One-pot tandem Hurtley-retro-Claisen-cyclisation reactions in the synthesis of 3-substituted analogues of 5-aminoisoquinolin-1-one (5-AIQ), a water-soluble inhibitor of PARPs

Article abstract of DOI:10.1016/j.bmc.2013.06.031

Poly(ADP-ribose)polymerase-1 (PARP-1) is an important target for drug design for several therapeutic applications. 5-Aminoisoquinolin-1-one (5-AIQ) is a highly water-soluble lead compound; synthetic routes to 3-substituted analogues were explored. Tandem Hurtley coupling of β-diketones with 2-bromo-3-nitrobenzoic acid, retro-Claisen acyl cleavage and cyclisation gave the corresponding 3-substituted 5-nitroisocoumarins. Treatment with ammonia at high temperature and reduction with tin(II) chloride gave eleven target 3-substituted 5-AIQs, which were all soluble in water (>1% w/v) as their HCl salts. Most were more potent than 5-AIQ as inhibitors of PARP-1 and of PARP-2 in vitro, the most active being 5-amino-3-methylisoquinolin-1-one (PARP-1: IC ₅₀ = 0.23 μM vs IC₅₀ = 1.6 μM for 5-AIQ). Some rationalisation of the SAR was achieved through molecular modelling.

Full text of DOI:10.1016/j.bmc.2013.06.031

Bioorganic & Medicinal Chemistry 21 (2013) 5218–5227
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Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
One-pot tandem Hurtley–retro-Claisen–cyclisation reactions
in the synthesis of 3-substituted analogues of 5-aminoisoquinolin-
1-one (5-AIQ), a water-soluble inhibitor of PARPs
Esther C. Y. Woon , Peter T. Sunderland, Helen A. Paine, Matthew D. Lloyd, Andrew S. Thompson,
⇑
Michael D. Threadgill
Medicinal Chemistry, Department of Pharmacy & Pharmacology, University of Bath, Claverton Down, Bath BA2 7AY, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
Poly(ADP-ribose)polymerase-1 (PARP-1) is an important target for drug design for several therapeutic
applications. 5-Aminoisoquinolin-1-one (5-AIQ) is a highly water-soluble lead compound; synthetic
routes to 3-substituted analogues were explored. Tandem Hurtley coupling of b-diketones with
2-bromo-3-nitrobenzoic acid, retro-Claisen acyl cleavage and cyclisation gave the corresponding 3-
substituted 5-nitroisocoumarins. Treatment with ammonia at high temperature and reduction with
tin(II) chloride gave eleven target 3-substituted 5-AIQs, which were all soluble in water (>1% w/v) as their
HCl salts. Most were more potent than 5-AIQ as inhibitors of PARP-1 and of PARP-2 in vitro, the most
Received 25 April 2013
Revised 7 June 2013
Accepted 12 June 2013
Available online 22 June 2013
Keywords:
PARP-1
Hurtley reaction
Tandem
Isocoumarin
Isoquinolin-1-one
active being 5-amino-3-methylisoquinolin-1-one (PARP-1: IC50 = 0.23
lM vs IC50 = 1.6 lM for 5-AIQ).
Some rationalisation of the SAR was achieved through molecular modelling.
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
O
O
H
H
N
H
N
N
The poly(ADP-ribose)polymerases (PARPs) comprise a super-
family of enzymes which use NAD+ to generate electrophilic
ADP-ribose units to attach to substrate proteins to build poly anio-
nic poly(ADP-ribose) polymers.1 Two of the isoform members of
this superfamily, the archetypal PARP-1 and PARP-2, detect sites
of damage in DNA and use this poly(ADP-ribosyl)ation to open
the chromatin structure and initiate and regulate repair of
DNA.1–3 Other members of the superfamily (e.g., PARP-3, PARP-4
(vault mPARP) and PARPs-5a,b (the tankyrases) have other regula-
tory functions within the cell.1–6 Inhibitors of PARP-1 are in clinical
trial for the treatment of cancer7–9 and have demonstrated benefi-
cial activity in experimental models in a range of other therapeutic
applications, including inflammation,10,11 organ damage following
ischaemia–reperfusion,12,13 neurological damage,14,15 organ trans
plant16 and multiple sclerosis.17
O
F
N
HN
H
NH
N
N
O
1
2
olaparib
veliparib
O
O
H
H
N
N
HN
NH2
The known pharmacophore for optimum inhibition of PARP-1
comprises a lactam fused to an aromatic ring (e.g., quinazolin-4-
one, isoquinolin-1-one or phthalazin-1-one) or a similar primary
benzamide where the conformation of the C@O–NH is held in the
plane of the benzene ring by an intramolecular hydrogen bond. This
NHMe
rucaparib
3
4
5-AIQ
Figure 1. Structures of three inhibitors of PARP-1 in advanced clinical trial and of
5-AIQ.
benzamide amide motif is required for hydrogen bonding to the
⇑
Corresponding author. Tel.: +44 1 225 386 840; fax: +44 1 225 386 114.
conserved Gly863 and Ser904 and
p
-stacking with Tyr907 in the
E-mail address: m.d.threadgill@bath.ac.uk (M.D. Threadgill).
Present address: Department of Pharmacy, National University of Singapore,
Block S4, Science Drive 4, Singapore 117543, Republic of Singapore.
(NAD+)-nicotinamide-binding site. The clinical candidates olaparib
1, veliparib 2 and rucaparib 3 (Fig. 1) fit this model. 5-Aminoiso-
0968-0896/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmc.2013.06.031

E. C. Y. Woon et al. / Bioorg. Med. Chem. 21 (2013) 5218–5227
5219
quinolin-1-one (5-AIQ, 4, Fig. 1) is an inhibitor of PARP-1 and PARP-
2, which is highly water-soluble as its hydrochloride salt. Interest-
ingly, 4 shows potent therapeutic activity in models in vivo of a
range of diseases and disorders, including haemorrhagic shock,18
myocardial in farction,12 colitis19 and cerebral ischaemia.15 In the
context of cancer, it inhibits angiogenesis20 (PARP-1 regulates
general route to 3-substituted-5-nitroisocoumarins and, hence, to
3-substituted analogues of 4.
In 1929, Hurtley reported the displacement of the halogen from
2-bromobenzoic acid with the enolates of b-diketones and of
b-ketoesters in the presence of copper catalysts to form the
corresponding arylated b-dicarbonyl compound.28 He noted ‘The
presence of copper–bronze or copper acetate is necessary; the
latter appears to be the more vigorous catalyst, but the former
gives purer products and was used where possible.’ Later mecha-
nistic studies have not proved fully conclusive.29 Most have deter-
mined that the carboxylate of the aryl component is essential and
that bromine is the optimum halogen.29,30 Ames and Ribeiro
extended this process by forcing a retro-Claisen condensation
and ring closure on the Hurtley products with sodium chloride at
170 °C to give isocoumarins in moderate yields, making the
3-substituted isocoumarins available in two steps from 2-bromo-
benzoic acid and pentane-2,4-dione or 1,3-diphenylpropane-1,
3-dione.31 Very recently, Cai et al. developed a one-pot synthesis
of 3-substituted isocoumarins by reaction of 2-iodo- or 2-bromo-
benzoic acid with b-diketones, catalysed by copper(I) iodide and
potassium phosphate in dimethylformamide under forcing condi-
tions in a sealed tube.32 No 5-substituted analogues were reported.
This tandem process has been extended to use of 2-iodobenzani-
lides, in place of 2-bromobenzoic acid, but Kavala et al. note that
isocoumarins carrying nitro groups are unstable to the reaction
conditions.33 We therefore sought to expand the tandem
Hurtley–retro-Claisen–cyclisation reaction to the one-pot synthe-
sis of 5-nitro-3-substituted isocoumarins without recourse to
sealed tubes.
NF-j
B) and is potently antimetastatic,21 inter alia. Exploring the
structure–activity relationships around this core, we have reported
that 4-aryl-5-AIQs and 5-benzamidoisoquinolin-1-ones are iso-
form-selective inhibitors of PARP-2.22,23 6-Aryl thieno[3,4-c]pyri-
din-4(5H)ones inhibit PARP-1,24 so we proposed that the
analogous 3-substituted-5-AIQs should be explored.
We have previously reported the synthesis of 4 by condensation
of methyl 2-methyl-3-nitro benzoate with dimethylformamide
dimethyl acetal (DMFDMA) to give 5-nitroisocoumarin, followed
by conversion to 5-nitroisoquinolin-1-one with ammonia and
reduction of the nitro group.18 However, this method could not
be extended to the 3-methyl analogue25 and extension to the
3-aryl analogues was precluded by difficulty in accessing the
required benzamide acetals. 3-Aryl-5-nitroiso coumarins 5 have
been accessed by Castro–Stevens coupling of 2-iodo-3-nitroben-
zoic acid 6 with arylethynes, followed by cyclisation in situ
(Scheme 1) but this process was limited to three examples.26
Sonogashira coupling of methyl 2-iodo-3-methylbenzoate 7 with
phenylethynes was investigated, followed by cyclisation with
Hg2+ as catalyst but this was only effective for one example
(R3 = Ph).26 A more general but low-yielding method involved
Friedel–Crafts acylation of 5-nitroisocoumarin
9 with aroyl
chlorides under forcing conditions in nitrobenzene, followed by
in situ rearrangement and decarboxylation; this was limited to
benzoyl chloride and aroyl chlorides carrying electron-withdraw-
ing para-substituents.27 There is therefore a need for a more
2. Results & discussion
2-Bromo-3-nitrobenzoic acid 10 (Scheme 2) was prepared by
mercury-catalysed decarboxylation of 3-nitrobenzene-1,2-dioic
acid (3-nitrophthalic acid), followed by treatment of the inter
mediate aryl-mercury with bromine,34 by analogy with our previ-
ous method for 2-iodo-3-nitrobenzoic acid.26 Many of the b-dicar-
bonyl components were commercially available but Claisen
condensations, either base-catalysed (sodamide) or Lewis-acid cat-
alysed (boron trifluorideÁacetic acid complex), were used to supply
others.
As a preliminary study to establish suitable reaction conditions
for the reaction, 10 was treated with the tri fluoromethylphenyl
b-diketone 11a, using Hurtley’s original reaction conditions
(copper powder, with sodium ethoxide as base in boiling etha-
nol)28 (Scheme 2). The isocoumarin 12a was isolated in modest
O
O
CO2H
O
O
i
iv
R3
I
NO2
NO2
iii
NO2
6
5
9
CO2Me
ii
CO2Me
I
NO2
NO2
R3
7
8
Scheme 1. Earlier syntheses of 3-substituted-5-nitroisocoumarins 5. Reagents and
conditions: (i) CuC„CR3, pyridine, reflux (R3 = Ph, 4-MePh, 4-MeOPh); (ii) HC„CPh,
CuI, (Ph3P)2PdCl2, Pri2NH, THF; (iii) HgSO4, H2SO4, acetone, reflux; iv, R3COCl, SnCl4,
PhNO2. 130 °C (R3 = Ph, Ph-(EWG)).
yield, through
a
tandem Hurtley–retro-Claisen–cyclisation
sequence. The mono-ketone 13 and the ester 14 were also obtained
as by-products. Interestingly, there was no evidence for formation
O
O
O
O
O
CO2H
Me
i
Me
EtO
CF3
O
CF3
CF3
Br
NO2
O2N
O2N
10
11a
12a
CF3
13
14
O
O
NO2
O
Me
CF3
CF3
15
16
Scheme 2. Initial investigation of tandem Hurtley–retro-Claisen–cyclisation reaction of 10 with 11 under Hurtley’s conditions. Reagents and conditions: (i) Cu powder,
NaOEt, EtOH, reflux.

5220
E. C. Y. Woon et al. / Bioorg. Med. Chem. 21 (2013) 5218–5227
of 3-methyl-5-nitroisocoumarin, arising from an alternative
retro-Claisen reaction in the sequence, nor were the intermediate
arylated diketone 15 and the intermediate retro-Claisen product
16 observed in the product mixture. Compounds 13 and 14 are
products of retro-Claisen cleavage of the starting b-diketone 11a.
This suggests that the base, ethoxide, may be too nucleophilic, in
that it attacks the carbonyls of 11a before the Hurtley coupling
can take place, consuming 11a and thereby lowering the yield of
12a.
Replacement of the base with the less nucleophilic potassium
t-butoxide and the solvent with t-butanol obviated the
premature retro-Claisen cleavage (Scheme 3), providing mixtures
of the required 3-substituted 5-nitroisocoumarin 12a–h and the
3-methyl analogue 12g, arising from an alternative retro-Claisen
cleavage as the second step. These were readily separated by col-
umn chromatography. As shown in Table 1, the yields of 12a–h
were poor-to-modest. Rationalising that material was being lost
through the alternative retro-Claisen cleavage of the R3CO group,
we examined the tandem Hurtley–retro-Claisen–cyclisation reac-
tion sequence with symmetrical b-diketones 17b,d,h–k (Scheme 4).
As for the unsymmetrical analogues 11, these were either commer-
cially available (17b) or prepared by Claisen condensations.
Interestingly, during the assembly of the dibenzyl symmetrical
b-diketone 17i from ketone 18 and ester 19, a quantity of the
homo-Claisen product 20 was also formed, reflecting the acidity
CO2H
O
O
Br
O
Me
R3
NO2
10
11a-h
i
of the
a-pro tons in the intended electrophilic component 19
O
(Scheme 4). The yields of the required 3-alkyl and 3-aryl 5-nitro-
isocoumarins 12 were markedly higher when the symmetrical
diketones were employed (Table 1), using the same reaction condi-
tions (potassium t-butoxide in t-butanol). In cases where both
methods were examined for the same target 12a,d,h, the yield
for the tandem reaction with the symmetrical diketones 17 was
much higher. Indeed, the yields exceeded the sums of the yields
of (desired isocoumarins + 12g), suggesting that not only was the
problem of the wrong acyl group being lost in the retro-Claisen
step being resolved but also that the initial Hurtley reaction was
proceeding better with the enolates of 17. The dialkyl symmetrical
b-diketones 17g–k gave lower yields than the diaryl analogues
17b,d.
O
O
R3
Me
NO2
12a-h
NO2
12g
a: R3 = 4-F3CPh; b: R3 = Ph;
c: R3 = 4-MePh; d: R3 = 4-MeOPh;
e: R3 = 4-ClPh; f: R3 = thiophen-2-
yl; g: R3 = Me; h: R3 = pentyl
Scheme 3. Tandem Hurtley–retro-Claisen–cyclisation reactions of 10 with methyl
b-diketones 11a–h to form 3-substituted 5-nitro-iso-coumarins 12a–h. Reagents
and conditions: (i) Cu powder, KOBut, ButOH, reflux.
Table 1
Yields of 5-nitroisocoumarins 12 formed in the tandem Hurtley coupling ? retro-Claisen ? cyclisation reactions from 10 and unsymmetrical (11) and symmetrical (17)
b-diketones
Isocoumarin 3-substituent
Reaction of 10 with unsymmetrical diketones 11 (KOBut/ButOH)
Reaction of 10 with symmetrical diketones 17 (KOBut/ButOH)
Yield of target isocoumarin (%)
Yield of 12g (%)
Yield of target isocoumarin (%)
4-F3CPh
Ph
16 (12a)
4 (12b)
21 (12c)
15 (12d)
33 (12e)
21 (12f)
—
4 (12h)
ND
ND
6
8
3
6
4
0
—
0
ND
ND
ND
ND
78 (12b)
ND
60 (12d)
ND
ND
23 (12g)
26 (12h)
32 (12i)
24 (12j)
26 (12k)
4-MePh
4-MeOPh
4-ClPh
Thiophen-2-yl
Me
Pentyl
Bn
Et
CH2CHMe2
ND
ND = not determined.
O
O
CO2H
3
3
3
b d g
: R = Ph; : R = 4-MeOPh; : R
O
O
i
3
3
h
i
j
= Me; : R = pentyl; : R = Bn; :
R3
R3
Br
R3
R3 = Et; k: R3 = Me2CHCH2
NO2
10
NO2
11g,17b,d,h-k
12b,d,g-k
O
O
O
O
ii
Me
CO2Et
CO2Et
18
19
17i
20
Scheme 4. Tandem Hurtley–retro-Claisen–cyclisation reactions of 10 with symmetrical b-diketones 11g, 17b,d,h–k to form 3-substituted 5-nitro isocoumarins 12b,d,g–k
and synthesis of symmetrical b-diketone 17i. Reagents & conditions: (i) Cu powder, KOBut, ButOH, reflux; (ii) NaNH2, Et2O, reflux.

E. C. Y. Woon et al. / Bioorg. Med. Chem. 21 (2013) 5218–5227
5221
Thus the tandem reaction provided sufficient quantities of the
isocoumarins 17a–k for the remainder of the reaction sequence.
Notably, the sequence proceeds with alkyl b-diketones and with
aryl groups carrying electron-neutral, +M and ÀI para-substituents
but it fails completely with ÀM substituents on the aryl group,
such as nitro and cyano.
nuclear preparation (300 nM) and that reported by Suto et al.37
(250 nM) from a calf-thymus preparation assay. Differences in
absolute values of IC50 between assay types are well known for
PARP-1 inhibition. All the 3-substituted 5-aminoisoquinolinones
inhibited PARP-1 activity, with many having IC50 values in the
0.2–1.0 lM range. Indeed, all except 22f,i were more potent than
The 5-nitroisocoumarins 12 were readily converted into the
corresponding 5-nitroisoquinolin-1-ones 21 by reaction with
ammonia in boiling 2-methoxyethanol (Scheme 5), obviating the
use of sealed tubes for the more usual transformation in ethanol.
The yields were mostly good-to-high. Reduction of the nitro group
to furnish the target 3-substituted 5-aminoisoquinolin-1-ones 22
was effected with tin(II) chloride. For one example, 21a, catalytic
hydrogenation was also explored but gave practical problems of
separating the product 22a efficiently from the catalyst.
the lead com pound 4. Generally, the simpler 3-alkyl compounds
22g,h,j were slightly more potent than the 3-phenyl compound
22b; this is in line with similar effects noted by White et al.38 that
8-methoxy-2-methylquinazolin-4-one is ca. fivefold more potent
than is 8-meth oxy-2-phenylquinazolin-4-one. Introduction of
branching in the 3-alkyl chain, in the isobutyl analogue 22k and
the benzyl analogue 12i, however, caused some loss of activity. A
phenyl substituent is accepted at the 3-position (in 22b), showing
that steric bulk is unlikely to be the simple explanation of the
weaker activity of 22i,k. Curiously, the introduction of a thiophene
ring at the 3-position resulted in a loss of potency in 22f, despite the
usually accepted pharmacoequivalence of benzene and thiophene.
Selected compounds were also assayed for their inhibition of
PARP-2 activity (Table 2), using the assay previously reported by
us.23 Most of the analogues tested showed slightly greater potency
against PARP-2 but the selectivity was not large enough to allow
use in biochemical studies as selective inhibitors.
3. Biochemical evaluation
All the hydrochloride salts of 5-aminoisoquinolin-1-ones 22a–k
showed good water-solubility (>1% w/v; >30 mM). Each was eval-
uated in vitro for activity against human PARP-1 isolated from
HeLa nuclear extract, using the KuDOS FlashPlate scintillation
proximity assay method.35 This isotopic assay measures PARP-1
activity through synthesis of [3H]-ADP-ribose polymers from
[3H]-NAD+. Tritium bound to the FlashPlate was counted using a
scintillation plate reader. In this study, five different concentra-
tions of the inhibitor, in a range surrounding the predicted IC50 va-
lue, were used. Three independent determinations were per
formed for each candidate inhibitor 22a–k; the mean IC50 values
are reported in Table 2.
4. Molecular modelling studies
The structures of the 3-substituted 5-AIQs 22a–k were overlaid
with the structure of the known inhibitor 8-hydroxy-2-methylqui-
nazolin-4-one bound into the NAD+-binding site of the catalytic
domain of chicken PARP-1 derived from co-crystal X-ray data re-
trieved from the Brookhaven Protein Data Bank (PDB code:
4PAX), using Tripos Associates SYBYL software on a SGI Octane II
workstation. The 3-substituted 5-AIQ derivatives were initially
positioned such that the central rings were overlaid with the 8-hy-
droxy-2-methylquinazolin-4-one rings; the side chains were then
subjected to molecular mechanics and molecular dynamics calcu-
lations while restraining the binding pocket and the heterocyclic
core; the temperature was ramped to 300 K over 10 ps, then held
at 300 K for a further 20 ps. Once an optimal orientation had been
established for the side-chains, the restraints were removed and
the whole binding pocket (10 Å) was subjected to further molecu-
lar dynamics (20 ps at 300 K) and then refined with mechanics cal-
culations, allowing free movement of both the ligands and the
binding pocket. Examples of illustrations generated by these calcu-
lations are shown in Figure 2. As expected, each isoquinolin-1-one
could make hydrogen bonds from the carbonyl oxygen to the side-
chain O–H of Ser904 and to the backbone N–H of Gly863. For exam-
ple, in the minimised position for the most potent compound, 22g,
this oxygen was located 2.25 Å from the latter and 1.59 Å from the
former (Fig. 2A). The isoquinolin-1-one N–H was also located
appropriately for a strong hydrogen bond to the backbone carbonyl
of Gly863, as exemplified for 22g in Figure 2A with a distance of
2.08 Å. These hydrogen-bonding interactions are common in the
modelled and co-crystal structures of inhibitors. It was also ob-
served that the 5-NH2 in these inhibitors was well accommodated
within a small binding pocket and was orientated and located
appropriately for a water-mediated hydrogen bond to the carbox-
ylate of the important catalytic Glu988 in the active site; an ordered
water molecule is located in this position in several crystal struc-
tures. The core aromatic isoquinolin-1-one rings of 22a–k also
In this assay, the mean IC50 value for PARP-1 inhibition by the
lead compound, 5-AIQ 4, was found to be 1.6
lM, which is higher
than that reported previously by us36 for an assay in a broken
O
O
O
H
H
O
N
N
i
ii
R3
21a-k
R3
R3
NO2
NO2
NH2
12a-k
22a-k
3
3
3
3
a
b
c
d
: R = 4-F3CPh; : R = Ph; : R = 4-MePh; : R
=
=
3
3
e
f
g
4-MeOPh; : R = 4-ClPh; : R = thiophen-2-yl; :
R3 = Me; h: R3 = pentyl; i: R3 = Bn; j: R3 = Et; k: R3
Me2CHCH2
Scheme 5. Conversion of the 5-nitroisocoumarins 12a–k into 5-aminoisoquinolin-
1-ones 22a–k. Reagents: (i) NH3, MeO(CH2)2OH, reflux; (ii) SnCl2, EtOH or H2, Pc/C,
EtOH, aq HCl.
Table 2
IC50 values for inhibition of human PARP-1 and murine PARP-2 by 3-substituted
5-amino-iso-quinolin-1-ones
Compd No.
3-Substituent
PARP-1 IC50
(lM)
PARP-2 IC50 (lM)
4
H
1.6 0.25
0.33 0.07
1.07 0.07
0.88 0.14
0.90 0.45
0.57 0.03
5.61 2.20
0.23 0.02
0.32 0.17
5.14 1.60
0.49 0.04
1.17 0.56
1.05 0.15
0.17 0.02
0.48 0.15
0.12 0.03
0.73 0.25
0.16 0.05
ND
0.26 0.05
ND
ND
22a
22b
22c
22d
22e
22f
22g
22h
22i
22j
22k
4-F3CPh
Ph
4-MePh
4-MeOPh
4-ClPh
Thiophen-2-yl
Me
Pentyl
Bn
Et
formed a
p-stack with the electron-rich aromatic side-chain of
Tyr907, as is common for PARP-1 inhibitors (illustrated for 22g in
Fig. 2B). Notably, the bulk of the sulfur in 22f (Fig. 2C) may possibly
interfere with the critical hydrogen bond from the inhibitor N–H to
Gly863 of the enzyme, diminishing its potency.
0.83 0.10
ND
CH2CHMe2
ND = not determined.

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E. C. Y. Woon et al. / Bioorg. Med. Chem. 21 (2013) 5218–5227
Gly863
A
B
C
Ser904
Ser904
Gly863
Gly863
Ser904
Tyr907
Glu988
Glu988
D
E
Figure 2. Illustrations of modes of binding of selected examples in the NAD+-binding site of chicken PARP-1, as predicted by molecular modelling. (A) Binding of 22g, showing
hydrogen bonds to Gly863 and Ser904 (green solid lines) and the proximity of the 5-amine to the carboxylate of Glu988 (green dotted line). (B) Binding of 22g, showing
p
-stacking to Tyr907. (C) Binding of 22f, showing hydrogen bonds to Gly863 and Ser904 and potential steric obstruction by the sulfur. (D) View of binding of 22g, showing
insertion of the 3-Me into a pocket. (E) View of binding of 22a, showing insertion of the 3-(4-trifluoromethylphenyl) into a pocket.
These modelling studies indicated that the 3-substituents of
22a–k should occupy hydrophobic pocket. Figure 2D
6. Experimental
6.1. Chemistry
a
shows the 3-methyl of 22g entering shallowly into this space,
whereas the 3-(4-trifluoromethylphenyl) of 22a appears to
fill the pocket (Fig. 2E), reflecting the increased inhibitory
potency of these and closely related compounds when compared
with 4.
Mps were determined using a Reichert-Jung Thermo Galen
Kofler block and are uncorrected. IR spectra were recorded on a
Perkin–Elmer RXI FT-IR spectrometer as KBr discs. NMR spectra
were recorded on either
a
JEOL GX 270 (270.05 MHz 1H;
67.8 MHz 13C) or a JEOL EX 400 (399.65 MHz 1H; 100.4 MHz 13C;
376.05 MHz 19F) spectrometer. Mass spectra were obtained using
a VG 7070 mass spectrometer. Column chromatography was per-
formed using silica gel 60 (0.040–0.063 mm, Merck). Experiments
were conducted at ambient temperature, unless otherwise stated.
Solutions in organic solvents were dried using anhydrous MgSO4
and solvents were evaporated under reduced pressure.
5. Conclusion
This paper reports a one-pot tandem Hurtley–retro-Claisen–
cyclisation reaction sequence, which is useful in preparing 3-aryl
and 3-alkyl 5-nitroisocoumarins 12. These are important interme-
diates in accessing the corresponding 3-aryl and 3-alkyl 5-amino-
isoquinolin-1-ones 22. The tandem sequence can be carried out
with either unsymmetrical or symmetrical b-diketones. The whole
preparation of the targets 22 is achieved without recourse to sealed
tubes, particularly for the Hurtley step and for the isocoumarin-
to-isoquinolinone step, which have previously required such spec-
ialised equipment.32,39 This new sequence tolerates most groups,
except ÀM substituents on the aryl units in diaryl-b-diketones.
It is therefore complementary to our one-pot formation of
3-aryl-5-nitroisocoumarins by Friedel–Crafts acylation of 5-
nitroisocoumarin, rearrangement and decarboxylation, for which
ÀM substituents are optimal.27
6.1.1. 5-Nitro-3-(4-trifluoromethylphenyl)isocoumarin (12a).
Method A
Compound 1034 (2.5 g, 10 mmol) and Cu powder (220 mg,
3.5 mmol) were added to 11a40 (3.5 g, 15 mol) and NaOEt (1.6 g,
23 mmol) in EtOH (35 mL). The mixture was boiled under reflux
for 16 h, then poured into H2O and acidified with aq HCl (2 M).
Extraction (Et2O), evaporation and chromatography (hexane/EtOAc
4:1) gave 12a (160 mg, 5%) as yellow crystals, with data as below.
Further elution gave 13 (210 mg, 11%) as a colourless oil (lit.41 oil):
1H NMR (CDCl3) d 2.56 (3H, s, Me), 7.55 (2H, d, J = 8.2 Hz, Ph 3,5-
H2), 8.14 (2H, d, J = 8.2 Hz, Ph 2,6-H2). Further elution gave 14
(130 mg, 6%) as a colourless oil (lit.42 oil): 1H NMR (CDCl3) d 1.41
(3H, t, J = 7.2 Hz, Me), 4.41 (2H, q, J = 7.2 Hz, CH2), 7.75 (2H, d,
J = 8.2 Hz, 3,5-H2), 8.16 (2H, d, J = 8.2 Hz, 2,6-H2).
Many of the 3-substituted 5-AIQ derivatives 22a–k showed
moderately more potent inhibition of the enzymatic activities of
PARP-1 and PARP-2 than the parent 4, although there was no selec-
tivity evident for either isoform. As demonstrated by molecular
modelling, the 3-substituents entered a modestly-sized hydropho-
bic pocket in both enzymes. The ready access to these structures
through the tandem Hurtley–retro-Claisen–cyclisation reaction se-
quence now enables further structure–activity studies for design
and discovery of new inhibitors of these clinically important
enzymes.
6.1.2. 5-Nitro-3-(4-trifluoromethylphenyl)isocoumarin (12a)
and 3-methyl-5-nitro isocoumarin (12g). Method B
Compound 1034 (3.6 g, 16 mmol) was boiled under reflux with
11a (760 mg, 3.1 mmol), KOBut (700 mg, 6.3 mmol) and Cu powder

E. C. Y. Woon et al. / Bioorg. Med. Chem. 21 (2013) 5218–5227
5223
(20 mg, 0.3 mmol) in ButOH (50 mL) for 16 h. The mixture was
poured into H2O (350 mL) and was acidified with aq HCl (2 M).
Extraction (Et2O), evaporation and chromatography (hexane/EtOAc
9:1) gave 12a (160 mg, 16%) as yellow crystals: mp 163–164 °C
6.1.8. 3-(4-Chlorophenyl)-5-nitroisocoumarin (12e). Method A
Compound 1034 was treated with 11e, Cu and KOBut in ButOH,
as for the synthesis of 12a (Method B) (chromatographic eluent:
hexane/EtOAc 8:1) to give 12e (33%) as pale yellow crystals: mp
204–205 °C; (lit.27 mp 204–205 °C); 1H NMR (CDCl3) d 7.47 (2H,
d, J = 6.6 Hz, Ph 3,5-H2), 7.62 (1H, t, J = 8.0 Hz, 7-H), 7.87 (2H, d,
J = 6.9 Hz, Ph 2,6-H2), 7.88 (1H, br s, 4-H), 8.50 (1H, dd, J = 8.3,
1.9 Hz, 6-H), 8.63 (1H, br d, J = 8.0 Hz, 8-H); 13C NMR d (Cq not ob-
served) 96.62, 127.23, 127.50, 129.44, 131.74, 135.92; MS (EI) m/z
303.0111 (M) (C15H837ClNO4 requires 303.0112), 301.0137 (M)
(C15H835ClNO4 requires 301.0142). Further elution yielded 12g
(4%) as yellow crystals, with data as below.
(lit.27 mp 163–164 °C); IR mmax 1724, 1626, 1537, 1344 cmÀ1 1H
;
NMR (CDCl3) d 7.67 (1H, t, J = 8.2 Hz, 6-H), 7.75 (2H, d, J = 8.2 Hz,
Ph 3,5-H2), 7.93 (1H, d, J = 0.8 Hz, 4-H), 8.03 (2H, d, J = 8.2 Hz, Ph
2,6-H2), 8.51 (1H, dd, J = 8.2, 1.6 Hz), 8.57 (1H, ddd, J = 8.2, 1.6,
0.8 Hz, 8-H); 19F NMR (CDCl3) d À63.54 (s, CF3). Further elution
yielded 12g (40 mg, 6%) as yellow crystals, with data as below.
6.1.3. 5-Nitro-3-phenylisocoumarin (12b) and 3-methyl-5-
nitroisocoumarin (12g). Method A
Compound 1034 was treated with 11b, Cu and KOBut in ButOH,
as for the synthesis of 12a (Method B) (chromatographic eluent:
hexane/EtOAc 10:1) to give 12b (4%) as yellow crystals: mp 142–
6.1.9. 5-Nitro-3-(thiophen-2-yl)isocoumarin (12f)
Compound 1034 was treated with 11f,44 Cu and KOBut in ButOH,
as for the synthesis of 12a (Method B) (chromatographic eluent:
hexane/EtOAc 8:1) to give 12f (21%) as pale yellow crystals: mp
143 °C (lit.26 mp 142–143 °C); IR mmax 1739, 1525, 1341 cmÀ1 1H
;
NMR (CDCl3) d 7.50–7.53 (3H, m, Ph 3,4,5-H3), 7.62 (1H, t,
J = 7.8 Hz, 7-H), 7.89 (1H, d, J = 0.8 Hz, 4-H), 7.93–7.97 (2H, m, Ph
2,6-H2), 8.51 (1H, dd, J = 8.2, 1.2 Hz, 6-H), 8.65 (1H, dt, J = 8.2, 1.2,
0.8 Hz, 8-H); MS (EI) m/z 267.0532 (M) (C15H9NO4 requires
267.0532). Further elution yielded 12g (170 mg, 8%) as yellow
crystals, with data as below.
189–190 °C; IR m
max 1744, 1619, 1530, 1338 cmÀ1; 1H NMR (CDCl3)
d 7.15 (1H, dd, J = 5.1, 3.9 Hz, thiophene 4-H), 7.50 (1H, dd, J = 5.1,
1.2 Hz, thiophene 5-H), 7.55 (1H, t, J = 8.2 Hz, 7-H), 7.71 (1H, dd,
J = 3.9, 1.2 Hz, thiophene 3-H), 7.71 (1H, d, J = 0.8 Hz, 4-H), 8.47
(1H, dd, J = 8.2, 1.2 Hz, 6-H), 8.59 (1H, ddd, J = 8.2, 1.2, 0.8 Hz,
8-H); MS (EI) m/z 273.0088 (M) (C13H7NO4S requires 273.0096).
6.1.4. 5-Nitro-3-phenylisocoumarin (12b). Method B
Compound 1034 (5.0 g, 20 mmol) and Cu powder (150 mg,
2.4 mmol) were added to 17b (22.9 g, 102 mmol) and KOBut
(4.6 g, 41 mmol) in ButOH (100 mL). The mixture was boiled under
reflux for 16 h, then poured into water and acidified with aq HCl
(2 M). This suspension was extracted (Et2O). Evaporation and chro-
matography (hexane/EtOAc 10:1) gave 12b (4.2 g, 78%) as yellow
crystals, with data as above.
6.1.10. 3-Methyl-5-nitroisocoumarin (12g)
Compound 1034 was treated with 11g, Cu and KOBut in ButOH,
as for the synthesis of 12a (Method B) (chromatographic eluent:
hexane/EtOAc 3:2) to give 12g (23%) as yellow crystals: mp 199–
200 °C (lit.23 mp 199–200 °C); IR mmax 1746, 1648, 1520,
1331 cmÀ1 1H NMR (CDCl3) d 2.37 (3H, s, Me), 7.13 (1H, d,
;
J = 0.8 Hz, 4-H), 7.55 (1H, t, J = 8.2 Hz, 7-H), 8.41 (1H, dd, J = 8.2,
1.2 Hz, 6-H), 8.56 (1H, ddd, J = 8.2, 1.2, 0.8 Hz, 8-H); 13C NMR d
20.46, 98.36, 121.92, 126.88, 131.36, 131.84, 135.74, 143.85,
158.63, 160.83; MS (EI) m/z 205.0384 (M) (C10H7NO4 requires
205.0375); Anal. Calcd for C10H7NO4: C, 58.54; H, 3.44; N, 6.83.
Found: C, 58.3; H, 3.47; N, 6.78.
6.1.5. 3-(4-Methylphenyl)-5-nitroisocoumarin (12c)
Compound 1034 (22.7 g, 100 mmol) was treated with 11c, Cu
and KOBut in ButOH, as for the synthesis of 12a (Method B) (chro-
matographic eluent: hexane/EtOAc 10:1) to give 12c (21%) as pale
yellow crystals: mp 180–181 °C (lit.27 mp 181–182 °C); 1H NMR
(CDCl3) d 2.42 (3H, s, Me), 7.29 (2H, d, J = 8.6 Hz, Ph 3,5-H2), 7.57
(1H, t, J = 8.2 Hz, 7-H), 7.82 (1H, s, 4-H), 7.83 (2H, d, J = 8.4 Hz, Ph
2,6-H2), 8.48 (1H, br d, J = 8.2 Hz, 6-H), 8.61 (1H, br d, J = 8.5 Hz,
8-H). Further elution yielded 12g (3%), with data as below.
6.1.11. 5-Nitro-3-pentylisocoumarin (12h). Method A
Compound 1034 was treated with 11h, Cu and KOBut in ButOH,
as for the synthesis of 12a (Method B) (chromatographic eluent:
hexane/EtOAc 10:1) to give 12h (4%) as a pale yellow oil: IR mmax
(film) 1736, 1646, 1530, 1344 cmÀ1 1H NMR (CDCl3) d 0.90–0.94
;
(3H, m, pentyl 5-H3), 1.35–1.40 (4H, m, pentyl 3,4-H4), 1.70–1.78
(2H, m, pentyl 2-H2), 2.59 (2H, t, J = 7.8 Hz, pentyl 1-H2), 7.12
(1H, d, J = 0.8 Hz, 4-H), 7.55 (1H, t, J = 7.8 Hz, 7-H), 8.41 (1H, dd,
J = 7.8, 1.6 Hz, 6-H), 8.56 (1H, ddd, J = 7.8, 1.6, 0.8 Hz, 8-H); 13C
NMR d 13.96, 22.37, 26.61, 31.18, 34.20, 97.69, 122.08, 126.83,
131.34, 131.85, 135.71, 143.82, 160.99, 162.36; MS (EI) m/z
261.1002 (M) (C14H15NO4 requires 261.1001).
6.1.6. 3-(4-Methoxyphenyl)-5-nitroisocoumarin (12d). Method
A
Compound 1034 was treated with 11d40, Cu and KOBut in
ButOH, as for the synthesis of 12a (Method B) (chromatographic
eluent: hexane/EtOAc 10:1) to give 12d (15%) as yellow crystals:
mp 241–242 °C (lit.26 mp 241–242 °C); 1H NMR (CDCl3) d 3.88
(3H, s, Me), 6.99 (2H, d, J = 9.0 Hz, Ph 3,5-H2), 7.54 (1H, t,
J = 8.2 Hz, 7-H), 7.76 (1H, s, 4-H), 7.88 (2H, d, J = 9.0 Hz, Ph
2,6-H2), 8.46 (1H, dd, J = 8.2, 1.2 Hz, 6-H), 8.59 (1H, dd, J = 8.2,
6.1.12. 5-Nitro-3-pentylisocoumarin (12h). Method B
Compound 1034 was treated with 17h,45 Cu and KOBut in
ButOH, as for the synthesis of 12b (Method B) to give 12h (36%)
as a pale yellow oil, with data as above.
1.2 Hz, 8-H); 13C NMR (CDCl3) (Cq omitted)
d 55.56 (Me),
94.74 (4-C), 114.52 (Ph 3,5-C2), 126.56 (7-C), 127.73 (Ph 2,6-C2),
131.71 (6-C), 135.92 (8-C); MS (EI) m/z 297.0639 (M) (C16H11NO5
requires 297.0637), 266 (MÀOMe). Further elution yielded 12g
(6%) as yellow crystals, with data as below.
6.1.13. 5-Nitro-3-phenylmethylisocoumarin (12i)
Compound 1034 was treated with 17i, as for the synthesis of
12b (Method B) (chromatographic eluent: hexane/EtOAc 9:1) to
give 12i (32%) as yellow crystals: mp 137–138 °C; IR mmax 1740,
6.1.7. 3-(4-Methoxyphenyl)-5-nitroisocoumarin (12d). Method
B
1647, 1564, 1346 cmÀ1 1H NMR (CDCl3) d 3.88 (2H, s CH2), 7.13
;
Compound 1034 was treated with 17d,43 Cu and KOBut in
ButOH, as for the synthesis of 12b (Method B) (chromatographic
eluent: hexane/EtOAc 4:1) to give 12d (61%) as yellow crystals,
with data as above.
(1H, d, J = 0.5 Hz, 4-H), 7.24–7.36 (5H, m, Ph-H5), 7.54 (1H, t,
J = 8.0 Hz, 7-H), 8.39 (1H, dd, J = 8.0, 1.4 Hz, 6-H), 8.53 (1H, ddd,
J = 8.0, 1.4, 0.5 Hz, 8-H); MS (EI) m/z 281.0690 (M) (C16H11NO4 re-
quires 281.0688), 190 (MÀBn).

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6.1.14. 3-Ethyl-5-nitroisocoumarin (12j)
mp 127–128 °C; IR mmax 3482, 1665, 1536, 1348 cmÀ1 1H NMR
;
Compound 1034 was treated with 17j, Cu and KOBut in ButOH,
as for the synthesis of 12b (Method B) (chromatographic eluent:
hexane/EtOAc 9:1) to give 12j (24%) as yellow crystals: mp 77–
((CD3)2SO) d 7.25 (1H, s, 4-H), 7.53–7.55 (3H, m, Ph 3,4,5-H3),
7.66 (1H, t, J = 7.8 Hz, 7-H), 7.78–7.80 (2H, m, Ph 2,6-H2), 8.49
(1H, d, J = 7.8 Hz, 6-H), 8.60 (1H, d, J = 7.8 Hz, 8-H), 12.11 (1H, br
s, NH); MS (EI) m/z 266.0694 (M) (C15H10N2O3 requires 266.0691).
78 °C; IR mmax 1747, 1645, 1524, 1347 cm-1 1H NMR (CDCl3) d
;
1.17 (3H, t, J = 7.6 Hz, Me), 2.55 (2H, q, J = 7.6 Hz, CH2), 7.01 (1H,
d, J = 0.9 Hz, 4-H), 7.48 (1H, t, J = 8.1 Hz, 7-H), 8.32 (1H, dd,
J = 8.1, 2.6 Hz, 6-H), 8.44 (1H, ddd, J = 8.1, 2.6, 0.9 Hz, 8-H); 13C
6.1.19. 3-(4-Methylphenyl)-5-nitroisoquinolin-1-one (21c)
Compound 12c was treated with NH3 in 2-methoxyethanol, as
for the synthesis of 21a, to give 21c (86%) as bright yellow crystals:
mp 175–176 °C; 1H NMR ((CD3)2SO) d 2.37 (3H, s, Me), 7.20 (1H, d,
J = 0.8 Hz, 4-H), 7.32 (2H, d, J = 8.2 Hz, Ph 3,5-H2), 7.62 (1H, t,
J = 8.2 Hz, 7-H), 7.66 (2H, d, J = 8.2 Hz, Ph 2,6-H2), 8.45 (1H, dd,
J = 8.2, 1.2 Hz, 6-H), 8.56 (1H, ddd, J = 8.2, 1.2, 0.8 Hz, 8-H), 12.03
(1H, br s, NH); MS (EI) m/z 280.0856 (M) (C16H12N2O3 requires
280.0848); Anal. Calcd for C16H12N2O3: C, 68.56; H, 4.32; N, 9.99.
Found: C, 68.2; H, 4.28; N, 10.0.
NMR
d 11.73, 27.99, 97.41, 122.65, 127.41, 131.89, 132.38,
136.22, 144.43, 161.43, 163.92; MS (EI) m/z 219.0533 (M)
(C11H9NO4 requires 219.0532).
6.1.15. 3-(2-Methylpropyl)-5-nitroisocoumarin (12k)
Compound 1034 treated with 17k, Cu and KOBut in ButOH, as for
the synthesis of 12b (Method B) (chromatographic eluent: hexane/
EtOAc 9:1) to give 12k (26%) as yellow crystals: mp 71–72 °C; IR
mmax 1737, 1645, 1531, 1346 cmÀ1 1H NMR d (CDCl3) 0.99 (6H, d,
;
J = 6.6 Hz, 2 Â Me), 2.16 (1H, m, CH2CH), 2.45 (2H, d, J = 7.4 Hz,
CH2), 7.09 (1H, s, 4-H), 7.55 (1H, t, J = 8.2 Hz, 7-H), 8.40 (1H, dd,
J = 8.2, 1.2 Hz, 6-H), 8.54 (1H, dd, J = 8.2, 1.2 Hz, 8-H); MS (EI) m/z
247.0848 (M) (C13H13NO4 requires 247.0845).
6.1.20. 3-(4-Methoxyphenyl)-5-nitroisoquinolin-1-one (21d)
Compound 12d was treated with NH3 in 2-methoxyethanol, as
for the synthesis of 21a, to give 21d (65%) as bright yellow crystals:
mp 236–237 °C; IR mmax 3468, 1677, 1515, 1323 cmÀ1 1H NMR
;
((CD3)2SO) d 3.82 (3H, s, Me), 7.07 (2H, d, J = 9.0 Hz, Ph 3,5-H2),
7.18 (1H, d, J = 0.8 Hz, 4-H), 7.60 (1H, t, J = 8.2 Hz, 7-H), 7.73 (2H,
d, J = 9.0 Hz, Ph 2,6-H2), 8.45 (1H, dd, J = 8.2, 1.2 Hz, 6-H), 8.55
(1H, ddd, J = 8.2, 1.2, 0.8 Hz, 8-H), 12.00 (1H, br s, NH); MS (EI)
m/z 296.0802 (M) (C16H12N2O4 requires 296.0797); Anal. Calcd
for C16H12N2O4Á0.5H2O: C, 62.95; H, 4.26; N, 9.18. Found: C, 63.2;
H, 4.12; N, 9.49.
6.1.16. 1,5-Diphenyl-2,4-pentanedione (17i) and ethyl
2,4-diphenyl-3-oxobutanoate (20)
1-Phenylpropan-2-one 18 (26.8 g, 0.20 mol) in dry Et2O (50 mL)
was added during 10 min to NaNH2 (50% in toluene, 31.2 ml,
0.40 mol) and dry Et2O (100 mL) and the mixture was stirred for
30 min. Ethyl phenylacetate 19 (65.6 g, 0.40 mol) in dry Et2O
(50 mL) was added dropwise. The mixture was boiled under reflux
for 2 h, poured into H2O (300 mL) and neutralised with aq HCl
(2 M). The solution was extracted with Et2O. The solvent was evap-
orated. The residue was dissolved in an equal volume of MeOH. To
this methanolic solution was added a hot solution of Cu(OAc)2
(40.0 g) in H2O (350 mL) and the mixture was allowed to stand un-
til it cooled to 20 °C. The precipitated copper salt was filtered,
washed with cold petroleum ether and shaken with a mixture of
aq H2SO4 (10%, 300 mL) and Et2O (100 mL) until the Et2O layer
was colourless. Evaporation and recrystallisation (hexane/EtOAc)
yielded 17i (26%) as orange crystals: mp 68–69 °C (lit.46 mp
65.5–66.5 °C); 1H NMR (CDCl3) d 3.56 (4H, s, 1,5-H4), 5.43 (1H, s,
3-H), 7.18–7.32 (10 H, m, 2 Â Ph-H5), 15.27 (1H, br s, OH); MS
(EI) m/z 252.1144 (M) (C17H16O2 requires 252.1150), 161
(MÀCH2Ph), 133 (MÀCOCH2Ph). Isolated from the methanolic
mother liquor was 20 (41%) as colourless crystals: mp 76–78 °C
6.1.21. 3-(4-Chlorophenyl)-5-nitroisoquinolin-1-one (21e)
Compound 12e was treated with NH3 in 2-methoxyethanol, as
for the synthesis of 21a, to give 21e (64%) as bright yellow crystals:
mp 231–233 °C (decomp.); 1H NMR ((CD3)2SO) d 7.22 (1H, d,
J = 0.8 Hz, 4-H), 7.59 (2H, d, J = 8.6 Hz, Me 3,5-H2), 7.65 (1H, t,
J = 8.2 Hz, 7-H), 7.79 (2H, d, J = 8.6 Hz, Ph 2,6-H2), 8.47 (1H, dd,
J = 8.2, 1.2 Hz, 6-H), 8.58 (1H, ddd, J = 8.2, 1.2, 0.8 Hz, 8-H), 12.13
(1H, br s, NH); (FAB) m/z 303.0360 (M+H) (C15H1037ClN2O3 requires
303.0350), 301.0377 (M+H) (C15H1035ClN2O3 requires 301.0380);
Anal. Calcd for C15H9ClN2O3Á0.25H2O: C, 59.02; H, 3.11; N, 9.18.
Found: C, 58.8; H, 3.11; N, 9.11.
6.1.22. 5-Nitro-3-(thiophen-2-yl)isoquinolin-1-one (21f)
Compound 12f was treated with NH3 in 2-methoxyethanol, as
for the synthesis of 21a, to give 21f (63%) as orange crystals: mp
(lit.47 mp 75 °C); IR mmax 1734, 1715 cmÀ1 1H NMR (CDCl3) d
;
1.22 (3H, t, J = 7.1 Hz, Me), 3.74 (2H, s, 4-H2), 4.17 (2H, q,
J = 7.1 Hz, CH2Me), 4.81 (1H, s, 2-H), 7.05–7.39 (10 H, m, 2 Â
Ph-H5); MS (EI) m/z 282.1255 (M) (C18H18O3 requires 282.1256).
225 °C (decomp.); IR mmax 3458, 1670, 1616, 1514, 1319 cmÀ1 1H
;
NMR ((CD3)2SO) d 7.21 (1H, dd, J = 5.1, 3.9 Hz, thiophene 4-H),
7.33 (1H, d, J = 0.8 Hz, 4-H), 7.60 (1H, t, J = 8.2 Hz, 7-H), 7.77 (1H,
dd, J = 5.1, 1.2 Hz, thiophene 5-H), 7.93 (1H, dd, J = 3.9, 1.2 Hz, thi-
ophene 3-H), 8.47 (1H, dd, J = 8.2, 1.2 Hz, 6-H), 8.54 (1H, ddd,
J = 8.2, 1.2, 0.8 Hz, 8-H), 12.13 (1H, br s, NH); 13C NMR d (some
Cq omitted) 95.84, 125.24, 126.48, 127.88, 128.63, 129.12,
130.12, 130.88, 133.29; MS (EI) m/z 272.0257 (M) (C13H8N2O3S re-
quires 272.0256); Anal. Calcd for C13H8N2O3SÁ0.25H2O: C, 56.42; H,
3.07; N, 10.13. Found: C, 56.7; H, 3.15; N, 10.0.
6.1.17. 5-Nitro-3-(4-trifluoromethylphenyl)isoquinolin-1-one
(21a)
Compound 12a (560 mg, 1.7 mmol) in MeO(CH2)2OH (50 mL)
was saturated with NH3 and boiled under reflux for 4 h. The solvent
and excess reagent were evaporated until 10 mL remained. The
concentrate was stored at 4 °C for 16 h. The crystals were collected
by filtration, washed (H2O, then EtOH) and recrystallised (MeOH) to
give 21a (150 mg, 27%) as yellow crystals: mp 230–231 °C; 1H NMR
((CD3)2SO) d 7.28 (1H, s, 4-H), 7.68 (1H, t, J = 7.8 Hz, 7-H), 7.88 (2H,
d, J = 8.2 Hz, Ph 3,5-H2), 7.97 (2H, d, J = 8.2 Hz, Ph 2,6-H2), 8.47 (1H,
dd, J = 7.8, 1.2 Hz, 6-H), 8.58 (1H, d, J = 7.8, 1.2 Hz, 8-H), 12.21 (1H,
br s, NH); 19F NMR ((CD3)2SO) d À61.84 (s, CF3); MS (EI) m/z
334.0560 (M) (C16H9F3N2O3 requires 334.0565).
6.1.23. 3-Methyl-5-nitroisoquinolin-1-one (21g)
Compound 12g was treated with NH3 in 2-methoxyethanol, as
for the synthesis of 21a, to give 21g (68%) as bright yellow crystals:
mp 231–232 °C (lit.23 mp 231–232 °C); IR mmax 3435, 1668, 1523,
1346 cmÀ1 1H NMR ((CD3)2SO) d 2.29 (3H, s, Me), 6.78 (1H, br s,
;
4-H), 7.55 (1H, t, J = 7.8 Hz, 7-H), 8.38 (1H, dd, J = 7.8, 1.2 Hz,
6-H), 8.49 (1H, ddd, J = 7.8, 1.2 Hz, 8-H), 11.79 (1H, br s, NH); MS
(FAB) m/z 205.0617 (M+H) (C10H9N2O3 requires 205.0613), 189
(MÀMe); Anal. Calcd for C10H8N2O3: C, 58.82; H, 3.95; N, 13.72.
Found: C, 58.4; H, 3.99; N, 13.5.
6.1.18. 5-Nitro-3-phenylisoquinolin-1-one (21b)
Compound 12b was treated with NH3 in 2-methoxyethanol, as
for the synthesis of 21a, to give 21b (73%) as bright yellow crystals:

E. C. Y. Woon et al. / Bioorg. Med. Chem. 21 (2013) 5218–5227
5225
6.1.24. 5-Nitro-3-pentylisoquinolin-1-one (21h)
127.41 (7-C + Ph 2,6-C2), 129.20 (q, J = 31.8 Hz, Ph 4-C), 136.82
Compound 12h was treated with NH3 in 2-methoxyethanol, as
for the synthesis of 21a, to give 21h (29%) as bright yellow crystals:
(Ph 1-C), 137.83 (3-C), 139.92 (5-C), 162.46 (1-C); 19F NMR
((CD3)2SO)
d
-61.02 (s, CF3); MS m/z (ES) 303.0756 (MÀH)
mp 158–159 °C; IR mmax 3467, 1666, 1524, 1375 cmÀ1
;
1H NMR
(C16H10F3N2O requires 303.0745).
((CD3)2SO) d 0.86–0.89 (3H, m, pentyl 5-H3), 1.28–1.34 (4H, m,
pentyl 3,4-H4), 1.60–1.67 (2H, m, pentyl 2-H2), 2.55 (2H, t,
J = 7.6 Hz, pentyl 1-H2), 6.79 (1H, s, 4-H), 7.56 (1H, t, J = 7.8 Hz,
7-H), 8.39 (1H, dd, J = 7.8, 1.2 Hz, 6-H), 8.50 (1H, dd, J = 7.8,
1.2 Hz, 8-H), 11.77 (1H, br s, NH); MS (EI) m/z 260.1162 (M)
(C14H16N2O3 requires 260.1161).
6.1.29. 5-Amino-3-(4-trifluoromethylphenyl)isoquinolin-1-one
hydrochloride (22a). Method B
Compound 21a (140 mg, 0.42 mmol) and Pd/C (10%, 70 mg) in
EtOH (15 mL) and aq HCl (34%, 0.4 mL) were stirred vigorously un-
der H2 for 2 h. The suspension was filtered through Celite. The Cel-
ite pad and residue were suspended in water (100 mL) and heated.
The hot suspension was filtered through a second Celite pad. Evap-
oration of the solvent and drying gave 21a (60 mg, 42%), with data
as above.
6.1.25. 5-Nitro-3-phenylmethylisoquinolin-1-one (21i)
Compound 12i was treated with NH3 in 2-methoxyethanol, as
for the synthesis of 21a, to give 21i (83%) as bright yellow crystals:
mp 203–204 °C (decomp.); IR mmax 3186, 1645, 1524, 1323 cmÀ1
;
1H NMR ((CD3)2SO) d 3.92 (2H, s CH2), 6.80 (1H, s, 4-H), 7.24–
7.34 (5H, m, Ph-H5), 7.57 (1H, t, J = 7.8 Hz, 7-H), 8.39 (1H, d,
J = 7.8 Hz, 6-H), 8.49 (1H, d, J = 7.8 Hz, 8-H), 11.93 (1H, br s, NH);
MS (EI) m/z 280.0848 (M) (C16H12N2O3 requires 280.0848).
6.1.30. 5-Amino-3-phenylisoquinolin-1-one (22b)
Compound 21b was treated with SnCl2 in EtOH, as for the syn-
thesis of 22a (Method A), to give 22b (57%) as yellow crystals: mp
215–217 °C; IR m
max 3569, 3329, 3230, 1655 cmÀ1; 1H NMR (CDCl3)
d 4.00 (2H, br s, NH2), 6.64 (1H, s, 4-H), 6.93 (1H, dd, J = 7.8, 1.2 Hz,
6-H), 7.22 (1H, t, J = 7.8 Hz, 7-H), 7.36–7.45 (3H, m, Ph 3,4,5-H3),
7.64-7.66 (2H, m, Ph 2,6-H2), 7.80 (1H, dd, J = 7.8, 1.2 Hz, 8-H),
10.08 (1H, br s, NH); MS m/z (FAB) 237.1019 (M+H) (C15H13N2O re-
quires 237.1028). Compound 22b (50 mg, 0.2 mmol) was stirred
with aq HCl (2 M, 20 mL) for 30 min. Evaporation and recrystallisa-
tion (MeOH) yielded 22bÁHCl salt (53 mg, 91%) as a pale buff solid:
mp 192–193 °C; 1H NMR (D2O) d 6.98 (1H, s, 4-H), 7.52–7.59 (3H,
m, Ph 3,4,5-H3), 7.59 (1H, t, J = 8.1 Hz, 7-H), 7.68–7.75 (2H, m, Ph
2,6-H2), 7.84 (1H, d, J = 8.1 Hz, 6-H), 8.31 (1H, d, J = 8.1 Hz, 8-H).
A small sample of 22b was also converted into 22bÁHBr salt: pale
buff solid; mp 274–275 °C; IR mmax 3425, 2923, 1629; 1H NMR
(CD3OD) d 7.10 (1H, s, 4-H), 7.28 (1H, d, J = 7.7 Hz, 6-H), 7.38 (1H,
t, J = 7.8 Hz, 7-H), 7.55 (3H, m, Ph 3,4,5-H3), 7.80 (1H, d,
J = 7.6 Hz, 8-H), 7.87 (2H, m, Ph 2,6-H2), 11.55 (1H, s, N–H); 13C
NMR (CD3OD) (HSQC/HMBC) d 98.36 (4-C), 127.45 (4a-C), 127.67
(7-C), 128.13 (Ph 2,6-C2), 128.96 (8-C), 129.46 (6-C), 130.32 (Ph
3,4,5-C3), 131.34 (Ph 4-C), 134.00 (8a-C), 135.28 (Ph 1-C), 144.34
(5-C), 164.63 (1-C).
6.1.26. 3-Ethyl-5-nitroisoquinolin-1-one (21j)
Compound 12j was treated with NH3 in 2-methoxyethanol, as
for the synthesis of 21a, to give 21j (38%) as bright yellow crystals:
mp 196–197 °C; IR mmax 3432, 1666, 1524, 1372 cmÀ1 1H NMR
;
((CD3)2SO) d 1.22 (3H, t, J = 7.5 Hz, Me), 2.59 (2H, q, J = 7.5 Hz,
CH2), 6.80 (1H, s, 4-H), 7.56 (1H, t, J = 8.1 Hz, 7-H), 8.40 (1H, dd,
J = 8.1, 1.5 Hz, 6-H), 8.51 (1H, dd, J = 8.1, 1.5 Hz, 8-H), 11.79 (1H,
br s, NH); MS (FAB) m/z 219.0779 (M+H) (C11H11N2O3 requires
219.0770).
6.1.27. 5-Nitro-3-(2-methylpropyl)isoquinolin-1-one (21k)
Compound 12k was treated with NH3 in 2-methoxyethanol, as
for the synthesis of 21a, to give 21k (89%) as bright yellow crystals:
mp 184–185 °C; IR mmax 3436, 1655, 1523, 1376 cmÀ1 1H NMR
;
((CD3)2SO) d 0.91 (6H, d, J = 6.6 Hz, 2 Â Me), 1.97–2.04 (1H, m,
CH2CH), 2.43 (2H, d, J = 7.0 Hz, CH2), 6.77 (1H, s, 4-H), 7.56 (1H, t,
J = 7.8 Hz, 7-H), 8.40 (1H, dd, J = 7.8, 1.2 Hz, 6-H), 8.50 (1H, dd,
J = 7.8, 1.2 Hz, 8-H), 11.76 (1H, br s, NH); MS (EI) m/z 246.1003
(M) (C13H14N2O3 requires 246.1004).
6.1.31. 5-Amino-3-(4-methylphenyl)isoquinolin-1-one (22c).
Method A
6.1.28. 5-Amino-3-(4-trifluoromethylphenyl)isoquinolin-1-one
(22a). Method A
Compound 21c was treated with SnCl2 in EtOH, as for the syn-
thesis of 22a (Method A), to give 22c (92%) as pale yellow crystals:
Compound 21a (1.0 g, 3.0 mmol) was heated at 70 °C with SnCl2
(1.8 g, 9.5 mmol) in EtOH (50 mL) for 4 h, then poured into ice-H2O
(200 mL). The suspension was made alkaline with aq NaOH and fil-
tered. Extraction of the filtrate (EtOAc), evaporation and recrystal-
lisation (hexane/EtOAc) gave 22a (360 mg, 40%) as yellow crystals:
mp 213–214 °C; IR m
max 3476, 3253, 1669 cmÀ1; 1H NMR (CDCl3) d
2.41 (3H, s, Me), 4.06 (2H, br, NH2), 6.68 (1H, s, 4-H), 6.99 (1H, d,
J = 7.8 Hz, 6-H), 7.28 (1H, t, J = 7.8 Hz, 7-H), 7.29 (2H, d, J = 7.8 Hz,
Ph 3,5-H2), 7.59 (2H, d, J = 7.8 Hz, Ph 2,6-H2), 7.86 (1H, d,
J = 7.8 Hz, 8-H), 9.92 (1H, br, NH); MS m/z (FAB) 251.1181 (M+H)
(C16H15N2O requires 251.1184). A sample was converted into
22cÁHCl salt: pale buff solid; mp >350 °C; 1H NMR ((CD3)2SO) d
2.23 (3H, s, Me), 6.48 (1H, s, 4-H), 7.31 (2H, d, J = 7.8 Hz, Ph 3,5-
H2), 7.36 (1H, t, J = 7.8 Hz, 7-H), 7.61 (1H, d, J = 7.8 Hz, 6-H), 7.75
(1H, d, J = 7.8 Hz, 8-H), 7.96 (2H, d, J = 7.8 Hz, Ph 2,6-H2), 11.47
(1H, br, NH).
mp 214–215 °C; IR mmax 3419, 3218, 1651 cmÀ1
;
1H NMR
((CD3)2SO) d 5.86 (2H, br s, NH2), 6.88 (1H, dd, J = 7.8, 1.2 Hz,
6-H), 7.18 (1H, t, J = 7.8 Hz, 7-H), 7.22 (1H, s, 4-H), 7.40 (1H, d,
J = 7.8, 1.2 Hz, 8-H), 7.82 (2H, d, J = 8.2 Hz, Ph 3,5-H2), 8.02 (2H, d,
J = 8.2 Hz, 2,6-H2), 11.45 (1H, br s, NH); 19F NMR ((CD3)2SO) dF
À61.60 (s, CF3); MS (FAB) m/z 305.0898 (M+H) (C16H12F3N2O re-
quires 305.0902). A sample was converted into 22aÁHCl salt: pale
buff solid; mp > 350 °C; 1H NMR ((CD3)2SO) d 7.14 (1H, dd,
J = 7.8, 1.2 Hz, 6-H), 7.18 (1H, s, 4-H), 7.31 (1H, t, J = 7.8 Hz, 7-H),
7.63 (1H, dd, J = 7.8, 1.2 Hz, 8-H), 7.85 (2H, d, J = 8.2 Hz, Ph 3,5-
H2), 8.01 (2H, d, J = 8.2 Hz, 2,6-H2), 11.60 (1H, br s, NH); 19F NMR
((CD3)2SO) d À59.50 (s, CF3). A small sample of 22a was also con-
verted into 22aÁHBr salt: buff solid; mp >360 °C; IR mmax 3414,
3165, 1647, 1327, 1170, 1116; 1H NMR ((CD3)2SO) d 7.17 (2H, m,
4,6-H2), 7.32 (1H, t, J = 7.5 Hz, 7-H), 7.67 (1H, d, J = 7.5 Hz, 8-H),
7.88 (2H, d, J = 8.0 Hz, Ph 3,5-H2), 8.04 (2H, d, J = 8.0 Hz, Ph 2,6-
H2), 11.63 (1H, br, NH); 13C NMR ((CD3)2SO) (HSQC/HMBC) d
99.53 (4-C), 117.08 (8-C), 118.87 (6-C), 123.51 (8a-C), 124.11 (q,
J = 270.6 Hz, CF3), 125.64 (q, J = 3.5 Hz, Ph 3,5-C2), 126.28 (4a-C),
6.1.32. 5-Amino-3-(4-methylphenyl)isoquinolin-1-one
hydrochloride (22c). Method B
Compound 21c was treated with H2 and Pd/C in EtOH and aq
HCl, as for the synthesis of 22a (Method B), to give 22c (79%) as
a pale buff solid, with data as above.
6.1.33. 5-Amino-3-(4-methoxyphenyl)isoquinolin-1-one (22d)
Compound 21d (80 mg, 0.3 mmol) was treated with SnCl2 in
EtOH, as for the synthesis of 22a (Method A), to give 22d (83%)
as yellow crystals: mp 189–190 °C; IR mmax 3438, 3233,
1660 cmÀ1 1H NMR (CDCl3) d 3.86 (3H, s, Me), 4.11 (2H, br,
;

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E. C. Y. Woon et al. / Bioorg. Med. Chem. 21 (2013) 5218–5227
NH2), 6.64 (1H, s, 4-H), 6.97 (1H, dd, J = 7.8, 1.2 Hz, 6-H), 6.99 (2H,
d, J = 8.8 Hz, Ph 3,5-H2), 7.25 (1H, t, J = 7.8 Hz, 7-H), 7.66 (2H, d,
J = 8.8 Hz, Ph 2,6-H2), 7.85 (1H, dd, J = 7.8, 1.2 Hz, 8-H), 10.45
(1H, br s, NH); MS (FAB) m/z 267.1132 (M+H) (C16H15N2O2 requires
267.1134). A sample was converted into 22dÁHCl salt: buff solid;
mp >350 °C; 1H NMR (D2O) d 3.86 (3H, s, OMe), 6.84 (2H, d,
J = 8.1 Hz, Ph 3,5-H2), 6.92 (1H, s, 4-H), 7.11 (1H, t, J = 8.1 Hz,
7-H), 7.55 (1H, d, J = 8.1 Hz, 6-H), 7.70 (1H, d, J = 8.1 Hz, 8-H),
7.94 (2H, J = 8.1 Hz, Ph 2,6-H2).
mp 75–76 °C; IR mmax 3448, 3395, 3166, 1651 cmÀ1 1H NMR d
;
0.76–0.88 (3H, m, pentyl 5-H3), 1.21–1.34 (4H, m, pentyl 3,4-H4),
1.66–1.78 (2H, m, pentyl 2-H2), 2.57 (2H, t, J = 7.6 Hz, pentyl
1-H2), 3.94 (2H, br s, NH2), 6.21 (1H, s, 4-H), 6.92 (1H, dd, J = 7.7,
1.2 Hz, 6-H), 7.20 (1H, t, J = 7.7 Hz, 7-H), 7.84 (1H, dd, J = 7.7,
1.2 Hz, 8-H), 11.75 (1H, br s, NH); MS (EI) m/z 230.1418 (M)
(C14H18N2O requires 230.1419). A sample was converted into
22hÁHCl salt: buff solid; mp 129–130 °C; 1H NMR (D2O) d 0.74–
0.82 (3H, m, pentyl 5-H3), 1.19–1.29 (4H, m, pentyl 3,4-H4),
1.55–1.66 (2H, m, pentyl 2-H2), 2.55 (2H, t, J = 7.6 Hz, pentyl
1-H2), 6.53 (1H, s, 4-H), 7.49 (1H, t, J = 7.8 Hz, 7-H), 7.74 (1H, d,
J = 7.8 Hz, 6-H), 8.20 (1H, d, J = 7.8 Hz, 8-H).
6.1.34. 5-Amino-3-(4-chlorophenyl)isoquinolin-1-one (22e)
Compound 21e was treated with SnCl2 in EtOH, as for the syn-
thesis of 22a (Method A), to give 22e (41%) as yellow crystals: mp
231–232 °C; IR mmax 3548, 3338, 3236, 1654 cmÀ1
;
1H NMR
6.1.38. 5-Amino-3-phenylmethylisoquinolin-1-one (22i)
Compound 21i was treated with SnCl2 in EtOH, as for the syn-
thesis of 22a (Method A), to give 22i (64%) as yellow crystals:
((CD3)2SO) d 5.81 (2H, br, NH2), 6.86 (1H, dd, J = 7.8, 1.2 Hz, 6-H),
7.11 (1H, s, 4-H), 7.15 (1H, t, J = 7.8 Hz, 7-H), 7.38 (1H, dd, J = 7.8,
1.2 Hz, 8-H), 7.53 (2H, d, J = 6.6 Hz, Ph 3,5-H2), 7.83 (2H, d,
J = 6.6 Hz, Ph 2,6-H2), 11.34 (1H, br s, NH); MS (FAB) m/z
273.0618 (M+H) (C15H1237ClN2O requires 273.0609), 271.0629
(M+H) (C15H1235ClN2O requires 271.0638). A sample was con-
verted into 22eÁHCl salt: buff solid; mp >350 °C; 1H NMR
((CD3)2SO) d 7.08 (1H, s, 4-H), 7.14 (1H, dd, J = 7.8, 1.2 Hz, 6-H),
7.28 (1H, t, J = 7.8 Hz, 7-H), 7.56 (2H, d, J = 9.0 Hz, Ph 3,5-H2),
7.64 (1H, dd, J = 7.8, 1.2 Hz, 8-H), 7.83 (2H, d, J = 9.0 Hz, Ph 2,6-
H2), 11.50 (1H, br s, NH); 13C NMR ((CD3)2SO) (HSQC/HMBC) d
98.36 (4-C), 119.82 (8-C), 120.94 (6-H), 125.98 (8a-C), 126.92 (7-
C), 127.68 (4a-C), 128.36 (Ph 2,6-C2), 128.75 (Ph 3,5-C2), 132.77
(Ph 1-C), 133.93 (Ph 4-C), 136.71 (5-C), 138.30 (3-C), 160.61 (1-C).
mp 85–86 °C; IR mmax 3469, 3394, 3162, 1661 cmÀ1 1H NMR
;
(CDCl3) d 3.91 (2H, s CH2), 4.00 (2H, br s, NH2), 6.72 (1H, d,
J = 8.1 Hz, 6-H), 6.86 (1H, s, 4-H), 6.91 (1H, t, J = 8.1 Hz, 7-H),
7.17–7.43 (5H, m, Ph-H5), 7.83 (1H, d, J = 8.1 Hz, 8-H), 10.94 (1H,
br s, NH); MS (EI) m/z 250.1100 (M) (C16H14N2O requires
250.1106). A sample was converted into 22iÁHCl salt: buff solid;
mp > 350 °C; 1H NMR (D2O) d 3.94 (2H, s CH2), 6.49 (1H, s, 4-H),
7.25–7.37 (5H, m, Ph-H5), 7.51 (1H, t, J = 7.8 Hz, 7-H), 7.73 (1H, d,
J = 7.8 Hz, 6-H), 8.23 (1H, d, J = 7.8 Hz, 8-H).
6.1.39. 5-Amino-3-ethylisoquinolin-1-one (22j)
Compound 21j was treated with SnCl2 in EtOH, as for the syn-
thesis of 22a (Method A), to give 22j (24%) as pale yellow crystals:
6.1.35. 5-Amino-3-(thiophen-2-yl)isoquinolin-1-one (22f)
Compound 21f was treated with SnCl2 in EtOH, as for the syn-
thesis of 22a (Method A), to give 22b (66%) as yellow crystals:
mp 162–163 °C; IR mmax 3447, 3395, 3164, 1646 cmÀ1 1H NMR
;
((CD3)2SO) d 1.21 (3H, t, J = 7.5 Hz, Me), 2.47 (2H, q, J = 7.4 Hz,
CH2), 5.51 (2H, br s, NH2), 6.44 (1H, d, J = 0.8 Hz, 4-H), 6.80 (1H,
dd, J = 7.8, 1.2 Hz, 6-H), 7.05 (1H, t, J = 7.8 Hz, 7-H), 7.33 (1H, ddd,
J = 7.8, 1.2, 0.8 Hz, 8-H), 11.04 (1H, br s, NH); MS (FAB) m/z
189.1026 (M+H) (C11H13N2O requires 189.1028). Anal. Calcd for
(C11H12N2O.0.25 H2O) C, 68.57; H, 6.49; N, 14.55; Found: C, 68.9;
H, 6.45; N, 14.3. A sample was converted into 22jÁHCl salt: buff so-
lid; mp 133–134 °C; 1H NMR ((CD3)2SO) d 1.22 (3H, t, J = 7.4 Hz,
Me), 2.53 (2H, q, J = 7.4 Hz, CH2), 6.44 (1H, s, 4-H), 7.34 (1H, t,
J = 7.8 Hz, 7-H), 7.47 (1H, dd, J = 7.8, 1.2 Hz, 6-H), 7.91 (1H, dd,
J = 7.8, 1.2 Hz, 8-H), 11.41 (1H, br s, NH).
mp 229–230 °C; IR mmax 3470, 3365, 1659 cmÀ1 1H NMR (CDCl3)
;
d 4.03 (2H, br s, NH2), 6.70 (1H, s, 4-H), 6.99 (1H, dd, J = 7.8,
1.1 Hz, 6-H), 7.14 (1H, dd, J = 4.9, 3.8 Hz, thiophene 4-H), 7.28
(1H, t, J = 7.8 Hz, 7-H), 7.37 (1H, dd, J = 4.9, 1.1 Hz, thiophene
5-H), 7.49 (1H, dd, J = 3.8, 1.1 Hz, thiophene 3-H), 7.86 (1H, dd,
J = 7.8, 1.1 Hz, 8-H), 9.50 (1H, br s, NH); MS (EI) m/z 242.0517
(M) (C13H10N2OS requires 242.0514). A sample was converted into
22fÁHCl salt: buff solid: mp >350 °C; 1H NMR (D2O) d 6.87 (1H, s,
4-H), 7.07 (1H, dd, J = 4.9, 3.8 Hz, thiophene 4-H), 7.26 (1H, d,
J = 4.9 Hz, thiophene 5-H), 7.53 (1H, d, J = 3.8 Hz, thiophene 3-H),
7.58 (1H, t, J = 7.8 Hz, 7-H), 7.77 (1H, d, J = 7.8 Hz, 6-H), 8.22 (1H,
d, J = 7.8 Hz, 8-H).
6.1.40. 5-Amino-3-(2-methylpropyl)isoquinolin-1-one (22k)
Compound 21k was treated with SnCl2 in EtOH, as for the syn-
thesis of 22a (Method A), to give 22k (83%) as yellow crystals: mp
6.1.36. 5-Amino-3-methylisoquinolin-1-one (22g)
Compound 21g was treated with SnCl2 in EtOH, as for the syn-
thesis of 22a (Method A), to give 22g (59%) as pale yellow crystals:
mp 183–184 °C (lit.23 mp 183–184 °C); IR mmax 3467, 3375, 3298,
113–114 °C; IR m
max 3468, 3396, 3165, 1645 cmÀ1; 1H NMR (CDCl3)
d 0.82 (6H, d, J = 6.4 Hz, 2 Â Me), 1.90–2.02 (1H, m, CH2CH), 2.32
(2H, d, J = 7.4 Hz, CH2), 3.99 (2H, br, NH2), 6.14 (1H, s, 4-H), 6.84
(1H, dd, J = 7.9, 1.2 Hz, 6-H), 7.10 (1H, t, J = 7.9 Hz, 7-H), 7.71 (1H,
dd, J = 7.9, 1.2 Hz, 8-H), 11.52 (1H, br s, NH); MS (EI) m/z
216.1263 (M) (C13H16N2O requires 216.1263). A sample was con-
verted into 22kÁHCl salt: buff crystals; mp 151–152 °C; 1H NMR
(D2O) d 0.88 (6H, d, J = 6.6 Hz, 2 Â Me), 1.89–1.93 (1H, m, CH2CH),
2.47 (2H, d, J = 7.4 Hz, CH2), 6.52 (1H, s, 4-H), 7.50 (1H, t, J = 7.9 Hz,
7-H), 7.76 (1H, d, J = 7.9 Hz, 6-H), 8.22 (1H, d, J = 7.9 Hz, 8-H).
1655 cmÀ1 1H NMR ((CD3)2SO) d 2.18 (3H, s, Me), 5.47 (2H, br,
;
NH2), 6.44 (1H, s, 4-H), 6.80 (1H, dd, J = 7.8, 1.2 Hz, 6-H), 7.05
(1H, t, J = 7.8 Hz, 7-H), 7.32 (1H, dd, J = 7.8, 1.2 Hz, 8-H), 11.06
(1H, br s, NH); MS m/z (FAB) 175.0874 (M+H) (C10H11N2O requires
175.0871), 159 (MÀMe). A sample was converted into 22gÁHCl
salt: pale buff solid: mp >350 °C; IR mmax 3414, 2851, 1685 cmÀ1
;
1H NMR ((CD3)2SO) (COSY/NOESY) d 2.23 (3H, s, Me), 6.48 (1H, s,
4-H), 7.37 (1H, t, J = 7.8 Hz, 7-H), 7.69 (1H, d, J = 7.8 Hz, 6-H),
7.99 (1H, d, J = 7.8 Hz, 8-H), 11.50 (1H, br s, NH); 13C NMR
((CD3)2SO) (HMQC, HMBC) d 19.21 (Me), 97.20 (4-C), 125.25 (8-
C), 125.51 (6-C), 125.7 (8a-C), 126.2 (7-C), 130.3 (4a-C), 138.79
(3-C), 140.0 (5-C), 161.99 (1-C); Anal. Calcd for C10H11ClN2O: C,
57.02; H, 5.26; N, 13.30. Found: C, 56.82; H, 5.01; N, 13.45.
Acknowledgements
This work was supported by the Association for International
Cancer Research, KuDOS Pharmaceuticals and the University of
Bath. We are grateful to Dr. Niall M. B. Martin and Dr. Krystyna
Dillon (KuDOS) for help with the PARP assays and to Dr. Timothy
J. Woodman for some of the NMR spectra. MDT, AST and MDL
are members of the Cancer Research @ Bath (CR@B) network.
6.1.37. 5-Amino-3-pentylisoquinolin-1-one (22h)
Compound 21h was treated with SnCl2 in EtOH, as for the
synthesis of 22a (Method A), to give 22h (67%) as yellow crystals:

E. C. Y. Woon et al. / Bioorg. Med. Chem. 21 (2013) 5218–5227
5227
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Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.biortech.2012.
11.108.
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