Systematic structure-activity relationship (SAR) exploration of diarylmethane backbone and discovery of a highly potent novel uric acid transporter 1 (URAT1) inhibitor

molecules

Article

Systematic Structure-Activity Relationship (SAR)

Exploration of Diarylmethane Backbone and

Discovery of A Highly Potent Novel Uric Acid

Transporter 1 (URAT1) Inhibitor

Wenqing Cai ^1,2,†, Jingwei Wu ^2,†, Wei Liu ², Yafei Xie ², Yuqiang Liu ², Shuo Zhang ³,

Weiren Xu ², Lida Tang ², Jianwu Wang ^1,* and Guilong Zhao ^2,

*

ID

1

School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China;

caiwenqingsunny@163.com

2

3

Tianjin Key Laboratory of Molecular Design and Drug Discovery, Tianjin Institute of Pharmaceutical

Research, Tianjin 300193, China; wujw@tjipr.com (J.W.); liuw@tjipr.com (W.L.); xieyf@tjipr.com (Y.X.);

liuyq@tjipr.com (Y.L.); xuwr@tjipr.com (W.X.); tangld@tjipr.com (L.T.)

Shandong Key Laboratory for Special Silicon-Containing Materials, Advanced Materials Institute,

Shandong Academy of Sciences, Jinan 250014, China; e50687e@163.com

Correspondence: jwwang@sdu.edu.cn (J.W.); zhao_guilong@126.com (G.Z.); Tel.: +86-531-8836-2708 (J.W.);

+86-22-2300-6869 (G.Z.)

*

†

These authors contributed equally to this work.

Received: 18 January 2018; Accepted: 26 January 2018; Published: 27 January 2018

Abstract: In order to systematically explore and better understand the structure-activity relationship

(SAR) of a diarylmethane backbone in the design of potent uric acid transporter 1 (URAT1) inhibitors,

33 compounds (1a–1x and 1ha–1hi) were designed and synthesized, and their in vitro URAT1

inhibitory activities (IC₅₀) were determined. The three-round systematic SAR exploration led to the

discovery of a highly potent novel URAT1 inhibitor, 1h, which was 200- and 8-fold more potent

than parent lesinurad and benzbromarone, respectively (IC₅₀= 0.035

µM against human URAT1 for

1h vs. 7.18 M and 0.28 M for lesinurad and benzbromarone, respectively). Compound 1h is the

µ

most potent URAT1 inhibitor discovered in our laboratories so far and also comparable to the most

potent ones currently under development in clinical trials. The present study demonstrates that the

diarylmethane backbone represents a very promising molecular scaffold for the design of potent

URAT1 inhibitors.

Keywords: gout; hyperuricemia; URAT1 inhibitor; lesinurad; structure-activity relationship

(SAR); synthesis

1. Introduction

Gout is the most common inﬂammatory arthritis caused by the deposition of monosodium urate

(MSU) in articular and periarticular tissues and characterized by recurrent joint swelling, redness,

warmth and severe pain [

lead to permanent joint destruction, bone erosion and kidney impairment, dramatically affecting

patients’ quality of life and even threatening their lives [ ]. In addition, more and more evidence

has been accumulated to demonstrate that hyperuricemia is likely an independent risk factor for

hypertension, chronic kidney disease (CKD) and congestive heart failure (CHF) among others [ ].

First identiﬁed by Egyptians in 2640 BC, gout is among the earliest diseases recognized as a clinical

entity [ ]. The prevalence and incidence of hyperuricemia and gout have been rising worldwide [ ],

and gout and its comorbidities present signiﬁcant burdens on both the individual and community [ ].

1]. If left untreated or poorly managed, tophaceous gout will ultimately

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Hyperuricemia is the necessary condition of MSU formation and deposition, which is deﬁned as

elevated serum uric acid (sUA) levels above the saturation point of MSU in body ﬂuid at physiological

pH (7.4) and temperature, i.e., 6.8 mg/dL (404

µmol/L) [10]. Uric acid is a weak organic acid

(pKa = 5.75), and therefore greater than 98% is in the ionized form, i.e., urate anion, at physiological

pH (7.4); due to the presence of sodium ion at high concentrations in the extracellular compartment,

urate largely presents as MSU [11].

Uric acid is the end-product of purine metabolism in humans due to the loss of uricase during the

course of evolution; uricase is an enzyme capable of oxidizing highly insoluble uric acid to allantoin,

which is 5–10 times more water-soluble than uric acid and can, therefore, be much more readily

eliminated by the kidney [12]. Hyperuricemia is caused by over-production and/or under-excretion of

urate, and among the patients with hyperuricemia, greater than 90% of them are urate under-excretors,

whereas the remaining less than 10% are over-producers [13].

The treatment of gout can be divided into the anti-inﬂammatory treatment of acute gout attack

and management of chronic gout. The standard therapy for acute gout is traditionally directed

toward reducing inﬂammation with anti-inﬂammatory agents such as colchicine, nonsteroidal

anti-inﬂammatory drugs (NSAIDs), corticosteroids and interleukin-1

reduce gout ﬂares but are also associated with a variety of adverse effects [14

treatment of chronic gout is to reduce sUA <6 mg/dL (360 mol/L) and even <5 mg/dL (300

β

blockers, which can effectively

15]. The mainstay of

mol/L)

,

µ

for severe gout by urate-lowering therapy (ULT) with xanthine oxidase inhibitors (XOIs) such

as allopurinol, febuxostat and topiroxostat, uricosuric agents such as probenecid, sulﬁnpyrazone,

benzbromarone and lesinurad, and uricase such as pegloticase [15,16]. Reducing the sUA below the

saturation point of MSU in body ﬂuid can prevent the formation of new MSU crystals and lead to the

dissolution of existing crystals. XOIs are used as ﬁrst-line ULT, which are, nonetheless, associated with

many severe adverse effects and low response rate; uricosuric agents are usually used as second-line

therapy when patients are refractory to XOIs alone or contraindicated for them [13]. Uricases are only

indicated for patients with severe gout or high sUA burden, such as those with tophaceous deformities,

tumor lysis syndrome or Lesch-Nyhan syndrome [13].

The production of uric acid is balanced by its elimination, mainly in the urine. Approximately

one-third of urate is excreted via the gastrointestinal tract, while the remaining two-thirds via the

kidney [12]. In humans, sUA levels are controlled by a complex system of transporters expressed in the

renal proximal tubule. Thus, uric acid is freely ﬁltered at the glomerulus, and greater than 90% of the

urate ﬁltered in the kidney is reabsorbed back into the bloodstream with the remaining less than 10%

being excreted in urine; this reabsorption process is mainly mediated by uric acid transporter 1 (URAT1,

SLC22A12), also known as urate transporter 1 or urate-anion exchanger. URAT1, ﬁrst identiﬁed in

2002, is a 12-transmembrane protein and prominently expressed on the apical side of epithelial cells

of proximal tubules in the renal cortex [12,17]. In light of the fact that more than 90% of the patients

with hyperuricemia are urate under-excretors and URAT1 is responsible for most of the uric acid

reabsorption (about 90%), URAT1 inhibitors were believed to be a very efﬁcacious and promising class

of uricosuric agents for the treatment of hyperuricemia and gout [18,19].

Three uricosuric agents, probenecid, sulﬁnpyrazone and benzbromarone, were used in the clinic

for a long time before the identiﬁcation of URAT1 in 2002, and their uricosuric effect was found

to arise from the URAT1 inhibitory activity (Figure 1) [17]. However, these agents suffer from a

variety of adverse effects or drawbacks. Probenecid is associated with low efﬁcacy, short half-life and

signiﬁcant drug-drug interaction (DDI) resulting from its dual inhibition against URAT1 and other

organic anion transporters (OATs), such as OAT1 and OAT3 [12,20]. Sulﬁnpyrazone is also a very

weak URAT1 inhibitor with a short half-life, and associated with severe gastrointestinal toxicity [21].

Benzbromarone is a potent URAT1 inhibitor, but notorious for severe hepatotoxicity, which resulted

in its withdrawal from Europe in 2003 and non-approval in the US [22]. Lesinurad is a novel URAT1

inhibitor developed by Ardea Biosciences, now a subsidiary of AstraZeneca, and was approved by the

U.S. Food and Drug Administration (FDA) in 2015 and by the European Medicines Agency (EMA) in

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2016 for the treatment of hyperuricemia associated with gout in combination with an XOI. Lesinurad

is the ﬁrst URAT1 inhibitor approved after the identiﬁcation of URAT1 in 2002; however, lesinurad

suffers from low efﬁcacy and a narrow therapeutic window [23]. Recently, considerable attention

has been paid to the burden of gout on the individual and community as well as the discovery of

URAT1 inhibitors on identiﬁcation of URAT1 as a druggable therapeutic target, with lesinurad being

approved and a number of others under development in clinical trials (Figure 1) [24–29]. In the effort

to discover potent URAT1 inhibitors based on the structure of lesinurad in our laboratories, earlier

studies successfully delivered a number of highly potent URAT1 inhibitors, and the IC₅₀values of

some of them are even lower by almost two orders of magnitude than lesinurad (Figure 2) [30–34].

These highly potent URAT1 inhibitors share a common structural feature, i.e., a carboxylic group

(in blue) connected to a ﬂexible naphthyltriazolylmethane backbone (in red) by a linker. Encouraged

by the earlier results, we moved forward to expand this speciﬁc naphthyltriazolylmethane backbone

to a general diarylmethane backbone and carry out a systematic structure-activity relationship (SAR)

study on the general backbone as well as the substituents on the α-position of the carboxylic acid

group, with an expectation to better understand the SAR of this unique ﬂexible structure and discover

highly potent URAT1 inhibitors as promising candidate drugs (Schemes 1–5). The SAR study delivered

a highly potent URAT1 inhibitor 1h with a new backbone, i.e., thiophenyltrizolylmethane, and an IC₅₀

of 0.035 µM, which is the most potent URAT1 inhibitor discovered in our laboratories so far and also

comparable to the most potent ones currently under development in clinical trials [12].

Figure 1. Structures of approved URAT1 inhibitors and selected URAT1 inhibitors under development

in clinical trials.

Figure 2. Design of URAT1 inhibitors in present study and discovery of 1h.

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2. Results and Discussion

2.1. Chemistry

The synthetic route to target compounds 1a

–

1n is shown in Scheme 1 . 1-Adamantanecarboxylic

ac_◦id 11 was treated with thionyl chloride in the presence of DMF as catalyst in dried CH₂Cl₂at

0 C to reﬂux temperature to afford the corresponding acyl chloride 12, which was subsequently

treated with aqueous ammonia in THF at 0 ^◦C to roo_◦m temperature to smoothly produce amide 13

.

Reduction of amide 13 with LiAlH₄in dried THF at 0 C to reﬂux temperature yielded corresponding

methylamine 2d. 5-Bromobenzo[b]furan 9k and 2-bromonaphthalene 9m reacted with CuCN in DMF

◦

at high temperatures (reﬂux for 9k and 130 C for 9m) in N₂atmosphere to furnish 10k and 10m

,

◦

respectively, which were then reduced with LiAlH₄in dried THF at 0 C to reﬂux temperature to

afford corresponding methylamines 2k and 2m, respectively. 1-Methylnaphthalene 14 was brominated

◦

with N-bromosuccinimide (NBS) in acetonitrile at 30–40 C to afford 1-bromo-4-methylnaphthalene 15

,

.

◦

which was treated with CuCN in DMF in N₂atmosphere at 130 C to give rise to cyanonaphthalene 16

Methylnaphthalene 16 was smoothly converted to bromomethylnaphthalene 17 by treatment with NBS

in the presence of benzoyl peroxide (BPO) in CCl₄at reﬂux in N₂atmosphere, which was subsequently

◦

treated with 3 eq of KSCN in DMF at 140 C in N₂atmosphere to afford isothiocyanate 3l. It is

worth noting that the high reaction temperature is critically important for the selective formation of

isothiocyanate 3l over its potential isomer thiocyanate [35]. Methylamines 2c

–2k and 2m–2n were

treated with thiophosgene in the presence of diisopropylethylamine (DIPEA) as acid scavenger in

dried CH₂Cl₂at 0 ^◦C to room temperature to yield corresponding isothiocyanates 3c

respectively. Isothiocyanates 3a

furnish the adducts 4a 4n, which were in turn directly treated with aqueous K₂CO₃in THF (4a

or DMF (4c

4n) at 50 ^◦C to effect the cyclization to give the triazole thiones 5a

puriﬁcation and characterization. Selective S-alkylation of thiones 5a

in the presence of K₂CO₃in acetone (5a 5b) or DMF (5c 5n) at room temperature gave esters 6a

Treatment of 6a 6c and 6e 6n with NBS in acetonitrile at room temperature smoothly effected selective

bromination at 5-position of the triazole ring to successfully yield 7a 7c and 7e 7n, respectively;

–

3k and 3m

–

3n

,

–3n reacted ﬁrst with formic hydrazide in THF at room temperature to

–

4b)

–

5n without further

5n with methyl bromoacetate

6n.

–

however, after considerable experimentation, the bromination of 6d to 7d could only be brought

about with a more powerful brominating reagent 1,3-dibromo-5,5-dimethylhydantoin (DBDMH) in

CH₂Cl₂at room temperature presumably due to the steric hindrance posed by the bulky adamantane

ring [36]. Alkaline hydrolysis of esters 7a

afforded corresponding carboxylic acids 8a

–

7n with aqueous LiOH in MeOH at room temperature

8n, which were converted to sodium salts thereof for the

sake of improving the aqueous solubility to facilitate the operation in in vitro assay.

The synthetic route to target compounds 1ha 1hi is summarized in Scheme 2. Standard

Vilsmeier formylation at the -position of thiophenes 9ha

9hc with POCl₃/DMF at 100 ^◦C smoothly

produced corresponding aldehydes 10ha 10hc 37]; however, under the same reaction condition,

–

α

–

[

3-methylthiophene 9hd gave an inseparable mixture of 3-methylthiophene-2-carbaldehyde 10hd

and 4-methylthiophene-2-carbaldehyde 10he in a ratio of 85/15 as indicated by ¹H-NMR because

of the presence of two

α-positions in 9hd [38]. The minor isomer 10he was removed from 10hd

by recrystallization of the mixture of their corresponding oximes 11hd and 11he in the next step.

Compounds 9he

,

9hh and 9hi were ﬁrst treated with n-BuLi in dried THF at

−

78 ^◦C (9he and 9hh

)

◦

or at

−

78 C to room temperature (9hi) to afford the corresponding aryl lithiums, which were in

turn trapped with dried DMF at

−

78 ^◦C to room temperature to produce aldehydes 10he

, 10hh and

10hi, respectively. It is worth noting that, as with in the case of the conversion of 9hd to 10hd and

10he as described above, 9he (identical to 9hd actually) also gave an inseparable mixture of 10hd and

10he in a ratio of 19/81 under the second formylation condition [38], and the minor isomer 10hd was

also removed from 10he by recrystallization of the mixture of corresponding oximes 11hd and 11he

in the next step. Standard Suzuki coupling of 18 and PhB(OH)₂in the presence of Pd(PPh₃)₄and

K₂CO₃in dioxane/H₂O (9/1 by v/v) in N₂atmosphere at reﬂux smoothly afforded 10hg. Aldehydes

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10ha

–

10hi were converted to corresponding oximes 11ha

–

11hi each as a Z/E mixture by treatment with

hydroxylamine hydrochloride in the presence of K₂CO₃in 90% ethanol at 0 ^◦C to room temperature.

Oximes 11ha–11hi were reduced to corresponding methylamines 2ha–2hi with LiAlH₄in dried THF

at 0 ^◦C to reﬂux temperature. Following the same procedure for the synthesis of 1c–1n from 2c–2n in

Scheme 1 , 2ha

in the bromination of 6ha

adamantane ring, the bromination of 6hi also needed the powerful brominating reagent DBDMH

because of the presence of bulky dibenzothiophene ring; (2) unlike bromination of 6a 6c and 6e 6n

6hd

–2hi were converted to targets compounds 1ha

–1hi. However, there are some exceptions

–

6hi that should be noted: (1) just as with the bromination of 6d with a bulky

–

with NBS that proceeded at room temperature (Scheme 1), the bromination of compounds 6ha

–

◦

and 6hf

–

6hg with NBS required to be carried out at 0 C to suppress the potential bromination of

the thiophene ring because thiophene ring is an aromatic ring more electron-rich than most of the

counterparts in Scheme 1; (3) treatment of 6he and 6hh with 1 eq of NBS gave intermediates 7⁰he

and 7⁰hh, respectively, even at 0 ^◦C, where the bromine atom was introduced to the thiophene ring

instead of the desired triazole ring because the unoccupied

and -position in benzothiophene ring are more electron-rich and therefore more nucleophilic than the

5-position in triazole ring. Further treatment of 7⁰he and 7⁰hh with 1 eq of NBS produced 7he and 7hh

α-position in 4-methyl-2-thiophene ring

β

,

respectively, where the newly introduced bromine atom was at the desired 5-position of triazole ring.

The exact position of the bromine atom in 7⁰he was unambiguously elucidated by Nuclear Overhauser

Effect (NOE) as shown in Scheme 2.

The synthetic route to 1o–1s is depicted in Scheme 3. Isothiocyanate 3l ﬁrst reacted with

2-aminoacetaldehyde dimethyl acetal in THF at room temperature to give an adduct 4o, which in

turn underwent cyclization to afford imidazole thione 5o by treatment in reﬂuxing 25%H₂SO₄/AcOH

(8/2 by v/v) [39]. Selective S-alkylation of imidazole thione 5o with methyl bromoacetate, ethyl

2-bromo-2-methylpropionate and ethyl 1-bromocyclobutanecarboxylate in the presence of K₂CO₃in

DMF at room temperature afforded 6q

triazole thione 5l with ethyl 2-bromo-2-methylpropionate and ethyl 1-bromocyclobutanecarboxylate

in the presence of K₂CO₃at elevated temperatures (60 ^◦C for 6o and 80 ^◦C for 6p) yielded 6o and 6p

respectively. Compounds 6o 6s were converted to target compounds 1o 1s following the procedure

used for the synthesis of 1a 1n from 6a 6n as shown in Scheme 1. Noteworthy is that the brominations

of 6o and 6p were carried out at higher temperatures instead of room temperature, i.e., 60 ^◦C for 6o

and 45 ^◦C for 6p. In the bromination of imidazole ring in 6q

6s, there are two potential positions to

, 6r and 6s, respectively. Likewise, selective S-alkylation of

,

–

be brominated, and the exact position at which the bromine atom was introduced was unequivocally

determined by NOE as depicted in Scheme 3, which is also consistent with the reported results in

similar situation [40]. The exact position of the bromine atom attached to the imidazole ring in 7q–7s

was identical to that in their triazole counterparts 1a–1n and 1ha–1hi, which is critically important in

SAR study when to compare the biological activity of a pair of compounds with only the central rings

being different while other positions including the substituents being completely identical.

The synthetic route to target compounds 1t–1v is illustrated in Scheme 4.

4-Cyano-1-naphthaldehyde 19 was prepared from (4-cyano-1-naphthyl)methyl bromide 17 by

standard Sommelet reaction [41]. Thus, 17 reacted ﬁrst with hexamethylenetetramine in reﬂuxing 50%

aqueous acetic acid, and the quaternary ammonium intermediate thus formed was further hydrolyzed

with hydrochloric acid to give rise to 19. Treatment of 3-bromo-4-chloropyridine 20 with n-BuLi in

dried THF at

−

78 ^◦C furnished 21, a reactive aryl lithium intermediate resulting from the selective

Br-Li exchange [42], which was in turn trapped with aldehyde 19 to give 22. Treatment of benzylic

alcohol 22 with thionyl chloride in dried CH₂Cl₂at 0 ^◦C to room temperature gave benzylic chloride

23, which was subsequently reduced with zinc powder in acetic acid at room temperature to smoothly

produce 24 with a desired naphthylpyridinylmethane backbone [43]. Initial attempts to directly reduce

benzylic alcohol 22 to 24 with Et₃SiH/BF₃Et₂O [44], NaBH₄/AlCl₃[45] or 57%HI/AcOH [46] were

·

unsuccessful because no reaction occurred for the ﬁrst reagent, a side reaction of AlCl₃-mediated

dechlorination predominated for the second one and the reaction proceeded considerably slowly for

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the third one. Treatment of chloropyridine 24 with Na₂S

furnished pyridine thiol 5p. Selective S-alkylation of thiol 5p with methyl bromoacetate, ethyl

·

9H₂O in DMF at 110 ^◦C in N₂atmosphere

2-bromo-2-methylpropionate and ethyl 1-bromocyclobutanecarboxylate in the presence of K₂CO₃

in DMF at room temperature gave 6t

,

6u and 6v, respectively. Alkaline hydrolysis of 6t

–

6v with

aqueous LiOH in methanol at room temperature afforded corresponding acids 8t–8v, which were then

converted to sodium salts thereof 1t–1v as described above.

The synthetic route to target compounds 1w–1x is presented in Scheme 5. Imidazole

thione 5q was prepared from isothiocyanate 3h following the procedure described above for the

synthesis of 5o from 3l. Treatment of thione 5q with ethyl 2-bromo-2-methylpropionate and ethyl

1-bromocyclobutanecarboxylate in the presence of K₂CO₃in DMF at elevated temperatures (60 ^◦C

for 6w and 40 ^◦C for 6x) produced 6w and 6x, respectively. Compounds 6w

target compounds 1w 1x following the procedure used for the synthesis of 1q

Scheme 3 except that the bromination of 6w

6x with NBS was carried out at 0 ^◦C in order to suppress

the potential bromination of thiophene ring.

–

6x were converted to

–

1s from 6q 6s shown in

–

Scheme 1. Synthetic route to 1a

–

1n. Reagents and conditions: (i) _◦SOCl₂, DMF (cat.), dried CH₂Cl₂,

◦

0 C-reﬂux; (ii) NH₃

·

H₂O, THF, 0 C-rt; (iii) LiAlH₄, dried THF, 0 C-reﬂux; (iv) CuCN, DMF, 130 C

◦

(15 and 9m) or reﬂux (9k), N₂; (v) for 14: NBS, MeCN, 30–40 C; for 6a–6c and 6e–6n: NBS, MeCN, rt;

◦

for 6d: DBDMH, CH₂Cl₂, rt; (vi) NBS, BPO, CCl₄, reﬂux, N₂; (vii) KSCN, DMF, 140 C, N₂; (viii) CSCl₂,

◦

DIPEA, dried CH₂Cl₂, 0 C-rt; (ix) HCONHNH₂, THF, rt ; (x) aq K₂CO₃, THF (4a

–

4b) or DMF (4c–4n),

◦

50 C; (xi) BrCH₂CO₂Me, K₂CO₃, acetone (5a

–5b) or DMF (5c

–5n), rt; (xii) aq LiOH, MeOH, rt; (xiii) aq

NaOH, MeOH, rt.

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Scheme 2. Synthetic route to 1ha

100 ^◦C; for 9he 9hh and 9hi: n-BuLi, dried THF, –78 ^◦C (9he and 9hh) or

DMF,

78 ^◦C-rt; (ii) NH₂OH HCl, K₂CO₃, 90%EtOH, 0 ^◦C-rt; (iii) PhB(OH)₂, Pd(PPh₃)₄, K₂CO₃,

–

1hi. Reagents and conditions: (i) for 9ha

–

9hd: POCl₃, dried DMF,

,

−

78 ^◦C-rt (9hi), then dried

−

·

dioxane/H₂O (9/1 by v/v), N₂, reﬂux; (iv) LiAlH₄, dried THF, 0 ^◦C-_◦reﬂux; (v) CSCl₂, DIPEA, dried

◦

CH₂Cl₂, 0 C-rt; (vi) HCONHNH₂, THF, rt ; (vii) aq K₂CO₃, DMF, 50 C; (viii) BrCH₂CO₂Me, K₂CO₃,

DMF, rt; (ix) for 6ha

and 6hh: NBS, MeCN, 0 C; (xi) NBS , MeCN, rt; (xii) aq LiOH, MeOH, rt; (xiii) aq NaOH, MeOH, rt.

–

6hd_◦and 6hf

–

6hg: NBS , MeCN, 0 ^◦C; for 6hi: DBDMH, CH₂Cl₂, rt; (x) for 6he

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Scheme 3. Synthetic route to 1o

rt; (ii) 25%H₂SO₄/AcOH (8/2 by v/v), reﬂux; (iii) for 6q

for 6o and 6r

–

1s

.

Reagents and conditions: (i) NH₂CH₂CH(OMe)₂, THF,

BrCH₂CO₂Me, K₂CO₃, DMF, rt;

(CH₃)₂CBrCO₂Et, K₂CO₃, DMF, 60 ^◦C (6o) or rt (6r); for 6p and 6s, ethyl

:

1-b_◦romocyclobutanecarboxylate, K₂CO₃, DMF, 80 ^◦C (6p) or rt (6s); (iv) NBS, MeCN, 60 ^◦C (6o),

45 C (6p) or rt (6q–6s) ; (v) aq LiOH, MeOH, rt; (vi) aq NaOH, MeOH, rt.

Scheme 4. Synthetic route to 1t

–

1v. Reagents and conditions: (i) (a) hexamethylenetetramine, 50%AcOH,

◦

reﬂux; (b) con. HCl, 50%AcOH, reﬂux; (ii) n-BuLi, dried THF,

−

78 C, N₂, then 19

,

−

78 C-rt; (iii)

◦

SOCl₂, dried CH₂Cl₂, 0 C-rt; (iv) Zn, AcOH, rt; (v) Na₂S·9H₂O, DMF, 110 C, N₂; (vi) BrCH₂CO₂Me

(

6t), (CH₃)₂CBrCO₂Et (6u) or ethyl 1-bromocyclobutanecarboxylate (6v), K₂CO₃, DMF, rt; (vii) aq

LiOH, MeOH, rt; (viii) aq NaOH, MeOH, rt.

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Scheme 5. Synthetic route to 1w

(ii) 25%H₂SO₄/AcOH (8/2 by v/v), reﬂux; (iii) for 6w: (CH₃)₂CBrCO₂Et, K₂CO₃, DMF, 60 C; for 6x

ethyl 1-bromocyclobutanecarboxylate, K₂CO₃, DMF, 40 C; (iv) NBS, MeCN, 0 C; (v) aq LiOH, MeOH,

rt; (vi) aq NaOH, MeOH, rt.

–1x. Reagents and conditions: (i) NH₂CH₂CH(OMe)₂, THF, rt;

◦

:

◦

2.2. In Vitro URAT1 Inhibitory Activity

The results of in vitro inhibitory assay of 33 synthesized compounds, i.e., 1a–1x and 1ha–1hi,

as well as lesinurad as positive control against human URAT1 (Supplementary Material) are

summarized in Table 1.

Table 1. Results of in vitro inhibitory assay of 1a–1x and 1ha–1hi against human URAT1 (IC₅₀).

Compd.

R

X

R¹

R²

IC₅₀(µM) ^a

7.18 ± 1.13 ^b

0.28 ± 0.07 ^c

18.42 ± 3.36

4.83 ± 1.02

lesinurad

benzbromarone

-

1a

1b

Me

Et

1c

-

4.60 ± 0.88

1d

-

5.11 ± 0.79

1e

1f

-

2.98 ± 0.60

14.19 ± 4.71

4.54 ± 0.69

0.035 ± 0.01

1.16 ± 0.34

1g

1h

1i

1j ^d

-

1.15 ± 0.25

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Table 1. Cont.

Compd.

1k

R

X

R¹

R²

IC₅₀(µM) ^a

-

2.61 ± 0.40

3.80 ± 0.78

1l

-

1m

1n

-

4.66 ± 1.04

1.36 ± 0.24

1ha

1hb

1hc

-

11.23 ± 2.36

> 50

7.98 ± 2.14

1hd

1he

-

3.04 ± 0.84

6.10 ± 1.17

1hf

-

> 50

1hg

1hh

-

31.68 ± 9.34

0.12 ± 0.03

1hi

-

18.47 ± 5.41

1o

1p

1q

1r

1s

1t

1u

1v

1w

1x

-

N

C

-

Me

1.96 ± 0.34

0.59 ± 0.17

5.55 ± 0.98

0.21 ± 0.07

0.48 ± 0.11

8.83 ± 1.02

1.39 ± 0.42

1.15 ± 0.20

17.36 ± 3.98

0.32 ± 0.07

-(CH₂)₃-

H

Me

H

Me

H

Me

H

Me

-(CH₂)₃-

Me

a

All the experiments were performed in triplicate, and the IC₅₀values were expressed as mean

value for lesinurad: IC₅₀= 7.3 µM against human URAT1 [23]. Reported value for benzbromarone: IC₅₀= 0.29 µM

against human URAT1 [47]. For 1j, the substituent R should be RCH₂as indicated in Scheme 1.

±

SD. ^bReported

c

d

As shown in Figure 2, the diarylmethane backbone consists of two aromatic rings, i.e., the distal

and central aromatic rings, corresponding to the modiﬁcations of the naphthalene and triazole

rings in the original naphthyltriazolylmethane backbone, respectively. The SAR exploration of the

Molecules 2018, 23, 252

11 of 38

diarylmethane backbone in present study started with the distal aromatic ring. This round of SAR

study was divided into two phases: the ﬁrst phase was mainly focused on the discovery of an optimal

framework of the distal ring (1a

around the optimal framework identiﬁed in the ﬁrst phase to further ﬁnd its most preferred substituent

1ha 1hi). Thus, as shown from the results of 1a 1n, the optimal framework for the distal ring is

2-thiophene ring with 1h being the most potent URAT1 inhibitor among 1a 1n (IC₅₀= 0.035 M).

It is also obvious that, with only a few exceptions (such as 1f and 1a), most compounds in 1a 1n are

more potent than lesinurad, but there is a trend that compounds with two aromatic rings in the R

substituent (1i 1n) are generally more potent than those with only one aromatic or lower (cyclo)alkyl

groups (1a 1h). Noteworthy is that although this trend didn’t deliver the most potent compound (1h

–1n), and the second one was the ﬁne-tuning of the substituents

(

–

µ

–

)

in this phase, it still warrants further study in the future. With 2-thiophene ring being identiﬁed as the

optimal framework for the distal aromatic ring, we progressed to the second phase, i.e., ﬁne-tuning

of the substituents around 2-thiophene ring. Thus, among 1ha–1hi with a 2-thiophene ring and its

close analogues, no compound was found to be more potent than 1h, indicating that the framework of

2-thiophene cannot tolerate any substituent. It is interesting that 3-thiophene ring, a close analogue of

2-thiophene ring, led to the complete loss of URAT1 inhibitory activity (1hf). Compound 1hh with a

3-bromobenzo[b]thiophene ring exhibited highly potent URAT1 inhibitory activity (IC₅₀= 0.12 µM),

which, however, is still less potent than 1h.

In order to accelerate the whole process of SAR exploration, we carried out the SAR exploration

of the central aromatic ring as well as the substituents on the -position of the carboxylic acid group

at the same time we performed the ﬁrst round of SAR study. In the second round, we kept the distal

aromatic ring as 4-cyano-1-naphthalene ring and designed 9 compounds (1o 1v). Thus, it is clear

that for all the three central aromatic rings, i.e., 1,2,4-triazole, imidazole and pyridine, the activity

was uniformly enhanced dramatically when the size of -substituents of the carboxylic acid group

increased (1p 1o 1l 1r 1s 1q 1v 1u 1t), indicating that the gem-dimethyl and cyclobutane

are optimal substituents at the -position of the carboxylic acid group. Among the three central rings,

α

–

α

>

;

>

;

>

α

the imidazole ring seemed the optimal one (1r > 1u > 1o; 1s > 1p > 1v).

With in hand the optimal distal ring being 2-thiophene from the ﬁrst-round SAR study and the

optimal central ring and the α-substituent of the carboxylic acid group being imidazole ring and

gem-dimethyl/cyclobutane, respectively, from the second-round, we advanced to the third round by

merging the results from the ﬁrst two rounds of SAR study and designed compounds 1w and 1x to see

if there is an additive effect. It turned out that the URAT1 inhibitory activity of 1w was weak but the

1x was highly potent, which was, however, still less potent than 1h.

In summary, 1h displayed an IC₅₀of 0.035 µM, which is 200- and 8-fold more potent than

the parent lesinurad and benzbromarone, respectively, making it the most potent URAT1 inhibitor

discovered in our laboratories so far and also comparable to the most potent ones currently under

development in clinical trials [18]. The present study strongly suggested that diarylmethane backbone

is a considerably promising molecular scaffold for the design of potent URAT1 inhibitors.

3. Experimental Section

3.1. General

Melting points were measured with an RY-2 microscopic melting point apparatus (Tianjin

Tianguang Optical Instrument Ltd., Tianjin, China) and are uncorrected. ¹H-NMR and ¹³C-NMR

spectra were recorded on a Bruker AV400 NMR spectrometer (Bruker BioSpin AG, Faellanden,

Switzerland) using DMSO-d₆, CDCl₃and MeOH-d₄as solvent and known chemical shifts of residual

1

proton signals of deuterated solvents (for H-NMR) or carbon signals of deuterated solvents (for

¹³C-NMR) as internal standard. High-resolution mass spectra (HRMS) were recorded with an

Agilent Q-TOF 6510 mass spectrometer (Agilent Technologies, Santa Clara, CA, USA) using the

direct injection method and electrospray ionization (ESI) technique in negative mode (ESI–). HPLC

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purities are determined on a reverse-phase C₁₈column (Waters Atlantis T3, 5

µ

m, 4.6

×

150 mm;

column temperature, 35 ^◦C) at 225 nm using an Agilent 1260 VWD HPLC system with ﬂow rate of

1.0 mL/min. Mobile phase A was MeCN/MeOH (90/10 by v/v), and mobile phase B was 10 mM

aqueous (NH₄)₂HPO₄(adjusted to pH of 4.3

A/B (25%/75%) at 0 min to A/B (40%/60%) at 30 min, A/B (50%/50%) at 45 min, A/B (70%/30%) at

60 min, A/B (70%/30%) at 70 min, A/B (25%/75%) at 71 min, and ﬁnally A/B (25%/75%) at 75 min.

±

0.03 with H₃PO₄). The gradient system started from

Starting materials 11, 9k, 9m, 14, 2c, 2e–2j, 2n, 3a–3b, 9ha–9hd, 9hh–9hi, 18, 10hf and 20 were

commercially available. All the dried solvents were prepared by standard methods.

3.2. Chemistry

3.2.1. General Procedure for the Synthesis of Substituted Methylamines 2d, 2k and 2m

To a stirred mixture of 1-adamantanecarboxylic acid (11, 36.05 g, 200 mmol) and DMF (5 drops)

in CH₂Cl₂(360 mL) cooled in an ice-water bath was added thionyl chloride (26.17 g, 220 mmol) in

one portion. The resulting mixture was reﬂuxed until the evolution of HCl gas ceased (typically

within 2 h). The solvent and excess thionyl chloride were then removed on a rotary evaporator, and

the crude acid chloride 12 was dissolved in THF (100 mL). The resulting solution was then slowly

added dropwise to stirred concentrated aqueous ammonia (400 mL) cooled in an ice-water bath. After

addition, the resulting white slurry was stirred at room temperature for another 2 h, and the white

precipitates were collected via vacuum ﬁltration, washed with cold n-hexane and dried in vacuo to

afford 1-ada_◦mantanecarboxamide (13). White solid; 34.06 g (95%); m.p. 177–179 ^◦C (literature value,

185.5–191.7 C [48]). ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 6.89 (brs, 1H), 6.62 (brs, 1H), 1.93 (s, 3H),

1.73–1.74 (m, 6H), 1.60–1.68 (m, 6H).

A mixture of 1-methylnaphthalene (14, 28.44 g, 200 mmol) and NBS (39.16 g, 220 mmol) in MeCN

◦

(300 mL) was stirred at 30-40 C until completion of the reaction as indicated by TLC analysis (typically

within 12 h). On cooling to room temperature, the reaction mixture was poured into ice-water (600 mL),

and the resulting mixture was extracted with CH₂Cl₂(500 mL

washed successively with 5% aqueous Na₂S₂O₃(200 mL), saturated aqueous Na₂CO₃(100 mL

and 5% brine (200 mL), dried (Na₂SO₄) and evaporated on a rotary evaporator to give a residue, which

×

3). The combined extracts were

×

3)

was puriﬁed by column chromatography to afford 1-bromo-4-methylnaphthalene (15

)

.

Colorless oil,

1

42.01 g (98%). H-NMR (DMSO-d₆, 400 MHz)

δ: 8.14–8.16 (m, 1H), 8.07–8.09 (m, 1H), 7.76 (d, J = 7.6 Hz,

1H), 7.66–7.70 (m, 2H), 7.30 (d, J = 7.6 Hz, 1H), 2.63 (s, 3H).

A mixture of 15

,

9k or 9m (190 mmol) and CuCN (49.00 g, 570 mmol) in DMF (500 mL) were

◦

stirred at 130 C (for 15 and 9m) or reﬂux (for 9k) in N₂atmosphere for 12 h, when TLC analysis

indicated completion of reaction. On cooling to room temperature, the reaction mixture was diluted

with CH₂Cl₂(1000 mL), and the resulting mixture was further stirred for 1 h and ﬁltered off. The ﬁltrate

was washed with 5% brine (500 mL

which was puriﬁed by column chromatography to afford 16, 10k or 10m.

×

5), dried (Na₂SO₄) and evaporated on a rotary evaporator,

◦

4-Methyl-1-naphthonitrile (16): White solid; 24.78 g (78%); m.p. 54–55 C (literature value, 53–54 ^◦C [49]).

¹H-NMR (DMSO-d₆, 400 MHz)

δ

: 8.20 (d, J = 8.0 Hz, 1H), 8.11 (d, J = 8.0 Hz, 1H), 8.04 (d, J = 7.2 Hz,

1H), 7.72–7.82 (m, 2H), 7.53 (d, J = 7.2 Hz, 1H), 2.74 (s, 3H).

Benzo[b]furan-5-carbonitrile (10k): White solid; 23.12 g (85%); m.p. 81–83 ^◦C (literature value,

1

81–82 ^◦C [50]). H-NMR (DMSO-d₆, 400 MHz)

δ: 8.22 (d, J = 1.2 Hz, 1H), 8.19 (d, J = 2.0 Hz, 1H), 7.81

(d, J = 8.4 Hz, 1H), 7.73–7.75 (m, 1H), 7.08 (d, J = 1.6 Hz, 1H).

◦

2-Naphthonitrile (10m): White solid; 20.96 g (72%); m.p. 63–65 C (literature value, 65–66 C [51]).

¹H-NMR (DMSO-d₆, 400 MHz) δ: 8.57 (s, 1H), 8.03–8.11 (m, 3H), 7.65–7.78 (m, 3H).

To a stirred solution of 13, 10k or 10m (130 mmol) in dried THF (150 mL) cooled in an ice-water

bath was added portionwise LiAlH₄(6.41 g, 169 mmol). Thereafter the reaction mixture was stirred at

room temperature for 1 h and then at reﬂux for another 5 h, when the reaction completed as indicated

Molecules 2018, 23, 252

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by TLC analysis. On cooling to room temperature, the reaction mixture was carefully poured into

ice-water (500 mL) while stirring, and the resulting mixture was diluted with CH₂Cl₂(300 mL), stirred

for 0.5 h and ﬁltered off through Celite. The organic phase was separated from the ﬁltrate, and the

aqueous phase was back-extracted with CH₂Cl₂(200 mL

washed with saturated brine (200 mL), dried (Na₂SO₄) and evaporated on a rotary evaporator to

give a residue, which was puriﬁed by column chromatography through a short silica gel column to

×

2). The combined organic phases were

afford 2d, 2k or 2m. These amines were used directly in the next step without further puriﬁcation

and characterization.

3.2.2. General Procedure for the Synthesis of Substituted Methylamines 2ha–2hi

To a stirred solution of 5-bromothiophene-2-carbaldehyde (18, 38.22 g, 200 mmol) and

phenylboronic acid (26.82 g, 220 mmol) in dioxane/H₂O (9/1 by v/v, 600 mL in total), K₂CO₃(110.56 g,

800 mmol) and Pd(PPh₃)₄(11.56 g, 10 mmol) were added. The reaction mixture was heated at reﬂux

for 10 h in N₂atmosphere. On cooling to room temperature, the reaction mixture was ﬁltered off. The

organic phase was evaporated on a rotary evaporator, and the residue thus obtained was extracted

with CH₂Cl₂(200 mL

×

3). The combined extracts were washed with 5% brine (200 mL), dried

(Na₂SO₄) and evaporated on a rotary evaporator to give a residue, which was puriﬁed by column

chromatography to afford 5-pheny_◦lthiophene-2-carbaldehyde (10hg). White solid; 36.90 g (98%); m.p.

◦

89–91 C (literature value, 92–93 C [52]). ¹H-NMR (DMSO-d₆, 400 MHz)

δ

: 9.91 (s, 1H), 8.04 (d,

J = 4.0 Hz, 1H), 7.79–7.81 (m, 2H), 7.74 (d, J = 4.0 Hz, 1H), 7.41–7.50 (m, 3H).

To a stirred solution of 9ha–9hd (200 mmol) in dried DMF (43.86 g, 600 mmol) cooled in an

ice-water bath was added dropwise POCl₃(46.00 g, 300 mmol). The resulting mixture was stirred at

this temperature for 30 min and then at 100 ^◦C for another 5 h. After cooling to room temperature,

the reaction mixture was poured carefully into ice-water (300 mL). The mixture thus obtained was

extracted with CH₂Cl₂(300 mL

×

3), and the combined extracts were washed successively with 5%

brine (200 mL), 10% aqueous K₂CO₃(200 mL) and 5% brine (200 mL), dried (Na₂SO₄) and evaporated

on a rotary evaporator to afford a residue, which was puriﬁed by column chromatography to yield

10ha–10hd.

1

5-Chlorothiophene-2-carbaldehyde (10ha): Colorless oil; 22.00 g (75%). H-NMR (DMSO-d₆, 400 MHz) δ:

9.82 (s, 1H), 7.95 (d, J = 4.0 Hz, 1H), 7.39 (d, J = 4.0 Hz, 1H). The ¹H-NMR data were in good agreement

with those reported [53].

1

5-Methylthiophene-2-carbaldehyde (10hb): Colorless oil; 21.20 g (84%). H-NMR (DMSO-d₆, 400 MHz)

δ:

9.80 (s, 1H), 7.84 (d, J = 4.0 Hz, 1H), 7.04–7.05 (m, 1H), 2.54 (s, 3H). The ¹H-NMR data were in good

agreement with those reported [53].

1

5-Ethylthiophene-2-carbaldehyde (10hc): Colorless oil; 22.72 g (81%). H-NMR (DMSO-d₆, 400 MHz),

δ:

9.81 (s, 1H), 7.85 (d, J = 3.6 Hz, 1H), 7.06–7.07 (m, 1H), 2.88 (q, J = 7.5 Hz, 2H), 1.25 (t, J = 7.4 Hz, 3H).

3-Methylthiophene-2-carbaldehyde (10hd): Colorless oil; 22.46 g (89%). An inseparable mixture of

1

regioisomers as indicated by H-NMR. The H-NMR data were in good agreement with those

reported [38].

To a stirred solution of 9he

atmosphere was added dropwise 1.6 M n-BuLi in n-hexane (125 mL, 200 mmol) via syringe, and the

resulting solution was stirred at

78 ^◦C for 1 h ( for 9he and 9hh) or returned to room temperature

for 5 h (for 9hi) before dropwise addition of dried DMF (21.93 g, 300 mmol) via syringe. Thereafter

the reaction mixture was stirred at

78 ^◦C for 0.5 h and at room temperature for another 1 h. The

reaction mixture was poured into ice-water (600 mL) while stirring and the resulting mixture was

extracted with CH₂Cl₂(300 mL 3). The combined extracts were washed with 5% brine (500 mL),

,

9hh or 9hi (200 mmol) in dried THF (200 mL) held at

−

78 ^◦C in N₂

−

×

dried (Na₂SO₄) and evaporated on a rotary evaporator to give a residue, which was puriﬁed by column

chromatography to afford the pure product 10he, 10hh or 10hi.

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4-Methylthiophene-2-carbaldehyde (10he): Colorless oil; 23.97 g (95%). An inseparable mixture of

1

regioisomers as indicated by H-NMR. The H-NMR data were in good agreement with those

reported [38].

1

Benzo[b]thiophene-2-carbaldehyde (10hh): Colorless oil; 29.80 g (92%). H-NMR (DMSO-d₆, 400 MHz)

δ:

10.14 (s, 1H), 8.43 (s, 1H), 8.09–8.12 (m, 2H), 7.56–7.60 (m, 1H), 7.48–7.52 (m, 1H). The ¹H-NMR data

were in good agreement with those reported [54].

◦

1

Bibenzo[b,d]thiophene-4-carbaldehyde (10hi): White solid; 36.08 g (85%); m.p. 117–119 C. H-NMR

(CDCl₃, 400 MHz) : 10.27 (s, 1H), 8.40 (d, J = 7.6 Hz, 1H), 8.17–8.22 (m, 1H), 7.93–7.97 (m, 2H), 7.64 (t,

J = 7.6 Hz, 1H), 7.47–7.54 (m, 2H). The ¹H-NMR data were in good agreement with those reported [55].

δ

To a stirred solution of 10ha 10hi (145 mmol) and NH₂OH HCl (20.15 g, 290 mmol) in 90% EtOH

–

·

(300 mL) was added dropwise an aqueous solution prepared by dissolving K₂CO₃(24.05 g, 174 mmol)

in a minimal amount of water. After addition, the mixture was stirred at room temperature until

the reaction completed as indicated by TLC analysis (typically within 5 h). The reaction mixture

was concentrated to about one-third of its original volume on a rotary evaporator and the residue

was poured into ice-water (400 mL). The resulting mixture was adjusted to pH 6–7 with diluted

hydrochloric acid and extracted with CH₂Cl₂(200 mL

5% brine (200 mL), dried (Na₂SO₄) and evaporated on a rotary evaporator to give a residue, which was

×

3). The combined extracts were washed with

puriﬁed by recrystallization from n-hexane/EtOAc (5/1 by v/v) to give 11ha–11hi. Oximes 11ha–11hi

were used directly in the next step without further characterization.

The synthesis of 2ha–2hi from 11ha–11hi by the reduction with LiAlH₄was carried out using the

identical operation to that for the synthesis of 2d, 2k and 2m from 13, 10k and 10m, respectively.

3.2.3. General Procedure for the Synthesis of Isothiocyanates 3c–3n and 3ha–3hi

A suspension of 16 (23.40 g, 140 mmol), BPO (5.09 g, 21 mmol) and NBS (29.90 g, 168 mmol) in

CCl₄(400 mL) was stirred at reﬂux in N₂atmosphere until the completion of reaction as indicated by

TLC analysis (typically within 12 h; once the reaction commenced, 2.55 g of BPO was added every

5 h until the reaction completed). The reaction mixture was cooled to room temperature and ﬁltered

off, and the ﬁltrate was successively washed with saturated aqueous NaHCO₃(200 mL

brine (200 mL), dried (Na₂SO₄) and evaporated on a rotary evaporator to afford a residue, which was

×

5) and 5%

puriﬁed by column chromatography to yield (4-cyano-1-naphthyl)methyl bromide (17). White solid;

◦

31.35 g (91%); m.p. 113–115 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.34–8.37 (m, 1H), 8.13–8.21 (m, 2H),

7.82–7.89 (m, 3H), 5.27 (s, 2H).

To a stirred solution of 17 (30.76 g, 125 mmol) in DMF (300 mL) was added KSCN (24.30 g,

250 mmol), and the mixture thus obtained was stirred for 4 h at 140 ^◦C in N₂atmosphere until the

completion of reaction as indicated by TLC analysis. On cooling to room temperature, the reaction

mixture was poured into ice-water (600 mL) while stirring. The resulting mixture was exacted with

CH₂Cl₂(200 mL

×

3). The combined extracts were washed with 5% brine (300 mL), dried (Na₂SO₄) and

evaporated on a rotary evaporator to give a residue, which was puriﬁed by column chromatography

to afford (4-cyano-1-naphthyl)methyl isothiocyanate (3l). White solid; 20.47 g (73%); m.p. 113–115

^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.18–8.22 (m, 3H), 7.81–7.89 (m, 2H), 7.75 (d, J = 7.6 Hz, 1H),

5.56 (s, 2H).

To a stirred solution of thiophosgene (15.18 g, 132 mmol) in dried CH₂Cl₂(150 mL) cooled in

an ice-water bath was added dropwise a solution prepared by dissolving 2c 2k 2m 2n or 2ha 2hi

–

,

–

(120 mmol) and DIPEA (46.53 g, 360 mmol) in dried CH₂Cl₂(150 mL). The resulting mixture was

stirred for 1 h in an ice-water bath and for another 1 h at room temperature. The reaction mixture was

then poured into ice-water (300 mL) while stirring. The organic phase was separated, and the aqueous

phase was back-extracted with CH₂Cl₂(200 mL

successively with 5% hydrochloric acid (100 mL

×

2). The combined organic phases were washed

2; for 3f and 3n, the washing with 5% hydrochloric

×

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acid is omitted) and saturated brine (300 mL), dried (Na₂SO₄) and evaporated on a rotary evaporator

to give a residue, which was puriﬁed by column chromatography to afford 3c–3k, 3m–3n or 3ha–3hi.

Cyclohexylmethyl isothiocyanate (3c): Colorless oil; 18.26 g (98%). ¹H-NMR (DMSO-d₆, 400 MHz)

δ:

3.51 (d, J = 6.4 Hz, 2H), 1.60–1.70 (m, 6H), 1.17–1.27 (m, 2H), 1.08–1.14 (m, 1H), 0.93–1.03 (m, 2H).

The ¹H-NMR data were in good agreement with those reported [56].

1-Adamantylmethyl isothiocyanate (3d): White solid; 22.89 g (92%); m.p. 76–77 ^◦C. ¹H-NMR (DMSO-d₆,

400 MHz) δ: 3.33 (s, 2H), 1.98 (s, 3H), 1.67–1.70 (m, 3H), 1.57–1.60 (m, 3H), 1.50–1.51 (m, 6H).

1

Benzyl isothiocyanate (3e): Colorless oil; 15.94 g (89%). H-NMR (DMSO-d₆, 400 MHz)

δ: 7.34–7.44 (m,

5H), 4.93 (s, 2H). The ¹H-NMR data were in good agreement with those reported [57].

1

3-Pyridinylmethyl isothiocyanate (3f): Colorless oil; 10.81 g (ca 61%). H-NMR (DMSO-d₆, 400 MHz)

δ

:

8.59 (d, J = 1.6 Hz, 1H), 8.56 (d, J = 1.2 Hz and 4.8 Hz, 1H), 7.82 (d, J = 7.6 Hz, 1H), 7.45 (dd, J = 4.8 Hz

and 8.0 Hz, 1H), 4.99 (s, 2H). The ¹H-NMR data were in good agreement with those reported [56].

2-Furanylmethyl isothiocyanate (3g): Colorless oil; 15.87g (95%). ¹H-NMR (DMSO-d₆, 400 MHz)

δ:

7.71 (s, 1H), 6.46–6.47 (m, 2H), 4.95 (s, 2H). The ¹H-NMR data were in good agreement with those

reported [56].

1

2-Thiophenylmethyl isothiocyanate (3h): Colorless oil; 16.39 g (88%). H-NMR (DMSO-d₆, 400 MHz)

δ

:

7.56 (dd, J = 1.2 Hz and 5.2 Hz, 1H), 7.14 (d, J = 3.2 Hz, 1H), 7.03 (dd, J = 3.6 Hz and 5.2 Hz, 1H),

5.12 (s, 2H).

Biphenyl-4-methyl isothiocyanate (3i): White solid; 23.25 g (86%); m.p. 66–67 ^◦C. ¹H-NMR (DMSO-d₆,

400 MHz) δ

: 7.66–7.72 (m, 4H), 7.45–7.48 (m, 4H), 7.35–7.39 (m, 1H), 4.97 (s, 2H). The ¹H-NMR data

were in good agreement with those reported [56].

Diphenylmethyl isothiocyanate (3j): Colorless oil; 22.17 g (82%). ¹H-NMR (DMSO-d₆, 400 MHz)

δ:

7.31–7.43 (m, 10H), 6.50 (s, 1H). The ¹H-NMR data were in good agreement with those reported [58].

1

Benzo[b]furan-5-methyl isothiocyanate (3k): Colorless oil; 20.21 g (89%). H-NMR (DMSO-d₆, 400 MHz)

δ

:

8.03 (d, J = 2.4 Hz, 1H), 7.68 (d, J = 1.2 Hz, 1H), 7.63 (d, J = 8.4 Hz, 1H), 7.33 (dd, J = 2.0 Hz and 8.4 Hz,

1H), 7.00 (d, J = 0.8 Hz and 2.4 Hz, 1H), 5.00 (s, 2H).

2-Naphthylmethyl isothiocyanate (3m): White solid; 20.33 g (85%); m.p. 62–63 ^◦C. ¹H-NMR (DMSO-d₆,

400 MHz) δ: 7.90–7.98 (m, 4H), 7.49–7.57 (m, 3H), 5.11 (s, 2H).

◦

Quinoline-6-methyl isothiocyanate (3n): White solid; 18.74 g (78%); m.p. 186–188 C. ¹H-NMR (DMSO-d₆,

400 MHz) : 9.22 (dd, J = 1.2 Hz and 8.8 Hz, 1H), 9.03 (d, J = 8.4 Hz, 1H), 8.38 (d, J = 8.8 Hz, 1H), 8.27 (s,

δ

1H), 8.03 (dd, J = 1.6 Hz and 8.8 Hz, 1H), 7.98 (dd, J = 5.2 Hz and 8.4 Hz, 1H), 5.28 (s, 2H).

(5-Chloro-2-thiophenyl)methyl isothiocyanate (3ha): Colorless oil; 19.80 g (87%). ¹H-NMR (DMSO-d₆,

400 MHz) δ: 7.03–7.05 (m, 2H), 5.06 (s, 2H).

1

(5-Methyl-2-thiophenyl)methyl isothiocyanate (3hb): Colorless oil; 16.66 g (82%). H-NMR (DMSO-d₆,

400 MHz) δ: 6.92 (d, J = 3.6 Hz, 1H), 6.69–6.70 (m, 1H), 5.01 (s, 2H), 2.43 (s, 3H).

(5-Ethyl-2-thiophenyl)methyl isothiocyanate (3hc): Colorless oil; 18.69 g (92%). ¹H-NMR (DMSO-d₆,

400 MHz)

δ: 6.93 (d, J = 3.6 Hz, 1H), 6.73 (d, J = 3.6 Hz, 1H), 5.02 (s, 2H), 2.78 (q, J = 7.5 Hz, 2H), 1.22 (t,

J = 7.6 Hz, 3H).

1

(3-Methyl-2-thiophenyl)methyl isothiocyanate (3hd): Colorless oil; 11.98 g (59%). H-NMR (DMSO-d₆,

400 MHz) δ: 7.43 (d, J = 5.2 Hz, 1H), 6.91 (d, J = 4.8 Hz, 1H), 5.03 (s, 2H), 2.20 (s, 3H).

1

(4-Methyl-2-thiophenyl)methyl isothiocyanate (3he): Colorless oil; 10.56 g (52%). H-NMR (DMSO-d₆,

400 MHz) δ: 7.12 (s, 1H), 6.95 (s, 1H), 5.05 (s, 2H), 2.18 (s, 3H).

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1

(3-Thiophenyl)methyl isothiocyanate (3hf) : Colorless oil; 15.46 g (83%). H-NMR (DMSO-d₆, 400 MHz)

: 7.58–7.60 (m, 1H), 7.53 (d, J = 2.0 Hz, 1H), 7.13 (dd, J = 0.8 Hz and 5.2 Hz, 1H), 4.90 (s, 2H).

(5-Phenyl-2-thiophenyl)methyl isothiocyanate (3hg): White solid; 26.37 g (95%); m.p. 63–65 ^◦C. ¹H-NMR

δ

(DMSO-d₆, 400 MHz) δ: 7.63–7.65 (m, 2H), 7.40–7.44 (m, 3H), 7.30–7.34 (m, 1H), 7.15 (d, J = 4.0 Hz, 1H),

5.14 (s, 2H).

(Benzo[b]thiophen-2-yl)methyl isothiocyanate (3hh): White solid; 23.65 g (96%); m.p. 62–64 ^◦C. ¹H-NMR

(DMSO-d₆, 400 MHz) : 7.96–7.98 (m, 1H), 7.84–7.86 (m, 1H), 7.46 (s, 1H), 7.35–7.41 (m, 2H), 5.25 (s, 2H).

δ

◦

(Dibenzo[b,d]thiophen-4-yl)methyl isothiocyanate (3hi): White solid; 28.19 g (92%); m.p. 81–83 C. ¹H-NMR

(DMSO-d₆, 400 MHz) δ: 8.39–8.42 (m, 2H), 8.09–8.11 (m, 1H), 7.53–7.60 (m, 4H), 5.24 (s, 2H).

3.2.4. General Procedure for the Synthesis of Thiones 5a–5n and 5ha–5hi

A mixture of isothiocyanate 3a–3n or 3ha–3hi (90 mmol) and formic hydrazide (6.49 g, 108 mmol)

in THF (150 mL) was stirred at room temperature until the reaction completed as indicated by TLC

analysis, when a white slurry formed. The crystals were collected by vacuum ﬁltration and dried in

vacuo at room temperature to give the intermediate 4a

next step without further puriﬁcation and characterization. Thus, 4a

THF (150 mL; for 4a 4b) or DMF (150 mL; for 4c 4n and 4ha 4hi) followed by addition of aqueous

–

4n or 4ha

–

4hi, which was used directly in the

–

4n or 4ha 4hi was dissolved in

–

K₂CO₃prepared by dissolving K₂CO₃(12.44 g, 90 mmol) in a minimal amount of water, and the

◦

solution thus obtained was stirred at 50 C until completion of the reaction as indicated by TLC

analysis (typically within 5 h). On cooling to room temperature, for 4a–4b: the reaction mixture

was directly concentrated on a rotary evaporator to remove THF, and the aqueous residue was

adjusted to pH 5–6 and further evaporated to dryness to give a residue, which was puriﬁed by column

chromatography to afford 5a–5b; for 4c–4n or 4ha–4hi: the reaction mixture was poured into ice-water

(300 mL), and the resulting mixture was adjusted to pH 5–6 with diluted hydrochloric acid to give a

white slurry. The white crystals were collected by vacuum ﬁltration, washed with water and dried

in vacuo to give the crude product 5c

–5n or 5ha–5hi as a white solid, which was triturated with

EtOAc/n-hexane to yield the pure product 5c–5n or 5ha–5hi.

◦

4-Ethyl-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5a): White solid; 8.08 g (78%); m.p. 169–171 C. ¹H-NMR

(DMSO-d₆, 400 MHz)

δ

: 13.61 (brs, 1H), 8.38 (s, 1H), 3.42 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ:

166.36, 142.60, 31.27.

◦

4-n-Propyl-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5b): White solid; 8.49 g (73%); m.p. 90–91 C.

¹H-NMR (DMSO-d₆, 400 MHz)

3H). ¹³C-NMR (DMSO-d₆, 100 MHz) δ: 165.57, 141.53, 39.32, 13.92.

δ: 13.63 (brs, 1H), 8.45 (s, 1H), 3.91 (q, J = 7.2 Hz, 2H), 1.26 (t, J = 7.2 Hz,

4-(Cycloh_◦exylmethyl)-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5c): White solid; 11.90 g (67%); m.p.

1

138–140 C. H-NMR (DMSO-d₆, 400 MHz)

δ: 13.64 (brs, 1H), 8.42 (d, J = 1.2 Hz, 1H), 3.75 (d,

J = 7.2 Hz, 1H), 1.79–1.88 (m, 1H), 1.59–1.68 (m, 3H), 1.50–1.53 (m, 2H), 1.10–1.20 (m, 3H), 0.90–0.99 (m,

2H). ¹³C-NMR (DMSO-d₆, 100 MHz) δ: 166.15, 142.36, 49.58, 36.14, 29.69, 25.75, 24.97.

4-(1-Adamantylmethyl)-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5d): White solid; 18.40 g (82%); m.p.

223–225 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.65 (brs, 1H), 8.34 (s, 1H), 3.68 (s, 2H), 1.93 (s, 3H),

1.62–1.65 (m, 3H), 1.47–1.56 (m, 9H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 167.29, 142.86, 54.42, 39.85,

36.14, 34.59, 27.48.

◦

4-Benzyl-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5e): White solid; 13.08 g (76%); m.p. 121–123 C.

¹H-NMR (DMSO-d₆, 400 MHz) : 13.76 (brs, 1H), 8.54 (s, 1H), 7.29–7.38 (m, 5H), 5.16 (s, 2H). ¹³C-NMR

δ

(DMSO-d₆, 100 MHz) δ: 166.28, 142.04, 135.99, 128.60, 127.85, 127.75, 46.88.

4-(3-Pyridinylmethyl)-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5f): White solid; 12.46 g (72%); m.p.

211–213 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.80 (brs, 1H), 8.62 (d, J = 2.0 H, 1Hz), 8.60 (s, 1H),

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8.51–8.52 (m, 1H), 7.75–7.78 (m, 1H), 7.37–7.40 (m, 1H), 5.20 (s, 2H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ:

166.22, 149.19, 149.10, 142.02, 135.66, 131.61, 123.62, 44.70.

4-(2-Furanylmethyl)-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5g): White solid; 12.72 g (78%); m.p.

133–135 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.76 (brs, 1H), 8.45 (s, 1H), 7.64 (d, J = 1.6 Hz, 1H),

6.43–6.46 (m, 2H), 5.17 (s, 2H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 166.04, 148.30, 143.35, 141.74, 110.75,

109.46, 40.41.

4-(2-Thiophenylmethyl)-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5h): White solid; 13.50 g (76%); m.p.

108–110 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.74 (brs, 1H), 8.54 (s, 1H), 7.47 (dd, J = 1.2 Hz and

4.8 Hz, 1H), 7.20 (d, J = 3.2 Hz, 1H), 6.99–7.01 (m, 1H), 5.33 (s, 2H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ:

165.84, 141.62, 137.60, 127.85, 126.91, 126.81, 41.73.

4-(Biphenyl-4-methyl)-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5i): White solid; 18.53 g (77%); m.p.

◦

1

178–180 C. H-NMR (DMSO-d₆, 400 MHz) δ: 13.79 (brs, 1H), 8.59 (d, J = 1.2 Hz, 1H), 7.63–7.66

(m, 4H), 7.43–7.47 (m, 4H), 7.36 (t, J = 7.2 Hz, 1H), 5.21 (s, 2H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ:

166.29, 142.09, 139.77, 139.59, 135.16, 128.89, 128.40, 127.51, 126.91, 126.63, 46.61.

4-(Diphenylmethyl)-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5j): White solid; 18.04 g (75%); m.p. 166–168 ^◦C.

¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.94 (brs, 1H), 8.50 (s, 1H), 7.35–7.43 (m, 6H), 7.18–7.19 (m, 4H),

7.08 (s, 1H). ¹³C-NMR (DMSO-d₆, 100 MHz) δ: 166.38, 140.77, 138.00, 128.84, 128.15, 127.99, 61.08.

4-(Benzo[b]furan-5-methyl)-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5k): White solid; 14.78 g (71%); m.p.

151–153 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.75 (brs, 1H), 8.54 (s, 1H), 7.99 (d, J = 2.0 Hz, 1H),

7.66 (d, J = 1.2 Hz, 1H), 7.58 (d, J = 8.4 Hz, 1H), 7.35–7.38 (m, 1H), 6.96 (d, J = 2.8 Hz, 1H), 5.24 (s, 2H).

¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 166.17, 153.86, 146.64, 142.00, 130.77, 127.39, 124.46, 120.93, 111.41,

106.71, 47.00.

4-((4-Cyano-1-naphthyl)methyl]-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5l): White solid; 15.64 g (72%);

◦

m.p. 218–220 C. ¹H-NMR (DMSO-d₆, 400 MHz)

8.19 (d, J = 8.0 Hz, 1H), 8.16 (d, J = 7.2 Hz, 1H), 7.79–7.88 (m, 2H), 7.25 (d, J = 7.6 Hz, 1H), 5.74 (s, 2H).

¹³C-NMR (DMSO-d₆, 100 MHz)

: 166.49, 142.16, 137.78, 132.88, 131.56, 129.83, 129.12, 128.35, 125.09,

124.64, 124.30, 117.36, 109.18, 45.06.

δ: 13.94 (brs, 1H), 8.46 (s, 1H), 8.36 (d, J = 8.4 Hz, 1H),

δ

4-(2-Naphthylmethyl)-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5m): White solid; 14.77 g (68%); m.p.

◦

165–167 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.80 (brs, 1H), 8.59 (d, J = 1.2 Hz, 1H), 7.88–7.92 (m, 3H),

7.81 (s, 1H), 7.49–7.54 (m, 3H), 5.33 (s, 2H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 166.35, 142.16, 133.51,

132.67, 132.39, 128.36, 127.72, 127.55, 126.53, 126.45, 126.25, 125.63, 47.12.

4-(Quinoline-6-methyl)-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5n): White solid; 16.36 g (75%); m.p.

◦

272–275 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.82 (brs, 1H), 8.89 (dd, J = 1.6 Hz and 4.4 Hz, 1H), 8.62

(s, 1H), 8.35 (d, J = 8.4 Hz, 1H), 8.01 (d, J = 8.8 Hz, 1H), 7.85 (s, 1H), 7.75 (dd, J = 2.0 Hz and 8.8 Hz, 1H),

7.51–7.55 (m, 1H), 5.37 (s, 2H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 166.36, 150.76, 147.16, 142.19, 135.97,

134.17, 129.41, 129.15, 127.55, 126.69, 121.81, 46.85.

4-((5-Chloro-2-thiophenyl)methyl]-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5ha): White solid; 15.02 g (72%);

◦

m.p. 176–178 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.79 (brs, 1H), 8.55 (s, 1H), 7.08 (d, J = 3.6 Hz, 1H),

7.01 (d, J = 3.6 Hz, 1H), 5.25 (s, 2H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 165.77, 141.54, 136.87, 128.71,

128.02, 126.34, 42.01.

4-((5-Methyl-2-thiophenyl)methyl]-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5hb): White solid; 13.31 g

◦

1

(70%); m.p. 131–133 C. H-NMR (DMSO-d₆, 400 MHz) δ: 13.72 (brs, 1H), 8.50 (s, 1H), 6.98 (d,

J = 3.2 Hz, 1H), 6.66–6.67 (m, 1H), 5.23 (s, 2H), 2.37 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 165.81,

141.56, 140.31, 135.16, 127.87, 125.00, 42.01, 14.87.

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4-((5-Ethyl-2-thiophenyl)methyl]-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5hc): White solid; 15.21 g (75%);

m.p. 64–66 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.73 (brs, 1H), 8.51 (s, 1H), 7.00 (d, J = 3.6 Hz, 1H),

6.70 (d, J = 3.2 Hz, 1H), 5.25 (s, 2H), 2.73 (q, J = 7.5 Hz, 2H), 1.18 (t, J = 7.6 Hz, 3H). ¹³C-NMR (DMSO-d₆,

100 MHz) δ: 165.84, 147.80, 141.56, 134.82, 127.65, 123.22, 42.06, 22.75, 15.72.

4-((3-Methyl-2-thiophenyl)methyl]-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5hd): White solid; 14.83 g

◦

1

(78%); m.p. 113–115 C. H-NMR (DMSO-d₆, 400 MHz) δ: 13.74 (brs, 1H), 8.41 (s, 1H), 7.38 (d,

J = 5.2 Hz, 1H), 6.86 (d, J = 5.2 Hz, 1H), 5.26 (s, 2H), 2.28 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ:

165.87, 141.59, 136.18, 130.91, 129.96, 125.12, 40.26, 13.64.

4-((4-Methyl-2-thiophenyl)methyl]-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5he): White solid; 14.45 g

(76%); m.p. 98–100 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.73 (brs, 1H), 8.52 (s, 1H), 7.03 (s, 1H), 6.99

(s, 1H), 5.26 (s, 2H), 2.15 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 165.86, 141.61, 137.39, 136.83, 129.84,

121.71, 41.90, 15.26.

4-((3-Thiophenyl)methyl]-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5hf): White solid; 12.55 g (70%); m.p.

109–110 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.73 (brs, 1H), 8.51 (s, 1H), 7.53 (dd, J = 3.2 Hz and

4.8 Hz, 1H), 7.47 (d, J = 1.6 Hz, 1H), 7.16 (dd, J = 0.8 Hz and 4.8 Hz, 1H), 5.13 (s, 2H). ¹³C-NMR

(DMSO-d₆, 100 MHz) δ: 166.01, 141.86, 136.42, 127.40, 127.06, 124.18, 42.41.

4-((5-Phenyl-2-thiophenyl)methyl]-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5hg): White solid; 16.73 g (68%);

m.p. 160–162 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.78 (brs, 1H), 8.58 (s, 1H), 7.58–7.60 (m, 2H),

7.37–7.41 (m, 3H), 7.30 (t, J = 7.4 Hz, 1H), 7.20 (d, J = 3.6 Hz, 1H), 5.34 (s, 2H). ¹³C-NMR (DMSO-d₆, 100

MHz) δ: 165.88, 143.95, 141.64, 137.14, 133.38, 129.18, 129.09, 127.78, 125.27, 123.27, 42.01.

4-((Benzo[b]thiophen-2-yl)methyl]-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5hh): White solid; 15.80 g (71%);

m.p. 185–188 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.82 (brs, 1H), 8.60 (s, 1H), 7.90–7.92 (m, 1H),

7.81–7.83 (m, 1H), 7.45 (s, 1H), 7.31–7.38 (m, 2H), 5.45 (s, 2H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 166.19,

141.85, 139.50, 138.90, 138.87, 124.79, 124.66, 124.18, 123.80, 122.56, 42.84.

4-((Dibenzo[b,d]thiophen-4-yl)methyl]-2,3-dihydro-4H-1,2,4-triazoline-3-thione (5hi): White solid; 18.20 g

(68%); m.p. 240–242 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

: 13.87 (brs, 1H), 8.46 (s, 1H), 8.35–8.40 (m,

2H), 8.05–8.08 (m, 1H), 7.51–7.56 (m, 3H), 7.29 (d, J = 7.2 Hz, 1H), 5.42 (s, 2H). ¹³C-NMR (DMSO-d₆,

100 MHz) : 166.71, 142.14, 138.15, 136.79, 135.78, 134.94, 129.79, 127.32, 126.14, 125.13, 124.95, 123.00,

δ

122.20, 121.67, 46.32.

3.2.5. General Procedure for the Synthesis of Thiones 5o and 5q

A solution of isothiocyanate 3l or 3h (90 mmol) and NH₂CH₂CH(OMe)₂(11.36 g, 108 mmol)

in THF (150 mL) was stirred at room temperature until the reaction completed as indicated by TLC

analysis. The reaction mixture was evaporated on a rotary evaporator to give the crude intermediate

4o or 4p, which was used directly in the next step without further puriﬁcation. Thus, the crude 4o or

4p was suspended in 25% aqueous H₂SO₄containing 20% acetic acid (by v/v) and stirred at reﬂux

for 3 h when TLC analysis indicated the reaction was completed. On cooling to room temperature,

the reaction mixture was poured into ice-water (450 mL) and the white crystals were collected by

vacuum ﬁltration, washed with water and dried in vacuo to give the crude product 5o or 5q, which

was triturated with EtOAc/n-hexane to yield the pure product 5o or 5q.

1-((4-Cyano-1-naphthyl)methyl)-2,3-dihydro-1H-imidazoline-2-thione (5o): White solid; 17.43 g (73%); m.p.

287–289 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ

: 12.33 (brs, 1H), 8.40 (d, J = 8.4 Hz, 1H), 8.14–8.18 (m,

2H), 7.85 (t, J = 7.4 Hz, 1H), 7.78 (t, J = 7.6 Hz, 1H), 7.18 (d, J = 7.2 Hz, 1H), 6.97–7.01 (m, 2H), 5.73 (s,

2H). ¹³C-NMR (DMSO-d₆, 100 MHz)

: 161.66, 139.23, 132.89, 131.55, 130.03, 129.04, 128.17, 124.97,

δ

124.62, 124.49, 118.38, 117.47, 115.13, 108.77, 46.95.

1-((2-Thiophenyl)methyl)-2,3-dihydro-1H-imidazoline-2-thione (5q): White solid; 12.37 g (70%); m.p.

◦

1

124–126 C. H-NMR (DMSO-d₆, 400 MHz) δ: 12.12 (brs, 1H), 7.43 (d, J = 5.2 Hz, 1H), 7.16 (d, J

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= 3.2 Hz, 1H), 7.08–7.09 (m, 1H), 6.98 (dd, J = 3.6 Hz and 5.2 Hz, 1H), 6.86–6.87 (m, 1H), 5.31 (s, 2H).

¹³C-NMR (DMSO-d₆, 100 MHz) δ: 160.94, 138.85, 127.27, 126.68, 126.32, 117.81, 114.64, 43.57.

3.2.6. Procedure for the Synthesis of (4-Cyano-1-naphthyl)(4-mercapto-3-pyridinyl)methane (5p)

A solution of 17 (49.22 g, 200 mmol) and hexamethylenetetramine (56.07 g, 400 mmol) in 50%

acetic acid was stirred at reﬂux for 6 h followed by addition of concentrated hydrochloric acid (10 mL).

The reﬂux was continued for another 0.5 h, when the reaction completed as indicated by TLC analysis.

On cooling to room temperature, the reaction mixture was concentrated to half its original volume

and poured into ice-water (300 mL) while stirring. The resulting mixture was extracted with CH₂Cl₂

(200 mL

×

3), and the combined extracts were washed successively with saturated aqueous NaHCO₃

3) and 5% brine (300 mL), dried (Na₂SO₄) and evaporated on a rotary evaporator to give

×

a residue, which was puriﬁed by column chromatography to afford 4-cyano-1-naphthaldehyde (19).

Yellow solid; 30.45 g (78%); m.p. 138–141 ^◦C (literature value, 143–144 ^◦C [59]). H-NMR (DMSO-d₆,

1

400 MHz) 10.54 (s, 1H), 9.17–9.21 (m, 1H), 8.41 (d, J = 7.2 Hz, 1H), 8.29 (d, J = 7.2 Hz, 1H), 8.23–8.27 (m,

1H), 7.89–7.93 (m, 2H).

To a stirred solution of 3-bromo-4-chloropyridine (20, 28.86 g, 150 mmol ) in dried THF

(350 mL) held at –78 ^◦C in N₂atmosphere was added dropwise 1.6M n-BuLi in n-hexane (93.75 mL,

150 mmol) via syringe. After addition, the resulting mixture was stirred at this temperature for

another 0.5 h, followed by addition of a solution of 19 (29.28 g, 150 mmol) in dried THF (150 mL)

in a dropwise manner via syringe. The reaction mixture was slowly warmed to room temperature

and stirred at room temperature for another 1 h. The reaction mixture was slowly poured into

ice-water (600 mL). The mixture thus obtained was extracted with CH₂Cl₂(200 mL

×

3), and

the combined extracts were washed with 5% brine (200 mL), dried (Na₂SO₄) and evaporated on

a rotary evaporator to give a residue, which was puriﬁed by column chromatography to afford

(4-chloro-3-pyridinyl)(4-cyano-1-naphthyl)methanol (22). White solid; 29.62 g (67%); m.p. 178–180 ^◦C.

¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.55 (s, 1H), 8.49 (d, J = 5.6 Hz, 1H), 8.21 (d, J = 8.4 Hz, 1H), 8.17 (d,

J = 8.0 Hz, 1H), 8.16 (d, J = 7.6 Hz, 1H), 7.79–7.83 (m, 1H), 7.72–7.76 (m, 1H), 7.58 (d, J = 5.2 Hz, 1H),

7.57 (d, J = 7.6 Hz, 1H), 6.78 (d, J = 5.6 Hz, 1H), 6.62 (d, J = 6.0 Hz, 1H).

To a stirred solution of 22 (26.53 g, 90 mmol) in dried CH₂Cl₂(300 mL) cooled in an ice-water

bath was added thionyl chloride (12.85 g, 108 mmol). After addition, the resulting mixture was

stirred at room temperature until the reaction completed as indicated by TLC analysis (typically

within 4 h) and poured into ice-water (600 mL) while stirring. The mixture thus obtained was

adjusted to pH 7–8 with saturated aqueous NaHCO₃. The organic phase was separated, and the

aqueous phase was back-extracted with CH₂Cl₂(200 mL

×

2). The combined organic phases were

washed with 5% brine (300 mL), dried (Na₂SO₄) and evaporated on a rotary evaporator to give crude

(4-chloro-3-pyridinyl)(4-cyano-1-naphthyl)methyl chloride (23) as a residue, which was used directly

in the next step without further puriﬁcation.

To a stirred solution of crude 23 prepared above (deemed to be 90 mmol) in acetic acid (300 mL)

was added Zn powder (13.08 g, 200 mmol) in a portionwise manner at room temperature, and after

addition, the reaction mixture was stirred at room temperature until the reaction completed as indicated

by TLC analysis (typically within 5 h). The reaction mixture was diluted with CH₂Cl₂(300 mL) and

the resulting mixture was further stirred for 10 min and ﬁltered off through Celite. The ﬁltrate was

evaporated on a rotary evaporator to almost dryness, and the residue was dissolved in CH₂Cl₂(200 mL).

The solution thus obtained was washed successively saturated aqueous NaHCO₃(200 mL) and 5%

brine (200 mL), dried (Na₂SO₄) and evaporated on a rotary evaporator to give a residue, which was

puriﬁed by column chromatography to afford (4-chloro-3-pyridinyl)(4-cyano-1-naphthyl)methane (24).

White solid; 18.48 g (78%); m.p. 155–157 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.48 (d, J = 5.6 Hz, 1H),

8.39 (s, 1H), 8.31 (d, J = 8.4 Hz, 1H), 8.18 (d, J = 8.0 Hz, 1H), 8.08 (d, J = 7.6 Hz, 1H), 7.84 (t, J = 7.4 Hz,

1H), 7.76–7.80 (m, 1H), 7.63 (d, J = 5.2 Hz, 1H), 7.16 (d, J = 7.6 Hz, 1H), 4.68 (s, 2H).

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A solution of 24 (15.33 g, 55 mmol) and Na₂S

·

9H₂O (39.63 g, 165 mmol) in DMF (200 mL) was

◦

stirred at 110 C in N₂atmosphere until the reaction completed as indicated by TLC analysis (typically

within 12 h). On cooling to room temperature, the reaction mixture was concentrated on a rotary

evaporator to about 50 mL and poured into ice-water (600 mL) while stirring, and the mixture thus

obtained was adjusted to pH 5–6 and extracted with CH₂Cl₂(200 mL

phases were washed with 5% brine (100 mL), dried (Na₂SO₄) and evaporated on a rotary evaporator to

×

3). The combined organic

give a residue, which was puriﬁed by column chromatography to afford the pure compound 5p. White

solid; 10.94 g (72%); m.p. 208–211 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ

: 12.38 (brs, 1H), 8.08–8.15 (m,

3H), 7.79 (t, J = 7.8 Hz, 1H), 7.69 (t, J = 7.4 Hz, 1H), 7.56 (d, J = 6.4 Hz, 1H), 7.44 (d, J = 7.6 Hz, 1H), 7.39

(d, J = 6.8 Hz, 1H), 7.29 (s, 1H), 4.60 (s, 2H). ¹³C-NMR (DMSO-d₆, 100 MHz)

: 188.80, 143.10, 137.95,

δ

132.97, 132.87, 131.75, 131.28, 131.19, 130.04, 128.70, 127.81, 126.05, 125.16, 124.92, 117.80, 107.49, 34.86.

3.2.7. General Procedure for the Synthesis of Esters 6a–6x and 6ha–6hi

A mixture of thiones or thiol 5a

(CH₃)₂CBrCO₂Et or ethyl 1-bromocyclobutanecarboxylate (80 mmol) and K₂CO₃(16.59 g, 120 mmol)

in a suitable solvent (200 mL; acetone for 5a 5b or DMF for the others) was stirred at a temperature

speciﬁed in Schemes 1 –5 until the completion of reaction as indicated by TLC analysis (typically within

12 h). On cooling to room temperature (if necessary), for 5a 5b: the reaction mixture was ﬁltered

off and the ﬁltrate was evaporated on a rotary evaporator to give a residue, which was puriﬁed by

column chromatography to afford 6a 6b; for the others: the reaction mixture was poured into ice-water

(300 mL), and the resulting mixture was extracted with CH₂Cl₂(100 mL 3). The combined extracts

were washed with 5% brine (100 mL 5), dried (Na₂SO₄) and evaporated on a rotary evaporator to

–5q or 5ha–5hi (60 mmol), bromoacetates BrCH₂CO₂Me,

–

×

afford the crude product as a residue, which was puriﬁed by column chromatography to yield the

pure product 6c–6x or 6ha–6hi.

◦

Methyl 2-((4-ethyl-4H-1,2,4-triazol-3-yl)thio)acetate (6a): White solid; 9.32 g (83%); m.p. 67–69 C.

¹H-NMR (DMSO-d₆, 400 MHz) : 8.53 (s, 1H), 4.03 (s, 2H), 3.63 (s, 3H), 3.58 (s, 3H). ¹³C-NMR

δ

(DMSO-d₆, 100 MHz) δ: 168.85, 148.31, 146.26, 52.42, 34.56, 30.73.

Methyl 2-((4-n-propyl-4H-1,2,4-triazol-3-yl)thio)acetate (6b): Colorless oil; 9.42 g (78%). ¹H-NMR

(DMSO-d₆, 400 MHz)

δ: 8.60 (s, 1H), 4.06 (s, 2H), 3.96 (q, J = 7.3 Hz, 2H), 3.63 (s, 3H), 1.31 (t, J = 7.2 Hz,

3H). ¹³C-NMR (DMSO-d₆, 100 MHz) δ: 168.78, 147.56, 145.03, 52.41, 39.37, 34.50, 15.19.

Methyl 2-((4-(cyclohexylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6c): White solid; 13.25 g (82%); m.p.

56–58 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.55 (s, 1H), 4.07 (s, 2H), 3.79 (d, J = 7.2 Hz, 2H), 3.63 (s,

3H), 1.59–1.72 (m, 4H), 1.47–1.50 (m, 2H), 1.09–1.21 (m, 3H), 0.87–0.96 (m, 2H). ¹³C-NMR (DMSO-d₆,

100 MHz) δ: 168.67, 148.12, 145.87, 52.35, 49.80, 37.67, 34.50, 29.63, 25.64, 24.94.

Methyl 2_◦-((4-(1-adamantylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6d): White solid; 15.62 g (81%); m.p.

214–216 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.48 (s, 1H), 4.07 (s, 2H), 3.65 (s, 2H), 3.62 (s, 3H), 1.94 (s,

3H), 1.63–1.66 (m, 3H), 1.52–1.55 (m, 3H), 1.42 (s, 6H). ¹³C-NMR (CDCl₃, 100 MHz)

δ: 168.96, 150.42,

145.75, 56.82, 52.99, 40.22, 36.49, 35.79, 34.72, 28.06.

◦

Methyl 2-((4-benzyl-4H-1,2,4-triazol-3-yl)thio)acetate (6e): White solid; 12.01 g (76%); m.p. 82–84 C.

¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.71 (s, 1H), 7.32–7.40 (m, 3H), 7.22–7.23 (m, 2H), 5.21 (s, 2H), 4.03 (s,

2H), 3.62 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.63, 148.22, 145.77, 135.59, 128.79, 128.06, 127.41,

52.39, 47.34, 34.39.

Methyl 2-((4-(3-pyridinylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6f): Colorless oil; 10.78 g (68%).

¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.74 (s, 1H), 8.53–8.54 (m, 2H), 7.63–7.65 (m, 1H), 7.39–7.42 (m,

1H), 5.27 (s, 2H), 4.05 (s, 2H), 3.61 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.60, 149.36, 148.89,

148.17, 145.75, 135.39, 131.28, 123.80, 52.41, 45.01, 34.40.

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Methyl 2-((4-(2-furanylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6g): White solid; 11.40 g (75%); m.p.

67–69 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.63 (s, 1H), 7.65 (d, J = 1.6 Hz, 1H), 6.48 (d, J = 3.2 Hz,

1H), 6.44–6.46 (m, 1H), 5.25 (s, 2H), 4.04 (s, 2H), 3.63 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.71,

148.16, 148.14, 145.54, 143.72, 110.78, 109.57, 52.41, 40.65, 34.56.

Methyl 2-((4-(2-thiophenylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6h): Colorless oil; 16.30 g (78%).

¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.70 (s, 1H), 7.52–7.53 (m, 1H), 7.12–7.13 (m, 1H), 7.01–7.03 (m, 1H),

5.42 (s, 2H), 4.05 (s, 2H), 3.62 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.66, 147.95, 145.35, 137.68,

127.64, 127.21, 127.02, 52.40, 42.25, 34.61.

Methyl 2-((4-(biphenyl-4-methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6i): White solid; 15.48 g (76%); m.p.

152–154 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

: 8.76 (s, 1H), 7.64–7.68 (m, 4H), 7.45 (t, J = 7.6 Hz, 2H),

7.37 (d, J = 7.2 Hz, 1H), 7.31–7.34 (m, 2H), 5.26 (s, 2H), 4.05 (s, 2H), 3.62 (s, 3H). ¹³C-NMR (DMSO-d₆,

δ

100 MHz)

δ: 168.65, 148.24, 145.81, 139.92, 139.43, 134.74, 128.91, 128.05, 127.59, 127.07, 126.64, 52.40,

47.04, 34.40.

1

Methyl 2-((4-(diphenylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6j): Colorless oil; 16.90 g (83%). H-NMR

(DMSO-d₆, 400 MHz) δ: 8.30 (s, 1H), 7.36–7.44 (m, 6H), 7.18–7.19 (m, 4H), 6.79 (s, 1H), 4.03 (s, 2H), 3.61

(s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.64, 148.70, 144.48, 137.65, 128.92, 128.47, 127.99, 62.12,

52.41, 34.58.

Methyl 2-((4-(benzo[b]furan-5-methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6k): White solid; 14.38 g (79%);

m.p. 82–85 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

: 8.74 (s, 1H), 8.01 (d, J = 2.4 Hz, 1H), 7.60 (d, J = 8.8

Hz, 1H), 7.54 (s, 1H), 7.22–7.24 (m, 1H), 6.96 (d, J = 1.2 Hz, 1H), 5.29 (s, 2H), 4.04 (s, 2H), 3.61 (s, 3H).

¹³C-NMR (DMSO-d₆, 100 MHz)

: 168.66, 153.88, 148.17, 146.83, 145.73, 130.27, 127.53, 124.05, 120.55,

111.59, 106.71, 52.38, 47.46, 34.37.

δ

Methyl 2-((4-((4-cyano-1-naphthyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6l): White solid; 16.65 g (82%);

◦

1

m.p. 135–137 C. H-NMR (DMSO-d₆, 400 MHz)

J = 8.0 Hz, 1H), 8.15 (d, J = 7.6 Hz, 1H), 7.81–7.90 (m, 2H), 7.00 (d, J = 7.2 Hz, 1H), 5.87 (s, 2H), 4.07 (s,

2H), 3.61 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

: 168.59, 148.78, 146.17, 137.70, 132.92, 131.49, 129.58,

δ: 8.72 (s, 1H), 8.30 (d, J = 8.0 Hz, 1H), 8.20 (d,

δ

129.27, 128.47, 125.08, 124.17, 123.82, 117.29, 109.30, 52.45, 45.32, 34.53.

Methyl 2-((4-(2-naphthylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6m): White solid; 15.04 g (80%); m.p.

101–103 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ

: 8.78 (s, 1H), 7.88–7.94 (m, 3H), 7.73 (s, 1H), 7.51–7.55

(m, 2H), 7.37–7.39 (m, 1H), 5.39 (s, 2H), 4.03 (s, 2H), 3.60 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ:

168.63, 148.34, 145.90, 133.06, 132.67, 132.42, 128.58, 127.74, 127.58, 126.57, 126.40, 126.27, 125.16, 52.36,

47.55, 34.38.

Methyl 2_◦-((4-(quinoline-6-methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6n): White solid; 14.33 g (76%); m.p.

141–143 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.90 (dd, J = 1.6 Hz and 4.4 Hz, 1H), 8.80 (s, 1H), 8.35 (d,

J = 8.0 Hz, 1H), 8.03 (d, J = 8.4 Hz, 1H), 7.77 (d, J = 0.8 Hz, 1H), 7.62–7.65 (m, 1H), 7.54 (dd, J = 4.4 Hz

and 8.4 Hz, 1H), 5.44 (s, 2H), 4.04 (s, 2H), 3.59 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.63, 150.93,

148.38, 147.20, 145.95, 136.00, 133.77, 129.65, 128.72, 127.61, 126.46, 121.94, 52.38, 47.26, 34.43.

Ethyl 2-((4-((4-cyano-1-naphthyl)methyl)-4H-1,2,4-triazol-3-yl)thio)-2-methylpropionate (6o): White solid;

14.38 g (63%); m.p. 110–112 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ

: 8.81 (s, 1H), 8.29 (d, J = 8.4 Hz, 1H),

8.20 (d, J = 8.4 Hz, 1H), 8.12 (d, J = 7.6 Hz, 1H), 7.82–7.91 (m, 2H), 6.85 (d, J = 7.6 Hz, 1H), 5.86 (s, 2H),

4.06 (q, J = 7.1 Hz, 2H), 1.52 (s, 6H), 1.10 (t, J = 7.2 Hz, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

: 172.09,

δ

146.45, 138.21, 132.96, 131.44, 129.39, 129.28, 129.24, 128.46, 125.11, 123.97, 123.36, 117.22, 109.28, 61.36,

53.28, 45.41, 25.84, 13.67.

Ethyl 1-((4-((4-cyano-1-naphthyl)methyl)-4H-1,2,4-triazol-3-yl)thio)cyclobutanecarboxylate (6p): White solid;

15.01 g (58%); m.p. 141–143 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.79 (s, 1H), 8.29 (d, J = 8.4 Hz, 1H),

8.20 (d, J = 8.0 Hz, 1H), 8.14 (d, J = 7.2 Hz, 1H), 7.82–7.91 (m, 2H), 6.89 (d, J = 7.6 Hz, 1H), 5.85 (s,

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2H), 4.05 (q, J = 7.1 Hz, 2H), 2.57–2.65 (m, 2H), 2.24–2.31 (m, 2H), 2.03–2.12 (m, 1H), 1.83–1.91 (m, 1H),

1.09 (t, J = 7.0 Hz, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

: 171.64, 146.97, 146.25, 138.08, 132.98, 131.47,

δ

129.44, 129.33, 128.51, 125.15, 123.99, 123.47, 117.26, 109.30, 61.28, 54.07, 45.37, 31.76, 15.55, 13.72.

Methyl 2-((1-((4-cyano-1-naphthyl)methyl)-1H-imidazol-2-yl)thio)acetate (6q): White solid; 14.58 g (72%);

m.p. 116–118 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ

: 8.32 (d, J = 8.0 Hz, 1H), 8.19 (d, J = 8.0 Hz, 1H),

8.13 (d, J = 7.6 Hz, 1H), 7.81–7.89 (m, 2H), 7.34 (s, 1H), 7.07 (d, J = 1.2 Hz, 1H), 6.81 (d, J = 7.6 Hz, 1H),

5.83 (s, 2H), 3.91 (s, 2H), 3.58 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

: 169.09, 139.81, 139.44, 133.02,

δ

131.45, 129.58, 129.51, 129.18, 128.32, 125.04, 124.17, 123.08, 123.06, 117.40, 108.86, 52.26, 47.09, 35.26.

Ethyl 2-((1-((4-cyano-1-naphthyl)methyl)-1H-imidazol-2-yl)thio)-2-methylpropionate (6r): White solid; 17.76

◦

g (78%); m.p. 108–110 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.28 (d, J = 8.4 Hz, 1H), 8.18 (d, J = 8.0 Hz,

1H), 8.10 (d, J = 7.2 Hz, 1H), 7.81–7.89 (m, 2H), 7.46 (d, J = 1.2 Hz, 1H), 7.19 (d, J = 0.4 Hz, 1H), 6.67

(d, J = 7.6 Hz, 1H), 5.86 (s, 2H), 4.04 (q, J = 7.2 Hz, 2H), 1.46 (s, 6H), 1.11 (t, J = 7.0 Hz, 3H). ¹³C-NMR

(DMSO-d₆, 100 MHz) δ: 172.56, 139.92, 137.14, 133.05, 131.38, 130.41, 129.38, 129.21, 128.35, 125.06,

124.11, 123.97, 122.69, 117.36, 108.80, 61.08, 52.84, 47.33, 25.62, 13.72.

Ethyl 1-((1-((4-cyano-1-naphthy_◦l)methyl)-1H-imidazol-2-yl)thio)cyclobutanecarboxylate (6s): White solid;

1

17.85 g (76%); m.p. 135–137 C. H-NMR (DMSO-d₆, 400 MHz)

δ: 8.28 (d, J = 8.4 Hz, 1H), 8.19

(d, J = 7.6 Hz, 1H), 8.10–8.12 (d, J = 7.6 Hz, 1H), 7.81–7.90 (m, 2H), 7.45 (s, 1H), 7.16 (s, 1H), 6.71 (d,

J = 7.6 Hz, 1H), 5.84 (s, 2H), 4.03 (q, J = 7.1 Hz, 2H), 2.53–2.56 (m, 2H), 2.23–2.29 (m, 2H), 1.98–2.07 (m,

1H), 1.76–1.84 (m, 1H), 1.09 (t, J = 7.2 Hz, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 172.24, 139.80, 137.62,

133.05, 131.40, 130.32, 129.41, 129.22, 128.37, 125.07, 123.95, 123.88, 122.79, 117.37, 108.83, 61.02, 54.17,

47.28, 31.33, 15.32, 13.75.

Methyl 2-((3-((4-cyano-1-naphthyl)methyl)pyridin-4-yl)thio)acetate (6t): Colorless oil; 15.05 g (72%).

¹H-NMR (DMSO-d₆, 400 MHz)

δ

: 8.37 (d, J = 5.2 Hz, 1H), 8.28 (d, J = 8.4 Hz, 1H), 8.17 (d, J = 8.4 Hz

1H), 8.12 (s, 1H), 8.07 (d, J = 7.2 Hz, 1H), 7.84 (t, J = 7.4 Hz, 1H), 7.76 (t, J = 7.6 Hz, 1H), 7.34 (d, J = 5.2 H,

1Hz), 7.15 (d, J = 7.6 Hz, 1H), 4.56 (s, 2H), 4.12 (s, 2H), 3.65 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

,

δ:

168.93, 149.63, 147.96, 146.71, 141.46, 132.96, 131.69, 131.07, 130.96, 128.92, 128.07, 125.40, 125.05, 124.84,

119.59, 117.64, 107.90, 52.50, 33.09, 32.16.

Ethyl 2-((3-((4-cyano-1-naphthyl)methyl)pyridin-4-yl)thio)-2-methylpropionate (6u): Colorless oil; 15.93 g

(68%). ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.45 (d, J = 5.2 Hz, 1H), 8.30 (s, 1H), 8.27 (d, J = 8.4 Hz,

1H), 8.17 (d, J = 8.0 Hz, 1H), 8.06 (d, J = 7.6 Hz, 1H), 7.84 (t, J = 7.4 Hz, 1H), 7.78 (t, J = 7.2 Hz, 1H),

7.35 (d, J = 5.2 Hz, 1H), 7.05 (d, J = 3.6 Hz, 1H), 4.64 (s, 2H), 4.12 (q, J = 7.1 Hz, 2H), 1.51 (s, 6H), 1.13

(t, J = 7.2 Hz, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 172.82, 150.91, 147.99, 143.04, 142.39, 135.60,

132.96, 131.66, 130.93, 128.94, 128.06, 126.75, 125.55, 125.05, 124.81, 117.61, 107.83, 61.39, 50.98, 33.44,

25.84, 13.75.

Ethyl 1-((3-((4-cyano-1-naphthyl)methyl)pyridin-4-yl)thio)cyclobutanecarboxylate (6v): White solid; 17.87 g

(74%); m.p. 123–125 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

1H), 8.17 (d, J = 8.0 Hz, 1H), 8.15 (s, 1H), 8.07 (d, J = 7.6 Hz, 1H), 7.84 (t, J = 7.6 Hz, 1H), 7.77 (t, J = 7.6 Hz

δ

: 8.36 (d, J = 5.2 Hz, 1H), 8.27 (d, J = 8.0 Hz

,

1H), 7.12 (d, J = 7.6 Hz, 1H), 7.06 (d, J = 5.6 Hz, 1H), 4.12 (q, J = 7.1 Hz, 2H), 2.79–2.86 (m, 2H), 2.20–2.27

(m, 2H), 2.06–2.17 (m, 1H), 1.90–2.00 (m, 1H), 1.09 (t, J = 7.2 Hz, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ:

172.31, 150.24, 147.90, 145.83, 141.56, 132.94, 131.68, 131.52, 131.04, 128.93, 128.04, 125.33, 125.06, 124.78,

120.76, 117.62, 107.94, 61.47, 50.89, 33.10, 31.74, 16.20, 13.77.

Ethyl 2-((1-((2-thiophenyl)methyl)-1H-imidazol-2-yl)thio)-2-methylpropionate (6w): Oil; 16.78 g (89%).

¹H-NMR (DMSO-d₆, 400 MHz)

δ: 7.44–7.46 (m, 2H), 7.05–7.06 (m, 2H), 6.96–6.98 (m, 1H), 5.40 (s,

2H), 4.03 (q, J = 7.2 Hz, 2H), 1.46 (s, 6H), 1.12 (t, J = 7.2 Hz, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ:

172.56, 139.55, 136.03, 130.07, 126.97, 126.73, 126.27, 123.13, 61.00, 52.80, 44.26, 25.56, 13.70.

Ethyl 1-((1-((2-thiophenyl)methyl)-1H-imidazol-2-yl)thio)cyclobutanecarboxylate (6x): Oil; 15.86 g (82%).

¹H-NMR (DMSO-d₆, 400 MHz)

: 7.46 (dd, J = 1.2 Hz and 5.2 Hz, 1H), 7.06 (d, J = 3.6 Hz, 1H), 7.03 (d,

δ

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J = 0.8 Hz, 1H), 6.96–6.99 (m, 1H), 5.38 (s, 2H), 4.05 (q, J = 7.1 Hz, 2H), 2.51–2.56 (m, 2H), 2.24–2.31 (m,

2H), 2.04–2.11 (m, 1H), 1.78–1.85 (m, 1H), 1.11 (t, J = 7.2 Hz, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ:

172.31, 139.47, 136.49, 129.99, 126.98, 126.75, 126.30, 122.89, 60.94, 54.26, 44.21, 31.21, 15.27, 13.75.

Methyl 2-((4-((5-chloro-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6ha): Oil; 14.22 g (78%).

¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.69 (s, 1H), 7.04 (d, J = 4.0 Hz, 1H), 7.01 (d, J = 4.0 Hz, 1H), 5.36 (s,

2H), 4.07 (s, 2H), 3.63 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.62, 147.94, 145.31, 136.85, 128.88,

127.79, 126.87, 52.41, 42.32, 34.57.

Methyl 2-((4-((5-methyl-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6hb): Oil; 12.75 g (75%).

¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.66 (s, 1H), 6.91 (d, J = 3.2 Hz, 1H), 6.68–6.69 (m, 1H), 5.31 (s, 2H),

4.05 (s, 2H), 3.63 (s, 3H), 2.38 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.67, 147.88, 145.27, 140.56,

135.17, 127.67, 125.31, 52.40, 42.45, 34.58, 14.87.

Methyl 2-((4-((5-ethyl-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6hc): Colorless oil; 12.85 g

1

(72%). H-NMR (DMSO-d₆, 400 MHz)

δ

: 8.69 (s, 1H), 6.94 (d, J = 3.2 Hz, 1H), 6.71 (d, J = 3.2 Hz, 1H),

5.34 (s, 2H), 4.06 (s, 2H), 3.63 (s, 3H), 2.74 (q, J = 7.5 Hz, 2H), 1.18 (t, J = 7.6 Hz, 3H). ¹³C-NMR (DMSO-d₆,

100 MHz) δ: 168.67, 148.06, 147.92, 145.31, 134.86, 127.47, 123.52, 52.39, 42.53, 34.62, 22.74, 15.64.

Methyl 2-((4-((3-methyl-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6hd): Colorless oil; 13.26 g

1

(78%). H-NMR (DMSO-d₆, 400 MHz)

δ

: 8.62 (s, 1H), 7.42 (d, J = 5.2 Hz, 1H), 6.88 (d, J = 5.2 Hz, 1H),

5.33 (s, 2H), 4.03 (s, 2H), 3.62 (s, 3H), 2.25 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.67, 147.90,

145.33, 136.17, 130.70, 130.28, 125.29, 52.39, 40.79, 34.65, 13.45.

Methyl 2-((4-((4-methyl-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6he): Colorless oil; 11.39 g

1

(67%). H-NMR (DMSO-d₆, 400 MHz)

δ

: 8.68 (s, 1H), 7.08 (s, 1H), 6.92 (s, 1H), 5.34 (s, 2H), 4.05 (s, 2H),

3.62 (s, 3H), 2.15 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.66, 147.93, 145.35, 137.45, 137.14, 129.60,

121.85, 52.40, 42.40, 34.62, 15.24.

1

Methyl 2-((4-((3-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6hf): Oil; 10.99 g (68%). H-NMR

(DMSO-d₆, 400 MHz) δ: 8.68 (s, 1H), 7.55–7.57 (m, 1H), 7.42 (d, J = 2.0 Hz, 1H), 7.04–7.05 (m, 1H), 5.19

(s, 2H), 4.04 (s, 2H), 3.62 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.69, 148.02, 145.56, 136.25, 127.50,

126.96, 124.08, 52.40, 42.83, 34.41.

Methyl 2-((4-((5-phenyl-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6hg): White solid; 17.00 g

(82%); m.p. 104–106 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

: 8.74 (s, 1H), 7.59–7.61 (m, 2H), 7.38–7.41

(m, 3H), 7.28–7.32 (m, 1H), 7.13 (d, J = 4.0 Hz, 1H), 5.43 (s, 2H), 4.07 (s, 2H), 3.63 (s, 3H). ¹³C-NMR

(DMSO-d₆, 100 MHz) : 168.66, 148.01, 145.39, 144.18, 137.10, 133.20, 129.11, 128.95, 127.89, 125.26,

δ

123.54, 52.41, 42.50, 34.61.

Methyl 2-((4-((benzo[b]thiophen-2-yl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6hh): White solid; 12.46 g

(65%); m.p. 84–86 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.77 (s, 1H), 7.92–7.94 (m, 1H), 7.82–7.84 (m,

1H), 7.34–7.38 (m, 3H), 5.55 (s, 2H), 4.06 (s, 2H), 3.61 (s, 3H) . ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.64,

148.27, 145.56, 139.25, 138.90, 138.74, 124.81, 124.68, 123.87, 123.84, 122.56, 52.41, 43.19, 34.63.

Methyl 2-((4-((dibenzo[b,d]thiophen-4-yl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (6hi): White solid; 15.30

g (69%); m.p. 144–145 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

: 8.76 (s, 1H), 8.37–8.41 (m, 2H), 8.04–8.07

(m, 1H), 7.53–7.57 (m, 3H), 7.26 (d, J = 7.2 Hz, 1H), 5.52 (s, 2H), 4.01 (s, 2H), 3.60 (s, 3H). ¹³C-NMR

(DMSO-d₆, 100 MHz) : 168.60, 148.76, 146.23, 138.04, 136.78, 135.90, 134.81, 129.46, 127.39, 126.17,

δ

125.22, 124.98, 122.96, 122.23, 121.98, 52.37, 46.76, 34.52.

3.2.8. General Procedure for the Synthesis of Brominated Esters 7a

7⁰hh and 7hi

–7s, 7w–7x, 7ha–7hd, , 7hf–7hg,

7⁰he

A mixture of a substrate to be brominated 6a

–6x or 6ha–6hi (40 mmol) and a brominating reagent

NBS or DBDMH (48 mmol) in a suitable solvent MeCN or CH₂Cl₂(100 mL) was stirred at a suitable

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temperature until the completion of reaction as indicated by TLC analysis (typically within 12 h). The

brominating agent, solvent and temperature are speciﬁed in Schemes 1–5.

The reaction mixture was poured into ice-water (200 mL), and the resulting mixture was extracted

with CH₂Cl₂(100 mL

(100 mL), saturated aqueous Na₂CO₃(100 mL

evaporated on a rotary evaporator to give a residue, which was puriﬁed by column chromatography

to afford the pure product 7a–7s, 7w–7x, 7ha–7hd, 7⁰he, 7hf–7hg, 7⁰hh or 7hi.

×

3). The combined extracts were washed successively with 5% aqueous Na₂S₂O₃

5) and 5% brine (100 mL), dried (Na₂SO₄) and

×

◦

Methyl 2-((5-bromo-4-ethyl-4H-1,2,4-triazol-3-yl)thio)acetate (7a): White solid; 5.54 g (52%); m.p. 86–88 C.

¹H-NMR (DMSO-d₆, 400 MHz) : 4.04 (s, 2H), 3.64 (s, 3H), 3.54 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ

δ: 168.62, 150.98, 130.88, 52.46, 34.54, 31.90.

Methyl 2-((5-bromo-4-n-propyl-4H-1,2,4-triazol-3-yl)thio)acetate (7b): White solid; 9.19 g (82%); m.p. 56–58

◦

C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ

: 4.10 (s, 2H), 3.98 (q, J = 7.2 Hz, 2H), 3.64 (s, 3H), 1.25 (t, J = 7.2 Hz

,

3H). ¹³C-NMR (DMSO-d₆, 100 MHz) δ: 168.53, 150.45, 129.71, 52.47, 40.57, 34.41, 14.38.

Methyl 2-((5-bromo-4-(cyclohexylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7c): Colorless oil; 10.03 g (72%);

¹H-NMR (DMSO-d₆, 400 MHz)

δ: 4.11 (s, 2H), 3.77 (d, J = 7.2 Hz, 2H), 3.64 (s, 3H), 1.61–1.78 (m, 4H),

1.49–1.52 (m, 2H), 1.11–1.18 (m, 3H), 0.95–1.04 (m, 2H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.46,

151.27, 130.47, 52.46, 50.82, 37.40, 34.33, 29.78, 25.53, 24.98.

Methyl 2-((-4-(1-adamantylmethyl)-5-bromo-4H-1,2,4-triazol-3-yl)thio)acetate (7d): White solid; 10.05 g

◦

(69%); m.p. 120–122 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 4.08 (s, 2H), 3.67 (s, 2H), 3.63 (s, 3H), 1.95 (s,

3H), 1.63–1.66 (m, 3H), 1.55–1.58 (m, 3H), 1.52–1.53 (m, 6H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.53,

152.52, 131.40, 56.34, 52.45, 40.20, 35.86, 35.43, 35.20, 27.50.

Methyl 2-((4-benzyl-5-bromo-4H-1,2,4-triazol-3-yl)thio)acetate (7e): White solid; 8.90 g (65%); m.p. 87–89

^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 7.31–7.40 (m, 3H), 7.15–7.17 (m, 2H), 5.21 (s, 2H), 4.08 (s, 2H),

3.63 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.41, 151.44, 134.43, 130.64, 128.87, 128.13, 126.79,

52.48, 48.11, 34.25.

Methyl 2-((5-bromo-4-(3-pyridinylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7f): White solid; 7.55 g (55%);

m.p. 68–70 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.54–8.56 (m, 1H), 8.51 (d, J = 1.6 Hz, 1H), 7.57–7.59

(m, 1H), 7.41–7.44 (m, 1H), 5.28 (s, 2H), 4.11 (s, 2H), 3.63 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ:

168.41, 151.45, 149.16, 148.17, 135.12, 130.56, 130.44, 123.98, 52.51, 45.89, 34.32.

Methyl 2-((5-bromo-4-(2-furanylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7g): White solid; 8.24 g (62%);

◦

1

m.p. 78–80 C. H-NMR (DMSO-d₆, 400 MHz) δ: 7.66 (d, J = 1.2 Hz, 1H), 6.50 (d, J = 3.2 Hz, 1H),

6.45–6.47 (m, 1H), 5.22 (s, 2H), 4.08 (s, 2H), 3.63 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.48,

151.22, 147.06, 143.89, 130.33, 110.79, 109.97, 52.48, 41.79, 34.44.

Methyl 2-((5-bromo-4-(2-thiophenylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7h): White solid; 10.86 g

◦

(78%); m.p. 81–83 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 7.54 (dd, J = 1.2 Hz and 4.8 Hz, 1H), 7.13–7.14

(m, 1H), 7.03 (dd, J = 3.6 Hz and 4.8 Hz, 1H), 5.38 (s, 2H), 4.10 (s, 2H), 3.63 (s, 3H). ¹³C-NMR (DMSO-d₆,

100 MHz) δ: 168.42, 150.97, 136.35, 130.11, 127.90, 127.25, 127.18, 52.49, 43.46, 34.48.

Methyl 2-((4-(biphenyl-4-methyl)-5-bromo-4H-1,2,4-triazol-3-yl)thio)acetate (7i): White solid; 10.88 g (65%);

◦

1

m.p. 140–142 C. H-NMR (DMSO-d₆, 400 MHz)

δ: 7.64–7.69 (m, 4H), 7.44–7.47 (m, 2H), 7.36 (t,

J = 7.4 Hz, 1H), 7.25 (d, J = 8.4 Hz, 2H), 5.26 (s, 2H), 4.11 (s, 2H), 3.64 (s, 3H). ¹³C-NMR (DMSO-d₆, 100

MHz)

34.27.

δ: 168.43, 151.47, 139.99, 139.34, 133.56, 130.66, 128.91, 127.62, 127.42, 127.14, 126.64, 52.50, 47.84,

Methyl 2-((5-bromo-4-(diphenylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7j): Colorless oil; 9.54 g (57%);

¹H-NMR (DMSO-d₆, 400 MHz)

δ: 7.32–7.40 (m, 6H), 7.21–7.25 (m, 4H), 6.93 (s, 1H), 3.95 (s, 2H),

3.55 (s, 3H).

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Methyl 2-((4-(benzo[b]furan-5-methyl)-5-bromo-4H-1,2,4-triazol-3-yl)thio)acetate (7k): White solid; 10.40

g (68%); m.p. 89–91 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

: 8.01 (d, J = 2.0 Hz, 1H), 7.61 (d, J = 8.4 Hz,

δ

1H), 7.45 (d, J = 0.8 Hz, 1H), 7.17 (dd, J = 1.6 Hz and 8.8 Hz, 1H), 6.96–6.97 (m, 1H), 5.30 (s, 2H), 4.09 (s,

2H), 3.62 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.44, 153.87, 151.44, 146.92, 130.60, 129.13, 127.60,

123.38, 119.87, 111.69, 106.73, 52.48, 48.24, 34.25.

Methyl 2-((5-bromo-4-((4-cyano-1-naphthyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7l): White solid; 10.85

g (65%); m.p. 120–122 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

: 8.37 (d, J = 8.0 Hz, 1H), 8.20–8.23 (m, 1H),

8.12 (d, J = 7.6 Hz, 1H), 7.86–7.94 (m, 2H), 6.70 (d, J = 7.6 Hz, 1H), 5.88 (s, 2H), 4.09 (s, 2H), 3.61 (s, 3H).

¹³C-NMR (DMSO-d₆, 100 MHz)

: 168.35, 151.95, 136.65, 132.94, 131.44, 131.26, 129.46, 129.26, 128.51,

δ

125.12, 124.11, 121.74, 117.21, 109.24, 52.50, 46.07, 34.42.

Methyl 2-((5-bromo-4-(2-naphthylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7m): White solid; 9.41 g (60%);

◦

m.p. 91–93 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ

: 7.88–7.96 (m, 3H), 7.64 (s, 1H), 7.51–7.55 (m, 2H), 7.34

(dd, J = 1.6 Hz and 8.4 Hz, 1H), 5.39 (s, 2H), 4.09 (s, 2H), 3.61 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ

:

168.44, 151.57, 132.63, 132.42, 131.94, 130.74, 128.69, 127.74, 127.58, 126.64, 126.45, 125.63, 124.48, 52.46,

48.33, 34.30.

Methyl 2-((5-bromo-4-(quinoline-6-methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7n): White solid; 9.75 g (62%);

◦

m.p. 63–66 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ

: 8.91 (dd, J = 1.6 Hz and 4.4 Hz, 1H), 8.36 (d, J = 8.8 Hz

1H), 8.05 (d, J = 8.8 Hz, 1H), 7.67 (s, 1H), 7.60 (d, J = 2.0 Hz and 8.8 Hz, 1H), 7.53–7.56 (m, 1H), 5.44 (s,

2H), 4.09 (s, 2H), 3.61 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

: 168.45, 151.60, 150.97, 147.18, 135.98,

,

δ

132.65, 130.80, 129.76, 128.08, 127.63, 125.79, 122.00, 52.48, 48.08, 34.39.

Ethyl 2-((4-((5-bromo-4-cyano-1-naphthyl)methyl)-4H-1,2,4-triazol-3-yl)thio)-2-methylpropionate (7o): White

1

foam; 11.94 g (65%). H-NMR (DMSO-d₆, 400 MHz)

δ: 8.38–8.40 (m, 1H), 8.20–8.22 (m, 1H), 8.07 (d,

J = 7.6 Hz, 1H), 7.86–7.94 (m, 2H), 6.50 (d, J = 7.2 Hz, 1H), 5.89 (s, 2H), 4.07 (q, J = 7.2 Hz, 2H), 1.53 (s,

6H), 1.11 (t, J = 7.2 Hz, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ

: 171.82, 149.65, 136.92, 132.91, 132.33,

131.37, 129.46, 129.05, 128.53, 125.12, 124.01, 121.42, 117.15, 109.21, 61.51, 53.89, 46.19, 25.83, 13.66.

Ethyl 1-((5-bromo-4-((4-cyano-1-naphthyl)methyl)-4H-1,2,4-triazol-3-yl)thio)cyclobutanecarboxylate (7p):

White solid; 9.22 g (52%); m.p. 131–133 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.38 (d, J = 7.6 Hz, 1H),

8.20–8.23 (m, 1H), 8.10 (d, J = 7.6 Hz, 1H), 7.86–7.94 (m, 2H), 6.56 (d, J = 7.6 Hz, 1H), 5.87 (s, 2H), 4.06

(q, J = 7.1 Hz, 2H), 2.59–2.66 (m, 2H), 2.24–2.31 (m, 2H), 2.03–2.10 (m, 1H), 1.84–1.91 (m, 1H), 1.10 (t,

J = 7.2 Hz, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 172.06, 150.94, 137.53, 133.61, 132.67, 132.11, 130.19,

129.82, 129.27, 125.85, 124.70, 122.24, 117.87,109.98, 62.15, 55.09, 46.89, 32.58, 16.34, 14.42.

Methyl 2-((5-bromo-1-((4-cyano-1-naphthyl)methyl)-1H-imidazol-2-yl)thio)acetate (7q): White solid; 8.33 g

(50%); m.p. 105–107 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ

: 8.43 (d, J = 8.0 Hz, 1H), 8.21 (d, J = 7.6 Hz,

1H), 8.10 (d, J = 7.6 Hz, 1H), 7.85–7.93 (m, 2H), 7.31 (s, 1H), 6.49 (d, J = 7.6 Hz, 1H), 5.85 (s, 2H), 3.93 (s,

2H), 3.58 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

: 168.83, 141.67, 138.26, 133.01, 131.40, 130.25, 129.39,

δ

129.20, 128.45, 125.11, 124.07, 121.33, 117.32, 108.87, 104.95, 52.34, 46.30, 35.11.

Ethyl 2-((5-bromo-1-((4-cyano-1-na_◦phthyl)methyl)-1H-imidazol-2-yl)thio)-2-methylpropionate (7r): White

solid; 10.08 g (55%); m.p. 125–127 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.43 (d, J = 7.6 Hz, 1H), 8.20 (d,

J = 7.6 H, 1Hz), 8.07 (d, J = 7.6 Hz, 1H), 7.86–7.93 (m, 2H), 7.44 (s, 1H), 6.28 (d, J = 7.6 Hz, 1H), 5.89

(s, 2H), 4.05 (q, J = 7.1 Hz, 2H), 1.47 (s, 6H), 1.10 (t, J = 7.2 Hz, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ:

172.28, 138.97, 138.57, 133.02, 131.33, 131.30, 129.42, 129.01, 128.50, 125.11, 123.97, 121.11, 117.28, 108.85,

106.69, 61.23, 53.31, 46.61, 25.56, 13.69.

Ethyl 1-((5-bromo-1-((4-cyano-1-naphthyl)methyl)-1H-imidazol-2-yl)thio)cyclobutanecarboxylate (7s): White

solid; 9.78 g (52%); m.p. 102–105 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.42 (d, J = 8.0 Hz, 1H), 8.21 (d,

J = 8.0 Hz, 1H), 8.09 (d, J = 7.6 Hz, 1H), 7.86–7.93 (m, 2H), 7.40 (s, 1H), 6.34 (d, J = 7.2 Hz, 1H), 5.87 (s,

2H), 4.04 (q, J = 7.1 Hz, 2H), 2.52–2.57 (m, 2H), 2.21–2.28 (m, 2H), 2.00–2.07 (m, 1H), 1.78–1.84 (m, 1H),

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1.09 (t, J = 7.0 Hz, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 171.92, 139.49, 138.47, 132.99, 131.33, 131.15,

129.42, 129.02, 128.50, 125.11, 123.93, 121.18, 117.27, 108.87, 106.31, 61.14, 54.38, 46.54, 31.39, 15.36, 13.71.

Ethyl 2-((5-bromo-1-((2-thiophenyl)methyl)-1H-imidazol-2-yl)thio)-2-methylpropionate (7w): Oil; 8.72 g (56%).

¹H-NMR (DMSO-d₆, 400 MHz) δ: 7.46–7.47 (m, 1H), 7.24 (s, 1H), δ: 7.007–7.013 (m, 1H), 6.97–6.99 (m,

1H), 5.42 (s, 2H), 4.03 (q, J = 7.2 Hz, 2H), 1.48 (s, 6H), 1.10 (t, J = 7.2 Hz, 3H). ¹³C-NMR (DMSO-d₆,

100 MHz) δ: 172.31, 138.40, 137.84, 130.86, 126.97, 126.71, 126.46, 105.57, 61.15, 53.31, 43.86, 25.47, 13.64.

Ethyl 1-((5-bromo-1-((2-thiophenyl)methyl)-1H-imidazol-2-yl)thio)cyclobutanecarboxylate (7x): Colorless oil;

1

8.51 g (53%). H-NMR (DMSO-d₆, 400 MHz)

δ: 7.48 (dd, J = 0.8 Hz and 5.2 Hz, 1H), 7.20 (s, 1H), 7.03

(d, J = 2.8 Hz, 1H), 6.97–7.00 (m, 1H), 5.40 (s, 2H), 4.05 (q, J = 7.2 Hz, 2H), 2.51–2.59 (m, 2H), 2.24–2.31

(m, 2H), 2.06–2.13 (m, 1H), 1.79–1.87 (m, 1H), 1.10 (t, J = 7.2 Hz, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ:

172.04, 138.40, 138.31, 130.73, 126.99, 126.80, 126.53, 105.17, 61.10, 54.52, 43.77, 31.26, 15.35, 13.71.

Methyl 2-((5-bromo-4-((5-chloro-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7ha): Colorless oil;

1

7.96 g (52%). H-NMR (DMSO-d₆, 400 MHz)

δ: 7.05 (d, J = 3.6 Hz, 1H), 7.00 (d, J = 4.0 Hz, 1H), 5.34 (s,

2H), 4.11 (s, 2H), 3.63 (s, 3H).

Methyl 2-((5-bromo-4-((5-methyl-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7hb): White solid;

8.40 g (58%); m.p. 57–59 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 6.93 (d, J = 3.6 Hz, 1H), 6.69–6.70 (m,

1H), 5.28 (s, 2H), 4.09 (s, 2H), 3.64 (s, 3H), 2.39 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.44, 150.91,

140.83, 133.82, 130.03, 127.97, 125.27, 52.49, 43.68, 34.45, 14.85.

Methyl 2-((5-bromo-4-((5-ethyl-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7hc): Colorless oil;

1

9.03 g (60%). H-NMR (DMSO-d₆, 400 MHz)

δ

: 6.95 (d, J = 3.6 Hz, 1H), 6.73 (d, J = 3.2 Hz, 1H), 5.29

(s, 2H), 4.09 (s, 2H), 3.62 (s, 3H), 2.75 (q, J = 7.5 Hz, 2H), 1.18 (t, J = 7.4 Hz, 3H). ¹³C-NMR (DMSO-d₆,

100 MHz) δ: 168.44, 150.95, 148.35, 133.46, 130.03, 127.86, 123.49, 52.50, 43.75, 34.51, 22.73, 15.60.

Methyl 2-((5-bromo-4-((3-methyl-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7hd): White solid;

◦

9.13 g (63%); m.p. 79–81 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 7.43 (d, J = 5.2 Hz, 1H), 6.88 (d, J = 5.2 Hz,

1H), 5.31 (s, 2H), 4.05 (s, 2H), 3.63 (s, 3H), 2.29 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.41, 151.00,

135.95, 130.20, 125.37, 52.47, 42.50, 34.49, 13.74.

Methyl 2-((4-((5-bromo-4-methyl-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7⁰he) White solid;

8.11 g (56%); m.p. 75–77 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 8.68 (s, 1H), 6.91 (s, 1H), 5.32 (s, 2H),

4.06 (s, 2H), 3.63 (s, 3H), 2.09 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.63, 147.94, 145.33, 137.37,

137.18, 129.84, 108.88, 52.41, 42.30, 34.59, 14.75.

Methyl 2-((5-bromo-4-((3-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7hf): Colorless oil; 6.96 g

(50%); ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 7.57–7.59 (m, 1H), 7.38 (d, J = 1.6 Hz, 1H), 7.01 (dd, J = 1.2 Hz

and 5.2 Hz, 1H), 5.18 (s, 2H), 4.09 (s, 2H), 3.63 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.46, 151.12,

134.99, 130.27, 127.69, 126.47, 123.94, 52.49, 44.08, 34.27.

Methyl 2-((5-bromo-4-((5-_◦phenyl-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7hg): White solid;

9.00 g (53%); m.p. 78–80 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 7.59–7.61 (m, 2H), 7.38–7.41 (m, 3H), 7.31

(t, J = 7.4 Hz, 1H), 7.14 (d, J = 7.6 Hz, 1H), 5.40 (s, 2H), 4.12 (s, 2H), 3.63 (s, 3H). ¹³C-NMR (DMSO-d₆,

100 MHz) : 168.43, 151.03, 144.36, 135.72, 133.05, 130.16, 129.21, 129.12, 127.98, 125.31, 123.49, 52.49,

43.70, 34.49.

δ

Methyl 2-((4-((3-bromobenzo[b]thiophen-2-yl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7⁰hh): White solid;

10.36 g (65%); m.p. 94–96 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

: 8.77 (s, 1H), 8.03 (d, J = 8.0 Hz, 1H),

7.77 (d, J = 7.6 Hz, 1H), 7.47–7.56 (m, 2H), 5.60 (s, 2H), 4.04 (s, 2H), 3.60 (s, 3H). ¹³C-NMR (DMSO-d₆,

100 MHz) : 169.28, 149.14, 146.39, 137.80, 137.74, 134.48, 127.01, 126.55, 123.96, 123.49, 108.30, 53.12,

43.52, 35.41.

δ

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Methyl 2-((5-bromo-4-((dibenzo[b,d]thiophen-4-yl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7hi): White

solid; 9.33 g (52%); m.p. 120–122 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

: 8.37–8.42 (m, 2H), 8.06–8.08

(m, 1H), 7.52–7.57 (m, 3H), 7.12 (d, J = 7.6 Hz, 1H), 5.49 (s, 2H), 4.04 (s, 2H), 3.60 (s, 3H). ¹³C-NMR

(DMSO-d₆, 100 MHz) : 168.39, 151.92, 138.04, 136.17, 135.98, 134.75, 131.25, 128.48, 127.49, 125.30,

δ

125.24, 125.07, 123.00, 122.29, 121.97, 52.47, 47.59, 34.40.

3.2.9. General Procedure for the Synthesis of Brominated Esters 7he and 7hh

To a stirred solution of 7⁰he or 7⁰hh (20 mmol) in MeCN (100 mL) at room temperature was

added NBS (3.56 g, 20 mmol), and the resulting mixture was stirred until completion of the reaction

as indicated by TLC analysis (typically within 12h). The reaction mixture was poured into ice-water

(200 mL), and the resulting mixture was extracted with CH₂Cl₂(200 mL

extracts were washed successively with 5% aqueous Na₂S₂O₃(100 mL), saturated aqueous Na₂CO₃

×

3). The combined

(

100 mL × 5) and 5% brine (100 mL), dried (Na₂SO₄) and evaporated on a rotary evaporator to give a

residue, which was puriﬁed by column chromatography to afford the pure product 7he or 7hh.

Methyl 2-((5-bromo-4-((5-bromo-4-methy_◦l-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7he):

1

White solid; 5.92 g (62%); m.p. 91–93 C. H-NMR (DMSO-d₆, 400 MHz)

δ

: 6.91 (s, 1H), 5.29 (s,

2H), 4.11 (s, 2H), 3.63 (s, 3H), 2.09 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 168.40, 150.98, 137.21,

136.05, 130.12, 129.94, 109.04, 52.49, 43.48, 34.47, 14.73.

Methyl 2-((5-bromo-4-((3-bromobenzo[b]thiophen-2-yl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetate (7hh): White

solid; 5.64 g (66%); m.p. 81–83 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

: 8.03 (d, J = 0.8 Hz, 1H), 7.79 (d,

J = 8.0 Hz, 1H), 7.53–7.57 (m, 1H), 7.47–7.51 (m, 1H), 5.56 (s, 2H), 4.09 (s, 2H), 3.62 (s, 3H). ¹³C-NMR

(DMSO-d₆, 100 MHz) : 168.31, 151.42, 136.97, 136.83, 132.93, 130.58, 126.36, 125.90, 123.24, 122.78,

δ

107.56, 52.48, 44.25, 34.51.

3.2.10. General Procedure for the Synthesis of Acids 8a–8x and 8ha–8hi

To a stirred solution of 6t

temperature was added an aqueous solution of LiOH prepared by dissolving LiOH

10 mmol) in a minimal amount of water, and the resulting mixture was stirred at room temperature

until the reaction completed as indicated by TLC analysis (typically within 5 h). The reaction mixture

–

6v

,

7a

–

7s

,

7w

–

7x or 7ha

–

7hi (5 mmol) in MeOH (20 mL) at room

H₂O (0.42 g,

·

was poured into ice-water (50 mL), and the resulting mixture was acidiﬁed to pH 4-5 (for 6t

-6v, 7f

and 7n) or 1–2 (for others) with concentrated hydrochloric acid before the extraction with CH₂Cl₂

(

50 mL × 3). The combined extracts were washed with water (50 mL), dried (Na₂SO₄) and evaporated

on a rotary evaporator to afford the crude product as a residue, which was puriﬁed by trituration with

EtOAc/n-hexane to yield the pure product 8a–8x or 8ha–8hi.

2-((5-Bromo-4-ethyl-4H-1,2,4-triazol-3-yl)thio)acetic acid (8a): White solid; 0.98 g (78%); m.p. 136–138 ^◦C.

¹H-NMR (DMSO-d₆, 400 MHz) δ: 12.95 (brs, 1H), 3.95 (s, 2H), 3.53 (s, 3H).

2-((5-Bromo-4-n-propyl-4H-1,2,4-triazol-3-yl)thio)acetic acid (8b): White solid; 0.10 g (75%); m.p.

◦

143–145 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ

: 12.94 (brs, 1H), 4.01 (s, 2H), 3.98 (q, J = 7.3 Hz, 2H), 1.25

(t, J = 7.2 Hz, 3H).

2-((5-Bromo-4-(cyclohexylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8c): White solid; 1.17 g (70%); m.p.

155–157 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

: 13.02 (brs, 1H), 4.03 (s, 2H), 3.76 (d, J = 7.6 Hz, 2H),

δ

1.61–1.79 (m, 4H), 1.49–1.52 (m, 2H), 1.11–1.20 (m, 3H), 0.95–1.04 (m, 2H).

2-((4-(1-Adamantylmethyl)-5-bromo-4H-1,2,4-triazol-3-yl)thio)acetic acid (8d): White solid; 1.82 g (94%);

m.p. 169–171 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 12.92 (brs, 1H), 4.00 (s, 2H), 3.66 (s, 2H), 1.95 (s,

3H), 1.63–1.66 (m, 3H), 1.54–1.58 (m, 3H), 1.52–1.53 (m, 6H).

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◦

2-((4-Benzyl-5-bromo-4H-1,2,4-triazol-3-yl)thio)acetic acid (8e): White solid; 2.05 g (78%); m.p. 160–162 C.

¹H-NMR (DMSO-d₆, 400 MHz)

δ: 12.97 (brs, 1H), 7.31–7.40 (m, 3H), 7.16–7.18 (m, 2H), 5.20 (s, 2H),

4.01 (s, 2H).

2-((5-Bromo-4-(3-pyridinylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8f): White solid; 1.25 g (76%);

1

m.p. 173 ^◦C (dec). H-NMR (DMSO-d₆, 400 MHz)

δ: 13.03 (brs, 1H), 8.54 (d, J = 4.0 Hz, 1H), 8.51 (d,

J = 1.6 Hz, 1H), 7.58 (d, J = 8.0 Hz, 1H), 7.39–7.42 (m, 1H), 5.27 (s, 2H), 4.03 (s, 2H).

2-((5-Bromo-4-(2-furanylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8g): White solid; 1.24 g (78%); m.p.

113–116 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 12.97 (brs, 1H), 7.65 (s, 1H), 6.50 (d, J = 3.2 Hz, 1H),

6.45–6.46 (m, 1H), 5.21 (s, 2H), 4.00 (s, 2H).

2-((5-Bromo-4-(2-thiophenylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8h): White solid; 1.40 g (84%);

◦

m.p. 113–115 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 12.98 (brs, 1H), 7.54 (dd, J = 1.2 Hz and 5.2 Hz, 1H),

7.14 (d, J = 3.2 Hz, 1H), 7.01–7.03 (m, 1H), 5.38 (s, 2H), 4.02 (s, 2H).

2-((4-(Biphenyl-4-methyl)-5-bromo-4H-1,2,4-triazol-3-yl)thio)acetic acid (8i): White solid; 1.44 g (71%); m.p.

◦

178–179 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.01 (brs, 1H), 7.64–7.69 (m, 4H), 7.45 (t, J = 7.6 Hz, 2H),

7.36 (t, J = 7.2 Hz, 1H), 7.26 (d, J = 8.4 Hz, 2H), 5.25 (s, 2H), 4.02 (s, 2H).

2-((5-Bromo-4-(diphenylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8j): White solid; 1.48 g (73%); m.p.

134–135 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 12.79 (brs, 1H), 7.32–7.40 (m, 6H), 7.23–7.25 (m, 4H),

6.93 (s, 1H), 3.88 (s, 2H).

2-((4-(Benzo[b]furan-5-methyl)-5-bromo-4H-1,2,4-triazol-3-yl)thio)acetic acid (8k): White solid; 1.51 g (82%);

m.p. 171–173 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

: 12.97 (brs, 1H), 8.01 (d, J = 2.0 Hz, 1H), 7.61 (d,

δ

J = 8.4 Hz, 1H), 7.46 (s, 1H), 7.17–7.20 (m, 1H), 6.96 (d, J = 1.6 Hz, 1H), 5.29 (s, 2H), 4.02 (s, 2H).

2-((5-Bromo-4-((4-cyano-1-naphthyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8l): White solid; 1.61 g

(80%); m.p. 170–172 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 12.93 (brs, 1H), 8.37 (d, J = 7.6 Hz, 1H),

8.20–8.22 (m, 1H), 8.09 (d, J = 7.6 Hz, 1H), 7.85–7.93 (m, 2H), 6.71 (d, J = 7.6 Hz, 1H), 5.87 (s, 2H),

4.01 (s, 2H).

2-((5-Bromo-4-(2-naphthylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8m): White solid; 1.48 g (78%); m.p.

◦

172–174 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 12.97 (brs, 1H), 7.88–7.95 (m, 3H), 7.65 (s, 1H), 7.51–7.55

(m, 2H), 7.35 (dd, J = 1.6 Hz and 7.6 Hz, 1H), 5.38 (s, 2H), 4.03 (s, 2H).

2-((5-Bromo-4-(quinoline-6-methyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8n): White solid; 1.37 g (72%); m.p.

1

203 ^◦C (dec). H-NMR (DMSO-d₆, 400 MHz)

δ

: 12.98 (brs, 1H), 8.90–8.91 (m, 1H), 8.35 (d, J = 8.0 Hz

,

1H), 8.04 (d, J = 8.4 Hz, 1H), 7.69 (s, 1H), 7.60–7.63 (m, 1H), 7.54 (dd, J = 4.0 Hz and 8.4 Hz, 1H), 5.43 (s,

2H), 4.03 (s, 2H).

2-((4-((5-Bromo-4-cyano-1-naphthyl)methyl)-4H-1,2,4-triazol-3-yl)thio)-2-methylpropionic acid (8o): White

◦

1

solid; 1.47 g (68%); m.p. 168–170 C. H-NMR (DMSO-d₆, 400 MHz) δ: 13.16 (brs, 1H), 8.35 (d,

J = 7.6 Hz, 1H), 8.20–8.22 (m, 1H), 8.07 (d, J = 7.6 Hz, 1H), 7.86–7.94 (m, 2H), 6.53 (d, J = 7.6 Hz, 1H),

5.89 (s, 2H), 1.51 (s, 6H).

1-((5-Bromo-4-((4-cyano-1-naphthyl)methyl)-4H-1,2,4-triazol-3-yl)thio)cyclobutanecarboxylic acid (8p): White

◦

1

solid; 1.44 g (65%); m.p. 173–175 C. H-NMR (DMSO-d₆, 400 MHz) δ: 13.08 (brs, 1H), 8.34 (d,

J = 8.0 Hz, 1H), 8.21 (d, J = 7.6 Hz, 1H), 8.08 (d, J = 7.6 Hz, 1H), 7.86–7.94 (m, 2H), 6.60 (d, J = 7.6 Hz,

1H), 5.86 (s, 2H), 2.57–2.65 (m, 2H), 2.24–2.31 (m, 2H), 1.99–2.07 (m, 1H), 1.86–1.92 (m, 1H).

2-((5-Bromo-1-((4-cyano-1-naphthyl)methyl)-1H-imidazol-2-yl)thio)acetic acid (8q): White solid; 1.45 g (72%);

m.p. 180–182 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 12.84 (brs, 1H), 8.42 (d, J = 8.4 Hz, 1H), 8.20 (d,

J = 7.6 Hz, 1H), 8.09 (d, J = 7.6 Hz, 1H), 7.85–7.93 (m, 2H), 7.30 (s, 1H), 6.51 (d, J = 7.6 Hz, 1H), 5.85 (s,

2H), 3.86 (s, 2H).

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2-((5-Bromo-1-((4-cyano-1-naphthyl)methyl)-1H-imidazol-2-yl)thio)-2-methylpropionic acid (8r): White solid;

1.61 g (75%); m.p. 193–195 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

: 12.96 (brs, 1H), 8.39 (d, J = 7.6 Hz,

δ

1H), 8.19–8.22 (m, 1H), 8.07 (d, J = 7.6 Hz, 1H), 7.86–7.93 (m, 2H), 7.43 (s, 1H), 6.33 (d, J = 7.6 Hz, 1H),

5.90 (s, 2H), 1.44 (s, 6H).

1-((5-Bromo-1-((4-cyano-1-naphthyl)methyl)-1H-imidazol-2-yl)thio)cyclobutanecarboxylic acid (8s): White

◦

1

solid; 1.50 g (68%); m.p. 210–213 C. H-NMR (DMSO-d₆, 400 MHz) δ: 12.96 (brs, 1H), 8.38 (d,

J = 8.0 Hz, 1H), 8.21 (d, J = 8.4 Hz, 1H), 8.08 (d, J = 7.6 Hz, 1H), 7.85–7.93 (m, 2H), 7.40 (s, 1H), 6.39 (d,

J = 7.6 Hz, 1H), 5.88 (s, 2H), 2.53–2.56 (m, 2H), 2.19–2.26 (m, 2H), 1.95–2.02 (m, 1H), 1.79–1.85 (m, 1H).

2-((3-((4-Cyano-1-naphthyl)methyl)pyridin-4-yl)thio)acetic acid (8t): White solid; 1.30 g (78%); m.p.

◦

1

246–249 C. H-NMR (DMSO-d₆, 400 MHz) δ: 13.10 (brs, 1H), 8.38 (d, J = 5.2 Hz, 1H), 8.28 (d,

J = 8.4 Hz, 1H), 8.17 (d, J = 8.0 Hz, 1H), 8.11 (s, 1H), 8.07 (d, J = 7.6 Hz, 1H), 7.84 (t, J = 7.4 Hz, 1H), 7.76

(t, J = 7.8 Hz, 1H), 7.36 (d, J = 5.2 Hz, 1H), 7.17 (d, J = 7.6 Hz, 1H), 4.56 (s, 2H), 4.01 (s, 2H).

2-((3-((4-Cyano-1-naphthyl)methyl)pyridin-4-yl)thio)-2-methylpropionic acid (8u) White soli; 1.30 g (72%);

m.p. 175–177 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.11 (brs, 1H), 8.43 (d, J = 5.2 Hz, 1H), 8.26 (d, J =

8.4 Hz, 1H), 8.24 (s, 1H), 8.17 (d, J = 8.4 Hz, 1H), 8.06 (d, J = 7.2 Hz, 1H), 7.83 (t, J = 7.6 Hz, 1H), 7.77 (t,

J = 7.6 Hz, 1H), 7.43 (d, J = 5.2 Hz, 1H), 7.09 (d, J = 7.2 Hz, 1H), 4.64 (s, 2H), 1.50 (s, 6H).

1-((3-((4-Cyano-1-naphthyl)methyl)pyridin-4-yl)thio)cyclobutanecarboxylic acid (8v): White solid; 1.22 g

(65%); m.p. 210–212 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 13.10 (brs, 1H), 8.34 (d, J = 5.6 Hz, 1H), 8.26

(d, J = 8.4 Hz, 1H), 8.17 (d, J = 8.4 Hz, 1H), 8.10 (s, 1H), 8.08 (d, J = 7.6 Hz, 1H), 7.84 (t, J = 7.4 Hz, 1H),

7.76 (t, J = 7.6 Hz, 1H), 7.17 (d, J = 7.6 Hz, 1H), 7.11 (d, J = 5.6 Hz, 1H), 4.54 (s, 2H), 2.78–2.86 (m, 2H),

2.18–2.25 (m, 2H), 2.07–2.16 (m, 1H), 1.92–2.00 (m, 1H).

2-((5-Bromo-1-((2-thiophenyl)methyl)-1H-imidazol-2-yl)thio)-2-methylpropionic acid (8w): White solid; 1.48

g (82%); m.p. 153–155 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 12.92 (brs, 1H), 7.46–7.47 (m, 1H), 7.22 (s,

1H), 7.03 (d, J = 3.2 Hz, 1H), 6.97–6.99 (m, 1H), 5.44 (s, 2H), 1.44 (s, 6H).

1-((5-Bromo-1-((2-thiophenyl)methyl)-1H-imidazol-2-yl)thio)cyclobutanecarboxylic acid (8x): White solid;

1.40 g (75%); m.p. 164–166 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 12.96 (brs, 1H), 7.47–7.48 (m, 1H),

7.20 (s, 1H), 7.05 (d, J = 7.2 Hz, 1H), 6.99 (dd, J = 3.6 Hz and 4.8 Hz, 1H), 5.42 (s, 2H), 2.51–2.56 (m, 2H),

2.20–2.27 (m, 2H), 1.98–2.06 (m, 1H), 1.80–1.86 (m, 1H).

2-((5-Bromo-4-((5-chloro-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8ha): White solid; 1.25 g

(68%); m.p. 142–143 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

(d, J = 4.0 Hz, 1H), 5.33 (s, 2H), 4.03 (s, 2H).

δ: 12.95 (brs, 1H), 7.05 (d, J = 4.0 Hz, 1H), 7.01

2-((5-Bromo-4-((5-methyl-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8hb): White solid;

1.31 g (75%); m.p. 119–120 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 12.98 (brs, 1H), 6.93 (d, J = 3.2 Hz,

1H), 6.69–6.70 (m, 1H), 5.28 (s, 2H), 4.01 (s, 2H), 2.38 (s, 3H).

2-((5-Bromo-4-((5-ethyl-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8hc): White solid; 1.41 g

(78%); m.p. 119–120.5 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

: 12.98 (brs, 1H), 6.95 (d, J = 3.6 Hz, 1H),

δ

6.73 (d, J = 7.2 Hz, 1H), 5.29 (s, 2H), 4.02 (s, 2H), 2.75 (q, J = 7.5 Hz, 2H), 1.18 (t, J = 7.4 Hz, 3H).

2-((5-Bromo-4-((3-methyl-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8hd): White solid;

1.45 g (83%); m.p. 111–112 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 12.97 (brs, 1H), 7.42 (d, J = 4.8 Hz,

1H), 6.88 (d, J = 5.2 Hz, 1H), 5.30 (s, 2H), 3.98 (s, 2H), 2.29 (s, 3H).

2-((5-Bromo-4-((5-bromo-4-methyl_◦-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8he): White

solid; 1.82 g (85%); m.p. 144–145 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 12.99 (brs, 1H), 6.92 (s, 1H), 5.29

(s, 2H), 4.03 (s, 2H), 2.09 (s, 3H).

Molecules 2018, 23, 252

30 of 38

2-((5-Bromo-4-((3-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8hf): White solid; 1.27 g (76%);

◦

m.p. 124–126 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 12.96 (brs, 1H), 7.56–7.58 (m, 1H), 7.39 (d, J = 2.0 Hz,

1H), 7.03 (dd, J = 0.8 Hz and 5.2 Hz, 1H), 5.17 (s, 2H), 4.01 (s, 2H).

2-((5-Bromo-4-((5-phenyl-2-thiophenyl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8hg): White solid;

◦

1

1.48 g (72%); m.p. 126–128 C. H-NMR (DMSO-d₆, 400 MHz) δ: 13.02 (brs, 1H), 7.59–7.61 (m,

2H), 7.38–7.41 (m, 3H), 7.31 (t, J = 7.2 Hz, 1H), 7.15 (d, J = 3.6 Hz, 1H), 5.39 (s, 2H), 4.04 (s, 2H).

2-((5-Bromo-4-((3-bromobenzo[b]thiop_◦hen-2-yl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8hh): White

1

solid; 1.81 g (78%); m.p. 153–155 C. H-NMR (DMSO-d₆, 400 MHz)

δ: 12.98 (brs, 1H), 8.03 (d,

J = 8.0 Hz, 1H), 7.79 (d, J = 7.6 Hz, 1H), 7.53–7.57 (m, 1H), 7.47–7.51 (m, 1H), 5.55 (s, 2H), 4.02 (s, 2H).

2-((5-Bromo-4-((dibenzo[b,d]thiophen-4-yl)methyl)-4H-1,2,4-triazol-3-yl)thio)acetic acid (8hi): White solid;

◦

1.59 g (73%); m.p. 157 C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 12.94 (brs, 1H), 8.37–8.42 (m, 2H), 8.06–8.08

(m, 1H), 7.52–7.57 (m, 3H), 7.13 (d, J = 7.2 Hz, 1H), 5.48 (s, 2H), 3.98 (s, 2H).

3.2.11. General Procedure for the Synthesis of Sodium Salts 1a–1x and 1ha–1hi

To a stirred mixture of 8a–8x or 8ha–8hi (accurately weighted to four decimal places, 2 mmol) in

MeOH (10 mL) was added an aqueous solution of NaOH prepared by dissolving NaOH (0.0800 g,

2 mmol) in a minimal amount of water, and the resulting mixture was stirred at room temperature

until a clear solution was obtained (typically within 1 h). The reaction mixture was ﬁltered off and

the ﬁltrate was evaporated on a rotary evaporator to afford a residue, which was co-evaporated with

CH₂Cl₂(10 mL

the pure product 1a–1x or 1ha–1hi.

×

3) on a rotary evaporator and further dried in vacuo at room temperature to yield

Sodium 2-((5-bromo-4-ethyl-4H-1,2,4-triazol-3-yl)thio)acetate (1a): White solid; 0.55 g (100%); m.p. 203 ^◦C

(dec). ¹H-NMR (DMSO-d₆, 400 MHz) : 3.62 (s, 2H), 3.50 (s, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ

: 169.38, 153.59, 129.80, 40.08, 31.71. ESI-HRMS [M

−

Na]^–: (m/z) calcd. for C₅H₅BrN₃O₂S:

249.9291 (⁷⁹Br), found: 249.9289; calcd. for C₅H₅BrN₃O₂S: 251.9271 (⁸¹Br), found: 251.9263. HPLC

purity: 97.78%.

Sodium 2_◦-((5-bromo-4-n-propyl-4H-1,2,4-triazol-3-yl)thio)acetate (1b): White solid; 0.58 g (100%); m.p.

106–108 C (dec). ¹H-NMR (DMSO-d₆, 400 MHz)

δ: 3.94 (q, J = 7.2 Hz, 2H), 3.66 (s, 2H), 1.23 (t,

J = 7.2 Hz, 3H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ: 169.46, 153.07, 128.63, 40.29, 40.03, 14.47. ESI-HRMS

[M

−

Na]^–: (m/z) calcd. for C₆H₇BrN₃O₂S: 263.9448 (⁷⁹Br), found: 263.9446; calcd. for C₆H₇BrN₃O₂S:

265.9427 (⁸¹Br), found: 265.9425. HPLC purity: 99.02%.

Sodium 2-((5-bromo-4-(cyclohexylmethyl)-4H-1,2,4-triazol-3-yl)thio)acetate (1c): White solid; 0.71 g (99%);

1

m.p. 135 ^◦C (dec). H-NMR (DMSO-d₆, 400 MHz)

δ

: 3.73 (d, J = 7.2 Hz, 2H), 3.68 (s, 2H), 1.61–1.77

(m, 4H), 1.48–1.51 (m, 2H), 1.13–1.17 (m, 3H), 0.98–1.03 (m, 2H). ¹³C-NMR (DMSO-d₆, 100 MHz)

δ:

169.41, 153.91, 129.38, 50.62, 40.10, 37.35, 29.88, 25.61, 25.04. ESI-HRMS [M

C₁₁H₁₅BrN₃O₂S: 332.0074 (⁷⁹Br), found: 332.0241; calcd. for C₁₁H₁₅BrN₃O₂S: 334.0053 (⁸¹Br), found:

334.0238. HPLC purity: 98.27%.

−

Na]^–: (m/z) calcd. for

Sodium 2-((4-(1-adamantylmethyl)-5-bromo-4H-1,2,4-triazol-3-yl)thio)acetate (1d): White solid; 0.82 g

◦

(100%); m.p. 194 C (dec). ¹H-NMR (DMSO-d₆, 400 MHz)

δ

: 3.63 (s, 2H), 1.95 (s, 3H), 1.62–1.65

(m, 3H), 1.53–1.58 (m, 9H). ¹³C-NMR (DMSO-d₆, 100 MHz)

35.94, 35.46, 27.53. ESI-HRMS [M

384.0393; calcd. for C₁₅H₁₉BrN₃O₂S: 386.0366 (⁸¹Br), found: 386.0375. HPLC purity: 98.41%.

δ: 169.35, 155.05, 130.34, 56.18, 40.65, 40.36,

−

Na]^–: (m/z) calcd. for C₁₅H₁₉BrN₃O₂S: 384.0387 (⁷⁹Br), found:

Sodium 2-((4-benzyl-5-bromo-4H-1,2,4-triazol-3-yl)thio)acetate (1e): White solid; 0.70 g (100%); m.p.

119–121 ^◦C. ¹H-NMR (DMSO-d₆, 400 MHz)

δ

: 7.35–7.39 (m, 2H), 7.32 (d, J = 7.2 Hz, 1H), 7.13–7.15 (m,

2H), 5.17 (s, 2H), 3.60 (s, 2H). ¹³C-NMR (DMSO-d₆, 100 MHz)

: 168.26, 154.27, 134.87, 129.42, 128.81,

127.94, 126.71, 47.87, 40.61. ESI-HRMS [M

Na]^–: (m/z) calcd. for C₁₁H₉BrN₃O₂S: 325.9604 (⁷⁹Br),

found: 325.9591; calcd. for C₁₁H₉BrN₃O₂S: 327.9584 (⁸¹Br), found: 327.9574. HPLC purity: 99.14%.

δ

−

Article Doi

Systematic structure-activity relationship (SAR) exploration of diarylmethane backbone and discovery of a highly potent novel uric acid transporter 1 (URAT1) inhibitor

DOI: 10.3390/molecules23020252

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Article abstract of DOI:10.3390/molecules23020252

Full text of DOI:10.3390/molecules23020252

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