Synthesis and catalysed hydroboration of styryl sulfonamides

Article abstract of DOI:10.1139/v05-078

We have prepared the aryl sulfonamides 4,4′-R-C₆H ₄SO₂NHC₆H₄CH=CH₂ (R = CH₃, 1a; NO₂, 1b) by addition of 2 equiv. of 4-vinylaniline to the corresponding sulfonyl chlor

Full text of DOI:10.1139/v05-078

661
Synthesis and catalysed hydroboration of styryl
sulfonamides1
Natalie A. Wynberg, Lisa J. Leger, Maren L. Conrad, Christopher M. Vogels,
Andreas Decken, Stephen J. Duffy, and Stephen A. Westcott
Abstract: We have prepared the aryl sulfonamides 4,4′-R-C6H4SO2NHC6H4CH=CH2 (R = CH3, 1a; NO2, 1b) by
addition of 2 equiv. of 4-vinylaniline to the corresponding sulfonyl chlorides. The disulfonamides 4,4,4′-(R-C6H4SO2)2-
NC6H4CH=CH2 (R = CH3, 2a; NO2, 2b) were also prepared using 4-vinylaniline and 2 equiv. of the sulfonyl chlorides
in the presence of DMAP. Although hydroborations of sulfanilamide derivatives 1 suffered from competing hydrogena-
tion reactions, judicious choice of the transition metal catalyst gave selective formation of either the primary or second-
ary boronate esters in hydroborations of 2a.
Key words: boronate esters, catalysed hydroborations, sulfanilamides, vinylaniline.
Résumé : On a préparé les aryl sulfonamides, 4,4′-R-C6H4SO2NHC6H4CH=CH2 (R = CH3, 1a; NO2, 1b) par l’addition
de deux équivalents de 4-vinylaniline aux chlorures de sulfonyle correspondants. On a aussi préparé les disulfonamides
4,4,4′-(R-C6H4SO2)2NC6H4CH=CH2 (R = CH3, 2a; NO2, 2b) à partir de la 4-vinylaniline et de deux équivalents de
chlorures de sulfonyle, en présence de DMAP. Quoique les réactions d’hydroboration des dérivés sulfanilamides 1 soient
en compétition avec les réactions d’hydrogénation, un choix judicieux d’un catalyseur à base d’un métal de transition
permet d’obtenir la formation sélective des boronates soit primaires ou secondaires lors des hydroborations du composé 2a.
Mots clés : esters de l’acide boronique, hydroborations catalysées, sulfanilamides, vinylaniline.
[Traduit par la Rédaction] Wynberg et al.
Introduction
catalysed hydroborations are the most common and syntheti-
cally useful of these reactions. They are believed to proceed
via initial oxidative addition of HBcat (7), followed by coor-
dination of the alkene to the metal centre with subsequent
insertion of the alkene into either the Rh—H (8) or the Rh—
B bond (9) and reductive elimination to yield the desired
product (10). The unusual secondary boronate ester product
is believed to arise when the metal centre can best stabilize a
benzylic intermediate during the catalytic cycle.
Although a considerable amount of research has focused
on the catalysed hydroboration of simple unsaturated hydro-
carbon systems, much less is known about analogous reac-
tions with heteroatom-containing substrates (3, 11–17). For
instance, catalysed hydroborations of pyrrolidinyl amides
with HBcat gave, after oxidation, syn 1,3-hydroxy amides
with high levels of regio- and stereochemical control (18).
The remarkable selectivities observed in these reactions are
believed to arise from a directing effect of the amide moiety.
As part of our ongoing investigation into generating biologi-
cally active boron compounds (19) and, in an effort to
expand the scope of metal-catalysed hydroborations, we de-
The hydroboration of alkenes and alkynes, which consti-
tutes the addition of a B—H bond across a carbon—carbon
multiple bond, is a remarkably important reaction in organic
synthesis (1). Although simple boron hydride reagents such
as borane (H3B·X, where X is a Lewis base) and 9-
borabicyclo[3.3.1]nonane react readily with alkenes at room
temperature, hydroborations with catecholborane (HBcat,
cat = 1,2-O2C6H4) generally require elevated temperatures.
The discovery that transition metals can be used to catalyse
the addition of HBcat to substrates has become an important
and well-established technique in organic synthesis (2–6).
These reactions can have regio-, chemo-, or stereoselectiv-
ities complementary, or more remarkably, opposite to those
from products obtained via the uncatalysed variant. For ex-
ample, hydroborations of styrenes (ArCH=CH2) with HBcat
proceed to give selectively either the expected primary bor-
onate ester (ArCH2CH2Bcat) or the secondary boronate ester
(ArCH(Bcat)CH3), depending upon the choice of catalyst
used to affect this transformation (Scheme 1) (3). Rhodium-
Received 10 December 2004. Published on the NRC Research Press Web site at http://canjchem.nrc.ca on 8 June 2005.
Dedicated to Professor Howard Alper in recognition of his outstanding contributions in catalysis.
N.A. Wynberg, L.J. Leger, M.L. Conrad, C.M. Vogels, S.J. Duffy, and S.A. Westcott.2 Department of Chemistry, Mount
Allison University, Sackville, NB E4L 1G8, Canada.
A. Decken.3 Department of Chemistry, University of New Brunswick, Fredericton, NB E3B 5A3, Canada.
1This article is part of a Special Issue dedicated to Professor Howard Alper.
2Corresponding author (e-mail: swestcott@mta.ca).
3Corresponding author (crystallography) (e-mail: adecken@unb.ca).
Can. J. Chem. 83: 661–667 (2005)
doi: 10.1139/V05-078
© 2005 NRC Canada

662
Can. J. Chem. Vol. 83, 2005
Scheme 1.
O
H
5 mol %
[Cp*IrCl2]2
B
O
O
+
HB
O
O
O
HBcat
B
5 mol %
Rh(acac)(dppe)
H
cided to examine the synthesis and hydroboration of sulfa-
nilamide derivatives containing a pendant styryl moiety.
Initial results are presented herein.
pounds 1a and 1b were recovered upon removal of solvent
under vacuum and washed with hexane (3 × 3 mL).
Compound 1a
1
Yield: 70%, mp 80–82 °C. H NMR (CDCl3) δ: 7.65 (d,
Experimental
J = 8 Hz, 2H, Ar), 7.26 (d, J = 8 Hz, 2H, Ar), 7.21 (d, J =
8 Hz, 2H, Ar), 7.01 (d, J = 8 Hz, 2H, Ar), 6.76 (br s, 1H,
NH), 6.60 (d of d, J = 18, 10 Hz, 1H, CH=CH2), 5.64 (d, J =
18 Hz, 1H, CH=CHH), 5.18 (d, J = 10 Hz, 1H, CH=CHH),
2.36 (s, 3H, CH3). 13C NMR (CDCl3) δ: 144.0, 136.1, 136.0,
135.9, 134.9, 129.7, 127.3, 127.2, 121.7, 113.8, 21.6. IR
(Nujol): 3271, 2943, 2922, 1597, 1508, 1392, 1333, 1159,
1090, 906, 814, 681, 492. EI-MS m/z (relative intensity):
273 (73, [M]+), 155 (5), 118 (100), 91 (58).
Materials and methods
Reagents and solvents used were obtained from Aldrich
Chemicals. RhCl(PPh3)3 (20), Rh(acac)(coe)2 (21), and
[Cp*IrCl2]2 (22) were prepared as described elsewhere.
NMR spectra were recorded on a JEOL JNM-GSX270 FT
1
NMR spectrometer. H NMR chemical shifts are reported in
parts per million (ppm) and are referenced to residual pro-
tons in deuterated solvent at 270 MHz. 11B NMR chemical
shifts are referenced to external BF3·OEt2 at 87 MHz. 13C
NMR chemical shifts are referenced to solvent carbon reso-
nances as internal standards at 68 MHz. Multiplicities are re-
ported as singlet (s), doublet (d), triplet (t), quartet (q),
multiplet (m), broad (br), and overlapping (ov). Infrared
spectra were obtained using a Mattson Genesis II FT-IR
spectrometer and are reported in cm–1. Melting points were
measured uncorrected with a Mel-Temp apparatus. GC-MS
analyses were conducted using a Varian Saturn 2000
GC/MS/MS coupled to a CP-3800 GC. The GC was
equipped with both the 1177 injection port with a CP-8410
liquid autoinjector connected to an SPB-1 (Supelco) fused
silica column (30 m × 0.25 mm i.d. × 0.25 µm) and the 1079
solid injector chromatoprobe, attached to a 50 cm transfer
line. The GC-MS spectrometer is controlled by the Saturn
Workstation software, Version 5.51.
Compound 1b
1
Yield: 60%, mp 182–184 °C. H NMR (DMSO-d6) δ:
10.68 (br s, 1H, NH), 8.37 (d, J = 8 Hz, 2H, Ar), 7.99 (d,
J = 8 Hz, 2H, Ar), 7.36 (d, J = 8 Hz, 2H, Ar), 7.08 (d, J =
8 Hz, 2H, Ar), 6.58 (d of d, J = 18, 10 Hz, 1H, CH=CH2),
5.71 (d, J = 18 Hz, 1H, CH=CHH), 5.17 (d, J = 10 Hz, 1H,
CH=CHH). 13C NMR (DMSO-d6) δ: 150.4, 145.4, 137.0,
136.3, 134.3, 128.8, 127.7, 125.2, 121.2, 114.4. IR (Nujol):
3224, 2935, 2912, 1606, 1527, 1348, 1165, 1086, 924, 854,
735, 604, 542. EI-MS m/z (relative intensity): 304 (41, [M]+),
118 (100).
Reaction of 1a with 1 equiv. of HBcat in the presence
of RhCl(PPh3)3
Under an atmosphere of dinitrogen, a 0.5 mL C6D6 solu-
tion of HBcat (1 equiv.) was added to a mixture of 1a and
RhCl(PPh3)3 (0.05 equiv.) in 0.5 mL of C6D6. The reaction
was allowed to proceed for 4 h, at which point NMR spec-
Synthesis
1
troscopic data was collected. H NMR δ: 7.92 (d, J = 8 Hz,
2H, Ar), 7.00 (d, J = 8 Hz, 2H, Ar), 6.96–6.82 (ov m, 4H,
Ar and Bcat), 6.70–6.64 (ov m, 4H, Ar and Bcat), 2.31 (q,
J = 8 Hz, 2H, CH2CH3), 1.82 (s, 3H, CH3), 0.94 (t, J = 8 Hz,
3H, CH2CH3). 11B NMR δ: 24.8 (ArSO2N(Bcat)CH2CH3).
General synthesis of 1a and 1b
Under an atmosphere of dinitrogen, an Et2O (2 mL) solu-
tion of 4-vinylaniline (2 equiv.) was added dropwise to a
stirred Et2O (5 mL) solution of the appropriate sulfonyl
chloride. The mixture was allowed to stir for 18 h, at which
point the resulting solid was removed by filtration and the
filtrate stored at –30 °C for 2 days. Any subsequent precipi-
tate was also removed by filtration and discarded. Com-
Reaction of 1b with 1 equiv. of HBcat in the presence
of RhCl(PPh3)3
Under an atmosphere of dinitrogen, a 0.5 mL CDCl3 solu-
© 2005 NRC Canada

Wynberg et al.
663
tion of HBcat (1 equiv.) was added to a suspension of 1b
and RhCl(PPh3)3 (0.05 equiv.) in 0.5 mL of CDCl3. The re-
action was allowed to proceed for 18 h, at which point spec-
troscopic NMR data of the resulting hydrogenation product
(ArN(Bcat)CH2CH3, 98% by NMR spectroscopy) was col-
145.0, 136.8, 132.2, 131.5, 129.6, 128.8, 128.7, 122.7,
112.4, 29.4, 21.8, 12.1 (br, C-B). 11B NMR (CDCl3) δ: 34.8.
EI-MS m/z (relative intensity): 547 (12, [M]+), 429 (100),
273 (68), 155 (8), 118 (33).
1
Compound 4
lected. H NMR δ: 8.21 (d, J = 8 Hz, 2H, Ar), 7.93 (d, J =
1H NMR (CDCl3) δ: 7.81 (d, J = 8 Hz, 4H, Ar), 7.31 (d,
J = 8 Hz, 4H, Ar), 7.30 (d, J = 8 Hz, 2H, Ar), 7.22 (2nd or-
der m, 2H, Bcat), 7.09 (2nd order m, 2H, Bcat), 6.96 (d, J =
8 Hz, 2H, Ar), 3.01 (q, J = 8 Hz, 1H, CH(Bcat)CH3), 2.45
(s, 6H, CH3), 1.58 (d, J = 8 Hz, 3H, CH(Bcat)CH3). 13C
NMR (CDCl3) δ: 148.2, 145.7, 145.0, 136.9, 132.0, 131.6,
129.6, 128.7, 128.6, 122.9, 112.6, 24.8 (br, C-B), 21.8, 16.6.
11B NMR (CDCl3) δ: 34.1. EI-MS m/z (relative intensity):
547 (2, [M]+), 428 (18), 246 (100), 155 (8), 118 (16).
8 Hz, 2H, Ar), 7.24–7.04 (ov m, 8H, Ar and Bcat), 2.56 (q,
J = 8 Hz, 2H, CH2CH3), 1.16 (t, J = 8 Hz, 3H, CH2CH3).
11B NMR δ: 24.5 (ArN(Bcat)CH2CH3).
General synthesis of 2a and 2b
Under an atmosphere of dinitrogen, a toluene (2 mL) so-
lution of 4-vinylaniline was added dropwise to a stirred tolu-
ene (5 mL) mixture of the appropriate sulfonyl chloride
(2.5 equiv.) and 4-DMAP (2.5 equiv.). The mixture was
heated at reflux for 2 days, at which point solvent was re-
moved under vacuum, and the resultant white solid was
washed with Et2O (3 × 5 mL). The filtrate was collected,
and the Et2O was removed under vacuum. The resulting
solid was then washed with EtOH (4 × 5 mL) to afford 2.
X-ray data
Crystals of 3 were grown by slow evaporation using
CHCl3 at –30 °C. Crystals were coated with Paratone-N oil,
mounted using a glass fibre, and frozen in the cold nitrogen
stream of the goniometer. A hemisphere of data was col-
lected on a Bruker AXS P4/SMART 1000 diffractometer us-
ing ω and θ scans with a scan width of 0.3° and with 90 s
exposure times. The detector distance was 6 cm. The crystal
was twinned, and the orientation matrixes for two compo-
nents were determined (23, 24), and the data were reduced
(25). The structure was solved by direct methods and refined
by full-matrix least squares on F2 (SHELXTL) (26) using all
reflections. One of the ethyl linkages was disordered, and
the site occupancy was determined using an isotropic model
as 0.7 (C(41)—C(42)) and 0.3 (C(41′)—C(42′)) and was
fixed in subsequent refinement cycles. All non-hydrogen at-
oms were refined anisotropically. Hydrogen atoms were in-
cluded in calculated positions and refined using a riding
model.
Compound 2a
Yield: 70%, mp 176–178 °C. 1H NMR (CDCl3) δ: 7.81 (d,
J = 8 Hz, 4H, Ar), 7.36 (d, J = 8 Hz, 2H, Ar), 7.32 (d, J =
8 Hz, 4H, Ar), 6.97 (d, J = 8 Hz, 2H, Ar), 6.69 (d of d, J =
18, 10 Hz, 1H, CH=CH2), 5.77 (d, J = 18 Hz, 1H,
CH=CHH), 5.33 (d, J = 10 Hz, 1H, CH=CHH), 2.45 (s, 6H,
CH3). 13C NMR (CDCl3) δ: 145.1, 139.5, 136.7, 135.8,
133.6, 131.7, 129.7, 128.7, 127.0, 116.1, 21.8. IR (Nujol):
2970, 2951, 1595, 1462, 1377, 1167, 908, 806, 661, 550,
488. EI-MS m/z (relative intensity): 427 (98, [M]+), 272
(53), 208 (100), 155 (13), 118 (16), 91 (20).
Compound 2b
1
Yield: 55%, mp 274 to 275 °C. H NMR (DMSO-d6) δ:
8.51 (d, J = 8 Hz, 4H, Ar), 8.12 (d, J = 8 Hz, 4H, Ar), 7.59
(d, J = 8 Hz, 2H, Ar), 7.10 (d, J = 8 Hz, 2H, Ar), 6.80 (d of
d, J = 18, 10 Hz, 1H, CH=CH2), 5.96 (d, J = 18 Hz, 1H,
CH=CHH), 5.42 (d, J = 10 Hz, 1H, CH=CHH). 13C NMR
(DMSO-d6) δ: 151.5, 143.6, 140.3, 135.8, 132.2, 132.1,
130.4, 128.1, 125.6, 117.9. IR (Nujol): 2935, 2902, 2863,
1710, 1531, 1462, 1377, 1169, 1082, 960, 920, 852, 733,
642, 602, 552. EI-MS m/z (relative intensity): 489 (2, [M]+),
304 (57), 273 (3), 118 (100).
Results and discussion
N-Aryl sulfonamides are an important class of com-
pounds, particularly in pharmaceutical research (27), where
a number of these compounds have been reported to act as
class III antiarrhythmic agents (28), non-nucleotide reverse
transcriptase inhibitors (29), and as HIV-1 protease inhibi-
tors (30). We have recently undertaken a study to investigate
the synthesis and biological activity of novel borosulfon-
amides (31, 32). Interest in compounds containing boronic
acids (RB(OH)2) or boronate esters (RB(OR′)2) arises from
their remarkable versatility in organic synthesis (33), as well
as from their potent biological activities (34–42). For in-
stance, the boron compounds boromycin and aplasmomycin
are powerful antibiotics, and L-4-borono-phenylalanine has
found significant application in boron neutron capture ther-
apy for the treatment of certain cancers (43). These proper-
ties, along with their ability to transport water-insoluble
reagents through membranes (44), make boronate ester com-
pounds useful carrier ligands for biologically active com-
pounds.
General procedure for the hydroboration of compounds
3 and 4
Under an atmosphere of dinitrogen, 1 equiv. of catechol-
borane in 0.5 mL of CDCl3 was added to a 0.5 mL CDCl3
solution of the appropriate catalyst and substrate. The reac-
tions were allowed to proceed for 18 h, at which point NMR
data were collected. Compounds 3 and 4 were isolated by
recrystallization from a solution of CDCl3:hexane (1:2)
stored at –30 °C.
Compound 3
1H NMR (CDCl3) δ: 7.79 (d, J = 8 Hz, 4H, Ar), 7.29 (d,
J = 8 Hz, 4H, Ar), 7.25–7.20 (ov m, 4H, Ar and Bcat), 7.08
(2nd order m, 2H, Bcat), 6.92 (d, J = 8 Hz, 2H, Ar), 2.99 (t,
J = 8 Hz, 2H, CH2CH2Bcat), 2.44 (s, 6H, CH3), 1.66 (t, J =
8 Hz, 2H, CH2CH2Bcat). 13C NMR (CDCl3) δ: 148.2, 146.0,
In this study, we have prepared the novel aryl sulfona-
mides 4,4′-R-C6H4SO2NHC6H4CH=CH2 (R = CH3, 1a;
NO2, 1b) (Fig. 1) by addition of 2 equiv. of 4-vinylaniline to
the corresponding sulfonyl chlorides. Varying the physical
© 2005 NRC Canada

664
Can. J. Chem. Vol. 83, 2005
Scheme 2.
O
B
O
S
2
O
S
2
O
N
H
O
O
N
[cat.]
+
+
H
BH
2
R
R
O
B
O
S
2
[cat.]
O
N
R = CH , NO
3
R
2
O
O
S
2
B
O
N
R
Fig. 1. Styryl sulfanilamides.
Scheme 3.
O
S
2
R'
N
Ir
Cl
L
HBcat
R
ClBcat
H
Ir
Ir
L
Bcat
R
1a: R = CH3, R' = H
1b: R = NO2, R' = H
2a: R = CH3, R' =4-SO2C6H4CH3
2b: R = NO2, R' =4-SO2C6H4NO2
HBcat
R
L
and electronic properties of the sulfonyl chlorides will allow
for the general synthesis of a wide variety of styryl sulfanil-
amide derivatives. Unfortunately, we have found that metal-
catalysed addition of 1.1 equiv. of HBcat to styryl sulfona-
R
The novel disulfonamides 4,4,4′-(R-C6H4SO2)2NC6H4-
CH=CH2 (R = CH3, 2a; NO2, 2b) could be prepared in mod-
erate to good yields using 4-vinylaniline and 2.5 equiv. of
the sulfonyl chlorides in the presence of excess DMAP.
However, the introduction of a second nitrobenzene group in
2b made this sulfonamide derivative insoluble in non-
coordinating organic solvents, and as a result, hydroboration
studies could not be conducted on this substrate. Addition of
HBcat to 2a using the iridium catalyst [Cp*IrCl2]2 (45) pro-
ceeded smoothly to give the expected primary boronate ester
product 3 in high yields (by multinuclear NMR spectros-
copy), along with minor amounts (<5%) of the correspond-
ing hydrogenation product. A small amount of hydrogenated
alkene, arising from the degradation of HBcat, is almost al-
ways observed in reactions using a late metal catalyst (46).
Although it is possible that reactions using this catalyst pre-
cursor proceed via an oxidative addition mechanism, similar
1
mides 1a and 1b gave significant amounts (>95% by H
NMR spectroscopy) of hydrogenation products R-
C6H4SO2N(Bcat)C6H4CH2CH3 (R = CH3 or NO2). These
products presumably arise as a result of an initial interaction
of the borane with the sulfonamide N—H bond to generate a
new N—Bcat bond while liberating dihydrogen, which can
subsequently add to the styryl group in the presence of a cat-
alyst (Scheme 2). Indeed, a new N—B resonance is ob-
served in the 11B NMR spectra at 25 ppm. Furthermore,
reactions with excess HBcat gave a complicated mixture of
products arising from competing hydrogenation and (or)
hydroboration reactions, regardless of the catalyst used to af-
fect these transformations. We therefore investigated the
analogous reactions of sulfonamides 2, which do not contain
an active N—H bond.
© 2005 NRC Canada

Wynberg et al.
665
Scheme 4.
N(SO2R)2
5 mol %
[Cp*IrCl2]2
catB
N(SO2R)2
3
O
+
HB
O
N(SO2R)2
HBcat
5 mol %
Rh(acac)(dppe)
2a: R = 4-C6H4CH3
Bcat
4
Fig. 2. Molecular structure of 3 with displacement ellipsoids drawn at the 30% probability level. Solvent molecule and hydrogen atoms
omitted for clarity.
to those purported for reactions using rhodium-based cata-
lysts, it is also possible that these reactions may be occurring
via a σ-bond metathesis pathway to give 3 (Scheme 3). This
reaction could proceed via initial metathesis of an Ir—Cl
bond with HBcat to give a transient iridium hydride species.
The formation of Ir-H species in hydroborations using
HBcat has been reported previously (45). Subsequent inser-
tion of the alkene into the Ir—H bond, followed by a σ-bond
metathesis with HBcat would give the primary boronate es-
ter while regenerating the active Ir-H catalyst. A similar
mechanism has been proposed for reactions of HBcat using
early metal and lanthanide catalysts (47). The iridium-
catalysed hydroboration of alkenes using pinacolborane is
also known to give the corresponding primary boronate ester
products (48, 49).
Selective formation of the unusual secondary boronate es-
ter 4 could be achieved in these reactions using either
RhCl(PPh3)3 or Rh(acac)(dppe) (acac = acetylacetonato,
dppe = 1,2-bis(diphenylphosphino)ethane) as the catalyst
precursor (Scheme 4). The latter is a very active and selec-
tive catalyst precursor for a wide range of alkenes, where the
resting state of the catalytically active species is the zwitteri-
onic complex, Rh(dppe)(η6-catBcat) (50). Compounds 3 and
4 have been characterized using a number of physical tech-
niques, including multinuclear NMR spectroscopy. A broad
peak at approximately δ 30 ppm in the 11B NMR spectra is
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666
Can. J. Chem. Vol. 83, 2005
Table 2. Selected bond lengths (Å) and angles
Table 1. Crystallographic data collection parameters for 3.
(°) for 3.
Complex
Formula
3
Bond lengths (Å)
C(1)—C(2)
C28H26BNO6S2·1/2CHCl3
1.517(5)
1.562(6)
1.687(3)
1.688(3)
1.423(2)
1.434(2)
1.752(3)
1.432(2)
1.435(2)
1.756(3)
1.389(5)
1.402(5)
1.383(4)
1.399(4)
Formula mass
Crystal system
Space group
a (Å)
b (Å)
c (Å)
607.11
Triclinic
P1
C(1)—B(30)
N(9)—S(10)
N(9)—S(20)
S(10)—O(12)
S(10)—O(11)
S(10)—C(13)
S(20)—O(21)
S(20)—O(22)
S(20)—C(23)
B(30)—O(31)
B(30)—O(38)
O(31)—C(32)
O(38)—C(37)
8.291 5(12)
18.403(3)
19.051(3)
80.093(2)
87.942(2)
84.195(2)
2 848.5(7)
4
α (°)
β (°)
γ (°)
V (Å3)
Z
ρcalcd (mg m–3)
1.416
Crystal size (mm3)
Temperature (K)
Radiation
0.4 × 0.075 × 0.050
173(1)
Mo Kα (λ = 0.710 73)
0.372
18 974
18 974
Bond angles (°)
C(6)-N(9)-S(10)
C(6)-N(9)-S(20)
S(10)-N(9)-S(20)
O(12)-S(10)-O(11)
O(12)-S(10)-N(9)
O(11)-S(10)-N(9)
O(12)-S(10)-C(13)
O(11)-S(10)-C(13)
N(9)-S(10)-C(13)
O(21)-S(20)-O(22)
O(21)-S(20)-N(9)
O(22)-S(20)-N(9)
O(21)-S(20)-C(23)
O(22)-S(20)-C(23)
N(9)-S(20)-C(23)
O(31)-B(30)-O(38)
O(31)-B(30)-C(1)
O(38)-B(30)-C(1)
C(32)-O(31)-B(30)
C(2)-C(1)-B(30)
µ (mm–1)
117.4(2)
120.1(2)
Total reflections
Total unique reflections
No. of variables
Theta range (°)
Largest difference peak and hole
(e Å–3)
122.46(16)
119.98(15)
106.00(15)
106.47(15)
109.98(15)
108.24(16)
105.14(16)
119.64(17)
104.04(14)
108.98(14)
109.36(15)
109.81(16)
103.72(16)
111.2(3)
752
1.43–25.00
1.104 and –0.725
S (GoF) on F2
0.835
0.056 9
a
R1 (I > 2σ(I))
b
wR2 (all data)
0.143 5
aR1 = Σ|(|Fo| – |Fc|)|/ΣFo|.
bwR2 = (Σ[w(Fo – Fc2)2]/Σ[wFo ])1/2, where w = 1/[σ2(Fo ) +
2
4
2
(0.0638P)2], where P = (max (Fo , 0) + 2Fc2)/3.
2
observed for both sulfonamides, indicating that the boron
atom lies in a three-coordinate C-Bcat environment (51).
Compound 3 has also been characterized by a single crystal
diffraction study, and the molecular structure is shown in
Fig. 2;4 crystallographic data are given in Table 1, and se-
lected bond distances and angles are shown in Table 2. The
B—O bond distances (avg. = 1.3955(5) Å) are also typical
for three-coordinate Bcat groups (52–55) and are signifi-
cantly shorter than those observed in chelate complexes with
diphenylborinic acid (ca. 1.5 Å), where the boron atom is
four coordinate (56).
125.9(4)
122.8(4)
104.7(3)
113.4(4)
ing boron-containing derivatives, the results of which will be
presented in due course.
In summary, we have prepared novel sulfanilamide deriva-
tives containing styryl groups and have examined metal-
catalysed hydroborations of these substrates using HBcat.
Judicious choice of the catalyst precursor used to affect
these transformations allows for the selective generation of
either the primary or secondary boronate ester. Preliminary
work has shown that these reactions are general, as analo-
gous compounds could be obtained in metal-catalysed
hydroborations of thiophene sulfonamide derivatives. Future
work will investigate the potential biological activities of a
wide range of novel styryl sulfonamides and the correspond-
Acknowledgements
Thanks are gratefully extended to the American Chemical
Society – Petroleum Research Fund (Grant #37824-B1),
Canada Research Chairs Programme, Canadian Foundation
for Innovation – Atlantic Innovation Fund, Natural Sciences
and Engineering Research Council of Canada (NSERC), and
Mount Allison University for financial support. We also
thank Dan Durant and Roger Smith for their expert technical
assistance and anonymous reviewers for helpful comments.
4 Supplementary data for this article are available on the Web site or may be purchased from the Depository of Unpublished Data, Document
Delivery, CISTI, National Research Council Canada, Ottawa, ON K1A 0S2, Canada. DUD 3675. For more information on obtaining mate-
rial refer to http://cisti-icist.nrc-cnrc.gc.ca/irm/unpub_e.shtml. CCDC 256413 contains the crystallographic data for this manuscript. These
data can be obtained, free of charge, via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Centre,
12 Union Road, Cambridge CB2 1EZ, UK; fax +44 1223 336033; or deposit@ccdc.cam.ac.uk).
© 2005 NRC Canada

Wynberg et al.
667
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