Potent BRAF kinase inhibitors based on 2,4,5-trisubstituted imidazole with naphthyl and benzothiophene 4-substituents

Bioorganic & Medicinal Chemistry 21 (2013) 1284–1304

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Bioorganic & Medicinal Chemistry

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Potent BRAF kinase inhibitors based on 2,4,5-trisubstituted

imidazole with naphthyl and benzothiophene 4-substituents

Dan Niculescu-Duvaz ^a, Ion Niculescu-Duvaz ^a, Bart M. J. M. Suijkerbuijk ^a, Delphine Ménard ^a,

Alfonso Zambon ^a, Lawrence Davies ^a, Jean-Francois Pons ^c, Steven Whittaker ^b, Richard Marais ^d,

Caroline J. Springer ^a,

⇑

^aThe Institute of Cancer Research, Cancer Research UK Cancer Therapeutics Unit, Division of Cancer Therapeutics, 15 Cotswold Road, Sutton, Surrey SM2 5NG, United Kingdom

^bThe Institute of Cancer Research, Division of Cancer Biology, 237 Fulham Road, London SW3 6JB, United Kingdom

^cEvotec (UK) Ltd, 114 Milton Park, Abingdon, Oxfordshire, OX14 4SA, United Kingdom

^dThe Paterson Institute for Cancer Research, The University of Manchester, Wilmslow Road, Manchester M20 4BX, United Kingdom

a r t i c l e i n f o

a b s t r a c t

Article history:

The RAS–RAF–MEK–ERK pathway is hyperactivated in 30% of human cancers. BRAF is a serine–threonine

kinase, belonging to this pathway that is mutated with high frequency in human melanoma and other

cancers thus BRAF is an important therapeutic target in melanoma. We have designed inhibitors of BRAF

based on 2,4,5-trisubstituted imidazoles with naphthyl and benzothiophene-4-substituents. Two

compounds were discovered to be potent BRAF inhibitors: 1-(6-{2-[4-(2-dimethylamino-ethoxy)

phenyl]-5-(pyridin-4-yl)-1H-imidazol-4-yl} benzo[b]thiophen-3-yl)-2,2,2-triﬂuoroethanol (1i) with

BRAF IC₅₀= 190 nM and with cellular GI₅₀= 2100 nM, and 6-{2-[4-(2-dimethylamino-ethoxy)-phenyl]-

5-pyridin-4-yl-3H-imidazol-4-yl}-naphthalen-1-ol (1q) with IC₅₀= 9 nM and GI₅₀= 220 nM.

Received 24 October 2012

Revised 14 December 2012

Accepted 15 December 2012

Available online 3 January 2013

Keywords:

BRAF

Kinase inhibitors

Anticancer

Melanoma

Triarylimidazole

1. Introduction

Triaryl substituted imidazole-based compound 1¹⁸is the most

potent mutant BRAF inhibitor within its series. Although 1 is rea-

There are 200,000 newly diagnosed cases of malignant mela-

noma worldwide each year, of which ꢀ20% are incurable. Approx-

imately 40% of melanomas exhibit a mutation in the BRAF protein,¹

a serine/threonine kinase responsible for MAPK/ERK kinase (MEK)

phosphorylation in the mitogen-activated protein kinase (MAPK)

pathway, a conserved signalling cascade responsible for cell prolif-

eration and survival. The majority of BRAF mutations (90%) consist

of a glutamic acid substitution of the valine at position 600

(V600E).²This mutation causes a destabilisation of the inactive

form of the enzyme, which in turn leads to its constitutive activa-

tion resulting in uncontrolled proliferation of cells.³

Many mutant BRAF inhibitors have been developed, some hav-

ing been assessed clinically. GSK2118436,⁴RAF265,⁵and XL281⁶

are currently being evaluated in phase I-III clinical trials.

PLX4032 (vemurafenib, Zelboraf) has shown promising results in

mutant BRAF driven melanoma^7–10and was approved for the treat-

ment of ^V600EBRAF metastatic melanoma.

sonably potent on isolated mutant BRAF, it is less potent in a mu-

tant BRAF driven cell line, and greater cell line potency is

desirable. We therefore investigated the triaryl imidazole scaffold

further to generate improved kinase and cellular activity com-

pared to compound 1. We have named the imidazole core ring

C and the putative hinge binder ring A; ring B interacts in the

hydrophobic pocket of the enzyme (BPII)¹⁹and ring D extends

outside the BRAF ATP-binding pocket pointing towards, and inter-

acting with, the solvent.

Compounds containing 2,4,5-trisubstituted, ﬁve-membered,

aromatic heterocycles have been reported previously as potent

inhibitors of BRAF, targeting the active conformation of the

kinase.^20–26It is clear that the nature of group B, targeting the

hydrophobic pocket next to the gatekeeper residue is crucial for

activity. Three types of B-rings have been described in active

triarylimidazole BRAF inhibitors: indanone-oximes, chlorophenols

and tricyclic pyrazoles.^18,21,24,26Recently, diarylthiazoles with

phenyl-arylsulfonamides as B-rings have also been reported.²⁵

Our aim was to discover new related compounds as BRAF inhibitors

by focusing on exploring the ring B substituents. These substitu-

ents were designed to probe the inner environment of the BPII

pocket of the protein by exposing it to different combinations of

We initiated a drug discovery programme to identify alternative

BRAF inhibitors.^11–18One example is shown in Figure 1.

⇑

Corresponding author. Tel.: +44 (0)20 8722 4214; fax: +44 (0)20 8722 4046.

E-mail address: caroline.springer@icr.ac.uk (C.J. Springer).

http://dx.doi.org/10.1016/j.bmc.2012.12.035

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

1285

the increased lipophilicity and Van der Waals radius (size of ring

B) of the inhibitor rather than to improved electrostatic interac-

tions, since the close analogue with 3-chloro-4-ﬂuorophenyl ring

B (1b) is inactive. The naphthyl group was considered a suitable

extrapolation of the 3,4-dichlorophenyl fragment, which can be

further substituted with H-bond donors or acceptors.

N

A

H

N

C

D

N

B

N

HN

1

BRAF IC₅₀=0.240 uM

SRB GI₅₀=0.870 uM

2. Results and discussion

2.1. Chemistry

Figure 1. Structure of 2,4,5 trisubstituted imidazole-based BRAF inhibitor with

tricyclic pyrazole ring B.

The 2,4,5-trisubstitution of the imidazole scaffold was achieved

using 2,4,5-tribromoimidazole (4) as starting material (Scheme 1).

N1 was protected with a methoxymethyl (MOM) group to give 5,

which was subsequently functionalised selectively at the 2-posi-

tion with a p-hydroxyphenyl group using a Suzuki coupling reac-

tion to give 6. A 2-N,N-dimethylaminoethyl solubilizing group

was then attached through the phenolic oxygen atom to give inter-

mediate 7. The remaining two bromine atoms on the imidazole

ring were displaced consecutively, ﬁrst at the 5-position by a

4-pyridyl ring and, secondly, with a number of functionalised aro-

matic systems at the 4-position, in both cases employing Suzuki

coupling reactions. Depending on the stability of the 4-substituent,

two distinct routes were followed: route 1 relies on the deprotec-

tion of 4-bromo intermediate 8 followed by coupling of a boronic

acid with the resulting free imidazole 9; in route 2, on the other

hand, the 4-substituent is put in place ﬁrst and the imidazole N1

of the resulting compound 10 is then deprotected in the last step.

Compounds 1a–z were synthesised in moderate to good yields

using one of the two approaches.

Some of the boronic acids or esters used for the arylation of the

imidazole 4-position were commercially available (e.g., 11 and 12,

Scheme 2), however most of them required synthesis. The routes

towards these building blocks are depicted in Schemes 3–11.

For the synthesis of boronic esters 17 and 20, 3-bromophenol

(13) was used as the starting material (Scheme 3). First, 13 was

formylated and the resulting ortho-hydroxybenzaldehyde 14 was

treated with ethyl diazoacetate to give derivatised benzofuran 15

in quantitative yield. Reduction of 15 with DIBAL-H followed by

boronylation gave hydroxymethyl synthon 17. Saponiﬁcation, ami-

dation and boronylation of intermediate 15 gave amide synthon

20. The coupling of compounds 17 and 20 with intermediate 9 un-

der standard Suzuki coupling conditions (see Section 4) gave inhib-

itors 1c and 1d.

polar and nonpolar groups, as well as hydrogen bond donor and/or

acceptor groups.

We have described¹⁸a series of pyrazole triaryl imidazoles and

diarylfuran carboxamide mutant BRAF inhibitors bearing tricyclic

ring B. We showed that the triarylimidazole scaffold yielded more

potent BRAF inhibitors than the diarylfuran-carboxamides. Herein

we have kept the central imidazole and the 2- and 5-substituents

constant: the 2-substituent is 2-(4-diaminoethoxyphenyl), which

is used as a solubilising group, and the 5-position is occupied by

a 4-pyridyl group, which is the putative hinge-binder.²³Here we

focus on the SAR of two new types of B rings: (a) substituted ben-

zofurans and benzothiophenes (compounds 2, Fig. 2); (b) substi-

tuted naphthyls (compounds 3, Fig. 2).

The benzofurans and benzothiophenes were proposed on the

basis of their similarity with the indane scaffold of the indanone-

oximes, the key group responsible for the activity of SB590885²³

(Fig. 2) and GDC-0879.²²A range of H-bond donor, H-bond accep-

tor, polar and non-polar substituents were probed on the benzofu-

ran and benzothiophene fragment, including isosteres of oxime,

such as the hydroxymethyl group.

Naphthyls substituted with H-bond donors were proposed

based on the rationale that H-bond donors such as oximes, phenols

or pyrazoles^21,24,26are required as B-rings for enhanced activity

against BRAF. The increased lipophilicity of the naphthyl group ly-

ing in the hydrophobic pocket of BRAF is hypothesised to be desir-

able for improved potency against BRAF, favoring also the cellular

activity of the ligand presumably due to increased cell permeabil-

ity. This hypothesis is supported by the reported SAR of triaryl

imidazole BRAF inhibitors. For example a triarylimidazole with

4-chloro-3-hydroxyphenyl ring B is 3.5 fold more potent in the BRAF

assay than the equivalent compound with 3-hydroxyphenyl ring

B;²¹2,4-dihydroindeno[1,2-c]pyrazole ring B on the same scaffold

is >50 fold more active than the equivalent 2,8-dihydroindeno

[1,2-d][1,2,3]triazole.¹⁸Examples of naphthol groups as B-rings, albeit

linked to different core scaffolds, were reported to provide good

BRAF inhibition.^26,27Interestingly, the screening of triarylimidazole

BRAF inhibitors in our group identiﬁed the lipophilic 3,4-dichloro-

phenyl ring B motif associated with activity against BRAF of

Derivatised benzothiophenes were synthesised from the key

intermediate 3,6-dibromobenzothiophene (25), which was ob-

tained from 4-bromo-2-ﬂuorobenzaldehyde (21) in four steps.

Compound 21 was treated with ethyl thioglycolate to give 22 in

excellent yield. Hydrolysis of the ester functionality and subse-

quent copper-mediated decarboxylation gave 24; selective 3-bro-

mination with NBS gave 25. Compound 25 could be lithiated at

the 3-position and quenched with appropriate electrophiles to give

0.58 lM (compound 1a, Table 1). This effect can be attributed to

N

H

N

H

N

H

N

O

N

O

N

O

N

Z

R_n

X

R_n

Y

N

HO

SB590885

2

3

Z=S, O

X, Y=CH, N

R=various substituents

Figure 2. General structure of inhibitors with benzofuran/benzothiophene or naphthyl isosteres of indanoneoximes.

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Table 1

Biological activities of compounds 1a–z

N

H

N

O

N

R

#

R

BRAF IC₅₀

(l

M) SEM (number of replicates)

pERK IC₅₀

(

lM) SEM (number of replicates)

SRB GI₅₀(l

M) SEM^a

Cl

1a

0.58 0.07(3)

>10

5.9 2.0(2)

n.d.

1.6 0.06

n.d.

Cl

1b

1c

F

O

>10

n.d.

OH

O

1d

O

NH₂

S

1e

1f

>10

n.d.

S

HO

1g

>10

n.d.

S

1h

1i

>10

n.d.

HO

C₂F₅

CF₃

0.33 0.10(3)

2.7 0.02(3)

3.1 0.1

R-1i

1j

0.19 0.03(2)

9.4 0.3(2)

>10

2.3 0.3(2)

2.1 0.3

2.3 0.07

n.d.

CF₃

S

31(1)

S

1k

1l

n.d.

S

O

S

14

n.d.

S

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

1287

Table 1 (continued)

#

R

BRAF IC₅₀

>10

(l

M) SEM (number of replicates)

pERK IC₅₀

n.d.

(

lM) SEM (number of replicates)

SRB GI₅₀

n.d.

(l

M) SEM^a

S

1m

O

F₃C

HO

1n

>10

n.d.

S

1o

1p

F₃C

HO

OH

1.4 0.08(3)

3.6 0.3(2)

3.2 0.03

1q

0.009 0.003(3)

8.8 1.4(2)

0.39 0.04(3)

14 2.0(2)

0.22 0.02

4.3 0.02

1.1 0.04

OH

1r

1s

HO

0.042 0.007(3)

1.25 0.09(3)

Cl

OH

1t

0.029 0.028(2)

0.25 0.03(3)

11 1.2

F

OH

H

N

O

1u

1v

>100

n.d.

N

H

O

1w

1x

>10

n.d.

HN

O

N

F

1.1 0.14(3)

5.1 1.4(3)

5.7 0.05

NH₂

1y

1z

>10

n.d.

HOOC

a

Cell proliferation assays (SRB GI₅₀) were performed in quadruplicate.

the desired 3-substituted benzothiophenes in moderate yields (see

Schemes 4 and 5).

propionamide. Reduction to racemic alcohol 30 with NaBH₄, fol-

lowed by boronylation to 31 and coupling with 9 gave racemic

1h (Scheme 4).

An analogous route using 2,2,2-triﬂuoro-N,N-dimethyl acetam-

ide gave racemic 1i. Enantiomerically enriched (91%) R-1i was

synthesised by performing the reduction of ketone 32 with (S)-2-

methyl-CBS-oxazaborolidine (Scheme 5).

Quenching of 3-lithiated 25 with either n-propyl or methyl

disulﬁde led to thioethers 35 and 37, respectively. Boronylation

gave compounds 36 and 38, which were subsequently coupled

In one series, 25 was converted to aldehyde 26 via lithiation fol-

lowed by quenching with DMF. Standard boronylation gave inter-

mediate 27, which afforded inhibitor 1e by Suzuki coupling.

Reduction of aldehyde 1e with sodium borohydride produces alco-

hol 1f. The same intermediate 27 was converted ﬁrst to the race-

mic 28 by treatment with ethyl magnesium bromide and then

coupled with 9 to give racemic inhibitor 1g. Alternatively, 25

could be converted to 29 with 2,2,3,3,3-pentaﬂuoro-N,N-dimethyl

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D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

O

H

N

Br

b

a

c

Br

N

Br

OH

O

N

4

5

6

7

O

N

e

d

N

O

N

O

N

Br

Ar

10

8

f

Route 2

Route 1

N

H

N

H

N

e

O

N

O

N

Ar

1a-z

9

a) MOMBr, NaH, THF; b) p-HOC₆H₄B(OH)₂, K₂CO₃, Pd(PPh₃)₄, toluene, MeOH, reflux; c) Cl(CH₂)₂N(CH₃)₂,

Cs₂CO₃, DMF, 40^oC; d) pyridyl boronic ester, K₂CO₃, Pd(OAc)₂, PPh₃, DME, H₂O, 90^oC; e) Suzuki coupling:

arylboronic acids or esters, K₂CO₃, Pd(OAc)₂, PPh₃, DME, H₂O, 110^oC; f) deprotection: 5M HCl, 60^oC

Scheme 1. General synthetic route towards triarylimidazole-based inhibitors.

N

OH

B

H

N

H

N

Cl

a

OH

+

O

N

O

N

X

Cl

Br

9

X

1a X=Cl

11 X=Cl

12

1b

X=F

X= F

a) K₂CO₃, Pd(OAc)₂, PPh₃, DME, H₂O, 110^oC

Scheme 2. Synthesis of compounds 1a, 1b.

with 9 to give inhibitors 1j and 1l. These, in turn, were converted

into the corresponding sulfoxides 1k and 1m, respectively, by

treatment with Oxone^Ò(Scheme 5).

In order to obtain 2-substituted benzothiophenes, 6-bromo-

benzothiophene 24 was lithiated and quenched with N,N-dimeth-

yltriﬂuoroacetamide to give intermediate 39 which after reduction,

boronylation and coupling with intermediate 9 was converted to

the racemic inhibitor 1n (Scheme 6).

The racemic 4-(2-triﬂuoro-1-hydroxy)-phenyl boronic ester

(43) was synthesised by reduction of 1,1,1-triﬂuoroacetophenyl

bromide (41) followed by the usual boronylation procedure and

was coupled to intermediate 9 to give the racemic inhibitor 1o

(see Scheme 7).

7-Methoxy-naphthalen-2-ol (44) was converted into 45 by elec-

trophilic bromination with Br₂/PPh₃. Boronylation to 46 and cou-

pling with 9 gave inhibitor 1p. The isomer 1q was synthesised

from 6-aminotetralone (47) in several steps (Scheme 8). Intermedi-

ate 47 was converted into 48 via a diazotization reaction. Genera-

tion of vinyl silylether 49 followed by oxidation to 50 and

desilylation gave 6-bromonaphthalen-1-ol (51). Boronylation and

coupling with 9 gave 1q.

The 2-chloro and 2-ﬂuoro-1-naphthol derivatives 1s and 1t,

were synthesised as shown in Scheme 9. 6-Bromo-1-naphthol 55

was chlorinated using NaOCl/t-BuOH to give 56, followed by bor-

onylation and coupling with 9 to give 1s. The ﬂuoro analogue 1t

had to be synthesised via a more elaborate route. Treatment of

5-bromo-indan-1-one (58) with trimethylsilyl ﬂuorosulfonyldiﬂu-

oroacetate (TFDA)²⁸led to rearranged compound 59 in low yield,

which was boronylated to 60 and coupled with 8 to give 61. Depro-

tection of both the imidazole and the naphthol functionalities was

performed with HBr/HOAc at 120 °C in a sealed vessel to yield 14%

of inhibitor 1t (Scheme 9).

A few other bicyclic systems were also considered as possible

pharmacophores (Scheme 10). Particularly quinolones and amino-

isoquinolines were anticipated to be of interest. 7-Bromo-2-chloro-

quinoline (62) served as the starting material for inhibitor 1u.

Substitution of the chlorine atom with a hydroxyl group gave 63,

and a subsequent boronylation and coupling with intermediate

8

gave N-protected compound 65, which was subsequently

deprotected to give 1u. Its isomer 1v was synthesised from the

corresponding boronic ester 67 and intermediate 8. Isoquinolone

1w was obtained by Suzuki coupling of boronic ester 70 with

unprotected bromoimidazole 9.

The amino-isoquinoline substituted inhibitor 1x was synthes-

ised from 71 in 4 steps through 73 via a coupling reaction with

6-Hydroxynaphthyl substituted inhibitor 1r was synthesised by

deprotection of 54, which was obtained by Suzuki coupling of 8 and

6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)naphthalen-2-ol.

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

1289

O

B

Br

HO

Br

c

O

d

O

a

b

O

17

O

H

13

O

OH

16

14

15

e

N

f

N

Br

O

N

H

N

O

OH

18

1c

g

Br

O

NH₂

19

d

N

O

B

N

O

e

O

N

H

N

O

20

NH₂

O

NH₂

1d

a) CH₂O, MgCl₂, NEt₃, CH₃CN, reflux; b) fluoroboric acid.Et₂O, EtOOCCHN₂, H₂SO₄, DCM; c) DIBAL-H, DCM,

-78^oC; d) boronylation(general procedure); e) coupling(general procedure); f) NaOH2N, EtOH, reflux; g) oxalyl

chloride, NH₄OH, DMF, DCM.

Scheme 3. Synthesis of benzofuran inhibitors 1c, 1d.

the protected intermediate 8 (see Scheme 11). Fluoronaphthyl-

functionalized inhibitor 1y was synthesised by boronylation of

75, coupling with 8, and deprotection of intermediate 77 according

to the general methods. 2-Naphthoic acid 1z was obtained accord-

ing to the same route.

benzofuran and benzothiophene alcohols 1c and 1f are inactive.

The H-bond acceptor aldehyde analogue 1e is also inactive. We

considered reasons for the greater activity of indanone oxime

SB590885 compared to the isosteric 1c and 1f. One possible expla-

nation is that the H-donor in benzofuran/benzothiophene is situ-

ated on a freely rotating bond, whereas in the oxime the position

is ﬁxed. This is also supported by the reported increased activity

of 2,4-dihydroindeno[1,2-c]pyrazole as compared to phenylpyraz-

oles.^21,24However other potential explanations for this decrease

in BRAF inhibition are possible, such as: (a) a heteroatom pair (such

as nitrogen and oxygen of oxime^21,24or the two nitrogen groups of

pyrazole) rather than H-bond donor ability is required in the active

site; (b) a H-bond donor in the active site is required, and it has to

be more acidic than an alcohol (pK_as of oximes are around 11 and

pK_aof chlorophenol is 9);²¹(c) the indane ring of indanone is more

lipophilic than the benzothiophene and especially the benzofuran

group. The good activity of compound 1a supports the idea that in-

creased lipophilicity is favorable for BRAF inhibition.

2.2. Biological results

Three assays were used to determine the biological activities of

compounds 1a-z. The IC₅₀of the ^V600EBRAF mutant enzyme inhibi-

tion in vitro (IC₅₀, BRAF) was measured for all compounds. Those

compounds showing promising activity in the kinase assay were

submitted to two cellular assays: inhibition of the phosphorylation

of extracellular signal-regulated kinase (ERK) (IC₅₀, pERK) and

growth inhibition of BRAF dependent WM266.4 cells (GI₅₀

,

SRB).¹⁴These data are summarised in Table 1.

2.3. SAR of compounds with benzofuran or benzothiophene

ring B

We used these hypotheses to guide the design of our BRAF

inhibitors. Based on hypothesis (a) we selected sulfoxide as a pair

of vicinal heteroatoms lacking the H-bond donor function. Methyl

and propyl sulfoxide compounds 1m and 1k are inactive; the re-

duced thiomethyl ether analogues 1l and 1j respectively show only

The benzofuran and benzothiophene rings were designed as

isosteres of the indane group of indanone-oximes.^21,23,24Despite

the shape similarity with indanone-oxime, the H-bond donors

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D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

O

F

Br

a

O

b

O

d

c

H

S

OEt

Br

S

OH

S

Br

22

23

24

21

25

e

O

N

O

h

f

H

N

H

N

i

O

N

O

N

O

S

Br

B

26

O

27

1f

1e

j

O

HO

g

N

HO

H

h

N

O

S

B

O

28

1g

HO

N

HO

O

H

C₂F₅

h

f

i

N

O

N

S

O

S

Br

B

O

29

30

31

1h

HO

C₂F₅

a) ethylthioglycolate, K₂CO₃, DMF; b) EtOH, KOH, reflux; c) Cu powder, quinoline, 185^oC; d) NBS, AcOH, CHCl₃; e) nBuLi, DMF, Et₂O,

-70^oC; f) boronylation (general procedure); g) EtMgBr, THF; h) Suzuki coupling with 9 (general procedure); i) NaBH₄, EtOH or MeOH;

j) nBuLi, 2,2,3,3,3-pentafluoro-N,N-dimethylpropionamide, -70^oC

Scheme 4. Synthesis of 3-substituted benzothiophene inhibitors 1e–h.

weak activity (BRAF IC₅₀= 14

l

M and 9.4

l

M). Since the sulfoxide

inhibition, therefore naphthols 1p, 1q and 1r were initially syn-

thesised. The hydroxyl H-bond donor on the naphthyl ring has

a beneﬁcial effect on binding to BRAF, with activity observed

for all three naphthols. This is in agreement with another recent

report of a naphthol-containing BRAF inhibitor.²⁶The position of

the hydroxyl group has a profound effect on afﬁnity, with the

6-substituted 1-naphthol 1q being >100-fold more potent than

the 7-substituted 2-naphthol 1p and 1000 fold more potent than

the 6-substituted 2-naphthol 1r. This large increase in BRAF inhi-

bition can be explained by an H-bond interaction of the correctly

positioned hydroxyl group with an H-bond acceptor of the pro-

tein. Compound 1q has potent inhibitory activity on BRAF (BRAF

IC₅₀= 9 nM), good cellular activity on the MAPK pathway (pERK

IC₅₀=390 nM) and growth inhibition of WM266.4 cells (GI₅₀

SRB = 219 nM).

Two halogenated analogues of 1q were synthesised, chloro-

naphthol 1s and ﬂuoronaphthol 1t, in order to increase the acidity

of the naphthol. The chloro substitution in 1s decreases the kinase

inhibition 4-fold, and the cellular activity correspondingly to

micromolar inhibition. The smaller ﬂuorine substituent in 1t still

causes a 3-fold decrease in kinase inhibition, although the cellular

inhibition of the pathway is comparable to 1s. The WM266.4

growth inhibition value is surprisingly high, since in most cases

the pERK IC₅₀and GI₅₀SRB are correlate very well. This decrease

in activity in the kinase assay can be potentially attributed to par-

tial ionisation of 1t and 1s to inactive negatively charged pheno-

lates at the pH of the assays. The pK_aof 2-chloro-1-naphthol is

7.8; the pK_aof 2-ﬂuoro-1-naphthol can be estimated to be around

7.9 based on the pK_aof 2-ﬂuorophenol (8.7) and the difference

might not have been the best choice of heteroatom pairs, possibly

due to lack of H-bond donor capability, we tested the amide group

containing the carbonyl acceptor and the NH₂donor, albeit in a

1,3-position. However the corresponding compound 1d is also

inactive.

In order to test hypothesis (b), we sought benzothiophenes

bearing more acidic H-bond donors. Triﬂuoroethanol is more

acidic than ethanol (pK_a= 12.5 vs 15.9), therefore the racemic

1-(benzothiophen-3-yl)-2,2,2-triﬂuoroethanol derivative 1i was

synthesised. Pleasingly, this compound is more active (BRAF

IC₅₀= 0.33

lM). The R-enantiomer R-1i is active at similar levels

(BRAF IC₅₀= 0.19

l

M) and low micromolar cell activity. The activ-

ity appears to be due to electronic effects, as compound 1g with

ethyl substituent with a similar van der Waals volume (39.8 Å³

for CF₃and 38.9 Å³for Et)²⁹is inactive. The larger pentaﬂuoro-

ethyl-substituted analogue 1h is not active, presumably for steric

reasons. The 3-position of the 2,2,2-triﬂuoroethanol substituent

on the benzothiophene ring B is crucial, since neither the 2-substi-

tuted benzothiophene 1n nor the 4-phenyl substituted 1o are

active.

2.4. SAR of compounds with naphthyl ring B

The naphthyl group was selected as a more lipophilic ring B

alternative, as per hypothesis (c), which is amenable to substitu-

tion with H-bond donors in a rigid framework. The potent BRAF

inhibition shown by compound 1i points towards the require-

ment for a relatively acidic hydroxyl group on ring B for BRAF

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

1291

O

HO

CF₃

b1

b2

c

d

O

S

32

S

N

Br

B

O

Br

H

N

R-33

R-34

O

N

S

d

HO

CF₃

HO

-1i

CF₃

c

R-1i

a

O

S

B

O

S

Br

-34

-33

N

H

N

S

d

e

c

O

N

S

25

O

S

Br

B

O

35

1j

36

f

N

H

N

O

N

S

1k

O

N

H

N

S

O

N

g

c

d

N

S

O

S

B

O

Br

1l

37

38

f

N

H

N

O

N

S

1m

O

a) nBuLi, N,N-dimethyltrifluoroacetamide, hexane, -100^oC; b1) NaBH₄, EtOH or MeOH; b2) (S)-oxazaborolidine, catecholborane,

DCM; c) boronylation (general procedure); d) coupling with 9 (general procedure); e) nBuLi, propyldisulfide, Et₂O, -70^oC; f) oxone,

H₂O-Me₂CO; g) nBuLi, methyldisulfide, Et₂O, -70^oC.

Scheme 5. Synthesis of 3-substituted benzothiophene inhibitors 1i–1m.

between the pKa values of 2-chlorophenol (8.6) and 2-chloro-

1-naphthol (7.8). By comparison, the pK_aof 1-naphthol is 9.3,

and is mainly non-ionised at physiological pH.

The importance of the hydroxyl H-bond donor group of naphthol

is underlined by comparison of 1q with 1w and 1t with 1y. The pre-

dominant tautomer of 1-hydroxyisoquinoline 1w is the isoquino-

lone, lacking the crucial H-donor group of the 1-naphthol 1q and is

completely devoid of activity. Compound 1y, the ﬂuoronaphthyl

analogue of ﬂuoronaphthol 1t, is also inactive. A similar loss of activ-

ity is seen for the quinolones 1u and 1v when compared to the cor-

responding naphthols 1p and 1r. The activity can be partially

restored (to BRAF IC₅₀= 1 M) when the isoquinolone is replaced

with 1-aminoisoquinoline 1x, which possesses an H-bond donor

group in the same position as naphthol 1q. The naphthoic acid 1z

is also inactive, which is not surprising considering it is deproto-

nated to the corresponding carboxylate at neutral pH.

Based on these results we concluded that appropriate acidity

(pK_a= 9–11) of a correctly positioned H-bond donor within a rigid

framework is the main driving factor for potent BRAF inhibition in

the triarylimidazole scaffold presented here.

l

1292

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

N

a

H

N

b

O

OH

c, d

O

N

S

Br

S

CF₃

S

CF₃

Br

N

S

F₃C

HO

24

39

-40

-1n

a) nBuLi, N,N-dimethyltrifluoroacetamide, Et₂O, -70^oC; b) NaBH₄, EtOH; c) boronylation (general procedure);

d) Suzuki coupling with 9 (general procedure).

Scheme 6. Synthesis of 2-substituted benzothiophene inhibitor 1n.

O

N

OH

a

H

N

b

c

F₃C

O

N

Br

O

N

Br

B

O

41

42

43

F₃C

1o

OH

a) NaBH₄, NaOH, MeOH; b) boronylation (general procedure); c) K₂CO₃, Pd(OAc)₂, PPh₃, DME, H₂O, 110^oC.

Scheme 7. Synthesis of 1,1,1-triﬂuoro-2-hydroxyethyl phenyl inhibitor 1o.

were performed on Gilson Prep LC modules running on software

3. Conclusions

version 1.71 or 3.0 on HyperprepHSC18 100 mm Â 21.2 mm col-

umns, 12 lm, at a ﬂow rate of 30 mL/min at room temperature

A new series of BRAF inhibitors has been prepared, based on

2,4,5-trisubstituted imidazoles containing in the 4 position a

substituted naphthyl, benzofuranyl or benzothiophenyl group.

The presence of a correctly positioned H-bond donor of appropriate

pK_aon these bicyclic ring systems is important for activity.

Benzo[b]thiophen-3-yl)-2,2,2-triﬂuoro-ethanol is a novel moiety

that interacts with the BPII pocket of BRAF resulting in potent BRAF

kinase inhibition in vitro and in cells. Benzo[b]thiophen-3-yl)-

2,2,2-triﬂuoro-ethanol 1i and naphthols 1q, 1s and 1t are particu-

larly active against BRAF with compound 1q in particular showing

BRAF IC₅₀of 9 nM, and cellular potency at submicromolar levels.

These ﬁndings suggest new avenues for designing BRAF inhibitors.

using as aqueous phase: water + 0.1% TFA and as organic phase:

acetonitrile + 0.1% triﬂuoroacetic acid (TFA) (UV detector, at 215

and 254 nM). Chiral HPLC was run on Chiracel OD-H columns using

as eluent: (a) heptane/methanol 9:1 + 0.1% triethylamine (TEA) or

(b) heptane/ethanol 85:15 at a ﬂow rate of 30 mL/min (UV detec-

tor, at 215 and 254 nm). NMR spectra were recorded in DMSO-d₆

on a Bruker DPX 250 MHz or a Bruker Advance 500 MHz spectrom-

eter. Chemical shifts (d) are given in ppm and are referenced to

residual, not fully deuterated solvent signal (i.e. DMSO-d₅). Cou-

pling constants (J) are given in Hz. Accurate Mass Measurement

was performed with a Waters Micromass LCT Premier orthogonal

acceleration Time-of-Flight Mass Spectrometer 4 GHz TDC with

LockSpray™ enable mass measurements of 5 ppm or better for

m/z of 400 or greater and 2 mDa or better for m/z of 400 or less.

Calibration reference: Wpos_150208.cal or Wneg_150208a.cal.

MassLynx v4.1 SCN 633 was the operating software using the in-

built elemental composition to report data. Minimum 10 scans

combined across a MS peak. Microwave reactions were run on a

CM discovery unit operating at 200 watts with simultaneous

stirring.

4. Experimental

4.1. General

All starting materials, reagents and solvents for reactions were

reagent grade and used as purchased. Chromatography solvents

were HPLC grade and were used without further puriﬁcation.

Reactions were monitored by thin layer chromatography (TLC)

analysis using Merck silica gel 60 F-254 thin layer plates. Flash

column chromatography was carried out on Merck silica gel 60

(0.015–0.040 mm) or in disposable Isolute Flash Si and Si II silica

gel columns. LC–MS analyses were performed on a Micromass

4.2. 2-Hydroxy-4-bromobenzaldehyde (14)

3-Bromophenol (13) (2 g, 11.6 mmol), magnesium chloride

(1.66 g, 17.4 mmol) and triethylamine (6.2 mL, 44.4 mmol) were

dissolved in acetonitrile (60 mL) and stirred at rt for 20 min before

adding paraformaldehyde (2.34 g, 78 mmol) and heating at reﬂux

for 8 h. After cooling to rt, the reaction was acidiﬁed with 2 N

HCl and extracted with MTBE (2 Â 60 mL). The combined organic

extracts were washed with brine (40 mL), dried (MgSO₄), ﬁltered

and evaporated. The residue was puriﬁed by chromatography on

silica gel eluting with 0–5% EtOAc in heptane and the product

recrystallised from hot heptane. Yield: 595 mg (25%). ¹H NMR

(CDCl₃), d: 7.18 (dd, 1H, ArH), 7.21 (d, J = 1.8, 1H, ArH), 7.42 (d,

J = 8.2, 1H, ArH), 9.87 (br, 1H, OH), 11.13 (s, 1H, CHO).

LCT/Water’s Alliance 2795 HPLC system using 5 lm Atlantis C18,

50 mm Â 2.1 mm columns at 22 °C with the following solvent sys-

tem: Aqueous: water + 0.1% formic acid; Organic: 0.1% for-

mic + acetonitrile, at a ﬂow rate of 1 mL/min. Method A: gradient

starting with 100% aqueous to 100% organic in 2.5 min at room

temperature and a ﬂow rate of 0.6 mL/min or method B gradient

starting with 100% aqueous to 100% organic in 5 min at 40 °C (col-

umn temperature) at a ﬂow rate of 0.6 mL/min. UV detection was

at 215 nM and ionisation was positive or negative ion electrospray.

The molecular weight scan range was 50–1000. Samples were in-

jected at 3 ll on a partial loop ﬁll. All automated HPLC puriﬁcation

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

1293

N

c

a

b

N

O

HO

O

HO

Br

HO

Br

B

O

HO

O

N

45

44

46

H

N

1p

Br

e

f

Br

NH₂

d

OTIPS

49

OTIPS

O

48

50

47

N

H

N

O

B

b

c

Br

g

O

N

O

N

OH

51

52

1q

O

N

O

B

N

c

H

N

h

N

O

N

O

N

HO

N

53

HO

54

1r

a) Br₂, MeCN, rt; b) boronylation (general procedure); c) coupling (general procedure); d) NaNO₂, HBr, CuBr, H₂O, 0^oC

e) TIPSOTf, NEt₃, DCM, rt; f) DDQ, dioxane, 80^oC; g) NaOH, NMP, H₂O-MeOH; h) deprotection (general procedure)

Scheme 8. Synthesis of naphthol inhibitors 1p–r.

4.3. Ethyl 6-bromobenzofuran-3-carboxylate (15)

CH₂), 7.38 (dd, 1H, ArH), 7.51 (d, J = 8.6, 1H, ArH), 7.57 (s, 1H,

ArH), 7.66 (d, J = 1.8, 1H, ArH).

To a solution of 2-hydroxy-4-bromobenzaldehyde (14) (345 mg,

1.7 mmol) and ethereal ﬂuoroboric acid (23

ll, 0.2 mmol) in DCM

4.5. 6-Bromobenzofuran-3-carboxylic acid (18)

(1 mL) was added a solution of ethyl diazoacetate (0.28 mL,

2.7 mmol) in DCM (3 mL) over 12 min. After 2 h, the solvent was

evaporated and concentrated sulfuric acid (0.15 mL) added. After

10 min, the reaction was diluted with DCM (5 mL) and the acid

neutralized with solid sodium bicarbonate. The desired product

was puriﬁed by chromatography on silica gel eluting with DCM.

Yield: 490 mg (quantitative). ¹H NMR (CDCl₃), d: 1.43 (t, J = 7.1,

3H, CH₃), 4.41 (q, J = 7.1, 2H, CH₂), 7.49 (dd, J = 8.4, 1.7, 1H, ArH),

7.72 (d, J = 1.7, 1H, ArH), 7.93 (d, J = 8.5, 1H, ArH), 8.22 (s, 1H, ArH).

A mixture of ethyl 6-bromobenzofuran-3-carboxylate (220 mg,

0.8 mmol) and 2 N NaOH (0.6 mL, 1.2 mmol) in ethanol (1.2 mL)

was heated for 1 h. The bulk of the solvent was evaporated and

the residue acidiﬁed with 2 N HCl (1.2 mL) to give a thick precipi-

tate. This was diluted with water, cooled to rt and ﬁltered to leave

the product after washing with more water. Yield: 99 mg (50%). ¹H

NMR (DMSO-d₆), d: 7.56 (dd, J = 8.4, 1.8, 1H, ArH), 7.91 (d, J = 8.4,

1H, ArH), 8.04 (d, J = 1.7, 1H, ArH), 8.70 (s, 1H, ArH), 13.09 (s, 1H,

COOH). LC–MS: R_f= 1.87 min; m/z 239/241 ([M+H]⁺, 100). HRMS

(EI): m/z calcd for C₉H₅BrO₃([M+H]⁺): 238.9344; found: 238.9355.

4.4. (6-Bromo-benzofuran-3-yl)-methanol (16)

A

solution of ethyl 6-bromobenzofuran-3-carboxylate (15)

4.6. 6-Bromobenzofuran-3-carboxylic acid amide (19)

(135 mg, 0.5 mmol) in DCM (2.7 mL) was cooled to À78 °C. DI-

BAL-H (1.5 M in toluene) (0.83 mL, 1.2 mmol) was added over

2 min and the reaction stirred at rt for 4.5 h before adding water

(0.45 mL) and EtOAc (10 mL). After separation, the organic phase

was washed with 1 N HCl (10 mL), dried (MgSO₄), ﬁltered and

evaporated. The product was puriﬁed by chromatography on silica

gel eluting with 0–40% EtOAc in heptane to afford 84 mg (74%) of

desired material. ¹H NMR (CDCl₃), d: 2.22 (s, 1H, OH), 4.80 (s, 2H,

Compound 18 (99 mg, 0.4 mmol) was suspended in DCM (1 mL)

and oxalyl chloride (43 ll, 0.5 mmol) added, followed by a drop of

DMF. After 1 h, the reaction was evaporated to dryness and 0.5 N

ammonia in dioxane (3.3 mL, 1.7 mmol) added, followed after 2 h

by concentrated ammonium hydroxide (1 mL). After stirring at rt

for 16 h, the dioxane was evaporated, water (1 mL) added and ex-

tracted with DCM (3 Â 2 mL). The precipitate which formed was

1294

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

N

H

N

O

B

c

Br

a

Br

b

O

N

O

N

Cl

OH

Cl

OH

55

56

57

1s

O

Br

B

Br

b

O

d

F

O

58

F

60

59

c

O

N

H

N

e

O

N

O

N

F

O

OH

F

1t

61

F

a) NaOCl, DCM, t-BuOH, rt; b) boronylation (general procedure); c) coupling (general procedure); d) TFDA, NaF,

o-xylene, reflux: e) HBr, AcOH, 120^oC, sealed tube.

Scheme 9. Synthesis of halogenated naphthol inhibitors 1s, 1t.

ﬁltered off and washed with DCM. The combined organic phases

were washed with potassium carbonate solution and water then

dried (MgSO₄), ﬁltered and evaporated. This was combined with

the initial precipitate to give the desired product (32 mg, 32%).

LC–MS: R_f= 1.65 min; m/z 240/242 ([M+H]⁺, 100).

NMR (CDCl₃), d: 7.62 (dd, J = 8.6, 1.8, 1H, ArH), 7.95 (d, J = 8.6,

1H, ArH), 8.11 (s, 1H, ArH), 8.37 (d, J = 1.8, 1H, ArH), 13.55 (br,

1H, COOH).

4.9. 6-Bromobenzothiophene (24)

4.7. Ethyl, 6-bromobenzothiophene-2-carboxylate (22)

Compound 23 (3.67 g, 14.3 mmol) and copper powder (0.45 g,

7.1 mmol) were suspended in quinoline (18 mL) and heated at

185 °C for 2 h. After cooling down to rt, EtOAc (25 mL) was added

and the suspension ﬁltered. The solid was washed with further

EtOAc and the combined organic solutions washed with 2 N HCl

(2 Â 50 mL). After drying (MgSO₄), ﬁltration and evaporation in va-

cuo, the residue was puriﬁed by chromatography on silica with

pentane to afford the desired material (2.21 g) as a crystalline

white solid. Yield: 73%. ¹H NMR (CDCl₃), d: 7.31 (dd, J = 5.4, 0.9,

1H, ArH), 7.43 (d, J = 5.4, 1H, ArH), 7.48 (dd, J = 8.4, 1.6, 1H, ArH),

7.69 (d, J = 8.6, 1H, ArH), 8.03 (d, J = 1.8, 1H, ArH).

4-Bromo-2-ﬂuorobenzaldehyde, 21, (3.12 g, 15.4 mmol) and

potassium carbonate (2.76 g, 20.0 mmol) were suspended in dry

DMF (15 mL) and cooled to 0 °C under nitrogen. Ethyl thioglycolate

(1.7 mL, 15.5 mmol) was added portionwise over 1 h and the reac-

tion warmed slowly to rt and stirred at rt for 16 h. The reaction was

then heated at 60 °C for 5.5 h before cooling and adding water

(30 mL). The mixture was stirred for 30 min at rt then ﬁltered,

washed with water and dried to leave the product 22 (4.31 g) as

a solid. (Yield: 98%). ¹H NMR (CDCl₃), d: 1.42 (t, J = 7.0, 3H, CH₃),

4.42 (q, J = 7.0, 2H, CH₂), 7.52 (dd, J = 8.4, 1.6, 1H, ArH), 7.73 (d,

J = 8.6, 1H, ArH), 8.01 (s, 1H, ArH), 8.02 (d, J = 1.4, 1H, ArH).

4.10. 3,6-Dibromobenzo[b]thiophene (25)

4.8. 6-Bromobenzothiophene-2-carboxylic acid (23)

Compound 24 (1.5 g, 7.0 mmol) was dissolved in chloroform

(11 mL). Acetic acid (11 mL) was added and the mixture cooled

on ice before adding N-bromosuccinimide (1.57 g, 8.8 mmol) por-

tionwise over 1 h. The reaction was allowed to warm to rt then

stirred at rt for 16 h before washing with saturated sodium thiosul-

fate (22 mL), saturated sodium bicarbonate (2 Â 22 mL) and water

(22 mL). The solution was dried (Na₂SO₄) before ﬁltration and

evaporation in vacuo. The product was puriﬁed by chromatogra-

phy on silica gel with pentane to afford the desired material

Compound 22 (4.31 g, 15.1 mmol) was dissolved in hot ethanol

(43 mL) and potassium hydroxide (4.66 g, 83.2 mmol) in water

(43 mL) added. The suspension was heated at reﬂux for 1.5 h dur-

ing which time it mostly dissolved. After cooling slightly, 6 N HCl

(17 mL) was added portionwise. Much of the ethanol was evapo-

rated in vacuo and the residual solid ﬁltered, washed with water

and dried to give 23 (3.67 g) as an off-white solid. Yield: 95%. ¹H

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

1295

O

B

H

N

H

b

O

Br

O

N

Cl

N

Br

a

O

63

64

62

c

O

N

H

N

d

N

O

N

O

N

H

N

O

65

1u

O

N

O

B

N

b

H

Br

d

c

N

O

N

O

N

O

N

O

N

H

O

N

H

N

67

66

N

H

O

N

68

O

1v

H

N

O

B

H

N

b

Br

c

O

N

HN

N

O

HN

69

70

1w

O

a) NaOH 2M, microwave; b) boronylation (general procedure); c) coupling (general procedure); d) deprotection

(general procedure)

Scheme 10. Synthesis of quinolones 1u, 1v and isoquinolone 1w.

(1.49 g) as a crystalline solid. Yield: 73%. ¹H NMR (CDCl₃), d: 7.42 (s,

1H, ArH), 7.58 (dd, J = 8.6, 1.4, 1H, ArH), 7.69 (d, J = 8.4, 1H, ArH),

8.01 (d, J = 1.4, 1H, ArH).

EtOAc (2 mL), washing with brine (1 mL), drying (MgSO₄) and evapo-

rating in vacuo. The product was puriﬁed by chromatography on silica

gel with 50% EtOAc/heptane (24 mg, 47%). ¹H NMR (CDCl₃), d: 1.00

(t, J = 7.3, 3H, CH₃), 1.38 (s, 12H, CH₃), 1.89–2.04 (m, 2H, CH₂), 5.04

(t, J = 6.4, 1H, CH), 7.45 (s, 1H, ArH), 7.78 (dd, J = 8.2, 0.9, 1H, ArH),

7.88 (d, J = 8.2, 1H, ArH), 8.36 (s, 1H, ArH).

4.11. 6-Bromo-benzo[b]thiophene-3-carbaldehyde (26)

3,6-Dibromobenzo[b]thiophene, 25 (338 mg, 1.2 mmol) was dis-

solved in diethyl ether (10 mL) and cooled to À70 °C. 1.6 M n-BuLi in

hexanes (0.8 mL, 1.3 mmol) was added over 35 minutes and the

reaction stirred at À70 °C for a further 40 min before adding N,N-

4.13. 2,2,3,3,3-Pentaﬂuoro-N,N-dimethyl-propionamide

Dimethylamine (2 M in MeOH) (3 mL, 6.0 mmol) was dissolved

in DCM (4 mL) and cooled on ice/water. Pentaﬂuoropropionic

anhydride (0.4 mL, 2.0 mmol) was added over 10 min and the reac-

tion stirred at 0 °C for 30 min and at rt for 1 h. The volatiles were

evaporated and the residue re-dissolved in DCM (2 mL), washed

with water (3 Â 2 mL), dried (MgSO₄), ﬁltered and evaporated to

leave the desired compound (187 mg, 50%). ¹H NMR (CDCl₃), d:

3.06 (t, J = 1.0, 3H, CH₃), 3.19 (t, J = 2.2, 3H, CH₃). ¹⁹F NMR (CDCl₃),

d: À115.3 (s, 2F, CF₂), À82.2 (s, 3F, CF₃).

dimethylformamide (94

l

l, 1.2 mmol). After stirring at À70 °C for

4 h, the reaction was quenched with 2 N HCl (6 mL), warmed to rt

and the layers separated. The aqueous was extracted with diethyl

ether (10 mL) and the combined organic phases were washed with

saturated NaHCO₃(10 mL) and brine (5 mL) before evaporation in

vacuo. The desired compound was isolated by chromatography on

silica gel with 0–20% EtOAc in heptane (112 mg, 40%). ¹H NMR

(CDCl₃), d: 7.63 (dd, J = 8.7, 1.8, 1H, ArH), 8.01 (d, J = 1.4, 1H, ArH),

8.31 (s, 1H, ArH), 8.56 (d, J = 8.7, 1H, ArH), 10.13 (s, 1H, CHO).

4.14. 1-(6-Bromo-benzo[b]thiophen-3-yl)-2,2,3,3,3-pentaﬂuoro-

4.12. 1-[6-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-

propan-1-one (29)

benzo[b]thiophen-3-yl]-propan-1-ol ( 28)

Compound 25 (146 mg, 0.5 mmol) was dissolved in diethyl

ether (4 mL) and cooled to À70 °C. 1.6 M n-BuLi in hexanes

(0.34 mL, 0.55 mmol) was added over 15 min and the reaction stir-

red at À70 °C for a further 30 min before adding 2,2,3,3,3-pentaﬂu-

A solution of 27 (46 mg, 0.2 mmol) in dry THF (0.5 mL) was cooled

on ice/water before adding ethyl magnesium bromide (1 M in THF)

(0.18 mL, 0.2 mmol). The reaction was stirred at 0 °C for 30 min then

at rt for 1.5 h before quenching with 2 N HCl (0.5 mL), extracting with

oro-N,N-dimethylpropionamide (84 ll, 0.55 mmol). After stirring

1296

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

O

N

O

B

N

a

b

c

Br

H

N

d

O

N

O

N

NH₂

71

N

PMB

N

72

73

N

NH₂

PMB

74

1x

O

N

O

B

N

b

d

c

Br

H

N

O

N

O

N

F

N

75

76

F

77

1y

N

H

N

O

B

b

c

Br

O

N

O

N

HOOC

78

79

1z

a) PMBCl, NaH 60% in mineral oil, DMF, rt; b) boronylation (general procedure); c) coupling (general procedure); d) deprotection

(general procedure).

Scheme 11. Synthesis of inhibitors 1x–z.

at À70 °C for 4 h, the reaction was quenched with 2 N HCl

(2 Â 1 mL), warmed to rt and the layers separated. The organic

phase was washed with water (2 mL) and brine (2 mL), dried

(MgSO₄), ﬁltered and evaporated in vacuo. The desired compound

was isolated by chromatography on silica gel with 0–10% EtOAc in

heptane (97 mg, 54%). ¹H NMR (CDCl₃), d: 7.65 (dd, J = 8.7, 1.8, 1H,

ArH), 8.04 (d, J = 1.7, 1H, ArH), 8.57 (d, J = 8.7, 1H, ArH), 8.67 (s, 1H,

ArH). ¹⁹F NMR (CDCl₃), d: À115.6 (s, 2F, CF₂), À81.4 (s, 3F, CF₃).

acidiﬁed with 1 M HCl (3 mL), extracted with methyl tert-butyl

ether (MTBE, 3 Â 1 mL), dried (MgSO₄) and the solvent removed

in vacuo. The residue was puriﬁed by chromatography using hep-

tane to afford the desired material as white crystals. Yield: 80 mg

(38%). ¹H NMR (CDCl₃), d: 7.68 (dd, J = 9.1, 1.8, 1H, ArH), 8.08 (d,

J = 1.4, 1H, ArH), 8.61 (m, J = 5.0, 3.6, 2H, ArH). LC–MS:

R_f= 2.49 min; m/z not observed. HRMS (EI): m/z calcd for

C

₁₀H₄BrF₃OS ([M+H]⁺): 352.9095; found: 352.9078.

4.15. 1-(6-Bromo-benzo[b]thiophen-3-yl)-2,2,3,3,3-

4.17. 1-(6-Bromo-benzo[b]thiophen-3-yl)-2,2,2-triﬂuoro-

pentaﬂuoro-propan-1-ol ( -30)

ethanol ( 33)

Sodium borohydride (44 mg, 1.2 mmol) was dissolved in 1 N NaOH

(94 ll) and methanol (2 mL) and a solution of compound 29 (97 mg,

Compound 32 (40 mg, 0.1 mmol) was suspended in MeOH (0.4 mL)

and added to NaBH₄in a 4:5 MeOH/1 M NaOH (1.8 mL) solution. THF

(0.5 mL) was added and the reaction stirred for 1 h at rt. Water

(2 mL) was added and the aqueous layer was extracted with Et₂O

(3 Â 1 mL), washed with brine (1 Â 1 mL), dried (MgSO₄) and the sol-

vent removed in vacuo. The residue was puriﬁed by chromatography

using a stepped gradient of 0–5% EtOAc in heptane to afford the desired

material as a colourless glue. Yield: 43 mg (100%). ¹H NMR (CDCl₃), d:

2.79 (br, 1H, OH), 5.42 (m, 1H, CH), 7.54 (dd, J = 8.8, 1.6, 1H, ArH),

7.66 (s, 1H, ArH), 7.80 (d, J = 8.8, 1H, ArH), 8.04 (d, J = 1.7, 1H, ArH).

LC–MS: R_f= 2.50 min; m/z not observed.

0.3 mmol) in methanol (1.5 mL) was added. After stirring at rt for

1.5 h, water (2 mL) was added and the methanol evaporated. The res-

idue was extracted with diethyl ether (2 Â 2 mL) and the combined or-

ganic phases washed with water (2 mL) and brine (2 mL). This was

loaded directly onto a silica gel column and run using 0–20% EtOAc

in heptane to give the desired compound (79 mg, 81%). ¹H NMR

(CDCl₃), d: 2.88 (d, J = 5.3, 1H, OH), 5.53 (dt, J = 17.1, 5.9, 1H, CH), 7.52

(dd, J = 8.7, 1.8, 1H, ArH), 7.65 (s, 1H, ArH), 7.76 (d, J = 8.7, 1H, ArH),

8.02 (d, J = 1.8, 1H, ArH). ¹⁹F NMR (CDCl₃), d: k À128.4 (d, J = 275, 1F,

CF₂), À120.8 (d, J = 275, 1F, CF₂), À81.4 (s, 3F, CF₃).

4.18. (R)-1-(6-Bromo-benzo[b]thiophen-3-yl)-2,2,2-triﬂuoro-

ethanol (R-33)

4.16. 1-(6-Bromo-benzo[b]thiophen-3-yl)-2,2,2-triﬂuoro-

ethanone (32)

Compound 32 (31 mg, 0.1 mmol) was dissolved in DCM (3 mL)

and added to a solution of S-oxoazaborolidine (30 mg, 0.1 mmol) in

DCM (1 mL) under a nitrogen ﬂow. The solution was cooled to

À90 °C. Cathecholborane (0.2 mL, 2 M in THF, 0.2 mmol) was di-

luted with dry toluene (4 mL), and added dropwise over 30 min,

after which the mixture was allowed to warm up to room temper-

ature. Water (2 mL) and NaHCO₃(2 mL) were added and the aque-

ous layer was extracted with EtOAc (3 Â 1 mL), washed with brine

Compound 25 (175 mg, 0.6 mmol) was dissolved in dry Et₂O

(2 mL) and placed under a nitrogen ﬂow. The reaction mixture

was cooled to À100 °C and nBuLi in hexanes (0.47 mL, 0.7 mmol)

was added dropwise, and the mixture was stirred at À70 °C for

30 min. The reaction was cooled to À100 °C, and N,N-dimethyl-tri-

ﬂuoroacetamide was added dropwise in dry Et₂O (1 mL). The mix-

ture was stirred at À60 °C for 1 h, then allowed to warm up to rt,

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

1297

(1 Â 1 mL), dried (MgSO₄) and the solvent removed in vacuo. The

residue was puriﬁed by chromatography using a stepped gradient

of 0–2% EtOAc in heptane to afford the desired material as white

solid. Yield: 30 mg, quantitative. Chiral HPLC (method 2): 81% R-

isomer, t_r10.80, (10% S-isomer). ¹H NMR (CDCl₃), d: 2.79 (br, 1H,

OH), 5.42 (m, 1H, CH), 7.54 (dd, J = 8.8, 1.6, 1H, ArH), 7.66 (s, 1H,

ArH), 7.80 (d, J = 8.8, 1H, ArH), 8.04 (d, J = 1.7, 1H, ArH). LC–MS:

R_f= 2.16 min; m/z not observed.

stepped gradient of 5–10% EtOAc in heptane to afford the desired

material as a colourless oil. Yield: 447 mg (62%). ¹H NMR (CDCl₃),

d: 2.94 (d, J = 0.9 Hz, 1H, OH), 5.38 (q, J = 6.1 Hz, 1H, CH), 7.38 (s,

1H, ArH), 7.48 (dd, J = 8.7, 1.83 Hz, 1H, ArH), 7.72 (d, J = 8.5 Hz,

1H. ArH), 7.94 (d, J = 1.7 Hz, 1H, ArH), LC–MS: R_f= 2.50 min; m/z

not observed.

4.23. 1-(4-Bromo-phenyl)-2,2,2-triﬂuoro-ethanol ( 42)

4.19. 6-Bromo-3-propylsulfanyl-benzo[b]thiophene (35)

Sodium borohydride (327 mg, 8.7 mmol) was dissolved in a

mixture of 1 N NaOH (0.7 mL) and MeOH (6.7 mL). A solution of

bromotriﬂuoroacetophenone, 41 (0.34 mL, 2.0 mmol) in MeOH

(3.3 mL) was added and the reaction stirred at rt for 1.5 h before

adding water (8 mL). The mixture was extracted with MTBE

(2 Â 10 mL) and the combined organic phases washed with water

(10 mL) and brine (10 mL) before drying (MgSO₄), ﬁltering and

3,6-Dibromobenzo[b]thiophene 25 (292 mg, 1.0 mmol) was dis-

solved in diethyl ether (12 mL) and cooled to À70 °C. 1.6 M n-BuLi

in hexanes (0.69 mL, 1.1 mmol) was added over 35 min and the

reaction stirred at À70 °C for a further 40 min before adding n-pro-

pyl disulﬁde (0.17 mL, 1.1 mmol). After stirring at À70 °C for 5.5 h,

the reaction was warmed to rt, diluted with EtOAc and water, the

layers separated and the organic washed with dilute potassium

carbonate (5 mL). After drying (Na₂SO₄), ﬁltering and evaporating

in vacuo, the desired compound was isolated by chromatography

on silica gel with pentane (119 mg, 41%). ¹H NMR (CDCl₃), d: 1.05

(t, J = 7.5, 3H, CH₃), 1.61–1.73 (m, 2H, CH₂), 2.88 (t, J = 7.5, 2H,

CH₂), 7.37 (s, 1H, ArH), 7.56 (dd, J = 8.6, 1.8, 1H, ArH), 7.81 (d,

J = 8.2, 1H, ArH), 8.02 (d, J = 1.8, 1H, ArH).

evaporating in vacuo to leave the product as

a clear oil

(817 mg, quantitative). ¹H NMR (CDCl₃), d: 3.45 (br, 1H, OH),

4.98 (q, J = 6.8, 1H, CH), 7.35 (d, J = 8.6, 2H, ArH), 7.55 (d, J = 8.6,

2H, ArH).

4.24. 7-Bromo-naphthalen-2-ol (45)

Triphenylphosphine (500 mg, 2.9 mmol) was dissolved in MeCN

(5 mL), and bromine (0.15 mL, 2.9 mmol) was added at 0 °C whilst

stirring. The solution was allowed to warm up to rt, and 7-meth-

oxy-naphthalen-2-ol, 44 (490 mg, 2.8 mmol) was added portion-

wise. The solution was reﬂuxed for 2 h, and the solvent removed

in vacuo. The residue was heated to 250 °C in a sealed tube over-

night. After cooling to rt, the residue was puriﬁed by chromatogra-

phy using a stepped gradient of 10–20% EtOAc in heptane to yield

45 as a beige solid. Yield: 120 mg (19%). ¹H NMR (CDCl₃), d: 5.17

(br, 1H, OH), 7.06 (d, J = 2.5, 1H, ArH), 7.11 (dd, J = 8.7, 2.4, 1H,

ArH), 7.40 (dd, J = 8.7, 2.0, 1H, ArH), 7.63 (d, J = 8.9, 1H, ArH),

7.72 (d, J = 8.9, 1H, ArH), 7.84 (s, 1H, ArH). LC–MS: R_f= 2.01 min;

m/z 221/223 ([M+H]⁺, 100).

4.20. 6-Bromo-3-methylsulfanyl-benzo[b]thiophene (37)

Compound 25 (292 mg, 1.0 mmol) was dissolved in diethyl

ether (12 mL) and cooled to À70 °C. 1.6 M n-BuLi in hexanes

(0.69 mL, 1.1 mmol) was added over 45 min and the reaction

stirred at À70 °C for a further 30 min before adding methyl

disulﬁde (97

l

l, 1.1 mmol). After stirring at À70 °C for 4 h, the

reaction was warmed to rt, diluted with MTBE and washed with

saturated potassium carbonate (2 Â 5 mL). After drying (Na₂SO₄),

ﬁltering and evaporating in vacuo, the desired compound was

isolated by chromatography on silica gel with pentane

(111 mg, 43%). ¹H NMR (CDCl₃), d: 2.53 (s, 3H, CH₃), 7.15 (s,

1H, ArH), 7.53 (dd, 1H, ArH), 7.72 (d, J = 8.6, 1H, ArH), 8.00 (d,

J = 1.4, 1H, ArH).

4.25. 6-Bromo-3,4-dihydro-2H-naphthalen-1-one (48)

6-Aminotetralone (47, 500 mg, 3.1 mmol) was dissolved in 25%

HBr (1 mL). The mixture was cooled to 0 °C and a solution of

NaNO₂(263 mg, 3.8 mmol) in water (1 mL) was slowly added.

The reaction mixture was further added to a solution of CuBr

(458 mg, 3.2 mmol) in 48% HBr (1 mL) and the reaction was stirred

for 1.5 h while warming to rt. The solution was extracted with

EtOAc (3 Â 5 mL), dried over MgSO₄and the solvent was removed

in vacuo. The crude material was puriﬁed by column chromatogra-

phy (0–20% DCM in heptane) to afford the desired product

(435 mg, 74%). ¹H NMR (CDCl₃), d: 2.08–2.19 (m, 2H, CH₂), 2.65

(dd, J = 7.2, 5.9, 2H, CH₂), 2.96 (t, J = 5.9, 2H, CH₂), 7.42–7.47 (m,

2H, ArH), 7.89 (d, J = 8.8, 1H, ArH). LC–MS: R_f= 2.04 min; m/z

225/227 ([M+H]⁺, 100).

4.21. 1-(5-Bromo-benzo[b]thiophen-2-yl)-2,2,2-triﬂuoro-

ethanone (39)

5-Bromobenzo[b]thiophene (700 mg; 3.3 mmol) was dissolved

in dry Et₂O (14 mL) and placed under nitrogen ﬂow. 1.6 M nBuLi

in hexanes (2.25 mL, 3.6 mmol) was added dropwise, and the mix-

ture was stirred at rt for 5 min. The reaction was cooled to À70 °C

and N,N-dimethyl-triﬂuoroacetamide (0.42 mL; 3.6 mmol) was

added dropwise. The mixture was stirred at À70 °C for 2 h, then al-

lowed to warm up to rt, acidiﬁed with 1 M HCl to pH=1, extracted

with MTBE (3 Â 50 mL), dried (MgSO₄) and the solvent removed in

vacuo. The residue was puriﬁed by chromatography using 5%

EtOAc in heptane to afford the desired material as a yellow solid.

Yield: 717 mg (73%). ¹H NMR (CDCl₃), d: 7.68 (d, J = 1.83 Hz, 1H,

ArH), 7.79 (s, 1H, ArH), 8.15 (d, J = 1.83 Hz, 2H, ArH).

4.26. (6-Bromo-3,4-dihydro-naphthalen-1-yloxy)-triisopropyl-

silane (49)

4.22. 1-(5-Bromo-benzo[b]thiophen-2-yl)-2,2,2-triﬂuoro-

ethanol ( 40)

Under N₂atmosphere, 48 (418 mg, 1.9 mmol) was dissolved in

dry DCM (4.2 mL). NEt₃(0.47 mL, 3.3 mmol) was added, followed

by triisopropylsilyl triﬂate (0.6 mL, 2.2 mmol). The reaction was

stirred at rt for 2 h, washed with cold NaHCO₃(3 Â 2 mL), dried

over Na₂SO₄and evaporated in vacuo. The residue (845 mg,

119%) was sufﬁciently pure to be used directly for the next step.

¹H NMR (CDCl₃), d: 1.10–1.15 (m, 18H, CH(CH₃)₂), 1.16–1.33 (m,

3H, CH), 2.24–2.34 (m, 2H, CH₂), 2.73 (t, J = 7.9, 2H, CH₂), 5.19 (t,

J = 4.6, 1H, CH), 7.25–7.27 (m, 1H, ArH), 7.29–7.36 (m, 1H, ArH),

7.37–7.42 (m, 1H, ArH).

Compound 39 (717 mg, 2.3 mmol) was suspended in MeOH

(10 mL) and added to a solution of NaBH₄(380 mg; 10.0 mmol)

in 9:1 MeOH/1 M NaOH (13.4 mL). The reaction was stirred for

2 h at rt then water (20 mL) was added and the aqueous layer

was extracted with tert-butyl methyl ether (3 Â 50 mL), washed

with brine (1 Â 30 mL), dried (Na₂SO₄) and the solvent removed

in vacuo. The residue was puriﬁed by chromatography using a

1298

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

4.27. (6-Bromo-naphthalen-1-yloxy)-triisopropyl-silane (50)

(10 mL) to yield 63 as a pale yellow solid. Yield: 282 mg, 94%. ¹H

NMR (CDCl₃), d: 6.71 (d, J = 9.5, 1H, ArH), 7.33–7.37 (s, 1H, ArH),

7.41–7.46 (m, 1H, ArH), 7.52 (d, J = 1.8, 1H, ArH), 7.77 (d, J = 9.5,

1H, ArH), 11.15 (br, 1H, OH). LC–MS: R_f= 1.48 min; m/z 224/226

([M+H]⁺, 100).

Crude 49 (800 mg, 2.1 mmol) was dissolved in dioxane (8 mL)

and 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) (968 mg,

4.2 mmol) was added. The mixture was heated at 80 °C for

30 min, cooled to rt and diluted with heptane (16 mL). The solid

was ﬁltered off and washed with more heptane. The solution was

loaded onto a silica column and run with heptane to give the de-

sired compound (754 mg, 95%). ¹H NMR (CDCl₃), d: 1.16 (d,

J = 7.3, 18H, CH(CH₃)₂), 1.32–1.48 (m, 3H, CH), 6.88 (dd, J = 4.9,

3.8, 1H, ArH), 7.32 (d, J = 1.2, 1H, ArH), 7.34 (s, 1H, ArH), 7.53

(dd, J = 8.9, 1.9, 1H, ArH), 7.96 (d, J = 1.8, 1H, ArH), 8.13 (d, J = 9.0,

1H, ArH). LC–MS: R_f= 5.21 min; m/z 378/380 ([M+H]⁺, 100).

4.32. (6-Bromo-isoquinolin-1-yl)-bis-(4-methoxy-benzyl)-

amine (72)

Compound 71 (320 mg, 1.4 mmol) was dissolved in DMF (5 mL)

and NaH (60% in mineral oil, 126 mg, 3.2 mmol) was added por-

tionwise. The suspension was stirred for 10 min and para-

methoxybenzyl chloride (PMBCl, 493 mg, 3.2 mmol) was added

dropwise. The reaction was stirred at rt for 90 min. Water

(20 mL) was added and the aqueous layer was extracted with

EtOAc (3 Â 20 mL). The organic layer was washed with water

(2 Â 20 mL), brine (20 mL), dried (MgSO₄), ﬁltered, and the solvent

removed in vacuo. The residue was puriﬁed by chromatography

using a stepped gradient of 0–5% EtOAc in heptane to yield 72 as

a yellow glue. Yield: 295 mg, 44%.

4.28. 6-Bromonaphthalen-1-ol (51)

Compound 50 (786 mg, 2.07 mmol) was dissolved in NMP

(0.8 mL). To this solution was added a solution of NaOH (530 mg,

13.25 mmol) in water (0.53 mL) and MeOH (1.4 mL) and the reac-

tion mixture heated at 60 °C for 1.5 h. The methanol was evapo-

rated, the residue diluted with water (10 mL) and washed with

heptane (10 mL). The aqueous layer was acidiﬁed with 6 N HCl

(3 mL) and extracted with EtOAc (2 Â 10 mL). The combined or-

ganic phases were washed with water (3 Â 10 mL) and evaporated

to dryness. The desired product was isolated by chromatography

on silica gel using 0–20% EtOAc in heptane (342 mg, 74%). ¹H

NMR (CDCl₃), d: 5.31 (br, 1H, OH), 6.81 (dd, J = 5.7, 2.7, 1H, ArH),

7.33 (d, J = 3.0, 1H, ArH), 7.34 (s, 1H, ArH), 7.55 (dd, J = 9.0, 2.0,

1H, ArH), 7.97 (d, J = 2.0, 1H, ArH), 8.07 (d, J = 9.0, 1H, ArH).

¹H NMR (CDCl₃), d: 3.80 (s, 6H, CH₃), 4.51 (s, 4H, CH₂), 6.84

(d, J = 8.6, 4H, ArH), 7.11–7.19 (m, 5H, ArH), 7.56 (dd, J = 8.9, 2.0,

1H, ArH), 7.93 (d, J = 1.8, 1H, ArH), 8.11–8.18 (m, 2H, ArH).

LC–MS: R_f= 2.58 min; m/z 463, 465 ([M+H]⁺, 100).

4.33. General procedures: Synthesis of 4,4,5,5-tetramethyl-1,3,2-

dioxaborolane esters from aryl halides

Aryl halide (1 equiv), bis-pinacolato-diboron (1.5–3 equiv),

Pd(dppf)Cl₂(0.05–0.1 equiv), and KOAc (3–6 eq.) were suspended

in DMF (2–6 mL). The mixture was then heated at 90 °C for 2–

6 h, cooled to rt, diluted with H₂O (10 mL) and extracted with

EtOAc (3 Â 5 mL). The organic layer was dried (MgSO₄) and the sol-

vent removed in vacuo. The residue was puriﬁed by chromatogra-

phy using a stepped gradient of 0–10% EtOAc in heptane to yield

the desired boronic ester.

4.29. 6-Bromo-2-chloro-naphthalen-1-ol (56)

Compound 55 (90 mg, 0.4 mmol) was dissolved in DCM

(0.9 mL). To this solution, a mixture of bleach (0.25 mL, 0.4 mmol),

t-BuOH (57 ll, 0.6 mmol) and DCM (0.9 mL), which had previously

been stirred for 10 min, was added. After 30 min, the residual oxi-

dant was destroyed with saturated sodium thiosulfate solution

(0.5 mL) and the reaction acidiﬁed with 2 N HCl (0.5 mL). The lay-

ers were separated and the aqueous extracted with DCM (2 mL).

The combined organic phases were washed with water and puri-

ﬁed by chromatography on silica gel using heptane as solvent.

Yield: 58 mg (56%). ¹H NMR (CDCl₃), d: 6.03 (br, 1H, OH), 7.29 (d,

J = 3.0, 1H, ArH), 7.40 (s, 1H, ArH), 7.59 (dd, J = 9.0, 2.0, 1H, ArH),

7.95 (d, J = 2.0, 1H, ArH), 8.10 (d, J = 9.0, 1H, ArH).

4.33.1. [6-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-

benzofuran-3-yl]-methanol (17)

Compound 16 (84 mg, 0.37 mmol) was boronylated according

to the general procedure to give the desired compound (93 mg,

92%). ¹H NMR (CDCl₃), d: 1.37 (s, 12H, CH₃), 2.06 (s, 1H, OH),

4.82 (s, 2H, CH₂), 7.63 (dd, 1H, ArH), 7.65 (d, J = 8.6, 1H, ArH),

7.70 (s, 1H, ArH), 7.94 (s, 1H, ArH). HRMS (EI): m/z calcd for

C

₁₅H₁₇BO₃([M-H₂O+H]⁺): 256.1385; found: 256.1377.

4.30. 6-Bromo-1-diﬂuoromethoxy-2-ﬂuoro-naphthalene (59)

4.33.2. 6-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-

benzofuran-3-carboxylic acid amide (20)

NaF (30 mg, 0.72 mmol) was dissolved in o-xylene (18 mL) and

5-bromo-indan-1-one, 58 (2.53 g, 12.0 mmol) was added. The mix-

ture was reﬂuxed for 1 h under nitrogen. Trimethylsilyl ﬂuor-

osulfonyldiﬂuoroacetate (TFDA, 6 g, 24.0 mmol) was cautiously

added over 20 min and reﬂux continued for 2 h. Two further

batches of TFDA (2 Â 6 g, 2 Â 24 mmol) were added and reﬂux con-

tinued for 3 h, upon which the reaction was allowed to cool to rt.

The solvents were removed under vacuum and the residue puriﬁed

by chromatography using heptane to yield 59 as a brown solid.

Yield: 1.3 g, 37%. ¹H NMR (CDCl₃), d: 6.40–7.08 (m, 1H, CH),

7.32–7.44 (m, 1H, ArH), 7.59–7.72 (m, 2H, ArH), 8.00–8.10 (m,

2H, ArH). LC–MS: R_f= 2.37 min; m/z not observed.

Compound 19 (32 mg, 0.13 mmol) was boronylated according

to the general procedure to give the desired compound (32 mg,

83%). ¹H NMR (CD₃OD), d: 1.37 (s, 12H, CH₃), 7.71 (d, J = 7.7, 1H,

ArH), 7.89 (s, 1H, ArH), 8.07 (d, J = 7.7, 1H, ArH), 8.41 (s, 1H,

ArH). LC–MS: R_f= 1.87 min; m/z 288 ([M+H]⁺, 100).

4.33.3. 6-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-

benzo[b]thiophene-3-carbaldehyde (27)

Compound 26 (107 mg, 0.44 mmol) was boronylated according

to the general procedure to give the desired compound (103 mg,

81%). ¹H NMR (CDCl₃), d: 1.30 (s, 12H, CH₃), 7.84 (dd, J = 8.2, 0.9,

1H, ArH), 8.28–8.31 (m, 2H, ArH), 8.58 (dd, J = 8.2, 0.9, 1H, ArH),

10.07 (s, 1H, CHO). LC–MS: R_f= 2.36 min; m/z 289 ([M+H]⁺, 100).

4.31. 7-Bromo-quinolin-2-ol (63)

7-Bromo-2-chloro-quinoline 62 (300 mg; 1.3 mmol) was sus-

pended in 2 M NaOH (2 mL) and heated at 190 °C in the microwave

reactor (150 Watt, 250 psi) for 30 min. The resulting precipitate

was diluted with water (5 mL), ﬁltered and washed with water

4.33.4. 2,2,3,3,3-Pentaﬂuoro-1-[6-(4,4,5,5-tetramethyl-[1,3,2]

dioxaborolan-2-yl)-benzo[b]thiophen-3-yl]-propan-1-ol ( 31)

Compound -30 (71 mg, 0.2 mmol) was boronylated according

to the general procedure to give the desired compound (51 mg,

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

1299

62%). ¹H NMR (CDCl₃), d: 1.38 (s, 12H, CH₃), 3.21 (d, J = 5.3, 1H, OH),

4.33.12. 6-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-

naphthalen-1-ol (52)

5.53 (dt, J = 17.1, 5.8, 1H, CH), 7.70–7.77 (m, 3H, ArH), 8.83 (s, 1H,

ArH). ¹⁹F NMR (CDCl₃), d: À128.7 (d, J = 275, 1F, CF₂), À120.8 (d,

J = 275, 1F, CF₂), À81.4 (s, 3F, CF₃).

Compound 51 (40 mg, 0.2 mmol) was boronylated according to

the general procedure to give the title compound (37 mg, 68%). ¹H

NMR (CDCl₃), d: 1.33 (s, 12H, CH₃), 5.36 (br, 1H, OH), 6.79 (dd,

J = 7.5, 0.9, 1H, ArH), 7.22 (t, J = 3.0, 1H, ArH), 7.40 (t, J = 8.4, 1H,

ArH), 7.78 (dd, J = 8.5, 1.1, 1H, ArH), 8.07 (d, J = 8.5, 1H, ArH),

8.27 (s, 1H, ArH).

4.33.5. 2,2,2-Triﬂuoro-1-[6-(4,4,5,5-tetramethyl-[1,3,2]

dioxaborolan-2-yl)-benzo[b]thiophen-3-yl]-ethanol ( 34)

Compound -33 (40 mg, 0.13 mmol) was boronylated according

to the general procedure to give the desired compound (39 mg,

84%) as a white solid. ¹H NMR (CDCl₃), d: 1.38 (s, 12H, CH₃), 2.90

(br, 1H, OH), 5.49 (m, 1H, CH), 7.77 (s, 1H, ArH), 7.80–7.91 (m,

2H, ArH), 8.37 (s, 1H, ArH). LC–MS: R_f= 2.36 min; m/z 359

([M+H]⁺, 100).

4.33.13. 2-Chloro-6-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-

yl)-naphthalen-1-ol (57)

Compound 56 (34 mg, 0.13 mmol) was boronylated according

to the general procedure to give the title compound (29 mg,

72%). ¹H NMR (CDCl₃), d: 1.41 (s, 12H, CH₃), 6.02 (br, 1H, OH),

7.36 (d, J = 3.0, 1H, ArH), 7.43 (d, J = 9.0, 1H, ArH), 7.89 (d, J = 8.4,

1H, ArH), 8.20 (d, J = 8.4, 1H, ArH), 8.31 (s, 1H, ArH).

4.33.6. (R)-2,2,2-Triﬂuoro-1-[6-(4,4,5,5-tetramethyl-[1,3,2]

dioxaborolan-2-yl)-benzo[b] thiophen-3-yl]-ethanol (R-34)

Compound R-33 was boronylated according to the general pro-

cedure to give a white solid that was used immediately in the next

step. ¹H NMR (CDCl₃), d: 1.30 (s, 12H, CH₃), 2.94 (d, J = 5.0, 1H, OH),

5.37–5.46 (m, 1H, CH), 7.70 (s, 1H, ArH), 7.71–7.76 (m, 1H, ArH),

7.78–7.84 (m, 1H, ArH), 8.29 (s, 1H, ArH). LC–MS: R_f= 2.33 min;

m/z not observed.

4.33.14. 2-(5-Diﬂuoromethoxy-6-ﬂuoro-naphthalen-2-yl)-

4,4,5,5-tetramethyl-[1,3,2]-dioxa borolane (60)

Compound 59 (240 mg, 0.8 mmol) was boronylated according

to the general procedure to give the title compound (111 mg,

39%). ¹H NMR (CDCl₃), d: 1.40 (s, 12H, CH₃), 6.39–7.04 (m, 1H,

CH), 7.29–7.40 (m, 1H, ArH), 7.79 (dd, J = 9.0, 5.0, 1H, ArH), 7.96

(d, J = 8.4, 1H, ArH), 8.14 (d, J = 8.5, 1H, ArH), 8.36 (s, 1H, ArH).

LC–MS: R_f= 1.69 min; m/z not observed.

4.33.7. 4,4,5,5-Tetramethyl-2-(3-propylsulfanyl-

benzo[b]thiophen-6-yl)-[1,3,2]-dioxa borolane (36)

Compound 35 (68 mg, 0.24 mmol) was boronylated according

to the general procedure to give the title compound (45 mg, 56%)

as a white solid. ¹H NMR (CDCl₃), d: 1.00 (t, J = 7.3, 3H, CH₃), 1.38

(s, 12H, CH₃), 1.54–1.71 (m, 2H, CH₂), 2.85 (t, J = 7.3, 2H, CH₂),

7.46 (s, 1H, ArH), 7.84 (dd, J = 8.6, 1.8, 1H, ArH), 7.94 (d, J = 8.2,

1H, ArH), 8.35 (d, J = 1.8, 1H, ArH).

4.33.15. 7-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-

quinolin-2-ol (64)

Compound 63 (282 mg; 1.3 mmol) was boronylated according

to the general procedure to give the title compound. ¹H NMR

(CDCl₃), d: 1.38 (s, 12H, CH₃), 6.72 (d, J = 9.6, 1H, ArH), 7.50–7.66

(m, 3H, ArH), 7.78 (d, J = 9.6, 1H, ArH), 9.44 (br, 1H, OH). LC–MS:

R_f= 1.79 min; m/z 272 ([M+H]⁺, 100).

4.33.8. 4,4,5,5-Tetramethyl-2-(3-methylsulfanyl-

benzo[b]thiophen-6-yl)-[1,3,2]-dioxaborolane (38)

Compound 37 (111 mg, 0.43 mmol) was boronylated according

to the general procedure to give the title compound (105 mg, 80%)

as a white solid. ¹H NMR (CDCl₃), d: 1.38 (s, 12H, CH₃), 2.53 (s, 3H,

CH₃), 7.27 (s, 1H, ArH), 7.84–7.87 (m, 2H, ArH), 8.35 (s, 1H, ArH).

4.33.16. 6-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-

quinolin-2-ol (67)

6-Bromoquinolin-2-ol (244 mg; 1.1 mmol) was boronylated

according to the general procedure to give the title compound

(184 mg; 62%). ¹H NMR (CDCl₃), d: 1.38 (s, 12H, CH₃), 6.71 (d,

J = 9.59 Hz, 1H, ArH), 7.35 (d, J = 8.22 Hz, 1H, ArH), 7.83 (d,

J = 9.59 Hz, 1H, ArH), 7.92 (dd, J = 8.22, 1.22 Hz, 1H, ArH), 8.06 (s,

1H, ArH), 11.50–11.72 (m, 1H, NH). LC–MS: R_f= 1.77 min; m/z

272 ([M+H]⁺, 100).

4.33.9. 2,2,2-Triﬂuoro-1-[5-(4,4,5,5-tetramethyl-

[1,3,2]dioxaborolan-2-yl)-benzo[b]thiophen-2-yl]-ethanol

( 40a)

Compound 40 (384 mg, 1.2 mmol) was boronylated according

to the general procedure to give the desired compound (320 mg,

72%) as a white solid. ¹H NMR (CDCl₃), d: 1.38 (s, 12H, CH₃),

2.90–3.16 (m, 1H, OH), 5.20–5.56 (m, 1H, CH), 7.40 (s, 1H, ArH),

7.67–7.98 (m, 2H, ArH), 8.26 (s, 1H, ArH); LC–MS: R_f= 2.36 min;

m/z 359 ([M+H]⁺, 100).

4.33.17. 6-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-2H-

isoquinolin-1-one (70)

Compound 69 (100 mg; 0.45 mmol) was boronylated according to

the general procedure to give the title compound (56 mg; 46%). ¹H

NMR (CD₃OD), d: 1.38 (s, 12H, CH₃), 6.70 (d, J = 7.0, 1H, ArH), 7.18

(d, J = 7.2, 1H, ArH), 7.82 (d, J = 8.1, 1H, ArH), 8.04 (s, 1H, ArH), 8.27

(d, J = 8.1, 1H, ArH). LC–MS: R_f= 0.91 min; m/z 190 ([M+H]⁺, 100).

4.33.10. 2,2,2-Triﬂuoro-1-[4-(4,4,5,5-tetramethyl-[1,3,2]

dioxaborolan-2-yl)-phenyl]-ethanol ( 43)

Compound 42 (255 mg, 1.0 mmol) was boronylated according

to the general procedure to give the title compound (199 mg,

66%) as a white solid. ¹H NMR (CDCl₃), d: 1.36 (s, 12H, CH₃),

2.96 (br, 1H, OH), 5.02 (q, J = 6.8, 1H, CH), 7.47 (d, J = 8.2, 2H,

ArH), 7.85 (d, J = 8.2, 2H, ArH). LC–MS: R_f= 2.16 min; m/z not

observed.

4.33.18. Bis-(4-methoxy-benzyl)-[6-(4,4,5,5-tetramethyl-

[1,3,2]dioxaborolan-2-yl)-isoquinolin-1-yl]-amine (73)

Compound 72 (295 mg; 0.64 mmol) was boronylated according to

1

the general procedure to give the title compound (101 mg, 31%). H

NMR (CDCl₃), d: 1.40 (s, 12H, CH₃), 3.79 (s, 6H, CH₃), 4.52 (s, 4H, CH₂),

6.82 (d, J = 8.6, 4H, ArH), 7.14 (d, J = 9.1, 4H, ArH), 7.28 (s, 1H, ArH),

7.87 (d, J = 9.1, 1H, ArH), 8.14 (d, J = 5.4, 1H, ArH), 8.23–8.30 (m, 2H,

ArH). LC–MS: R_f= 1.62 min; m/z 511 ([M+H]⁺, 100). HRMS (EI): m/z

calcd for C₃₁H₃₅BN₂O₄([M+H]⁺): 510.2804; found: 510.2807.

4.33.11. 7-(4,4,5,5-Tetramethyl-[1,3,2]dioxaborolan-2-yl)-

naphthalen-2-ol (46)

Compound 45 (120 mg; 0.55 mmol) was boronylated according

to the general procedure to give the title compound (35 mg, 24%).

¹H NMR (CDCl₃), d: 1.35 (s, 12H, CH₃), 5.52 (br, 1H, OH), 7.14 (d,

J = 2.5, 1H, ArH), 7.19 (dd, J = 8.7, 2.4, 1H, ArH), 7.70 (dd, J = 8.7,

2.0, 1H, ArH), 7.75 (m, 2H, ArH), 8.21 (s, 1H, ArH). LC–MS:

R_f= 2.17 min; m/z not observed.

4.33.19. 2-(6-Fluoro-naphthalen-2-yl)-4,4,5,5-tetramethyl-

[1,3,2]dioxaborolane (76)

Compound 75 (300 mg; 1.3 mmol) was boronylated according

to the general procedure to give the title compound (191 mg,

1300

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

54%). ¹H NMR (CDCl₃), d: 1.28 (s, 12H, CH₃), 7.14 (td, J = 8.9, 2.7, 1H,

ArH), 7.32 (dd, J = 9.8, 2.5, 1H, ArH), 7.65 (d, J = 8.2, 1H, ArH), 7.72–

7.79 (m, 2H, ArH), 8.26 (s, 1H, ArH). LC–MS: R_f= 2.67 min; m/z not

observed.

4.34.4. 6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-pyridin-4-

yl-1H-imidazol-4-yl}-benzofuran-3-carboxylic acid amide (1d)

Compounds 20 (20 mg, 0.07 mmol) and 9 (12 mg, 0.03 mmol)

were coupled according to the general procedure to give the de-

sired compound (0.7 mg, 5%) as a yellow glassy solid. ¹H NMR

(CD₃OD), d: 2.37 (s, 6H, N(CH₃)₂), 2.81 (t, J = 5.40 Hz, 2H, CH₂),

4.19 (t, J = 5.44 Hz, 2H, CH₂), 7.10 (d, J = 9.0 Hz, 2H, ArH), 7.49

(dd, J = 8.2, 1.4 Hz, 1H, ArH), 7.53–7.63 (m, 2H, ArH), 7.73 (d,

J = 0.8 Hz, 1H, ArH), 7.92–8.00 (m, 2H, ArH), 8.08–8.17 (m, 1H,

ArH), 8.36–8.46 (m, 2H, ArH), 8.50–8.59 (m, 1H, ArH). LC–MS:

R_f= 2.23 min; m/z 468 ([M+H]⁺, 100), 234. HRMS (EI): m/z calcd

for C₂₇H₂₆N₅O₃([M+H]⁺): 468.2036; found: 468.2031.

4.33.20. 6-(4,4,5,5-Tetramethyl-[1,3,2]-dioxaborolan-2-yl)-

naphthalen-2-carboxylic acid (79)

6-Bromonaphthalene-2-carboxylic acid (500 mg; 2.0 mmol)

was boronylated using the general procedure to give the desired

compound (478 mg; 80%). ¹H NMR (CD₃OD), d: 1.40 (s, 12H,

CH₃), 7.79–7.90 (m, 1H, ArH), 7.93–8.11 (m, 3H, ArH), 8.37 (s, 1H,

ArH), 8.61 (s, 1H, ArH). LC–MS: R_f= 2.17 min; m/z 299 ([M+H]⁺,

5), 340 (100). HRMS (EI): m/z calcd for C₁₇H₁₉BO₄([M+H]⁺):

298.1491; found: 298.1483.

4.34.5. 6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-pyridin-4-

yl-3H-imidazol-4-yl}-benzo[b]thiophene-3-carbaldehyde (1e)

Compounds 27 (96 mg, 0.33 mmol) and 9 (100 mg, 0.26 mmol)

were coupled according to the general procedure to give the

desired compound (63 mg, 51%). ¹H NMR (acetone-d₆), d: 2.15

(s, 6H, N(CH₃)₂), 2.57 (t, 2H, J = 5.9 Hz, CH₂), 4.03 (t, 2H, J = 5.9 Hz,

CH₂), 6.94 (d, 2H, J = 9.1 Hz, ArH), 7.35–7.50 (m, 2H, ArH), 7.57–

7.69 (m, 1H, ArH), 7.96 (d, 2H, J = 8.6 Hz, ArH), 8.13–8.23 (m, 1H,

ArH), 8.33 (d, 2H, J = 4.1 Hz, ArH), 8.39–8.58 (m, 1H, ArH), 8.68–

8.79 (m, 1H, ArH), 10.10 (s, 1H, CH), 11.80 (br s, 1H, NH), LC–MS:

R_f= 2.39 min; m/z 469 ([M+H]⁺, 10), 235 (100). HRMS (EI): m/z

calcd for C₂₇H₂₄N₄O₂S ([M+H]⁺): 469.1698; found: 469.1682.

4.34. Suzuki coupling of 4-bromoimidazole compounds

{2-[4-(4-Bromo-5-pyridin-4-yl-1H-imidazol-2-yl)-phenoxy]-

ethyl}-dimethyl-amine (9)¹⁸(1 equiv), the appropriate boronic

ester (1.2–2 equiv), PPh₃(0.1 equiv), and K₂CO₃(8–10 equiv) were

suspended in a 2:1 mixture of DME:H₂O (3–9 mL). The suspension

was stirred vigorously whilst de-gassing with N₂for 20 min before

adding Pd(OAc)₂(0.01 equiv). The mixture was then reﬂuxed for

2 h to overnight, cooled to rt, acidiﬁed to pH=1 with 1 M HCl

and washed with EtOAc (3 Â 5 mL). The aqueous layer was basiﬁed

with 2 M NaOH to pH=14 and extracted with EtOAc (3 Â 5 mL).

This organic layer was dried (MgSO₄) and the solvent removed un-

der vacuum. The residue was puriﬁed by preparative HPLC to yield

the desired product.

4.34.6. (6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-pyridin-

4-yl-3H-imidazol-4-yl}-benzo[b]thiophen-3-yl)-methanol (1f)

Compound 1e (13 mg, 28

(0.5 mL) before adding sodium borohydride (2 mg, 53

l

mol) was partly dissolved in ethanol

mol). After

l

4.34.1. (2-{4-[4-(3,4-Dichloro-phenyl)-5-pyridin-4-yl-1H-

imidazol-2-yl]-phenoxy}-ethyl)-dimethyl-amine (1a)

Compound 9 (50 mg; 0.13 mmol) and 3,4-dichlorophenyl boro-

nic acid 11 (50 mg; 0.26 mmol) were coupled according to the gen-

eral procedure to give the desired compound (7 mg, 12%). ¹H NMR

(CD₃OD), d: 3.01 (s, 6H, N(CH₃)₂), 3.65 (t, J = 4.8, 2H, CH₂), 4.45 (t,

J = 4.8, 2H, CH₂), 7.20 (d, J = 9.1, 2H, ArH), 7.54 (dd, J = 8.2, 2.3,

1H, ArH), 7.72 (d, J = 8.2, 1H, ArH), 7.85 (s, 1H, ArH), 8.06 (d,

J = 9.1, 2H, ArH), 8.12 (d, J = 6.8, 2H, ArH), 8.62 (d, J = 6.8, 2H,

ArH). LC–MS: R_f= 2.51 min; m/z 453, 455, 457 ([M+H]⁺, 100).

HRMS (EI): m/z calcd for C₂₄H₂₃Cl₂N₄O ([M+H]⁺): 453.1249; found:

453.1244.

stirring for 2 h at rt, water (1 mL) and 2 N HCl (1 drop) were added

and the reaction extracted with EtOAc (1 mL). The aqueous was basi-

ﬁed with 2 N NaOH and extracted with EtOAc/MeOH (2 Â 1 mL). The

combined organic phases were washed with water (1 mL) and evap-

orated to dryness to leave the desired compound (10 mg, 75%). ¹H

NMR (CD₃OD), d: 2.41 (s, 6H, N(CH₃)₂), 2.85 (t, 2H, J = 5.2 Hz, CH₂),

4.23 (t, 2H, J = 5.4 Hz, CH₂), 4.85 (s, 2H, CH₂), 7.13 (d, 2H, J = 8.6 Hz,

ArH), 7.53 (d, 1H, J = 8.2 Hz, ArH), 7.57–7.63 (m, 3H, ArH), 7.97–

8.03 (m, 3H, ArH), 8.10 (s, 1H, ArH), 8.44 (d, 2H, J = 5.9 Hz, ArH).

LC–MS: R_f= 2.29 min; m/z 471 ([M+H]⁺, 10), 236 (100). HRMS (EI):

m/z calcd for C₂₇H₂₆N₄O₂S ([M+H]⁺): 471.1854; found: 471.1844.

4.34.7. 1-(6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-

pyridin-4-yl-3H-imidazol-4-yl}-benzo[b]thiophen-3-yl)-

propan-1-ol ( 1g)

4.34.2. (2-{4-[5-(3-Chloro-4-ﬂuoro-phenyl)-4-pyridin-4-yl-1H-

imidazol-2-yl]-phenoxy}-ethyl)-dimethyl-amine (1b)

Compound 9 (40 mg; 0.09 mmol) and 3-chloro-4-ﬂuorophenyl

boronic acid 12 (32 mg; 0.19 mmol) were coupled using the gen-

eral procedure to give the desired product (3 mg; 7%). ¹H NMR

(CD₃OD), d: 3.02 (s, 6H, N(CH₃)₂), 3.65 (t, J = 4.8, 2H, CH₂), 4.45 (t,

J = 4.8, 2H, CH₂), 7.20 (d, J = 8.6, 2H, ArH), 7.45 (t, J = 8.9, 2H,

ArH), 7.57 (br, 1H, ArH), 7.81 (d, J = 8.2, 1H, ArH), 8.06 (t, J = 8.4,

4H, ArH), 8.61 (d, J = 6.4, 2H, ArH). LC–MS: R_f= 2.44 min; m/z 437

([M+H]⁺, 10), 219 (100).

Compounds 28 (24 mg, 75 lmol) and 9 (25 mg, 60 lmol) were

coupled according to the general procedure to give the desired com-

pound (17 mg, 54%). ¹H NMR (CD₃OD), d: 1.06 (t, 3H, J = 7.0 Hz, CH₃),

1.92–2.13 (m, 2H, CH₂), 3.06 (s, 6H, N(CH₃)₂), 3.70 (br. s, 2H, CH₂),

4.51 (br. s, 2H, CH₂), 5.06 (t, 1H, J = 6.4 Hz, CH), 7.27 (d, 2H, J = 8.6 Hz,

ArH), 7.63 (d, 1H, J = 8.2 Hz, ArH), 7.69 (s, 1H, ArH), 8.11–8.19 (m, 5H,

ArH), 8.24 (s, 1H, ArH), 8.63 (d, 2H, J = 5.9 Hz, ArH). LC–MS:

R_f= 2.44 min; m/z 499 ([M+H]⁺, 10), 250 (100). HRMS (EI): m/z calcd

for C₂₉H₃₀N₄O₂S ([M+H]⁺): 499.2167; found: 499.2181.

4.34.3. (6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-pyridin-

4-yl-3H-imidazol-4-yl}-benzofuran-3-yl)-methanol (1c)

4.34.8. 1-(6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-

pyridin-4-yl-3H-imidazol-4-yl}-benzo[b]thiophen-3-yl)-

2,2,3,3,3-pentaﬂuoro-propan-1-ol ( 1h)

Compound 17 (60 mg, 0.22 mmol) and 9 (50 mg, .0.13 mmol)

were coupled according to the general procedure to give the de-

sired compound (20 mg, 50%). ¹H NMR (CD₃OD), d: 2.42 (s, 6H,

N(CH₃)₂), 2.87 (t, J = 5.3, 2H, CH₂), 4.22 (t, J = 5.3, 2H, CH₂), 4.83

(s, 2H, CH₂), 7.12 (d, J = 8.9, 2H, ArH), 7.42 (d, J = 7.9, 1H, ArH),

7.58 (d, J = 3.6, 2H, ArH), 7.68 (s, 1H, ArH), 7.80 (d, J = 7.9, 1H,

ArH), 7.84 (s, 1H, ArH), 7.99 (d, J = 8.9, 2H, ArH), 8.43 (d, J = 5.0,

2H, ArH). LC–MS: R_f= 2.23 min; m/z 455 ([M+H]⁺, 100), 228. HRMS

Compounds 31 (51 mg, 0.14 mmol) and 9 (41 mg, 0.11 mmol)

were coupled according to the general procedure to give the de-

sired compound (42 mg, 68%). ¹H NMR (CD₃OD), d: 3.02 (s, 6H,

N(CH₃)₂), 3.66 (t, J = 5.2, 2H, CH₂), 4.46 (t, J = 5.2, 2H, CH₂), 5.67

(dd, J = 19.3, 6.1, 1H, CH), 7.22 (d, J = 9.1, 2H, ArH), 7.63 (d, J = 8.6,

1H, ArH), 7.97 (s, 1H, ArH), 8.08 (d, J = 8.6, 2H, ArH), 8.13 (d,

J = 6.8, 2H, ArH), 8.20–8.25 (m, 2H, ArH), 8.58 (d, J = 6.8, 2H, ArH).

LC–MS: R_f= 2.64 min; m/z 589 ([M+H]⁺, 10), 295 (100). HRMS

(EI): m/z calcd for

C

₂₇H₂₆N₄O₃([M+H]⁺): 455.2083; found:

455.2087.

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

1301

(EI): m/z calcd for C₂₉H₂₅F₅N₄O₂S ([M+H]⁺): 589.1696; found:

589.1691.

desired compound (43 mg, 47%). ¹H NMR (CD₃OD), d: 2.61 (s, 3H,

CH₃), 3.02 (s, 6H, N(CH₃)₂), 3.66 (t, J = 5.2, 2H, CH₂), 4.46 (t,

J = 5.2, 2H, CH₂), 7.22 (d, J = 8.6, 2H, ArH), 7.54 (s, 1H, ArH), 7.64

(dd, J = 8.4, 1.6, 1H, ArH), 8.01 (d, J = 8.6, 1H, ArH), 8.06–8.12 (m,

4H, ArH), 8.21 (s, 1H, ArH), 8.57 (d, J = 6.8, 2H, ArH). LC–MS:

R_f= 2.80 min; m/z 487 ([M+H]⁺, 10), 244 (100). HRMS (EI): m/z

calcd for C₂₇H₂₆N₄OS₂([M+H]⁺): 487.1626; found: 487.1608.

4.34.9. 1-(6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-

pyridin-4-yl-1H-imidazol-4-yl}-benzo[b]thiophen-3-yl)-2,2,2-

triﬂuoro-ethanol ( 1i)

Compounds 34 (45 mg, 0.12 mmol) and 9 (24 mg, 60 lmol)

were coupled according to the general procedure to give the de-

sired compound as its TFA salt (6.7 mg, 17%). ¹H NMR (CD₃OD),

d: 3.02 (s, 6H, N(CH₃)₂), 3.65 (t, J = 5.2, 2H, CH₂), 4.47 (t, J = 5.2,

2H, CH₂), 5.55 (t, J = 6.4, 1H, CH), 7.22 (d, J = 9.1, 2H, ArH), 7.63

(d, J = 8.6, 1H, ArH), 7.96 (s, 1H, ArH), 8.09 (d, J = 9.1, 2H, ArH),

8.13 (d, J = 6.8, 2H, ArH), 8.18–8.27 (m, 2H, ArH), 8.57 (d, J = 6.4,

2H, ArH). LC–MS: R_f= 2.61 min; m/z 539 ([M+H]⁺, 10), 270 (100).

4.34.14. (2-{4-[5-(3-Methanesulﬁnyl-benzo[b]thiophen-6-yl)-

4-pyridin-4-yl-1H-imidazol-2-yl]-phenoxy}-ethyl)-dimethyl-

amine (1m)

Compound 1l (69 mg, 80

lmol) was dissolved in water (1 mL)

and oxone^Ò(26 mg, 40

l

mol) added. After 15 min, the reaction

was basiﬁed with a little 2 N NaOH, evaporated to dryness and

the residue extracted with EtOAc/MeOH (2 Â 1 mL). The desired

product was isolated by chromatography on silica gel using 7:2:1

EtOAc/MeOH/TEA. Yield: 20 mg (50%). ¹H NMR (CD₃OD), d: 3.02

(s, 6H, N(CH₃)₂), 3.12 (s, 3H, CH₃), 3.66 (t, J = 5.2, 2H, CH₂), 4.46

(t, J = 5.2, 2H, CH₂), 7.22 (d, J = 8.6, 2H, ArH), 7.73 (dd, J = 8.5, 1.4,

1H, ArH), 8.05–8.15 (m, 4H, ArH), 8.30 (d, J = 8.4, 1H, ArH), 8.36

(d, J = 1.4, 1H, ArH), 8.42 (s, 1H, ArH), 8.57 (d, J = 6.8, 2H, ArH).

LC–MS: R_f= 2.32 min; m/z 503 ([M+H]⁺, 10), 252 (100). HRMS

(EI): m/z calcd for C₂₇H₂₆N₄O₂S₂([M+H]⁺): 503.1575; found:

503.1565.

4.34.10. (R)-1-(6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-

pyridin-4-yl-1H-imidazol-4-yl}-benzo[b]thiophen-3-yl)-2,2,2-

triﬂuoro-ethanol (R-1i)

Compounds R-34 (30 mg, 80 lmol) and 9 (24 mg, 60 lmol)

were coupled according to the general procedure to give the de-

sired compound as its TFA salt (25 mg, 64%). Chiral HPLC (method

1): free base: 91% R-isomer, t_r34.51 (9% S-isomer). ¹H NMR

(CD₃OD), d ppm 3.02 (s, 6H, N(CH₃)₂), 3.66 (t, 2H, CH₂), 4.46 (t,

2H, J = 4.8 Hz, CH₂), 5.49–5.62 (m, 1H, CH), 7.21 (d, 2H, J = 6.8 Hz,

ArH), 7.63 (dd, 1H, J = 8.6, 1.4 Hz, ArH), 7.95 (s, 1H, ArH), 8.08 (d,

2H, J = 8.6 Hz, ArH), 8.12 (d, 2H, J = 6.8 Hz, ArH), 8.21–8.26 (m,

2H, ArH), 8.56 (d, 2H, J = 6.8 Hz, ArH); LC–MS: R_f= 2.47 min; m/z

539 ([M+H]⁺, 10), 270 (100). HRMS (EI): m/z calcd for

4.34.15. 1-(5-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-

pyridin-4-yl-3H-imidazol-4-yl}-benzo[b]thiophen-2-yl)-2,2,2-

triﬂuoro-ethanol ( 1n)

C

₂₈H₂₅F₃N₄O₂S ([M+H]⁺): 539.1728; found: 539.1729.

Compound 9 (63 mg; 0.16 mmol) and boronate ester 40a

(88 mg; 0.24 mmol) were coupled using the general procedure.

The residue was puriﬁed by preparative LC to give the desired

product (13 mg; 13%). ¹H NMR (CD₃OD), d: 3.02 (s, 6H, N(CH₃)₂),

3.66 (t, J = 5.2, 2H, CH₂), 4.46 (t, J = 5.2, 2H, CH₂), 5.44–5.55 (m,

1H, CH), 7.22 (d, J = 9.0, 2H, ArH), 7.53–7.59 (m, 2H, ArH), 8.03–

8.14 (m, 6H, ArH), 8.56 (d, J = 7.0, 2H, ArH). LC–MS: R_f= 2.51 min;

m/z 539 ([M+H]⁺, 10), 270 (100). HRMS (EI): m/z calcd for

4.34.11. Dimethyl-(2-{4-[5-(3-propylsulfanyl-

benzo[b]thiophen-6-yl)-4-pyridin-4-yl-1H-imidazol-2-yl]-

phenoxy}-ethyl)-amine (1j)

Compounds 36 (45 mg, 0.13 mmol) and 9 (43 mg, 0.11 mmol)

were coupled according to the general procedure to give the de-

sired compound (42 mg, 74%). ¹H NMR (CD₃OD), d: 1.06 (t,

J = 7.3, 3H, CH₃), 1.60–1.77 (m, 2H, CH₂), 2.97 (t, J = 7.3, 2H, CH₂),

3.02 (s, 6H, N(CH₃)₂), 3.65 (t, J = 4.8, 2H, CH₂), 4.46 (t, J = 4.6, 2H,

CH₂), 7.22 (d, J = 9.0, 2H, ArH), 7.65 (d, J = 8.4, 1H, ArH), 7.72 (s,

1H, ArH), 8.03–8.24 (m, 6H, ArH), 8.58 (d, J = 5.6, 2H, ArH). LC–

MS: R_f= 2.98 min; m/z 515 ([M+H]⁺, 10), 258 (100). HRMS (EI):

m/z calcd for C₂₉H₃₀N₄OS₂([M+H]⁺): 515.1939; found: 515.1940.

C

₂₈H₂₆F₃N₄O₂S ([M+H]⁺): 539.1723; found: 539.1730.

4.34.16. -1-(4-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-

pyridin-4-yl-3H-imidazol-4-yl}-phenyl)-2,2,2-triﬂuoro-ethanol

( 1o)

Compounds 43 (32 mg, 0.1 mmol) and 9 (34 mg, 90 lmol)

were coupled according to the general procedure to give the de-

sired compound (21 mg, 50%). ¹H NMR (CD₃OD), d: 2.64 (s, 6H,

N(CH₃)₂), 3.15 (t, J = 5.2, 2H, CH₂), 4.30 (t, J = 5.2, 2H, CH₂), 5.13

(q, J = 6.8, 1H), 7.14 (d, J = 9.1, 2H, ArH), 7.56–7.64 (m, 6H, ArH),

7.99 (d, J = 8.6, 2H, ArH), 8.46 (d, J = 4.5, 2H, ArH). LC–MS:

R_f= 2.41 min; m/z 483 ([M+H]⁺, 10), 242 (100). HRMS (EI): m/z

calcd for C₂₆H₂₅F₃N₄O₂([M+H]⁺): 483.2008; found: 483.2016.

4.34.12. Dimethyl-[2-(4-{5-[3-(propane-1-sulﬁnyl)-

benzo[b]thiophen-6-yl]-4-pyridin-4-yl-1H-imidazol-2-yl}-

phenoxy)-ethyl]-amine (1k)

Compound 1j (60 mg, 70 lmol) was dissolved in water (1.5 mL)

and acetone (1.5 mL). Oxone^Ò(43 mg, 0.1 mmol) was subsequently

added and after 10 min, the reaction was basiﬁed with saturated

K₂CO₃, brine added and the reaction mixture extracted with

EtOAc/MeOH (2 Â 1 mL). The desired product was isolated by chro-

matography on silica gel using 10:1:1 EtOAc/MeOH/TEA.

Yield = 8 mg (21%). ¹H NMR (CD₃OD), d: 1.12 (t, J = 7.4, 3H, CH₃),

1.71–1.88 (m, 2H, CH₂), 3.03 (s, 6H, N(CH₃)₂), 3.21–3.28 (m, 2H,

CH₂), 3.66 (t, J = 4.8, 2H, CH₂), 4.47 (t, J = 4.6, 2H, CH₂), 7.23 (d,

J = 9.0, 1H, ArH), 7.73 (d, J = 8.4, 1H, ArH), 8.06–8.16 (m, 4H, ArH),

8.28 (d, 1H, J = 8.4, ArH), 8.37 (s, 1H, ArH), 8.41 (s, 1H, ArH), 8.60

(br, 2H, ArH), 2H concealed by solvent peak. LC–MS: R_f= 2.51 min;

m/z 531 ([M+H]⁺, 10), 266 (100). HRMS (EI): m/z calcd for

C₂₉H₃₁N₄O₂S₂([M+H]⁺): 531.1889; found: 531.1882.

4.34.17. 7-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-pyridin-

4-yl-1H-imidazol-4-yl}-naphthalen-2-ol (1p)

Compound 9 (48 mg; 0.12 mmol) was coupled to compound 46

(40 mg, 0.15 mmol) using the general procedure to give the desired

compound as a beige solid (13 mg; 24%). ¹H NMR (CD₃OD), d: 2.45

(s, 6H, N(CH₃)₂), 2.92 (t, J = 5.1, 2H, CH₂), 4.22 (t, J = 5.2, 2H, CH₂),

7.06–7.18 (m, 4H, ArH), 7.34 (d, J = 8.6, 1H, ArH), 7.59 (br, 2H,

ArH), 7.74–7.86 (m, 3H, ArH), 7.98 (d, J = 8.9, 2H, ArH), 8.41 (d,

J = 4.3, 2H, ArH). LC–MS: R_f= 2.42 min; m/z 451 ([M+H]⁺, 100),

226. HRMS (EI): m/z calcd for C₂₈H₂₆N₄O₂([M+H]⁺): 451.2134;

found: 451.2127.

4.34.13. Dimethyl-(2-{4-[5-(3-methylsulfanyl-

benzo[b]thiophen-6-yl)-4-pyridin-4-yl-1H-imidazol-2-yl]-

phenoxy}-ethyl)-amine (1l)

4.34.18. 6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-pyridin-

4-yl-3H-imidazol-4-yl}-naphthalen-1-ol (1q)

Compounds 38 (69 mg, 0.23 mmol) and 9 (73 mg, 0.19 mmol)

were coupled according to the general procedure to give the

Compound 9 (49 mg, 0.11 mmol) was coupled with compound

52 (37 mg, 0.14 mmol) according to the general procedure to give

1302

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

the desired compound. Yield: 34 mg (68%). Part of this (28 mg) was

converted to the triple TFA salt by dissolving in MeOH (1 mL), add-

ing triﬂuoroacetic acid (0.1 mL) and evaporating to dryness. Yield:

48 mg (86%). ¹H NMR (CD₃OD), d: 2.92 (s, 6H, N(CH₃)₂), 3.56

(t, J = 4.8, 2H, CH₂), 4.39 (t, J = 4.8, 2H, CH₂), 6.86 (dd, J = 6.1, 2.0,

1H, ArH), 7.17 (d, J = 9.1, 1H, ArH), 7.27–7.35 (m, 2H, ArH), 7.46

(d, J = 8.6, 1H, ArH), 8.00–8.06 (m, 6H, ArH), 8.30 (d, J = 8.6, 1H,

ArH), 8.56 (d, J = 6.4, 2H, ArH). LC–MS: R_f= 2.36 min; m/z 451

([M+H]⁺, 10), 226 (100). HRMS (EI): m/z calcd for C₂₈H₂₆N₄O₂

([M+H]⁺): 451.2134; found: 451.2116.

4.34.24. 6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-pyridin-

4-yl-3H-imidazol-4-yl}-2H-isoquinolin-1-one (1w)

Compounds 70 (56 mg, 0.21 mmol) and 9 (44 mg; 0.14 mmol)

were coupled according to the general procedure to give the de-

sired compound (2 mg, 2%). ¹H NMR (CD₃OD), d: 3.00 (s, 6H,

N(CH₃)₂), 3.66 (t, J = 4.8, 2H, CH₂), 4.46 (t, J = 4.8, 2H, CH₂), 6.74

(d, J = 7.3, 1H, ArH), 7.22 (d, J = 8.2, 2H, ArH), 7.28 (d, J = 7.3, 1H,

ArH), 7.71 (d, J = 8.6, 1H, ArH), 7.96 (s, 1H, ArH), 8.04–8.17 (m,

4H, ArH), 8.45 (d, J = 8.6, 1H, ArH), 8.59 (br, 2H, ArH). LC–MS:

R_f= 2.14 min; m/z 452 ([M+H]⁺, 10), 226 (100). HRMS (EI): m/z

calcd for C₂₇H₂₅N₅O₂([M+H]⁺): 452.2086; found: 452.2068.

4.34.19. 6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-1-

methoxymethyl-5-pyridin-4-yl-1H-imidazol-4-yl}-naphthalen-

2-ol (54)

4.34.25. (6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-1-

methoxymethyl-5-pyridin-4-yl-1H-imidazol-4-yl}-isoquinolin-

1-yl)-bis-(4-methoxy-benzyl)-amine (74)

Compound 8 (50 mg; 0.12 mmol) and compound 73 (89 mg;

0.17 mmol) were coupled using the general procedure to give the

desired compound (7 mg; 8%). LC–MS: R_f= 1.46 min; m/z 735

([M+H]⁺, 10), 368 (100). HRMS (EI): m/z calcd for C₄₅H₄₆N₆O₄

([M+H]⁺): 735.3659; found: 735.3652.

{2-[4-(4-Bromo-1-methoxymethyl-5-pyridin-4-yl-1H-imidazol-

2-yl)- phenoxy]-ethyl}-dimethyl-amine (8)¹⁸(80 mg; 0.19 mmol)

was coupled to 6-hydroxynaphthalene-2-boronic acid 53 (43 mg;

0.23 mmol) using the general procedure to give the desired com-

pound (44 mg, 48%). ¹H NMR (CDCl₃), d: 2.42 (s, 6H, N(CH₃)₂),

2.84 (t, J = 5.6, 2H, CH₂), 3.32 (s, 3H, CH₃), 4.18 (t, J = 5.6, 2H,

CH₂), 4.98 (s, 2H, CH₂), 6.96–7.08 (br, 4H, ArH), 7.36–7.46 (m, 2H,

ArH), 7.47–7.53 (m, 2H, ArH), 7.57 (d, J = 9.5, 1H, ArH), 7.81

(d, J = 8.9, 2H, ArH), 7.97 (s, 1H, ArH), 8.67 (d, J = 5.9, 2H, ArH).

LC–MS: R_f= 2.57 min; m/z 495 ([M+H]⁺, 100), 248. HRMS (EI): m/z

calcd for C₃₀H₃₁N₄O₃([M+H]⁺): 495.2396; found: 495.2392.

4.34.26. (2-{4-[4-(6-Fluoro-naphthalen-2-yl)-1-

methoxymethyl-5-pyridin-4-yl-1H-imidazol-2-yl]-phenoxy}-

ethyl)-dimethyl-amine (77)

Compounds 8 (50 mg; 0.12 mmol) and 76 (49 mg, 0.18 mmol)

were coupled using the general procedure to give the desired

product (50 mg; 71%). ¹H NMR (CDCl₃), d: 2.05 (s, 6H,

N(CH₃)₂), 2.78 (t, J = 5.7, 2H, CH₂), 4.07–4.19 (m, 5H, CH₃+ CH₂),

4.98 (s, 2H, CH₂), 7.07 (d, J = 9.1, 2H, ArH), 7.21 (td, J = 8.7, 2.5,

1H, ArH), 7.39 (dd, J = 9.8, 2.5, 1H, ArH), 7.48 (d, J = 5.9, 2H,

ArH), 7.54 (d, J = 9.5, 1H, ArH), 7.62–7.67 (m, 1H, ArH), 7.73

(dd, J = 8.9, 5.7, 1H, ArH), 7.82 (d, J = 8.6, 2H, ArH), 8.10 (s, 1H,

ArH), 8.69 (d, J = 6.4, 2H, ArH). LC–MS: R_f= 1.00 min; m/z 497

([M+H]⁺, 10), 249 (100).

4.34.20. 2-Chloro-6-{2-[4-(2-dimethylamino-ethoxy)-phenyl]-

5-pyridin-4-yl-3H-imidazol-4-yl}-naphthalen-1-ol (1s)

Compounds 57 (29 mg, 95 lmol) and 9 (27 mg, 95 lmol) were

coupled according to the general procedure to give the desired

compound (1 mg, 3%). ¹H NMR (CD₃OD), d: 3.02 (s, 6H, N(CH₃)₂),

3.66 (t, J = 4.8, 2H, CH₂), 4.46 (t, J = 4.8, 2H, CH₂), 7.22 (d, J = 9.1,

2H, ArH), 7.43–7.52 (m, 2H, ArH), 7.65 (d, J = 8.6, 1H, ArH), 8.07–

8.13 (m, 5H, ArH), 8.43 (d, J = 8.6, 1H, ArH), 8.56 (d, J = 6.8, 2H,

ArH). LC–MS: R_f= 2.54 min; m/z 485 ([M+H]⁺, 10), 243 (100).

4.34.27. 6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-pyridin-

4-yl-3H-imidazol-4-yl}-naphthalene-2-carboxylic acid (1z)

Compound 9 (50 mg; 0.12 mmol) was coupled to 6-(4,4,5,5-

tetramethyl-[1,3,2]dioxaborolan-2-yl)-naphthalen-2-carboxylic

acid, 79 (69 mg; 0.23 mmol) according to the general procedure

to give the desired compound (2 mg, 1%). ¹H NMR (CD₃OD), d:

3.02 (s, 6H, N(CH₃)₂), 3.65 (t, J = 4.8, 2H, CH₂), 4.46 (t, J = 4.8,

2H, CH₂), 7.22 (d, J = 8.6, 2H, ArH), 7.75 (d, J = 8.6, 1H, ArH),

8.04 (d, J = 8.6, 1H, ArH), 8.07–8.18 (m, 5H, ArH), 8.21

(d, J = 8.2, 1H, ArH), 8.26 (s, 1H, ArH), 8.58 (d, J = 6.8, 2H, ArH),

8.72 (s, 1H, ArH). LC–MS: R_f= 2.36 min; m/z 479 ([M+H]⁺, 100),

240. HRMS (EI): m/z calcd for C₂₉H₂₇N₄O₃([M+H]⁺): 479.2083;

found: 479.2076.

4.34.21. (2-{4-[4-(5-Diﬂuoromethoxy-6-ﬂuoro-naphthalen-2-

yl)-1-methoxymethyl-5-pyridin-4-yl-1H-imidazol-2-yl]-

phenoxy}-ethyl)-dimethyl-amine (61)

Compounds 8 (54 mg; 0.13 mmol) and 60 (55 mg; 0.16 mmol)

were coupled using the general procedure to give the desired product

(23 mg; 26%). Compound 61 was used in the next step without further

puriﬁcation. LC–MS: R_f= 1.49 min; m/z 563 ([M+H]⁺, 10), 282 (100).

4.34.22. 7-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-1-

methoxymethyl-5-pyridin-4-yl-1H-imidazol-4-yl}-quinolin-2-

ol (65)

Compounds 64 (120 mg; 0.44 mmol) and 8 (127 mg; 0.29 mmol)

were coupled according to the general procedure to give the desired

compound (100 mg; 68%). ¹H NMR (CDCl₃), d: 2.38 (s, 6H, N(CH₃)₂),

2.79 (t, J = 5.7, 2H, CH₂), 3.29 (s, 3H, CH₃), 4.16 (t, J = 5.7, 2H, CH₂),

4.95 (s, 2H, CH₂), 6.63 (d, J = 9.5, 1H, ArH), 7.07 (d, J = 9.1, 2H, ArH),

7.19–7.29 (m, 1H, ArH), 7.40 (d, J = 8.2, 1H, ArH), 7.43–7.50 (m, 2H,

ArH), 7.54 (br, 1H, ArH), 7.71 (d, J = 9.5, 1H, ArH), 7.80 (d, J = 9.1,

2H, ArH), 8.57 (d, J = 6.4, 2H, ArH). LC–MS: R_f= 1.09 min; m/z 496

([M+H]⁺, 10), 249 (100). HRMS (EI): m/z calcd for C₂₉H₂₉N₅O₃

([M+H]⁺): 496.2349; found: 496.2358.

4.35. MOM-deprotection

The protected imidazole (ie: 10) (0.16 mmol) was dissolved in

1 mL 5 M HCl and the reaction heated at 60 °C for 1 h. The solvents

were removed in vacuo to yield the deprotected imidazole as its

HCl salt in quantitative yield.

4.35.1. 6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-pyridin-4-

yl-1H-imidazol-4-yl}-naphthalen-2-ol (1r)

4.34.23. 6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-1-

methoxymethyl-5-pyridin-4-yl-1H-imidazol-4-yl}-quinolin-2-

ol (68)

Compounds 67 (184 mg; 0.68 mmol) and 8 (50 mg; 0.17 mmol)

were coupled according to the general procedure to give the de-

sired compound as a yellow glass (12 mg; 16%). Compound 68

was used in next step without further puriﬁcation. LC–MS:

R_f= 0.99 min; m/z 496 ([M+H]⁺, 10), 248 (100).

Compound 54 (63 mg, 0.13 mmol) was deprotected according

to the general procedure to give the title compound (15 mg, 26%)

as its HCl salt. ¹H NMR (CD₃OD), d: 3.02 (s, 6H, N(CH₃)₂), 3.66

(t, J = 5.1, 2H, CH₂), 4.46 (t, J = 5.2, 2H, CH₂), 7.13–7.28 (m, 4H,

ArH), 7.50–7.58 (m, 1H, ArH), 7.84 (t, J = 9.1, 2H, ArH), 8.04–8.15

(m, 5H, ArH), 8.55 (d, J = 5.0, 2H, ArH). LC–MS: R_f= 2.37 min; m/z

451 ([M+H]⁺, 100), 226. HRMS (EI): m/z calcd for C₂₈H₂₇N₄O₂

([M+H]⁺): 451.2134; found: 451.2132.

D. Niculescu-Duvaz et al. / Bioorg. Med. Chem. 21 (2013) 1284–1304

1303

4.35.2. 6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-pyridin-4-

yl-3H-imidazol-4-yl}-2-ﬂuoro-naphthalen-1-ol (1t)

Compound 61 (23 mg, 0.04 mol) was dissolved in 48% aq

Disclosure statement

l

This work was carried out as part of a research collaboration be-

tween the Institute of Cancer Research, The Wellcome Trust, Glaxo-

SmithKline and Cancer Research UK. Pease note that all authors

who are, or have been, employed by The Institute of Cancer Re-

search are subject to a ‘Rewards to Inventors Scheme’ that may re-

ward contributors to a programme that is subsequently licensed.

HBr (1 mL) and AcOH (1.6 mL) and the solution was heated to

120 °C in a sealed tube overnight. The solution was allowed to

cool to rt, diluted with water (5 mL) and washed with EtOAc.

The acidic layer was concentrated in vacuo and the the residue

puriﬁed by preparative HPLC to yield the TFA salt as a yellow

glue. Yield: 4.6 mg, 14%. ¹H NMR (CD₃OD), d: 3.02 (s, 6H,

N(CH₃)₂), 3.66 (t, J = 4.8, 2H, CH₂), 4.46 (t, J = 4.8, 2H, CH₂),

7.22 (d, J = 9.1, 2H, ArH), 7.36–7.51 (m, 2H, ArH), 7.63 (d,

J = 9.1, 1H, ArH), 8.04–8.14 (m, 5H, ArH), 8.41 (d, J = 8.6, 1H,

ArH), 8.56 (d, J = 6.4, 2H, ArH). LC–MS: R_f= 2.37 min; m/z 469

([M+H]⁺, 10), 235 (100). HRMS (EI): m/z calcd for C₂₈H₂₆FN₄O₂

([M+H]⁺): 469.2034; found: 469.2033.

Acknowledgments

This work was supported by the Wellcome Trust (Ref: 080333/

Z/06/Z), Cancer Research UK (Grant numbers C309/A11566, C309/

A8274 and C107/A10433), the Isle of Man Anti-Cancer Association

and The Institute of Cancer Research. We acknowledge NHS fund-

ing to the NIHR Biomedical Research Centre. We thank Professors

Workman and Blagg for their support. We are grateful to Meirion

Richards and Dr. Amin Mirza for technical support.

4.35.3. 7-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-pyridin-4-

yl-1H-imidazol-4-yl}-quinolin-2-ol (1u)

Compound 65 (25 mg; 0.024 lmol) was deprotected using the

Supplementary data

general procedure to give the desired product as its HCl salt

(30 mg; quantitative). ¹H NMR (CD₃OD), d: 3.03 (s, 6H, N(CH₃)₂),

3.70 (t, J = 5.7, 2H, CH₂), 4.54 (t, J = 5.7, 2H, CH₂), 6.76 (d, J = 9.5,

1H, ArH), 7.39 (d, J = 8.2, 2H, ArH), 7.54 (d, J = 7.3, 1H, ArH), 7.69

(br, 1H, ArH), 7.93 (d, J = 7.3, 1H, ArH), 8.10 (d, J = 9.5, 1H, ArH),

8.18–8.30 (m, 4H, ArH), 8.89 (d, J = 4.5, 2H, ArH). LC–MS:

R_f= 2.09 min; m/z 452 ([M+H]⁺, 10), 226 (100). HRMS (EI): m/z

calcd for C₂₇H₂₅N₅O₂([M+H]⁺): 452.2086; found: 452.2083.

Supplementary data associated with this article can be found, in

the online version, at http://dx.doi.org/10.1016/j.bmc.2012.12.035.

These data include MOL ﬁles and InChiKeys of the most important

compounds described in this article.

References and notes

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4.35.4. 6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-pyridin-4-

yl-3H-imidazol-4-yl}-quinolin-2-ol (1v)

Compound 68 (12 mg; 50 lmol) was deprotected using the gen-

eral procedure to give the desired product as its HCl salt (5 mg;

46%). ¹H NMR (CD₃OD), d: 3.02 (s, 6H, N(CH₃)₂), 3.67 (t, J = 5.0,

2H, CH₂), 4.49 (t, J = 5.0, 2H, CH₂), 6.71 (d, J = 9.5, 1H, ArH), 7.27

(d, J = 8.6, 2H, ArH), 7.55 (d, J = 8.6, 1H, ArH), 7.78 (d, J = 8.2, 1H,

ArH), 7.99–8.06 (m, 2H, ArH), 8.10–8.18 (m, 4H, ArH), 8.62–8.71

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276. HRMS (EI): m/z calcd for C₂₇H₂₆N₅O₂([M+H]⁺): 452.2087;

found: 452.2082.

4.35.5. 6-{2-[4-(2-Dimethylamino-ethoxy)-phenyl]-5-pyridin-4-

yl-1H-imidazol-4-yl}-isoquinolin-1-ylamine (1x)

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120 °C for 18 h. The acid was removed in vacuo and the residue

dissolved in water and washed with EtOAc. Evaporation of the

water gave the desired compound as the TFA salt (3.5 mg;

81%). ¹H NMR (CD₃OD), d: 3.02 (s, 6H, N(CH₃)₂), 3.65 (t, J = 4.5,

2H, CH₂), 4.46 (t, J = 4.5, 2H, CH₂), 7.22 (d, J = 8.6, 2H, ArH),

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J = 7.7, 1H, ArH), 8.10 (d, J = 8.6, 4H, ArH), 8.20 (s, 1H, ArH),

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4.35.6. (2-{4-[5-(6-Fluoro-naphthalen-2-yl)-4-pyridin-4-yl-1H-

imidazol-2-yl]-phenoxy}-ethyl)-dimethyl-amine (1y)

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eral procedure to give the desired product (31 mg; 70%). ¹H

NMR (CD₃OD), d: 3.04 (s, 6H, N(CH₃)₂), 3.70 (t, J = 4.8, 2H,

CH₂), 4.55 (t, J = 4.8, 2H, CH₂), 7.41 (d, J = 8.6, 2H, ArH), 7.48

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C

₂₈H₂₅FN₄O ([M+H]⁺):

3.2090; found: 453.2079.

1304

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Article Doi

Potent BRAF kinase inhibitors based on 2,4,5-trisubstituted imidazole with naphthyl and benzothiophene 4-substituents

DOI: 10.1016/j.bmc.2012.12.035

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