Synthesis and preliminary pharmacological evaluation of 4′-arylalkyl analogues of clozapine. IV. the effects of aromaticity and isosteric replacement

Article abstract of DOI:10.1071/CH08307

We report the synthesis and preliminary pharmacological activity of a new series of tricyclic analogues of clozapine as potential antipsychotic agents for the treatment of schizophrenia. These compounds were designed based on a revised structural model, a

Full text of DOI:10.1071/CH08307

Full Paper
CSIRO PUBLISHING
Aust. J. Chem. 2008, 61, 930–940
www.publish.csiro.au/journals/ajc
Synthesis and Preliminary Pharmacological Evaluation
of 4ꢀ-Arylalkyl Analogues of Clozapine. IV.∗ The Effects
of Aromaticity and Isosteric Replacement
Ben Capuano,A,B Ian T. Crosby,A Edward J. Lloyd,A Anna Podloucka,A
and David A. TaylorA
AMedicinal Chemistry and Drug Action, Monash Institute of Pharmaceutical Sciences,
Monash University (Parkville Campus), 381 Royal Parade, Parkville, Vic. 3052, Australia.
BCorresponding author. Email: ben.capuano@pharm.monash.edu.au
We report the synthesis and preliminary pharmacological activity of a new series of tricyclic analogues of clozapine as
potential antipsychotic agents for the treatment of schizophrenia. These compounds were designed based on a revised
structural model, and investigate the length and nature of a designated linker (alkyl and alkyloxy) and the nature of
the introduced aryl group (aromatic and heteroaromatic). The chemistry and structural characterization of this series
of 4ꢀ-arylalkyl(oxy) analogues of clozapine are described. Preliminary results on the pharmacological effects of the
selected linkers and introduced aryl groups on affinity for dopamine D4 and serotonin 5-HT2A receptors are discussed.
Psychosis-related animal behavioural data for promising compounds identified from the receptor binding screen are also
presented.
Manuscript received: 18 July 2008.
Final version: 30 September 2008.
Introduction
ring at the N4ꢀ position of clozapine. Preliminary pharmaco-
logical evaluations include in vitro receptor binding assays to
ascertain their affinity for dopamine D4 and serotonin 5-HT2A
receptors, with particular reference to the effects of isosteric
replacement of CH2 for O in the linker and CH for N in the aryl
system. The clozapine analogues were also evaluated for their
potential to antagonize apomorphine-induced climbing in mice,
a psychosis-related behavioural model predictive of mesolim-
bic dopaminergic activity and therefore potential antipsychotic
activity.
To develop a new structural model for antipsychotic activity,
the chemical structures of some current therapeutic antipsy-
chotics were analyzed initially (Fig. 1), namely haloperidol 1,
clozapine 2, risperidone 3, and olanzapine 4. Depicted in bold
is the halogenated ring of haloperidol 1, the nitrogen atom that
is ionized at physiological pH and a distant aromatic moiety.
Clozapine 2 also displays a halogenated aromatic ring and a
nitrogen atom that is ionized at physiological pH, but lacks an
aryl-containing moiety attached to the ionizable or distal nitro-
gen atom. Risperidone displays similar structural characteristics
to haloperidol, exhibiting a halogenated aromatic ring, a nitrogen
atom that is ionized at physiological pH and a distant conjugated
π-system. Olanzapine shows structural similarities to clozapine,
differing only in the absence of a halogen substituent, and con-
tains a substituted thiophene ring in place of clozapine’s benzene
ring.
Schizophrenia is a debilitating mental illness that severely dis-
torts a patient’s perception of reality, and significantly impairs
various emotional, behavioural, and cognitive functions. This
most common form of psychosis boasts a devastating and
overwhelming worldwide incidence of ∼1%.[1] Clozapine 2
is heralded as the prototypical atypical antipsychotic and is
uniquely superior in efficacy against refractory schizophrenia.
Clozapine effectively treats both the positive (delusions, hal-
lucinations, and disorganized behaviour) and negative (social
and emotional withdrawal, affective flattening) symptoms of
schizophrenia, in addition to associated neurocognitive deficits,
and is virtually free of movement-related side-effects.[2] The
adverse effects profile, however, requires improvement owing
to clozapine’s propensity to induce a potentially fatal blood
disorder.[3,4]
Previous analogues of clozapine were designed by the struc-
tural hybridization of haloperidol (1) and clozapine 2.[5,6]
The preliminary pharmacological investigation of the previous
chain-extended series of clozapine analogues[6] revealed that the
optimal length of the hydrocarbon linker between N4ꢀ and the
introduced aryl system (phenyl) was three to five atoms. This
observation afforded valuable insight into the spatial require-
ments in the region of clozapine’s distal nitrogen atom and
provided the impetus for the ensuing study. The series of ana-
logues described herein investigates the pharmacological effects
of introducing an alkyl and alkyloxy linker of three to four
atoms in length, attached to a distal aromatic and heteroaromatic
The X-ray crystal structures of the aforementioned anti-
psychotic agents were superimposed (Fig. 2) using the six ring
∗ Part III, Aust. J. Chem. 2007, 60, 928.
© CSIRO 2008
10.1071/CH08307
0004-9425/08/120930

Analogues of Clozapine. IV
931
atoms of a piperazine or piperidine ring in the chair form as the
reference point, while maintaining a common location for the
nitrogen atom that is ionized at physiological pH. The structural
model depicted in Fig. 3 conceptualizes the superimposition,
highlighting a collection of key structural features. The envis-
aged assembly of a halogenated aromatic ring (monocyclic or
polycyclic nucleus), a nitrogen atom that is ionized at physio-
logical pH and a secondary aromatic or π-system separated by an
aliphatic linker of designated length and nature from the nitrogen
atom may provide comparatively potent and superior antipsy-
chotic activity. Based on consideration of the superimposition of
crystal structures and the development of the structural model,
weembarkedonaninvestigationofthesynthesis, structuralchar-
acterization and biochemical effects of a series of compounds
related to the structural template shown in Fig. 4. The target
compounds contain the tricyclic nucleus of clozapine connected
to a piperazine ring system, from which a series of chain-
extended fragments are anchored. Substitution of arylalkyl and
arylalkoxy substituents at the N4ꢀ position were designed to gen-
erate compounds with an ‘extended’ appearance similar to that
of haloperidol and risperidone, with the view of encapsulating
biochemical attributes of these commercial therapeutics within
the novel series described herein.
Chemistry
All of the target amidines (5a–g) were synthesized using one of
three synthetic pathways, namely: (a) Lewis acid-mediated con-
densation of a tricyclic lactam 24 and a monosubstituted piper-
azine for compounds 5a–d; (b) activation of the tricyclic lactam
to the corresponding imino chloride followed by treatment with
a monosubstituted piperazine for compounds 5e–f; and (c) a
reductive amination of desmethylclozapine 27 and a suitable
phenylalkanal for compound 5g. 4-(4-Pyridinyl)but-3-yn-1-ol
H
N
OH
O
Cl
N
Cl
N
N
F
Haloperidol, 1
Clozapine, 2
N
F
H3C
H
N
H
N
S
H3C
O
N
Cl
CH3
N
N
N
N
N
N
4ꢁ
N
Risperidone, 3
Olanzapine, 4
5
N
N
O
(
A
)n
A ꢂ O or CH2
X,Y,Z ꢂ CH or N
n ꢂ 2 or 3
H3C
X
Fig. 1. The chemical structures of clinically prescribed drugs to treat
schizophrenia (clozapine, 1; haloperidol, 2; risperidone, 3; and olanzap-
ine, 4) indicating important structural features coloured in bold, used in the
development of a general structural model.
Y
Z
Fig. 4. New structural template selected for investigation.
Ionizable N at physiological pH
Fig. 2. Superimposition of the X-ray crystal structures of currently prescribed antipsychotics: haloperidol (1, red), clozapine (2,
dark blue), risperidone (3, green), and olanzapine (4, light blue). Hydrogen atoms have been omitted for clarity. (The X-ray crystal
structures were sourced from the Cambridge Structural Database; molecular modelling was performed on a Silicon Graphics Iris Indy
workstation using the commercial software package Insight II.)
Aromatic motif
X
N
ꢀ-system
Aliphatic spacer
Fig. 3. Structural model detailing generic structural features that may afford potent antipsychotic activity
based on the superimposition of known antipsychotic agents (X = C or N).

932
B. Capuano et al.
9 and 4-(5-pyrimidinyl)but-3-yn-1-ol 10 were prepared accord-
ing to Scheme 1. The first step of the syntheses used a
Sonogashira coupling of but-3-yn-1-ol 8 with commercially
available 4-bromopyridine hydrochloride 6 and 5-bromo-
pyrimidine 7 to afford the corresponding alkynols 9 and 10,
respectively. Subsequent reduction of the alkynols under stan-
dard hydrogenation conditions produced the desired alkanols 11
and 12 in 76 and 97% overall yields, respectively.
The pyridine- and pyrimidine-containing monosubstituted
piperazines 16–19 were furnished from the aforementioned
alcohols 11 and 12, and from commercially available starting
materials 13 and 14 (Scheme 2) via activation as mesylates
and subsequent treatment with piperazine 15 in 53–63% yield.
These monosubstituted piperazines represent the precursors to
the target nitrogen-containing heterocycles with a three- and
four-atom hydrocarbon linker (5c–f), respectively.
The phenoxyalkylpiperazines 22 and 23 were synthesized by
alkylation of piperazine with the corresponding phenoxyalkyl
bromides(Scheme3)andpurifiedbydistillationtoaffordcolour-
less liquids in 76 and 81% yield, respectively. These compounds
represent the precursors to the target phenoxyalkyl analogues 5a
and 5b displaying a four-atom linker that investigate the effects
of isosteric replacement of CH2 for O.
unfortunately significantly lower (14 and 24%, respectively) by
this method compared with the titanium–amine method.
The phenylbutyl analogue of clozapine 5g was synthesized
according to the method detailed in Scheme 6. The alcohol 25
was oxidized to the corresponding aldehyde 26 (77%) using
pyridinium chlorochromate (PCC), then reacted under reduc-
tive amination conditions with desmethylclozapine 27 in the
presence of sodium triacetoxyborohydride to yield the desired
analogue 5g in 66% yield.
Receptor Binding Studies
Details of the in vitro assays for the synthesized compounds
are described in the Experimental section. Table 1 lists prelim-
inary percentage inhibition (% I) of radioligand binding at a
compound concentration of 10−6 M for the dopamine D4.4 (the
most common polymorphic variant of the D4 receptor)[8] and
serotonin 5-HT2A receptors for all test compounds. Data for
the compound corresponding to the 4ꢀ-phenylpropyl analogue of
clozapine (A = CH2; X,Y,Z = CH; n = 2) were also included for
comparative purposes, and provided a firmer basis for structure–
activity relationships pertaining to the length and nature of the
The target amidines 5a–d were synthesized according to
Scheme 4 in 42–81% yield, whereby the corresponding mono-
substituted piperazines were coupled to the tricyclic lactam
24 using the Lewis acid titanium tetrachloride. A drawback
associated with this method is the uneconomical use of ∼five
equivalents of monosubstituted piperazine for the formation of
the reactive titanium–amine complex and presence of an ‘acid-
binding agent’.[7] The synthesis of compounds 5e,f is outlined
in Scheme 5 whereby the lactam was converted to the activated
imino chloride intermediate by phosphorus pentachloride, and
subsequently treated with approximately two equivalents of the
monosubstitutedpiperazine.Theyieldsforcompounds5e,f were
H
N
H
N
N
A
(i)
ꢃ
A
Br
N
H
20 A ꢂ O(CH2)2
21 A ꢂ O(CH2)3
15
22 A ꢂ O(CH2)2
23 A ꢂ O(CH2)3
Scheme 3. Reagents and conditions: (i) toluene, 85◦C.
OH
OH
OH
Br
Y
(i)
(ii)
ꢃ
X
Z
X
X
Y
Z
Y
Z
8
6 X,Z ꢂ CH, Y ꢂ N
7 X,Z ꢂ N, Y ꢂ CH
·
HCl
9 X,Z ꢂ CH, Y ꢂ N
10 X,Z ꢂ N, Y ꢂ CH
11 X,Z ꢂ CH, Y ꢂ N
12 X,Z ꢂ N, Y ꢂ CH
Scheme 1. Reagents and conditions: (i) LiCl, CuI, Pd(Ph3P)4, Et3N, H2O, reflux, 2.5 h; (ii) 10% Pd/C, H2(g), EtOH,
room temp.
H
N
O
S
A
O
CH3
A
OH
(i)
(ii)
N
A
O
X
X
H
N
Y
Z
Y
Z
Z
Y
11 X,Z ꢂ CH, Y ꢂ N, A ꢂ (CH2)4
12 X,Z ꢂ N, Y ꢂ CH, A ꢂ (CH2)4
13 X ꢂ N, Y,Z ꢂ CH, A ꢂ (CH2)3
14 X,Z ꢂ CH, Y ꢂ N, A ꢂ (CH2)3
X
N
H
16 X,Z ꢂ CH, Y ꢂ N, A ꢂ (CH2)4
17 X,Z ꢂ N, Y ꢂ CH, A ꢂ (CH2)4
18 X ꢂ N, Y,Z ꢂ CH, A ꢂ (CH2)3
19 X,Z ꢂ CH, Y ꢂ N, A ꢂ (CH2)3
15
Scheme 2. Reagents and conditions: (i) methanesulfonyl chloride, Et3N, CH2Cl2, −50◦C; (ii) tetrahydrofuran or 1,2-dimethoxyethane, reflux.

Analogues of Clozapine. IV
933
H
N
H
N
H
N
Cl
(i)
N
ꢃ
N
A
N
Cl
NH
O
5a X ꢂ CH, Y ꢂ CH, A ꢂ O(CH2)2
5b X ꢂ CH, Y ꢂ CH, A ꢂ O(CH2)3
5c X ꢂ N, Y ꢂ CH, A ꢂ (CH2)3
5d X ꢂ CH, Y ꢂ N, A ꢂ (CH2)3
N
X
Y
24
Y
A
X
22 X ꢂ CH, Y ꢂ CH, A ꢂ O(CH2)2
23 X ꢂ CH, Y ꢂ CH, A ꢂ O(CH2)3
18 X ꢂ N, Y ꢂ CH, A ꢂ (CH2)3
19 X ꢂ CH, Y ꢂ N, A ꢂ (CH2)3
Scheme 4. Reagents and conditions: (i) TiCl4, anisole, 25–55◦C, reflux.
H
N
H
N
Cl
N
(i)
N
Cl
H
NH
N
(ii)
N
O
Z
X
24
Y
A
N
A
Z
Y
5e X,Z ꢂ CH, Y ꢂ N, A ꢂ (CH2)4
5f X,Z ꢂ N, Y ꢂ CH, A ꢂ (CH2)4
X
16 X,Z ꢂ CH, Y ꢂ N, A ꢂ (CH2)4
17 X,Z ꢂ N, Y ꢂ CH, A ꢂ (CH2)4
Scheme 5. Reagents and conditions: (i) PCl5, dichloromethane, reflux, 1 h; (ii) 1,4-dioxan, reflux.
H
N
HO
O
Cl
(CH2)3
N
(CH2)3
(ii)
N
(i)
N
H
N
N
Z
X
Cl
Y
A
25
26
N
27
5g X,Y,Z ꢂ CH, A ꢂ (CH2)4
HN
Scheme 6. Reagents and conditions: (i) pyridinium chlorochromate (PCC), SiO2, dichloromethane, room temp.;
(ii) NaBH(OAc)3, 1,2-dichloroethane, room temp.
linker between the distal nitrogen atom N4ꢀ and the introduced
aryl ring.
enhanced affinity. It was also evident within this series that iso-
steric replacement of CH2 (phenylpropyl analogue) for O (5a)
improved the affinity for the D4.4 receptor relative to clozap-
ine while maintaining a somewhat comparable affinity for the
5-HT2A receptor. Additionally, replacement of the phenyl ring
(phenylpropyl analogue) with a pyridin-4-yl ring (5d) improved
the D4.4 affinity but reduced the 5-HT2A affinity compared with
clozapine, whereas the isomeric pyridin-3-yl analogue 5c dis-
played essentially the opposite effect. The analogues containing
a four-atom linker displayed excellent affinity for both receptor
systems compared with clozapine except for the pyrimidin-5-yl
analogue 5f, which displayed somewhat reduced D4.4 affinity.
Isosteric replacement of CH2 (5g) for O (5b) within this set
of compounds displayed no discernible difference in overall
In general, all test compounds showed comparable or better
affinity for the dopamine D4.4 receptor than clozapine (72% I)
except for the pyridin-3-ylpropyl (5c) and pyrimidin-5-ylbutyl
(5f) analogues, which were only marginally reduced (61% I
and 64% I, respectively). Equally, their affinity for the sero-
tonin 5-HT2A receptor was comparable with clozapine (85% I),
with the pyridin-4-ylpropyl analogue 5d demonstrating the least
inhibition of radioligand (72% I). The analogues containing
a three-atom linker, namely the phenylpropyl and pyridin-
3-ylpropyl 5c compounds, showed reduced affinity for the
dopamine D4.4 receptor compared with clozapine, whereas the
phenoxypropyl (5a) and pyridin-4-yl (5d) analogues displayed

934
B. Capuano et al.
Table 1. Preliminary binding studies
Table 2. Antagonism of apomorphine-induced climbing in mice
∗Compounds with statistically significant (P < 0.05) activity
H
N
Cl
CompoundA
Climbing indexB
% Inhibition of climbing
N
N
Apomorphine
Vehicle
Clozapine
4ꢀ-Phenylpropyl analogue
5a
5b
5c
5d
5e
5f
18.2 1.5
0.4 0.4
—
—
63
0C
37
71
7
47
69
32
89
6.8 2.6∗
18.8 0.5C
11.5 2.6
5.2 3.2∗
17.0 2.0
9.6 2.0∗
5.6 3.9∗
12.4 3.4
2.0 1.1∗
N
R
Compound
Clozapine
R
Binding affinity percentage
inhibition (% I) at 10−6 M
A
A
D4.4
5-HT2A
[3H]spiperone [3H]ketanserin
5g
CH3
72
40B
1
85
87B
1
AAll compounds were tested as their hydrochloride salts at a dose of
10 mg kg−1 intraperitoneal (ip).
4ꢀ-Phenylpropyl
analogue
CH2
CH2
BValues represent the mean s.e.m. climbing index.
CDetermined previously;[6] reference climbing index value for clozapine
hydrochloride was 12.8 1.3 at a dose of 10 mg kg−1 ip; climbing indices
for apomorphine hydrochloride (3 mg kg−1 ip) and vehicle were 18.2 1.5
and 0.4 0.4, respectively. Values represent the mean s.e.m.
5a
5b
5c
85
81
61
2
3
1
77
83
88
1
1
2
O
O
CH2
CH2
antipsychotic efficacy.[9–12] The mice were pretreated with
clozapine (10 mg kg−1 intraperitoneal (ip)) and test compounds
(10 mg kg−1 ip), as their hydrochloride salts, 30 min before an
injection of apomorphine hydrochloride (3.0 mg kg−1 ip) and
theirclimbingbehaviourassessed.Theresultsofthisbehavioural
assay are displayed in Table 2. Clozapine effectively dimin-
ished apomorphine-induced climbing in mice at 10 mg kg−1
ip, displaying 63% inhibition of climbing. The analogues 5b
(phenoxypropyl), 5e (pyridin-4-ylbutyl), and 5g (phenylbutyl)
were the standout compounds and significantly antagonized
the apomorphine-induced climbing behaviour in mice, with the
phenylbutyl analogue 5g displaying 89% inhibition of climb-
ing. These compounds contain a four-atom spacer between the
ionizable nitrogen atom and the introduced aryl ring and exhib-
ited an appreciably greater potency compared with clozapine.
Isosteric replacement (5b) and the inclusion of a heterocycle
(5e) appeared to maintain in vivo activity compared with the
saturated hydrocarbon linker and phenyl ring of the phenyl-
butyl analogue. Of the analogues containing a three-atom spacer,
only the pyridin-4-ylpropyl compound 5d displayed statisti-
cally significant antagonism of apomorphine-induced climbing
(47% inhibition) that was comparable with clozapine and greatly
enhanced compared with the benchmark phenylpropyl analogue.
The two compounds showing the worst anticlimbing activity cor-
respond to the pyridin-3-ylpropyl (5c) and pyrimidin-5-ylbutyl
(5f), which also happen to display the least affinity for the
dopamine D4.4 receptor.Although exhibiting a favourable recep-
tor binding profile, the phenoxypropyl analogue 5a showed
only a modest reduction in climbing (37% inhibition), which
failed to be statistically significant; however, greater significant
anticlimbing activity was observed at higher doses (climbing
index = 8.6 1.1 at 30 mg kg−1 ip). Overall, the in vivo data
suggest that substitution for methyl at the N4ꢀ position of cloza-
pine with the designated substituents has quite a variable effect
on behavioural activity with no definitive structure–activity cor-
relation. This may be attributed to insufficient receptor binding
data at the target and other receptor systems implicated in
this complex behavioural model. Pharmacokinetic factors and
physicochemical properties such as log P, molecular volume and
N
CH2
5d
5e
5f
85
78
64
1
2
7
72
87
85
2
1
2
N
N
CH2
CH2
CH2
N
N
5g
82
3
77
1
ADetermined in duplicate by MDS Pharma Services (Taiwan).
BDetermined in duplicate by PANLABS (Taiwan) at a concentration of
10−6 M for the tested compound and representing the mean of duplicate
tubes with a maximum standard error in the mean of 5; reference values
for clozapine (10−6 M) were 54% I and 90% I for the dopamine D4.4 and
serotonin 5-HT2A receptors, respectively.
receptor affinity as did replacement of the phenyl ring (5g) with
a pyridin-4-yl ring (5e). In general, the receptor binding data
suggest that substitution for methyl at the N4ꢀ position with
the designated substituents essentially maintains dopamine D4.4
and serotonin 5-HT2A affinity relative to clozapine. Based on
the affinity data from this initial receptor binding screen, all
compounds were selected for further investigation in a prelim-
inary in vivo behavioural assay that is predictive of potential
antipsychotic efficacy.
In Vivo Behavioural Studies
All the target compounds in the present study were evaluated
in vivo for their ability to antagonize apomorphine-induced
climbing in mice, a psychosis-related behavioural model pre-
dictive of mesolimbic, dopaminergic activity, and potential

Analogues of Clozapine. IV
935
polar surface area may also, in part, influence the variability in
activity.
Ultraspec 2000 UV-visible spectrometer utilising Swift II soft-
ware. Wavelengths of maximum absorbance (λmax) are quoted
with respective molar absorptivities (ε). 1H and 13C NMR
(nuclear magnetic resonance) spectra were recorded at 300.13
and 75.47 MHz respectively in CDCl3 using a Brüker Avance
DPX 300 spectrometer equipped with a Silicon Graphics work
station. Chemicalshifts(δ)forall1Hand13Cspectraarereported
in parts per million (ppm) using tetramethylsilane (TMS, 0 ppm)
and deuterated chloroform (CDCl3, 77.16 ppm or as specified)
as the reference, respectively, unless otherwise stated. In report-
ing spectral data, the following abbreviations have been used:
s, singlet; d, doublet; t, triplet; q, quartet; p, quintet; m, multi-
plet; br, broad; app, apparent; J, coupling constant in Hz; C,
quaternary carbon; CH, methine carbon; CO, carbonyl carbon;
CH2, methylene carbon; CH3, methyl carbon. Electrospray ion-
ization (ESI) mass spectra (MS) were determined in positive
ion mode using a Micromass Platform II mass spectrometer.
High-resolution MS were determined using a Brüker BioApex
II FTICR mass spectrometer. TLC was carried out routinely on
silica gel 60F254 precoated plates (0.25 mm, Merck). Flash col-
umn chromatography was carried out using Merck silica gel
60, 230–400 mesh ASTM. All solvents were distilled before
use. Tetrahydrofuran (THF) was distilled from sodium metal
and benzophenone ketyl under nitrogen immediately before use.
Distilled dichloromethane was stored over Type 4 Å molecu-
lar sieves. 1,4-Dioxan was distilled from phosphorus pentoxide
under nitrogen and stored over sodium metal.All chemicals used
were purchased from Sigma–Aldrich Pty Ltd.
Conclusions
A series of 4ꢀ-arylalkyl analogues of clozapine were synthesized
based on a new structural model derived from the super-
imposition of X-ray crystal structures of clinically prescribed
antipsychotics. These compounds were designed to investigate
the biochemical effects of isosteric replacement (CH2 for O)
and varying aromaticity (phenyl for heterocycle) compared with
previously published clozapine analogues. Preliminary in vitro
bindingdatarevealedthatalltargetanaloguesexhibiteddesirable
affinity for the dopamine D4.4 and serotonin 5-HT2A receptors
compared with clozapine, with the pyridin-3-ylpropyl (5c) and
the pyrimidin-5-ylbutyl (5f) analogues showing slightly reduced
D4.4 affinity.The binding data suggest that both receptor systems
favoured a linker of three to four atoms in length, and are tolerant
to isosteric replacement and substitution of a phenyl ring for a
heterocycle such as a pyridinyl.
An in vivo investigation of this series showed that three
of the target compounds (5b, 5e, and 5g), corresponding to
the phenoxypropyl, pyridin-4-ylbutyl, and phenylbutyl ana-
logues, respectively, dramatically diminished apomorphine-
induced climbing in mice. These results compared favourably
with clozapine’s anti-climbing properties. The behavioural data
have significantly contributed to refining the structural model
andstronglysuggestthatanaloguescontainingafour-atomlinker
(saturated hydrocarbon and isosteric replacement of CH2 for O)
between the ionizable nitrogen atom and the introduced aryl
system (phenyl and pyridinyl) afford potential antipsychotic
activity. Therefore, the aforementioned three lead compounds
will form the basis for further structural investigation and phar-
macological evaluation in our research group, in pursuit of the
elusive ‘ideal’ antipsychotic drug.
4-(4-Pyridinyl)but-3-yn-1-ol 9
To a stirred solution of 4-bromopyridine hydrochloride (6,
2.99 g, 15.4 mmol) in triethylamine (30 mL) and water (6 mL)
was added lithium chloride (69.8 mg, 1.54 mmol), copper(i)
iodide (81.4 mg, 0.462 mmol) and but-3-yn-1-ol (8, 1.30 g,
18.5 mmol). The reaction mixture was stirred for 15 min under
nitrogen, after which tetrakis(triphenylphosphine)palladium
(160 mg)wasaddedandthereactionmixturewasheatedatreflux
for 2.5 h. Then the mixture was cooled, concentrated under vac-
uum, treated with sodium hydroxide solution (1 M, 40 mL) and
the product extracted with chloroform (3 × 30 mL).The solution
was concentrated under vacuum and the product was purified
Experimental
General
Melting points were determined on a Reichert Micro-melting
point apparatus and are uncorrected. Elemental analyses were
carried out on samples dried under vacuum by Microanalyti-
cal Service, Chemistry Department, University of Queensland,
Brisbane, or Chemical & Micro Analytical Services Pty Ltd,
Belmont, Victoria, Australia. Analytical reverse-phase high-
performance liquid chromatography (HPLC) was performed on
target compounds converted to hydrochloride salts by treatment
with 1 M hydrogen chloride in diethyl ether and evaporated
to dryness, using a Waters HPLC system fitted with a Waters
Nova-Pak C18 Radial-Pak cartridge (8 mm × 100 mm, 6 µm,
60 Å) inside a Waters 8 × 10 compression module using a
binary system (solvent A: 0.1% TFA/H2O and solvent B: 0.1%
TFA/90% CH3CN/H2O). Analyses were conducted using iso-
cratic (60% A/40% B) and gradient elution mode (100% A to
100% B over 30 min) at 1.5 mL min−1 flow rate, UV detection
at 254 nm. IR spectra were recorded on Bio-Rad FTS 3500GX
utilising Merlin software for solids with KBr powder as back-
ground and on a Hitachi 270–30 infrared spectrophotometer
with NaCl discs for oils or as a neat compound on a Scimitar
Series Varian 800 Fourier-transform (FT) IR spectrophotometer
with a PIKE Technologies MIRacle ATR. UV-Visible spectra
were recorded as ethanolic solutions on a Pharmacia Biotech
via flash chromatography (ethyl acetate), to afford a pale brown
[13]
solid (2.25 g, 99%). δH
8.48 (2H, dd, J 4.5, 1.5, H2ꢀ, H6ꢀ),
7.23 (2H, dd, J 4.5, 1.5, H3ꢀ, H5ꢀ), 4.47 (1H, br s, OH), 3.84 (2H,
t, J 6.5, H1), 2.70 (2H, t, J 6.5, H2). δC 149.2 (CH), 132.3 (C),
126.0 (CH), 93.3 (C), 79.4 (C), 60.5 (CH2), 23.9 (CH2).
4-(5-Pyrimidinyl)but-3-yn-1-ol 10
To a stirred solution of 5-bromopyrimidine (7, 3.01 g,
18.9 mmol) in triethylamine (30 mL) and water (6 mL)
was added lithium chloride (62.5 mg, 1.38 mmol), copper(i)
iodide (73.8 mg, 0.419 mmol), and but-3-yn-1-ol (8, 1.16 g,
16.5 mmol). The reaction mixture was stirred for 15 min under
nitrogen, after which tetrakis(triphenylphosphine)palladium
(160 mg) was added and the reaction was worked up as for the
preparation of 4-(4-pyridinyl)but-3-yn-1-ol (9) to afford a pale
brown solid (2.02 g, 83%). δH[13] 9.08 (1H, s, H2ꢀ), 8.73 (2H, s,
H4ꢀ, H6ꢀ), 4.29 (1H, br s, OH), 3.86 (2H, t, J 6.5, H1), 2.74 (2H,
t, J 6.5, H2). δC 158.6 (CH), 155.9 (CH), 120.0 (C), 95.3 (C),
74.8 (C), 60.2 (CH2), 23.7 (CH2).

936
B. Capuano et al.
4-(4-Pyridinyl)butan-1-ol 11
1-[4-(5-Pyrimidinyl)butyl]piperazine 17
To a stirred solution of 4-(4-pyridinyl)but-3-yn-1-ol (9, 2.25 g,
15.3 mmol) in ethanol (50 mL) was added palladium-on-carbon
(10%, 240 mg). The mixture was hydrogenated at atmospheric
pressure for 4 h, after which further 10% Pd/C (100 mg) was
added and hydrogenation continued for an additional 2 h. The
catalyst was removed by filtration through a Celite pad, washed
with methanol and the filtrate concentrated under vacuum to
To a stirred solution of the 4-(5-pyrimidinyl)butan-1-ol (12,
2.06 g, 13.9 mmol) and triethylamine (4.50 g, 44.5 mmol) in dry
dichloromethane (20 mL) at −50◦C under nitrogen was added
methanesulfonyl chloride (1.13 mL, 14.6 mmol) dropwise and
the mesylate was worked up as described for the preparation
of 16. The crude mesylate was taken up in dimethoxyethane
(20 mL) to which solid piperazine (15, 3.05 g, 35.6 mmol) was
added. The reaction mixture was heated at reflux for 6 h and
worked up as described for the preparation of 16. The result-
ing residue was purified using flash chromatography (100:30:3
ethyl acetate/methanol/25% w/v aqueous ammonia) affording,
on evaporation, the title compound as a yellow oil, which crys-
tallized as pale yellow waxy needles on standing (1.17 g, 39%),
mp 50–53◦C. δH 9.06 (1H, s, H4ꢀꢀ), 8.58 (2H, s, H2ꢀꢀ, H6ꢀꢀ), 2.90
(4H, br s, H3, H5), 2.64 (2H, t, J 7.5, H1ꢀ), 2.36 (6H, m, H2, H6,
H4ꢀ), 1.68 (3H, m, H4, H2ꢀ), 1.55 (2H, m, H3ꢀ). δC 156.7 (CH),
156.6 (CH), 135.2 (C), 58.7 (CH2), 54.5 (CH2), 46.0 (CH2),
30.3 (CH2), 28.5 (CH2), 26.1 (CH2). m/z (ESI, 70V) 221 (MH+,
28%), 177 (39), 135 (39), 93 (100), 84 (54), 66 (30).
afford the product as an orange-brown liquid (2.26 g, 98%).
[14]
δH
8.41 (2H, d, J 4.5, H2ꢀ, H6ꢀ), 7.10 (2H, d, J 5.5, H3ꢀ,
H5ꢀ), 3.96 (1H, br s, OH), 3.67 (2H, t, J 7.5, H1), 2.63 (2H, t,
J 7.5, H4), 1.72 (2H, m, H2), 1.61 (2H, m, H3). δC 151.8 (C),
149.2 (CH), 124.0 (CH), 61.8 (CH2), 34.9 (CH2), 32.2 (CH2),
26.5 (CH2).
4-(5-Pyrimidinyl)butan-1-ol 12
To a stirred solution of 4-(5-pyrimidinyl)but-3-yn-1-ol (10,
2.02 g, 13.6 mmol) in ethanol (50 mL) was added Pd/C (10%,
300 mg). The mixture was hydrogenated at atmospheric pres-
sure overnight, after which further 10% Pd/C (100 mg) was
added and hydrogenation continued for another hour. The cata-
lyst was removed by filtration through a Celite pad, washed with
methanol, and the filtrate concentrated under vacuum to afford
the product[15] as an orange-brown liquid (1.88 g, 91%). δH 9.04
(1H, s, H2ꢀ), 8.59 (2H, s, H4ꢀ, H6ꢀ), 3.68 (2H, t, J 6, H1), 3.44
(1H, br s, OH), 2.67 (2H, t, J 7.5, H4), 1.75 (2H, m, H2), 1.63
(2H, m, H3). δC 156.8 (CH), 156.7 (CH), 135.3 (C), 62.2 (CH2),
32.1 (CH2), 30.3 (CH2), 27.1 (CH2).
1-[3-(3-Pyridinyl)propyl]piperazine 18
To a stirred solution of 3-(3-pyridinyl)propan-1-ol (13, 2.0 g,
14.7 mmol) and triethylamine (2.95 g, 29.1 mmol) in dry
dichloromethane (20 mL) at −50◦C was added methanesulfonyl
chloride (1.92 mL, 24.7 mmol) dropwise and the mesylate was
worked up as described for the preparation of 16. The crude
mesylate was taken up in THF (20 mL) to which solid piper-
azine (15, 5.00 g, 61.0 mmol) was added. The reaction mixture
was heated at reflux overnight and extracted as described for
the preparation of 16. The organic extract was washed with
water and dried over dry magnesium sulfate. The solution was
evaporated to dryness and the residue purified by vacuum dis-
tillation affording a very pale yellow oil (1.69 g, 56%), bp
185–195◦C/0.1 mm Hg. δH[16] 8.45 (1H, d, J 2, H2ꢀꢀ), 8.43 (1H,
dd, J 5, 1.5, H6ꢀꢀ), 7.50 (1H, m, H5ꢀꢀ), 7.20 (1H, m, H4ꢀꢀ), 2.89
(4H, m, H3, H5), 2.65 (2H, m, H3ꢀ), 2.40 (4H, m, H2, H6), 2.34
(2H, m, H1ꢀ), 1.97 (1H, s, H4), 1.82 (2H, app p, J 7.5, H2ꢀ).
δC 150.2 (CH), 147.5 (CH), 137.5 (C), 135.9 (CH), 123.4 (CH),
58.3 (CH2), 54.7 (CH2), 46.3 (CH2), 30.9 (CH2), 28.1 (CH2).
m/z (ESI, 30V) 207 (MH+, 15%) 206 (100), 113 (40), 94 (29).
1-[4-(4-Pyridinyl)butyl]piperazine 16
To a stirred solution of the 4-(4-pyridinyl)butan-1-ol (11,
1.97 g, 13.4 mmol) and triethylamine (3.10 g, 30.6 mmol) in dry
dichloromethane (20 mL) at −50◦C under nitrogen was added
methanesulfonyl chloride (1.80 mL, 22.4 mmol) dropwise. The
reaction mixture was slowly warmed up to 0◦C when the mixture
became orange, after which the mixture was promptly trans-
ferred to a separating funnel, washed with cold water and the
product was extracted with cold dichloromethane (3 × 20 mL).
The organic fractions were combined, washed with water, dried
over magnesium sulfate and the majority of dichloromethane
was removed under vacuum. The red mesylate solution (∼5 mL)
was diluted with dimethoxyethane (20 mL) and solid piperazine
(15, 5.16 g, 59.8 mmol) was added. The reaction mixture was
heated at reflux for 3 h, after which the mixture was evaporated to
dryness and the residue partitioned between aqueous hydrochlo-
ric acid solution (1 M, 30 mL) and dichloromethane (30 mL).
The organic layer was removed and the aqueous layer was
washed with dichloromethane (20 mL) and the pH adjusted to
14 with potassium hydroxide pellets. The product was extracted
with dichloromethane (3 × 40 mL), washed with water, dried
over magnesium sulfate and evaporated to dryness. The prod-
uct was purified using flash chromatography (100:30:3 ethyl
acetate/methanol/25% w/v aqueous ammonia) affording red-
brown oil. The product was further purified by distillation
affording pale yellow oil (1.80 g, 62%), bp 235–240◦C/0.5 mm
Hg. δH 8.48 (2H, dd, J 4.5, 1.5, H2ꢀꢀ, H6ꢀꢀ), 7.01 (2H, d, J 6,
H3ꢀꢀ, H5ꢀꢀ), 2.88 (4H, m, H3, H5), 2.62 (2H, t, J 7.5, H1ꢀ), 2.34
(6H, m, H2, H6, H4ꢀ), 1.91 (1H, s, H4), 1.66 (2H, m, H2ꢀ), 1.52
(2H, m, H3ꢀ). δC 151.4 (C), 149.8 (CH), 124.0 (CH), 59.2 (CH2),
55.3 (CH2), 46.2 (CH2), 35.2 (CH2), 28.3 (CH2), 26.3 (CH2).
m/z (ESI, 70V) 220 (MH+, 20%), 134 (38), 106 (100), 91 (23).
1-[3-(4-Pyridinyl)propyl]piperazine 19
To a stirred solution of the 3-(4-pyridinyl)propan-1-ol (14,
5.00 g, 36.4 mmol) and triethylamine (7.38 g, 72.8 mmol) in dry
dichloromethane (25 mL) at −50◦C under nitrogen was drop-
wise added methanesulfonyl chloride (4.80 mL, 62.0 mmol) and
the mesylate was worked up as described for the preparation of
16. The crude mesylate was taken up in anhydrous THF (25 mL)
to which solid piperazine (15, 12.5 g, 146 mmol) was added.The
reaction mixture was heated at reflux for 4 h and worked up as
described for the preparation of 16, affording the product, fol-
lowing vacuum distillation (3.95 g, 53%), as a pale yellow liquid,
bp 150–155◦C/0.3 mm Hg. δH 8.48 (2H, dd, J 4.5, 1.5, H2ꢀꢀ, H6ꢀꢀ)
7.11 (2H, dd, J 4.5, 1.5, H3ꢀꢀ, H5ꢀꢀ), 2.89 (4H, m, H3, H5), 2.64
(2H, t, J 7.5, H3ꢀ), 2.40 (4H, m, H2, H6), 2.33 (2H, t, J 7.5, H1ꢀ),
1.91 (1H, s, H4), 1.82 (2H, app p, J 7.5, H2ꢀ). δC 150.9 (C),
149.4 (CH), 123.6 (CH), 57.9 (CH2), 54.2 (CH2), 45.8 (CH2),
32.6 (CH2), 26.9 (CH2). m/z (+ESI, 100V) 206 (MH+, 100%),
120 (61).

Analogues of Clozapine. IV
937
1-(2-Phenoxyethyl)piperazine 22
8-Chloro-11-[4-(2-phenoxyethyl)piperazino]-
5H-dibenzo[b,e][1,4]diazepine 5a
A mixture of piperazine (15, 17.1 g, 199 mmol), β-bromo-
phenetole (20, 10.0 g, 49.7 mmol), and toluene (250 mL) was
stirred at 85◦C for 2 h, after which it was cooled, filtered, and the
filtrate concentrated under vacuum. The resulting residue was
partitioned between aqueous hydrochloric acid (2 M, 70 mL)
and dichloromethane and the aqueous phase washed with
dichloromethane (100 mL). The aqueous phase was adjusted
to pH 14 with solid sodium hydroxide and extracted with
dichloromethane (100 mL, 2 × 50 mL). The organic fractions
were combined, washed with water (50 mL), dried over anhy-
drous sodium sulfate, filtered and then concentrated under
vacuum.The product was purified by vacuum distillation to yield
a colourless oil (7.78 g, 76%), bp 175–180◦C/1.5 mm Hg (lit.[17]
143–144◦C/0.53 mm Hg). νmax/cm−1 3274, 3064, 2938, 2818,
1599. δH 7.23–7.29 (2H, m, H3ꢀꢀ, H5ꢀꢀ), 6.88–6.95 (3H, m, H2ꢀꢀ,
H4ꢀꢀ, H6ꢀꢀ), 4.09 (2H, t, J 6, H2ꢀ), 2.89 (4H, m, H3, H5), 2.77
(2H, t, J 6, H1ꢀ), 2.52 (4H, m, H2, H6), 1.65 (1H, s, H4). δC
158.8 (C), 129.4 (CH), 120.5 (CH), 114.6 (CH), 65.7 (CH2),
58.8 (CH2), 55.0 (CH2), 46.1 (CH2). m/z (+ESI, 20V) 207
(MH+, 100%).
To a solution of 1-(phenoxyethyl)piperazine (22, 1.27 g,
6.14 mmol) in anhydrous anisole (5 mL) under nitrogen was
added a solution of titanium tetrachloride in toluene (1 M,
1.4 mL, 1.4 mmol), which resulted in an immediate deep green
colour.The mixture was then warmed to 50–55◦C and a hot solu-
tion of 8-chloro-10,11-dihydro-5H-dibenzo[b,e][1,4]diazepine-
11-one (24, 300 mg, 1.23 mmol) in dry anisole (15 mL) was
added. The mixture was heated at reflux overnight, was cooled
and evaporated to dryness under vacuum. The residue was par-
titioned between ethyl acetate (80 mL) and aqueous sodium
hydroxide (1 M, 30 mL) and filtered. The organic layer was
separated and the aqueous phase extracted with ethyl acetate
(2 × 50 mL). The organic fractions were combined, washed with
water (2 × 30 mL), dried over anhydrous sodium sulfate and
evaporated to dryness. The resulting oily residue was purified
using flash chromatography (1:1 ethyl acetate/hexane) and the
major product evaporated to dryness. The product was recrys-
tallized from methanol/water to afford the title compound as
bright yellow crystals (430 mg, 81%), mp 79–81◦C. (Found:
C 67.1, H 6.2, N 11.9. C25H25ClN4O·CH3OH requires C 67.2,
H 6.3, N 12.1%). νmax (KBr)/cm−1 3352, 3060, 2932, 2840,
1600. λmax/nm (ε/M−1 cm−1) 216 (34670), 262 (17380), 298
(10720). δH ([D6]acetone) 7.33–7.36 (1H, m, H3), 7.24–7.32
(3H, m, H1, H3ꢀꢀꢀ, H5ꢀꢀꢀ), 7.00–7.09 (2H, m, H2, H4), 6.91 (5H,
m, H6, H9, H2ꢀꢀꢀ, H4ꢀꢀꢀ, H6ꢀꢀꢀ), 6.88 (1H, dd, J 8, 2, H7), 6.53 (1H,
s, H5), 4.15 (2H, t, J 6, H2ꢀꢀ), 3.43 (4H, m, H2ꢀ, H6ꢀ), 2.82 (2H,
t, J 6, H1ꢀꢀ), 2.67 (4H, m, H3ꢀ, H5ꢀ). δC ([D6]acetone) 164.1 (C),
160.0 (C), 155.1 (C), 150.9 (CH), 143.5 (C), 143.0 (C), 132.9
(CH), 131.0 (CH), 130.3 (CH), 128.6 (C), 127.0 (CH), 124.7 (C),
123.5 (CH), 121.4 (CH), 121.2 (CH), 115.5 (CH), 66.9 (CH2),
58.1 (CH2), 54.3 (CH2), 48.4 (CH2), 29.7 (CH2). m/z (+ESI,
70V) 435 (M[37Cl]H+, 10%), 433 (MH+, 25%), 296 (36), 273
(33), 270 (100).
1-(3-Phenoxypropyl)piperazine 23
A mixture of piperazine (15, 16.0 g, 186 mmol), 1-(3-
phenoxy)propyl bromide (21, 10.0 g, 46.5 mmol) and toluene
(250 mL) was stirred at 85◦C for 3 h and worked up as described
in the preparation of 22. Kugelrohr distillation afforded the prod-
uct as a pale yellow oil (8.30 g, 81%), bp 225◦C/2.5 mm Hg
(lit.[18,19] 115◦C/0.05 mm Hg), which formed a waxy solid on
standing, mp 48◦C. δH 7.25 (2H, m, H3ꢀꢀ, H5ꢀꢀ), 6.89 (3H, m,
H2ꢀꢀ, H4ꢀꢀ, H6ꢀꢀ), 3.99 (2H, t, J 6.5, H3ꢀ), 2.87 (4H, m, H3, H5),
2.49 (2H, m, H1ꢀ), 2.42 (4H, m, H2, H6), 1.95 (2H, app p, J 7,
H2ꢀ), 1.86 (1H, s, H4). δC 159.2 (C), 129.5 (CH), 120.7 (CH),
114.7 (CH), 66.3 (CH2), 55.9 (CH2), 54.8 (CH2), 46.3 (CH2),
26.7 (CH2). m/z (+ESI, 70V) 221 (MH+, 64%), 147 (31), 107
(43), 99 (100).
8-Chloro-11-[4-(3-phenoxypropyl)piperazino]-
5H-dibenzo[b,e][1,4]diazepine 5b
To a solution of 1-(3-phenoxypropyl)piperazine (23, 0.984 g,
4.47 mmol) in anhydrous anisole (5 mL) under nitrogen
was added a solution of titanium tetrachloride in toluene
(1.0 M, 0.90 mL, 0.90 mmol), which resulted in an immedi-
ate deep green colouration. The mixture was then warmed
to 55◦C and a hot solution of 8-chloro-10,11-dihydro-5H-
dibenzo[b,e][1,4]diazepine-11-one (24, 204 mg, 0.834 mmol) in
dry anisole (10 mL) was added.The mixture was heated at reflux
overnight after which time it was cooled and then evaporated to
dryness under vacuum. The reaction mixture was partitioned
between aqueous hydrochloric acid solution (1 M, 50 mL) and
ethyl acetate (75 mL). The aqueous layer was washed with ethyl
acetate and the pH was adjusted to 14 by potassium hydroxide
pellets.The product was extracted with ethyl acetate (3 × 50 mL)
and washed with water, dried over magnesium sulfate, then evap-
orated to dryness. The resulting oily residue was purified using
flash chromatography (4:1 ethyl acetate/hexane) and the major
product evaporated to dryness to afford the product as yellow
oil, which recrystallized from dichloromethane/hexane to afford
the title compound as yellow platelet crystals (183 mg, 49%),
mp 139–140◦C. (Found: C 69.9, H 6.1, N 12.4. C26H27ClN4O
requires C 69.9, H 6.1, N 12.5%). νmax (KBr)/cm−1 3353, 1602,
1563. λmax/nm (ε/M−1 cm−1) 217 (37150), 262 (18620), 296
(11480). δH 7.23–7.36 (4H, m, H1, H3, H3ꢀꢀꢀ, H5ꢀꢀꢀ), 7.07 (1H,
4-Phenylbutanal 26
Pyridinium chlorochromate (21.5 g, 66.6 mmol) was ground
with silica gel (21.5 g) using a mortar and pestle and the
resulting free-running light orange solid was suspended in
dichloromethane (200 mL) at room temperature. To the stirred
suspension was added a solution of 4-phenyl-1-butanol (25,
1.97 g, 10.2 mmol) in dichloromethane (10 mL) and stirring
maintained for 3 h. The mixture was filtered (Celite) and
the brown granular residue washed with dichloromethane
(2 × 500 mL). The resulting filtrate was concentrated under
vacuum, the residue taken up in dichloromethane (10 mL),
filtered through a silica gel plug and the residue washed
with dichloromethane. The combined filtrate was concentrated
under vacuum and the resulting oil distilled to give the prod-
uct aldehyde[20] (1.50 g, 77%) as a colourless liquid, bp 83–
84◦C/0.4 mm Hg (lit.[21] bp 120–122◦C/16 mm Hg). δH 9.68
(1H, t, J 1.5, H1), 7.21–7.30 (2H, m, H3ꢀ, H5ꢀ), 7.11–7.20 (3H,
m, H2ꢀ, H4ꢀ, H6ꢀ), 2.62 (2H, t, J 7.5, H4), 2.38 (2H, dt, J 7.5,
1.5, H2), 1.92 (2H, app p, J 7.5, H3). δC ([D3]acetonitrile) 203.7
(CH), 142.9 (C), 129.5 (2 × CH), 127.0 (CH), 43.8 (CH2), 35.7
(CH2), 24.7 (CH2). m/z (+ESI, 30V) 467 (3M + Na+, 28%),
209 (100), 91 (100).

938
B. Capuano et al.
m, H9), 7.02 (1H, m, H2), 6.91 (5H, m, H4, H7, H2ꢀꢀꢀ, H4ꢀꢀꢀ,
H6ꢀꢀꢀ), 6.81 (1H, dd, J 8.5, 2.5, H6), 6.52 (1H, s, H5), 4.07 (2H,
t, J 6.5, H3ꢀꢀ), 3.36 (4H, m, H2ꢀ, H6ꢀ), 2.55 (6H, m, H3ꢀ, H5ꢀ,
H1ꢀꢀ), 1.96 (2H, app p, J 6.5, H2ꢀꢀ). δC 164.1 (C), 160.3 (C),
155.1 (C), 143.5 (C), 142.9 (C), 132.8 (CH), 131.0 (CH), 130.3
(CH), 128.6 (C), 127.0 (CH), 124.7 (C), 123.5 (CH), 123.4 (CH),
121.4 (CH), 121.3 (CH), 121.2 (CH), 115.4 (CH), 66.7 (CH2),
55.7 (CH2), 54.0 (CH2), 48.4 (CH2), 27.7 (CH2). m/z (+ESI,
70V) 447 (MH+, 14%), 296 (30), 272 (33), 270 (100).
(CH), 124.9 (CH), 124.7 (C), 123.5 (CH), 123.4 (CH), 121.4
(CH), 121.2 (CH), 58.1 (CH2), 53.8 (CH2), 48.3 (CH2), 33.3
(CH2), 28.3 (CH2). m/z (+ESI, 70V) 434 (M[37Cl]H+, 11%),
432 (MH+, 30%), 272 (31), 270 (90), 192 (100), 120 (87).
8-Chloro-11-{4-[4-(4-pyridinyl)butyl]piperazino}-
5H-dibenzo[b,e][1,4]diazepine 5e
A mixture of phosphorus pentachloride (283 mg, 0.924 mmol)
and 8-chloro-10,11-dihydro-5H-dibenzo[b,e][1,4]diazepin-11-
one (24, 205 mg, 0.840 mmol) in dry dichloromethane (20 mL)
was heated at reflux for 1 h. The solvent was removed under
vacuum and the residue was azeotroped twice with benzene
and evaporated to dryness. The crude iminochloride was dis-
solved in anhydrous 1,4-dioxan (15 mL) and treated with
1-[4-(4-pyridinyl)butyl]piperazine (16, 356 mg, 1.62 mmol) in
anhydrous 1,4-dioxan (5 mL). The reaction mixture was heated
at reflux overnight, and worked up as described in the
preparation of 5b. The product was purified via flash chro-
matography (2:1 ethyl acetate/methanol) and the resulting oil
was recrystallized from dichloromethane/hexane to give the
title compound as yellow platelets (51 mg, 14%), mp 94–
95◦C. (Found: (MH+) 446.210. C26H29ClN5 requires (MH+)
446.211). HPLC (λ = 254 nm) retention time (tR) 3.40 min (iso-
cratic), tR 20.74 min (gradient). νmax (KBr)/cm−1 3259, 1608,
1560. λmax/nm (ε/M−1 cm−1) 229 (27540), 257 (19050), 296
(10960). δH 8.48 (2H, m, H2ꢀꢀꢀ, H6ꢀꢀꢀ), 7.26 (2H, m, H1, H3),
7.06 (1H, m, H9), 6.97–7.11 (2H, m, H3ꢀꢀꢀ, H5ꢀꢀꢀ), 7.00 (1H, m,
H2), 6.81 (2H, m, H4, H7), 6.60 (1H, d, J 8.5, H6), 4.90 (1H,
s, H5), 3.46 (4H, br s, H2ꢀ, H6ꢀ), 2.63 (2H, m, H1ꢀꢀ), 2.50 (4H,
m, H3ꢀ, H5ꢀ), 2.40 (2H, m, H4ꢀꢀ), 1.68 (2H, m, H2ꢀꢀ), 1.55 (2H,
m, H3ꢀꢀ). δC 162.9 (C), 152.9 (C), 151.4 (C), 149.9 (CH), 142.0
(C), 140.5 (C), 132.0 (CH), 130.4 (CH), 129.2 (C), 126.9 (CH),
124.0 (CH), 123.6 (C), 123.2 (CH), 123.1 (CH), 120.2 (CH),
120.1 (CH), 58.5 (CH2), 53.3 (CH2), 47.4 (CH2), 35.2 (CH2),
28.3 (CH2), 26.5 (CH2). m/z (+ESI, 70V) 446 (MH+, 10%),
296 (23), 272 (32), 270 (100).
8-Chloro-11-{4-[3-(3-pyridinyl)propyl]piperazino}-
5H-dibenzo[b,e][1,4]diazepine 5c
1-[3-(3-Pyridinyl)propyl]piperazine (18, 1.05 g, 5.10 mmol) in
anhydrous anisole (5 mL) was treated with a solution of tita-
nium tetrachloride in toluene (1.0 M, 1.12 mL, 1.12 mmol),
followed by a hot solution of 8-chloro-10,11-dihydro-5H-
dibenzo[b,e][1,4]diazepin-11-one (24, 250 mg, 1.02 mmol) in
dry anisole (10 mL) and worked up as described in the prepara-
tion of 5b. The product was purified via flash chromatography
(2:1 ethyl acetate/methanol) and the resulting yellow oil was
recrystallized from methanol/water to yield the title compound
as yellow prisms (184 mg, 42%), mp 83–85◦C. (Found: C 64.4,
H 6.6, N 14.2. C25H26ClN5·CH3OH·H2O requires C 64.8, H
6.7, N 14.5%). νmax (KBr)/cm−1 3255, 1605, 1554. λmax/nm
(ε/M−1 cm−1) 228 (29510), 262 (21880), 295 (12020). δH 8.44
(2H, m, H2ꢀꢀꢀ, H6ꢀꢀꢀ), 7.50 (1H, d, J 7.5, H5ꢀꢀꢀ), 7.18–7.30 (3H,
m, H1, H3, H4ꢀꢀꢀ), 7.06 (1H, d, J 2.5, H9), 6.99 (1H, t, J 7.5, H2),
6.80 (2H, dd, J 8.5, 2.5, H4, H7), 6.60 (1H, d, J 8.5, H6), 4.96
(1H, s, H5), 3.47 (4H, s, H2ꢀ, H6ꢀ), 2.66 (2H, t, J 7.5, H1ꢀꢀ), 2.51
(4H, s, H3ꢀ, H5ꢀ), 2.41 (2H, t, J 7.5, H3ꢀꢀ), 1.84 (2H, app p, J 7.5,
H2ꢀꢀ). δC 162.9 (C), 152.9 (C), 150.0 (CH), 147.4 (CH), 142.0
(C), 140.6 (C), 137.4 (C), 136.0 (CH), 132.0 (CH), 130.4 (CH),
129.1 (C), 126.9 (CH), 123.6 (C), 123.4 (CH), 123.2 (CH), 123.1
(CH), 120.2 (CH), 120.1 (CH), 57.7 (CH2), 53.2 (CH2), 47.4
(CH2), 30.8 (CH2), 28.2 (CH2). m/z (+ESI, 30V) 432 (MH+,
32%), 432 (100), 430 (25).
8-Chloro-11-{4-[3-(4-pyridinyl)propyl]piperazino}-
5H-dibenzo[b,e][1,4]diazepine 5d
8-Chloro-11-{4-[4-(5-pyrimidinyl)butyl]piperazino}-
5H-dibenzo[b,e][1,4]diazepine 5f
1-[3-(4-Pyridinyl)propyl]piperazine (19, 1.05 g, 5.11 mmol) in
anhydrous anisole (5 mL) was treated with a solution of tita-
nium tetrachloride in toluene (1.0 M, 1.13 mL, 1.13 mmol),
followed by a hot solution of 8-chloro-10,11-dihydro-5H-
dibenzo[b,e][1,4]diazepin-11-one (24, 250 mg, 1.02 mmol) in
dry anisole (10 mL) and worked up as for the preparation of 5b.
The product was purified via flash chromatography (3:1 ethyl
acetate/methanol), redissolved in dichloromethane (10 mL), fil-
tered, concentrated under vacuum and then recrystallized from
methanol/water to give the title compound as bright yellow
prisms (211 mg, 48%), mp 92–96◦C. (Found: C 67.1, H 6.4,
N 15.5. C25H26ClN5·CH3OH requires C 67.3, H 6.5, N 15.1%).
νmax (KBr)/cm−1 3276, 1602, 1560. λmax/nm (ε/M−1 cm−1) 228
(29510), 258 (20420), 296 (11750). δH ([D6]acetone) 8.45 (2H,
dd, J 4.5, 1.5, H2ꢀꢀꢀ, H6ꢀꢀꢀ), 7.33 (1H, m, H3), 7.29 (1H, m, H1),
7.23 (2H, dd, J 4.5, 1.5, H3ꢀꢀꢀ, H5ꢀꢀꢀ), 7.07 (1H, dd, J 8, 1, H4),
7.02 (1H, app td, J 7.5, 1, H2), 6.95 (1H, d, J 2.5, H9), 6.88 (1H,
d, J 8.5, H6), 6.81 (1H, dd, J 8.5, 2.5, H7), 6.58 (1H, s, H5),
3.41 (4H, m, H2ꢀ, H6ꢀ), 2.70 (2H, t, J 7.5, H3ꢀꢀ), 2.50 (4H, m,
H3ꢀ, H5ꢀ), 2.38 (2H, t, J 7.5, H1ꢀꢀ), 1.84 (2H, app p, J 7.5, H2ꢀꢀ).
δC ([D6]acetone) 164.1 (C), 155.0 (C), 152.1 (C), 150.5 (CH),
143.4 (C), 142.9 (C), 132.8 (CH), 131.0 (CH), 128.5 (C), 127.0
A mixture of phosphorus pentachloride (187 mg, 0.920 mmol)
and 8-chloro-10,11-dihydro-5H-dibenzo[b,e][1,4]diazepin-11-
one (24, 204 mg, 0.836 mmol) in dry dichloromethane (20 mL)
was heated at reflux for 1 h. The solvent was removed under
vacuum and the residue was azeotroped twice with benzene
and evaporated to dryness. The crude iminochloride was dis-
solved in anhydrous 1,4-dioxan (15 mL) and treated with the
1-[4-(5-pyrimidinyl)butyl]piperazine (17, 370 mg, 1.68 mmol)
in anhydrous 1,4-dioxan (5 mL). The reaction mixture was
heated at reflux for 19 h, and worked up as described in the prepa-
ration of 5b. The product was purified via flash chromatography
(10:3:0.03 ethyl acetate/methanol/25% w/v ammonia solution)
and recrystallized from methanol/water to afford the title com-
pound as yellow microcrystals (89 mg, 24%), mp 91–92◦C.
(Found: C 65.5, H 6.2, N 17.8. C25H27ClN6·CH3OH requires
C 65.2, H 6.5, N 17.5%). νmax (KBr)/cm−1 3270, 1607, 1561.
λmax/nm (ε/M−1 cm−1) 229 (25700), 259 (18200), 293 (10720).
δH 9.07 (1H, s, H2ꢀꢀꢀ), 8.58 (2H, s, H4ꢀꢀꢀ, H6ꢀꢀꢀ), 7.27 (2H, m,
H1, H3), 7.06 (1H, d, J 2.5, H9), 7.00 (1H, m, H2), 6.81 (2H,
m, H4, H7), 6.60 (1H, d, J 8.5, H6), 4.90 (1H, s, H5), 3.46 (4H,
m, H2ꢀ, H6ꢀ), 2.64 (2H, m, H1ꢀꢀ), 2.50 (4H, m, H3ꢀ, H5ꢀ), 2.42
(2H, m, H4ꢀꢀ), 1.70 (2H, m, H2ꢀꢀ), 1.57 (2H, m, H3ꢀꢀ). δC 162.8

Analogues of Clozapine. IV
939
(C), 156.9 (CH), 156.8 (2 × CH), 152.99 (C), 142.0 (C), 140.5
(C), 135.3 (C), 132.0 (CH), 130.4 (CH), 129.2 (C), 126.9 (CH),
123.6(C), 123.2(CH), 123.1(CH), 120.2(CH), 120.1(CH), 58.3
(CH2), 53.3 (CH2), 47.4 (CH2), 30.4 (CH2), 28.7 (CH2), 26.4
(CH2). m/z (+ESI, 70V) 447 (MH+, 10%), 272 (32), 270 (100),
91 (75).
Antagonism of Apomorphine-Induced Climbing in Mice
Adultfemalemice(20–33 g)wereusedforalltheexperiments
and housed five per cage under controlled conditions of temper-
ature (20 1◦C) and 12-h light/dark cycle (lights on 0600–1800
hours), with free access to food and tap water. The animals were
brought into the laboratory and weighed 1 h before the com-
mencement of the experiments to allow for acclimatization. All
compounds assayed were prepared as their hydrochloride salts
and dissolved in water for injections BP (British Pharmacopoeia)
before ip injection. Mice (five per dose) were pretreated with test
compound (10 mg kg−1 ip; 0.1 mL per 10 g bodyweight) 30 min
before an injection of apomorphine hydrochloride (3.0 mg kg−1
ip). Climbing behaviour was assessed[22] at 5-min intervals over
25 min, commencing 5 min after apomorphine administration,
using the following scoring system: 0 – no paws on the cage;
1 – one paw on the cage; 2 – two paws on the cage; 3 – three
paws on the cage; 4 – four paws on the cage. The score recorded
for each animal was based on the number of paws on the cage
at a particular time-point, at the moment the animal was first
observed. The mean climbing score (m.c.s.) was calculated by
summation of the total score per mouse for all mice per dose
over the course of the experiment, and dividing that figure by
the number of mice per dose. The results of the experiment were
8-Chloro-11-[4-(4-phenylbutyl)piperazino]-
5H-dibenzo[b,e][1,4]diazepine 5g
A stirred solution of 8-chloro-11-piperazino-5H-dibenzo[b,e]
[1,4]diazepine (27, 250 mg, 0.799 mmol) in dry 1,2-dichloro-
ethane (20 mL) under nitrogen was treated with 4-phenylbutanal
(26, 124 mg, 0.839 mmol)in1,2-dichloroethane(5 mL)followed
by sodium triacetoxyborohydride (237 mg, 1.12 mmol). Stirring
was maintained for 2 h, after which aqueous hydrochloric acid
(2 M, 30 mL) was added to produce a bright yellow-orange
precipitate (gum-like, sparingly soluble in water). The organic
layer was separated and discarded and the aqueous layer washed
with dichloromethane (2 × 25 mL). The aqueous layer and pre-
cipitate were combined, adjusted to pH 14 by the addition of
solid potassium hydroxide, then extracted with dichloromethane
(3 × 50 mL). The combined organic extracts were combined,
washed with water (30 mL), dried over dried magnesium sul-
fate and then concentrated under vacuum. The resulting oil was
purified using flash chromatography (2:3 ethyl acetate/hexane)
and the product recrystallized from dichloromethane/hexane as
bright yellow needles (235 mg, 66%), mp 169–171◦C. (Found:
C 72.7, H 6.6, N 12.6. C27H29ClN4 requires C 72.9, H 6.6,
N 12.6%). νmax (KBr)/cm−1 3280, 2940, 1600, 1562. λmax/nm
(ε/M−1 cm−1) 229 (25700), 261 (16980), 296 (10720). δH
([D6]acetone) 7.10–7.36 (7H, m, H1, H3, H2ꢀꢀꢀ, H3ꢀꢀꢀ, H4ꢀꢀꢀ, H5ꢀꢀꢀ,
H6ꢀꢀꢀ), 7.06 (1H, app d, J 8, H4), 7.00 (1H, app td, J 7.5, 1, H2),
6.95 (1H, d, J 2.5, H9), 6.86 (1H, d, J 8.5, H6), 6.79 (1H, dd, J
8.5, 2.5, H7), 6.46 (1H, s, H5), 3.39 (4H, m, H2ꢀ, H6ꢀ), 2.63 (2H,
t, J 7.5, H4ꢀꢀ), 2.46 (4H, m, H3ꢀ, H5ꢀ), 2.37 (2H, t, J 7, H1ꢀꢀ), 1.67
(2H, m, H3ꢀꢀ), 1.52 (2H, m, H2ꢀꢀ). δC ([D6]acetone) 164.1 (C),
155.1 (C), 143.63 (C), 143.56 (C), 142.9 (C), 132.8 (CH), 131.1
(CH), 129.3 (CH), 129.2 (CH), 128.7 (C), 127.1 (CH), 126.6
(CH), 124.8 (C), 123.5 (2 × CH), 121.4 (CH), 121.2 (CH), 59.0
(CH2), 54.0 (CH2), 48.4 (CH2), 36.5 (CH2), 30.1 (CH2), 27.3
(CH2). m/z (+ESI, 70V) 447 (M[37Cl]H+, 9%), 445 (MH+,
27%), 272 (33), 270 (100), 192 (50), 91 (25).
expressed as a mean value per mouse s.e.m. (standard error of
√
mean calculated by s/ n). The % inhibition climbing value was
calculated using the following formula:
% Inhibition climbing
[m.c.s.(apomorphine) − m.c.s.(drug)]
=
× 100
m.c.s.(apomorphine)
Biological Methods
The experimental protocols for the use of animals were approved
by the Victorian College of Pharmacy, Monash University Ani-
mal Ethics Committee, and are in accordance with theAustralian
Code of Practice for the Care and Use of Animals for Sci-
entific Purposes (Australian Government, National Health and
Medical Research Council, Canberra, 2004) and all government
regulations.
Statistical Analysis
The statistical analysis was carried out by one-way analysis of
variance (ANOVA) followed by Dunnett’s test for pair-wise com-
parison of drug-treated groups and apomorphine-treated control,
using GraphPad Prism 4 (2003), with P < 0.05 being considered
as statistically significant.
Pharmacology Procedures
Receptor Binding Assays
Accessory Publication
Receptor affinities were determined by MDS Pharma Ser-
vices (Taiwan), by the ability of the tested compounds to
displaceselectiveradioligands.Allassayedcompoundsweredis-
solved in dimethylsulfoxide (DMSO) to a stock concentration of
10−2 M, then diluted with assay buffer to a final concentration
of 10−6 M. The assays were carried out using the following:
(i) for dopamine D4.4 receptors: human recombinant (CHO-K1
cells), [3H]spiperone (0.3 nM) as radioligand and haloperidol
(10 µM) as reference compound for non-specific binding; (ii) for
serotonin 5-HT2A receptors: rat cortex, [3H]ketanserin (0.5 nM)
as radioligand, and ketanserin (1 µM) as reference compound
for non-specific binding. The binding results are expressed as
the percentage inhibition of specific binding at a concentration
of 10−6 M for the tested compound and represent the mean of
duplicate tubes the maximum standard error in the mean.
Analytical HPLC conditions used in the present study are
available from the journal’s website.
Acknowledgements
The authors gratefully acknowledge Stuart Thomson for NMR and mass
spectra of compounds described, and Kaitlyn Ky for her contribution to
synthesis and pharmacological testing. Funding for the present work was
provided by the Victorian College of Pharmacy (Monash University).
References
[1] A. Jablensky, N. Sartorius, A. Korten, G. Ernberg, M. Anker,
J. E. Cooper, J. R. Day, Br. J. Psychiatry 1987, 151, 408.
[2] B. Capuano, I. T. Crosby, E. J. Lloyd, Curr. Med. Chem. 2002, 9, 521.
doi:10.2174/0929867024606939

940
B. Capuano et al.
[3] J. M. Alvir, J. A. Lieberman, A. Z. Safferman, J. L. Schwimmer,
[13] M. Feuerstein, H. Doucet, M. Santelli, J. Mol. Catal. Chem. 2006,
256, 75. doi:10.1016/J.MOLCATA.2006.04.059
[14] J. M. Mayer, B. Testa, Helv. Chim. Acta 1982, 65, 1868.
doi:10.1002/HLCA.19820650621
[15] J. W. Tilley, P. Levitan, J. Lind, A. F. Welton, H. J. Crowley,
L. D. Tobias, M. O’Donnell, J. Med. Chem. 1987, 30, 185.
doi:10.1021/JM00384A031
[16] M. C. Toshiyasu, H. S. Hiromu, Y. I. Toshimitsu, US Patent 5144035
1992.
[17] H. G. Morren, R. Denayer, S. Trolin, E. Grivsky, H. Strubbe, R. Linz,
G. Dony, J. Maricq, Ind. Chim. Belg. 1954, 19, 1176.
[18] B. Falconnet, H. Pinhas, Great Britain Patent 1546238 1979.
[19] B. Falconnet, H. Pinhas, US Patent 4127661 1978.
[20] C. J. Kowalski, M. S. Haque, J. Am. Chem. Soc. 1986, 108, 1325.
doi:10.1021/JA00266A049
J. A. Schaaf, N. Engl. J. Med. 1993, 329, 162. doi:10.1056/
NEJM199307153290303
[4] H. A. Amsler, L. Teerenhovi, E. Barth, K. Harjula, P. Vuopio,
Acta Psychiatr. Scand. 1977, 56, 241. doi:10.1111/J.1600-0447.
1977.TB00224.X
[5] B. Capuano, I.T. Crosby, E. J. Lloyd, D.A.Taylor,Aust. J. Chem. 2002,
55, 565. doi:10.1071/CH02093
[6] B. Capuano, I. T. Crosby, E. J. Lloyd, A. Podloucka, D. A. Taylor, Aust.
J. Chem. 2003, 56, 875. doi:10.1071/CH03030
[7] J. Schneider, US Patent 3962248 1976.
[8] P. Seeman, H. H. M. Van Tol, Trends Pharmacol. Sci. 1994, 15, 264.
doi:10.1016/0165-6147(94)90323-9
[9] B. Costall, D. H. Fortune, R. J. Naylor, V. Nohria, Eur. J. Pharmacol.
1980, 66, 207. doi:10.1016/0014-2999(80)90144-2
[10] B. Costall, R. J. Naylor, V. Nohria, Br. J. Pharmacol. 1978, 63, 381P.
[11] B. Costall, R. J. Naylor, V. Nohria, Eur. J. Pharmacol. 1978, 50, 39.
doi:10.1016/0014-2999(78)90251-0
[21] E. F. N. Spon, Dictionary of Organic Compounds 1965,Vol. 4, p. 2673
(Eyre and Spottiswoode Ltd: London).
[22] N. A. Moore, M. S. Axton, Eur. J. Pharmacol. 1990, 178, 195.
doi:10.1016/0014-2999(90)90475-L
[12] B. Costall, R. J. Naylor, V. Nohria, Br. J. Pharmacol. 1980, 68, 175P.