Facile synthesis of 4-substituted 3,4-dihydro-1H-2,1,3-benzothiadiazine 2,2-dioxides

Article abstract of DOI:10.1002/hc.20670

A new method for the preparation of 4-substituted 3,4-dihydro-1H-2,1,3- benzothiadiazine 2,2-dioxides is described. Treatment of t-butyl N-phenylsulfamoylcarbamate derivatives (1) with different aldehydes afforded the corresponding intramolecular cyclized

Full text of DOI:10.1002/hc.20670

Heteroatom Chemistry
Volume 22, Number 2, 2011
Facile Synthesis of 4-Substituted
3,4-Dihydro-1H-2,1,3-Benzothiadiazine
2,2-Dioxides
Chai-Ho Lee,1 Guo Fan Jin,1 Hyun Wha Lim,1 Eun Hye Yang,1
Jong-Dae Lee,2 Hiroyuki Nakamura,3 Hyun Seung Ban,3 and
Sang Ook Kang4
1Department of Chemistry and Institute of Basic Natural Science, Wonkwang University,
Jeonbuk 570-749, Korea
2Department of Chemistry, College of Natural Science, Chosun University, Gwangju 501-759, Korea
3Department of Chemistry, Gakushuin University, Toshima, Tokyo 171-8588, Japan
4Department of Advanced Materials Chemistry, Korea University, Sejong Campus,
Chungnam 339-700, Korea
Received 31 October 2010
biological properties. For instance, diazoxide has
ABSTRACT: A new method for the preparation of
been shown to produce muscle relaxation [2] and
4-substituted 3,4-dihydro-1H-2,1,3-benzothiadiazine
bentazone is a potent herbicide [3]. Other members
2,2-dioxides is described. Treatment of t-butyl N-
of this family show antihypertensive and vasodi-
phenylsulfamoylcarbamate derivatives (1) with differ-
lating properties [4], as well as sedative effects
ent aldehydes afforded the corresponding intramolecu-
[5]. 4-Substituted-1H-2,1,3-benzothiadiazine-2,2-
lar cyclized products 2 under trifluoroacetic acid con-
dioxides and 3,4-dihydro analogues are also valuable
ꢀ
C
ditions. 2011 Wiley Periodicals, Inc. Heteroatom Chem
intermediates in the preparation of disinfectants,
22:192–197, 2011; View this article online at wileyonlineli-
bleaching agents, and antiseptics [6].
brary.com. DOI 10.1002/hc.20670
The usual procedure for the preparation of
fused 1H-2,1,3-thiadiazine 2,2-dioxides is a two-
step approach involving sulfamoylation of ortho-
INTRODUCTION
substituted amino derivatives, followed by ring
closure [1]. This technique produces 4(3H)-
oxo [7], 4-amino [8], or 4-phenyl [9] 1H-
2,1,3-benzothiadiazines from o-aminobenzoates,
o-aminobenzonitriles, or 2-aminobenzophenones,
respectively.
Among the components of the bicyclic diazine group
of heterocyclic compounds [1], benzothiadiazin-
S,S-dioxides are of special interest because of their
Catalytic hydrogenation of 4-substituted-
1H-2,1,3-benzothiadiazenes yielded the corre-
sponding 3,4-dihydro derivatives. These com-
pounds can be prepared directly by reaction of
2-aminobenzylamines with either sulfuryl chloride
[10] or sulfamide [11]. Recently, Pews reported
Correspondence to: Sang Ook Kang; e-mail: sangok@korea.ac
.kr.
Contract grant sponsor: Basic Science Research Program
through the National Research Foundation of Korea (NRF),
funded by the Ministry of Education, Science and Technology
Contract grant number: 2009-0072638.
c
ꢀ
2011 Wiley Periodicals, Inc.
192

Facile Synthesis of 4-Substituted 3,4-Dihydro-1H-2,1,3-Benzothiadiazine 2,2-Dioxides 193
H
N
H
N
H
H
R
R
R
R
SO2
NH
SO2
NH
R
R
N
N
O
tBu
S
O2
O
Ar
Ar
Intramolecular
cyclization
Iminium
intermediate
R = H 1a, OCH3 1b
FIGURE 1 Retrosynthetic analysis.
the synthesis of 3-alkyl derivatives by reaction of
N-alkyl-Nꢁ-arylsulfamides with trioxane [12]. The
scope of these methods is related to the substitution
in the benzo moiety; thus, the C-4 position was
unsubstituted in almost all the cases.
As 4-substituted-1H-2,1,3-benzothiadiazine 2,2-
dioxides were required for new drug candidate syn-
thesis, we decided to explore a more straightforward
synthesis approach. A simple retrosynthetic analy-
sis led us to recognize that N-t-butyloxycarbonyl-
Nꢁ-arylsulfamides (1) could be a suitable precursor
(Fig. 1). So we decided to explore this approach
by carrying out, as the key step, the intramolecular
cyclization of the corresponding N-arylsulfamides
with aldehydes to get the iminium ion, which could
subsequently be cyclized under trifluoroacetic acid
conditions.
FIGURE 2 Molecular structure of 2f with thermal ellipsoids
drawn at the 30% level and H atoms, except H1, H2, and H4,
are omitted for clarity.
A
few general methods for the prepa-
of 4-substituted-3,4-dihydro-1H-2,1,3-
ration
benzothiadiazine 2,2-dioxides have been reported
[13]. We recently demonstrated that intramolecular
α-sulfamidoalkylation transformations proceed-
ing through the intermediary of an iminium ion
provide an expeditious route for the preparation
of cyclic sulfamides [14]. Herein, we report the
successful transformation of N-t-butyloxycarbonyl-
Nꢁ-arylsulfamides (1) into 4-substituted-1H-2,1,3-
benzothiadiazine 2,2-dioxides (2a–j) via this
approach, allowing different substituents at C-4.
desired heterocyclic benzothiadiazines 2a–j in good
yield (2a: 60%; 2b: 79%; 2c: 61%; 2d: 83%; 2e:
62%; 2f: 85%; 2g: 65%; 2h: 80%; 2i: 45%; 2j: 60%).
1
All the new compounds were characterized by H
and 13C NMR, elemental analysis, and X-ray crys-
1
tallography. The H NMR spectrum of compounds
2a–d showed resonances at around 4.50–4.99 ppm
due to the methylene protons in the CHRꢁ (Rꢁ = H,
Me), respectively. Peaks at around 46.7–53.3 ppm
(CHRꢁ) were observed in the 13C NMR spectrum
of compounds 2a–d. Spectroscopic characterization
of the 4-aryl-1H-2,1,3-benzothiadiazine compounds
2e–h showed that the aryl group is linked to the C-
4 position in the benzothiadiazine ring. The most
significant difference between the 1H NMR spec-
trum of 2a–d and 2e–h was the downfield shift of
signals for the methylene proton of CHRꢁ (Rꢁ =
Ph, 3 OMePh). The 1H NMR spectrum of com-
pounds 2e–h showed resonances at around 5.55–
6.67 ppm due to the methylene protons in the CHRꢁ
unit, respectively. Peaks at around 46.7–62.6 ppm
(CHRꢁ) were observed the downfield shift of sig-
nals of C-4 in the 13C NMR spectrum of compounds
2e–h.
RESULT AND DISCUSSION
The starting materials 1 were prepared according to
established synthetic protocols [15]. When t-butanol
was reacted with an equimolar quantity of chloro-
sulfonyl isocyanate in dichloromethane, followed
by the reaction with 2 equimolar quantity of ani-
line or 3,4-dimethoxybenzenamine, compounds 1
were formed with 80 and 91% yields, respectively.
The general synthetic strategy for the preparation
of 4-Rꢁ-3,4-dihydro-1H-2,1,3-benzothiadiazine 2,2-
dioxides 2 was developed by the intramolecular cy-
clization reaction using trifluoroacetic acid condi-
tions in dichloromethane (Scheme 1).
The final structural proof of 2f was obtained by
an X-ray analysis, which was performed on the crys-
tals of 2f (Fig. 2). Selected bond lengths, bond angles,
The intramolecular cyclization reaction of 1 with
aldehydes or acetal was carried out to obtain the
Heteroatom Chemistry DOI 10.1002/hc

194 Lee et al.
H
N
H
N
R
R
H
R
R
H
H
SO2
NH
H+
SO2
NH
R
R
N
NH2
CF3COOH
R
R
N
N
O
R'CHO
S
tBu
S
O2
O2
O
R'
R'
R = H 1a, OCH3 1b
2a R' = H, R = H
2b R' = H, R = OCH3
2c R' = Me, R = H
2d R' = Me, R = OCH3
2e R' = Ph, R = H
2f R' = Ph, R = OCH3
2g R' = 3-OMePh, R = H
2h R' = 3-OMePh, R = OCH3
2i R' = o-carboranylmethyl, R = H
2j R' = o-carboranylmethyl, R = OCH3
SCHEME 1 Synthesis of compounds 2.
and torsion angles are collected in Table 1. The crys-
tal structure corresponds well with the conforma-
tion and configuration derived from the NMR data.
All three regions, that is, aryl, heterocyclic ring, and
tethered phenyl group of 2f, can be clearly assigned.
The crystal structure of 2f confirms that the hetero-
cyclic ring exists in a half-chair conformation with
an equatorial phenyl substituent. The S1–N1/N2
1 and o-carboranylmethyl diethyl acetal [16]. In the
1H NMR spectra of 2i and 2j, diagnostic signals
were observed for methylene protons of CHCH2 and
CH Cab at around 4.48–4.52 and 2.74–3.68 ppm, re-
2
spectively. Both the 2i and 2j yielded 1H NMR signals
very similar to those of the 2a–d. Key signals de-
tected in the 13C NMR spectrum of 2i and 2j include
resonances at 30.7 and 31.2 (CH2Cab), 55.8 and 56.0
(CHCH2), 63.1 and 63.5 (CH at carborane), and 74.9
and 74.6 (Cipso at carborane) ppm, respectively.
Recently, the construction of high boron con-
tent molecules has received considerable interest
[17]. At the same time, the introduction of carbo-
ranes into different types of dendrimeric structures,
at the inner region or at the molecular surface, is
also being explored [18]. The medicinal chemistry
of o-carborane, which contains 10 boron atoms, has
a clear advantage for its use in boron neutron cap-
ture therapy. The biological activities, including the
cytotoxicity and intracellular accumulation of the
o-carboranyl benzothiadiazine derivative, were next
investigated. As shown in Table 2, compounds 2i and
j exhibited high cytotoxicity in CT26 cells, with IC50
˚
bond distance 1.6425(13)/1.6139(12) A is similar
˚
to 1.631(4)/1.611(5) A in 3,4-dihydroisoquinoline-
2(1H)-sulfonamide [14]. The coordination geometry
at the S1 atom is distorted tetrahedrally, with bond
angles between 118.23(7) (O1–S1–O2), 109.78(6)
(O1–S1–N2), 107.64(7) (O2–S1–N2), 108.13(7) (O1–
S1–N1), 110.36(7) (O2–S1–N1), and 101.40(6)◦ (N1–
S1–N2), as shown in Table 1 and Fig. 2. These values
are similar to 105.3(3)–119.9(2)◦ obtained in the 3,4-
dihydroisoquinoline-2(1H)-sulfonamide [14]. In 2f,
the torsion angles for N1–S1–N2–C4/C10 range from
−58.46(11) to 55.87(10)◦.
As shown in Scheme 1, the benzothiadiazines
2i and 2j containing o-carboranyl moiety (C2B10H11,
Cab) were prepared from the reaction of sulfamides
◦
◦
˚
TABLE 1 Selected Bond Lengths (A), Bond Angles ( ), and Torsion Angles ( ) of 2f
˚
Bond Lengths (A)
S(1)–O(1)
S(1)–O(2)
S(1)–N(2)
S(1)–N(1)
1.4242(10)
N(1)–C(3)
N(2)–C(4)
N(2)–H(2)
N(1)–H(1)
1.4327(16)
1.4883(16)
0.87(2)
1.4381(12)
1.6139(12)
1.6425(13)
0.79(2)
Bond Angles (◦)
O(3)–S(1)–O(4)
O(3)–S(1)–N(2)
O(4)–S(1)–N(2)
118.23(7)
109.78(6)
107.64(7)
O(3)–S(1)–N(1)
O(4)–S(1)–N(1)
N(2)–S(1)–N(1)
108.13(7)
110.36(7)
101.40(6)
Torsion Angles (◦)
O(1)–S(1)–N(1)–C(3)
O(2)–S(1)–N(1)–C(3)
N(2)–S(1)– N(1)–C(3)
171.29(9)
−58.00
O(1)–S(1)–N(2)–C(4)
O(2)–S(1)–N(2)–C(4)
N(1)–S(1)–N(2)–C(4)
−172.65
57.42(12)
−58.46(11)
55.87(10)
Heteroatom Chemistry DOI 10.1002/hc

Facile Synthesis of 4-Substituted 3,4-Dihydro-1H-2,1,3-Benzothiadiazine 2,2-Dioxides 195
Synthesis of 4-Rꢁ-3,4-Dihydro-1H-2,1,3-
benzothiadiazine 2,2-dioxides (2a–j)
TABLE 2 Effects of o-Carboranyl Derivatives (2i and j) on
CT26 Cells Viability and Intracellular Accumulation
Viability
Accumulated Boron
General Procedure. Aldehydes (2.5 mmol) and
excess trifluoroacetic acid were added to a stirred so-
lution of N-t-butyloxycarbonyl-Nꢁ-phenylsulfamides
1 (2.0 mmol) in dichloromethane (30 mL) via a
cannula through a serum cap at 0◦C. The resulting
mixture was stirred at room temperature for 24 h.
The progress of the reaction was monitored by thin
layer chromatography. After completion of the reac-
tion, the removal of the solvent at the rotary evap-
orator gave a crude product, which was then chro-
matographed (SiO2, Hx:EA 2:1) to yield 2a–j.
Compound
IC50a (mM) Concentrationb (ppm)
2i
2j
0.691 0.035
0.671 0.017
p-Boronophenylalanine 4.627 0.404
(BPA)
0.465 0.075
0.454 0.040
0.264 0.026
aCT26 cells (5 × 103 cells) were incubated for 3 days in the presence
of various concentrations of compounds 2i and 2j or BPA, and the
viability was determined by MTT assay.
bCT26 cells (5 ×105 cells) were incubated for 3 h in the presence
of compounds 2i and 2j or BPA (10 ppm). After three washes, the
accumulated boron concentrations were determined by inductively
coupled plasma atomic emission spectroscopy (ICP-AES). The val-
ues are the mean SD from three samples.
Characterization of 4-Rꢁ-3,4-dihydro1H-2,1,3-
benzothiadiazine 2,2-dioxides (2a–j)
values (the half maximal inhibitory concentration)
in the 0.671 0.017 mM. However, the accumulated
boron concentration of compounds 2i and j was
higher than that of p-boronophenylalanine (BPA).
2a: Yield: 60% (0.22 g, 1.2 mmol). mp 183–185◦C.
Elemental Analysis: C7H8N2O2S, Found: C, 45.63; H,
4.40; N, 15.20. Calcd: C, 45.64; H, 4.38; N, 15.21.
IR (KBr pellet, cm−1) ν(S O) 1313, 1171. H NMR
1
(acetone-d6) δ 4.99 (d, J = 15.6 Hz, 2H), 6.67 (t, J =
15.6 Hz, 1H), 6.77 (m, 1H), 7.17–7.41 (m, 3H), 9.23
(s, 1H). 13C NMR (acetone-d6) δ 46.7 (CH2), 120.63,
124.9, 126.4, 127.5, 129.1, 129.6 (Ph).
CONCLUSION
In conclusion, we found a one-pot synthetic pro-
cedure for the formation of the 4-substituted 3,4-
dihydro-1H-2,1,3-benzothiadiazine 2,2-dioxides 2
based on an intramolecular α-sulfamidoalkylation
reaction of N-t-butyloxycarbonylsulfamides 1 with
aldehydes or acetal in an acidic condition.
2b: Yield: 79% (0.39 g, 1.6 mmol). C9H12N2O4S,
Found: C, 44.28; H, 4.96; N, 11.45. Calcd: C, 44.25;
H, 4.95; N, 11.47. IR (KBr pellet, cm−1) ν(S O) 1317,
1156. 1H NMR (acetone-d6) δ 3.74 (s, 6H), 4.50 (d, J =
15.0 Hz, 2H), 6.09 (t, J = 15.0 Hz, 1H), 6.42 (s, 1H),
6.76 (m, 1H), 9.51 (s, 1H). 13C NMR (acetone-d6) δ
47.7 (CH2), 55.6, 55.7 (OCH3), 102.9, 110.4, 111.2,
132.3, 145.3, 149.4 (Ph).
EXPERIMENTAL
All manipulations were performed under
a
2c: Yield: 61% (0.24 g, 1.2 mmol). mp 80–82◦C.
C8H10N2O2S, Found: C, 48.45; H, 5.10; N, 14.10.
Calcd: C, 48.47; H, 5.08; N, 14.13. IR (KBr pellet,
dry, oxygen-free nitrogen or argon atmo-
sphere using standard Schlenk techniques.
Dichloromethane was distilled under nitro-
gen from P2O5. Chlorosulfonyl isocyanate, t-
butanol, and aniline derivatives were used as
received from Aldrich Chemicals (St. Louis, MO).
o-Carborane was purchased from KatChem (Prague,
Czech Republic) and used after sublimation. The
starting materials 1 [15] and o-carboranyl diethyl
acetal [16] were synthesized by literature proce-
1
cm−1) ν(S O) 1323, 1160. H NMR (acetone-d6) δ
1.68 (d, J = 18.8 Hz, 3H), 4.75–4.79 (m, 1H), 6.18 (d,
J = 19.3 Hz, 1H), 6.83 (d, J = 7.8 Hz, 1H), 7.19 (t,
J = 15.1 Hz, 2H), 7.27 (d, J = 7.8 Hz, 1H), 9.02 (br
s, 1H). 13C NMR (acetone-d6) δ 19.2 (CHCH3), 53.3
(CHCH3), 117.3, 122.2, 124.8, 126.3, 128.2, 139.0
(Ph).
2d: Yield: 83% (0.43 g, 1.7 mmol). mp 108–112◦C.
C10H14N2O4S, Found: C, 46.47; H, 5.45; N, 10.88.
Calcd: C, 46.50; H, 5.46; N, 10.85. IR (KBr pellet,
1
dures. H and 13C NMR spectra were recorded on
a Varian Mercury 300 spectrometer operating at
300.1 and 75.4 MHz, respectively. All proton and
carbon chemical shifts were measured relative to
internal residual peaks from the lock solvent (99.5%
acetone-d6). IR spectra were recorded on a Biorad
FTS-165 spectrophotometer. Elemental analyses
were performed with a Carlo Erba instruments
CHNS-O EA1108 analyzer. All melting points were
taken in open capillaries and are uncorrected.
1
cm−1) ν(S O) 1329, 1158. H NMR (acetone-d6) δ
1.65 (d, J = 10.0 Hz, 3H), 3.75 (s, 3H), 3.78 (s, 3H),
4.65–4.70 (m, 1H), 6.03 (d, J = 2.0 Hz, 1H), 6.43 (s,
1H), 6.84 (s, 1H), 8.53 (br s, 1H). 13C NMR (acetone-
d6) δ 28.6 (CHCH3), 53.3 (CHCH3), 55.3, 56.0 (OCH3),
102.8, 110.6, 116.6, 132.1, 145.3, 149.4 (Ph).
2e: Yield: 62% (0.32 g, 1.2 mmol). Mp. 133–
135◦C. C13H12N2O2S, Found: C, 60.01; H, 4.66; N,
Heteroatom Chemistry DOI 10.1002/hc

196 Lee et al.
10.77. Calcd: C, 59.98; H, 4.65; N, 10.76. IR (KBr
(OCH3), 63.5 (CabCH), 74.6 (CabCipso), 102.4, 111.5,
112.4, 132.6, 144.7, 149.6 (Ph).
1
pellet, cm−1) ν(S O) 1326, 1164. H NMR (acetone-
d6) δ 5.83 (d, J = 2.0 Hz, 1H), 6.64 (d, J = 2.0 Hz, 1H),
7.08–7.11 (m, 2H), 7.27-7.45 (m, 5H), 7.53-7.56 (m,
1H), 7.65–7.68 (m, 2H), 7.96–7.98 (m, 1H), 9.13 (br
s, 1H). 13C NMR (acetone-d6) δ 62.4 (CHPh), 117.6,
118.5, 120.9, 121.9, 128.2, 128.4, 128.7, 129.2, 139.5,
140.3 (Ph).
Crystal Structure Determination. Preliminary
examination and data collection were performed us-
ing a Brucker SMART CCD detector system single-
crystal X-ray diffractometer equipped with a sealed-
tube X-ray source (40 kV × 50 mA) using graphite-
2f: Yield: 85% (0.54 g, 1.7 mmol). mp 160–
163◦C. C15H16N2O4S, Found: C, 56.21; H, 5.04, N,
8.77. Calcd: C, 56.24; H, 5.03; N, 8.74. IR (KBr pel-
˚
monochromated Mo Kα radiation (λ = 0.7107 A).
Preliminary unit cell constants were determined
with a set of 45 narrowframe (0.3◦ in ω) scans.
The double-pass method of scanning was used to
exclude any noise. The collected frames were inte-
grated using an orientation matrix determined from
the narrow–frame scans. The SMART software pack-
age was used for data collection, and SAINT was
used for frame integration [19]. Final cell constants
were determined by a global refinement of xyz cen-
troids of reflections harvested from the entire data
set. Structure solution and refinement were carried
out using the SHELXTL-PLUS software package
[20].
1
let, cm−1) ν(S O) 1317, 1157. H NMR (acetone-d6)
δ 3.40 (s, 3H), 3.70 (s, 3H), 5.55 (d, J = 2.0 Hz, 1H),
6.08 (s, 1H), 6.41 (s, 1H), 7.34–7.37 (m, 5H), 7.49 (d,
J = 2.0 Hz, 2H), 9.94 (brs, 1H). 13C NMR (acetone-
d6) δ 56.1, 56.4 (OCH3), 61.9 (CHPh), 102.7, 112.2,
114.8, 128.8, 129.0, 129.5, 133.0, 139.8, 144.2, 149.5
(Ph).
2g: Yield: 65% (0.35 g, 1.2 mmol). C14H14N2O3S,
Found: C, 57.89; H, 4.85; N, 9.64. Calcd: C, 57.92;
H, 4.86; N, 9.65. IR (KBr pellet, cm−1) ν(S O) 1321,
1
1159. H NMR (acetone-d6) δ 4.99 (s, J = 15.6 Hz,
2H), 6.67 (t, J = 15.6 Hz, 1H), 6.77 (m, 1H), 7.17−-
7.41 (m, 3H), 9.23 (s, 1H). 13C NMR (acetone-d6) δ
46.7 (CH), 120.63, 124.9, 126.4, 127.5, 129.1, 129.6
(Ph).
X-ray Crystal Data for 4-Phenyl-3,4-dihydro-1H-
2,1,3-(3,4-dimethoxybenzo)thiadiazine
2,2-dioxide
(2f). C15H16N2O4S, M = 320.36, Orthorhombic, space
˚
˚
˚
group P212121, a = 5.570(1) A, b = 16.002(3) A, c =
2h: Yield: 80% (0.56 g, 1.6 mmol). mp 163–
164◦C. C16H18N2O5S, Found: C, 54.82; H, 5.19, N,
7.98. Calcd: C, 54.85; H, 5.18; N, 7.99. IR (KBr pel-
let, cm−1) ν(S O) 1319, 1155. 1H NMR (acetone-d6) δ
3.51 (s, 3H), 3.77 (s, 3H), 3.80 (s, 3H), 5.69 (s, J = 2.0
Hz, 1H), 6.25 (s, 1H), 6.28 (d, J = 2.0 Hz, 1H), 6.51
(s, 1H), 6.93–6.95 (m, 1H), 7.06–7.07 (m, 1H), 7.07–
3
˚
16.311(3) A, V = 1453.7(5) A , Z = 4, Dc = 1.464
g/m3, F(000) = 672, R = 0.0291, absolute structure
1
parameter = 0.05(5). CCDC no. 789856 contains
the supplementary crystallographic data for this
paper. 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).
7.08 (m, 2H), 7.31–7.34 (m, 1H), 8.69 (br s, 1H). 13
C
NMR (acetone-d6) δ 54.8 (OCH3), 55.3, 55.9 (OCH3),
62.6 (CHPh), 103.0, 114.2, 114.4, 115.1, 121.4, 129.7,
132.8, 141.6, 145.0, 150.0, 160.2 (Ph).
2i: Yield: 45% (0.3 g, 0.9 mmol). mp 158–160◦C.
C10H20B10N2O2S, Found: C, 35.26; H, 5.93, N, 8.24.
Calcd: C, 35.28; H, 5.92; N, 8.23. IR (KBr pellet,
Supporting Information
Supporting Information related to this article con-
taining the experimental data is available from
the corresponding author (sangok@korea.ac.kr) on
request.
1
cm−1) ν(B H) 2581, ν(S O) 1321, 1162. H NMR
(acetone-d6) δ 3.01–3.04 (m, 1H), 3.35–3.68 (m, 1H),
4.48–4.52 (m, 1H), 5.15 (br s, 1H), 6.85−-7.04 (m,
2H), 7.24–7.30 (m, 1H), 7.50–7.58 (m, 2H), 9.23 (s,
1H). 13C NMR (acetone-d6) δ 30.7 (CH2Cab), 55.8
(CHCH2Cab), 63.1 (CabCH), 74.9 (CabCipso), 118.4,
118.8, 122.0, 128.7, 128.9, 131.8 (Ph).
REFERENCES
2j: Yield: 60% (0.48 g, 1.2 mmol). mp 162–165◦C.
C12H24B10N2O4S, Found: C, 36.02; H, 6.05, N, 7.01.
Calcd C, 35.99; H, 6.04; N, 6.99. IR (KBr pellet, cm−1)
ν(B H) 2581, ν(S O) 1325, 1161. 1H NMR (acetone-
d6) δ 3.13 (m, 1H), 3.31−-3.36 (m, 2H), 3.69 (s, 3H),
3.71 (s, 3H), 4.48–4.52 (m, 1H), 5.19 (br s, 1H), 6.73
(s, 1H), 7.48 (s, 1H), 9.90 (s, 1H). 13C NMR (acetone-
d6) δ 31.2 (CH2Cab), 56.0 (CHCH2Cab), 56.8, 57.0
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