Synthesis of antitumour (1H-1,2,3-triazol-4-yl)-4-hydroxycyclohexa-2,5- dien-1-ones by copper-catalysed Huisgen cycloadditions

Article abstract of DOI:10.1039/b920039h

4-Ethynyl-4-hydroxycyclohexa-2,5-dien-1-one 5 undergoes cycloaddition reactions with a range of substituted azides in the presence of copper salts to form 1,4-disubstituted triazoles 8-11 bearing the 4-hydroxycyclohexa-2,5-dien-1- one (quinol) pharmacopho

Full text of DOI:10.1039/b920039h

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www.rsc.org/obc | Organic & Biomolecular Chemistry
Synthesis of antitumour (1H-1,2,3-triazol-4-yl)-4-hydroxycyclohexa-
2,5-dien-1-ones by copper-catalysed Huisgen cycloadditions†
Andrew J. McCarroll,a Charles S. Matthews,b Geoffrey Wells,‡a Tracey D. Bradshawb and
Malcolm F. G. Stevens*a,b
Received 25th September 2009, Accepted 8th February 2010
First published as an Advance Article on the web 3rd March 2010
DOI: 10.1039/b920039h
4-Ethynyl-4-hydroxycyclohexa-2,5-dien-1-one 5 undergoes cycloaddition reactions with a range of
substituted azides in the presence of copper salts to form 1,4-disubstituted triazoles 8–11 bearing the
4-hydroxycyclohexa-2,5-dien-1-one (quinol) pharmacophore; one example of an isomeric
1,5-disubstituted triazole 12 was formed from 5 and benzyl azide in the presence of a ruthenium
catalyst. Compounds were screened for growth-inhibitory activity against five cancer cell lines of colon,
breast and lung origin, but were overall less potent than the benzothiazolyl- and indolyl-substituted
quinols 2 and 3.
pathway,6 compound 2 also displays anti-angiogenic properties in
Introduction
proliferating endothelial cells;7 variant 3 also perturbs signalling
Our interest in exploring the oxidation of simple phenols (eg
events modulated by downstream effectors of the tumour angio-
genesis process triggered by cellular hypoxia (eg Hif-1 and VEGf).8
In earlier work, we established a preliminary SAR for sub-
stituents at the 4-position in the quinols series regarding their
potency as inhibitors of cancer cell growth in vitro (Fig. 2).
Hydrogen is preferred at position R rather than acyl or alkyl.2
At position R1 a 6/5 heterocyclic (e.g. benzothiazole in 2 or indole
in 3) is preferred over a 6/6 heterobicyclic (e.g. quinoline) or a
monocyclic system (e.g. benzene or pyridine).2 In this paper, we
report an extension of these studies in which we have examined the
consequences of attaching a bulky aryl or alkyl group to a 1,2,3-
triazole substituent at R1 (compounds 8) in anticipation that these
modifications might display the desirable properties of quinols 2
and 3.
1) as a source of novel antitumour agents has been vindicated
in the identification of the 4-substituted 4-hydroxycyclohexa-2,5-
dien-1-one moiety (‘quinol’) as an unexploited pharmacophore in
drug discovery. Thus, oxidation of 1 with [(diacetoxy)iodo]benzene
(DAIB) in aqueous acetonitrile in the presence of TEMPO yielded
the prototypic benzothiazole-substituted quinol 2 (52%) (Fig. 1),
which displayed potent and selective antitumour activities against
colon, renal, and breast cancer cell lines in vitro.2 We have identified
the redox homeostasis-controlling protein thioredoxin (Trx)3 as
being an important molecular target.3 Subsequently, we have
identified a second, but more potent, series of indolyl-quinols
exemplified by the 6-fluoro-1-(phenylsulfonyl)indolylquinol 3,
which maintains the selectivity fingerprint against colon, renal
and breast cell lines in vitro4 but preferentially targets the protein
thioredoxin reductase (TrxR).5 Significantly, microarray analyses
of untreated human colorectal HCT 116 cells and those exposed
to 2 (1 mmol L-1) determined that, in a panel of over 10K cancer-
related genes, expression of only TrxR was upregulated > 3-fold.3
As expected for agents inhibiting the thioredoxin-signalling
aPharminox Ltd, Biocity, Pennyfoot Street, Nottingham, NG1 1GF
bCentre for Biomolecular Sciences, School of Pharmacy, University of
Nottingham, Nottingham, U.K. NG7 2RD. E-mail: malcolm.stevens@
nottingham.ac.uk; Fax: +44 115 951 3412; Tel: +44 115 951 3414
Fig. 2 Summary of SAR in antitumour quinols .
† Quinols as novel therapeutic agents. Part 9. For part 8 see ref. 1.
We have shown previously that quinol 3 can be prepared
efficiently in a Sonogashira coupling between the phenylsulfonyl-
substituted fluoroiodoaniline 4 and the 4-alkynylquinol 5.9 The
‡ Present address: Department of Pharmaceutical and Biological Chem-
istry, School of Pharmacy, 29–39 Brunswick Square, London, U.K. WC1N
1AX.
Fig. 1 Structures of 2-(4-hydroxyphenyl)benzothiazole 1 and antitumour 4-substituted-4-hydroxycyclohexa-2,5-dien-1-ones (‘quinols’) 2 and 3.
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Scheme 1 Synthesis of compound 3 by a Sonogashira reactiona.
(presumed) intermediate alkynyl-ol 6 cyclises spontaneously to
3 under the reaction conditions (Scheme 1). We were interested
to explore if the acetylene fragment of 5 was receptive to other
heterocycle-forming cyclizations, such as the generation of 1,2,3-
triazoles via the copper-catalysed Huisgen cycloaddition with
azides (a ‘click’ synthesis) which has found numerous applications
in a range of chemical/biological scenarios.10 In the current case,
outcomes of the proposed syntheses are non-obvious for two
reasons: the alkyne group in the quinol substrates is attached to a
quaternary carbon bearing an alcohol moiety; and the cyclohexa-
diene double bonds are potentially available for competing [3+2]
cycloadditions with an azide reagent.
azide failed to participate in the cycloaddition reaction under the
standard conditions, as did 4-azido-2-hydroxybenzoic acid and
2-(4-azidophenyl)-6-methyl-benzothiazole.
Owing to the potential hazards of purifying aryl azides,
particularly those of low molecular weight, we investigated a one-
pot route to triazole 8a, avoiding the isolation of phenyl azide 7a
by generating it in situ from phenyl iodide.11 However, this was an
inefficient process leading to a low yield (7%) of product.
Examples of alkyl and aralkyl azides 7k–n (prepared from the
corresponding bromides and sodium azide) were also effective sub-
strates for the cycloadditions (Scheme 2), leading to triazoles 8k–n
in excellent yields, although 6-azidohexanoic acid failed to give the
desired triazole. To further expand the broad applicability of the
click reaction in the quinols series, azido sugars 9a,b (which are
highly-modified alkyl azides) were employed in the cycloaddition
with alkyne-ol 5, although the highly polar pyranyl-substituted
triazole 10a (Scheme 3), which contains primary, secondary and
tertiary alcoholic functionalities, was hygroscopic and unsuitable
for biological evaluation. Different reaction conditions, a mixture
of Cu(I) iodide in chloroform containing 2,6-lutidine (Method B),
were required to facilitate cycloaddition of arylsulfonyl azides and
alkynyl-ol 5. The arylsulfonyl-substituted triazoles 11a,b (Fig. 3)
were obtained in moderate yields.
Results and discussion
A range of aryl azides (7a–i), prepared by diazotisation of various
anilines followed by treatment with sodium azide, were for the
most part used in the cycloaddition reactions without further
purification. The general ‘click’ procedure (Method A) involved
mixing the appropriate azide and alkyne-ol 5 in a mixture of
t-BuOH and water containing 1 M sodium ascorbate solution
and CuSO4·5H2O at 25 ◦C (Scheme 2). Cycloadditions proceeded
efficiently in the majority of cases, furnishing analytically pure
triazoles 8a–i on addition of water to the reaction mixture (with
the exception of 8i, which required further chromatographic
purification). 4-Azidopyridine 7j, prepared from 4-chloropyridine
and sodium azide, similarly gave the triazole 8j, but 4-nitrophenyl
Scheme 3 Synthesis of triazoles 10a,ba.
While the 1,4-disubstituted triazoles 8 are readily straightfor-
ward to obtain and isolate, we were also interested in the prepa-
ration of an isomeric 1,5-disubstituted analogue. Recent reports
Scheme 2 Synthesis of triazoles 8a–na.
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Fig. 3 Structures of 11 and 12.
Scheme 4 Synthesis of imidazole 14.
described the preparation of such triazoles from azides and alkynes
using a ruthenium catalyst Cp*RuCl(PPh3)2.12 The variation in
the regioselectivity from the copper-catalysed reaction is due to
mechanistic differences—a copper acetylide is formed leading
to 1,4-disubstituted triazoles, whereas a ruthenium acetylide is
not12b—and the solvent of choice is benzene, but work-up is
less straightforward. However, benzyl azide and alkyne 5 were
successfully combined to yield the desired triazole 12 (Fig. 3),
albeit in poor yield (<10%).
The substituted imidazole 14, which is a modified analogue
of 3 that also contains structural similarities to the triazoles,
was prepared by the standard lithiation route2 from precursor
13 shown in Scheme 4.
in Table 1. The dramatic differences in potency between the phenol
1 and the highly growth-inhibitory benchmark quinols 2 and 3
have been noted previously.4 The HCT 116 cell line was most
sensitive to compounds of the series 8; the least sensitive was
the A549 line, which is generally more resistant to compounds
of the quinols class.2,4,9 Against HCT 116 cells, GI50 values were
in the sub-micromolar range, with the exception of the pyrido-
analog 8j, which was approximately 10-fold less active. Against
the breast cell lines there were no notable potency differences
of compounds 8 against MCF-7 (ER+) and MDA 468 (ER-).
Disappointingly, the acetylated pyranyltriazole-substituted quinol
10b and the arylsulfonyltriazolyl-quinols 11a,b were generally
about 100-fold less growth-inhibitory than compounds in series
8. There were no notable differences between the potencies of the
1,4-(8l) and 1,5-(12) triazole regioisomers across the cell panel.
The two most active compounds amongst the new quinols in
these MTT assays were the decyl-substituted triazole 8k and the
phenylsulfonyl-imidazole 14, but neither displayed the nanomolar
growth-inhibitory potency of 2 and 3 against the HCT 116 cell
line (Table 1).
Biological results and discussion
The growth-inhibitory activities of new compounds were evaluated
against a panel of two human colon cancer cell lines (HCT 116
and HT 29), two mammary cell lines (MCF-7 and MDA 468) and
the generally chemoresistant lung adenocarcinoma line (A549).
Results of MTT assays following 72 h drug exposure are collated
Table 1 In vitro Growth-inhibitory potencies (GI50 values in mm)a of triazolyl- and imidazolyl-substituted 4-hydroxycyclohexa-2,5-dien-1-ones against
cancer cell linesb
Compound
HCT116
HT29
MCF-7
MDA 468
A549
1c
> 100
0.04
0.07
0.36
0.26
0.56
0.30
0.26
0.56
0.38
0.18
0.27
2.17
0.24
0.94
0.48
0.48
51.7
8.16
14.6
0.74
0.23
83.7
0.38
0.26
0.67
0.38
0.78
0.51
0.53
1.48
0.80
0.25
0.40
4.21
0.36
1.83
1.47
1.88
81.6
26.4
28.2
1.74
0.37
69.4
0.35
0.21
0.70
0.36
0.68
0.50
0.46
0.75
0.62
0.33
0.36
1.97
0.22
1.04
0.37
0.93
44.3
10.8
17.4
0.45
0.30
0.40
0.79
0.24
0.49
0.44
0.56
0.40
0.42
1.03
0.75
0.35
0.43
1.65
0.23
1.02
0.99
1.10
37.5
12.0
11.9
2.57
0.36
NT
2c
2.35
0.86
2.34
2.01
3.36
2.49
1.46
3.95
3.00
0.58
1.24
4.19
0.74
2.52
3.24
1.44
NT
3
8a
8b
8c
8d
8e
8f
8g
8h
8i
8j
8k
8l
8m
8n
10b
11a
11b
12
14
43.7
39.1
4.41
1.36
a Results are the mean of 3 determinations in MTT assays (see Experimental section). b Cancer line cell origin: HCT116 and HT29 (colon); MCF-7 (ER+
breast); MDA468 (ER- breast); A549 (lung). c Results from ref. 2. NT is not tested.
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Certain 1-aryltriazolyl-quinols, 8b,c,f,g and the 1-(4-methoxy-
benzyl)triazolyl-quinol 8n, were also evaluated in the NCI60
in vitro cell screen, which involves a 2 day drug exposure.13
The mean GI50 values were in the range 0.5–1.0 mM, whereas
the equivalent values for 2 and 3 were 0.23 and 0.016 mM,
respectively.4 These results confirm our earlier SAR analysis of
the activities of antitumour quinols: a bicyclic heterocyclic nucleus
at the cyclohexadienone 4-position (e.g. benzothiazole in 2 and
substituted indole in 3) is preferred to a monocyclic residue.2,4
4-(1-(4-Fluorophenyl)-1H-1,2,3-triazol-4-yl)-4-hydroxycyclohexa-
2,5-dienone 8c
By Method A, to give 8c as a beige powder (0.600 g; 95%), mp
173-178 ◦C. Found C 62.0, H 3.6, N 15.3. Calc. for C14H10FN3O2 C
62.0, H 3.7, N 15.5%. nmax/cm-1 1670, 1629, 1514. dH (DMSO-d6)
=
3.46 (1H, s, OH), 6.22 (2H, d, J 10.1, HC ), 7.22 (2H, d, J 10.1,
=
HC ), 7.45 (2H, t, J 8.8, ArH), 7.97 (2H, dd, J 9.1, 4.7, ArH),
7.90 (1H, s, CHN). dC (DMSO-d6) 65.7, 117.2 (d, J 24.2), 122.0,
123.0 (d, J 8.8), 126.9, 133.6 (d, J 2.8), 149.7, 150.9, 162.2 (d, J
345.8), 185.6. MS (ESI) m/z 272 (M+H)+.
Experimental section
4-Hydroxy-4-(1-(3-(trifluoromethyl)phenyl)-1H-1,2,3-triazol-4-
yl)cyclohexa-2,5-dienone 8d
Melting points were recorded on Stuart Scientific SMP3 appara-
tus, and are uncorrected. IR spectra were recorded on a Shimadzu
FT-IR8400S, and NMR spectra were recorded on a Bruker
Avance 400 instrument at 400.13 MHz (1H) and 100.62 MHz
(13C) in [2H6]DMSO) or CDCl3; coupling constants are in Hz.
Compounds that did not pass CHN Microanalysis were shown
to be >95% pure using LC/MS. The LC/MS system consisted
of an Agilent Technologies 1200 series LC connected to a 6110
Single Quadrupole MS with ESI source. Merck silica gel 60
(40–60 mm) was used for column chromatography. Azides were
prepared according to literature methods.14,15
By Method A, to give 8d as a beige powder (0.872 g; 91%), mp
165-166 ◦C. Found C 56.0, H 3.1, N 12.8. Calc. for C15H10F3N3O2
C 56.1, H 3.1, N 13.1%. nmax/cm-1 1672, 1630, 1618. dH (DMSO-
=
d6) 6.24 (2H, d, J 10.1, HC ), 6.70 (1H, s, OH), 7.23 (2H, d, J
=
10.1, HC ), 7.83-7.89 (2H, m, ArH), 8.28-8.32 (2H, m, ArH), 9.14
(1H, s, CHN). dC (DMSO-d6) 65.7, 117.3 (q, J 3.8), 122.1, 124.0
(q, J 272.6), 124.5, 125.8 (q, J 3.6), 126.9, 131.4 (q, J 32.6), 131.8,
137.5, 149.9, 150.7, 185.6. MS (ESI) m/z 322 (M+H)+.
4-Hydroxy-4-(1-(4-(trifluoromethyl)phenyl)-1H-1,2,3-triazol-
4-yl)cyclohexa-2,5-dienone 8e
General method for the synthesis of 1,4-disubstituted
1,2,3-triazoles 8a–n, 10a,b (Method A)
By Method A, to give 8e as a beige powder (0.820 g; 85%), mp
173-175 ◦C. Found C 56.1, H 3.1, N 12.9. Calc. for C15H10F3N3O2
C 56.1, H 3.1, N 13.1%. nmax/cm-1 1668, 1628. dH (DMSO-d6) 6.24
(2H, d, J 10.1, HC ), 6.72 (1H, s, OH), 7.23 (2H, d, J 10.1, HC ),
8.00 (2H, d, J 8.6, ArH), 8.20 (2H, d, J 8.6, ArH), 9.11 (1H, s,
CHN). MS (ESI) m/z 322 (M+H)+.
To a stirred mixture of the azide (3 mmol) and 4-ethynyl-4-
hydroxycyclohexa-2,5-dien-1-one 5 (0.402 g; 3 mmol) in t-BuOH
(6 mL) and water (6 mL) was added 1 M aqueous sodium
ascorbate solution (300 mL; 0.3 mmol), followed by copper sulfate
pentahydrate (7.5 mg, 0.03 mmol, in 100 mL of water). The mixture
was stirred overnight, diluted with water (50 mL) and filtered.
The precipitate was washed with water, and dried under vacuum
to afford the 4-substituted-4-hydroxycyclohexa-2,5-dien-1-ones
8a–n, 10a,b.
=
=
4-(1-(4-Methoxyphenyl)-1H-1,2,3-triazol-4-yl)-4-
hydroxycyclohexa-2,5-dienone 8f
By Meth◦od A, to give 8f as an off-white powder (0.600 g; 72%), mp
136-137 C. Found C 63.2, H 4.6, N 14.7. Calc. for C15H13N3O3
C 63.6, H 4.6, N 14.8%. nmax/cm-1 1670, 1512 dH (CDCl3) 3.59
4-Hydroxy-4-(1-phenyl-1H-1,2,3-triazol-4-yl)cyclohexa-2,5-
dienone 8a
=
(1H, s, OH), 3.89 (3H, s, OMe), 6.32 (2H, d, J 10.1, HC ), 7.04
By Method A, to give 8a as white needles (0.640 g; 83%), mp 145–
146 ◦C. nmax/cm-1 1663, 1624. dH (DMSO-d6) 6.22 (2H, d, J 10.1,
=
(2H, d, J 9.1, ArH), 7.13 (2H, d, J 10.1, HC ), 7.62 (2H, d, J 9.1,
ArH), 7.85 (1H, s, CHN). dC (DMSO-d6) 56.0, 65.7, 115.3, 121.7,
122.3, 126.8, 130.4, 149.4, 150.9, 159.8, 185.6. MS (ESI) m/z 284
(M+H)+.
=
=
HC ), 6.63 (1H, s, OH), 7.23 (2H, d, J 10.1, HC ), 7.48-7.52
(1H, m, ArH), 7.58-7.62 (2H, m, ArH), 7.90-7.93 (2H, m, ArH),
8.93 (1H, s, CHN). dC (DMSO-d6) 65.7, 120.6, 121.7, 126.8, 129.3,
130.4, 137.0, 149.7, 150.9, 185.6. MS (ESI) m/z 254 (M+H)+.
4-(1-(4-Acetylphenyl)-1H-1,2,3-triazol-4-yl)-4-
4-(1-(4-Bromophenyl)-1H-1,2,3-triazol-4-yl)-4-hydroxycyclohexa-
hydroxycyclohexa-2,5-dienone 8g
2,5-dienone 8b
By Method A, to give 8g as a beige powder (0.550 g; 62%), mp
167-170 ◦C. Found C 64.3, H 4.4, N 14.1. Calc. for C16H13N3O3 C
65.1, H 4.4, N 14.2%. nmax/cm-1 1678, 1668, 1604. dH (DMSO-d6)
By Method A, to give 8b as a beige powder (0.733 g; 74%), mp
176-177 ◦C. Found C 50.1, H 3.0, N 12.3. Calc. for C14H10BrN3O2
C 50.6, H 3.0, N 12.7%. nmax/cm-1 1664, 1624, 1495. dH (DMSO-
=
2.65 (3H, s, CH3), 6.24 (2H, d, J 10.1, HC ), 6.72 (1H, s, OH),
=
=
d6) 6.24 (2H, d, J 10.1, HC ), 6.68 (1H, s, OH), 7.23 (2H, d, J
7.24 (2H, d, J 10.1, HC ), 8.12 (2H, d, J 8.9, ArH), 8.18 (2H, d,
=
10.1, HC ), 7.82 (2H, d, J 8.9, ArH), 7.92 (2H, d, J 8.9, ArH),
J 8.9, ArH), 9.11 (1H, s, CHN). dC (DMSO-d6) 27.4, 65.7, 120.3,
121.9, 127.0, 130.6, 140.0, 150.0, 150.8, 185.6, 197.4. MS (ESI)
m/z 296 (M+H)+.
8.99 (1H, s, CHN). dC (DMSO-d6) 65.7, 121.8, 121.9, 122.5, 126.9,
133.3, 136.2, 149.8, 150.8, 185.6. MS (ESI) m/z 332 (M+H)+.
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4-(1-(4-Butylphenyl)-1H-1,2,3-triazol-4-yl)-4-hydroxycyclohexa-
2,5-dienone 8h
(3H, m, ArH). dC (CDCl3) 54.6, 66.2, 120.4, 127.8, 128.3, 129.1,
129.3, 133.9, 147.7, 148.3, 185.0. MS (ESI) m/z 268 (M+H)+.
By Method A, to give 8h as a beige powder (0.600 g; 95%), mp
162-163 ◦C. Found C 69.5, H 6.2, N 13.5. Calc. for C18H15N3O2 C
69.9, H 6.2, N 13.5%. nmax/cm-1 1668, 1628, 1518. dH (DMSO-d6)
0.92 (3H, t, J 7.4, CH3), 1.31-1.36 (2H, m, CH2), 1.56-1.62 (2H,
4-Hydroxy-4-(1-(3-phenylpropyl)-1H-1,2,3-triazol-5-yl)cyclohexa-
2,5-dienone 8m
By Method A, but the oil obtained from addition of water was ex-
tracted with ethyl acetate, and purified by column chromatography
(EtOAc) to give 8m as white flakes (0.440 g; 50%), mp 128-131 ◦C.
=
m, CH2), 2.67 (2H, t, J 7.7, ArCH2-), 6.23 (2H, d, J 10.1, HC ),
6.67 (1H, s, OH), 7.25 (2H, d, J 10.1, HC=), 7.42 (2H, d, J 8.5,
ArH), 7.82 (2H, d, J 8.5, ArH), 8.90 (1H, s, CHN). dC (DMSO-d6)
14.2, 22.2, 33.4, 34.7, 65.7, 120.5, 121.6, 126.8, 130.1, 134.9, 143.7,
149.5, 150.9, 185.7. MS (ESI) m/z 310 (M+H)+.
n
max/cm-1 1668, 1624. dH (CDCl3) 2.23-2.30 (2H, m, CH2), 2.68
(2H, t, J 7.4, CH2), 4.35 (2H, t, J 7.2, CH2), 6.26 (2H, d, J 10.1,
=
=
HC ), 7.04 (2H, d, J 10.1, HC ), 7.15-7.32 (5H, m, ArH), 7.41
(1H, s, CHN). dC (CDCl3) 31.5, 32.5, 50.0, 66.2, 120.8, 126.5,
127.7, 128.4, 128.7, 139.8, 147.3, 148.5, 185.0. HRMS (ES) calcd
for C17H18N3O2 (M+H+) 296.1399 found 296.1336.
4-(1-(Benzo[d]thiazol-6-yl)-1H-1,2,3-triazol-4-yl)-4-
hydroxycyclohexa-2,5-dienone 8i
By Method A, but the black oil obtained from addition of
water was extracted with ethyl acetate, and purified by column
chromatography (EtOAc) to give 8i as a cream powder (0.600 g;
95%), mp 216-220 ◦C. Found C 57.7, H 3.3, N 17.7. Calc. for
C15H10N4O2S C 58.1, H 3.3, N 18.1%. nmax/cm-1 1672, 1624, 1485.
4-Hydroxy-4-(1-(4-methoxybenzyl)-1H-1,2,3-triazol-4-
yl)cyclohexa-2,5-dienone 8n
By Method A, but the oil obtained from addition of water was
extracted with DCM, the organic layers dried (Mg SO4) and
concentrated, and the product crystallised from ethyl acetate–
hexane. (0.240 g; 27%), mp 86-88 ◦C. nmax/cm-1 1672, 1631, 1612,
1518, 1253. dH (DMSO-d6) 3.74 (3H, s, OMe), 5.50 (2H, s, PhCH2),
=
dH (DMSO-d6) 6.25 (2H, d, J 10.0, HC ), 6.72 (1H, s, OH), 7.26
=
(2H, d, J 10.0, HC ), 8.10-8.13 (1H, m, ArH), 8.29-8.31 (1H,
m, ArH), 8.82 (1H, d, J 2.1, ArH), 9.03 (1H, s), 9.54 (1H, s). dC
(DMSO-d6) 65.7, 115.0, 119.5, 122.2, 124.5, 126.9, 134.4, 135.4,
149.8, 150.9, 158.8, 185.6. MS (ESI) m/z 311 (M+H)+.
=
6.15 (2H, d, J 10.0, HC ), 6.48 (1H, s, OH), 6.94 (2H, d, J
=
8.5, ArH), 7.15 (2H, d, J 10.0, HC ), 7.32 (2H, d, J 8.5, ArH),
8.21 (1H, s, CHN). dC (DMSO-d6) 52.3, 55.6, 65.7, 114.6, 123.1,
126.5, 128.2, 130.3, 148.7, 151.2, 159.7, 185.7. MS (ESI) m/z 298
(M+H)+.
4-Hydroxy-4-(1-(pyridin-4-yl)-1H-1,2,3-triazol-4-yl)cyclohexa-
2,5-dienone 8j
By Method A, to give 8j as brown prisms (after allowing to stand
for several days) (0.763 g; 53%), mp 149-158 ◦C. nmax/cm-1 1661,
4-Hydroxy-4-(1-((2R,3S,4R,5S)-3,4,5-trihydroxy-6-
(hydroxymethyl)tetrahydro-2H-pyran-2-yl)-1H-1,2,3-triazol-5-
yl)cyclohexa-2,5-dienone 10a
=
1597. dH (DMSO-d6) 6.24 (2H, d, J 10.1, HC ), 6.72 (1H, s, OH),
=
7.20 (2H, d, J 10.1, HC ), 7.42 (2H, d, J 6.3, ArH), 8.01 (2H,
d, J 6.3, ArH). 8.79 (2H, d, J 6.3, ArH), 9.15 (1H, s, CHN) dC
(DMSO-d6) 65.8, 114.1, 121.8, 127.0, 143.0, 150.3, 150.6, 152.1,
185.6. MS (ESI) m/z 277 (M+Na)+.
By Method A, but the aqueous solution was concentrated to
give a brown oil, which was dissolved in methanol. Addition of
DCM resulted in the precipitation of a small amount of a brown
solid, which was filtered. Further addition of DCM, followed by
filtration, led to a colourless solution, which was concentrated
to form a white solid. On filtration from DCM, the white solid
immediately absorbed water, resulting in a colourless oil. dH (D2O)
3.48-3.69 (4H, m) 3.78-3.88 (2H, m), 5.65 (1H, d, J 9.2, H-1), 6.25
4-(1-Decyl-1H-1,2,3-triazol-4-yl)-4-hydroxycyclohexa-2,5-dienone
8k
By Method A, to give 8k as an off-white solid. (0.740; 78%), mp
86-87 ◦C. Found C 68.0, H 8.5, N 13.1. Calc. for C18H27N3O2
C 68.1, H 8.6, N 13.2%. nmax/cm-1 2918, 2580, 1670, 1633. dH
(DMSO-d6) 0.88 (3H, t, J 6.8, CH3), 1.23-1.29 (14H, m, 7 ¥ CH2),
1.78-1.81 (2H, m, CH2), 4.33 (2H, t, J 7.1, CH2N), 6.15 (2H, d,
=
=
(2H, d, J 10.0, HC ), 7.13 (2H, d, J 10.1, HC ), 8.25 (1H, s,
CHN). dC (H2O) 60.3, 65.7, 68.8, 72.2, 75.8, 78.8, 87.6, 122.8,
127.2, 147.3, 149.9, 187.8.
=
=
J 10.1, HC ), 6.45 (1H, s, OH), 7.16 (2H, d, J 10.1, HC ), 8.20
(1H, s, CHN). dC (DMSO-d6) 14.4, 22.5, 26.3, 28.8, 29.1, 29.3,
29.3, 30.1, 31.7, 50.0, 65.7, 123.1, 126.5, 148.4, 151.3, 185.7. MS
(ESI) m/z 318 (M+H)+.
(3S,4R,5S,6R)-2-(Acetoxymethyl)-6-(4-(1-hydroxy-4-
oxocyclohexa-2,5-dienyl)-1H-1,2,3-triazol-1-yl)tetrahydro-2H-
pyran-3,4,5-triyl triacetate 10b
By Method A to give 10b as a white powder (after allowing to
stand for several days) (0.376 g; 49%), mp 91-96 ◦C. nmax/cm-1
2920, 2852, 1751, 1674, 1633. dH (CDCl3) 1.90 (3H, s, CH3), 2.02
(3H, s, CH3), 2.06 (3H, s, CH3), 2.24 (3H, s, CH3), 4.15-4.24 (3H,
m, H-5, H-6), 5.24 (1H, dd, J 10.3, 3.3, H-3), 5.46 (1H, dd, J
10.3, 9.2, H-2), 5.55 (1H, d, J 3.3, H-4), 5.82 (1H, d, J 9.2, H-1),
4-(1-Benzyl-1H-1,2,3-triazol-4-yl)-4-hydroxycyclohexa-2,5-
dienone 8l
By Method A, to give 8l as a beige powder. (492 mg; 61%), mp 165-
167 ◦C. Found C 67.2, H 4.9, N 15.5. Calc. for C15H13N3O2 C 67.4,
H 4.9, N 15.7%. nmax/cm-1 1670, 1627. dH (CDCl3) 3.48 (1H, s,
=
6.27-6.33 (2H, m, HC ) dC (CDCl3) 20.3, 20.5, 20.7, 20.7, 61.2,
=
OH), 5.52 (2H, s, CH2), 6.23 (2H, d, J 10.1, HC ), 7.23 (2H, d, J
66.3, 66.7, 68.0, 70.5, 86.5, 119.6, 127.9, 128.2, 147.8, 148.1, 148.2,
=
10.1, HC ), 7.27-7.31 (2H, m, ArH), 7.39 (1H, s, CHN), 7.39-7.42
169.1, 169.8, 169.9, 170.4, 184.9. MS (ESI) m/z 530 (M+Na)+.
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General method for the synthesis of arylsulfonyl-substituted
1,2,3-triazoles 11a,b (Method B)
2,5-dienone17 (0.200 g, 1.297 mmol) was then added dropwise
over 5 min and the reaction mixture stirred for a further 2 h.
The reaction mixture was warmed to room temperature then
treated with a solution of ammonium chloride (0.5 g) in water
(10 mL) and stirred for 30 min. The mixture was then treated
with 1 M HCl (10 mL) and stirred for 2 h, then diluted with
EtOAc (40 mL), and the layers separated. The aqueous phase
was extracted with EtOAc (2 ¥ 40 mL) and the combined
organic layers were washed with 1 M HCl (2 ¥ 25 mL) and
sat. K2CO3 solution (4 ¥ 25 mL). The organic layer was dried
(MgSO4) and concentrated under vacuum. The resulting solid
was suspended in Et2O, then collected on a filter and dried
under vacuum to give 4-(1-benzenesulfonyl-4-phenylimidazol-2-
yl)-4-hydroxycyclohexa-2,5-dien-1-one (0.195 g, 38%), mp 135-
137 ◦C. Found C 64.0, H 4.2, N 6.8. Calc. for C21H16N2O4S C
64.3, H 4.1, N 7.1. nmax/cm-1 3292, 1659, 1614, 1370, 1175, 1150,
To a stirred mixture of an arylsulfonyl azide (5 mmol),
4-ethynyl-4-hydroxycyclohexa-2,5-diene-1-one 5 (0.80 g; 6 mmol)
and copper(I) iodide (95 mg; 0.5 mmol) in chloroform (10 mL)
at 0 ◦C was slowly added 2,6-lutidine (0.7 mL; 6 mmol). The
mixture was maintained at 0 ◦C for 1 h and then stirred at
◦
25 C for 12 h. The mixture was partitioned between DCM and
aqueous ammonium chloride and the combined organic layers
were separated, dried (MgSO4), concentrated, and the product
purified by column chromatography on silica gel (hexane–ethyl
acetate).
4-Hydroxy-4-(1-tosyl-1H-1,2,3-triazol-4-yl)cyclohexa-2,5-dienone
By method B, to give 11a as a beige powder (0.565 g; 34%), mp
100 ◦C (dec.). Found C 53.7, H 3.8, N 12.5. Calc. for C15H13N3O4S
C 54.4, H 4.0, N 12.7%. nmax/cm-1 1670, 1393. dH (CDCl3) 3.25
1055, 729 cm-1. dH (DMSO-d6) 6.24 (2H, d, J 9.3, HC ), 6.82
=
(1H, s, OH), 7.29-7.31 (1H, m, ArH), 7.37-7.41 (4H, m), 7.67-7.71
(2H, m, ArH), 7.79-7.82 (3H, m, ArH), 8.15 (2H, d, J 8.2, ArH),
8.48 (1H, d, J 0.5).
=
(3H, s, OCH3), 6.30 (2H, d, J 10.1, HC ), 7.01 (2H, d, J 10.1,
=
HC ), 7.43 (2H, d, J 8.4, ArH), 8.04 (2H, d, J 8.4, ArH), 8.13
(1H, s, CHN). dC (CDCl3) 21.9, 66.1, 120.9, 128.5, 129.0, 130.6,
In vitro MTT assays
132.5, 147.2, 147.3, 147.9, 184.6.
Compounds were prepared as 10 mM top stocks, in DMSO, and
stored at 4 ◦C. Human-derived cell lines (HCT 116 and HT29
colon carcinoma; MCF-7 and MDA 468 breast carcinoma, and
A549 lung adenocarcinoma) were routinely cultivated at 37 ◦C in
an atmosphere of 5% CO2 in RPMI 1640 medium supplemented
with 2 mM L-glutamine and 10% fetal calf serum and subcultured
twice weekly to maintain continuous logarithmic growth. Com-
pounds were evaluated against these cell lines according to the
method previously described.2
4-Hydroxy-4-(1-(4-methoxyphenylsulfonyl)-1H-1,2,3-triazol-4-
yl)cyclohexa-2,5-dienone
By method B, to give 11b as a beige powder (0.905 g; 52%) mp
105 ◦C (dec.). Found C 51.5, H 3.6, N 11.9. Calc. for C15H13N3O5S
C 51.9, H 3.8, N 12.1%. nmax/cm-1 1688, 1595, 1495, 1397. dH
=
(CDCl3) 3.92 (3H, s, OCH3), 6.29 (2H, d, J 10.1, HC ), 7.02 (2H,
=
d, J 10.1, HC ), 7.07 (2H, d, J 9.1, ArH), 8.08 (2H, d, J 9.1,
ArH), 8.12 (1H, s, CHN). dC (CDCl3) 56.0, 66.1, 115.3, 120.7,
126.3, 128.4, 131.5, 147.1, 147.3, 165.7, 184.6.
References
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4-hydroxycyclohexa-2,5-diene-1-one 5 (0.61 g; 4.55 mmol) in
deoxygenated (nitrogen gas) benzene (10 mL) was added
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=
(2H, d, J 10.1, HC ), 6.62 (2H, d, J 10.1, HC=), 7.12-7.14 (2H,
m, ArH), 7.33-7.35 (3H, m, ArH), 7.56 (1H, s, CHN). dC (CDCl3)
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2084 | Org. Biomol. Chem., 2010, 8, 2078–2084
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©