Synthesis and preliminary pharmacological evaluation of 4′-arylalkyl analogues of clozapine. II. Effect of the nature and length of the linker

Article abstract of DOI:10.1071/CH03030

We report the synthesis of a second generation of tricyclic analogues of clozapine, investigating the length and nature of the chain between an ionizable nitrogen atom at physiological pH and the introduced aryl moiety. The chemistry, structural characterization, and pharmacological evaluation of this series of 4′-arylalkyl analogues of clozapine are described. Preliminary findings on the effects on activity of the nature and length of the linker, degree of unsaturation, and type of aryl moiety on blockade of dopamine D₄ and serotonin 5-HT_2A receptors are discussed and animal behavioural data for key compounds presented.

Full text of DOI:10.1071/CH03030

CSIRO PUBLISHING
www.publish.csiro.au/journals/ajc
Aust. J. Chem. 2003, 56, 875–886
Synthesis and Preliminary Pharmacological Evaluation of
4ꢀ-Arylalkyl Analogues of Clozapine.
II.∗ Effect of the Nature and Length of the Linker
Ben Capuano,A,C Ian T. Crosby,A Edward J. Lloyd,A Anna PodlouckaA and David A. TaylorB
A
Department of Medicinal Chemistry, Victorian College of Pharmacy,
Monash University, Parkville, 3052, Australia.
B Department of Pharmaceutical Biology and Pharmacology, Victorian College of Pharmacy,
Monash University, Parkville, 3052, Australia.
C Author to whom correspondence should be addressed (email: ben.capuano@vcp.monash.edu.au).
We report the synthesis of a second generation of tricyclic analogues of clozapine, investigating the length and
nature of the chain between an ionizable nitrogen atom at physiological pH and the introduced aryl moiety. The
chemistry, structural characterization, and pharmacological evaluation of this series of 4ꢀ-arylalkyl analogues of
clozapine are described. Preliminary findings on the effects on activity of the nature and length of the linker, degree
of unsaturation, and type of aryl moiety on blockade of dopamine D4 and serotonin 5-HT2A receptors are discussed
and animal behavioural data for key compounds presented.
Manuscript received: 16 January 2003.
Final version: 19 May 2003.
H
N
Introduction
OH
Cl
Cl
Schizophrenia is a mental disorder characterized by chaotic
jumbling and fragmentation of sensations and thought
processes. This debilitating psychosis, often inaccurately
referred to as a ‘split mind’, is identified by a gross dis-
tortion of reality affecting approximately 1% of the world
population.[1–3] Our current research interests involve the
development of compounds with mixed D4 and 5-HT2A
antagonist activity for the treatment of schizophrenia. The
4ꢀ-arylmethylanaloguesdescribedpreviously,[4] whichinves-
tigated the positional and electronic effects of substituents on
the introduced aryl ring, generally proved to be less potent
N
O
N
N
(2)
N
(1)
H C
3
F
Hybridize
structures
H
N
Cl
N
N
(3)
4'
than clozapine in binding to the selected dopaminergic (D4.4
)
N
)
(n>1)
and serotonergic (5-HT2A) receptors. From these data and our
revised structural model (Scheme 1), conceived from a struc-
tural hybridization of the antipsychotics, haloperidol (1) and
clozapine (2), we embarked on the synthesis and pharmaco-
logical evaluation of second generation clozapine analogues
(3), exploring the length and nature of the link between the
distal nitrogen atom N4ꢀ and the introduced aryl moiety. The
profile of potent D4 and 5-HT2A receptor affinity is hypothe-
sized for the improvement of positive and negative symptoms
of schizophrenia, respectively, and relatively low striatal D2
receptor affinity to diminish EPS (extra pyramidal symptoms)
liability.
(
n
Y
Scheme 1. Structural hybridization of clozapine (1) and haloperidol
(2) yielding a tricyclic template (3).
Results and Discussion
Chemistry
Biochemical data for the N-benzyl analogue of clozapine,[4]
where n = 1, described previously, provided the catalyst to
assess the effect of modifying the length of the saturated
spacer, on the affinity for the D4.4 and 5-HT2A receptors.
∗ Part I: B. Capuano, I. T. Crosby, E. J. Lloyd, D. A. Taylor, Aust. J. Chem. 2002, 55, 565.
© CSIRO 2003
10.1071/CH03030
0004-9425/03/090875

876
B. Capuano et al.
Br
OH
O
S
H
N
CH3
O
+
O
(a)
N
H
(4)
(5)
(13)
(a)
(14)
(b)
H
N
H
N
H
N
H
N
Cl
N
N
N
N
(b)
N
(c)
(16)
H
N
N
(15)
Cl
NH
(7)
O
(6)
(8)
(d) (7)
(d) (7)
Scheme 2. Reagents and conditions: (a) toluene, 85◦C; (b) TiCl4,
anisole, 25 to 55◦C, reflux.
H
N
H
N
H
N
H
N
Cl
Cl
N
N
(a)
N
N
N
N
N
N
(18)
(17)
(9)
(10)
(7) (b)
(7) (b)
H
N
H
N
Scheme 4. Reagents and conditions: (a) N-ethyldiisopropylamine,
methanesulfonyl chloride, dichloromethane, −10◦C; (b) piperazine,
tetrahydrofuran, reflux; (c) 5% Pd/CaSO4/Pb (Lindlar catalyst), quino-
line, H2, methanol; (d) TiCl4, anisole, 25 to 55◦C, reflux.
Cl
Cl
N
N
N
N
N
N
titanium–amine complex of commercially available (E)-1-
cinnamylpiperazine (9) was reacted with (7) to generate the
(E)-arylalkenyl analogue of clozapine (12) as depicted in
Scheme 3. The (Z)-cinnamyl analogue (18) was furnished in
a similar fashion to (12) from the monosubstituted piperazine
1-[(Z)-3-phenyl-2-propenyl]piperazine (16) as illustrated in
Scheme 4. The Z stereochemistry was introduced by hydro-
genation using a Lindlar catalyst of the alkyne precursor (15),
which was generated from treatment of the mesylate (14)
of 3-phenylprop-2-yn-1-ol (13) with piperazine. Reaction of
(15) with the lactam (7) in the presence of titanium tetra-
chloride produced the phenylalkynyl analogue of clozapine
(17). The methodology adopted for phenylalkyl analogues
of clozapine where n >3 made use of commercially avail-
able phenylalkanols (Scheme 5). These alcohols (19a)–(19c)
were suitably oxidized to their respective aldehydes (20a)–
(20c) (62–79%) using pyridinium chlorochromate (PCC),
then reacted under reductive amination conditions with
desmethylclozapine (21) in the presence of sodium triace-
toxyborohydride to yield the desired phenylalkyl homologues
of clozapine (22a)–(22c).
(12)
(11)
Scheme 3. Reagents and conditions: (a) 10% Pd/C, H2, absolute
ethanol; (b) TiCl4, anisole, 25 to 55◦C, reflux.
For n = 2, the monosubstituted piperazine of interest, 1-(2-
phenylethyl)piperazine (6), was prepared by the alkylation of
piperazine (5) with (2-bromoethyl)benzene (4), as presented
in Scheme 2. Subsequent treatment of the titanium–amine
complex[5] of (6) with the tricyclic lactam (7) afforded
the N-phenylethyl analogue (8) as bright yellow prisms.
The synthesis of the homologue corresponding to the N-
phenylpropyl analogue of clozapine (11) (n = 3) is outlined
in Scheme 3. The intermediate 1-(3-phenylpropyl)piperazine
(10) was obtained by hydrogenation of commercially avail-
able (E)-1-cinnamylpiperazine (9). Subsequent treatment
with titanium tetrachloride followed by the lactam (7)
afforded (11) in excellent yield (87%). Our efforts were also
focussed on incorporating unsaturation, in the form of dou-
ble (E and Z) and triple bonds, into the link between N4ꢀ
and the introduced aryl moiety, and examining the effect of
these conformational restrictions on biological activity. The
The benzyloxyethyl (25a) and benzyloxypropyl (25b)
analogues of clozapine were synthesized to investigate the
effect of inserting an oxygen atom in the linker (Scheme 6),

4ꢀ-Arylalkyl Analogues of Clozapine
877
OH
OH
OH
O
O
O
O
(a)
(CH2)n
O
(26)
(27)
H
N
(19a): n = 5
(19b): n = 7
(19c): n = 10
(b)
Cl
H
N
N
O
(a)
(c)
(21)
N
Cl
(29)
O
O
N
O
N
O
N
(b)
(28)
(CH2)nϪ1
H
O
N
N
(22a): n = 5
(22b): n = 7
(22c): n = 10
(
)
n
Cl
Scheme 7. Reagents and conditions: (a) LiAlH4, anhydrous ether; (b)
PCC, SiO2, dichloromethane; (c) NaBH(OAc)3, 1,2-dichloroethane.
N
N
(20a): n = 5
(20b): n = 7
(20c): n = 10
(21)
R
HN
NH2
Scheme 5. Reagents and conditions: (a) pyridinium chlorochromate
(PCC), SiO2, dichloromethane; (b) NaBH(OAc)3, 1,2-dichloroethane.
CO2H
N
H
H
N
(30a): R = H
Br
(
)
n
(30b): R = OCH3
H
N
O
N
H
(a)
N
(a)
+
(
)
n
O
N
H
Cl
R
N
(5)
N
(b)
(24a): n = 2
(24b): n = 3
(23a): n = 2
(23b): n = 3
O
(21)
R
N
H
N
H
N
(31a): R = H
(32a): R = H
Cl
(31b): R = OCH3
(32b): R = OCH3
N
N
H
N
(b) (n = 2)
(c) (n = 3)
N
Scheme 8. Reagents and conditions: (a) NaOCl(aq.), water/toluene,
pH 9; (b) NaBH(OAc)3, 1,2-dichloroethane.
(
)
n
O
(25a): n = 2
(25b): n = 3
The benzodioxole and indole ring systems were investi-
gated as alternatives to the phenyl moiety for inclusion into
the structure of clozapine at the N4ꢀ position using a suit-
able linker. We were particularly interested in the synthesis
of the benzo[1,3]dioxol-5-ylethyl ((29), Scheme 7) and 5-
methoxyindol-3-ylethyl ((32b), Scheme 8) analogues (n = 2)
because structurally they incorporate the protected forms of
the neurotransmitters dopamine and serotonin, respectively.
The benzo[1,3]dioxol-5-ylethyl analogue of clozapine was
synthesized according to the method outlined in Scheme 7.
The aldehyde (28), obtained from its commercially avail-
able corresponding acid (26) by lithium aluminium hydride
reduction to the alcohol (27)[6] followed by PCC oxidation,[7]
underwent reductive amination with desmethylclozapine (21)
in the presence of sodium triacetoxyborohydride affording
the target amidine (29) in 41% yield.
The syntheses of indol-3-ylethyl analogues (32a) and
(32b) followed a similar pathway to that of (29), involv-
ing desmethylclozapine (21) and the corresponding indole-
3-acetaldehydes (31a) and (31b), and are outlined in
Scheme 8. Synthesis of indole-3-acetaldehyde (31a)[8] from
l-tryptophan (30a) was effected in 44% yield. Similar
conversion of 5-methoxy-dl-tryptophan (30b) afforded the
Scheme 6. Reagents and conditions: (a) toluene, 85◦C; (b) tricyclic
lactam (7), TiCl4, anisole, 25 to 55◦C, reflux; (c) tricyclic lactam (7),
phosphorus pentachloride, dichloromethane.
particularly in relation to improving aqueous solubility com-
pared with the saturated hydrocarbon linker. We had previ-
ously observed that hydrochloride salts of compounds with
a hydrocarbon linker were somewhat difficult to dissolve for
assay purposes and decided that inclusion of a heteroatom
with extensive hydrogen-bond acceptor properties would
be one way of inherently improving relative aqueous solu-
bility. The intermediate monosubstituted piperazines (24a)
and (24b) were prepared by alkylation of piperazine with
the appropriate benzyl bromoalkyl ether (23a) and (23b).
Compound (25a) was furnished from reaction of (7) with
(24a) in the presence of titanium tetrachloride, whilst (25b)
was obtained by treatment of (24b) with the imino chloride
intermediate obtained by reaction of (7) with phosphorus
pentachloride. Both target compounds (25a) and (25b) were
synthesized in reasonable yields (36 and 34%, respectively).

878
B. Capuano et al.
N
H
H
N
Table 1. Preliminary binding studiesA
H
N
Cl
Cl
(a)
N
N
Cl
N
N
N
N
N
N
N
R1
R2
(
)
n
OH
OH
O
O
H2C
H2C
(29)
(33)
R1 =
R2 =
Compound
n
Percentage inhibition (% I) at 10−6
M
B
B
C
D4.4
5-HT2A
D2
[3H]spiperone
OCH3
(32b)
OH
[3H]spiperone
[3H]ketanserin
H2C
H2C
(34)
Clozapine
(N-benzyl)
(8)
(11)
(22a)
54
79
47
40
47
48
20
90
50
93
87
79
47
31
76
81
86
83
81
3
2
4
5
6
1
2
3
5
7
N
H
N
H
Scheme 9. Reagents and conditions: (a) boron tribromide,
(22b)
(22c)
51 14
41 20
dichloromethane.
10
H
N
A All compounds were tested as their hydrochloride salts.
B Determined in duplicate by PANLABS, Taiwan.
C Determined in duplicate at the Victorian College of Pharmacy, Melbourne.
H
N
Cl
N
Cl
(a)
N
N
O
N
The N-2-adamantyl analogue (38) was synthesized under
reductive amination conditions using desmethylclozapine
(21) and 2-adamantanone (37) (Scheme 10). This lipophilic
moiety was selected to investigate the effect of a bulky,
non-aromatic group directly anchored to the distal nitrogen
atom, N4ꢀ.
(36)
F
N
Cl
(21)
N
(35)
H
F
(b)
O
O
H
N
Cl
N
(37)
Pharmacological Results and Discussion
In Vitro Receptor Binding Studies
N
(38)
N
The synthesized compounds were evaluated in vitro in a
series of preliminary receptor binding screens. The com-
pounds were assayed as their hydrochloride salts at a final
concentration of 10−6 M. Their affinities for cloned human
dopamine D4.4 receptors,[9] rat cortical serotonin 5-HT2A
receptors[10–12] (both of which represent the primary recep-
tors of interest), and rat striatal dopamine D2 receptors[9]
were assessed by measuring the displacement of the desig-
nated radioligand (percentage inhibition, % I). The D4.4 and
5-HT2A binding data for compounds presented in Tables 1
and2wereperformedbyPANLABS, TaiwanLtd, whilstthose
presented in Table 3 were performed in-house. There was a
discrepancy between the D4.4 receptor binding data deter-
mined for clozapine by PANLABS (54% I at 10−6 M) and
dataobtainedin-house(93%Iat10−6 M). Thisdifferencewas
not considered to be a factor as compounds were only com-
pared within their tabulated groups to assess relative affinities
in preliminary assays and not across different analyses.
Binding affinities for chain extended phenylalkyl ana-
logues of clozapine are presented in Table 1. Data for
the compound corresponding to the N-benzyl analogue of
clozapine (n = 1) were also included for comparison across
the series. Its inclusion provided a firmer basis for structure–
activity relationships concerning the length of the linker
between the distal nitrogen atom N4ꢀ, and the introduced
Scheme 10. Reagents and conditions: (a) sodium iodide, triethyl-
amine, 1,2-dimethoxyethane; (b) NaBH(OAc)3, 1,2-dichloroethane.
desired 5-methoxyindole-3-acetaldehyde (31b). Indole-3-
acetaldehydes (31a) and (31b) were systematically treated
with desmethylclozapine (21) under reducing conditions giv-
ing indol-3-ylethyl analogues of clozapine (32a) and (32b).
The benzo[1,3]dioxolylethyl (29) and 5-methoxyindol-3-
ylethyl (32b) analogues were further reacted with boron
tribromide to afford their catecholethyl (33) and indololethyl
(34) analogues (Scheme 9), respectively. These deprotected
analogues were of particular interest because they essentially
incorporate the structures of the neurotransmitters dopamine
and serotonin, respectively.
The effects of incorporating some of the structural fea-
tures of haloperidol into the molecule of clozapine were
investigated. We envisaged the hybrid molecule possessing
a 4ꢀ-fluorobutyrophenone of haloperidol directly linked
to the distal nitrogen atom, N4ꢀ, of clozapine. Alkylation
of desmethylclozapine (21) with 4-chloro-4ꢀ-fluorobutyro-
phenone (35) in the presence of sodium iodide furnished the
hybrid (36) as outlined in Scheme 10.

4ꢀ-Arylalkyl Analogues of Clozapine
879
Table 2. Preliminary binding studiesA
Table 3. Preliminary binding studiesA
H
N
H
N
Cl
Cl
N
N
N
N
N
R
N
R
Compound
R
Percentage inhibition (% I) at 10−6
M
Compound
R
Percentage inhibition (% I) at 10−6
M
B
B
B
D4.4
[3H]spiperone
5-HT2A
[3H]ketanserin
D2
B
B
C
D4.4
5-HT2A
D2
[3H]spiperone
[3H]spiperone [3H]ketanserin [3H]spiperone
Clozapine
(29)
CH3
93
41
3
1
94
84
1
9
76
3
Clozapine
(12)
CH3
54
52
90
80
76
77
3
2
O
CH2
CH2
CH2
57 17
34 21
O
H2C
(18)
42
70
65 16
(32a)
33 13
81
6
N
H
(17)
40
59
36
87
60 13
n.d.D
CH2
CH2
H3CO
CH2
(25a)
(32b)
(33)
27 11
83
92
2
5
30
42
2
5
N
H
O
O
CH2
(25b)
58
82
n.d.
HO
CH2
CH2
42
9
HO
HO
A All compounds were tested as their hydrochloride salts.
B Determined in duplicate by PANLABS, Taiwan.
C Determined in duplicate at the Victorian College of Pharmacy, Melbourne.
D Not determined.
(34)
24 15
59
5
34
6
N
H
O
(36)
(38)
CH2 61
4
5
90
39
5
6
76 12
F
benzene ring. The chain-extended analogues correspond-
ing to n = 2 (8), 3 (11), and 5 (22a) showed comparable
affinities to clozapine for both D4.4 and 5-HT2A receptors.
The clozapine analogue (22b) where n = 7 displayed D4.4
affinity comparable to clozapine but diminished affinity for 5-
HT2A receptors. Further chain extension where n = 10 (22c)
resulted in significantly decreased binding at the D4.4 and
5-HT2A receptors.
CH
13
49
5
A All compounds were tested as their hydrochloride salts.
B Determined in duplicate at the Victorian College of Pharmacy, Melbourne.
tests showed improved aqueous solubility for the hydrochlo-
ride salts of (25a) and (25b) compared with the hydrochloride
salt of (22a), which contained the saturated hydrocarbon
linker of equal length.
The (E) and (Z)-arylalkenyl analogues (12) and (18),
respectively, andthearylalkynylcompound(17)wereassayed
to examine the effect of incorporating unsaturation and also
conformational restriction into the linker between the nitro-
gen atom, N4ꢀ, and the introduced aromatic ring. The results
are presented in Table 2. Inclusion of the (E)-phenylpropenyl
moiety (12) produced affinity comparable to that of clozapine
for the D4.4 and 5-HT2A receptors. The (Z)-phenylpropenyl
analogue (18) displayed promising 5-HT2A affinity with
somewhat diminished activity at the D4.4 receptor. Incorpo-
ration of a phenylalkynyl group at the N4ꢀ position exhibited
reduced affinity at all receptor subtypes examined. The data
demonstrate that a degree of unsaturation (alkene) in test
compounds can be tolerated by the receptors of interest. The
above-mentioned analogues showed favourable D2 recep-
tor affinity comparable to the parent compound, clozapine.
Incorporation of oxygen into the linker (25a) and (25b)
afforded compounds with very promising binding profiles
that compared favourably to clozapine and represented the
best candidates for in vivo evaluation. Preliminary solubility
All compounds tabulated in Table 3, except for the indolo-
lethyl analogue (34) (59% I) and the adamantyl analogue (38)
(58% I), displayed affinity for the 5-HT2A receptor compara-
ble to clozapine (94% I). Of particular note were the catecho-
lethyl (33) and butyrophenone (36) analogues exhibiting 92
and 90% I, respectively. In contrast, all compounds displayed
relatively low affinity for the D4.4 receptor with compound
(36) displaying a maximum value of 61% I (cf. clozapine,
93% I). The catecholethyl analogue (33) showed diminished
affinity for the D4.4 receptor. Inclusion of the butyrophenone
portion of haloperidol into the structure of clozapine (36)
produced D2 affinity comparable with clozapine. The remain-
ing compounds exhibited lower affinity for the D2 receptor
compared with clozapine. Preliminary investigation of steric
factors was undertaken by increasing bulk at the N4ꢀ atom
with an adamantyl moiety (38). The resultant compound dis-
played poor activity at both D4.4 and 5-HT2A receptors (13

880
B. Capuano et al.
Table 4. Antagonism of apomorphine-induced climbing in mice
the aryl system, produced an excellent profile. The incorpo-
ration of an oxygen atom into the linker, as demonstrated
by (25a) and (25b), also produced favourable binding pro-
files compared with clozapine. The introduction of other aryl
moieties (benzodioxoles, indoles, and catechols) produced
compounds with significantly reduced receptor affinity com-
pared with clozapine. Steric bulk directly attached to the
distal nitrogen atom N4ꢀ associated with analogue (38) (N-
adamantyl) was not well tolerated by the D4.4 receptor
compared with clozapine. In vivo analysis of promising
candidates showed compound (12) effectively inhibiting
apomorphine-induced climbing in mice comparable to cloza-
pine. Compounds (8), (25a), and (25b), although displaying
very favourable binding profiles, failed to significantly antag-
onize apomorphine-induced climbing in mice. It should be
noted that an absence of effect in the apomorphine model
does not necessarily preclude antipsychotic activity given the
multifactorial nature of the neurotransmitters implicated in
the etiology of schizophrenia. This may be related to pharma-
cokinetic and pharmacodynamic factors and requires further
behavioural investigation. With respect to chain length, it
appears from the preliminary results of binding at D4.4
and 5-HT2A that the optimal length is 3–5 atoms, which
gives valuable insights into the spatial requirements in the
region of clozapine’s distal nitrogen atom. Thus compound
(12), for example, could be used as the basis for further
structural modification and pharmacological evaluation with
the aim of more precisely defining the structural require-
ments for antipsychotic activity devoid of clinically limiting
side-effects.
Compound
Climbing indexA
% Inhibition of climbing
Apomorphine
Vehicle
Clozapine
(8)
(12)
(25a)
18.2 1.5
0.4 0.4
–
–
30
20
50
0
12.8 1.3B
14.5 2.0
9.1 2.2B
18.8 0.5
15.6 3.9
(25b)
14
A All compounds were tested as their hydrochloride salts at a dose of
10 mg kg−1 i.p. Values represent the mean SEM climbing index.
B Compounds with statistically significant (P < 0.05) activity.
and 39% I, respectively) indicating receptor intolerance for
bulky substituents at the distal N4ꢀ position. Compounds were
selected for further investigation in a preliminary in vivo
assay predictive of antipsychotic efficacy using the criterion
that the % I (compound) > [% I (clozapine) − 10%] for both
D4.4 and 5-HT2A receptors. Compounds selected on this basis
include the phenylalkyl (8) (n = 2) (E)-phenylpropenyl (12)
and benzyloxyalkyl analogues (25a,b).
In Vivo Behavioural Studies
Promising compounds from the in vitro assays were inves-
tigated in vivo for their ability to antagonize apomorphine-
induced climbing in mice; a behavioural model predictive
of mesolimbic, dopaminergic activity and potential anti-
psychotic efficacy.[13–16] The mice were pretreated with
clozapine (10 mg kg−1 i.p.) and test compounds (10 mg kg−1
i.p.), as their hydrochloride salts, 30 min prior to an injec-
tion of apomorphine hydrochloride (3.0 mg kg−1 i.p.) and
their climbing behaviour assessed. The results are displayed
in Table 4. Clozapine effectively diminished apomorphine-
induced climbing in mice at 10 mg kg−1 i.p., displaying
30% inhibition of climbing. Disappointingly, the phenylethyl
(8), benzyloxyethyl (25a), and benzyloxypropyl (25b) ana-
logues of clozapine, although exhibiting some anti-climbing
activity at higher doses, failed to significantly antagonize
apomorphine-induced climbing at the administered dose of
10 mg kg−1 i.p. The (E)-phenylpropenyl analogue of clozap-
ine (12) significantly antagonized the apomorphine-induced
climbing (50% inhibition) and proved to be the first com-
pound of the series assayed to display any significant anti-
climbing activity, exhibiting an appreciably greater potency
compared with clozapine.
Experimental
Chemistry
Melting points were determined on a Reichert Micro-melting point
apparatus and are uncorrected. Infrared (IR) spectra were recorded on
a Hitachi 270-30 IR spectrophotometer as KBr discs unless indicated
otherwise. UV-vis spectra were recorded as ethanolic solutions on a
Pharmacia Biotech Ultraspec 2000 UV-vis spectrophotometer utilis-
ing Swift II software. Wavelengths of maximum absorbance and points
of inflexions (denoted by inf ) are quoted with accompanying molar
absorptivity data (log10 ε). 1H and 13C NMR spectra were recorded
at 300 and 75.4 MHz, respectively, using a Bruker Avance DPX 300
spectrometer equipped with a Silicon Graphics work station. Chemical
shifts for all 1H spectra are reported in parts per million (ppm), using
tetramethylsilane as the internal reference. Proton assignments were
based upon coupling constants and 2D-homonuclear (1H/1H) correla-
tion spectroscopy. Chemical shifts for all 13C spectra are reported in
ppm, using the solvent chemical shift as the reference.[17] J-Modulated
Spin-Echo experiments (JMOD) were routinely performed. Fast atom
bombardment (FAB) mass spectra were determined using a JEOL JMS-
DX300 Mass Spectrometer. The thioglycerol/glycerol matrix was used
for samples analyzed by FAB. Electrospray ionization (ESI) mass spec-
tra were determined in positive ion mode using a Micromass Platform
II Mass Spectrometer. High-resolution mass spectra were determined
using a Bruker BioApex II FTICR Mass Spectrometer. In reporting
spectroscopic data, the following abbreviations have been used: s, sin-
glet; d, doublet; t, triplet; q, quartet; p, pentet; m, multiplet; br, broad;
app, apparent. Analytical reverse-phase high-performance liquid chro-
matography (HPLC) was performed on a Waters HPLC system fitted
with a Nova-Pak HR C18 column (6 µm, 60 Å, 8 mm × 100 mm) using a
binary solvent system; solvent A: 0.1% trifluoroacetate (TFA)/H2O; sol-
vent B: 0.1% TFA/90% CH3CN/H2O. Analyses were conducted using
Conclusions
A series of 4ꢀ-arylalkyl analogues of clozapine were synthe-
sized based upon the structural hybridization of clozapine and
haloperidol. Preliminary in vitro binding data revealed a col-
lection of analogues that exhibited desirable affinity for D4.4
and 5-HT2A receptors comparable to clozapine. Compounds
exploring the effect of chain length corresponding to 2 methy-
lene units (8), linking the ionizable nitrogen atom N4ꢀ and the
introduced benzene ring, showed promising data. Similarly,
incorporation of the (E)-phenylpropenyl moiety (12), pos-
sessing a constrained three-carbon spacer between N4ꢀ and

4ꢀ-Arylalkyl Analogues of Clozapine
881
isocratic (60% A/40% B, flow rate 1.5 mL min−1) and gradient (100%
A to 100% B over 30 min, flow rate 1.5 mL min−1) elution modes.
Thin-layer chromatography (TLC) was carried out on silica gel 60 F254
pre-coated plates (0.25 mm, Merck, ART 5554). Preparative TLC was
performed on glass plates (20 cm × 20 cm × 2 mm, Merck, ART 5717).
Flash chromatography[18] was carried out routinely using Merck Sil-
ica gel 60, 230–400 mesh ASTM. Elemental analyses were carried out
on target compounds dried under vacuum over phosphorus pentoxide
at 30◦C for 24 h, by Chemical & Micro Analytical Services Pty Ltd,
Melbourne, or Microanalytical Service, Chemistry Department, Uni-
versity of Queensland, Brisbane. The results are within 0.4% of the
theoretical values for the indicated formula. All solvents used were
redistilled prior to use. Tetrahydrofuran was distilled over sodium
metal/benzophenone ketyl under nitrogen immediately prior to use.
Dry dichloromethane and 1,2-dichloroethane were obtained by distilla-
tion over phosphorus pentoxide followed by storage over 3A molecular
sieves. Dry ethanol and methanol were distilled from their respective
magnesium alkanolates and stored over type 4A and 3A molecular
sieves, respectively.
organic fractions were combined, washed with water (2 × 30 mL), dried
over anhydrous sodium sulfate, and then evaporated to dryness. The
resulting oily residue was purified using flash chromatography (ethyl
acetate/hexane; 2 : 1) and the major product was evaporated to dryness to
afford (8) as a yellow solid, which recrystallized from methanol as bright
yellow prisms (225 mg, 88%), mp 95◦C (softens), 152–154◦C (melts)
(Found: C 69.6, H 6.4, N 12.3%. C25H25ClN4·CH3OH requires C
69.6, H 6.5, N 12.5%) (Found: C 71.6, H 5.8, N 13.1%. C25H25ClN4
(dichloromethane/hexane) requires C 72.0, H 6.0, N 13.4%). νmax
(KBr)/cm−1 3300, 1604, 1562. λmax (log10 ε)/nm 227 (4.40), 260 (4.21),
297 (4.07). δH (300 MHz; CD2Cl2) 7.35−7.14 (7 H, m, H1, H3, H2ꢀꢀꢀ,
H3ꢀꢀꢀ, H4ꢀꢀꢀ, H5ꢀꢀꢀ, H6ꢀꢀꢀ), 7.04 (1 H, dd, J 7.5, 1, H2), 7.00 (1 H, d,
J 2.5, H9), 6.85 (1 H, dd, J 8, 1, H4), 6.81 (1 H, dd, J 8.5, 2.5, H7),
6.64 (1 H, d, J 8.5, H6), 4.98 (1 H, s, H5), 3.44 (4 H, m, H2ꢀ, H6ꢀ),
2.81 (2 H, m, H2ꢀꢀ), 2.64 (2 H, m, H1ꢀꢀ), 2.59 (4 H, m, H3ꢀ, H5ꢀ). δC
(75 MHz; [D6]acetone) 164.1, 155.1, 143.5, 143.0, 141.7, 132.8, 131.0,
129.7, 129.2, 128.6, 127.0, 126.8, 124.7, 123.5, 123.4, 121.4, 121.2,
61.1, 53.8, 48.3, 34.3. FAB mass spectrum m/z 417.2.
8-Chloro-11-[4-(3-phenylpropyl)piperazino]-
1-(2-Phenylethyl)piperazine (6)
5H-dibenzo[b,e][1,4]diazepine (11)
To a solution of (2-bromoethyl)benzene (15.0 g, 81.1 mmol) in toluene
(300 mL) was added piperazine (27.9 g, 324 mmol). The solution was
heated at 85◦C for 2 h after which it was cooled, filtered, and the
filtrate evaporated to dryness under vacuum. The resulting residue
was then partitioned between aqueous hydrochloric acid (2 M, 50 mL)
and dichloromethane (50 mL) and the aqueous phase washed with
dichloromethane (2 × 50 mL). The aqueous phase was adjusted to pH 14
with solid sodium hydroxide, the resulting oil removed, and the aqueous
phase was extracted with dichloromethane (2 × 100 mL). The oil and
organic fractions were combined, washed with water (2 × 50 mL), brine
(50 mL), dried over anhydrous sodium sulfate, filtered, and then con-
centrated under vacuum to yield a pale yellow oil. Vacuum distillation
afforded the product (10.7 g, 69%) as a colourless liquid, bp 110–111◦C
(0.5 mmHg) [lit.[19] bp 92–96◦C (0.15 mmHg)]. δH (300 MHz; CDCl3)
7.31–7.23 (2 H, m, H3ꢀꢀ, H5ꢀꢀ), 7.22–7.14 (3 H, m, H2ꢀꢀ, H4ꢀꢀ, H6ꢀꢀ), 2.91
(4 H, m, H3, H5), 2.80 (2 H, m, H2ꢀ), 2.58 (2 H, m, H1ꢀ), 2.48 (4 H, m,
H2, H6), 1.38 (1 H, s, H4). δC (75 MHz; CDCl3) 140.4, 128.6, 128.3,
125.9, 61.1, 54.6, 46.1, 33.4. ESI mass spectrum m/z 191.2.
1-(3-Phenylpropyl)piperazine (626 mg, 3.07 mmol) in anhydrous ani-
sole (5 mL) was treated with a solution of titanium tetrachlo-
ride in toluene (1.0 M, 0.67 mL, 0.67 mmol), followed by a solu-
tion of 8-chloro-10,11-dihydro-5H-dibenzo[b,e][1,4]diazepin-11-one
(7)(0.150 mg, 0.613 mmol)indryanisole(10 mL)andworkedupasdes-
cribed in the preparation of (8). The resulting residue was purified using
flash chromatography (ethyl acetate:hexane; 1 : 1) and product (11)
recrystallized from methanol/water as bright yellow prisms (229 mg,
87%), mp 65◦C (softens), 103◦C (melts) (Found: C 70.3, H 6.7, N
12.1%. C26H27ClN4·CH3OH requires C 70.0, H 6.7, N 12.1%). νmax
(KBr)/cm−1 3288, 1602, 1562. λmax (log10 ε)/nm 229 (4.38), 261 (4.20),
296 (4.00). δH (300 MHz; [D3]acetonitrile) 7.33 (1 H, app td, J 7.5, 1.5,
H3), 7.29–7.13 (6 H, m, H1, H2ꢀꢀꢀ, H3ꢀꢀꢀ, H4ꢀꢀꢀ, H5ꢀꢀꢀ, H6ꢀꢀꢀ), 7.02 (1 H,
app t, J 7.5, 1, H2), 6.98 (1 H, dd J 7.5, 1, H4), 6.94 (1 H, d, J 2.5, H9),
6.82 (1 H, dd, J 8.5, 2.5, H7), 6.77 (1 H, d, J 8.5, H6), 5.83 (1 H, s, H5),
3.36 (4 H, m, H2ꢀ, H6ꢀ), 2.63 (1 H, t, J 7.5, H3ꢀꢀ), 2.44 (4 H, m, H3ꢀ,
H5ꢀ), 2.34 (1 H, t, J 7, H1ꢀꢀ), 1.76 (1 H, app p, J 7.5, H2ꢀꢀ). δC (75 MHz;
[D3]acetonitrile) 164.2, 154.7, 143.7, 143.4, 142.7, 133.1, 131.2, 129.5,
129.3, 129.0, 126.9, 126.7, 124.5, 123.9, 123.7, 121.5, 121.2, 58.5, 53.9,
48.3, 34.2, 29.6. FAB mass spectrum m/z 431.3.
1-(3-Phenylpropyl)piperazine (10)
A mixture of (E)-1-cinnamylpiperazine (5.00 g, 24.7 mmol), palladium-
on-carbon (10%, 300 mg), and absolute ethanol (30 mL) was hydro-
genated at 60 psi for 30 min at ambient temperature. The catalyst was
removed by filtration through a celite pad and the filtrate was concen-
trated under vacuum. Vacuum distillation afforded the title compound
(10) (3.50 g, 69%) as a colourless liquid, bp 108–110◦C (0.1 mmHg)
[lit.[20] bp 122–128◦C (0.5 mmHg)]. δH (300 MHz; CDCl3) 7.27–7.19
(2 H, m, H3ꢀꢀ, H5ꢀꢀ), 7.17–7.09 (3 H, m, H2ꢀꢀ, H4ꢀꢀ, H6ꢀꢀ), 2.87 (4 H, m,
H3, H5), 2.62 (2 H, t, J 7.5, H3ꢀ), 2.38 (4 H, m, H2, H6), 2.33 (2 H, t,
J 7.5, H1ꢀ), 1.80 (2 H, app p, J 7.5, H2ꢀ), 1.78 (1 H, s, H4). δC (75 MHz;
CDCl3) 142.2, 128.4, 128.3, 125.8, 58.7, 54.6, 46.2, 33.7, 28.4. ESI
mass spectrum m/z 205.2.
8-Chloro-11-{4-[(E)-3-phenyl-2-propenyl]piperazino}-
5H-dibenzo[b,e][1,4]diazepine (12)
(E)-1-Cinnamylpiperazine (1.24 g, 6.13 mmol) in anhydrous anisole
(10 mL) was treated with
a solution of titanium tetrachloride
in toluene (1.0 M, 1.35 mL, 1.35 mmol), followed by a solution
of 8-chloro-10,11-dihydro-5H-dibenzo[b,e][1,4]diazepin-11-one (7)
(300 mg, 1.23 mmol) in dry anisole (20 mL) and worked up as described
in the preparation of (8). The resulting residue was purified using flash
chromatography(ethylacetate/hexane;7 : 3)andtheproduct(12)recrys-
tallized from dichloromethane/methanol as yellow prisms (462 mg,
88%), mp 92◦C (softens), 147–149◦C (melts) (Found: C 70.2, H 6.2, N
12.1%. C26H25ClN4·CH3OH requires C 70.3, H 6.3, N, 12.2%). νmax
(KBr)/cm−1 3372, 1602, 1560. λmax (log10 ε)/nm 236 (4.37), 250 (4.53),
294 (4.08). δH (300 MHz; [D6]acetone) 7.44 (2 H, m, H2ꢀꢀꢀ, H6ꢀꢀꢀ), 7.36–
7.26 (4 H, m, H1, H3, H3ꢀꢀꢀ, H5ꢀꢀꢀ), 7.22 (1 H, m, H4ꢀꢀꢀ), 7.06 (1 H, dd, J
8, 1, H4), 7.02 (1 H, app td, J 8, 1, H2), 6.95 (1 H, d, J 2.5, H9), 6.88
(1 H, d, J 8.5, H6), 6.81 (1 H, dd, J 8.5, 2.5, H7), 6.59 (br d, J 16, 1H,
H3ꢀꢀ), 6.52 (1 H, s, H5), 6.31 (1 H, dt, J 16, 6.5, H2ꢀꢀ), 3.43 (4 H, m,
H2ꢀ, H6ꢀ), 3.18 (2 H, dd, J 6.5, 1 Hz, H1ꢀꢀ), 2.56 (4 H, m, H3ꢀ, H5ꢀ). δC
(75 MHz; [D6]acetone) 164.1, 155.1, 143.5, 143.0, 138.2, 133.5, 132.9,
131.1, 129.5, 128.6, 128.3, 128.0, 127.3, 127.1, 124.7, 123.54, 123.45,
121.4, 121.2, 61.6, 53.8, 48.4. FAB mass spectrum m/z 429.2.
8-Chloro-11-[4-(2-phenylethyl)piperazino]-
5H-dibenzo[b,e][1,4]diazepine (8)
To a solution of 1-(2-phenylethyl)piperazine (0.583 g, 3.07 mmol) in
anhydrous anisole (5 mL) under nitrogen was added a solution of tita-
nium tetrachloride in toluene (1.0 M, 0.67 mL, 0.67 mmol). The mixture
was warmed to 50–55◦C and a hot solution of 8-chloro-10,11-dihydro-
5H-dibenzo[b,e][1,4]diazepin-11-one (7) (150 mg, 0.613 mmol) in dry
anisole (10 mL) was then added. The mixture was heated at reflux for
4 h after which time it was cooled and then evaporated to dryness
under vacuum. The brown coloured residue was partitioned between
ethyl acetate (50 mL) and aqueous sodium hydroxide (2 M, 30 mL),
the mixture was filtered under vacuum, and the residue was washed
with ethyl acetate (20 mL). The organic layer was separated and the
aqueous phase was extracted with ethyl acetate (2 × 50 mL). The
1-(3-Phenylprop-2-yn-1-yl)piperazine (15)
Methanesulfonyl chloride (4.42 g, 38.6 mmol) was added dropwise
using a syringe to a stirred solution of 3-phenylprop-2-yn-1-ol

882
B. Capuano et al.
(3.00 g, 22.7 mmol) and triethylamine (4.59 g, 45.4 mmol) in dry
dichloromethane (25 mL) at −50◦C. The reaction was warmed to 0◦C
and stirred at this temperature for 1 h. The reaction mixture was trans-
ferred to a separatory funnel and washed with water (2 × 30 mL), dried
over dried magnesium sulfate, and then evaporated to dryness afford-
ing a yellow liquid. The crude mesylate was dissolved in anhydrous
tetrahydrofuran (25 mL) and piperazine was added (7.82 g, 90.8 mmol).
The mixture was stirred and heated at reflux for 24 h then cooled.
The solvent was removed under vacuum and the residue partitioned
between aqueous hydrochloric acid (2 M, 50 mL) and dichloromethane
(50 mL) and the organic layer separated. The aqueous layer was washed
with dichloromethane (50 mL), adjusted to pH 14 by the addition of
solid potassium hydroxide, and then extracted with dichloromethane
(3 × 50 mL). The organic fractions were combined, washed with water
(2 × 30 mL), dried over dried magnesium sulfate, and then concen-
trated under vacuum. The resulting oil was distilled affording the
product (15)[21] (2.49 g, 55%) as a colourless liquid, bp 125–130◦C
(0.05 mmHg) that crystallized on standing. δH (300 MHz; CDCl3) 7.46–
7.38 (2 H, m, H2ꢀꢀ, H6ꢀꢀ), 7.30–7.22 (3 H, m, H3ꢀꢀ, H4ꢀꢀ, H5ꢀꢀ), 3.47 (2 H,
s, H1ꢀ), 2.91 (4 H, m, H3, H5), 2.58 (4 H, m, H2, H6), 1.78 (1 H, s, H4).
δC (75 MHz; CDCl3) 131.6, 128.1, 127.9, 123.1, 85.2, 84.5, 53.2, 48.2,
45.9. ESI mass spectrum m/z 201.1.
of 8-chloro-10,11-dihydro-5H-dibenzo[b,e][1,4]diazepin-11-one (7)
(150 mg, 0.613 mmol) in dry anisole (10 mL) and worked up as
described in the preparation of (8). The residue was purified using
flash chromatography (ethyl acetate/hexane; 1 : 1) and the product (17)
was recrystallized from dichloromethane/hexane as pale yellow micro-
needles (115 mg, 44%), mp 139.5–141◦C (Found: C 73.2, H 5.5, N
13.1%. C26H23ClN4 requires C 73.1, H 5.4, N 13.1%). νmax (KBr)/cm−1
3364, 1600, 1560. λmax (log10 ε)/nm 234 (4.59), 239 (4.60), 251 (4.51),
297 (4.04). δH (300 MHz; [D6]acetone) 7.49–7.42 (2 H, m, H2ꢀꢀꢀ, H6ꢀꢀꢀ),
7.37–7.28 (5 H, m, H1, H3, H3ꢀꢀꢀ, H4ꢀꢀꢀ, H5ꢀꢀꢀ), 7.08 (1 H, br d, J 8,
H4), 7.03 (1 H, m, H2), 6.96 (1 H, d, J 2.5 Hz, H9), 6.89 (1 H, d, J 8.5,
H6), 6.82 (1 H, dd, J 8.5, 2.5 Hz, H7), 6.56 (1 H, s, H5), 3.58 (2 H, s,
H1ꢀꢀ), 3.46 (4 H, m, H2ꢀ, H6ꢀ), 2.71 (4 H, m, H3ꢀ, H5ꢀ). δC (75 MHz;
[D6]acetone) 164.0, 155.0, 143.4, 142.9, 132.9, 132.5, 131.0, 129.4,
129.1, 128.6, 127.0, 124.6, 124.2, 123.54, 123.48, 121.4, 121.2, 85.9,
85.8, 52.4, 48.2, 48.0. ESI mass spectrum m/z 427.4.
General Procedure for the Preparation of Aldehydes
Pyridinium chlorochromate (1 mole equivalent) was ground with silica
gel (1 weight equivalent) using a mortar and pestle, and the result-
ing free-running light orange solid was suspended in dichloromethane
(200 mL) at room temperature. To the stirred suspension was added a
solution of the phenylalkanol (10.0 g) 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 to yield an oil. Vacuum distillation afforded
the title compound as a colourless liquid, unless otherwise indicated.
Aldehydes (20a)–(20c) were prepared in this manner.
1-[(Z)-3-Phenyl-2-propenyl]piperazine (16)
Amixtureof1-(3-phenylprop-2-yn-1-yl)piperazine(1.00 g, 4.99 mmol),
quinoline (250 µL) and Lindlar catalyst (5% Pd/CaCO3/Pb(OAc)2,
500 mg) in methanol (25 mL) was hydrogenated until one equivalent
of hydrogen gas was consumed. The catalyst was removed by filtra-
tion (celite) and the filtrate concentrated under vacuum. The residue
was purified by flash chromatography initially using ethyl acetate and
methanol (1 : 1) as eluent to remove quinoline, followed by a mixture
of dichloromethane, methanol, and ammonia (25 : 4.5 : 0.5) to elute the
product (16)[22] that distilled as a colourless liquid (0.810 g, 80%), bp
150–155◦C (0.5 mmHg). δH (300 MHz; CDCl3) 7.37−7.28 (2 H, m,
H2ꢀꢀ, H6ꢀꢀ), 7.28−7.18 (3 H, m, H3ꢀꢀ, H4ꢀꢀ, H5ꢀꢀ), 6.57 (1 H, br d, J 12,
H3ꢀ), 5.79 (1 H, dt, J 12, 6.5, H2ꢀ), 3.26 (2 H, dd, J 6.5, 2, H1ꢀ), 2.90
(4 H, m, H3, H5), 2.43 (4 H, m, H2, H6), 1.72 (1 H, s, H4). δC (75 MHz;
CDCl3) 137.1, 131.2, 129.5, 128.8, 128.1, 126.8, 56.8, 54.6, 46.1. ESI
mass spectrum m/z 203.1.
5-Phenylpentanal (20a).[23,24] (7.84 g, 79%), bp 84–86◦C
(0.4 mmHg) [lit.[25] bp 129–131◦C (10 mmHg)]. δH (300 MHz;
[D6]acetone) 9.69 (1 H, t, J 2, H1), 7.29−7.21 (2 H, m, H3ꢀ, H5ꢀ),
7.11–7.20 (3 H, m, H2ꢀ, H4ꢀ, H6ꢀ), 2.60 (t, J 7.5 Hz, 2H, H5), 2.38
(2 H, dt, J 7.5, 1.5, H2), 1.69–1.58 (m, 4H, H3, H4). δC (75 MHz;
[D6]acetone) 202.5, 141.9, 128.4, 128.3, 125.8, 43.7, 35.6, 30.8, 21.7.
ESI mass spectrum m/z 509.5 (3M + Na+).
7-Phenylheptanal (20b).[26] (7.61 g, 77%), bp 125–130◦C
(0.25 mmHg). δH (300 MHz; [D6]acetone) 9.73 (1 H, t, J 2, H1),
7.30−7.21 (2 H, m, H3ꢀ, H5ꢀ), 7.19−7.11 (3 H, m, H2ꢀ, H4ꢀ, H6ꢀ), 2.59
(2 H, t, J 7.5, H7), 2.39 (2 H, dt, J 7.5, 2, H2), 1.70−1.55 (4 H, m, H3,
H6), 1.40−1.30 (4 H, m, H4, H5). δC (75 MHz; [D6]acetone) 203.0,
142.8, 128.6, 128.4, 125.8, 44.0, 36.0, 31.4, 29.2, 29.1, 22.2. EI mass
spectrum m/z 190.2.
8-Chloro-11-{4-[(Z)-3-phenyl-2- propenyl]piperazino}-
5H-dibenzo[b,e][1,4]diazepine (18)
(Z)-1-Cinnamylpiperazine (0.620 g, 3.07 mmol) in anhydrous anisole
(5 mL) was treated with
a solution of titanium tetrachloride
10-Phenyldecanal (20c).[27] (6.13 g, 62%), bp 130–134◦C
(0.4 mmHg)thatsolidifiedonstanding. δH (300 MHz;[D6]acetone)9.71
(1 H, t, J 2, H1), 7.28−7.20 (2 H, m, H3ꢀ, H5ꢀ), 7.17−7.10 (3 H, m, H2ꢀ,
H4ꢀ, H6ꢀ), 2.58 (2 H, t, J 7.5, H10), 2.36 (2 H, dt, J 7.5, 2, H2), 1.67–
1.53 (4 H, m, H3, H9), 1.37−1.23 (10 H, m, H4, H5, H6, H7, H8). δC
(75 MHz; [D6]acetone) 202.6, 143.0, 128.5, 128.4, 125.7, 44.0, 36.1,
31.6, 29.54, 29.46 (2 × CH2), 29.4, 29.3, 22.2. EI mass spectrum m/z
232.2.
in toluene (1.0 M, 0.67 mL, 0.67 mmol), followed by a solution
of 8-chloro-10,11-dihydro-5H-dibenzo[b,e][1,4]diazepin-11-one (7)
(150 mg, 0.613 mmol) in dry anisole (10 mL) and worked up as
described in the preparation of (8). The resulting residue was puri-
fied using flash chromatography (ethyl acetate/hexane; 2 : 1) and the
product (18) recrystallized from dichloromethane/methanol as yellow
prisms (215 mg, 82%), mp 75◦C (softens), 99◦C (melts) (Found: C
72.7, H 5.9, N 13.1%. C26H25ClN4 requires C 72.8, H 5.9, N 13.1%).
νmax (KBr)/cm−1 3288, 1604, 1562. λmax (log10 ε)/nm 233 (4.52), 250
(4.42), 295 (4.02). δH (300 MHz; [D6]acetone) 7.39−7.22 (7 H, m, H1,
H3, H2ꢀꢀꢀ, H3ꢀꢀꢀ, H4ꢀꢀꢀ, H5ꢀꢀꢀ, H6ꢀꢀꢀ), 7.07 (1 H, dd, J 8, 1, H4), 7.02 (1 H,
app td, J 7.5, 1, H2), 6.95 (1 H, d, J 2.5, H9), 6.88 (1 H, d, J 8.5, H6),
6.81 (1 H, dd, J 8.5, 2.5, H7), 6.61 (1 H, dt, J 12, 2 Hz, H3ꢀꢀ), 6.55
(1 H, s, H5), 5.83 (1 H, dt, J 12, 6.5, H2ꢀꢀ), 3.43 (4 H, m, H2ꢀ, H6ꢀ),
3.31 (2 H, dd, J 6.5, 2, H1ꢀꢀ), 2.54 (4 H, m, H3ꢀ, H5ꢀ). δC (75 MHz;
[D6]acetone) 164.0, 155.0, 143.4, 143.0, 138.1, 132.8, 132.0, 131.0,
130.8, 129.9, 129.1, 128.5, 127.8, 127.0, 124.6, 123.5, 123.4, 121.4,
121.2, 59.9, 53.8, 48.3. ESI mass spectrum m/z 429.4.
General Procedure for the Preparation of (22a)–(22c)
To a stirred solution of 8-chloro-11-piperazino-5H-dibenzo[b,e][1,4]-
diazepine (21) (250 mg, 0.799 mmol) in dry 1,2-dichloroethane (20 mL)
under nitrogen was added the phenylalkanal (20a–c) (1.05 equivalents)
in 1,2-dichloroethane (5 mL) followed by sodium triacetoxyborohydride
(1.4 equivalents). Stirring was maintained for 2 h after which aque-
ous 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 precipitate
were combined, adjusted to pH 14 by the addition of solid potassium
hydroxide then extracted with dichloromethane (3 × 50 mL). The com-
bined organic extracts were washed with water (30 mL), dried over dried
magnesium sulfate, and then concentrated under vacuum. The result-
ing oil was purified using flash chromatography and the major product
8-Chloro-11-[4-(3-phenyl-2-propynyl)piperazino]-
5H-dibenzo[b,e][1,4]diazepine (17)
1-(3-Phenylprop-2-yn-1-yl)piperazine (0.615 g, 3.07 mmol) in anhy-
drous anisole (5 mL) was treated with a solution of titanium tetrachlo-
ride in toluene (1.0 M, 0.67 mL, 0.67 mmol), followed by a solution

4ꢀ-Arylalkyl Analogues of Clozapine
883
evaporated to dryness. Where appropriate, the residual solid was recrys-
tallized from a suitable solvent system. Amidines (22a)–(22c) were
prepared in this manner.
up as described in the preparation of (6). The crude product was puri-
fied using flash chromatography (chloroform/methanol/25% aqueous
ammonia solution; 19 : 1 : 0.1) affording a pale yellow oil that solidified
upon standing, forming waxy needles (0.99 g, 82%), mp 54–56◦C. δH
(300 MHz; CDCl3 and D2O) 7.34–7.25 (5 H, m, H2ꢀꢀ, H3ꢀꢀ, H4ꢀꢀ, H5ꢀꢀ,
H6ꢀꢀ), 4.66 (2 H, s, H5ꢀ), 3.51 (2 H, t, J 6.5, H3ꢀ), 2.86 (4 H, t, J 5, H3,
H5), 2.41 (6 H, m, H2, H6, H1ꢀ), 1.81 (2 H, app p, J 7, H2ꢀ). δC (75 MHz;
CDCl3) 138.5, 128.2, 127.5, 127.4, 72.8, 68.6, 56.0, 54.5, 46.0, 26.9.
ESI mass spectrum m/z 235.2.
8-Chloro-11-[4-(5-phenylpentyl)piperazino]-5H-dibenzo[ b,e]-[1,4]-
diazepine (22a). Column chromatography (ethyl acetate/hexane; 2 : 3)
gave the title compound, which recrystallized from dichloro-
methane/hexane as yellow microprisms (201 mg, 55%), mp 60◦C (soft-
ens), 110◦C (melts) (Found: C 72.9, H 7.2, N 11.8%. C28H31ClN4
requires C 73.3, H 6.8, N 12.2%). νmax (KBr)/cm−1 3316, 2944,
1616, 1566. λmax (log10 ε)/nm 229 (4.39), 261 (4.20), 297 (4.00). δH
(300 MHz; [D6]acetone) 7.37−7.11 (7 H, m, H1, H3, H2ꢀꢀꢀ, H3ꢀꢀꢀ, H4ꢀꢀꢀ,
H5ꢀꢀꢀ, H6ꢀꢀꢀ), 7.07 (1 H, dd, J 8, 1, H4), 7.02 (1 H, app td, J 7.5, 1, H2),
6.93 (1 H, d, J 2.5, H9), 6.87 (1 H, d, J 8.5, H6), 6.80 (1 H, dd, J 8.5,
2.5, H7), 6.51 (1 H, s, H5), 3.39 (4 H, m, H2ꢀ, H6ꢀ), 2.62 (2 H, t, J 7.5,
H5ꢀꢀ), 2.49 (4 H, m, H3ꢀ, H5ꢀ), 2.36 (t, J 7, 2H, H1ꢀꢀ), 1.66 (2 H, app p, J
7.5, H4ꢀꢀ), 1.54 (2 H, app p, J 7, H2ꢀꢀ), 1.39 (m, 2H, H3ꢀꢀ). δC (75 MHz;
[D6]acetone) 164.1, 155.1, 143.7, 143.6, 143.0, 132.8, 131.1, 129.3,
129.2, 128.7, 127.1, 126.5, 124.8, 123.50, 123.45, 121.4, 121.2, 59.2,
54.0, 48.4, 36.6, 32.2, 27.9, 27.6. ESI mass spectrum m/z 459.4.
8-Chloro-11-[4-(7-phenylheptyl)piperazino]-5H- dibenzo[ b,e][1,4]-
diazepine (22b). Column chromatography (ethyl acetate/hexane; 2 : 1)
gave the title compound, which recrystallized from methanol/water
as bright yellow microcrystals (225 mg, 58%), mp 62◦C (softens),
90◦C (melts) (Found: C 74.1, H 7.4, N 11.4%. C30H35ClN4 requires
C 74.0, H 7.2, N 11.5%). νmax (KBr)/cm−1 3320, 2936, 1614, 1566.
λmax (log10 ε)/nm 229 (4.41), 261 (4.23), 297 (4.03). δH (300 MHz;
[D6]acetone) 7.36–7.10 (7 H, m, H1, H3, H2ꢀꢀꢀ, H3ꢀꢀꢀ, H4ꢀꢀꢀ, H5ꢀꢀꢀ, H6ꢀꢀꢀ),
7.06 (1 H, br d, J 8, H4), 7.01 (1 H, app t, J 7.5, H2), 6.94 (1 H, d, J
2.5, H9), 6.87 (1 H, d, J 8.5, H6), 6.80 (1 H, dd, J 8.5, 2.5, H7), 6.47
(1 H, s, H5), 3.39 (4 H, m, H2ꢀ, H6ꢀ), 2.61 (2 H, t, J 7.5, H7ꢀꢀ), 2.48
(4 H, m, H3ꢀ, H5ꢀ), 2.35 (2 H, t, J 7, H1ꢀꢀ), 1.62 (2 H, app p, J 7, H6ꢀꢀ),
1.49 (2 H, app p, J 7, H2ꢀꢀ), 1.42–1.28 (6 H, m, H3ꢀꢀ, H4ꢀꢀ, H5ꢀꢀ). δC
(75 MHz; [D6]acetone) 164.1, 155.1, 143.8, 143.6, 143.0, 132.8, 131.1,
129.3, 129.2, 128.7, 127.1, 126.5, 124.8, 123.50, 123.45, 121.4, 121.3,
59.3, 54.0, 48.4, 36.6, 32.4, 30.2, 30.0, 28.2, 27.7. ESI mass spectrum
m/z 487.4.
8-Chloro-11-[4-(10-phenyldecyl)piperazino]-5H-dibenzo[ b,e][1,4]-
diazepine (22c). Column chromatography (ethyl acetate/hexane; 2 : 1)
gave the title compound as a bright yellow oil that solidified on stand-
ing (289 mg, 68%), mp 80.5–82◦C (Found: C 75.0, H 8.0, N 10.5%.
C33H41ClN4 requires C 74.9, H 7.8, N 10.6%). νmax (KBr)/cm−1 3364,
2932, 1608, 1566. λmax (log10 ε)/nm 228 (4.42), 261 (4.24), 296 (4.03).
δH (300 MHz; [D6]acetone) 7.36−7.11 (7 H, m, H1, H3, H2ꢀꢀꢀ, H3ꢀꢀꢀ,
H4ꢀꢀꢀ, H5ꢀꢀꢀ, H6ꢀꢀꢀ), 7.06 (1 H, br d, J 8, H4), 7.01 (1 H, app td, J 8, 1,
H2), 6.94 (1 H, d, J 2, H9), 6.87 (1 H, d, J 8, H6), 6.80 (1 H, dd, J 8, 2,
H7), 6.51 (1 H, s, H5), 3.39 (4 H, m, H2ꢀ, H6ꢀ), 2.61 (2 H, t, J 7.5, H10ꢀꢀ),
2.4ꢀ8ꢀ (4 H, m, H3ꢀ, H5ꢀ), 2.35 (2 H, t, J 7, H1ꢀꢀ), 1.62 (2 H, app p, J 7,
H9 ), 1.49 (2 H, app p, J 7, H2ꢀꢀ), 1.41–1.26 (12 H, m, H3ꢀꢀ, H4ꢀꢀ, H5ꢀꢀ,
H6ꢀꢀ, H7ꢀꢀ, H8ꢀꢀ). δC (75 MHz; [D6]acetone) 164.0, 155.0, 143.6, 143.5,
142.8, 132.7, 131.0, 129.2, 129.1, 128.6, 127.1, 126.4, 124.7, 123.4,
123.3, 121.3, 121.2, 59.3, 53.9, 48.3, 36.6, 32.4, 30.4, 30.34 (2 × CH2),
30.25, 30.1, 28.2, 27.7. ESI mass spectrum m/z 529.5.
11-{4-[2-(Benzyloxy)ethyl]piperazino}-8-chloro-
5H-dibenzo[b,e][1,4]diazepine (25a)
1-[2-(Benzyloxy)ethyl]piperazine (24a) (0.650 g, 2.95 mmol) in anhy-
drous anisole (5 mL) was treated with a solution of titanium tetrachloride
in toluene (1.0 M, 0.75 mL, 0.75 mmol), followed by a solution of lac-
tam (7) (180 mg, 0.738 mmol) in dry anisole (10 mL) and worked up as
described in the preparation of (8). The product was purified using flash
chromatography (ethyl acetate) and recrystallized from methanol/water
as yellow platelets (119 mg, 36%), mp 154–155◦C (Found: C 69.7, H
6.0, N 12.1%. C26H27ClN4O requires C 69.9, H 6.1, N 12.5%). νmax
(KBr)/cm−1 3326, 1610, 1563. λmax (log ε)/nm 229 (4.34), 260 (4.17),
297 (3.97). δH (300 MHz; CDCl3) 7.34–7.23 (7 H, m, H1, H3, H2ꢀꢀꢀ,
H3ꢀꢀꢀ, H4ꢀꢀꢀ, H5ꢀꢀꢀ, H6ꢀꢀꢀ), 7.05 (1 H, d, J 2.5, H9), 6.99 (1 H, m, H2),
6.79 (2 H, dd, J 8, 2.5, H4, H7), 6.58 (1 H, d, J 8.5, H6), 4.87 (1 H, s,
H5), 4.54 (2 H, s, H4ꢀꢀ), 3.61 (2 H, t, J 5.5, H2ꢀꢀ), 3.47 (4 H, m, H2ꢀ,
H6ꢀ), 2.67 (2 H, t, J 5.5, H1ꢀꢀ), 2.59 (4 H, m, H3ꢀ, H5ꢀ). δC (75 MHz;
CDCl3) 162.9, 152.9, 142.0, 140.5, 138.5, 132.0, 130.4, 129.2, 128.5,
127.9, 127.8, 126.9, 123.6, 123.1 (2 × CH), 120.2, 120.1, 73.3, 67.7,
58.1, 53.6, 47.4. ESI mass spectrum m/z 447.2.
11-{4-[3-(Benzyloxy)propyl]piperazino}-8-chloro-
5H-dibenzo[b,e][1,4]diazepine (25b)
A mixture of phosphorus pentachloride (199 mg, 0.957 mmol) and lac-
tam (7) (213 mg, 0.870 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 (20) was dissolved in anhydrous
1,4-dioxan (15 mL) and treated with 1-[3-(benzyloxy)propyl]piperazine
(24b) (398 mg, 1.70 mmol) in anhydrous 1,4-dioxan (5 mL). The reac-
tion mixture was heated at reflux for 16 h, then cooled and evaporated
to dryness. The dark red-brown residue was partitioned between ethyl
acetate and aqueous hydrochloric acid solution (2 M, 20 mL) and the
organic layer extracted with aqueous hydrochloric acid solution (2 M,
3 × 20 mL). The aqueous fraction was made alkaline with ammonia
solution (25%, 20 mL) and the product was extracted with ethyl acetate
(3 × 20 mL), washed with water, dried over dried magnesium sulfate,
and evaporated to dryness. The product was purified using flash chro-
matography (ethyl acetate) affording (25b) as a yellow oil (136 mg,
34%). νmax (KBr)/cm−1 3304, 1605, 1564. λmax (log ε)/nm 227 (4.36),
259 (4.20), 290 (3.92). δH (300 MHz; CDCl3) 7.35–7.20 (7 H, m, H1,
H3, H2ꢀꢀꢀ, H3ꢀꢀꢀ, H4ꢀꢀꢀ, H5ꢀꢀꢀ, H6ꢀꢀꢀ), 7.06 (1 H, d, J 2.5, H9), 6.99 (1 H, m
H2), 6.80 (2 H, m, H4, H7), 6.60 (1 H, d, J 8.5, H6), 4.87 (1 H, s, H5),
4.51 (2 H, s, H5ꢀꢀ), 3.53 (4 H, m, H2ꢀ, H6ꢀ), 3.46 (2 H, br s, H3ꢀꢀ), 2.50
(6 H, m, H1ꢀꢀ, H3ꢀ, H5ꢀ), 1.84 (2 H, app p, J 7.5, H2ꢀꢀ). δC (75 MHz;
CDCl3) 162.9, 152.9, 142.0, 140.5, 138.7, 132.0, 130.4, 129.2, 128.5,
127.7, 127.6, 126.9, 123.6, 123.1 (2 × CH), 120.2, 120.1, 73.0, 68.7,
55.6, 53.3, 47.4, 27.6. ESI high-resolution mass spectrum (Found: m/z
461.210. Calc. for C27H30ClN4O: m/z 461.211). The title compound
was converted into the hydrochloride salt by treatment with 3 M hydro-
gen chloride in ethyl acetate, evaporated to dryness, and then analyzed
chromatographically. HPLC (λ 254 nm) tR 10.18 min (isocratic), tR
25.30 min (gradient).
1-[2-(Benzyloxy)ethyl]piperazine (24a)
Benzyl 2-bromoethyl ether (23a) (0.85 g, 3.95 mmol) in toluene (20 mL)
was treated with piperazine (1.60 g, 18.6 mmol) and worked up as
described in the preparation of (6). The crude product was puri-
fied using flash chromatography (chloroform/methanol/25% aqueous
ammonia solution; 19 : 1 : 0.1) affording a pale yellow oil that solidified
upon standing forming waxy needles (0.67 g, 77%), mp 30–34◦C. δH
(300 MHz; CDCl3) 7.34–7.26 (5 H, m, H2ꢀꢀ, H3ꢀꢀ, H4ꢀꢀ, H5ꢀꢀ, H6ꢀꢀ), 4.54
(2 H, s, H4ꢀ), 3.59 (2 H, t, J 6, H2ꢀ), 2.90 (4 H, m, H3, H5), 2.60 (2 H,
t, J 6, H1ꢀ), 2.46 (4 H, m, H2, H6), 1.56 (1 H, br s, H4). δC (75 MHz;
CDCl3) 138.5, 128.5, 127.8, 127.7, 73.2, 67.7, 58.7, 55.1, 46.2. ESI
mass spectrum m/z 221.2.
2-(Benzo[1,3]dioxol-5-yl)ethanol (27)
The title compound was prepared according to the procedure of
Semmelhack et al.[6] from 3,4-methylenedioxyphenylacetic acid (26).
Following workup, the resulting pale yellow oil was purified using flash
chromatography (ether/hexane; 1 : 1) to afford the alcohol as a colour-
less oil (1.25 g, 90%) which was used in the following reaction without
1-[3-(Benzyloxy)propyl]piperazine (24b)
Benzyl 3-bromopropyl ether (23b) (1.17 g, 5.09 mmol) in toluene
(30 mL) was treated with piperazine (1.76 g, 20.4 mmol) and worked

884
B. Capuano et al.
further purification. δH (300 MHz; CDCl3) 6.74 (1 H, d, J 8, H7ꢀ), 6.71
(1 H, d, J 1.5, H4ꢀ), 6.66 (1 H, dd, J 8, 1.5, H6ꢀ), 5.91 (2 H, s, H2ꢀ),
3.79 (2 H, t, J 6.5, H1), 2.77 (2 H, t, J 6.5, H2), 1.68 (1 H, br s, OH).
δC (75 MHz; CDCl3) 148.0, 146.3, 132.4, 122.1, 109.5, 108.5, 101.0,
63.9, 39.0. ESI mass spectrum m/z 166.9.
8-Chloro-11-{4-[(1H-indol-3- yl)ethyl]piperazino)-5H-
dibenzo[b,e][1,4]diazepine (32a)
8-Chloro-11-piperazino-5H-dibenzo[b,e][1,4]diazepine (21) (180 mg,
0.575 mmol) in dry 1,2-dichloroethane (20 mL) under nitrogen was
treated with 2-(1H-indol-3-yl)ethanal (31a) (101 mg, 0.633 mmol) in
1,2-dichloroethane (5 mL) followed by sodium triacetoxyborohydride
(183 mg, 0.863 mmol) and worked up as for the preparation of (22a)–
(22c). The residue was purified using flash chromatography (ethyl
acetate) and the product recrystallized from dichloromethane/hexane as
yellow prisms (184 mg, 70%), mp 130–132◦C (Found: C 71.2, H 5.7, N
15.3%. C27H26ClN5 requires C 71.1, H 5.7, N 15.4%). νmax (KBr)/cm−1
3448, 1600, 1556. λmax (log10 ε)/nm 223 (4.63), 264 (4.27), 292 (4.17).
δH (300 MHz; [D6]acetone) 9.93 (1 H, br s, H1ꢀꢀꢀ), 7.58 (1 H, m, H4ꢀꢀꢀ),
7.27–7.39 (3 H, m, H3, H1, H7ꢀꢀꢀ), 7.19 (1 H, m, H2ꢀꢀꢀ), 6.97–7.11 (4 H,
m, H2, H4, H5ꢀꢀꢀ, H6ꢀꢀꢀ), 6.96 (1 H, d, J 2.5, H9), 6.88 (1 H, d, J 8.5,
H6), 6.80 (1 H, dd, J 8.5, 2.5, H7), 6.52 (1 H, s, H5), 3.45 (4 H, m, H2ꢀ,
H6ꢀ), 2.96 (2 H, m, H2ꢀꢀ), 2.71 (2 H, m, H1ꢀꢀ), 2.63 (4 H, m, H3ꢀ, H5ꢀ). δC
(75 MHz; [D6]acetone) 164.1, 155.0, 143.5, 142.9, 137.8, 132.8, 131.1,
128.8, 128.6, 127.0, 124.7, 123.48, 123.45, 123.2, 122.1, 121.4, 121.2,
119.40, 119.39, 114.5, 112.1, 60.2, 53.9, 48.4, 23.8. ESI mass spectrum
m/z 456.3.
2-(Benzo[1,3]dioxol-5-yl)ethanal (28)
2-(1,3-Benzodioxol-5-yl)ethanol (27) (0.500 g, 3.01 mmol) in dichloro-
methane (25 mL) was treated with a finely ground mixture of pyridinium
chlorochromate(0.973 g, 4.51 mmol)andsilicagel(0.973 g)andworked
up as for the preparation of (20a)–(20c) to give the title compound (28)
(0.404 g, 82%) as a pale yellow liquid[7] which was used in the following
reaction without further purification. δH (300 MHz; CD2Cl2) 9.66 (1 H,
t, J 2, H1), 6.78 (1 H, d, J 8, H7ꢀ), 6.67 (1 H, d, J 1.5, H4ꢀ), 6.64 (1 H, dd,
J 8, 1.5, H6ꢀ), 5.92 (2 H, s, H2ꢀ), 3.56 (2 H, d, J 2 Hz, H2). δC (75 MHz;
CD2Cl2) 199.7, 148.7, 147.5, 126.3, 123.3, 110.4, 109.0, 101.8, 50.5.
EI mass spectrum m/z 164.0.
11-{4-[2-(Benzo[1,3]dioxol-5-yl)ethyl]piperazino}-
8- chloro-5H-dibenzo[b,e][1,4]diazepine (29)
8-Chloro-11-{4-[2-(5-methoxy-1H-indol-3- yl)ethyl]piperazino)-
5H-dibenzo[b,e][1,4]diazepine (32b)
8-Chloro-11-piperazino-5H-dibenzo[b,e][1,4]diazepine (21) (250 mg,
0.799 mmol) in dry 1,2-dichloroethane (20 mL) under nitrogen
was treated with 2-(1,3-benzodioxol-5-yl)ethanal (28) (138 mg,
0.839 mmol) in 1,2-dichloroethane (5 mL) followed by sodium triace-
toxyborohydride (237 mg, 1.12 mmol) and worked up as for the prepa-
ration of (22a)–(22c). The residue was purified using flash chromato-
graphy (ethyl acetate/hexane; 2 : 1) and the product (29) recrystallized
from dichloromethane/hexane as bright yellow prisms (151 mg, 41%),
mp 156–157.5◦C (Found: C 67.4, H 5.5, N 11.9%. C26H25ClN4O2
requires C 67.7, H 5.5, N 12.2%). νmax (KBr)/cm−1 3292, 1600, 1562.
λmax (log10 ε)/nm 231 (4.49), 262 (4.26), 290 (4.18). δH (300 MHz;
[D6]acetone) 7.33 (1 H, ddd, J 8, 7.5, 1.5, H3), 7.29 (1 H, dd, J 7.5,
1.5, H1), 7.07 (1 H, dd, J 8, 1, H4), 7.02 (1 H, app td, J 7.5, 1, H2),
6.95 (1 H, d, J 2.5, H9), 6.88 (1 H, d, J 8.5, H6), 6.83–6.78 (2 H, m,
H7, H4ꢀꢀꢀ), 6.74 (1 H, dd, J 8, 0.5, H7ꢀꢀꢀ), 6.70 (1 H, dd, J 8, 1.5, H6ꢀꢀꢀ),
6.52 (1 H, s, H5), 5.93 (2 H, s, H2ꢀꢀꢀ), 3.41 (4 H, m, H2ꢀ, H6ꢀ), 2.73 (2 H,
m, H2ꢀꢀ), 2.52–2.62 (6 H, m, H3ꢀ, H5ꢀ, H1ꢀꢀ). δC (75 MHz; [D6]acetone)
164.0, 155.0, 148.6, 146.8, 143.5, 142.9, 135.5, 132.8, 131.0, 128.6,
127.0, 124.7, 123.5, 123.4, 122.4, 121.4, 121.2, 110.0, 108.4, 101.7,
61.3, 53.8, 48.3, 33.9. ESI mass spectrum m/z 461.3.
8-Chloro-11-piperazino-5H-dibenzo[b,e][1,4]diazepine (21) (203 mg,
0.649 mmol) in dry 1,2-dichloroethane (20 mL) under nitrogen
was treated with 2-(5-methoxy-1H-indol-3-yl)ethanal (31b) (135 mg,
0.713 mmol) in 1,2-dichloroethane (5 mL) followed by sodium tri-
acetoxyborohydride (206 mg, 0.973 mmol) and worked up as for
the preparation of (22a)–(22c). The residue was purified using flash
chromatography (ethyl acetate) using the technique of solid addition
and the product recrystallized from methanol/water as yellow micro-
prisms (191 mg, 61%), mp 255–257◦C (Found: C 67.2, H 5.9, N
13.2%. C28H28ClN5O · CH3OH requires C 67.2, H 6.2, N 13.5%). νmax
(KBr)/cm−1 3432, 3300, 1598, 1554. λmax (log10 ε)/nm 226 (4.73), 263
(4.38), 297 (4.23). δH (300 MHz; [D6]acetone) 9.78 (1 H, br s, H1ꢀꢀꢀ),
7.37–7.29 (2 H, m, H1, H3), 7.25 (1 H, d, J 9, H7ꢀꢀꢀ), 7.16 (1 H, br s,
H2ꢀꢀꢀ), 7.09 (1 H, m, H4ꢀꢀꢀ), 7.07 (1 H, m H4), 7.03 (1 H, m, H2), 6.95
(1 H, d, J 2.5, H9), 6.88 (1 H, d, J 8.5, H6), 6.81 (1 H, dd, J 8.5, 2.5, H7),
6.75 (1 H, dd, J 9, 2.5, H6ꢀꢀꢀ), 6.53 (1 H, s, H5), 3.81 (3 H, s, OCH3), 3.42
(4 H, m, H2ꢀ, H6ꢀ), 2.93 (2 H, m, H2ꢀꢀ), 2.71 (2 H, m, H1ꢀꢀ), 2.64 (4 H, m,
H3ꢀ, H5ꢀ). δC (75 MHz; [D6]DMSO) 162.7, 154.0, 152.9, 142.1, 141.9,
131.9, 131.3, 129.8, 127.5, 126.6, 125.5, 123.1, 123.0, 122.4, 122.2,
120.5, 120.3, 112.2, 111.9, 110.9, 100.2, 58.7, 55.4, 52.5, 46.9, 23.3.
ESI mass spectrum m/z 486.3.
2-(1H-Indol-3-yl)ethanal (31a)
The title compound was prepared according to the procedure of Schlecht
et al.[8] from l-tryptophan. The product was purified by flash chromato-
graphy (ethyl acetate/hexane; 2 : 5) affording the aldehyde as a yellow oil
(491 mg, 42%) which was used in a subsequent reaction without further
purification. νmax (KBr)/cm−1 3430, 1722. δH (300 MHz; [D6]acetone)
10.18 (1 H, br s, H1ꢀ), 9.70 (1 H, t, J 2.5, H1), 7.52 (1 H, m, H4ꢀ), 7.42
(1 H, app dt, J 8, 1, H7ꢀ), 7.32 (1 H, br d, J 2.5, H2ꢀ), 7.13 (1 H, m,
H6ꢀ), 7.04 (1 H, ddd, J 8, 7, 1, H5ꢀ), 3.79 (2 H, br d, J 2.5, H2). δC
(75 MHz; [D6]acetone) 200.1, 136.9, 128.0, 124.2, 122.9, 120.3, 119.0,
111.9, 106.7, 40.9. EI mass spectrum m/z 159.1.
4-{2-[4-(8-Chloro-5H-dibenzo[b,e][1,4]diazepin-
11-yl)piperazino]ethyl}benzene-1,2-diol (33)
To
a solution of 11-[4-(1,3-benzodioxol-5-ylethyl)piperazino]-8-
chloro-5H-dibenzo[b,e][1,4]diazepine (29) (50 mg, 0.108 mmol) in
anhydrous dichloromethane (10 mL) at room temperature was added
a solution of boron tribromide in dichloromethane (1.0 M, 1.08 mL,
1.08 mmol). A precipitate was observed and the mixture was stirred
at ambient temperature for 5 h. After this time, methanol (10 mL) was
added to the mixture and the resulting solution evaporated to dryness.
The residue was partitioned between saturated sodium bicarbonate solu-
tion (25 mL) and ethyl acetate (25 mL) and the aqueous layer extracted
with ethyl acetate (2 × 25 mL). The organic fractions were pooled,
washed with water (50 mL), brine (50 mL), dried over dried magne-
sium sulfate, and then evaporated to dryness. The residue was purified
by flash chromatography (ethyl acetate/methanol; 40 : 1). The column
fractions were combined, then evaporated to dryness affording the title
compound (33) as a pale yellow foam (33 mg, 68%) (Found: C 52.9,
H 5.3, N 9.5%. C25H25ClN4O2 · 2HCl · 2½H2O requires C 53.0, H 5.7,
N 9.9%). νmax (KBr)/cm−1 3600–3000, 3368, 1600, 1560. λmax (log10
ε)/nm 228 (4.47), 262 (4.22), 291 (4.08). δH (300 MHz; [D4]methanol)
7.32 (1 H, app td, J 7.5, 1.5, H3ꢀꢀꢀ), 7.26 (1 H, dd, J 7.5, 1.5, H1ꢀꢀꢀ), 6.98–
7.02 (2 H, m, H2ꢀꢀꢀ, H4ꢀꢀꢀ), 6.96 (1 H, d, J 2.5, H9ꢀꢀꢀ), 6.83 (1 H, dd, J 8.5,
2-(5-Methoxy-1H-indol-3-yl)ethanal (31b)
The title aldehyde was prepared from 5-methoxy-dl-tryptophan accord-
ing to the procedure previously described.[8] The product was purified by
flash chromatography (ethyl acetate/hexane; 1 : 3) to afford the aldehyde
(31b) as a yellow oil (139 mg, 34%) which was used in a subsequent
reaction without further purification. νmax (NaCl)/cm−1 3428, 1718. δH
(300 MHz; CD2Cl2) 9.71 (1 H, t, J 2.5, H1), 8.31 (1 H, br s, H1ꢀ), 7.23
(1 H, d, J 9, H7ꢀ), 7.07 (1 H, br d, J 2.5, H2ꢀ), 6.93 (1 H, d, J 2.5, H4ꢀ),
6.83 (1 H, dd, J 9, 2.5, H6ꢀ), 3.80 (3 H, s, OCH3), 3.73 (2 H, br d, J 2.5,
H2). δC (75 MHz; CD2Cl2) 200.2, 154.9, 132.0, 128.5, 125.0, 113.1,
112.7, 106.3, 100.7, 56.3, 40.9. EI mass spectrum m/z 189.1.

4ꢀ-Arylalkyl Analogues of Clozapine
885
2.5, H7ꢀꢀꢀ), 6.78 (1 H, d, J 8.5, H6ꢀꢀꢀ), 6.69 (1 H, d, J 8, H6), 6.66 (1 H, d,
J 2, H3), 6.53 (1 H, dd, J 8, 2, H5), 3.43 (4 H, m, H2ꢀꢀ, H6ꢀꢀ), 2.52–2.73
(8H, m, H1ꢀ, H2ꢀ, H3ꢀꢀ, H5ꢀꢀ). δC (75 MHz; [D4]methanol) 165.4, 155.6,
146.4, 144.8, 143.7, 143.2, 133.5, 132.8, 131.5, 129.6, 127.3, 124.6,
124.5, 124.0, 121.6, 121.4, 121.0, 117.0, 116.6, 61.9, 54.1, 48.3, 33.5.
ESI high-resolution mass spectrum (Found: m/z 449.1730. Calc. for
C25H26ClN4O2: m/z 449.1744).
the preparation of (22a)–(22c). The residue was purified using flash
chromatography (ethyl acetate/hexane; 1 : 3) and the product (38)
recrystallized from methanol/water as yellow microprisms (125 mg,
44%), mp 119◦C (softens), 127◦C (melts) (Found: C 70.3, H 7.1,
N 11.7%. C27H31ClN4·CH3OH requires C 70.2, H 7.4, N 11.7%).
νmax (KBr)/cm−1 3320, 2916, 1604, 1562. λmax (log10 ε)/nm 228 (4.39),
261 (4.19), 298 (4.02). δH (300 MHz; [D6]acetone) 7.35–7.25 (2 H, m,
H1, H3), 7.05 (1 H, dd, J 8, 1, H4), 7.00 (1 H, app td, J 7.5, 1, H2), 6.95
(1 H, d, J 2.5, H9), 6.86 (1 H, d, J 8.5, H6), 6.79 (1 H, dd, J 8.5, 2.5,
H7), 6.45 (1 H, s, H5), 3.42 (4 H, m, H2ꢀ, H6ꢀ), 2.51 (4 H, m, H3ꢀ, H5ꢀ),
2.17–2.03 (5 H, m), 1.63–1.91 (8H, m), 1.42 (1 H, br s), 1.38 (1 H, br s).
δC (75 MHz; [D6]acetone) 164.0, 155.1, 143.6, 142.9, 132.8, 131.1,
128.7, 127.1, 124.7, 123.41, 123.36, 121.4, 121.2, 68.7, 50.4, 48.7, 38.6,
38.1, 32.2, 30.5, 28.6, 28.4. ESI mass spectrum m/z 447.4.
8-Chloro-11-{4-[(5-hydroxy-1H-3-indolyl)ethyl]piperazino)-
5H-dibenzo[b,e][1,4]diazepine (34)
8-Chloro-11-{4- [2- (5-methoxy-1H-indol-3-yl)ethyl] piperazino)-5H-
dibenzo[b,e]-[1,4]diazepine (32b) (60 mg, 0.123 mmol) in anhydrous
dichloromethane (10 mL) was treated with a solution of boron tribro-
mide in dichloromethane (1.0 M, 1.23 mL, 1.23 mmol) and worked up as
for the preparation of (33). The resulting residue was purified using flash
chromatography (ethyl acetate/methanol; 20 : 1) to afford the product as
a tan foam (42 mg, 72%). νmax (KBr)/cm−1 3442, 3368, 1601, 1561.
λmax (log10 ε)/nm 227 (4.53), 260 (4.21), 300 (4.13). δH (300 MHz;
[D4]methanol) 7.34 (1 H, app td, J 8, 1.5, H3), 7.28 (1 H, dd, J 7.5,
1.5, H1), 7.16 (1 H, d, J 8.5, H7ꢀꢀꢀ), 7.07–6.98 (3 H, m, H2, H4, H2ꢀꢀꢀ),
6.97 (1 H, d, J 2.5, H9), 6.94 (1 H, d, J 2.5, H4ꢀꢀꢀ), 6.85 (1 H, dd, J 8.5,
2.5, H7), 6.80 (1 H, d, J 8.5, H6), 6.68 (1 H, dd, J 8.5, 2.5, H6ꢀꢀꢀ), 3.51
(4 H, m, H2ꢀ, H6ꢀ), 2.96 (2 H, m, H2ꢀꢀ), 2.87 (2 H, m, H1ꢀꢀ), 2.82 (4 H,
m, H3ꢀ, H5ꢀ). δC (75 MHz; [D4]methanol) 165.2, 155.6, 151.4, 143.7,
143.1, 133.7, 133.3, 131.5, 129.6, 129.4, 127.4, 124.8, 124.4, 124.3,
124.1, 121.7, 121.5, 112.9, 112.6, 112.3, 103.6, 60.2, 53.9, 47.9, 23.3.
ESI high-resolution mass spectrum (Found: m/z 472.1883. Calc. for
C27H27ClN5O: m/z 472.1904). The title compound was converted into
the hydrochloride salt by treatment with 3 M hydrogen chloride in ethyl
acetate, evaporated to dryness, and then analyzed chromatographically.
HPLC (λ 260 nm) tR 2.80 min (isocratic), tR 19.07 min (gradient).
Pharmacology Procedures
Test Compounds. The synthetic targets were tested in preliminary
in vitro and in vivo assays as their hydrochloride salts. The compounds
were dissolved in anhydrous ethyl acetate as their free base. A solution
of 3 M hydrogen chloride in dry ethyl acetate was added to precipitate
the compounds as their hydrochloride salt. The solvent was removed
under reduced pressure and the resulting oil dissolved in anhydrous
methanol. The solvent was again concentrated under vacuum to remove
all traces of hydrogen chloride. The remaining residue was taken up in
1 mL methanol to which 9 mL of ethyl acetate was added. The resulting
suspension was concentrated under reduced pressure, then dried under
vacuum overnight to afford the hydrochloride salt as a fine pale-yellow
powder in quantitative yield.
In Vitro Studies
Striatal and Cortical Tissue Preparation. Adult male Sprague–
Dawley rats weighing 200–250 g were killed by decapitation and the
brains removed rapidly and placed on ice. The striatum and cortex were
dissected and samples were placed in microcentrifuge tubes and stored
frozen at −80◦C until the day of the receptor binding assays.
4-[-4-(8-Chloro-5H-dibenzo[b,e][1,4]diazepin-11-yl)piperazino]-1-
(4-fluorophenyl)-1-butanone (36)
To a stirred solution of 8-chloro-11-piperazino-5H-dibenzo[b,e][1,4]-
diazepine (21) (150 mg, 0.480 mmol), triethylamine (97.2 mg, 130 µL
0.960 mmol) and sodium iodide (72 mg, 0.480 mmol) in dry 1,2-
dimethoxyethane (20 mL) was added to commercial 4-chloro-4ꢀ-
fluorobutyrophenone (160 µL, 0.960 mmol). The mixture was heated at
reflux for 24 h, concentrated under reduced pressure, and the resulting
oily residue acidified with aqueous hydrochloric acid (2 M, 25 mL) to
produce a pale yellow precipitate. The aqueous mixture was warmed
and stirred until dissolution was complete, and then washed with
dichloromethane (3 × 25 mL). The aqueous layer was adjusted to pH
10 by the addition of solid potassium bicarbonate, and then extracted
with dichloromethane (3 × 25 mL). The combined organic extracts were
washed with water (25 mL), dried over dried magnesium sulfate, and
then concentrated under vacuum. The resulting residue was purified
using flash chromatography (ethyl acetate) to afford the product as
a pale yellow foam (62 mg, 27%) (Found: C 68.0, H 5.6, N 11.4%.
C27H26ClFN4O requires C 68.0, H 5.5, N 11.7%). νmax (KBr)/cm−1
3352, 1677, 1599, 1563. λmax (log10 ε)/nm 235 (4.48), 258 (4.32), 295
(4.02). δH (300 MHz; [D6]acetone) 8.10 (2 H, m, H2ꢀꢀꢀ, H6ꢀꢀꢀ), 7.33 (1 H,
app td, J 7.5, 1.5, H3ꢀꢀ), 7.29–7.21 (3 H, m, H1ꢀꢀ, H3ꢀꢀꢀ, H5ꢀꢀꢀ), 7.06 (1 H,
br d, J 8, H4ꢀꢀ), 7.01 (1 H, app td, J 7.5, 1, H2ꢀꢀ), 6.93 (1 H, d, J 2.5,
H9ꢀꢀ), 6.87 (1 H, d, J 8.5, H6ꢀꢀ), 6.80 (1 H, dd, J 8.5, 2.5, H7ꢀꢀ), 6.51 (1 H,
s, H5ꢀꢀ), 3.34 (4 H, m, H3ꢀ, H5ꢀ), 3.07 (2 H, t, J 7, H2), 2.50 (4 H, m,
H2ꢀ, H6ꢀ), 2.45 (1 H, t, J 7, H4), 1.93 (2 H, app p, J 7, H3). δC (75 MHz;
[D6]acetone) 198.8 (C O), 166.4 (d, J 252, CF), 164.0, 154.0, 143.5,
142.9, 135.3, 132.8, 131.8 (d, J 9, CH), 131.0, 128.6, 127.0, 124.7,
123.5, 123.4, 121.4, 121.2, 116.3 (d, J 22, CH), 58.3, 53.8, 48.2, 36.6,
22.5. ESI mass spectrum m/z 477.2.
Rat Radioligand Binding Assays. Frozen tissue samples from rat
striatum were homogenized gently in ice-cold assay buffer (50 mM Tris
HCl, 120 mM NaCl, 5 mM KCl, 2 nM CaCl2, and 1 mM MgCl2; pH 7.4)
in a Ultra-Turrax homogenizer. Tissue was pelleted by centrifugation
at 1000 × g for 10 min at 0◦C in a Beckman Avanti J–25 Centrifuge.
The pellet was discarded, and the supernatant centrifuged for 15 min
at 40 000 × g at 0◦C. The resulting supernatant was then discarded,
and the remaining pellet resuspended in buffer and re-centrifuged for
15 min at 40 000 × g at 0◦C. The supernatant was discarded and the
remaining pellet resuspended in assay buffer to a final concentration of
2.0 mg mL−1 (estimated protein concentration of 0.07 mg of protein/
assay tube), frozen and stored at −80◦C until the day of the binding
experiment.
Tissue-protein levels were estimated using the Lowry method. The
assays were carried out using the following: (a) for 5-HT2A; rat cortical
membranes, [3H]ketanserin (0.5 nM) as radioligand, and methysergide
(1 µM) as reference compound for non-specific binding; and (b) for
D2; rat striatal membranes, [3H]spiperone (0.3 nM) and haloperidol
(10 µM). All compounds were assayed as their hydrochloride salts dis-
solved in 30% ethanol/water to a stock concentration of 3 mM, and
then diluted with assay buffer to a final concentration of 1 µM. Follow-
ing incubation at 37◦C for 15 min, 96 tube plates were filtered rapidly
through a Packard 96 GF/C filter and rinsed four times with 5 mL of ice-
cold buffer (50 mM Tris, 140 mM NaCl, 5 mM MgCl2; pH 7.4) using
a Packard microcell harvester (Packard Instruments, Downers Grove,
IL). Filters were allowed to dry, and then 40 µL of Microscint-20 scin-
tillation cocktail was added to each filter well. Each plate was sealed
using a microplate heat-sealing film on a microplate sealer then counted
on a Packard topcount microplate scintillation counter (Packard Instru-
ments). In the preliminary binding assay, the results are expressed as
percentage inhibition compared with results in the absence of drug, and
represent the mean of duplicate tubes at the tested concentration of 1 µM
in a single experiment.
11-[4-(2-Adamantyl)piperazino]-8-chloro-
5H-dibenzo[b,e][1,4]diazepine (38)
8-Chloro-11-piperazino-5H-dibenzo[b,e][1,4]diazepine (21) (200 mg,
0.639 mmol) in dry 1,2-dichloroethane (20 mL) was treated with 2-
adamantanone (101 mg, 0.671 mmol) followed by sodium triacetoxy-
borohydride (190 mg, 0.895 mmol) and worked up as described in

886
B. Capuano et al.
Cloned Radioligand Binding Assays. The assay for the determi-
and S. Thomson for NMR and mass spectra of compounds
described. Funding for this work was provided by the
Victorian College of Pharmacy (Monash University).
nation of dopamine D4.4 receptor affinity was carried out using human
recombinant (mammalian CHO-K1 cells) D4.4 receptors, [3H]spiperone
(0.3 nM) as radioligand, and L-754,870 (1 µM) as reference com-
pound for non-specific binding. All compounds were assayed as their
hydrochloride salts dissolved in 30% ethanol/water to a stock concentra-
tion of 3 mM, and then diluted with assay buffer to a final concentration
of 1 µM. The incubation, filtration, and counting procedures were equiv-
alent to those described for the rat radioreceptor assay. The results are
expressed as percent inhibition (% I) and represent the mean of duplicate
tubes at the tested concentration of 1 µM in a single experiment.
PANLABS Assay. Receptor binding affinities for dopamine D4.4
and serotonin 5-HT2A were determined by PANLABS (Taiwan) for
selected compounds. The assays were carried out using the follow-
ing: (a) for D4.4; human recombinant (mammalian CHO-K1 cells),
[3H]spiperone (0.3 nM) as radioligand, and haloperidol (10 µM) as
reference compound for non-specific binding; (b) for 5-HT2A; rat
brain, [3H]ketanserin (0.5 nM) as radioligand, and ketanserin (1 µM)
as reference compound for non-specific binding. Test compounds were
evaluated as hydrochloride salts at a final concentration of 1 µM for
their ability to displace the radioligand. Biochemical assay results are
presented as percent inhibition (% I) of specific binding.
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[m.c.s. (apomorphine) − m.c.s. (drug)]
% Inhibition Climbing =
×100
(1)
m.c.s. (apomorphine)
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Acknowledgments
The authors gratefully acknowledge W. Lau, P. J. Borg, and
N. Jones for the in vitro and in vivo pharmacology testing