OH)2
12
1: 2 t-BuLi, 0.5 h; 2: LDA, −68 ◦C, 4 h
27
S
C6H5
9c
Si(CH3)3
hydrolyzed with water (100 ml) and dilute aqueous H2SO4 to
reach a slightly acidic pH. The organic phase was separated and
the aqueous phase was extracted with Et2O (20 ml). The combined
organic solutions were next dried with MgSO4 and evaporated to
give a solid that was washed with water and recrystallized from
hexane (20 ml) to give 1e as colorless crystals, m.p. 112–114 ◦C;
1H-NMR (400 MHz, acetone-d6): δ 7.62 (d, Ar, J = 8.4 Hz, 2H), 7.39
(d, Ph, J = 8.4 Hz, 2H), 7.23 (t, Ph, J = 7.2 Hz, 2H), 7.18 (d, Ar,
J = 8.4 Hz, 2H), 7.08 (t, Ph, J = 7.2 Hz, 1H), 4.10 (s, S–C–H, 1H),
1
0.08 (s, CH3, 9H); 13C{ H} NMR (100.6 MHz, acetone-d6): 141.95
(C–Cbenzyl), 141.49 (C–S), 135.13 (C–C–B), 128.87 (Cmeta), 128.35
(Cortho), 126.77 (Cpara), 126.22 (C–C–S), 39.57 (H–C–S), −2.66
(CH3). Anal. calcd for C16H21BO2SSi: C, 60.76, H, 6.69; found: C,
61.11, H, 6.74.
Compound 1a: m.p. 127–129 ◦C; 1H-NMR (400 MHz, dmso-d6):
δ 7.73 (d, Ar, J = 8.4 Hz, 2H), 7.39 (d, Ar, J = 7.2 Hz, 2H), 7.29
(m, Ph, 4H), 7.20 (t, Ph, J = 7.2 Hz, 1H), 7.13 (s, OH), 4.60 (q,
1
S–C–H, J = 6.8 Hz, 1H), 1.59 (d, CH3, J = 6.8 Hz, 3H); 13C{ H} NMR
(100.6 MHz, dmso-d6): 143.08 (C–Cbenzyl), 137.84 (C–S), 134.67
(C–C–B), 128.63 (Cmeta), 128.52 (Cortho), 127.29 (Cpara), 126.44
(C–C–S), 45.18 (H–C–S), 22.47 (CH3). Anal. calcd for C14H15BO2S:
C, 65.14, H, 5.86; found: C, 65.31,◦H, 5.94.
Figure 1. ORTEP drawing of 9c with thermal ellipsoids plot (50% probabil-
ity). Hydrogen atoms were omitted for clarity. Selected bond lengths (Å)
and angles (deg): B–O1, 1.426(1); B–O1ꢁ, 1.293(1); B–C1, 1.594(1); C1–C2,
1.409(1); C3–Si, 1.899(9); O1–B–C1, 115.17 (7); O1ꢁ –B–C1, 125.84(9);
O1–B–C1–C2, −167.76(8); Si–C3–S–C4, −162.56(4); Si–C3–C2–C1,
89.74(9). Crystallographic data for this structure have been deposited with
the Cambridge Crystallographic Data Centre as supplementary publication
no. CCDC 805881.
Compound 1c: m.p. 210–212 C; 1H-NMR (400 MHz, dmso-d6): δ
7.94 (s, OH), 7.68 (d, Ar, J = 8.0 Hz, 2H), 7.49 (d, Ph, J = 7.2 Hz, 2H),
7.31 (t, Ph, J = 7.2 Hz, 2H), 7.25 (d, Ar, J = 8.0 Hz, 2H), 7.22 (t, Ph,
1
J = 7.2 Hz, 1H), 5.22 (s, S–C–H, 1H), 1.17 (s, CH3, 9H); 13C{ H} NMR
(100.6 MHz, dmso-d6): 167.91 (C O), 137.68 (C–Cbenzyl), 137.67
(C–S),134.59(C–C–B),128.38(Cmeta),128.14(Cortho),127.81(Cpara),
127.69 (C–C–S), 54.68 (S–C–H), 40.12 (C–CH3), 18.22 (CH3). Anal.
calcd for C18H22BNO3S: C, 62.98, H, 6.46, N, 4.08; found: C, 63.30, H,
6.54, N 3.92.
(H–C–S), 41.76 (C–N), 38.87 (C–N), 14.14 (CH3), 12.64 (CH3). Anal.
calcd for C18H22BNO3S: C, 62,98, H, 6.46, N, 4.08, Found: C, 63.44,
H, 6.12, N 3.43.
Compound 1d: m.p. 93–95 ◦C; 1H-NMR (400 MHz, acetone-
d6): δ 7.76 (d, Ar, J = 8.0 Hz, 2H), 7.55 (m, Ph, 2H), 7.33 (m,
1
Ar, Ph, 4H), 7.20 (m, Ph, 1H), 5.23 (s, S–C–H, 1H); 13C{ H} NMR
Typical Procedure for Lithiation of Lithium (Triiso-
propoxy)arylborates
(100.6 MHz, acetone-d6): 171.32 (C O), 138.03 (C–Cbenzyl), 137.13
(C–S),136.14(C–C–B),135.37(Cmeta),130.00(Cortho),129.30(Cpara),
128.88 (C–C–S), 55.45 (H–S–C). Anal. calcd for C14H13BO4S: C,
58.36, H, 4.55; found: C, 59.04, H, 4.59.
In a typical lithiation, 4-benzylthiobromobenzene 4 (1.39 g,
5 mmol) was added as a solid to the stirred solution of t-BuLi
(0.01 mol) in THF (30 ml) at −68 ◦C. The resultant slurry was stirred
for 1 h to form a yellow precipitate. B(OiPr)3 (0.94 g, 5 mmol)
was next added to the stirred slurry to form light-green solution.
After 1 h, the freshly prepared LDA (0.005 mol) in THF (20 ml) was
dropped to the stirred solution at −68 ◦C. The reaction mixture
was stirred at −68 ◦C for 2 h to form a yellow-brown solution.
Electrophile, Me3SiCl(0.54 g, 5 mmol)wasthenaddedviaasyringe
to form a colorless solution that was stirred overnight and then
Compound 2a: m.p. 97–98 ◦C; 1H-NMR (200 MHz, acetone-d6):
δ 7.93 (s, Ar,1H), 7.71 (d, Ar, J = 7.4 Hz 1H), 7.25 (m, Ar, Ph, 7H), 4.53
1
(q, S–C–H, J = 6.8 Hz, 1H), 1.61 (d, CH3, J = 6.8 Hz, 3H); 13C{ H}
NMR (100.6 MHz, acetone-d6): 143.12 (C–Cbenz), 136.58 (C–S),
133.94 (C–C–B), 133.24 (C–C–C–B), 132.21 (Cmeta), 130.21 (Cortho),
129.37 (Cpara), 128.34 (S–C–C–C–B), 127.51 (C–C–C–C–B), 47.97
(S–C–H), 22.80 (CH3). Anal. calcd for C14H15BO2S: C, 65.14, H, 5.86;
found: C, 65.43, H, 5.97.
c
Appl. Organometal. Chem. 2011, 25, 669–674
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K. Durka et al.
Compound 2e: m.p. 95–97 ◦C; 1H-NMR (200 MHz, acetone-d6):
δ 7.91 (s, Ar, 1H), 7.53 (d, Ar, J = 7.4 Hz 1H), 7.36 (d, Ph, J = 7.4 Hz,
2H), 7.21 (m, Ar, Ph, 3H), 7.07 (m, Ar, Ph, 2H), 4.04 (s, S–C–H, 1H),
(C–C–C–B), 127.49 (C–Cipso –C–B), 125.30 (Cortho), 125.01 (Cpara),
36.86 (S–C–H), −2.47 (CH3). Anal. calcd for C16H21BO2SSi: C, 60.76,
H, 6.69; found: C, 61.00, H, 6.74.
1
0.08 (s, CH3 9H); 13C{ H} NMR (100.6 MHz, acetone-d6): 141.06
(C–Cbenzyl), 136.23 (C–S), 134.62 (C–B), 133.21 (C–C–B), 131.06
(C–C–C–B), 128.80 (Cmeta), 128.14 (Cortho), 127.98 (Cpara), 127.50
(S–C–C–C–B), 125.48, 38.40 (S–C–H), −2.62 (CH3). Anal. calcd for
C16H21BO2SSi: C, 60.76, H, 6.69; found: C, 61.05, H, 6.75.
Crystal Data for 9c – Anhydride
Single crystal data were collected on a Kuma KM-4 CCD
diffractometer (Oxford Diffraction Ltd). The CRYSALISPRO program
was used for data collection, cell refinement, data reduction and
the empirical absorption corrections using spherical harmonics,
implemented in multi-scan scaling algorithm. The structure
was solved using direct methods, and refined with the full-
matrix least-squares technique using the SHELXS97 and SHELXL97
programs respectively.[18] C48H57B3O3S3Si3, MW = 894.84 a.u.,
hexagonal space group P3c, Dcalcd = 1.217 g cm−3, Z = 6,
a = b = 23.9673(7) Å, c = 14.7294(8) Å, α = 90.00◦, β = 90.00◦,
γ = 120.00◦, V = 7327.5(5) Å3, T = 100(2) K, Kuma KM-4 CCD
diffractometer,λ(Mo/Kα)=0.71073 Å,µ = 0.265 mm−1.Of55 706
reflectionsmeasured,8935wereunique(Rint = 0.102).Refinement
on F2 concluded with the values R1 = 0.0860 and wR2 = 0.1500
for 572 parameters (221 restrains) and 6052 data with I > 2δI.
Compound 3a: m.p. 74–76 ◦C; 1H-NMR (400 MHz, acetone-d6):
δ 7.57 (m, Ar, J = 7.2 Hz, 1H), 7.53 (d, Ar, J = 7.2 Hz, 1H), 7.36
(m, Ar, Ph, 4H), 7.23 (m, Ph, 2H), 7.19 (m, Ph, 1H), 5.34 (q, S–C–H,
1
J = 6.8 Hz, 1H), 1.59 (d, CH3, J = 6.8 Hz, 3H); 13C{ H} NMR
(100.6 MHz, acetone-d6): 146.13(C–Cbenzyl), 136.21 (C–S), 135.27
(C–C–B), 134.75 (C–C–C–B), 132.57 (Cmeta), 132.33 (Cortho), 129.43
(Cpara), 127.61(C–C–S), 127.34 (C–Cipso –C–B), 47.82 (S–C–H),
22.61 (CH3). Anal. calcd for C14H15BO2S: C, 65.14, H, 5.86; found: C,
65.44, H, 5.96.
Compound 7a: m.p. 94–96 ◦C; 1H-NMR (200 MHz, acetone-d6):
δ 7.78 (d, Ar, J = 8.0 Hz, 2H), 7.32 (m, Ar, Ph, 7H), 4.51 (q, S–C–H,
1
J = 6.8 Hz, 1H), 1.56 (d, CH3, J = 6.8 Hz, 3H); 13C{ H} NMR
(100.6 MHz, acetone-d6): 146.23 (C–Cbenzyl), 136.27 (C–S), 135.07
(C–C–B), 132.30 (Cmeta), 129.56 (C–C–C–B), 127.60 (Cortho), 127.18
(Cpara), 47.82 (S–C–H), 22.61 (CH3). Anal. calcd for C14H15BO2S: C,
65.14, H, 5.86; found: C, 65.64, H, 5.98.
Acknowledgments
Compound 7b: m.p. 152–154 ◦C; 1H-NMR (400 MHz, dmso-d6):
δ 8.03 (s, OH), 7.66 (d, Ar, J = 8.4 Hz, 2H), 7.33 (d, Ar, J = 8.4 Hz,
2H), 7.23 (m, Ph, 5H), 5.50 (s, S–C–H, 1H), 3.32 (dq, CH2, J = 7.2 Hz,
J = 15 Hz, 2H), 3.23 (dq, CH2, J = 7.2 Hz, J = 15 Hz, 2H), 0.94 (t,
This work was supported by the Warsaw University of Technology.
The X-ray measurements of compound 9c were undertaken at
the Crystallographic Unit of the Physical Chemistry Laboratory,
ChemistryDepartment,UniversityofWarsaw.SupportfromAldrich
Chemical Company, Milwaukee, WI, USA, through the donation of
chemicals and equipment, is gratefully acknowledged.
1
CH3, J = 7.2 Hz, 3H), 0.83 (t, CH3, J = 7.2 Hz, 3H); 13C{ H} NMR
(100.6 MHz, dmso-d6): 167.50 (C O), 139.35 (C–Cbenzyl), 134.17
(C–S), 131.23 (C–C–B), 128.86 (Cmeta), 128.25 (C–C–C–B), 127.37
(Cortho), 127.10 (Cpara), 53.82 (S–C–H), 41.74 (CH2), 38.87 (CH2),
14.12 (CH3), 12.65 (CH3). Anal. calcd for C18H22BNO3S: C, 62,98, H,
6.46, N, 4.08; found: C, 63.16, H, 6.52, N, 3.88.
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Compound 8a: m.p. 97–98 ◦C; 1H-NMR (200 MHz, acetone-d6):
δ 7.91 (s, Ar, 1H), 7.72 (d, Ar, J = 7.4 Hz 1H), 7.30 (m, Ar, Ph, 7H), 4.51
1
(q, S–C–H, J = 6.8 Hz, 1H), 1.57 (d, CH3, J = 6.8 Hz, 3H); 13C{ H}
NMR (100.6 MHz, acetone-d6): 143.02 (C–Cbenzyl), 136.50 (C–S),
133.89 (C–C–B), 133.79 (Cipso –C–C–B), 132.20 (Cmeta), 130.01
(C–C–C–B), 129.57 (C–C–C–C–B), 128.28 (Cortho), 127.53 (Cpara),
47.91 (S–C–H), 22.77 (CH3). Anal. calcd for C14H15BO2S: C, 65.14,
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δ 7.58 (d, Ar, J = 7.2 Hz, 1H), 7.51 (d, Ar, J = 7.2 Hz, 1H),
7.33 (m, Ar, Ph, 4H), 7.23 (m, Ph, 2H), 7.16 (m, Ph, 1H), 5.39 (q,
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1
S–C–H, J = 6.8 Hz, 1H), 1.53 (d, CH3, J = 6.8 Hz, 3H); 13C{ H}
NMR (100.6 MHz, dmso-d6): 146.44 (C–Cbenzyl), 135.92 (C–S),
133.72 (C–C–B), 130.35 (Cmeta), 129.37 (C–C–C–C–B), 129.15
(C–C–C–B), 126.67 (C–Cipso –C–B), 126.17 (Cortho), 125.76 (Cpara),
44.88 (S–C–H), 22.63 (CH3). Anal. calcd for C14H15BO2S: C, 65.14,
H, 5.86; found: C, 65.54, H, 5.98.
◦
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1
Compound 9c: m.p. 130–132 C; H-NMR (400 MHz, acetone-
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1H), 7.50 (dt, Ar, J = 7.6 Hz, J = 1.6 Hz, 1H), 7.41 (m, Ph, 2H),
7.15 (m, Ph, 2H), 7.08 (m, Ph, 1H), 7.03 (dt, Ar, J = 7.6 Hz,
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1
J = 0.8 Hz, 1H), 5.64 (s, S–C–H, 1H), 0.03 (s, CH3, 9H); 13C{ H}
NMR (100.6 MHz, acetone-d6): 147.99 (C–Cbenzyl), 139.68 (C–S),
135.37 (C–C–B), 130.59 (Cmeta), 129.20 (C–C–C–C–B), 127.57
c
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Appl. Organometal. Chem. 2011, 25, 669–674