Design, synthesis and evaluation of N-substituted saccharin derivatives as selective inhibitors of tumor-associated carbonic anhydrase XII

Article abstract of DOI:10.1016/j.bmc.2014.01.056

A series of N-alkylated saccharin derivatives were synthesized and tested for the inhibition of four different isoforms of human carbonic anhydrase (CA, EC 4. 2.1.1): the transmembrane tumor-associated CA IX and XII, and the cytosolic CA I and II. Most of the reported derivatives inhibited CA XII in the nanomolar/low micromolar range, hCA IX with K_Is ranging between 11 and 390 nM, whereas they were inactive against both CA I (K_Is >50 μM) and II (K_Is ranging between 39.1 nM and 50 μM). Since CA I and II are off-targets of antitumor carbonic anhydrase inhibitors (CAIs), the obtained results represent an encouraging achievement for the development of new anticancer candidates without the common side effects of non-selective CAIs. Moreover, the lack of an explicit zinc binding function on these inhibitors opens the way towards the exploration of novel mechanisms of inhibition that could explain the high selectivity of these compounds for the inhibition of the transmembrane, tumor-associated isoforms over the cytosolic ones.

Full text of DOI:10.1016/j.bmc.2014.01.056

Bioorganic & Medicinal Chemistry 22 (2014) 1821–1831
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Design, synthesis and evaluation of N-substituted saccharin
derivatives as selective inhibitors of tumor-associated carbonic
anhydrase XII
a
a
b
Melissa D’Ascenzio a, Simone Carradori a, , Celeste De Monte , Daniela Secci , Mariangela Ceruso ,
⇑
Claudiu T. Supuran b,c,
⇑
a Dipartimento di Chimica e Tecnologie del Farmaco, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy
b Università degli Studi di Firenze, Polo Scientifico, Laboratorio di Chimica Bioinorganica, Rm. 188, Via della Lastruccia 3, 50019 Sesto Fiorentino (Florence), Italy
c Università degli Studi di Firenze, Neurofarba Dept., Section of Pharmaceutical and Nutriceutical Sciences, Via U. Schiff 6, 50019 Sesto Fiorentino (Florence), Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of N-alkylated saccharin derivatives were synthesized and tested for the inhibition of four differ-
ent isoforms of human carbonic anhydrase (CA, EC 4. 2.1.1): the transmembrane tumor-associated CA IX
and XII, and the cytosolic CA I and II. Most of the reported derivatives inhibited CA XII in the nanomolar/
low micromolar range, hCA IX with KIs ranging between 11 and 390 nM, whereas they were inactive
Received 31 December 2013
Revised 26 January 2014
Accepted 30 January 2014
Available online 10 February 2014
against both CA I (KIs >50 lM) and II (KIs ranging between 39.1 nM and 50 lM). Since CA I and II are
off-targets of antitumor carbonic anhydrase inhibitors (CAIs), the obtained results represent an encour-
aging achievement for the development of new anticancer candidates without the common side effects of
non-selective CAIs. Moreover, the lack of an explicit zinc binding function on these inhibitors opens the
way towards the exploration of novel mechanisms of inhibition that could explain the high selectivity of
these compounds for the inhibition of the transmembrane, tumor-associated isoforms over the cytosolic
ones.
Keywords:
Saccharin
Selective carbonic anhydrase XII inhibitors
N-alkylation
Cyclic tertiary sulfonamides
Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction
cells try to compensate these changes in internal pH by enhancing
the expression of a series of proteins and membrane transporters
Solid tumors are often surrounded by a dynamic microenviron-
ment characterized by acidic pH and low levels of oxygen, glucose
and other nutrients.1 In order to survive these harsh conditions
cancer cells acquire various adaptive features which have been
proposed to be responsible for the development of invasive and
metastatic phenotypes.2–4 In fact, we know that cancer is not only
a genetic disorder but also a disease of dysregulated metabolism.
As a direct result of regional hypoxia, cancer cells fulfill their need
for high levels of ATP by switching their metabolism from aerobic
respiration to fermentative glycolysis, a phenomenon also known
as Warburg effect.5,6
such as H+-ATPases, the Na+-H+ exchanger NHE1, the monocarb-
oxylate-H+ efflux co-transporters MCT1 and MCT4, and carbonic
anhydrases (CA) IX and XII.8–10 Therefore, targeting these pH mod-
ulating proteins is an effective approach to treat recurrent, meta-
static and drug resistant tumors.9–13
CA IX and XII are overexpressed in multiple primary and meta-
static cancer cell-lines and nowadays represent well-established
targets both for tumor imaging, as diagnostic markers, as well as
for the treatment of tumors expressing them.14–19 As a result, a
considerable amount of literature has been produced in the last
few years in the search for effective, potent and selective inhibitors
of the fifteen reported isoforms of carbonic anhydrase,20–24 with
particular attention to the cancer related ones, CA IX and XII.25,26
However, the differences between the active sites of different CA
isoforms are minimal, subtle and this often results in the inhibition
of both target and off-target isoforms of CA.23,26,27
Metabolic reprogramming represents one of the hallmarks of
pre-malignant lesions and it is the cause of a pH dysregulation
which coupled with poor vascularization determines the formation
of a cytostatic and/or lethal microenvironment.7 In general, cancer
Although a wide variety of CAIs has been described in the
past,22,28,29 one of the most common approaches to design small
molecules targeting this family of metalloenzymes consists of
inserting zinc binding moieties into the structure of the inhibitor:
⇑
Corresponding authors. Tel./fax: +39 06 49693242 (S.C.); tel.: +39 055 4573005;
fax: +39 055 4573385 (C.T.S.).
E-mail addresses: simone.carradori@uniroma1.it (S. Carradori), claudiu.
supuran@unifi.it (C.T. Supuran).
http://dx.doi.org/10.1016/j.bmc.2014.01.056
0968-0896/Ó 2014 Elsevier Ltd. All rights reserved.

1822
M. D’Ascenzio et al. / Bioorg. Med. Chem. 22 (2014) 1821–1831
the sulfonamide group is one of the most important and widely
used moieties.22,30–33 In all of the crystallographic/molecular mod-
elling studies reported to date the primary sulfonamide derivatives
have been shown to bind to the catalytic zinc ion in the active site
of CA in their deprotonated form.34,35 However, it has recently
been demonstrated that even secondary/tertiary sulfonamides
are able to selectively inhibit the cancer related isoforms of CA IX
and XII, suggesting a different mechanism of action compared to
the classical, primary sulfonamides.36,37
Herein we report the synthesis of a new series of tertiary
sulfonamides obtained by functionalizing the sulfonamide nitro-
gen of saccharin, a renowned sweetener characterized by a really
safe toxicological profile and a peculiar ability of inhibiting
carbonic anhydrase isoforms in the high nanomolar/low micro-
molar range.38,39
observed rates. Stock solutions of inhibitor (1 lM) were prepared
in distilled–deionized water and dilutions up to 0.1 nM were done
thereafter with the assay buffer. Inhibitor and enzyme solutions
were preincubated together for 15 min at room temperature prior
to assay, in order to allow for the formation of the E-I complex or
for the eventual active site mediated hydrolysis of the inhibitor.
The inhibition constants were obtained by non-linear least-squares
methods using PRISM 3 and the Cheng–Prusoff equation,42 and
represent the mean from at least three different determinations.
All recombinant CA isoforms were obtained in-house as previously
reported.
An exhaustive SAR for this class of putative CAIs can be defined
as follows:
(i) All of the tested compounds proved to be inactive
(KI >50 lM) against hCA I, one of the most common off-
target isoforms of anticancer CAIs. In fact, hCA I is ubiqui-
tously expressed in the body, and can be found in high
concentrations in the blood and in the gastro-intestinal tract.
2. Chemistry
Compounds 1–20 and 11a were synthesized according to the
general procedure reported in Scheme 1. Saccharin (1.0 equiv)
was deprotonated using freshly grinded anhydrous potassium
carbonate and the corresponding salt was then reacted with an
electrophile (2–4 equiv) by stirring the reaction mixture in
N,N-dimethylformamide at 80 °C overnight. Compound 21 was
synthesized via a 1-3 dipolar cycloaddition of 2 to the dipole orig-
inated by the reaction of 27 with triethylamine in ethyl acetate.
Compound 27 was obtained via a two-step synthetic route:
commercially available 4-nitrobenzaldehyde was reacted with
hydroxylamine hydrochloride and triethylamine to give the corre-
sponding 4-nitrobenzaldoxime 26 in a 1:10 cis:trans mixture.40
Compound 26 underwent a chlorination reaction using N-chloro-
succinimide and catalytic hydrochloric acid in N,N-dimethylform-
amide to give 27 in good yield.41 Compound 22 was synthesized
by reacting 5 with hydroxylamine hydrochloride and triethylamine
in methanol at 80 °C to give the corresponding oxime in a 1:4
cis:trans mixture. Compound 23 was obtained by refluxing deriva-
tive 6 in concentrated HCl. The reaction of 23 with methylamine
in the presence of carbonyl diimidazole (CDI) in N,N-dimethylform-
amide at room temperature gave 24 in moderate yield. Opening of
the tensioned lactam ring of compound 8 using sodium borohydride
(12 equiv) in methanol gave the corresponding secondary sulfon-
amide 25. All synthesized compounds have been fully characterized
by analytical and spectral data (see Section 5.2 for details).
hCA II was also poorly inhibited (KI >50 lM) by most of the
compounds reported here, such as 1, 12, 15–21, 23 and 25,
whereas some of them were nanomolar inhibitors (2–5, 7–
11, 13, 22 and 24 showed inhibition constants in the range
of 36.7–158 nM). Few other derivatives were micromolar
hCA II inhibitors (6, 14, PH010918, S763217 and S780197
showed KIs in the range of 0.46–2.6 lM).
(ii) All the investigated compounds showed to inhibit hCA XII in
the low micromolar/nanomolar range, with the only excep-
tion of compounds 11a, PH010918 and S763217 which were
not active at concentrations higher than 50 lM. The intro-
duction of small unsaturated carbon chains on the sulfonam-
idic nitrogen of saccharin determined an increase of activity
of the obtained compounds against CA XII (see compounds
2–4 compared to saccharin in Table 1), although no selectiv-
ity was obtained against the off target isoform CAII. In par-
ticular, compound 4 showed to be more active against CA
II (KI = 36.7 nM) than against the cancer related isoforms
CA IX and XII (KI = 97 nM and 0.21 lM, respectively). When
the unsaturated substituent was a cyano group (compound
1) the obtained derivative showed a slight loss of activity
against CA IX and XII (KI = 0.29
lM and 0.71 lM, respec-
tively), together with a promising gain of selectivity (KI
>50
lM towards CA I and II). However, the introduction of
a
3 methylene long spacer between the sulfonamidic
Compounds PH010918, S763217 and S780197 were purchased
by Sigma–AldrichÒ Italy and used in the biological assays without
further characterization and/or purification.
nucleus of saccharin and the cyano group (PH010918)
caused
a
dramatic loss of activity against CA XII
(KI >50
l
M) and selectivity against CA II (KI = 1.26 M). Sac-
l
3. Results and discussion
charin derivatization at the sulfonamidic nitrogen with
various electron poor benzyl substituents gave derivatives
7–15. Among these compounds, those in which the aromatic
ring was substituted with an ortho/meta nitro group (com-
pounds 8–9) or bromine (compounds 10–11) displayed the
highest activity against CA XII (21.1 nM < KI < 28.1 nM)
despite their low selectivity (39.1 nM < KI < 86.8 nM towards
CA II). Moreover, compounds 8 and 9 showed to be good
inhibitors even of the other cancer related isoform CA IX
(KI = 91 nM and 11 nM, respectively). On the other hand,
the exchange of bromine with fluorine or chlorine on the
benzyl ring determined a significative loss of activity of the
obtained compounds against both CA IX and CA XII (see
compounds 12–15). The use of bulky naphthyl or phthalyl
substituents had a similar outcome (see compounds 16
and 17), although these compounds showed a promising
selectivity against CA XII with reference to all of the other
All the synthesized (1–25 and 11a) and purchased (PH010918,
S763217 and S780197) compounds were tested in order to evalu-
ate their biological activity against the cancer related isoforms of
carbonic anhydrase CA IX and XII, as well as against their corre-
sponding off-targets CA I and II (Tables 1 and 2).
An Applied Photophysics stopped-flow instrument has been
used for assaying the CA catalyzed CO2 hydration activity. Phenol
red (0.2 mM) has been used as indicator, working at the absor-
bance maximum of 557 nm, with 20 mM Hepes (pH 7.5, for
a-CAs) as buffer, and 20 mM NaClO4 (for maintaining constant
the ionic strength), following the initial rates of the CA-catalyzed
CO2 hydration reaction for a period of 10–100 s. For the determina-
tion of the kinetic parameters and inhibition constants, the CO2
concentrations ranged from 1.7 to 17 mM. For each inhibitor at
least six traces of the initial 5–10% of the reaction have been used
for determining the initial velocity. The uncatalyzed rates were
determined in the same manner and subtracted from the total
tested isoforms: CA I, II and IX (KI >50
lM), whereas com-
pound 15 inhibited both CA IX and XII. A similar behavior

M. D’Ascenzio et al. / Bioorg. Med. Chem. 22 (2014) 1821–1831
1823
O
O
O
O
O
N
O
K2CO3
R
S
S
S
+
+
NH
N
X
X
R
DMF, 80°C
R
O
O
O
11a
Cl Br
,
1 - 20
=
O
O
O
O
O
O
O
O
O
O
N
O
O
N
OEt
S
S
S
S
N
NO2
N
O
O
6
O
2
O
5
8
.
HCl conc
90 °C
NaBH4
MeOH, rt
Et3N
NH2OH HCl, Et3N
MeOH, 80°C
27
EtOAc, rt
OH
N
O
O
O
O
O
O
O
N
O
S
OH
S
S
S
N
N
N
H
O
O
O
O
OH
25
NO2
N
NO2
21
22
23
NH2CH3, CDI
DMF, rt
O
O
NH
S
N
O
24
Cl
H
OH
CHO
OH
.
NH2OH HCl, Et3N
NCS, HCl (g)
DMF, 50 °C
N
N
O2N
O2N
O2N
MeOH, 80°C
27
26
O
S
O
S
O
S
CN
O
O
O
N
N
CH3
N
O
Cl
O
HO
O
O
PH010918
S763217
Scheme 1. Synthesis of compounds 1–27.
S780197
was observed by introducing an extra carbonyl between the
methylene and the aromatic ring of the benzyl group. Ben-
zoyl derivatives 18–20 showed to inhibit CA XII only in the
respectively), and they were not active against CA I, II and
IX at concentrations higher than 50 M. Analogous results
were obtained for the cycloaddition product 21 (KI CA
XII = 0.24 M, KICA IX = 0.31 M, KI CA I/II >50 M), which
l
low micromolar range (KI = 1.78
l
M, 0.97
l
M and 2.01
lM,
l
l
l

1824
M. D’Ascenzio et al. / Bioorg. Med. Chem. 22 (2014) 1821–1831
Table 1
Inhibitory activity of derivatives 1–25, PH010918, S763217, and S780197 against selected hCA isoforms by a stopped-flow CO2 hydrase assay
O
O
R
S
N
O
Compound
R
KI (nM)
hCA I
hCA II
hCA IX
hCA XII
N
CH
1
2
3
>50,000
>50,000
>50,000
>50,000
158
290
210
140
710
570
94
86
4
5
>50,000
>50,000
36.7
42
97
210
440
O
O
150
6
7
>50,000
>50,000
2210
47.6
330
240
76.5
150
OEt
CN
8
>50,000
>50,000
>50,000
>50,000
>50,000
>50,000
>50,000
40.9
91
28.1
24.6
25.1
21.1
2520
2690
1310
NO2
NO2
9
39.1
11
10
11
12
13
14
43.5
>50,000
360
Br
F
Br
86.8
>50,000
91.0
>50,000
380
F
F
460
>50,000
F
Cl
15
16
17
>50,000
>50,000
>50,000
>50,000
>50,000
>50,000
390
2760
Cl
>50,000
>50,000
2540
O
13,410
N
O
O
O
18
19
>50,000
>50,000
>50,000
>50,000
>50,000
>50,000
1780
970
O2N

M. D’Ascenzio et al. / Bioorg. Med. Chem. 22 (2014) 1821–1831
1825
Table 1 (continued)
Compound
R
KI (nM)
hCA I
hCA II
hCA IX
hCA XII
O
20
21
>50,000
>50,000
>50,000
2010
NO2
NO2
>50,000
>50,000
310
240
N
O
OH
N
O
22
23
>50,000
>50,000
41.4
270
310
240
>50,000
41.9
OH
O
24
25
>50,000
>50,000
38.1
200
28.4
250
N
H
O
O
S
N
H
>50,000
>50,000
OH
CN
NO2
Cl
PH010918
S763217
H
>50,000
>50,000
2600
1260
400
290
>50,000
>50,000
O
S780197
>50,000
1,800
230
2910
HO
Saccharin
AAZ (acetazolamide)
18,540
250
5950
12
103
25
633
6
Table 2
Inhibitory activity of derivatives 11 (N-alkylated saccharin) and 11a (O-alkylated saccharin) against selected hCA isoforms by a stopped-flow CO2 hydrase assay
Compound
KI (nM)
hCA I
hCA II
86.8
hCA IX
360
hCA XII
21.1
Br
O
O
N
S
11
>50,000
O
O
S
O
N
11a
>50,000
>50,000
>50,000
>50,000
Br
O
showed to be a selective inhibitor of the cancer related
isoforms of CA. However, the best results of activity and
selectivity were obtained when saccharin was derivatized
using a carboxylic moiety: ethyl ester 6 and its hydrolyzed
product 23 showed to inhibit CA XII at nanomolar concen-
trations (KI = 76.5 nM and 41.9 nM, respectively), with deriv-
ative 23 being the most selective compound of the entire
series (ratio KI CA I-II/KI CA XII >1193). Because of the
well-known hydrolytic activity of some CA isoenzymes, 6
could be considered a prodrug, which might be converted
into 23 inside the active site, thus resulting in enzyme inhi-
bition. However, the conversion of 23 into its corresponding
N-methylamide 24 did not cause any loss of activity against
CA XII (KI = 28.4 nM), although it determined a significative
loss of selectivity against CA II: ratio KI CA II/KI CA
XII = 1.34). On the contrary, the exchange of the carboxylic
moiety with a carbonyl/oxime caused a switch of selectivity
of compounds 5 and 22 towards CA II.
(iii) hCA IX was also inhibited by some of the saccharin deriva-
tives reported here. Inactive compounds were 10, 12, 14,
16–20 and 25 (KI >50 lM). Derivative 9 was an effective
hCA IX inhibitor, with an inhibition constant of 11.0 nM
(better than acetazolamide), whereas the remaining com-
pounds were medium potency inhibitors, with inhibition

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M. D’Ascenzio et al. / Bioorg. Med. Chem. 22 (2014) 1821–1831
constants ranging between 91 and 400 nM. Small modifica-
than interpretation, and are referenced to the residual non deuter-
ated solvent peak. Infra-red spectra were recorded on a Bruker
Tensor 27 FTIR spectrometer equipped with an attenuated total
reflectance attachment with internal calibration. Absorbtion max-
tions in the structures of these inhibitors led to drastic
changes in their hCA IX inhibitory activity: for example,
nitro-substituted regioisomers 8 and 9 differ in their affinity
for hCA IX by a factor of 8.3. The same behaviour was
observed for the pair of regioisomers 10 and 11 (incorporat-
ing bromine on the phenyl ring) or 12 and 13 (incorporating
fluorine), although in these cases the ortho-substituted
derivatives were totally inactive and the meta-substituted
ones showed moderate hCA IX inhibition (Table 1).
ima (m
max) are reported in wavenumbers (cmÀ1). All melting points
were measured on a StuartÒ melting point apparatus SMP1, and
are uncorrected. Temperatures are reported in °C. Where given,
systematic compound names are those generated by ChemBio-
Draw UltraÒ 12.0 following IUPAC conventions.
(iv) Lastly, a consideration must be done regarding the impor-
tance of N-substitution of saccharin against O-substitution
in order to obtain potent and selective CAIs. Alkylation of
saccharin under basic conditions is known to happen both
at the nitrogen and at the oxygen of the lactam ring, giving
a mixture of products.43 However, the products of the
reported saccharin derivatization were mostly only N-alkyl-
ated derivatives, which are believed to be the thermody-
namic products of the reaction.44 Only in one case
(compounds 11 and 11a) both products were isolated and
tested against the four different isoforms of CAs reported
before (Table 2). It is clear from the biological results that
only N-alkylated compounds were able to inhibit CA.
5.2. Chemistry
General procedure for the synthesis of compounds 1–20:
freshly grinded anhydrous potassium carbonate (1.1 equiv) was
added to a stirring solution of saccharin (1.0 equiv) in 10 mL of
N,N-dimethylformamide at room temperature. Up to 4.0 equiv of
the corresponding electrophile were added portionwise and the
reaction stirred at 80 °C for 24–72 h. The reaction was poured on
ice and the resulting solid was purified by filtration or column
chromatography on silica gel.
5.2.1. 2-(1,1-Dioxido-3-oxobenzo[d]isothiazol-2(3H)-
yl)acetonitrile (1)
1.66 g of potassium carbonate and 0.18 g of potassium iodide
(10 mol %) were added to a stirring solution of saccharin (2.0 g,
1.0 equiv) in 10 mL of N,N-dimethylformamide. 2.8 mL of chloro-
acetonitrile (4.0 equiv) were added portionwise and the reaction
stirred at 80 °C for 48 h. The reaction was poured on ice and the
resulting suspension was filtered to give title compound as a light
brown solid (2.0 g, 82% yield); mp 130–134 °C; IR mmax 3104
4. Conclusions
In conclusion, a new series of heterogeneous saccharin deriva-
tives were synthesized and tested against four human CAs: the
two cancer-related isoforms CA IX and XII, and the most common
off-targets of antitumoral CAIs, CA I and II. All investigated com-
pounds showed no affinity for CA I, while they were all able to
inhibit CA XII in the low micromolar/nanomolar range. Few of
the new compounds were not active as CA I and II inhibitors, show-
ing effective inhibition of CA XII. These compounds represent a
promising start for the development of new selective inhibitors
of this less investigated isoform of CA as novel anticancer agents
based on the toxicologically safe scaffold of saccharin. However,
further studies will be needed to determine whether these com-
pounds directly bind to the active site of the enzyme, which is
highly conserved amongst the different isozymes, or outside the
active site, since they have lost the zinc binding moiety. An
in-depth study of the mechanism of binding will give more infor-
mation about the origin of the high selectivity displayed by this
new series of inhibitors. However, at this moment the inhibition
mechanism with this type of compounds is not known. We
hypothesize that these compounds may bind within the coumarin
binding site at the entrance of the cavity or even further away from
the metal ion.
(m
Csp2-H), 2260 (
m
CN), 1744 (
m
C@O), 1336 (mas S@O), 1251 (
m
C-N), 1165 (ms S@O), 728 (d Csp2-H), 676 (d Csp2-H) cmÀ1
;
1H
NMR (400 MHz, DMSO-d6) d 5.11 (2H, s, CH2), 8.05 (1H, t,
J = 7.6 Hz, CHAr), 8.12 (1H, t, J = 7.6 Hz, CHAr), 8.19 (1H, d,
J = 7.6 Hz, CHAr), 8.40 (1H, d, J = 7.6 Hz, CHAr). 13C NMR (101 MHz,
DMSO-d6) d 25.9 (CH2), 115.35 (CN), 122.5 (Ar), 126.1 (Ar), 126.2
(Ar), 136.1 (Ar), 136.9 (Ar), 137.2 (Ar), 158.4 (C@O).
5.2.2. 2-(2-Propyn-1-yl)benzo[d]isothiazol-3(2H)-one 1,1-
dioxide (2)
1.86 g of potassium carbonate (1.1 equiv) were added to a stir-
ring solution of saccharin (2.0 g, 1.0 equiv) in 10 mL of N,N-dimeth-
ylformamide at room temperature. 5.0 mL of a 80% solution of
propargyl bromide in toluene (4.0 equiv) were added portionwise
and the reaction stirred at 80 °C for 48 h. The reaction was poured
on ice and the aqueous phase extracted with dichloromethane. The
organics were reunited, dried over sodium sulfate and concen-
trated in vacuo. Column chromatography on silica gel (ethyl ace-
tate–petroleum ether 1:1) gave title compound as a white solid
(1.44 g, 60% yield); mp 112–116 °C; IR mmax 3274 (
Csp2-H), 1737 ( C@O), 1332 (mas S@O), 1259 (
S@O), 749 (d Csp2-H) cmÀ1 1H NMR-cis (400 MHz, DMSO-d6) d
m
Csp-H), 3093
5. Experimental protocols
5.1. General
(m
m
m C-N), 1178 (ms
;
3.39 (s, 1H, C„H), 4.57 (s, 2H, CH2), 7.99 (dt, 1H, J1 = 7.6 Hz,
J2 = 0.8 Hz, CHAr), 8.05 (dt, 1H, J1 = 7.6 Hz, J2 = 0.8 Hz, CHAr), 8.11
(d, 1H, J = 7.6 Hz, CHAr), 8.31 (d, 1H, J = 7.6 Hz, CHAr); 13C NMR
(101 MHz, DMSO-d6) d 27.9 (CH2), 75.7 (C„CH), 77.5 (C„CH),
122.2 (Ar), 125.7 (Ar), 126.4 (Ar), 135.8 (Ar), 136.6 (Ar), 137.4
(Ar), 158.4 (C@O).
Solvents were used as supplied without further purification.
Where mixtures of solvents are specified, the stated ratios are vol-
ume:volume. Unless otherwise indicated, all aqueous solutions
used were saturated. Reagents were used directly as supplied by
Sigma–AldrichÒ Italy. Column chromatography was carried out
using Sigma–AldrichÒ silica gel (high purity grade, pore size 60 Å,
200–425 mesh particle size). Analytical thin-layer chromatography
was carried out on Sigma–AldrichÒ silica gel on TLA aluminium
foils with fluorescent indicator 254 nm. Visualization was carried
out under ultra-violet irradiation (254 nm). NMR spectra were
5.2.3. 2-Allylbenzo[d]isothiazol-3(2H)-one 1,1-dioxide (3)
0.83 g of potassium carbonate (1.1 equiv) were added to a stir-
ring solution of saccharin (1.0 g, 1.0 equiv) in 10 mL of N,N-dimeth-
ylformamide at room temperature. 1.1 mL of allyl bromide
(4.0 equiv) were added portionwise and the reaction stirred at
80 °C for 48 h. The reaction was poured on ice and the resulting
suspension was filtered to give title compound as a white solid
recorded on
Chemical shifts are quoted in ppm, based on appearance rather
a
Bruker AV400 (1H: 400 MHz, 13C: 101 MHz).

M. D’Ascenzio et al. / Bioorg. Med. Chem. 22 (2014) 1821–1831
1827
(0.95 g, 76% yield); mp 73–75 °C; IR mmax 3274 (
m
Csp-H), 3094
C-N), 1180
1H NMR (400 MHz, DMSO-d6) d
CHAr), 8.10 (1H, t, J = 7.6 Hz, CHAr), 8.16 (1H, d, J = 7.6 Hz, CHAr),
8.37 (1H, d, J = 7.6 Hz, CHAr).45
(m
Csp2-H), 1731 (
m C@O), 1331 (mas S@O), 1262 (m
(m
s S@O), 751 (d Csp2-H) cmÀ1
;
4.34 (s, 1H CH2), 5.25 (d, 1H, J = 10.0 Hz, @CH), 5.36 (d, 1H,
J = 16.8 Hz, @CH), 5.88–5.95 (m, 1H, CH@), 8.00 (t, 1H, J = 7.6 Hz,
CHAr), 8.06 (t, 1H, J = 7.6 Hz, CHAr), 8.11 (d, 1H, J = 7.6 Hz, CHAr),
8.32 (d, 1H, J = 7.6 Hz, CHAr); 13C NMR (101 MHz, DMSO-d6)
d 41.0 (CH2), 119.0 (@CH2), 122.2 (Ar), 125.6 (Ar), 126.7 (Ar),
131.7 (CH@), 135.7 (Ar), 136.3 (Ar), 137.4 (Ar), 158.7 (C@O).
5.2.7. 2-(4-Cyanobenzyl)benzo[d]isothiazol-3(2H)-one 1,1-
dioxide (7)
0.83 g of anhydrous potassium carbonate (1.1 equiv) were
added to a stirring solution of saccharin (1.0 g, 1.0 equiv) in
10 mL of N,N-dimethylformamide at room temperature. 4-Cyanob-
enzyl bromide (1.17 g, 1.1 equiv) was added and the reaction stir-
red at 80 °C for 72 h. The reaction was poured on ice and the
resulting suspension was filtered. Purification via column chroma-
tography on silica gel (ethyl acetate–petroleum ether 1:1) gave
title compound as a white solid (1.14 g, 71% yield); mp 178–
5.2.4. 2-(2-Buten-1-yl)benzo[d]isothiazol-3(2H)-one 1,1-dioxide
(4)
0.83 g of anhydrous potassium carbonate (1.1 equiv) were
added to a stirring solution of saccharin (1.0 g, 1.0 equiv) in
10 mL of N,N-dimethylformamide at room temperature. 4-Bro-
mo-2-butene (0.62 mL, 1.1 equiv, 1:5 cis/trans mixture) was added
and the reaction stirred at 80 °C for 48 h. The reaction was poured
on ice and the resulting suspension was filtered to give title com-
pound as a white solid (0.51 g, 40% yield, 1:5 cis/trans mixture); mp
180 °C; IR mmax 3096 (
mas S@O), 1255 ( C-N), 1181 (ms S@O), 752 (d Csp2-H), 673 (d
sp2-H) cmÀ1 1H NMR (400 MHz, DMSO-d6) d 5.00 (2H, s, CH2),
m Csp2-H), 2228 (m CN), 1724 (m C@O), 1334
(
m
C
;
7.62 (d, 2H, J = 8.4 Hz, 2 Â CHAr), 7.85 (d, 2H, J = 8.4 Hz, 2 Â CHAr),
8.02 (dt, 1H, J1 = 7.6 Hz, J2 = 0.8 Hz, CHAr), 8.09 (dt, 1H, J1 = 7.6 Hz,
J2 = 0.8 Hz, CHAr), 8.13 (d, 1H, J = 7.6 Hz, CHAr), 8.36 (d, 1H,
J = 7.6 Hz, CHAr); 13C NMR (101 MHz, DMSO-d6) d 41.6 (CH2),
111.0 (CN), 119.1 (Ar), 122.2 (Ar), 125.8 (Ar), 126.7 (Ar), 129.0
(Ar), 132.9 (Ar), 135.8 (Ar), 136.4 (Ar), 137.3 (Ar), 141.4 (Ar),
159.1 (C@O).
72–75 °C; IR mmax 3098 (
1324 (mas S@O), 1265 (
(d Csp2-H) cmÀ1 1H NMR-trans (400 MHz, DMSO-d6) d 1.66
m
Csp2-H), 1742 (
m C@O), 1724 (m C@O),
m
C-N), 1172 (ms S@O), 749 (d Csp2-H), 674
;
(d, 3H, J = 6.4 Hz, CH3), 4.27 (d, 2H, J = 6.0 Hz, CH2), 5.51-5.59 (m,
1H, CH@), 5.80–5.87 (m, 1H, CH@), 7.99 (t, 1H, J = 7.6 Hz, CHAr),
8.05 (t, 1H, J = 7.6 Hz, CHAr), 8.10 (d, 1H, J = 7.6 Hz, CHAr) 8.30
(d, 1H, J = 7.6 Hz, CHAr); 1H NMR-cis (400 MHz, DMSO-d6) d 1.76
(d, 0.6H, J = 5.2 Hz, CH3), 4.37 (d, 0.4H, J = 6.8 Hz, CH2), 5.71–5.73
(m, 0.2H, CH@), 6.03–6.08 (m, 0.2H, CH@); 13C NMR-trans
(101 MHz, DMSO-d6) d 17.8 (CH3), 122.0 (Ar), 124.4 (CH@), 125.5
(Ar), 126.7 (Ar), 130.7 (CH@), 135.7 (Ar), 136.3 (Ar), 137.4 (Ar),
158.7 (C@O), (CH2 signal missing due to overlap with DMSO-d6);
13C NMR-cis (101 MHz, DMSO-d6) d 15.0 (CH3), 123.6 (CH@),
130.5 (CH@).
5.2.8. 2-(2-Nitrobenzyl)benzo[d]isothiazol-3(2H)-one 1,1-
dioxide (8)
0.45 g of potassium carbonate (1.1 equiv) and potassium
iodide (0.5 g, 10 mol %) were added to a stirring solution of sac-
charin (0.5 g, 1.0 equiv) in 10 mL of N,N-dimethylformamide at
room temperature. 2-Nitrobenzyl chloride (0.57 g, 1.1 equiv)
was added and the reaction stirred at 80 °C for 24 h. The reaction
was poured on ice and the resulting suspension was filtered. Puri-
fication via column chromatography on silica gel (ethyl acetate–
n-hexane 1:2) gave title compound as
(0.75 g, 78% yield); mp 173–178 °C; IR mmax 3086 (
1721 ( C@O), 1527 (mas N-O), 1333 (mas S@O), 1302 (ms N-O),
1260 ( C-N), 1161 (ms S@O), 723 (d Csp2-H), 670 (d Csp2-H)
cmÀ1 1H NMR (400 MHz, DMSO-d6) d 5.33 (2H, s, CH2), 7.63
(1H, t, J = 8.24 Hz, CHAr), 7.64 (1H, d, J = 8.36 Hz, CHAr), 7.76 (1H,
dt, J1 = 7.78 Hz, J2 = 1.16 Hz, CHAr), 8.03 (1H, dt, J1 = 7.54 Hz,
J2 = 1.16 Hz, CHAr), 8.09 (1H, dt, J1 = 7.54 Hz, J2 = 1.16 Hz, CHAr),
8.16 (2H, m, 2 Â CHAr), 8.36 (1H, d, J = 7.52 Hz, CHAr); 13C NMR
(101 MHz, DMSO-d6) d 122.2 (Ar), 125.6 (Ar), 125.8 (Ar), 126.7
(Ar), 129.8 (Ar), 130.0 (Ar), 130.3 (Ar), 134.7 (Ar), 135.8 (Ar),
136.45 (Ar), 137.3 (Ar), 148.2 (Ar), 159.3 (C@O); (CH2 signal miss-
ing due to overlap with DMSO-d6).
a
light brown solid
5.2.5. 2-(2-Oxopropyl)benzo[d]isothiazol-3(2H)-one 1,1-dioxide
(5)
m
Csp2-H),
m
m
0.83 g of potassium carbonate (1.1 equiv) were added to a stir-
ring solution of saccharin (1.0 g, 1.0 equiv) in 10 mL of N,N-dimeth-
ylformamide at room temperature. 2-Chloroacetone (1.0 mL,
2.2 equiv) was added portionwise and the reaction stirred at
80 °C for 48 h. The reaction was poured on ice and the resulting
suspension was filtered to give title compound as a pink solid
;
(1.17 g, 89% yield); mp 118–120 °C; IR mmax 3098 (
m
Csp2-H), 1742
C-N), 1172
1H NMR (400 MHz,
(m
C@O), 1724 (
m C@O), 1324 (mas S@O), 1265 (m
(
ms S@O), 749 (d Csp2-H), 674 (d Csp2-H) cmÀ1
;
DMSO-d6) d 2.24 (s, 3H, CH3), 4.77 (s, 2H, CH2), 8.03 (dt, 1H,
J1 = 7.6 Hz, J2 = 0.8 Hz, CHAr), 8.09 (dt, 1H, J1 = 7.6 Hz, J2 = 0.8 Hz,
CHAr), 8.13 (d, 1H, J = 7.6 Hz, CHAr), 8.33 (d, 1H, J = 7.6 Hz, CHAr);
13C NMR (101 MHz, DMSO-d6) d 27.2 (CH3), 47.2 (CH2), 122.2
(Ar), 125.6 (Ar), 126.6 (Ar), 135.8 (Ar), 136.4 (Ar), 137.5 (Ar),
159.0 (C@O), 199.7 (C@O).
5.2.9. 2-(3-Nitrobenzyl)benzo[d]isothiazol-3(2H)-one 1,1-
dioxide (9)
0.83 g of potassium carbonate (1.1 equiv) were added to a stir-
ring solution of saccharin (1.0 g, 1.0 equiv) in 20 mL of N,N-dimeth-
ylformamide at room temperature. 3-Nitrobenzyl bromide (1.46 g,
1.1 equiv) was added and the reaction stirred at 80 °C for 72 h. The
reaction was poured on ice and the resulting suspension filtered.
Purification via column chromatography on silica gel (ethyl ace-
tate–n-hexane 1:1) gave title compound as a light orange solid
5.2.6. Ethyl 2-(1,1-dioxido-3-oxobenzo[d]isothiazol-2(3H)-yl)
acetate (6)
0.45 g of potassium carbonate (1.1 equiv) were added to a stir-
ring solution of saccharin (0.5 g, 1.0 equiv) in 10 mL of N,N-dimeth-
ylformamide at room temperature. 0.67 mL of
a
-bromoethyl
(0.70 g, 37% yield); mp 179–181 °C; IR mmax 3091 (
m
Csp2-H), 1736
C@O), 1529 (mas N-O), 1326 (mas S@O), 1294 (ms N-O), 1263
C-N), 1165 (ms S@O), 738 (d Csp2-H), 672 (d Csp2-H) cmÀ1 1H
acetate (2.0 equiv) were added and the reaction stirred at 80 °C
overnight. The reaction was poured on ice and the aqueous phase
was extracted with ethyl acetate (3 Â 50 mL). The organics were
reunited, washed with brine, dried over sodium sulfate, and con-
centrated in vacuo. The residue was purified by column chroma-
tography on silica gel (n-hexane-ethyl acetate 1:1) to give title
compound as a white solid (0.53 g, 70% yield); mp 86–89 °C; 1H
NMR (DMSO-d6, 400 MHz) d 1.21 (3H, t, J = 7.2 Hz, CH3), 4.17
(2H, q, J = 7.2 Hz, CH2), 4.62 (2H, s, CH2), 8.04 (1H, t, J = 7.6 Hz,
(
(
m
m
;
NMR (400 MHz, CD2Cl2) d 4.83 (2H, s, CH2), 7.41 (1H, t, J = 8.0 Hz,
CHAr), 7.69 (1H, t, J = 6.8 Hz, CHAr), 7.71–7.78 (2H, m, 2 Â CHAr),
7.81 (1H, d, J = 7.6 Hz, CHAr), 7.91 (1H, d, J = 7.2 Hz, CHAr), 8.01
(1H, d, J = 7.2 Hz, CHAr), 8.18 (s, 1H, CHAr); 13C NMR (101 MHz,
DMSO-d6) d 41.6 (CH2), 121.1 (Ar), 123.2 (Ar), 123.4 (Ar), 125.3
(Ar), 127.0 (Ar), 129.8 (Ar), 134.6 (Ar), 134.7 (Ar), 135.3 (Ar),
136.9 (Ar), 137.6 (Ar), 148.1 (Ar), 159.9 (C@O).

1828
M. D’Ascenzio et al. / Bioorg. Med. Chem. 22 (2014) 1821–1831
5.2.10. 2-(2-Bromobenzyl)benzo[d]isothiazol-3(2H)-one 1,1-
ioxide (10)
J = 7.2 Hz, CHAr), 8.08 (t, 1H, J = 7.6 Hz, CHAr), 8.14 (d, 1H,
J = 7.2 Hz, CHAr), 8.34 (d, 1H, J = 7.2 Hz, CHAr); 13C NMR (101 MHz,
DMSO-d6) d 36.0 (d, J = 4.8 Hz, CH2), 115.8 (d, J = 21.1 Hz, Ar),
122.1 (Ar), 122.4 (d, J = 14.1 Hz, Ar), 125.1 (d, J = 3.0 Hz, Ar),
125.7 (Ar), 126.6 (Ar), 130.7 (d, J = 14.1 Hz, Ar), 130.8
(d, J = 2.0 Hz, Ar), 135.8 (Ar), 136.4 (Ar), 137.3 (Ar), 158.9 (C@O),
160.6 (d, J = 247.5 Hz, Ar).
0.83 g of potassium carbonate (1.1 equiv) was added to a stir-
ring solution of saccharin (1.0 g, 1.0 equiv) in 10 mL of N,N-dimeth-
ylformamide at room temperature. 2-Bromobenzyl bromide
(1.37 g, 1.0 equiv) was added and the reaction stirred at 80 °C over-
night. The reaction was poured on ice and the resulting suspension
was filtered to give title compound as a white solid (0.90 g, 46%
yield); mp 160–161 °C; IR mmax 1731 (
1260 ( C-N), 1161 (ms S@O), 747 ( Csp2-Br), 724 (d Csp2-H), 674
(d Csp2-H) cmÀ1 1H NMR (400 MHz, DMSO-d6) d 4.98 (s, 2H,
CH2), 7.30 (d, 1H, J = 7.6 Hz, CHAr), 7.39 (t, 1H, J = 7.6 Hz, CHAr),
7.44 (t, 2H, J = 7.6 Hz, CHAr), 7.68 (d, 1H, J = 7.6 Hz, CHAr), 8.03
(t, 1H, J = 7.6 Hz, CHAr), 8.09 (t, 1H, J = 7.6 Hz, CHAr), 8.16 (d, 1H,
J = 7.2 Hz, CHAr), 8.35 (d, 1H, J = 7.6 Hz, CHAr); 13C NMR (101 MHz,
DMSO-d6) d 42.5 (CH2), 122.1 (Ar), 122.7 (Ar), 125.8 (Ar), 126.7
(Ar), 128.5 (Ar), 129.7 (Ar), 130.4 (Ar), 133.2 (Ar), 134.0 (Ar),
135.8 (Ar), 136.5 (Ar), 137.3 (Ar), 159.1 (C@O).
m
C@O), 1335 (mas S@O),
5.2.13. 2-(3-Fluorobenzyl)benzo[d]isothiazol-3(2H)-one 1,1-
dioxide (13)
m
m
;
0.83 g of potassium carbonate (1.1 equiv) was added to a stir-
ring solution of saccharin (1.0 g, 1.0 equiv) in 10 mL of N,N-dimeth-
ylformamide at room temperature. 3-Fluorobenzyl chloride
(0.97 g, 1.1 equiv) was added and the reaction stirred at 80 °C for
48 h. The reaction was poured on ice to give and the resulting sus-
pension was filtered to give title compound as a white solid (0.54 g,
34% yield); mp 105–107 °C; IR
1330 (mas S@O), 1265 ( C-N), 1181 (
(d Csp2-H) cmÀ1 1H NMR (400 MHz, DMSO-d6) d 4.96 (2H, s,
m
max 3075 (m Csp2-H), 1737 (m C@O),
m
m
C-F), 754 (d Csp2-H), 675
;
5.2.11. 2-(3-Bromobenzyl)benzo[d]isothiazol-3(2H)-one 1,1-
dioxide (11) and 3-((3-bromobenzyl)oxy)benzo[d]isothiazole
1,1-dioxide (11a)
CH2), 7.15 (t, 1H, J = 7.6 Hz, CHAr), 7.27 (m, 2H, 2 Â CHAr), 7.41 (q,
1H, J = 6.8 Hz, CHAr), 8.01 (t, 1H, J = 7.6 Hz, CHAr), 8.07 (t, 1H,
J = 7.2 Hz, CHAr), 8.13 (d, 1H, J = 7.2 Hz, CHAr), 8.35 (d, 1H,
J = 7.2 Hz, CHAr); 13C NMR (101 MHz, DMSO-d6) d 41.4 (CH2),
115.1 (d, J = 22.2 Hz, Ar), 115.4 (d, J = 20.2 Hz, Ar), 122.1 (Ar),
124.3 (d, J = 4.0 Hz, Ar), 125.7 (Ar), 126.7 (Ar), 131.0 (d, J = 8.1 Hz,
Ar), 135.8 (Ar), 136.4 (Ar), 137.3 (Ar), 138.5 (d, J = 7.1 Hz, Ar),
159.1 (C@O), 162.6 (d, J = 244.4 Hz, Ar).
0.83 g of potassium carbonate (1.1 equiv) was added to a stir-
ring solution of saccharin (1.0 g, 1.0 equiv) in 10 mL of N,N-dimeth-
ylformamide at room temperature. 3-Bromobenzyl bromide (1.5 g,
1.1 equiv) was added and the reaction stirred at 80 °C for 72 h. The
reaction was poured on ice and the aqueous phase was extracted
with ethyl acetate (3 Â 50 mL). The organics were reunited, dried
over sodium sulfate, and evaporated in vacuo. Purification via col-
umn chromatography on silica gel (ethyl acetate–petroleum ether
2:1) gave compound 11 as a white solid (1.65 g, 86% yield); mp
5.2.14. 2-(2,6-Difluorobenzyl)benzo[d]isothiazol-3(2H)-one 1,1-
dioxide (14)
0.45 g of anhydrous potassium carbonate (1.1 equiv) were
added to a stirring solution of saccharin (0.5 g, 1.0 equiv) in
10 mL of N,N-dimethylformamide at room temperature. 2,6-Diflu-
orbenzyl bromide (0.68 g, 1.1 equiv) was added and the reaction
stirred at 80 °C overnight. The reaction was poured on ice and
the resulting suspension was filtered to give title compound as a
white solid (0.75 g, 81% yield); mp 173–175 °C; IR mmax 1734
92–95 °C; IR mmax 2900 (
m
Csp2-H), 1721 (
m
C@O), 1331 (mas S@O),
1266 ( C-N), 1181 (
m
m
Csp2-Br), 678 (d Csp2-H) cmÀ1
;
1H NMR
(400 MHz, DMSO-d6) d 4.95 (2H, s, CH2), 7.33 (t, 1H, J = 7.6 Hz,
CHAr), 7.45 (d, 1H, J = 6.8 Hz, CHAr), 7.50 (d, 1H, J = 6.8 Hz, CHAr),
7.65 (s, 1H, CHAr), 8.00 (t, 1H, J = 7.2 Hz, CHAr), 8.06 (t, 1H,
J = 7.2 Hz, CHAr), 8.11 (d, 1H, J = 7.2 Hz, CHAr), 8.34 (d, 1H,
J = 7.2 Hz, CHAr); 13C NMR (101 MHz, DMSO-d6) d 41.35 (CH2),
122.1 (Ar), 125.7 (Ar), 126.7 (Ar), 127.4 (Ar), 131.0 (Ar), 131.2
(Ar), 135.8 (Ar), 136.4 (Ar), 137.2 (Ar), 138.4 (Ar), 159.1 (C@O)
(two aromatic carbon missing due to signals overlapping); and
compound 11a as a light violet solid (0.007 g; 1% yield); mp
(
(
m
C@O), 1339 (mas S@O), 1295 (
m
Csp2-F), 1253 (
m C-N), 1159
ms S@O), 754 (d Csp2-H), 674 (d Csp2-H) cmÀ1
;
1H NMR (400 MHz,
DMSO-d6) d 5.01 (2H, s, CH2), 7.15 (t, 2H, J = 8.0 Hz, 2 Â CHAr),
7.48 (t, 1H, J = 7.2 Hz, CHAr), 8.00–8.05 (m, 2H, 2 Â CHAr), 8.15
(d, 1H, J = 7.2 Hz, CHAr), 8.28 (d, 1H, J = 7.2 Hz, CHAr); 13C NMR
(101 MHz, DMSO-d6) d 30.3 (m, CH2), 110.8 (t, J = 19.2 Hz, Ar),
112.1 (d, J = 25.3 Hz, Ar), 121.9 (Ar), 125.8 (Ar), 126.4 (Ar), 131.8
(t, J = 11.1 Hz, Ar), 135.8 (Ar), 136.5 (Ar), 137.2 (Ar), 158.2 (C@O),
161.5 (d, J = 258.4 Hz, Ar).
82–84 °C; IR mmax 2927 (
1282 ( C-O), 1151 (ms S@O), 1061 (
cmÀ1 1H NMR (400 MHz, CDCl3) d 5.33 (2H, s, CH2), 7.39–7.41
m
Csp2-H), 1633 (
m
C@N), 1337 (mas S@O),
m
m Csp2-Br), 678 (d Csp2-H)
;
(m, 1H, CHAr), 7.44–7.46 (m, 1H, CHAr), 7.52–7.58 (m, 3H, CHAr),
7.59–7.60 (m, 1H, CHAr), 8.03 (s, 1H, CHAr), 8.11–8.13 (m, 1H, CHAr);
13C NMR (101 MHz, CDCl3) d 66.82 (CH2), 122.5 (Ar), 126.9 (Ar),
128.6 (Ar), 129.2 (Ar), 130.2 (Ar), 130.7 (Ar), 131.2 (Ar), 131.3
(Ar), 131.4 (Ar), 131.7 (Ar), 137.7 (Ar), 140.3 (Ar), 167.7 (C@N).
5.2.15. 2-(3,4-Dichlorobenzyl)benzo[d]isothiazol-3(2H)-one 1,1-
dioxide (15)
0.83 g of potassium carbonate (1.1 equiv) were added to a stir-
ring solution of saccharin (1.0 g, 1.0 equiv) in 10 mL of N,N-dimeth-
ylformamide at room temperature. 3,4-Dichlorobenzyl chloride
(0.83 mL, 1.1 equiv) was added and the reaction stirred at 80 °C
for 48 h. The reaction was poured on ice and the resulting
suspension was filtered to give title compound as a white solid
5.2.12. 2-(2-Fluorobenzyl)benzo[d]isothiazol-3(2H)-one 1,1-
dioxide (12)
0.83 g of potassium carbonate (1.1 equiv) was added to a stir-
ring solution of saccharin (1.0 g, 1.0 equiv) in 10 mL of N,N-dimeth-
ylformamide at room temperature. 2-Fluorobenzyl chloride
(0.867 g, 1.1 equiv) was added and the reaction stirred at 80 °C
for 72 h. The reaction was poured on ice and the resulting suspen-
sion was filtered to give title compound as a white solid (0.14 g, 8%
(0.86 g, 46% yield); mp 135–137 °C; IR mmax 3079 (
C@O), 1323 (mas S@O), 1264 ( C-N), 1182 (ms S@O), 750 (d
sp2-H), 675 (d Csp2-H) cmÀ1 1H NMR (400 MHz, DMSO-d6) d
m Csp2-H), 1727
(m
m
C
;
4.97 (2H, s, CH2), 7.43 (dd, 1H, J1 = 8.4 Hz, J2 = 2.0 Hz, CHAr), 7.63
(d, 1H, J = 8.4 Hz, CHAr), 7.71 (d, 1H, J = 2.0 Hz, CHAr), 8.01 (t, 1H,
J = 7.6 Hz, CHAr), 8.07 (t, 1H, J = 7.6 Hz, CHAr), 8.12 (d, 1H,
J = 7.6 Hz, CHAr), 8.34 (d, 1H, J = 7.6 Hz, CHAr); 13C NMR (101 MHz,
DMSO-d6) d 40.8 (CH2), 122.1 (Ar), 125.7 (Ar), 126.7 (Ar), 128.7
(Ar), 130.4 (Ar), 131.0 (Ar), 131.2 (Ar), 131.5 (Ar), 135.8 (Ar),
136.4 (Ar), 136.9 (Ar), 137.3 (Ar), 159.1 (C@O).
yield); mp 90–92 °C; IR mmax 3091 (
m
Csp2-H), 1731 (
C-N), 1157 (ms S@O), 1177 (
Csp2-H), 674 (d Csp2-H) cmÀ1 1H NMR (400 MHz, DMSO-d6) d
m
C@O), 1334
(mas S@O), 1262 (
m
m C-F), 749
(m
;
4.98 (2H, s, CH2), 7.20 (dt, 1H, J1 = 7.6 Hz, J2 = 1.2 Hz, CHAr), 7.24
(m, 1H, J1 = 10.3 Hz, J2 = 8.4 Hz, J3 = 1.2 Hz, CHAr), 7.49 (m, 1H,
CHAr), 7.47 (dt, 1H, J1 = 7.6 Hz, J2 = 1.6 Hz, CHAr), 8.02 (t, 1H,

M. D’Ascenzio et al. / Bioorg. Med. Chem. 22 (2014) 1821–1831
1829
5.2.16. 2-(Naphthalen-1-ylmethyl)benzo[d]isothiazol-3(2H)-one
1,1-dioxide (16)
N,N-dimethylformamide at room temperature.
a
-Bromo-2-nitro-
acetophenone (1.46 g, 1.1 equiv) was added and the reaction stir-
red at 80 °C overnight. The reaction was poured on ice and the
resulting suspension was filtered. Purification via column chroma-
tography on silica gel (ethyl acetate–petroleum ether 1:1) gave
title compound as an orange solid (0.10 g, 5% yield); mp 182–
0.83 g of potassium carbonate (1.1 equiv) were added to a stir-
ring solution of saccharin (1.0 g, 1.0 equiv) in 10 mL of N,N-dimeth-
ylformamide at room temperature. 1-(Chloromethyl)naphthalene
(0.9 mL, 1.1 equiv) was added and the reaction stirred at 80 °C
for 72 h. The reaction was poured on ice. The aqueous phase was
extracted with ethyl acetate (3 Â 50 mL), the organics were
reunited, dried over sodium sulfate and evaporated in vacuo. Puri-
fication by column chromatography on silica gel (ethyl acetate–
petroleum ether 1:2) gave title compound as a white solid
187 °C; IR mmax 3103 (
mas S@O), 1312 ( C-N), 1186 (ms S@O), 752 (d Csp2-H), 675 (d Csp2
H) cmÀ1 1H NMR (400 MHz, DMSO-d6) d 5.30 (2H, s, CH2), 7.86 (t,
m Csp2-H), 1739 (m C@O), 1728 (m C@O), 1337
(
m
-
;
1H, J = 6.8 Hz, CHAr), 7.91–7.95 (m, 2H, 2 Â CHAr), 8.05 (t, 1H,
J = 7.6 Hz, CHAr), 8.11 (t, 1H, J = 7.6 Hz, CHAr), 8.18–8.20 (m, 2H,
2 Â CHAr), 8.38 (d, 1H, J = 7.6 Hz, CHAr); 13C NMR (101 MHz, DMSO-
d6) d 46.7 (CH2), 119.6 (Ar), 122.3 (Ar), 124.9 (Ar), 125.7 (Ar), 126.4
(Ar), 129.4 (Ar), 133.3 (Ar), 134.7 (Ar), 135.9 (Ar), 136.6 (Ar), 137.6
(Ar), 146.7 (Ar), 159.1 (C@O), 193.3 (C@O).
(0.33 g, 19% yield); mp 142–145 °C; IR mmax 3083 (
C@O), 1335 (mas S@O), 1298 ( C-N), 1171 (ms S@O), 748
(d Csp2-H), 675 (d Csp2-H) cmÀ1 1H NMR (400 MHz, DMSO-d6) d
m Csp2-H), 1725
(m
m
;
5.43 (s, 2H, CH2), 7.49–7.63 (m, 4H, 4 Â CHAr), 7.93 (d, 1H,
J = 7.6 Hz, CHAr), 7.99–8.09 (m, 3H, 3 Â CHAr), 8.19 (d, 1H,
J = 7.6 Hz, CHAr), 8.22 (d, 1H, J = 8.0 Hz, CHAr), 8.33 (d, 1H,
J = 7.6 Hz, CHAr); 13C NMR (101 MHz, DMSO-d6) d 122.1 (Ar),
123.5 (Ar), 128.8 (Ar), 125.9 (Ar), 126.5 (Ar), 126.6 (Ar), 126.7
(Ar), 127.1 (Ar), 129.1 (Ar), 129.2 (Ar), 130.5 (Ar), 130.9 (Ar),
133.7 (Ar), 135.8 (Ar), 136.4 (Ar), 137.5 (Ar), 159.3 (C@O); (CH2 sig-
nal missing due to overlap with DMSO-d6).
5.2.20. 2-(2-(3-Nitrophenyl)-2-oxoethyl)benzo[d]isothiazol-
3(2H)-one 1,1-dioxide (20)
0.83 g of potassium carbonate (1.1 equiv) were added to a stir-
ring solution of saccharin (1.0 g, 1.0 equiv) in 10 mL of N,N-dimeth-
ylformamide at room temperature. a-Bromo-3-nitroacetophenone
(1.46 g, 1.1 equiv) was added and the reaction stirred at 80 °C over-
night. The reaction was poured on ice to give and the resulting sus-
pension was filtered. Purification via column chromatography on
silica gel (ethyl acetate–petroleum ether 1:1) gave title compound
5.2.17. 2-((1,1-Dioxido-3-oxobenzo[d]isothiazol-2(3H)-
yl)methyl)isoindoline-1,3-dione (17)
0.45 g of potassium carbonate (1.1 equiv) were added to a
stirring solution of saccharin (500 mg, 1.0 equiv) in 20 mL of
N,N-dimethylformamide at room temperature. N-(Chloro-
methyl)phthalimide (0.54 g, 1.0 equiv) was added and the reaction
stirred at 80 °C for 72 h. The reaction was poured on ice. The aque-
ous phase was extracted with ethyl acetate (3 Â 50 mL), the organ-
ics were reunited, dried over sodium sulfate and evaporated in
vacuo. Purification via column chromatography on silica gel (ethyl
acetate–n-hexane 2:1) gave title compound as a white solid
as an orange solid (0.7 g, 37% yield); mp 183–186 °C; IR
m
max 3083
C@O), 1336 (mas S@O), 1317
C-N), 1181 (ms S@O), 754 (d Csp2-H), 670 (d Csp2-H) cmÀ1 1H
5.30 (2H, s, CH2), 7.91 (t, 1H,
(
(
m
m
Csp2-H), 1731 (m C@O), 1709 (m
;
NMR (400 MHz, DMSO-d6)
d
J = 8.0 Hz, CHAr), 8.07 (t, 1H, J = 7.6 Hz, CHAr), 8.11 (t, 1H, J = 7.6 Hz,
CHAr), 8.18 (d, 1H, J = 7.6 Hz, CHAr), 8.39 (d, 1H, J = 7.6 Hz, CHAr),
8.53 (d, 1H, J = 8.0 Hz, CHAr), 8.56 (d, 1H, J = 8.0 Hz, CHAr), 8.82 (s,
1H, CHAr); 13C NMR (101 MHz, DMSO-d6) d 45.5 (CH2), 122.3 (Ar),
123.4 (Ar), 125.7 (Ar), 126.6 (Ar), 128.9 (Ar), 131.2 (Ar), 135.1 (Ar),
135.4 (Ar), 135.9 (Ar),136.6 (Ar),137.7 (Ar),148.6 (Ar), 159.2 (C@O),
189.9 (C@O).
(0.61 mg, 66% yield); mp 284–287 °C; IR mmax 1725 (
1337 (mas S@O), 1252 ( C-N), 1166 (ms S@O), 727 (d Csp2-H), 677
(d Csp2-H) cmÀ1 1H NMR (400 MHz, DMSO-d6) d 5.66 (2H, s,
m C@O),
m
;
CH2), 7.90 (2H, m, 2 Â CHAr), 7.97 (m, 2H, 2 Â CHAr), 8.02 (1H, t,
J = 7.6 Hz, CHAr), 8.07 (1H, t, J = 7.6 Hz, CHAr), 8.19 (1H, d,
J = 7.6 Hz, CHAr), 8.28 (1H, d, J = 7.6 Hz, CHAr); 13C NMR (101 MHz,
DMSO-d6) d 41.8 (CH2), 122.0 (Ar),124.1 (Ar), 126.0 (Ar), 126.15
(Ar), 131.6 (Ar), 135.6 (Ar), 135.9 (Ar), 136.7 (Ar), 137.1 (Ar),
157.75 (C@O), 166.9 (C@O).
5.2.21. 2-((3-(4-Nitrophenyl)isoxazol-5-
yl)methyl)benzo[d]isothiazol-3(2H)-one 1,1-dioxide (21)
2-(1-Propyn-3-yl)benzo[d]isothiazol-3(2H)-one 1,1-dioxide
2
(0.5 g, 1.0 equiv) and p-nitrohydroxyiminoacyl chloride (0.57 g,
1.25 equiv) were dissolved in 20 mL of ethyl acetate. 1.0 mL of a
solution of 0.2 mL of triethylamine (1.25 equiv) in ethyl acetate
was added dropwise over 30 min. A white suspension was formed
and the reaction stirred overnight at room temperature. The reac-
tion was quenched with 20 mL of water and diluted with 10 mL of
dichloromethane. The resulting suspension was filtered to give
title compound as a light yellow solid (0.35 g, 40% yield); mp
5.2.18. 2-(2-Oxo-2-phenylethyl)benzo[d]isothiazol-3(2H)-one
1,1-dioxide (18)
0.83 g of potassium carbonate (1.1 equiv) were added to a stir-
ring solution of saccharin (1.0 g, 1.0 equiv) in 10 mL of N,N-dimeth-
ylformamide at room temperature.
a
-Bromoacetophenone (1.19 g,
260–262 °C; IR mmax 3146 (
C@N), 1511 ( N-O), 1334 (mas S@O), 1303 (
1184 (ms S@O), 755 (d Csp2-H) cmÀ1
m
Csp2-H), 1721 (
m
C@O), 1598 (
m
1.1 equiv) was added and the reaction stirred at 80 °C overnight.
The reaction was poured on ice and the resulting suspension was
filtered to give title compound as a yellow solid (1.46 g, 89% yield);
m
m
N-O), 1268 (
m
C-N),
;
1H NMR (400 MHz, DMSO-
d6) d 5.24 (s, 2H, CH2), 7.31 (s, 1H, C(4)H-isoxazole), 8.02 (t, 1H,
J = 7.2 Hz, CHAr), 8.08 (t, 1H, J = 7.6 Hz, CHAr), 8.13 (d, 1H,
J = 7.6 Hz, CHAr), 8.17 (d, 2H, J = 8.0 Hz, 2 Â CHAr), 8.32 (d, 2H,
J = 8.0 Hz, 2 Â CHAr), 8.36 (d, 1H, J = 7.2 Hz, CHAr); 13C NMR
(101 MHz, DMSO-d6) d 33.8 (CH2), 102.8 (C(4)-isoxazole) 122.3
(Ar), 124.8 (2 Â Ar), 125.9 (Ar), 126.7 (Ar), 128.4 (2 Â Ar), 134.6
(Ar), 135.9 (Ar) 136.6 (Ar), 137.3 (Ar), 148.9 (Ar), 156.1 (C(5)-
isoxazole), 158.7 (C@O), 168.3 (C(3)-isoxazole).
mp 192–194 °C; IR mmax 3092 (
C@O), 1332 ( as S@O), 1296 (
sp2-H), 673 (d Csp2-H) cmÀ1 1H NMR (400 MHz, DMSO-d6) d 5.48
m
Csp2-H), 1735 (
m C@O), 1698
(m
m
m C-N), 1180 (ms S@O), 744 (d
C
;
(2H, s, CH2), 7.60 (t, 2H, J = 7.6 Hz, 2 Â CHAr), 7.74 (t, 1H, J = 7.6 Hz,
CHAr), 8.05 (dt, 1H, J1 = 7.6 Hz, J2 = 0.8 Hz, CHAr), 8.09–8.13 (m, 2H,
2 Â CHAr), 8.17 (d, 1H, J = 7.6 Hz, CHAr), 8.36 (d, 1H, J = 7.6 Hz, CHAr);
13C NMR (101 MHz, DMSO-d6) d 45.3 (CH2), 122.2 (Ar), 125.6 (Ar),
126.7 (Ar), 128.9 (Ar), 129.4 (Ar), 134.3 (Ar), 134.8 (Ar), 135.9 (Ar),
136.5 (Ar), 137.7 (Ar), 159.3 (C@O), 190.6 (C@O).
5.2.22. 2-(2-(Hydroxyimino)propyl)benzo[d]isothiazol-3(2H)-
one 1,1-dioxide (22)
5.2.19. 2-(2-(2-Nitrophenyl)-2-oxoethyl)benzo[d]isothiazol-
3(2H)-one 1,1-dioxide (19)
0.83 g of potassium carbonate (1.1 equiv) were added to a
stirring solution of saccharin (1.0 g, 1.0 equiv) in 10 mL of
2-(2-Oxopropyl)benzo[d]isothiazol-3(2H)-one 1,1-dioxide
5
(0.5 g, 1.0 equiv) was added to a stirring solution of hydroxylamine
hydrochloride (0.22 g, 1.5 equiv) and triethylamine (0.34 mL,
2.2 equiv) in 5.0 mL of anhydrous methanol. The reaction was

1830
M. D’Ascenzio et al. / Bioorg. Med. Chem. 22 (2014) 1821–1831
stirred overnight at 80 °C. Methanol was removed in vacuo and the
residue triturated with ice-cold water to give title compound as a
light brown solid (66 mg, 12.5% yield, 1:4 cis/trans mixture); mp
1522 (
m
N-O), 1327 (mas S@O), 1165 (ms S@O), 698 (d Csp2-H)
cmÀ1
;
1H NMR (400 MHz, DMSO-d6) d 4.34 (d, 2H, J = 5.6 Hz,
CH2), 4.88 (s, 2H, CH2), 5.45 (br s, 1H, NH), 7.39 (t, 1H, J = 7.2 Hz,
CHAr), 7.50 (t, 1H, J = 7.6 Hz, CHAr), 7.60–7.68 (m, 3H, 3 Â CHAr),
7.74–7.79 (m, 2H, 2 Â CHAr), 7.96 (d, 1H, J = 8.4 Hz, CHAr), 8.29
(br s, 1H, OH); 13C NMR (101 MHz, DMSO-d6) d 43.4 (CH2), 60.0
(CH2), 125.1 (Ar), 127.3 (Ar), 128.2 (Ar), 128.5 (Ar), 129.1 (Ar),
130.7 (Ar), 133.0 (Ar), 133.4 (Ar), 134.1 (Ar), 137.0 (Ar), 141.6
(Ar), 148.1 (Ar); LRMS (ESI+) m/z 345.17 (M+Na)+, calcd for
139–140 °C; IR mmax 3202
(
m
O-H), 3069
C@N) 1328 (mas S@O), 1250 (
ms S@O), 746 (d Csp2-H), 677 (d Csp2-H) cmÀ1 1H NMR-trans
(
m
Csp2-H), 1736
(m
C@O), 1620 (
m
m
C-N), 1143
(
;
(400 MHz,CDCl3) d 1.97 (s, 3H, CH3), 4.48 (s, 2H, CH2), 7.87–7.95
(m, 3H, 3 Â CHAr), 8.67 (d, 1H, J = 7.6 Hz, CHAr); 1H NMR-trans
(400 MHz,CDCl3) d 1.97 (s, 3H, CH3), 4.48 (s, 2H, CH2), 7.87–7.95
(m, 3H, 3 Â CHAr), 8.11 (d, 1H, J = 7.6 Hz, CHAr), 8.67 (br s, 1H,
OH); 1H NMR-cis (400 MHz,CDCl3) d 1.93 (s, 0.7H, CH3), 4.48 (s,
0.5H, CH2); 13C NMR-trans (101 MHz, CDCl3) d 11.8 (CH3), 42.2
(CH2), 121.1 (Ar), 125.5 (Ar), 127.0 (Ar), 134.5 (Ar), 135.1 (Ar),
137.7 (Ar), 152.0 (C@N), 159.0 (C@O); 13C NMR-cis (101 MHz,
CDCl3) d 16.8 (CH3), 35.8 (CH2).
C14H14N2O5S 345.05.
5.2.26. 4-Nitrobenzaldehyde oxime (26)
In an oven-dried flask hydroxylamine hydrochloride (1.37 g,
1.5 equiv) and triethylamine (2.1 mL, 2.25 equiv) were dissolved
in 10 mL of anhydrous methanol and stirred for 5 min at room
temperature. 2.0 g of 4-nitrobenzaldehyde (1.0 equiv) were added
and the reaction mixture was stirred at 80 °C for 4 h. After com-
plete consumption of starting material, the reaction was cooled
down to room temperature and the solvent removed in vacuo.
20 mL of ice cold water were added to the residue and the resulting
suspension was kept in an ice bath for 15 min. The obtained solid
was filtered and washed with petroleum ether/diethyl ether to give
title compound as white solid (2.10 g, 97% yield); mp 99–102 °C;
1H NMR (400 MHz, DMSO-d6) d 7.83 (d, 2H, J = 7.6 Hz, C(2)H and
C(6)H), 8.22 (d, 2H, J = 7.6 Hz, C(3)H and C(5)H), 8.28 (s, 1H,
CH@N), 11.83 (s, 1H, OH).40
5.2.23. 2-(1,1-Dioxido-3-oxobenzo[d]isothiazol-2(3H)-yl)acetic
acid (23)
Ethyl 2-(1,1-dioxido-3-oxobenzo[d]isothiazol-2(3H)-yl)acetate
6 (500 mg, 1.0 equiv) was suspended in 12 mL of concentrated
HCl. The reaction mixture was heated up to 90 °C and stirring
was carried out overnight. Dilution of the concentrated acid with
water gave a white suspension which was filtered to give title com-
pound as a white solid (387 mg, 84% yield); mp 200–203 °C; IR
mmax 3393 (
m
O-H), 1728 (
m
C@O), 1336 (mas S@O), 1257 (
m C-N),
1190 (ms S@O), 747 (d Csp2-H), 681 (d Csp2-H) cmÀ1
;
1H NMR
(400 MHz, DMSO-d6) d 4.49 (2H, s, CH2), 8.03 (1H, t, J = 7.6 Hz,
CHAr), 8.09 (1H, t, J = 7.6 Hz, CHAr), 8.15 (1H, d, J = 7.6 Hz, CHAr),
8.34 (1H, d, J = 7.6 Hz, CHAr), 13.34 (1H, bs, D2O exch., COOH);
13C NMR (DMSO-d6, 101 MHz) d 32.3 (CH2), 122.2 (Ar), 125.65
(Ar), 126.5 (Ar), 135.8 (Ar), 136.5 (Ar), 137.5 (Ar), 159.0 (C@O),
167.95 (C@O).
5.2.27. N-Hydroxy-4-nitrobenzimidoyl chloride (27)
In an oven-dried flask 4-nitrobenzaldheyde oxime 26 (1.86 g,
1.0 equiv) was dissolved in 10 mL of anhydrous N,N-dimethylform-
amide. 0.3 g of N-chlorosuccinimide (0.2 equiv) were added and
the reaction stirred for 10 min at room temperature. The solution
was purged with 20 mL of HClg. The reaction was stirred for 10
additional minutes and then heated up to 50 °C. 1.20 g of N-chloro-
succinimide were added portionwise (0.2 equiv at the time) over
half an hour. The reaction mixture was stirred at 50 °C overnight.
The progression of the reaction was monitored using iodine starch
paper. When the iodine starch paper was not turning brown any-
more, the reaction was quenched with 4 volumes of ice cold water.
The aqueous phase was extracted with diethyl ether (3 Â 50 mL),
the reunited organics were dried over sodium sulfate and evapo-
rated in vacuo to give title compound as light yellow solid
5.2.24. N-Methyl-2-(1,1-dioxido-3-oxobenzo[d]isothiazol-
2(3H)-yl) acetylamide (24)
Carbonyl diimidazole (202 mg, 1.5 equiv) and 0.62 mL of a 2 M
solution of methylamine in THF (1.5 equiv) were added to a stirring
solution of 2-(1,1-dioxido-3-oxobenzo[d]isothiazol-2(3H)-yl)acetic
acid 23 (200 mg, 1.0 equiv) in 5 mL of anhydrous DMF at room
temperature. After 4 h the reaction was diluted with dichlorometh-
ane (20 mL) and washed with a saturated solution of sodium bicar-
bonate. The organics were dried over sodium sulfate and
evaporated in vacuo. Purification via column chromatography on
silica gel (ethyl acetate–n-hexane 2:1) gave title compound as a
white solid (87 mg, 41% yield); mp 204–206 °C; IR mmax 3297
(1.92 g, 85% yield); mp 107–110 °C; IR mmax 3293 (
m
O-H), 2868
(m
Csp2-H), 1523 ( C@N), 1349 ( N-O), 1240 ( ;
m
m
m
C-N) cmÀ1
1H
NMR (400 MHz, DMSO-d6) d 8.00 (d, 2H, J = 8.0 Hz, 2 Â CHAr),
(
(
C
m
N-H), 3094 (
mas S@O), 1256 (
sp2-H) cmÀ1 1H NMR (400 MHz, DMSO-d6)
d
m
Csp2-H), 1737 (
C-N), 1187 (ms S@O), 753 (d Csp2-H), 672 (d
2.62 (d, 3H,
m C@O), 1664 (m C@O), 1333
8.26 (d, 2H, J = 8.0 Hz, 2 Â CHAr), 12.95 (s, 1H, OH).41
m
;
Acknowledgments
J = 4.4 Hz, CH3), 4.29 (2H, s, CH2), 8.02 (1H, t, J = 7.2 Hz, CHAr),
8.08 (1H, t, J = 7.2 Hz, CHAr), 8.13 (1H, d, J = 7.6 Hz, CHAr), 8.17
(bd, 1H, J = 4.0 Hz, NH), 8.34 (1H, d, J = 7.6 Hz, CHAr); 13C NMR
(101 MHz, DMSO-d6) d 26.15 (CH3), 122.2 (Ar), 125.5 (Ar), 127.1
(Ar), 135.7 (Ar), 136.2 (Ar), 137.3 (Ar), 159.1 (C@O), 165.5 (C@O);
(CH2 signal missing due to overlap with DMSO-d6).
This work was financed by two FP7 EU projects (Metoxia and
Dynano) to C.T.S.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmc.2014.01.056.
5.2.25. 2-(Hydroxymethyl)-N-(2-
nitrobenzyl)benzenesulfonamide (25)
(2-Nitrobenzyl)benzo[d]isothiazol-3(2H)-one 1,1-dioxide
8
References and notes
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with dichloromethane (3 Â 30 mL). The organics were reunited,
dried over sodium sulfate, and concentrated in vacuo to give title
compound as a light brown solid (0.19 g, 37% yield); mp 103–
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