Synthesis and evaluation of the structural elements in alkylated tetrahydroisoquinolines for binding to CNS receptors

Article abstract of DOI:10.1016/j.bmc.2016.09.019

Diseases of the CNS are often complex and involve multiple receptor systems and thus, the treatment options for these diseases must focus on targeting the multiple receptors implicated in the various disorders. Schizophrenia and depression are examples of such diseases and their pharmacotherapy thus depends on agents which target multiple receptors including the dopamine, serotonin and even cholinergic receptors at the same time. In our previous campaign to find multi-receptor ligands, we have identified the benzothiazole 1a as an initial lead molecule. In the current work, we have expanded the structure affinity relationship (SAFIR) of 1a resulting in the identification of a partially restrained butyrophenone 3j as a potent and selective dual 5-HT_1Aand 5-HT₇receptor ligand. It is expected that compound 3j may serve as a new lead for further development in our search for newer and novel ligands with the potential to treat diseases of CNS origin.

Full text of DOI:10.1016/j.bmc.2016.09.019

Accepted Manuscript
Synthesis and evaluation of the structural elements in alkylated tetrahydroiso-
quinolines for binding to CNS receptors
Edward Ofori, Xue Y. Zhu, Jagan R. Etukala, Barbara A. Bricker, Seth Y.
Ablordeppey
PII:
S0968-0896(16)30706-4
DOI:
http://dx.doi.org/10.1016/j.bmc.2016.09.019
BMC 13272
Reference:
Bioorganic & Medicinal Chemistry
To appear in:
Received Date:
Revised Date:
Accepted Date:
11 July 2016
26 August 2016
8 September 2016
Please cite this article as: Ofori, E., Zhu, X.Y., Etukala, J.R., Bricker, B.A., Ablordeppey, S.Y., Synthesis and
evaluation of the structural elements in alkylated tetrahydroisoquinolines for binding to CNS receptors, Bioorganic
& Medicinal Chemistry (2016), doi: http://dx.doi.org/10.1016/j.bmc.2016.09.019
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Synthesis and evaluation of the structural elements in alkylated tetrahydroisoquinolines for binding
to CNS receptors
Edward Ofori, Xue Y. Zhu, Jagan R. Etukala, Barbara A. Bricker, Seth Y. Ablordeppey*
Division of Basic Pharmaceutical Sciences, Florida A&M University, College of Pharmacy and
Pharmaceutical Sciences, Tallahassee, FL 32307, USA
Abstract
Diseases of the CNS are often complex and involve multiple receptor systems and thus, the treatment
options for these diseases must focus on targeting the multiple receptors implicated in the various
disorders. Schizophrenia and depression are examples of such diseases and their pharmacotherapy thus
depends on agents which target multiple receptors including the dopamine, serotonin and even cholinergic
receptors at the same time. In our previous campaign to find multi-receptor ligands, we have identified the
benzothiazole 1a as an initial lead molecule. In the current work, we have expanded the structure affinity
relationship (SAFIR) of 1a resulting in the identification of a partially restrained butyrophenone 3j as a
potent and selective dual 5-HT1A and 5-HT7 receptor ligand. It is expected that compound 3j may serve as a
new lead for further development in our search for newer and novel ligands with the potential to treat
diseases of CNS origin.
*Corresponding Author
Key words: Structure affinity relationship, CNS ligands, antipsychotic, multi-receptor ligands, dual
receptor ligands

1. Introduction
Over the years, it has become evident that pharmacotherapy of major CNS diseases such as depression,
bipolar disorder, schizophrenia and anxiety disorders rely on drugs which target multiple CNS receptors
simultaneously.1, 2 For instance, the superior efficacy and improved side effect profiles of atypical
antipsychotics such as lurasidone, ziprasidone and aripiprazole, have been attributed to their broad
spectrum of activities involving dopaminergic, serotonergic and even cholinergic neurotransmission.3 In
the same way, antidepressants such as vilazodone, that target the reuptake of serotonin (5-HT) along with
the 5-HT1A receptor are known to be fast acting, efficacious and tolerable.4, 5 However, a more defined
combination of pharmacological activities at these and other targets is desirable for such agents to offer
optimum therapeutic benefits in treating diseases of CNS origin.
It is now well established that targeting the D2-like receptors (D2, D3 and D4, antagonists), 5-HT1A
(agonists), 5-HT2A (antagonists) and 5-HT7 (antagonists) are desirable features in the pharmacotherapy for
schizophrenia.6, 7 On the other hand, antidepressants may benefit from targeting the serotonin transporter
(SERT), along with 5-HT1AR (agonist) and 5-HT7R (antagonist) for an improved profile.8-10 And now with
the introduction of the D2R partial agonist and functionally selective aripiprazole as a well-tolerated and
effective antipsychotic, the drug development paradigm for schizophrenia has significantly shifted in a new
and exciting direction.11 The caveat for multiple receptor targeting has been that it may also lead to off-
target activities that may culminate in unforeseen side effects. Therefore, as part of our drug design
strategy, there is also a focus on evaluating synthetic compounds at culprit receptors including the 5-HT2B,
receptors associated with valvular heart disease,12 and the 5-HT2C and H1 weight gain and sedation side
effects.13-14
N-alkylated tetrahydroisoquinolines have been at the center of discussion recently as key ligands for certain
CNS receptors associated with major brain disorders.15-17 We have previously reported that the
tetrahydroisoquinoline (THIQ) moiety, appropriately substituted with arylalkyl groups such as
benzothiazole alkyl groups or halobutyrophenones could produce agents that provide differential binding
profiles at clinically relevant CNS receptors including serotonin (5-HT) and dopamine (DA) receptor
subtypes.18, 19 In this manuscript, we further explore changes in three segments (A, B and C) of compound

1a (Figure 1) in order to understand the structure-affinity relationships (SAFIRs) associated with this lead
molecule.
Figure 1. Structures of the benzothiazole hit compounds depicting the various segments of modification.
2. Chemistry
Compounds 1a and 1c were previously reported.18 Compound 1b was prepared by coupling 2-(3-
chloropropyl)benzo[d]thiazole (A) previously reported by us18,20-21 (Figure 2) to 1,2,3,4-tetrahydro-
isoquinoline (THIQ) under the general alkylation condition B (4.1.2) that used K2CO3 as the base, KI as a
catalyst and either acetonitrile (CH3CN) or dimethoxyethane (DME) as the refluxing solvent. Alkylating
agent C was synthesized according to a modified literature method22 outlined in Scheme 1 and was reacted
with THIQ to afford compound 1d (Scheme 2). Compound 1e was prepared in a similar manner as 1b
except that 8-chloro-1,2,3,4-tetrahydroisoquinoline was used in place of THIQ, and B was the alkylating
agent. The alkylating agent D was obtained using a similar approach as was used to obtain alkylating
agents A and B and was reacted with the various amines (THIQ, aromatic substituted THIQs and
decahydroisoquinoline) as depicted in Scheme 2 to afford the corresponding compounds 1f-i.
Figure 2. Alkylating agents used in the syntheses of compounds in group 1 (1a – i).
To synthesize the indene 2a and the 1,2-dihydronaphthalene analog, 2b in group 2, the alkylating agents 14
and 15 were prepared following a four-step procedure (Scheme 3). First, the commercially available
indanone 6 and the α-tetralone 7 were separately refluxed with glyoxylic acid in an aqueous acid in a cross-

aldol condensation reaction to produce the α,β-unsaturated ketones 8 and 9 respectively. The α,β-
unsaturated keto function in 8 and 9 was then reduced using a palladium-carbon catalyzed hydrogenation
reaction to afford the corresponding keto-acids 10 and 11 which were subsequently converted to the
alcohols 12 and 13 under reductive conditions using LiAlH4. The primary hydroxyl group was converted to
an iodo group under Appel reaction conditions.23 Interestingly, the Appel reaction also led to the generation
of a styrene-like double bond seen in intermediates 14 and 15 (Scheme 3).
The bis-p-chlorobenzene alkylating agent 19 used to prepare compound 2c was serendipitously isolated in
a previous attempt to form intermediate 17 from a reaction of the commercially available Grignard reagent
16 and 4-chlorobutyryl chloride (Scheme 4). A plausible mechanism to explain the formation of this
product is that the intended product 17 underwent further 1,2 addition of the Grignard reagent (4-
chlorophenyl)magnesium chloride (16) to the carbonyl function to generate the tertiary alcohol 18 that
dehydrated in the presence of MgCl2 acting as a Lewis acid (catalyst) to produce 19. The isolated
alkylating agent 19 was then coupled to THIQ under the general alkylation condition B to afford 2c
(Scheme 4). In Scheme 5, the dimethylglutarimide analogs 2d and 2e were obtained through a simple two-
step reaction. Commercially available dimethylglutarimide 20 was N-alkylated using dibromobutane and
the resulting alkylbromide 21 coupled separately to THIQ and isoindoline to afford compounds 2d and 2e
respectively (Scheme 5).
Compounds 3c-f were obtained via a one-step N-alkylation with the commercially available 4-chloro-1-(4-
chlorophenyl)butane-1-one,.22 of the various amines (tetrahydroquinoline and tetrahydrobenzazepines) as
depicted in Scheme 6. To prepare compound 3g, oxindole 23 was acylated under Friedel-Crafts acylation
conditions to obtain the ketone 24 which was subsequently used to react with THIQ to obtain compound 3g
(Scheme 7). Preparation of compounds 3c-g and 3i utilized microwave heating (general alkylation method
A) that led to reduced reaction time (up to 60 min) and higher yields compared to conventional heating
(general alkylation method B) (24-48 h). Compounds 3h-j were prepared by N-alkylating THIQ using the
indanone alkylating agents 25-27 previously reported by our lab (Scheme 8).20, 21
Scheme 1. Synthesis of alkylating agent C. Reagents and conditions: 5N HCl, reflux.

Scheme 2. Synthesis of compounds in Group 1. Reagents and conditions: i) K2CO3 (Et3N for 1d), KI,
DME, CH3CN, or DMF (for 1d), reflux or rt (for 1d), 12-18h.; ii) ethereal HCl or HBr.

Scheme 3. Synthesis of the indene and dialin derivatives of THIQ. Reagents and conditions: i) glyoxylic
acid, H2SO4-H2O (1:4), dioxane, reflux; ii) Pd/C (H2), 40 psi, 48h; iii) LiAlH4, toluene/ether, reflux ; iv)
PPh3, I2, imidazole, DCM; v) K2CO3, KI, CH3CN, reflux.
Scheme 4. Synthesis of bis-p-chlorophenyl analog of THIQ. Reagents and conditions: i) 4-chlorobutyryl
chloride, dry THF, rt; ii) THIQ, K2CO3, KI, DME; iii) ethereal HBr.
Scheme 5. Synthesis of dimethylglutarimide analogs of THIQ. Reagents and conditions: i) 1,4-
dibromobutane, CH3CN, reflux; ii) amine (THIQ for 2d, and isoindoline for 2e), K2CO3, CH3CN,
reflux; iii) ethereal HCl.

Scheme 6. Synthesis of p-chlorobutyrophenone analogs. Reagents and conditions: i) appropriate amine,
K2CO3, KI, DME, MW; ii) ethereal HCl.
Scheme 7. Synthesis of the oxindole analog of THIQ. Reagents and conditions: i) 4-chlorobutyryl
chloride, AlCl3, CS2, 0°-rt; ii) THIQ, K2CO3, KI, DME, MW.
Scheme 8. Synthesis of indanone analogs of THIQ. Reagents and conditions: i) THIQ, K2CO3, KI,
toluene, MW (for 3i) or reflux (for 3h and 3j); ii) ethereal HCl for 3i and 3j.
3. Results and discussion

2-(4-(3,4-Dihydroisoquinolin-2(1H)-yl)butyl)benzo[d]thiazole (compound 1a) was previously reported18
and serves as a lead compound for modification to better understand the structure affinity relationship
(SAFIR) associated with binding to key CNS receptors. The binding affinity data of compound 1a at the
D2-like receptors (Ki : D2 = 167 nM, D3 = 8.7 nM and D4 = 67 nM), 5-HT1A (Ki = 10 nM) and the 5-
HT7 receptor (Ki = 22 nM) are reported in Table 1. To this end, we embarked on an SAFIR study to
explore the effect of structural changes in the benzothiazole moiety (segment A), the alkyl linker
(segment B), and the tetrahydroisoquinoline moiety (segment C) of 1a on binding affinity at the various
CNS receptors. This study led to the generation of three structural types of compounds, the
benzothiazoles, cycloalkyl/cycloalkylamines and butyrophenone analogs classified as group 1, 2, and 3
agents respectively, which will be the focus of this discussion.
Shortening the butyl linker in segment B of 1a to a three-carbon chain (1b), led to a lower affinity for all
the DA and 5-HT receptors investigated except at the D4 receptor where a moderate increase in affinity
was observed. Replacing the THIQ ring in 1a with isoindoline (1c) also resulted in decreased binding
affinity to all the receptors under consideration. Compound 1d was prepared to explore the effect of
replacing benzothiazole moiety (segment A) of compound 1b with benzimidazole on binding affinity.
The binding data suggest that the benzothiazole was preferred at all the receptors evaluated. Thus, the
data on compounds 1a -d suggests a benzothiazole with a 4-carbon spacer attached to THIQ is preferred
for the DA and 5-HT receptors explored.
Compound 1e, with an 8-chloro substitution on segment C of 1a did not result in significant changes in
binding affinities suggesting substitution on the THIQ ring is tolerated at least at the 8-position.
Similarly, a 5-chloro substitution on the benzothiazole moiety (1f) was tolerated at all the receptors
except for the D3 and D4 receptors. However, substituting the same substituents simultaneously on the
benzothiazole and the THIQ moieties (1g) resulted in diminished affinities for all the receptors.
Compound 1h was synthesized to explore the need for the aromatic ring in THIQ for binding to the
receptors under consideration. While the D2 and D3 receptors suffered significant reductions in affinity,
the 5-HT1A, 5-HT2A, 5-HT2C and 5-HT7 were essentially unaffected. Similarly, introducing the 9,10-
dimethoxy group on 1f to form 1i, ill-affected binding affinity to the D2-like receptors but not the
serotonin receptors under consideration. It is worth noting that none of the benzothiazole analogs
displayed high affinity Ki values for the "culprit" receptors H1 and 5-HT2C which have been associated
with metabolic and sedative side effects.12-14 On the other hand, there is high affinity binding and
significant variability in the binding to the 5-HT2B receptors with a range of 7.0 – 327 nM.
To further evaluate the structural requirements for segment A/B binding affinity, we synthesized four
analogs, 2a – d and the binding affinity constants are reported in Table 2. Compounds 2a and 2b can be
viewed as partially restricted butyl spacers using cyclopentene and cyclohexene rings. Both compounds
displayed diminished binding affinity for the D2R and showed no definitive trends at other clinically
relevant receptors. Compound 2c, 2d and 2e generally showed no significant binding affinities for any
of the receptors under consideration.

Compounds with the butyrophenone alkyl group (group 3) are analogs of either compound 3a or 3b
previously reported by us.19 Inspired by the promising binding affinity profiles of these butyrophenones
at the relevant CNS receptors (Table 3), we embarked on an exploration to further understand the
SAFIR of these compounds. To begin with, we sought to understand the role of the position of the
nitrogen in segment C. The THIQ moiety in 3b was replaced with tetrahydroquinoline and 2,3,4,5-
tetrahydro-1H-benzo[b]azepine to produce compounds 3c and 3d respectively, resulting in the formation
of aromatic nitrogen atoms in both analogs. Significantly, this change resulted in no apparent receptor
binding affinity at the selected CNS receptors. This observation will lead one to speculate that an
aliphatic nitrogen atom with a higher pKa is more desirable in these compounds for binding to the
receptors. Alternatively, the positioning of the nitrogen atom proximal to the phenyl ring may have
prevented optimal interaction with the complementary functional group at the receptors. Compounds 3e
and 3f were synthesized to further explore the above trains of thought. Thus, moving the nitrogen away
from a direct interaction with the phenyl ring resulted in a minor improvement in the binding potencies
at the DA and 5-HT receptor subtypes when compared to 3c and 3d but fell way short of the original
affinities seen with 3b. Replacing the 4-chlorophenyl group with an oxindole bicyclic moiety to form 3g
produced no significant improvements in binding affinity at the various receptors.
Compounds 3h-3j were the partially restrained analogs of the butyrophenone analogs 3a or 3b.
Restricting the keto group into an indanone led to some rather interesting observations as reported in
Table 3. First, compound 3h, the restrained analog of 3a, records over 15-fold decrease in potency at the
D2R (Ki = 750 nM), compared to 3a (Ki = 49 nM), retained activity at the 5-HT1A (Ki = 19 nM) and an
awe-inspiring low nanomolar binding affinity at the 5-HT7 receptor (Ki = 1.6 nM). This is of biological
significance because of the paucity of selective dual 5-HT1A and 5-HT7 receptor ligands in the
literature.24 Also, a growing body of knowledge suggests that the 5-HT7 receptor controls normal
circadian rhythm, sleep, mood, memory and learning, and cognition25-27 and may therefore serve as a
plausible target for treating neuropsychiatric disorders such as schizophrenia and mood disorders.
Having obtained 3h as a possible lead, we investigated the effect of removing the fluoro group in 3h to
produce compound 3i. This resulted in over 165-fold decrease in binding affinity at the 5-HT7 receptor
which suggested that a halo-phenyl moiety may be required for this 5-HT7 affinity. Further confirmation
of this thought was observed by replacing the fluoro atom with a chloro atom to form compound 3j with
a sub-nanomolar binding affinity constant (Ki = 0.5 nM) at the 5-HT7 receptor. Compound 3j compares
favorably with the binding affinity of SB269970 (pKi = 1.3 nM), the selective 5-HT7 antagonist, albeit it
has a dual binding affinity profile.28 Similarly, when compared to the most potent analogs from
modifications to the lead compound, UCM-560029 and a recently reported arylindole series,1-
(naphthyl)indole derivative 3p,30 compound 3j is about 9 to14-fold more potent at the 5-HT7 receptor
and over 4 to 10-fold higher affinity at the 5-HT1A receptor. Overall, the binding affinity constants of the
indanone analogs fared poorly at the D2-like receptors as well as the culprit 5-HT receptors.
In conclusion, beginning with compound 1a as an initial lead molecule of the benzothiazole series, we
have obtained several alkylated THIQ analogs with potent and desirable multi-receptor binding features

especially at the 5-HT1A and 5-HT7 receptors. The 5-chloro-indanone analog 3j, displaying low
nanomolar and a sub-nanomolar affinity values at the 5-HT1A and the 5-HT7 receptors respectively, is an
addition to the rather scarce group of dual 5-HT1A and 5-HT7 receptor selective ligands in the literature
that can be used to probe the role of these receptors in treating the affective and cognitive diseases of
CNS origin.

Table 1
Group 1 analogs and their binding affinity constants at clinically relevant CNS receptors
Compd
Ki (nM)
Structure
(pKi±SEM)
D2
167
D3
8.7
D4
67.0
5-HT1A
10.0
5-HT2A
1681
5-HT7
22.0
5-HT2B
18.0
5-HT2C
H1
583
910
(6.78±0.09)
(8.5±0.1) (7.17±0.05)
(8±0.03)
(5.77±0.06) (7.66±0.06)
(7.74±0.05)
(6.04±0.04) (6.23±0.08)
1a*
1b
MTA
80.0 41.0
(7.1±0.10) (7.39±0.04) (7.02±0.03) (5.69±0.06) (7.43±0.07)
95.0
2051 37.0
18.0
(7.74±0.04)
1182
822
(5.93±0.05) (6.09±0.08)
990
(6±0.04)
259
141
111
>10,000
>10K
258
211
(6.68±0.08)
135
(6.87±0.06)
MTA
>10K
675
762
(6.12±0.08)
(6.59±0.06) 6.85±0.07 (6.95±0.07)
1c*
1d
915.0
6.09±0.09
2176
5.66±0.07
127.0
6.9±0.07
65.0
7.19±0.07
91.0
7.04±0.04
MTA
290 ± 40
272
31.0
129
29.0
45.0
239
293
(6.57±0.08) (7.52±0.04) (6.89±0.08) (7.53±0.08)
(6.6±0.10) (7.35±0.04)
(6.62±0.08)
(6.17±0.09) (6.53±0.08)
1e
138
447
572
15.0
702
25.0
16.0
759
247
(6.86±0.08) (6.35±0.07) (6.24±0.09) (7.84±0.07)
(6.2±0.10)
(7.6±0.09)
(7.81±0.07)
(6.12±0.08) (6.61±0.06)
1f
853
91.0
279
42.0
483
144
327
820
560
(6.07±0.08) (7.04±0.05) (6.55±0.08) (7.38±0.08)
(6.3±0.1)
(6.84±0.04)
(6.49±0.09)
(6.09±0.09) (6.25±0.07)
1g
1h
1i
1087
526
37.0
11.0
1144
44.0
64.0
(7.19±0.09)
501
268
(5.96±0.08) (6.28±0.08) (7.43±0.06) (7.93±0.06)
(5.9±0.10) (7.36±0.07)
(6.3±0.07
(6.57±0.06)
418
1083
272
9.9
667
(6.2±0.1)
67.0
(7.17±0.06)
7.0
(8.15±0.08)
329
327
(6.38±0.09) (5.97±0.07) (6.57±0.07)
(8±0.05)
(6.48±0.08) (6.49±0.08)
MTA = Missed 50% of threshold inhibition.
* Binding affinity data from 18

Table 2
Compounds in group 2 and their binding affinity constants at relevant CNS receptors
Ki (nM)*
Compd
Structure
(pKi ± SEM)
D2
D3
D4
5-HT1A
1,109
5-HT2A
5-HT7
132
5-HT2B
5-HT2C
MTA
H1
88.0
194
149
(6.83±0.07)
MTA
1,867
(5.73±0.04)
MTA
2a
2b
2c
(7.05±0.09) (6.71± 0.04) (5.96 ±0.08)
(6.88±0.07)
5,647
184
140
138
975
65.0
126
(6.9±0.04)
2,903
1437
(5.25±0.06) (6.73±0.04) (6.85±0.05) (6.86 ±0.04) (6.01 ± 0.09) (7.18 ± 0.07)
(5.54 ± 0.07) (5.84 ± 0.07)
MTA
MTA
150
(6.8 ± 0.1)
MTA
MTA
MTA
MTA
MTA
497
MTA
MTA
2,028
998
(6.3±0.07)
(5.69±0.05) (6 ± 0.07)
1,645
(5.8 ± 0.1)
MTA
MTA
MTA
305
MTA
3,867
2d
2e
2,933
(5.53±0.09)
339
(6.47±0.07)
>10,000
739
531
(6.28±0.07)
>10,000
>10,000
(8.2 ± 0.1)
(6.53±0.07) (5.41±0.07)
MTA = Missed 50% of threshold inhibition.
Table 3
Compounds in group 3 and their binding affinity at clinically relevant CNS receptors
Ki(nM)
Comp Structure
d
(pKi ± SEM)
D2
D3
D4
5-HT1A
19.5
5-HT2A
5-HT7
5-HT2B
519
5-HT2C
H1
49.0 ±3.0
72.0 ±5.0
2.3 ±0.2
21.0
381
>10,000
86.3± 7.3
3a*
*
3b*
*
126
(6.9±0.06)
86.0
8.2
3.6
232
(6.63±0.07)
2,976
(5.53±0.06)
597
(6.22±0.05)
(7.07±0.04) (8.09±0.07)
(8.45±0.07)
17.0
(7.77±0.04)
MTA
3c

MTA
MTA
MTA
MTA
MTA
MTA
MTA
MTA
MTA
>10,000
MTA
MTA
MTA
3d
MTA
3,578
MTA
342
MTA
442
MTA
1,712
MTA
120
257
(6.59±0.05)
138
(6.68±0.05)
127
501
(6.3±0.05)
549
(6.26±0.05)
483
348
(6.46±0.04)
611
(6.21±0.07)
4,234
3,224
(5.5±0.1)
1,087
(6±0.3)
MTA
3e
3f
3g
3h
3i
(5.45±0.08) (6.47±0.04) (6.35±0.04) (5.77±0.07) (6.92±0.03)
1,170 106 82 214 281
(5.93±0.08 (6.97±0.04) (7.09±0.04) (6.67±0.06) (6.55±0.03)
5,399 66 3,335 122 1,022
(5.27±0.09) (7.18±0.04) (5.48±0.04) (6.91±0.07) (5.99±0.03)
(6.9±0.05)
1.6
(6.32±0.05)
(5.37±0.09)
MTA
750
223
251
19.0
1,204
ND
(6.12±0.07) (6.65±0.04)
(6.6±0.06)
(7.73±0.04) (5.92±0.09)
(8.8±0.06)
294
391
1,184
(5.93±0.06)
128
24
(7.6±0.1)
553
2,583.5
946
866.0
783
1,102
48.3
391.3
265
50
16
748
0.5
(9.33±0.06)
1.3
8.9±0.1
7±2
109
(6.96±0.07)
3j
(6.02±0.08) (6.11±0.07)
(7.3±0.06)
(7.81±0.06)
(6.1±0.1)
(6.89±0.08) (6.26±0.06)
aSB269970
bCompound 18
cCompound 3p
ND
ND
ND
<5
<5
5
<5
ND
ND
ND
ND
ND
ND
ND
219±11
70±12
ND
ND
ND
ND
ND
ND
ND
ND
4.5±1
MTA = Missed 50% of threshold inhibition, ND = Not determined.
* Ki values without the associated SEM, are within 20% of the mean value. ** Binding affinity data from reference 19.
b
aBinding affinity data from reference 28. Binding affinity data from reference 29; cBinding affinity data from reference 30

4. Experimental
Melting points of final compounds were determined on a Gallenkamp (UK) apparatus and are reported
as uncorrected. All NMR spectra were obtained on a Varian 300 MHz Mercury Spectrometer and the
free induction decay (FID) data were processed using Mestrelab’s Mnova NMR software (version 8.1)
to obtain the reported NMR data. Elemental analyses were carried out by Atlantic Microlab, Inc.,
Norcross, GA, and are within 0.4% of theory unless otherwise stated. Flash chromatography was
performed using CombiFlash® with Davisil grade 634 silica gel. Starting materials were obtained from
Sigma–Aldrich or Matrix scientific and were used without further purification. All microwave assisted
syntheses (MW) were carried out using a Biotage Initiator®.
4.1.1 General alkylation procedure A
A mixture of alkylating agent (1 equiv), appropriate amine (1.1 equiv) K2CO3 (1.1 equiv), and KI
(catalytic) in DME or CH3CN (10 mL) was placed in a 20 mL microwave vial (for MW) with a stirrer
o
and tightly sealed. The mixture was subjected to microwave (MW) heating at 120 C for 60 mins. The
resulting crude mixture was directly purified on silica gel by flash chromatography (gradient up to 70%
EtOAc in hexanes) to afford the final compounds. The free base where necessary, was converted to the
HCl or HBr salt and crystallized out of a mixture of MeOH-Et2O.
4.1.2 General alkylation procedure B
A mixture of alkylating agent (1 equiv), appropriate amine (1.1 equiv) K2CO3 (1.1 equiv), and KI
(catalytic) in DME or CH3CN (50 mL) was placed in a round bottomed flask with a stirrer was heated to
reflux on a heating plate for 24-28 h. The reaction was monitored by TLC for product formation. After
reaction was complete, the resulting crude mixture was directly purified on silica gel by flash
chromatography (gradient up to 70% EtOAc in hexanes) to afford the final compounds. The free base
where necessary, was converted to the HCl or HBr salt and crystallized out of a mixture of MeOH-Et2O.
4.2. Synthesis of Compounds
4.2.1. 2-(3-(3,4-Dihydroisoquinolin-2(1H)-yl)propyl)benzo[d]thiazole hydrobromide, 1b
Previously reported alkylating agent 2-(3-chloropropyl)benzo[d]thiazole18 was reacted with THIQ under
the general alkylation conditions B (4.1.2) described above to produce the hygroscopic compound 1b as
1
the HBr salt in 20% yield. H NMR (DMSO-d6): 9.96 (brs, 1H), 8.08 (d, J = 7.5 Hz, 1H), 7.93 (d, J =
7.5 Hz, 1H), 7.50 (t, J = 7.5 Hz, 1H), 7.42 (t, J = 7.5 Hz, 1H), 7.20-7.30 (m, 4H), 4.61 (d, J = 13.8 Hz,
1H), 4.34 (dd, J = 7.8, 15.6 Hz, 1H), 3.74-3.79 (m, 1H), 3.34-3.42 (m, 3H), 3.23-3..28 (m, 2H), 3.02-
3.18 (m, 2H), 2.30-2.40 (m, 2H). Anal. calcd for C19H22Br2N2S: C 48.53, H 4.72, N 5.96. Found: C
48.61, H 4.72, N 5.89.
4.2.2. 2-(3-Chloro-propyl)-1H-benzoimidazole, D
To a mixture of 1,2-diaminobenzene,4 (0.5g, 4.6 mmol) and 4-chlorobutanoic acid,5 (0.86 g, 7 mmol) in
a schlenk tube was added 5N HCl solution (25 mL) and heated to boil for 5 h. The reaction mixture was

then cooled and added to water (25 mL). The precipitate obtained was filtered and vacuum dried to give
a white solid (1.25 g, 56%) which was used in the next step without further purification.
4.2.3. 2-(3-(1H-benzo[d]imidazol-2-yl)propyl)-1,2,3,4-tetrahydroisoquinoline, 1d
A mixture of 2-(3-chloro-propyl)-1H-benzoimidazole, D, (1.2 g, 6.15 mmol), THIQ (1.2 g, 9.0 mmol),
KI (100 mg) and Et3N (4 mL, 28.5 mmol) in DMF (5 mL) was stirred for 56 h at room temperature (rt).
The mixture was diluted with EtOAc (200 mL), washed with brine (3 × 50 mL). The organic layer was
dried over Na2SO4, and filtered. The filtrate was concentrated in vacuo to dry and followed by column
chromatography on silica gel to afford 2-[3-(1H-benzoimidazol-2-yl)-propyl]-1,2,3,4-tetrahydro-
isoquinoline, 1d as the HCl salt (0.32 g ,14%) and crystallized from MeOH-Et2O mixture. Mp: 234-235
ºC; 1H NMR (DMSO-d6): 7.77 (m, 2H), 7.50 (m, 2H), 7.22 (m, 4H), 4.45 (brs, 2H), 3.52 (brs, 2H), 3.34
(m, 4H), 3.15 (brs, 2H), 2.52 (m, 2H). Anal calcd for C19H23Cl2N3•0.3H2O: C 61.72, H 6.27, N 11.37.
Found: C 61.40, H 6.48, N 11.35.
4.2.4. 2-(4-(8-Chloro-3,4-dihydroisoquinolin-2(1H)-yl)butyl)benzo[d]thiazole hydrochloride, 1e
Using the previously reported alkylating agent 2-(4-chlorobutyl)-benzo[d]thiazole,18 the amine 8-chloro-
1,2,3,4-tetrahydroisoquinoline was N-alkylated under the general alkylation reaction condition B,
1
described above to produce compound 1e as a white HCl salt in 45% yield. Mp: 192-194 °C. HNMR
(300 MHz, DMSO-d6): δ 11.01 (brs, 1H), 8.19 (d, J = 7.8 Hz, 1H), 8.07 (d, J = 7.8 Hz,1H), 7.62-7.54
(m, 3H), 7.45 (t, J = 6.9 Hz, 1H), 7.35 (d, J = 7.8 Hz, 1H), 5.05-4.95 (m, 1H), 4.69 (d, J = 1.5 Hz, 1H),
4.47-4.40 (m, 1H), 3.89-3.85 (m, 1H), 3.48-3.32 (m, 4H), 3.22 (t, J = 5.1 Hz, 2H), 2.05 (s, 4H). Anal.
calcd for; C20H22Cl2N2S•0.9.H2O: C 58.65, H; 5.41, N; 6.84, Found; C; 58.43, H; 5.81, N; 6.36.
4.2.5. Alkylating agent, 5-Chloro-2-(4-chlorobutyl)benzo[d]thiazole, C
Using similar cyclization reaction procedure previously described by us,18 2-amino-4-
chlorobenzenethiol was reacted with 5-chloropentanoyl chloride in toluene at rt to afford alkylating
1
agent C (see ref18 for details). H NMR (300 MHz, CDCl3): δ 7.85 (d, J = 2.1 Hz, 1H), 7.75 (d, J = 8.1
Hz, 1H), 7.34(dd, J = 1.8 Hz, 6.6 Hz, 1H), 3.59 (t, J = 6.6 Hz, 2H), 3.15 (t, J = 7.2 Hz, 2H), 2.08-2.01
(m, 2H), 1.96-1.89(m, 2H).
4.2.6. 5-Chloro-2-(4-(3,4-dihydroisoquinolin-2(1H)-yl)butyl)benzo[d]thiazole hydrochloride, 1f
Alkylating agent C was reacted with THIQ under the general alkylation condition B described above to
1
afford compound 1f as the HCl salt in 75% yield. Mp: 229-231 °C, H NMR (300 MHz, DMSO-d6): δ
10.68 (s, 1H), 8.10 (d, J = 8.4 Hz, 1H), 8.00 (d, J = 1.5 Hz,1H), 7.47-7.44 (dd, J = 2.1, 8.4 Hz, 1H),
7.27-7.17 (m, 4H), 4.52-4.47 9d, J = 15.6 Hz, 1H), 4.28-4.21 (dd, J = 7.8, 15.3 Hz, 1H), 3.70-3.64 (m,
1H), 3.37 (s, 2H), 3.24-3.16 (m, 4H), 3.02-2.97 (m, 1H), 1.96-1.89 (m, 4H). Anal. calcd for
C20H22Cl2N2S: C 61.07, H 5.64, N 7.12. Found: C 60.89, H 5.65, N 6.94.
4.2.7. 5-Chloro-2-(4-(5-chloro-3,4-dihydroisoquinolin-2(1H)-yl)butyl)benzo[d]thiazole hydrochloride,
1g

Using method B of the general alkylation reaction condition, 8-chloro-1,2,3,4-tetrahydroisoquinoline
was N-alkylated with alkylating agent C to afford compound 1g as a white solid HCl salt in 73% yield.
Mp: 218-220°C, 1H NMR (300 MHz, DMSO-d6): δ 11.70 (brs, 1H), 8.08 (d, J = 8.7 Hz, 1H,), 7.99 (d, J
= 2.1 Hz, 1H), 7.47-7.42, (m, 2H), 7.30 (t, J = 7.8 Hz, 1H), 7.19 (d, J = 7.8Hz, 1H), 4.55-4.5 (m, 1H),
4.32-4.24 (m, 1H), 4.02-3.97 (m, 2H), 3.36-3.18 (m, 4H), 3.06 (t, J = 5.1Hz, 2H), 1.89 (s, 4H). Anal.
calcd for C20H21Cl3N2S•0.24.H2O: C 55.58, H 4.90, N 6.48. Found: C 55.57, H 5.10, N 6.19.
4.2.8. 5-Chloro-2-(4-(octahydroisoquinolin-2(1H)-yl)butyl)benzo[d]thiazole hydrochloride, 1h
General alkylation method B was used. Alkylating agent C was reacted with decahydroisoquinoline to
1
afford compound 1h in 85% yield. Mp: 141-143°C. H NMR (300 MHz, DMSO-d6): δ (9.93 (s, 1H),
8.11-8.08 (d, J = 8.4 Hz, 1H), 8.00 (d, J = 1.8 Hz, 1H), 7.47-7.44 (dd, J = 2.1, 11.4 Hz, 1H) 3.50-3.30
(m, 4H), 3.25 (d, J = 10.2 Hz 1H), 3.18-3.13 (t, J = 7.2 Hz, 2H), 3.06-3.300 (m, 2H), 2.90-2.80 (m, 1H),
1.86-1.78 (m, 4H), 1.70-1.66 (m, 2H), 1.60-1.43 (m, 4H), 1.24-1.18 (t, J = 10.2 Hz, 2H), 1.00-0.87 (t, J
= 12.0 Hz, 2H). Anal. calcd for C20H28Cl2N2S•0.95.H2O: C 57.67, H 6.78, N 6.73. Found: C 57.66, H
7.08, N 6.51.
4.2.9.
5-Chloro-2-(4-(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1H)-yl)butyl)benzo[d]thiazole
hydrochloride, 1i.
Compound 1i in its HCl salt form was prepared similarly to 1h above using 6,7-dimethoxy-1,2,3,4-
tetrahydroisoquinoline as the amine in a 79% yield. Mp: 180-182oC, 1H NMR (300 MHz, DMSO-d6): δ
10.60 (s, 1H), 8.09 (d, J = 9.0 Hz, 1H), 8.00 (d, J = 1.8 Hz, 1H), 7.47-7.44 (dd, J = 2.1, 8.4 Hz, 1H), 6.78
(d, J = 8.4Hz, 2H), 3.80-3.74 (m, 5H), 3.30-3.16 (m, 5H), 1.90-1.86 (m, 4H). Anal. calcd for
C20H28Cl2N2S•0.32EtOAc: C 54.91, H 5.45, N 5.82. Found: C 54.76, H 5.84, N 5.54.
4.2.10. (E)-2-(1-oxo-1H-inden-2(3H)-ylidene)acetic acid, 8
A mixture of 1-indanone, 6 (3 g, 22.7 mmol), glyoxylic acid (50% aqueous solution, 5.9 g, 54.5 mmol),
and conc. H2SO4 (0.74 mL) in dioxane (5 mL) were stirred at refluxing temperature for 12 h. The
mixture was cooled, the product filtered off, washed with water and dried to give the acid (E)-2-(1-oxo-
1H-inden-2(3H)-ylidene) acetic acid (3.68 g, 86.2%) as a white solid. Mp: 202–204 °C (lit. mp 205–206
1
°C), H NMR (300 MHz, DMSO-d6): δ 12.00 (brs, 1H), 7.73–7.80 (m, 2H), 7.68 (d, J = 7.7 Hz, 1H),
7.49 (t, J = 7.9 Hz, 1H), 6.55 (t, J = 2.4 Hz, 1H), 4.08 (d, J = 1.8, 2H).
4.2.11. (E)-2-(1-oxo-3,4-dihydronaphthalen-2(1H)-ylidene)acetic acid, 9
Intermediate 9 was prepared similarly to 8 above using α-tetralone instead of 1-indanone (Scheme 3).
The crude product obtained after filtration was used for the next step without further purification. Yield
1
(3.5 g, 84%). H NMR (300 MHz, DMSO-d6): 12.96 (brs, 1H), 7.95-7.92 (m, 1H), 7.83-7.57(m, 1H),
7.43-7.38(m, 2H), 6.65-6.64(m, 1H), 3.31-3.27(m, 2H), 2.98(t, J = 6.6 Hz, 2H).
4.2.12. 2-(1-oxo-2,3-dihydro-1H-inden-2-yl)acetic acid, 10
(E)-2-(1-oxo-1H-inden-2(3H)-ylidene) acetic acid, 8 (10 g, 53 mmol) in MeOH (45 mL) and dioxane
(150 mL) with Pd/C (10%, 1 g) was stirred under H2 (40 psi) for 48 h. The mixture was filtered through

celite and the solvent evaporated to give 2-(1-oxo-2,3-dihydro-1H-inden-2-yl)acetic acid (7) as an off-
white solid. Mp 85–88°C, 1H NMR (300 MHz, DMSO-d6): δ 8.47 (br s, 1 H, enol OH ), 7.08–7.18 (m, 4
H, H-4, H-5, H-6, H-7), 2.99–3.06 (m, 2 H, H-1, H-3), 2.69–2.74 (m, 1 H, H-2), 2.53–2.60 (m, 2 H, H-1,
H-3), 2.48 (d, J = 7.4 Hz, 2 H, CH2CO2).
4.2.13. 2-(1-hydroxy-3,4-dihydronaphthalen-2-yl)acetic acid, 11
Intermediate 11 was prepared similarly to 10 above using (E)-2-(1-oxo-3,4-dihydronaphthalen-2(1H)-
1
ylidene)acetic acid(9) as the precursor (Scheme 3). H NMR (300 MHz, DMSO-d6): δ 12.13 (brs, 1H),
7.85(d, J = 8.1Hz, 1H), 7.56-7.5(m, 1H), 7.35-7.31(m, 2H), 3.13-3.02(m, 1H), 2.95(m, 2H), 2.74-
2.66(m, 1H), 2.44-2.37(m, 1H), 2.17-2.09(m, 1H), 2.0-1.85(m, 1H).
4.2.14. 2-(2-hydroxyethyl)-2,3-dihydro-1H-inden-1-ol, 12
A solution of 2-(3-Hydroxy-1H-inden-2-yl)acetic acid (3.4 g, 19.8 mmol) in dry THF (100 mL) was
added dropwise to a suspension of LiAlH4 (1.5 g, 39.6 mmol) in dry THF (50 mL) at 0 °C and the
resulting mixture was stirred at refluxing temperature for 12 h. EtOAc was added to quench excess
LiAlH4 and then aqueous HCl solution (10%, 50 mL) was added and the organic fraction separated. The
aqueous solution was extracted with EtOAc (3 × 50 mL), and the combined organic fraction dried and
the solvent evaporated to give alcohol 2-(2-hydroxyethyl)-2,3-dihydro-1H-inden-1-ol (2.18 g) as a
1
yellow oil which was used for the next step without further purification. H NMR (300 MHz, CDCl3): δ
7.43-7.35(m, 1H), 7.26-7.18(m, 3H), 4.9(br d, J = 6.6 Hz, 1H), 3.91-3.73(m, 2H), 3.4(s, 1H), 3.1-
2.92(m, 1H), 2.6-2.46(m, 1H), 2.29-2.2(m, 1H), 1.95-1.86(m, 2H).
4.2.15. 2-(2-hydroxyethyl)-1,2,3,4-tetrahydronaphthalen-1-ol, 13
Synthesis of intermediate 13 followed the same procedure as 12 above and was used for the next step
without further purification.
4.2.16. 2-(2-iodoethyl)-1H-indene, 14
A solution of triphenylphosphine (5.28 g, 20.2 mmol) and imidazole (1.37 gm, 20.2 mmol) in CH2Cl2
was cooled to 0 °C, and iodine (5.09 g, 20.15 mmol) was added. The mixture was stirred for 30 min and
then a CH2Cl2 solution (20 mL) of the crude 2-(2-hydroxyethyl)-1H-inden-3-ol, 12 (2.18 gm, ~13.43
mmol) obtained above was added in a dropwise manner. The reaction mixture was stirred for 12 h at rt,
filtered, the organic layer washed with H2O and then by aqueous sodium thiosulfate (50 mL), H2O 950
mL) and brine 950 mL). The organic layer was dried over sodium sulfate, excess solvent removed under
reduced pressure and the residue purified on combiflash column using EtOAc/hexane (1:9) as eluent to
1
afford 2-(2-iodoethyl)-1H-indene (14) as a brown solid. H NMR (300 MHz, CDCl3): δ 7.4(d, J = 7.5
Hz, 1H), 7.32(d, J = 7.5 Hz, 1H), 7.26-7.21(m, 1H), 7.17-7.11(m, 1H), 6.62(s,1H), 3.4-3.35(m, 4H),
3.11-3.07(m, 2H)
4.2.17. 3-(2-iodoethyl)-1,2-dihydronaphthalene, 15
Under the same Appel reaction conditions described for 14 above, the alkylating agent 15 was prepared
1
in 26% yield using 2-(2-hydroxyethyl)-1,2,3,4-tetrahydronaphthalen-1-ol,13 as the precursor. H NMR

(300 MHz, CDCl3): δ 7.15-7.1(m, 3H), 7.03-7.0(m, 1H), 6.28(s, 1H), 3.31(t, J = 7.8 Hz, 2H), 2.86-
2.75(m, 4H), 2.27(t, J = 8.4, 2H).
4.2.18. 2-(2-(1H-inden-2-yl)ethyl)-1,2,3,4-tetrahydroisoquinoline, 2a
Using method B, the alkylating agent 2-(2-iodoethyl)-1H-indene (11) was used to alkylate THIQ
(section 4.1.2) to afford compound 2a as a white solid in 29% yield. Mp: 87-89 oC, 1H NMR (300 MHz,
CDCl3): δ 7.38 (d, 1H, J = 7.2 Hz), 7.29-7.19 (m, 2H), 7.15-7.02 (m, 5H), 6.59 (s, 1H), 3.74 (s, 2H),
3.38 (s, 2H), 2.95 (t, J = 6.0 Hz, 2H), 2.83 (s, 6H). Anal. calc for C20H21N: C 87.23, H 7.69, N 5.09;
Found: C 86.97, H 7.74, N 4.99.
4.2.19. 2-(2-(3,4-Dihydronaphthalen-2-yl)ethyl)-1,2,3,4-tetrahydroisoquinoline, 2b
Using the alkylating agent 12, THIQ was alkylated under the general alkylation method B to produce
1
compound 2b as a hygroscopic solid in 35% yield, H NMR (300 MHz, CDCl3): δ 7.18-6.96 (m, 8H),
6.29(s, 1H), 3.7(s, 2H), 2.93(t, J = 6 Hz, 2H), 2.86-2.77(m, 4H), 2.76-2.68(m, 2H), 2.51(t, J = 8.7 Hz,
2H), 2.31(t, J = 8.1 Hz, 2H). 13C NMR (75 MHz, CDCl3): δ 140.18, 134.74, 134.39, 134.23, 128.66,
127.18, 126.6, 126.42, 126.2, 126.12, 125.6, 125.38, 123.4, 56.92, 56.16, 51.02, 35.41, 29.14, 28.15,
27.58. Anal. calcd. for C21H23N : C 87.15, H 8.01, N 4.84 ; Found: 87.04, 7.96, 4.78.
4.2.20. 4,4'-(4-Chlorobut-1-ene-1,1-diyl)bis(chlorobenzene), 19
To a solution of 4-chlorobutyryl chloride (5 mL, 44 mmol) in dry THF (50 mL) was added dropwise to a
solution of 4-chlorophenylmagnesium bromide (100 mL, 1.0 M in Et2O, 100 mmol) at -5 °C in 1 hr.
After addition was complete, the reaction mixture was stirred at rt overnight, and then quenched with
saturated NH4Cl solution followed by extraction with EtOAc (400 mL). The organic layer was separated
and washed with brine (2 x 200 mL), then dried with anhydrous Na2SO4 and filtered. The filtrate was
concentrated in vacuo, and the residue purified directly on silica gel using flash chromatography to give
1
the pure product, 4,4'-(4-chlorobut-1-ene-1,1-diyl)bis(chlorobenzene) (19), 9.3 g, yield 68%. H NMR
(300MHz, CDCl3): 7.36 (d, J = 6.0 Hz, 2H), 7.24 (d, J = 6.6 Hz, 2H), 7.12 (d, J = 6.0 Hz, 2H), 7.09 (d, J
= 6.0 Hz, 2H), 6.10 (t, J = 7.2 Hz, 1H), 3.57 (t, J = 6.6 Hz, 2H), 2.56 (m, 2H).
4.2.21. 2-(4,4-Bis(4-chlorophenyl)but-3-en-1-yl)-1,2,3,4-tetrahydroisoquinineol hydrobromide, 2c
Compound 2c was prepared by reacting the alkylation agent 4,4'-(4-chlorobut-1-ene-1,1-
diyl)bis(chlorobenzene) (19) and THIQ under the general alkylation B conditions to afford 2c in 56%
yield. Mp 215-216 °C ,1H NMR (DMSO-d6): 9.69 (brs,1H), 7.51 (d, J = 8.1 Hz, 2H), 7.38 (d, J = 8.1
Hz, 2H), 7.15-7.28 (m, 8H), 6.18 (t, J = 7.5 Hz, 1H), 4.46-4.50 (m, 1H), 4.23-4.31 (m ,1H), 3.61-3.66
(m, 1H), 3.30-3.38 (m, 3H), 3.04-3.09 (m, 2H), 2.53-2.58 (m, 2H). Anal. calcd for C25H24BrCl2N: C
61.37, H 4.94, N 2.86. Found: C 61.33, H 5.05, N 2.95.
4.2.22. 1-(4-bromobutyl)-4,4-dimethylpiperidine-2,6-dione, 21
A mixture of 4,4-dimethylpiperidine-2,6-dione, 20 (0.93 g, 5 mmol) and 1,4-dibromobutane (5.4 g, 25
mmol) was stirred under reflux in dry CH3CN (20 mL) for 12 h. The reaction mixture was allowed to
cool to room temperature and the excess solvent was removed under reduced pressure. The crude
product obtained was directly purified on flash column chromatography (silica gel, ethyl acetate/light
petroleum 1:3) to afford 1-(4-bromobutyl)-4,4-dimethylpiperidine-2,6-dione, (21) as a colorless oil
1
which was used in the next stage without further purification. H NMR (300 MHz, CDCl3): δ 3.8(t, J =
7.2, 2H), 3.42(t, J = 6.6 Hz, 2H), 2.51(s, 4H), 1.91-1.82 (m, 2H), 1.73-1.62(m, 2H), 1.08(s, 6H).

4.2.23.
1-(4-(3,4-Dihydroisoquinolin-2(1H)-yl)butyl)-4,4-dimethylpiperidine-2,6-dione
hydrochloride, 2d
Under the general alkylation method B described above, the alkylating agent 21 was reacted with THIQ
to afford compound 2d as a highly hydroscopic HCl salt in 76% yield. 1HNMR (300 MHz, DMSO-d6): δ
9.82 (brs, 1H), 7.66-7.60 (m, 1H), 7.47-7.38 (m, 2H), 7.15(dd, J = 5.4, 10.8 Hz,1H), 3.59 (t, J = 7.4 Hz,
2H), 3.40 (s, 2H), 2.97 (s, 2H), 2.50 (s, 8H), 1.70-1.60 (m, 2H), 1.35 (t, J = 7.5 Hz, 2H), 9.95 (s, 6H).
Anal. calcd for C20H29ClN2O2. 0.15 EtOAc: C; 63.53, H; 7.73, N; 7.41. Found: C; 63.41, H; 8.10, N;
7.02.
4.2.24. 1-(4-(Isoindolin-2-yl)butyl)-4,4-dimethylpiperidine-2,6-dione, 2e
Using isoindoline as the amine, compound 2e was prepared in its free base form similarly to compound
o
2d above in 23% yield. Mp: 84-85 C, 1HNMR (300 MHz, CDCl3): δ 7.18 (s, 4H), 3.83 (s, 4H), 3.81-
3.75 (t, J = 3.9 Hz, 2H), 2.76-2.71 (t, J = 6.9 Hz, 2H), 2.49 (s, 4H), 1.62-1.58 (t, J = 7.7 Hz, 4H), 1.06 (s,
6H). Anal calcd for C19H26N2O2•0.15 H2O: C 71.96, H 8.26, N 8.83. Found: C 71.93, H 8.25, N 8.81.
4.2.25. Synthesis of compounds 3c-f
In general, compounds 3c-f were synthesized following the general alkylation method A described
above (section 4.1.1) using the common alkylating agent 4-chloro-1-(4-chlorophenyl)butan-1-one (22)
to obtain the respective final compounds as HCl salts, except for 3c which was obtained as a free base
(Scheme 6).
4.2.25.1. 1-(4-Chlorophenyl)-4-(3,4-dihydroquinolin-1(2H)-yl)butan-1-one, 3c
Using 1,2,3,4-tetrahydroquinoline as the amine and 4-chloro-1-(4-chlorophenyl)butan-1-one(22) as the
alkylating agent, compound 3c was produced as a white crystalline solid in 33% yield. Mp: 192-193
ºC.1H NMR (300 MHz, DMSO-d6) δ 7.97 (d, J = 8.3 Hz, 2H), 7.59 (d, J = 8.2 Hz, 2H), 7.07 – 6.91 (m,
2H), 6.85 (d, 1H), 6.66 (d, 1H), 3.38 – 3.25 (m, 4H), 3.11 (t, J = 6.9 Hz, 2H), 2.71 (t, J = 6.2 Hz, 2H),
13
1.97 – 1.83 (m, 4H). C NMR (75MHz, DMSO-d6) δ 198.54, 145.25, 139.46, 135.16, 129.44, 129.22,
128.92, 127.15, 122.34, 115.64, 110.65, 50.64, 49.49, 35.66, 28.15, 22.22, 20.87. Anal. calcd for
C19H20ClNO: C, 72.72; H, 6.42; N, 4.46. Found: C, 72.48; H, 6.30; N, 4.35.
4.2.25.2.
1-(4-Chlorophenyl)-4-(2,3,4,5-tetrahydro-1H-benzo[b]azepin-1-yl)butan-1-one
hydrochloride, 3d
Using 2,3,4,5-tetrahydro-1H-benzo[b]azepine as the amine and reacting it with 22, compound 3d was
obtained as a white crystalline HCl salt. Yield: 35%, mp:192-193 ºC. 1H NMR (300 MHz, Methanol-d4)
δ 7.95 (d, J = 8.1 Hz, 2H), 7.68 (d, J = 7.3 Hz, 1H), 7.54 – 7.35 (m, 5H), 4.86 (t, J = 2.6 Hz, 2H), 4.03 –
3.44 (m, 4H), 3.32 – 3.02 (m, 4H), 2.36 – 1.79 (m, 4H). 13C NMR (75 MHz, CD3OD) δ 197.63, 139.28,
138.80, 136.67, 134.94, 133.19, 130.46, 129.43, 128.59, 127.72, 123.75, 56.70, 52.39, 34.45, 33.51,
25.45, 23.68, 19.47. Anal. calcd for C20H23Cl2NO: C, 65.94; H, 6.36; N, 3.84. Found: C, 65.66; H, 6.41;
N, 3.74.
4.2.25.3.
1-(4-Chlorophenyl)-4-(4,5-dihydro-1H-benzo[c]azepin-2(3H)-yl)butan-1-one
hydrochloride, 3e
Intermediate 22 was used to alkylate the amine 2,3,4,5-tetrahydro-1H-benzo[c]azepine to obtain
compound 3e as a white solid crystal. Yield: 52%, mp: 201-202 ºC. 1H NMR (300 MHz, DMSO-d6) δ

11.24 (s, 1H), 7.93 (d, J = 8.8 Hz, 2H), 7.56 (dd, J = 8.5 Hz, 2H), 7.42 (d, J = 7.3 Hz, 1H), 7.34 – 7.21
(m, 3H), 4.56 (d, J = 14.1 Hz, 1H), 4.38 (dd, J = 5.1, 14.1 Hz, 1H), 3.52 – 3.42 (m, 2H), 3.35 (s, 2H),
3.12 (td, J = 2.4, 6.9 Hz, 2H), 2.88 (t, J = 18.8 Hz, 2H), 2.02 (q, J = 7.6 Hz, 2H), 1.94 – 1.84 (m, 2H).
13C NMR (75 MHz, DMSO-d6) δ 198.15, 143.47, 138.59, 135.44, 132.21, 130.48, 130.25, 129.93,
129.62, 129.24, 127.10, 56.85, 55.95, 35.66, 33.38, 22.40, 18.39. Anal. calcd for C20H23Cl2NO: C,
65.94; H, 6.36; N, 3.84. Found: C, 65.67; H, 6.44; N, 3.72.
4.2.25.4.
1-(4-Chlorophenyl)-4-(4,5-dihydro-1H-benzo[d]azepin-3(2H)-yl)butan-1-one
hydrochloride, 3f
Amine 2,3,4,5-tetrahydro-1H-benzo[d]azepine was reacted with 22 to produce compound 3f as a white
solid crystal. Yield: 59%, mp: 240-242 ºC. 1H NMR (300 MHz, DMSO-d6) δ 11.31 (s, 1H), 7.98 (dd, J =
8.3 Hz, 2H), 7.59 (dd, J = 8.4 Hz, 2H), 7.22 – 7.15 (m, 4H), 3.72 – 3.59 (m, 2H), 3.53 – 3.41 (m, 2H),
3.18 (dt, J = 6.6, 14.4 Hz, 4H), 2.95 (dt, J = 6.8, 16.9 Hz, 4H), 2.09 (q, J = 7.6 Hz, 2H).13C NMR (75
MHz, DMSO-d6) δ 198.18, 139.80, 138.62, 135.52, 130.28, 129.53, 129.29, 127.40, 56.86, 53.70, 35.87,
31.16, 18.34. Anal. calcd for C20H23Cl2NO: C, 65.94; H, 6.36; N, 3.84. Found: C, 65.83; H, 6.44; N,
3.90.
4.2.26. 5-(4-Chlorobutanoyl)indolin-2-one, 24
A modified acylation reaction described by Lackey et al.31 was followed to access intermediate 3b.
Briefly, to a dry 100 mL round-bottomed flask equipped with a stirrer was added 5 g (37.5 mmol) of
AlCl3, 30 mL of carbon disulfide (CS2), and 2.5 mL (22.5 mmol) of 4-chlorobutyryl chloride at 0 °C
with stirring. To the mixture obtained was added 2 g (15 mmol) of oxindole (23) in a portionwise
manner over 20 minutes. After the addition was completed, the reaction mixture was allowed to warm to
rt and stirred overnight to produce a red precipitate. The content was dumped into a beaker containing
100g of ice with 5 mL conc. HCl and stirred thoroughly. The brick red precipitate obtained was
dissolved in methanol and loaded onto silica column and subsequently separated by combiflash
(gradient elution up to 50% EtOAc in hexanes) to afford 2.6 g (73%) of 5-(4-chlorobutanoyl)indolin-2-
1
one, 24. H NMR (300 MHz, DMSO-d6) δ 10.75 (s, 1H), 7.84 (dd, J = 1.9, 8.2 Hz, 1H), 7.78 (s, 1H),
6.88 (d, J = 8.2 Hz, 1H), 3.68 (t, J = 6.7 Hz, 2H), 3.52 (s, 2H), 3.07 (t, J = 7.1 Hz, 2H), 2.03 (q, J = 6.9
Hz, 2H).13C NMR δ 197.83, 177.19, 148.82, 130.53, 129.41, 126.55, 124.52, 109.19, 45.39, 35.95,
35.16, 27.48.
4.2.27. 5-(4-(3,4-Dihydroisoquinolin-2(1H)-yl)butanoyl)indolin-2-one, 3g
Using the alkylating agent 24, THIQ was alkylated under the general alkylation method A condition to
1
afford compound 3g as a free base in 59% yield. Mp: 166-168 ºC. H NMR (300 MHz, CDCl3) δ 9.23
(s, 1H),7.84 (d, J = 4.7 Hz, 1H), 7.87 (d, J = 8.2 Hz, 1H), 7.16 – 6.96 (m, 4H), 6.85 (s, 1H), 3.61 (s, 2H),
3.51 (s, 2H), 3.02 (t, J = 7.2 Hz, 2H), 2.86 (t, J = 5.9 Hz, 2H), 2.75 (t, J = 5.9 Hz, 2H), 2.59 (t, J = 7.1
Hz, 2H), 2.04 (q, J = 7.2 Hz, 2H). 13C NMR (75MHz, CDCl3) δ 199.01, 177.77, 146.77, 134.74, 134.31,
131.90, 129.38, 128.60, 126.55, 126.11, 125.57, 125.34, 124.63, 109.16, 57.34, 55.97, 50.78, 35.97,
35.90, 29.01, 21.92. Anal. Calcd for C21H22N2O2: C, 75.42; H, 6.63; N, 8.38; Found: C, 75.12; H, 6.74;
N, 8.16.
4.2.28. 2-(2-(3,4-Dihydroisoquinolin-2(1H)-yl)ethyl)-5-fluoro-2,3-dihydro-1H-inden-1-one, 3h.
Using the previously reported alkylating agent 2-(2-chloroethyl)-5-fluoro-2,3-dihydro-1H-inden-1-one
(25),20, 21 THIQ was alkylated under alkylation method B to afford compound 3h in 23% yield. Mp 240-
1
241 ºC; H NMR (DMSO-d6): 7.73 (dd, J = 5.8, 8.4 Hz, 1H), 7.45 (d, J = 9.0 Hz, 1H), 7.24 (m, 5H),

4.52 (m, 2H), 4.28 (m, 2H), 3.68 (m, 1H), 3.34 (m, 6H), 2.99 (m,1H), 2.89 (m, 2H), 2.31 (m, 1H), 1.99
(m, 1H). Anal. calcd for C20H21ClFNO: C 69.46, H 6.12, N 4.05; Found: C 69.18, H 6.08, N 4.60.
4.2.29. 2-(2-(3,4-Dihydroisoquinolin-2(1H)-yl)ethyl)-2,3-dihydro-1H-inden-1-one hydrochloride, 3i
Under the general alkylation method B, the previously described alkylating agent 2-(2-chloroethyl)-2,3-
dihydro-1H-inden-1-one (26)20 was coupled to THIQ to afford compound 3i as the HCl salt in 65%
yield. Mp: 201-203 ºC. 1H NMR (300 MHz, DMSO-d6) δ 11.18 (s, 1H), 7.74 – 7.63 (m, 2H), 7.60 (d, J
= 7.6 Hz, 1H), 7.48 – 7.40 (m, 1H), 7.29 – 7.15 (m, 4H), 4.49 (s, 1H), 4.31 (s, 1H), 3.68 (s, 1H), 3.40 (t,
J = 8.4 Hz, 3H), 3.01 (s, 1H), 2.92 (d, J = 4.1 Hz, 1H), 2.89 – 2.77 (m, 2H), 2.41 – 2.28 (m, 1H), 1.99 (d,
J = 9.8 Hz, 1H). 13C NMR (75 MHz, DMSO-d6) δ 207.35, 154.03, 136.27, 135.65, 131.92, 128.97,
128.07, 128.00, 127.38, 127.04, 123.76, 53.85, 52.05, 49.10, 44.65, 32.59, 25.42. Anal. Calcd for
C20H22ClNO·0.2H2O: C, 72.47; H, 6.81; N, 4.23. Found: C, 72.55; H, 6.56; N, 4.29.
4.2.30.
5-Chloro-2-(2-(3,4-dihydroisoquinolin-2(1H)-yl)ethyl)-2,3-dihydro-1H-inden-1-one
hydrochloride, 3j.
The previously reported alkylating agent 2720 was reacted with THIQ under the general alkylation
1
method B condition to afford compound 3j as the HCl salt in 41% yield. Mp 239-240 °C, H NMR
(DMSO-d6): 11.10 9 (brs,1H), 7.72 (s,1H), 7.67 (d, J = 8.1 Hz, 1H), 7.49 (d, J = 8.1 Hz, 1H), 7.17-7.27
(m, 4H), 4.51 (d, J = 12.6 Hz, 1H), 4.25-4.32 (m,1H), 3.65-3.2 (m,1H), 3.23-3.42 (m, 5H), 2.92-3.02
(m,1H), 2.86-2.92 (m, 2H), 2.29-2.37 (m,1H), 1.95-2.05 (m,1H).Anal. calcd for C20H21Cl2NO: C 66.30,
H 5.84, N 3.87. Found: C 66.29, H 5.94, N 3.93.
5. Receptor binding studies
Binding affinities reported in Tables 1- 3 were conducted by the National Institute of Mental Health
Psychoactive Drug Screening Program (NIMH-PDSP). Details of the methods and radioligands used for
the binding assays were previously reported.32
Acknowledgements
This work was supported by the continuing financial support of the NIH/NIGMS SCORE grant number
2SC1GM116724, NIMHD RCMI grant number G12 RR 03020 and a Title III Grant to Florida A&M
University. The work was also supported in part by the Pharmaceutical Research Center NIH/ NCRR
1C06-RR12512-01 Grant. Ki determinations and receptor binding profiles were generously provided by
the National Institute of Mental Health’s Psychoactive Drug Screening Program, Contract # HHSN-271-
2013-00017-C (NIMH PDSP). The NIMH PDSP is directed by Bryan L. Roth, MD, PhD, at the
University of North Carolina at Chapel Hill and Project Officer Jamie Driscoll at NIMH, Bethesda MD,
USA. Funding sources acknowledged had no involvement in the study design, data collection and
interpretation, or article preparation and submission of this manuscript.
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Synthesis and evaluation of the structural elements in alkylated tetrahydroisoquinolines for binding to CNS
receptors
Edward Ofori, Xue Y. Zhu, Jagan R. Etukala, Barbara A. Bricker, Seth Y. Ablordeppey*
Division of Basic Pharmaceutical Sciences, Florida A&M University, College of Pharmacy and Pharmaceutical
Sciences, Tallahassee, FL 32307, USA
Graphical Abstract: