Complete sequential functionalization of monopyrrolotetrathiafulvalenes

DOI: 10.1055/s-2005-861879

Source and publish data:

Synthesis p. 1251 - 1260 (2005)

Update date:2022-08-05

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Authors:

Gopee, Hemant

Nielsen, Kent A.

Jeppesen, Jan O.

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Article abstract of DOI:10.1055/s-2005-861879

Introduction of aldehyde and ketone functional groups into the α-positions of monopyrrolotetrathiafulvalene provides a novel method for a stepwise and selective penta-functionalization of monopyrrolotetrathiafulvalene derivatives. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2005-861879

PAPER

1251

Complete Sequential Functionalization of Monopyrrolotetrathiafulvalenes

omplete Sequent

ial

unction

alization of

onop

yrrolotetrat

nhiafulvalenest Gopee, Kent A. Nielsen, Jan O. Jeppesen*

Department of Chemistry, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark

Fax +4566158780; E-mail: joj@chem.sdu.dk

Received 16 December 2004

On account of effective N- and S-alkylations, it is possible

to functionalize (Figure 2a) the MPTTF unit in the 5-,

4¢-, and 5¢-positions and several cyclophanes,¹²cage mol-

ecules,¹³and amphiphilic bistable [2]rotaxanes¹⁴have

been prepared from MPTTF building blocks. However,

the potential for functionalizing the MPTTF unit in its 4-

and 6-position (Figure 2b) has only very recently been

pursued¹⁵and has mainly been conducted under strongly

basic conditions¹⁶using LDA rendering this method less

convenient for the preparation of systems containing

functional groups sensitive to strong base. Although the

progress in molecular, macromolecular, and supramolec-

ular TTF chemistry has been revolutionized by an ongo-

ing development of new TTF building blocks there is still

a quest for further developments allowing new and even

more complicated TTF systems to be prepared under mild

conditions.

Abstract: Introduction of aldehyde and ketone functional groups

into the a-positions of monopyrrolotetrathiafulvalene provides a

novel method for a stepwise and selective penta-functionalization

of monopyrrolotetrathiafulvalene derivatives.

Key words: aldehyde, functionalization, ketone, pyrrole, tetrathia-

fulvalene

Tetrathiafulvalene¹(TTF, 1, Figure 1) is a well estab-

lished molecule whose interest goes beyond the field of

materials chemistry. Its derivatives were originally pre-

pared as strong electron-donor molecules for the develop-

ment of electrically conducting materials.^2,3In the last

decades, large synthetic efforts have been devoted to the

preparation of molecular, macromolecular,⁴and

supramolecular⁵systems based on TTF and its deriva-

tives. The ongoing quest for these materials has promoted

much research in the development of new TTF building

R¹S

R³

2' 2

R²S

Figure 1 Molecular formulae of TTF 1 and MPTTF 2

Figure 2 Different types of functionalization of MPTTF derivati-

ves, a) in the 5-, 4¢-, and 5¢-positions and b) in the 4- and 6-positions

blocks which are nowadays used in systems such as cyclo-

phanes,⁶chemical sensors,⁷catalysts,⁸switches,⁹and

electronic devices.¹⁰Thus, one of the most successful

modifications has been the annelation of a pyrrole ring di-

rectly onto the TTF skeleton affording (Figure 1) the

monopyrrolo[3,4-d]tetrathiafulvalenes (MPTTF) 2. De-

rivatives of MPTTF, such as 3 (Scheme 1) carrying cya-

noethyl thiolate and tosyl protecting groups, have proven

to be some of the most useful building blocks in TTF

chemistry.¹¹

Here, we report such an accomplishment by describing a

synthetic method that allows the MPTTF building block 3

to be functionalized sequentially in all of its five possible

attachments sites under mild conditions in a chronological

manner as shown in Scheme 1. Firstly, the MPTTF build-

ing block can be functionalized in two separate steps at

position I and II, followed by functionalization at position

III. Finally, the two a-positions, i.e., positions IV and V,

on the pyrrole ring can be functionalized in a stepwise

manner by the introduction of either dithioacetal or

dithioketal substituents which act as masked aldehyde or

ketone functional groups, respectively. Introduction of

such reactive handles in the IV- and V-positions creates

not only novel MPTTF derivatives, but also potentially

useful building blocks on account of the vide range of

chemical reactions – such as oxidation and reduction reac-

tions,¹⁷Wittig reactions,¹⁸and imine¹⁹formation to men-

tion just a few examples – which can be carried out on

aldehyde and ketone functionalities.

N III

N Ts

Scheme 1 Sequential functionalization of the MPTTF building

block 3

SYNTHESIS 2005, No. 8, pp 1251–1260

Generally, carbonyl functional groups can be introduced

into the a-position of pyrrole derivatives in a single syn-

Advanced online publication: 17.03.2005

DOI: 10.1055/s-2005-861879; Art ID: P15004SS

1252

H. Gopee et al.

PAPER

thetic step by reactions such as the Vilsmeier formyla- functionalization of the MPTTF unit to the bis-aldehyde/

tion.²⁰Unfortunately, these types of reactions only allow ketone 12 can be achieved (Scheme 2) in three separate

one carbonyl group to be introduced because of the strong steps. Firstly, a bisthioacetal/bisthioketal group can be in-

deactivating effect of carbonyl groups toward subsequent troduced by treatment of 7 with the benzodithiol-2-ylium

electrophilic aromatic substitution reactions. However, tetrafluoroborate salt 8 carrying R⁴. Secondly, another

bisacylated pyrrole derivatives can be accessed by a syn- bisthioacetal/bisthioketal group can be introduced by

thetic approach reported²¹by Barbero and co-workers in treatment of 9 with the benzodithiol-2-ylium tetrafluoro-

the early 1990’s. In a two step synthetic procedure a,a¢- borate salt 10 carrying R⁵affording the MPTTF derivative

bisacylation can be carried out by 1) treatment of pyrrole 11. Finally, the two bisthioacetal/bisthioketal protecting

derivatives with benzodithiol-2-ylium tetrafluoroborate groups in 11 can be removed using mercury(II) acetate

salts; followed by 2) deprotection of the resulting dithio- giving the pentafunctionalized MPTTF derivative 12.

acetals or dithioketals affording the bisacylated pyrrole

In principle two different alkyl groups (R¹and R²) can be

derivatives. By combining this method with the well es-

introduced (Scheme 1) into position I and II by deprotec-

tablished N- and S-alkylations of MPTTF derivatives, we

tion of the two cyanoethyl thiolate protecting group fol-

have devised a synthetic protocol for sequential function-

alization of the MPTTF building block 3 at all of its five

possible attachments sites as outlined in Scheme 2. Treat-

ment of 3 with one equivalent of cesium hydroxide gener-

lowed by realkylation of the resulting thiolates. However,

for simplicity we have chosen to alkylate these two posi-

tions with identical alkylating reagents as shown in

Scheme 3. In this paper, pentyl bromide (C₅H₁₁Br) was

ates the MPTTF-monothiolate selectively, without

used as the alkylating reagent which could be coupled

interfering with the tosyl protecting group. This MPTTF-

with the MPTTF building block 3, following its in situ

(THF/MeOH) deprotection with one equivalent of cesium

hydroxide monohydrate (CsOH·H₂O) to give 13 in 79%

yield. Subsequently, the remaining cyanoethyl protecting

monothiolate can thereafter be alkylated with an alkylat-

ing reagent (R¹X) affording the alkylthio-MPTTF deriva-

tive 4. Subsequently, the remaining cyanoethyl thiolate

protecting group in 4 can be deprotected using another

group in 13 was deprotected using one equivalent of

equivalent of cesium hydroxide and the resulting thiolate

CsOH·H₂O followed by addition of C₅H₁₁Br, which ef-

can be alkylated by addition of a second alkylating re-

fected the second deprotection/alkylation sequence, af-

agent (R²X), giving the dialkylated MPTTF derivative 5.

fording 14 in 82% yield. Deprotection of the tosyl group

The tosyl protecting group on the MPTTF unit can be re-

was carried out in near quantitative yield by stirring 14 at

50 °C in a 1:1 mixture of THF–MeOH in the presence of

an excess of sodium methoxide. Introduction of the alkyl

(methyl and propyl) groups onto the pyrrole nitrogen of

moved by using sodium methoxide and the resultant pyr-

role nitrogen in 6 can be alkylated with a third alkylating

reagent (R³X) providing the MPTTF derivative 7. Further

1. CsOH

2. R²X

1. CsOH

2. R¹X

R¹S

R²S

N Ts

R⁴

BF₄

R¹S

R²S

R¹S

NaH / R³X

R¹S

NaOMe

R³

R²S

R⁴

R⁵

R¹S

R²S

Hg(OAc)₂

R¹S

R²S

BF₄

R³

R⁵

Scheme 2 Complete reaction sequence

Synthesis 2005, No. 8, 1251–1260 © Thieme Stuttgart · New York

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Complete Sequential Functionalization of Monopyrrolotetrathiafulvalenes

1253

1. CsOH⋅H₂O / MeOH

2. C₅H₁₁Br / THF / r.t.

1. CsOH⋅H₂O / MeOH

2. C₅H₁₁Br / THF / r.t.

C₅H₁₁

N Ts

82%

79%

MeI or C₃H₇Br / DMF

NaH / 0 °C / 1 h

NaOMe / THF–MeOH

C₅H₁₁

50 °C / 1 h

N R³

N Ts

N H

C₅H₁₁

98%

C₅H₁₁

16 : R³= CH₃, 96%

17 : R³= C₃H₇, 93%

Scheme 3 Synthesis of MPTTF derivatives

the TTF derivative 15 was easily carried out (Scheme 3) would show similar reactivity with 21 and 23 under the

at 0 °C by deprotonation with sodium hydride followed by conditions described above. In the case of 21 the product

reaction with either methyl iodide or propyl bromide.²²29 was easily formed at room temperature in good yields.

Both products 16 and 17 were easily purified and obtained However, when identical conditions were applied on 23,

in high yields of 96% and 93%, respectively.

only a small amount of product 31 was obtained as indi-

cated by TLC analysis. Consequently, a larger amount of

2-phenyl-1,3-benzodithiol-2-ylium tetrafluoroborate (19)

(up to 5 equiv) was added and a good yield was obtained

only after heating the mixture under reflux for 10 hours.

Compounds 28 to 31 were obtained in moderate to good

yields (60–80%).

Functionalization of the MPTTF derivatives 16 and 17 at

the 4-position could be achieved selectively (Scheme 4)

by controlling the reaction conditions. Treatment of 16

with one equivalent of 1,3-benzodithiol-2-ylium tetra-

fluoroborate (18) in acetonitrile and pyridine as base gave

the dithioacetal 20 in 53% yield; the reaction was com-

pleted within one hour. Similarly, the reaction of 16 with In the second strategy (Scheme 4, Method A), bis-func-

one equivalent of 2-phenyl-1,3-benzodithiol-2-ylium tionalization of the MPTTF derivatives 16 and 17 directly

tetrafluoroborate²¹(19) under identical conditions gave at the 4- and 6-positions was carried out in a one-pot reac-

the dithioketal 21 in a 65% yield. In both cases, electro- tion. Thus, compounds 16 and 17 were reacted with 1,3-

philic aromatic substitution took place at both the 4- and benzodithiol-2-ylium tetrafluoroborate (18) at room tem-

6-positions thus reducing the yield of the desired prod- perature and afforded the products 28 and 30, respective-

ucts. It should also be noted that under these conditions, ly. Also, the reaction of 16 with excess 2-phenyl-1,3-

the reaction did not go to completion and consequently a benzodithiol-2-ylium tetrafluoroborate (19) proceeded

small amount of starting material was isolated during pu- smoothly and product 29 was obtained in a reasonable

rification. Similar reactions were carried out on the N-pro- yield. However, harsher conditions (5 equiv of 19 and

pyl derivative 17 and the products 22 and 23 were 10 h of heating under reflux) had to be used when 17 was

obtained in good yields of 61% and 75%, respectively.

reacted with 2-phenyl-1,3-benzodithiol-2-ylium tetrafluo-

roborate (19) to obtain 31. The difference can most likely

be attributed to steric hindrance. All products were ob-

tained in reasonable yields (48–74%).

Deprotection of the dithioacetals (20 and 22) and

dithioketals (21 and 23) into their corresponding alde-

hydes (24 and 26) and ketones (25 and 27) were achieved

(Scheme 4) by using mercury(II) acetate in DMSO at Finally, deprotection (Scheme 4) of the bisdithioacetals

100 °C. All the reactions took place within 2 hours and the 28 and 30 and bisdithioketals 29 and 31 into their respec-

products were obtained in good yields (69–78%).

tive aldehydes (32 and 34) and ketones (33 and 35) were

carried out by using mercury(II) acetate in DMSO at

100 °C. The reactions took place within two hours and all

products were obtained in good yields (72–78%).

The syntheses of the dialdehydes (32 and 34) and dike-

tones (33 and 35), i.e., functionalization at both the 4- and

6-positions, were carried out in two alternative ways. The

first strategy (Scheme 4, Method B) employed the In conclusion, we have successfully developed a synthetic

MPTTF derivatives (20–23) as starting material and an method that allows the MPTTF building block 3 to be

excess of the respective salts (18 and 19) with either stir- functionalized sequentially in all of its five possible posi-

ring at room temperature or by stirring under reflux. Thus tions under mild conditions. The synthetic routes allow

20 was reacted with 2.5 equivalents of 1,3-benzodithiol-2- selective introduction of either one or two aldehyde or ke-

ylium tetrafluoroborate (18) in acetonitrile to yield the tone functional groups on the MPTTF unit depending on

bis-dithioacetal 28. The propyl analogue 22 reacted under the reaction conditions used. It can therefore be extrapo-

similar conditions to give 30. It was envisaged that 2-phe- lated that five totally different groups can be introduced

nyl-1,3-benzodithiol-2-ylium tetrafluoroborate (19) using this sequence of reactions, a finding which undeni-

Synthesis 2005, No. 8, 1251–1260 © Thieme Stuttgart · New York

1254

H. Gopee et al.

PAPER

1 equiv

R⁴

BF₄

R⁴

Hg(OAc)₂/ Me₂SO

100 °C / 2 h

pyridine / MeCN

r.t. / 1 h

C₅H₁₁

R³

18 : R⁴= H

19 : R⁴= Ph

C₅H₁₁

16 : R³= CH₃

17 : R³= C₃H₇

24 : R³= CH₃R⁴= H, 73%

25 : R³= CH₃R⁴= C₆H₅, 69%g

26 : R³= C₃H₇R⁴= H, 70%

27 : R³= C₃H₇R⁴= C₆H₅, 70%

20 : R³= CH₃R⁴= H, 53%

21 : R³= CH₃R⁴= C₆H₅, 65%

22 : R³= C₃H₇R⁴= H, 61%

23 : R³= C₃H₇R⁴= C₆H₅, 75%

Method A

Method B

2.5 to 5 equiv

R⁴

2.5 to 5 equiv

BF₄

18 : R⁴= H

19 : R⁴= Ph

R⁴

BF₄

pyridine / MeCN

r.t. / 1 h

18 : R⁴= H

19 : R⁴= Ph

R⁴

Hg(OAc)₂/ Me₂SO

100 °C / 2 h

C₅H₁₁

R³

C₅H₁₁

R⁴

32 : R³= CH₃R⁴= H, 72%

33 : R³= CH₃R⁴= C₆H₅, 75%

34 : R³= C₃H₇R⁴= H, 72%

35 : R³= C₃H₇R⁴= C₆H₅, 78%

28 : R³= CH₃R⁴= H, Method A: 49%, Method B: 80%

29 : R³= CH₃R⁴= C₆H₅, Method A: 45%, Method B: 68%

30 : R³= C₃H₇R⁴= H, Method A: 55%, Method B: 60%

31 : R³= C₃H₇R⁴= C₆H₅, Method A: 74%, Method B: 78%

Scheme 4 Synthesis of acylated MPTTF derivatives

2-[4-(2-Cyanoethylthio)-5-pentylthio-1,3-dithiole-2-yliden]-5-

tosyl-(1,3)-dithiolo[4,5-c]pyrrole (13)

ably is important for the future development of molecular

and supramolecular systems based on TTF.

A solution of compound 3 (0.28 g, 0.50 mmol) in anhyd THF (40

mL) was degassed (N₂, 10 min) and a solution of CsOH·H₂O

(88 mg, 0.53 mmol) in anhyd MeOH (1 mL) was added dropwise

over a period of 1 h. The mixture was stirred for 15 min and C₅H₁₁Br

(91 mg, 0.074 mL, 0.60 mmol) was added in one portion. The reac-

tion mixture was stirred for a further 5 h. The solvent was evaporat-

ed and the resulting yellow residue was dissolved in CH₂Cl₂

(100 mL), washed with H₂O (3 × 50 mL) and dried (MgSO₄). Evap-

oration of the solvent gave a yellow solid, which was purified by

column chromatography (250 mL SiO₂, ∆ = 6 cm; CH₂Cl₂–cyclo-

hexane, 9:1) to give the title compound 13 as a yellow powder;

yield: 0.23 g (79%); mp 105–109 °C.

¹H NMR (CDCl₃/TMS): d = 0.90 (t, 3 H, J = 7.0 Hz), 1.25–1.45 (m,

4 H), 1.57–1.70 (m, 2 H), 2.41 (s, 3 H), 2.67 (t, 2 H, J = 7.3 Hz),

2.85 (t, 2 H, J = 7.4 Hz), 3.01 (t, 2 H, J = 7.3 Hz), 6.94 (s, 2 H), 7.30

(d, 2 H, J = 8.2 Hz), 7.73 (d, 2 H, J = 8.2 Hz).

¹³C NMR (CDCl₃/TMS): d = 13.9, 18.6, 21.6, 22.1, 29.4, 30.5, 31.2,

36.3, 111.2, 111.3, 113.5, 117.4, 118.3, 121.5, 126.8 (two overlap-

ping peaks), 126.9, 130.1, 133.4, 135.2, 145.5.

All reactions were carried out under an anhyd argon atmosphere in

an oven dried round bottomed flask. Chemicals were purchased

from commercial sources and were used as received except com-

pounds 3²²and 19²¹which were prepared according to literature

procedures. Solvents were dried according to literature proce-

dures.²³TLC was carried out using aluminium sheets pre-coated

with silica gel 60 F₂₅₄(Merck 5554). The plates were inspected un-

der UV light (254 nm) and, if required, developed in I₂vapor. Col-

umn chromatography was carried out using silica gel 60F (Merck

9385, 0.040–0.063 mm). Melting points were determined on a Bü-

chi melting point apparatus and are uncorrected. H NMR (300

MHz) and ¹³C NMR (75 MHz) spectra were recorded on a Gemini-

300BB instrument, using TMS or the residual solvent as the internal

standard which were assigned on the basis of Nudelman.²⁴Fourier

transform matrix-assisted laser-desorption/ionization mass spec-

trometry (FT–MALDI–MS) was performed on an IonSpec 4.7 tesla

Ultima Fourier Transform mass spectrometer, utilizing a 2,5-dihy-

droxybenzoic acid (DHB) matrix. Microanalyses were performed

by the Atlantic Microlab, Inc., Atlanta, Georgia, USA.

FT-MALDI-MS: m/z (%) = 583 (M⁺, 90).

Synthesis 2005, No. 8, 1251–1260 © Thieme Stuttgart · New York

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Complete Sequential Functionalization of Monopyrrolotetrathiafulvalenes

1255

FT-MALDI-HRMS: m/z calcd for M⁺, 583.9883; found, 583.9880.

Anal. Calcd for C₁₉H₂₇NS₆(461.8): C, 49.42; H, 5.89; N, 3.03; S,

41.66. Found: C, 49.55; H, 5.92; N, 3.03; S, 41.80.

Anal. Calcd for C₂₃H₂₄N₂O₂S₆(584.9): C, 47.23; H, 4.14; N, 4.79;

S 38.38. Found: C, 47.36; H, 4.17; N, 4.82; S, 38.45.

5-Propyl-2-[4,5-bis(pentylthio)-1,3-dithiole-2-yliden]-(1,3)-

dithiolo[4,5-c]pyrrole (17)

2-[4,5-Bis(pentylthio)-1,3-dithiole-2-yliden]-5-tosyl-(1,3)-di-

thiolo[4,5-c]pyrrole (14)

Compound 15 (2.40 g, 5.30 mmol) was dissolved in anhyd DMF

(20 mL) and the solution degassed with N₂for 15 min. C₃H₇Br (6.60

g, 50 mmol) was added, the mixture cooled to 0 °C in an ice/salt

bath whereupon hexane washed NaH (1.20 g, 30 mmol) was added.

The reaction mixture was stirred for 1 h at 0 °C, poured onto ice, ex-

tracted with CH₂Cl₂(3 × 50 mL), and the extracts were dried

(MgSO₄). Evaporation of the solvent gave the crude product, which

was purified by column chromatography (400 mL SiO₂, ∆ = 6 cm;

CH₂Cl₂–petroleum ether, 1:1) to give the title compound 17 as a yel-

low oil; yield: 2.49 g (93%).

A solution of compound 13 (0.20 g, 0.34 mmol) in anhyd THF (40

mL) was degassed (N₂, 10 min) and a solution of CsOH·H₂O

(60.0 mg, 0.36 mmol) in anhyd MeOH (1 mL) was added dropwise

over a period of 1 h. The mixture was stirred for 15 min and C₅H₁₁Br

(56 mg, 0.046 mL, 0.37 mmol) was added in one portion and the re-

action mixture was stirred for 5 h. The solvent was evaporated and

the resulting yellow residue was dissolved in CH₂Cl₂(70 mL),

washed with H₂O (2 × 50 mL), and dried (MgSO₄). Evaporation of

the solvent gave a yellow solid, which was purified by column chro-

matography (200 mL SiO₂, ∆ = 6 cm; cyclohexane–CH₂Cl₂, 3:2)

to give the title compound 14 as a yellow powder; yield: 0.17 g

(82%); mp 80–83 °C (Lit.²²79–81 °C).

¹H NMR (CDCl₃/TMS): d = 0.92 (t, 9 H, J = 7.1 Hz), 1.29–1.42 (m,

8 H), 1.62 (quintet, 4 H, J = 7.2 Hz), 1.75 (sextet, 2 H, J = 7.3 Hz),

2.82 (t, 4 H, J = 7.2 Hz), 3.80 (br s, 2 H), 6.96 (s, 2 H).

¹H NMR (CDCl₃/TMS): d = 0.89 (t, 6 H, J = 7.1 Hz), 1.25–1.45 (m,

8 H), 1.61 (quintet, 4 H, J = 7.2 Hz), 2.41 (s, 3 H), 2.79 (t, 4 H,

J = 7.4 Hz), 6.92 (s, 2 H), 7.29 (d, 2 H, J = 8.3 Hz), 7.72 (d, 2 H,

J = 8.3 Hz).

¹³C NMR (CDCl₃/TMS): d = 14.1, 21.7, 22.2, 29.5, 30.7, 36.4,

111.3, 115.3, 116.2, 127.0, 127.3, 127.6, 130.2, 135.4, 145.5.

¹³C NMR (CDCl₃/TMS): d = 11.1, 13.9, 22.1, 29.4, 30.7, 30.8, 30.9,

36.2, 112.3, 118.5 (2 overlapping peaks), 127.4 (2 overlapping

peaks).

FT-MALDI-MS: m/z (%) = 489 (M⁺, 100).

FT-MALDI-HRMS: m/z calcd for C₂₁H₃₁NS₆, 489.0775; found,

489.0765.

Anal. Calcd C₂₁H₃₁NS₆(489.3): C, 51.49; H, 6.38; N, 2.86; S,

39.27. Found: C, 51.67; H, 6.51; N, 2.88; S, 39.42.

2-[4,5-Bis(pentylthio)-1,3-dithiole-2-yliden]-(1,3)-dithiolo[4,5-

c]pyrrole (15)

A solution of compound 14 (2.41 g, 4.01 mmol) in anhyd THF (120

mL) and anhyd MeOH (40 mL) was degassed (N₂, 15 min); NaOMe

(25% solution in MeOH; 9.1 mL, 2.16 g, 40.0 mmol) was added in

one portion. The yellow mixture was heated at 50 °C for 1 h. After

cooling to r.t., H₂O (200 mL) was added, the mixture was extracted

with CH₂Cl₂(3 × 100 mL) and the extracts were dried (MgSO₄).

Evaporation of the solvent gave a yellow oil, which was purified by

column chromatography (500 mL SiO₂, ∆ = 6 cm; CH₂Cl₂–cyclo-

hexane 1:1) to give the title compound 15 as a yellow solid; yield:

1.75 g (98%); mp 60–62 °C (Lit.²²62–63 °C).

¹H NMR (CDCl₃/TMS): d = 0.90 (t, 6 H, J = 7.1 Hz), 1.25–1.45 (m,

8 H), 1.63 (quintet, 4 H, J = 7.2 Hz,), 2.82 (t, 4 H, J = 7.4 Hz),

6.60 (d, 2 H, J = 2.3 Hz), 8.19 (s, 1 H).

¹³C NMR (CDCl₃/TMS): d = 13.9, 22.1, 29.4, 30.6, 36.2, 109.7,

111.5, 119.8, 120.0, 127.3.

4-(Benzo-1,3-dithiol-2-yl)-5-methyl-2-[4,5-bis(pentylthio)-1,3-

dithiole-2-yliden]-(1,3)-dithiolo[4,5-c]pyrrole (20)

Compound 16 (0.50 g, 1.08 mmol) and 1,3-benzodithiol-2-ylium

tetrafluoroborate (18) (0.26 g, 1.08 mmol) were dissolved in MeCN

(50 mL) at 50 °C. Anhyd pyridine (0.1 mL, 1.26 mmol) was then

added to the dark red solution and the mixture stirred for 20 min at

r.t. The reaction mixture was diluted with CH₂Cl₂(20 mL), H₂O

(100 mL) was added, extracted with CH₂Cl₂(3 × 50 mL), and the

extracts were dried (MgSO₄). Evaporation of the solvent gave the

crude product, which was purified by column chromatography (700

mL SiO₂, ∆ = 6 cm; CH₂Cl₂–petroleum ether, 1:4) to give the title

compound 20 as a yellowish brown solid; yield: 0.35 g (53%); mp

99–103 °C.

¹H NMR (CDCl₃/TMS): d = 0.85–0.96 (m, 6 H), 1.25–1.41 (m, 8

H), 1.55–1.64 (m, 4 H), 2.78 (t, 2 H, J = 7.2 Hz), 2.80 (t, 2 H,

J = 7.2 Hz), 3.60 (br s, 3 H), 6.28 (s, 1 H), 6.39 (s, 1 H), 7.06 (dd, 2

H, J = 9.0, 3.3 Hz), 7.23 (dd, 2 H, J = 9.0, 3.3 Hz).

¹³C NMR (CDCl₃/TMS): d = 13.9, 14.0, 22.1, 29.4 (2 overlapping

peaks), 29.6, 30.6, 30.7, 35.3, 36.1, 36.2, 49.9, 110.1, 115.1, 117.9,

120.1, 120.3, 120.6, 122.5, 125.9, 127.3, 127.5, 137.1.

5-Methyl-2-[4,5-bis(pentylthio)-1,3-dithiole-2-yliden]-(1,3)-

dithiolo[4,5-c]pyrrole (16)

Compound 15 (2.20 g, 4.92 mmol) was dissolved in anhyd DMF

(20 mL) and the solution degassed with N₂for 15 min. MeI (0.69 g,

49.2 mmol) was added, the mixture cooled to 0 °C in an ice/salt bath

whereupon hexane washed NaH (0.69 g, 17.2 mmol) was added.

The reaction mixture was stirred for 1 h and then purged with N₂to

evaporate the excess MeI. The mixture was poured onto ice, extract-

ed with CH₂Cl₂(3 × 50 mL), and dried (MgSO₄). Evaporation of the

solvent gave the crude product, which was purified by column chro-

matography (400 mL SiO₂, ∆ = 6 cm; CH₂Cl₂–petroleum ether,

1:1) to give the title compound 16 as a yellow oil; yield: 2.20 g

(96%).

¹H NMR (CDCl₃/TMS): d = 0.92 (t, 6 H, J = 7.0 Hz), 1.28–1.46 (m,

8 H), 1.63 (quintet, 4 H, J = 7.0 Hz), 2.83 (t, 4 H, J = 7.0 Hz), 3.65

(br s, 3 H), 6.42 (s, 2 H).

¹³C NMR (CDCl₃/TMS): d = 13.9, 22.3, 29.4, 30.7, 36.2, 37.2,

113.4, 118.8 (2 overlapping peaks), 127.4 (2 overlapping peaks).

FT-MALDI-MS: m/z (%) = 613 (M⁺, 100).

FT-MALDI-HRMS: m/z calcd for C₂₇H₃₆NS₈, 613.0217; found,

613.0198.

4-(2-Phenylbenzo-1,3-dithiol-2-yl)-5-methyl-2-[4,5-bis(pen-

tylthio)-1,3-dithiole-2-yliden]-(1,3)-dithiolo[4,5-c]pyrrole (21)

Compound 16 (0.50 g, 1.08 mmol) and 2-phenyl-1,3-benzodithiol-

2-ylium tetrafluoroborate (19) (0.34 g, 1.08 mmol) were dissolved

in MeCN (50 mL) at 50 °C. Anhyd pyridine (0.1 mL, 1.26 mmol)

was then added to the dark red solution and the mixture stirred for

30 min at r.t. The reaction mixture was diluted with CH₂Cl₂(20

mL), H₂O (100 mL) was added, extracted with CH₂Cl₂(3 × 50 mL),

and the extracts were dried (MgSO₄). Evaporation of the solvent

gave the crude product, which was purified by column chromatog-

raphy (600 mL SiO₂, ∆ = 6 cm; CH₂Cl₂–petroleum ether, 1:3) to

give the title compound 21 as an orange solid; yield: 0.49 g (65%);

mp 68–70 °C.

FT-MALDI-MS: m/z (%) = 461 (M⁺, 90).

FT-MALDI-HRMS: m/z calcd for C₁₉H₂₇NS₆, 461.0462; found,

461.0449.

Synthesis 2005, No. 8, 1251–1260 © Thieme Stuttgart · New York

1256

H. Gopee et al.

PAPER

¹H NMR (CDCl₃/TMS): d = 0.87–0.97 (m, 6 H), 1.29–1.44 (m, 8

H), 1.56–1.71 (m, 4 H), 2.83 (m, 4 H), 3.60 (br s, 3 H), 6.44 (s, 1 H),

7.09 (dd, 2 H, J = 8.9, 3.2 Hz), 7.24 (dd, 2 H, J = 8.9, 3.2 Hz),

7.28–7.37 (m, 3 H), 7.59–7.66 (m, 2 H).

¹³C NMR (CDCl₃/TMS): d = 14.0 (2 overlapping peaks), 22.2 (2

overlapping peaks), 29.4 (2 overlapping peaks), 30.5 (2 overlapping

peaks), 30.6, 30.7, 36.2, 49.5, 116.4, 122.6, 126.3, 127.3, 127.4,

127.6, 127.7, 127.8, 128.4, 128.6, 128.7, 128.8, 137.4, 138.3, 138.5.

127.6, 127.8, 128.7 (2 overlapping peaks), 128.8 (2 overlapping

peaks), 137.5, 138.3, 138.5.

FT-MALDI-MS: m/z (%) = 717 (M⁺, 100).

FT-MALDI-HRMS: m/z calcd for C₃₄H₃₉NS₈, 717.0843; found,

717.0868.

Anal. Calcd for C₃₄H₃₉NS₈(717.3): C, 56.86; H, 5.47; N, 1.95; S,

35.72. Found: C, 57.01; H, 5.50; N, 1.91; S, 35.99.

FT-MALDI-MS: m/z (%) = 689 (M⁺, 100).

5-Methyl-2-[4,5-bis(pentylthio)-1,3-dithiole-2-yliden]-(1,3)-

dithiolo[4,5-c]pyrrole-4-carbaldehyde (24)

FT-MALDI-HRMS: m/z calcd for C₃₂H₃₅NS₈, 689.0530; found,

689.0559.

Compound 20 (0.20 g, 0.40 mmol) was dissolved in DMSO (20

mL) and the solution stirred at 100 °C. Hg(OAc)₂(1.24 g, 4.0

mmol) was then added in one portion and the mixture stirred at the

same temperature for a further 1 h. (TLC analysis was performed af-

ter treatment of an aliquot with an aq solution of KI). The reaction

mixture was allowed to cool down and an aq solution of KI (50 mL,

10%) was added. The mixture was extracted with CH₂Cl₂(3 × 50

mL), the extracts were filtered through celite, and dried (MgSO₄).

Evaporation of the solvent gave the crude product, which was puri-

fied by column chromatography (400 mL SiO₂, ∆ = 6 cm; CH₂Cl₂–

petroleum ether, 1:1) to give the title compound 24 as a yellow oil;

yield: 0.12 g (73%).

¹H NMR (CDCl₃/TMS): d = 0.94 (t, 6 H, J = 7.0 Hz), 1.00–1.56 (m,

8 H), 1.62–1.70 (m, 4 H), 2.82 (t, 2 H, J = 7.1 Hz), 2.83 (t, 2 H,

J = 7.0 Hz), 3.92 (br s, 3 H), 6.63 (s, 1 H), 9.59 (s, 1 H).

¹³C NMR (CDCl₃/TMS): d = 13.9 (2 overlapping peaks), 22.2 (2

overlapping peaks), 29.4 (2 overlapping peaks), 29.5, 29.7 (2 over-

lapping peaks), 30.6, 36.3, 112.8, 117.9, 120.6, 121.6, 124.5, 127.1,

127.9, 152.1, 176.2.

Anal. Calcd for C₃₂H₃₅NS₈(689.7): C, 55.69; H, 5.11; N, 2.03; S,

37.17. Found: C, 55.97; H, 5.15; N, 2.01; S, 37.15.

4-(Benzo-1,3-dithiol-2-yl)-5-propyl-2-[4,5-bis(pentylthio)-1,3-

dithiole-2-yliden]-(1,3)-dithiolo[4,5-c]pyrrole (22)

Compound 17 (0.60 g, 1.23 mmol) and 1,3-benzodithiol-2-ylium-

tetrafluoroborate (18) (0.29 g, 1.23 mmol) were dissolved in MeCN

(50 mL) at 50 °C. Anhyd pyridine (0.25 mL, 2.20 mmol) was then

added to the dark red solution and the mixture stirred for 20 min at

r.t. The reaction mixture was diluted with CH₂Cl₂(20 mL), H₂O

(100 mL), extracted with CH₂Cl₂(3 × 50 mL), and the extracts were

dried (MgSO₄). Evaporation of the solvent gave the crude product,

which was purified by column chromatography (600 mL SiO₂,

∆ = 6 cm; CH₂Cl₂–petroleum ether, 1:4) to give the title compound

22 as a brown solid; yield: 0.48 g (61%), mp 107–108 °C.

¹H NMR (CDCl₃/TMS): d = 0.85–0.96 (m, 9 H), 1.25–1.41 (m, 8

H), 1.65 (quintet, 4 H, J = 7.2 Hz), 1.75 (sextet, 2 H, J = 7.0 Hz),

2.78 (t, 2 H, J = 7.2 Hz), 2.80 (t, 2 H, J = 7.2 Hz), 3.79 (br s, 2 H),

6.38 (s, 1 H), 6.44 (s, 1 H), 7.05 (dd, 2 H, J = 9.1, 3.3 Hz), 7.23 (dd,

2 H, J = 9.1, 3.3 Hz).

FT-MALDI-MS: m/z (%) = 489 (M⁺, 100).

FT-MALDI-HRMS: m/z calcd for C₂₀H₂₇NS₆: 489.0411; found:

489.0416.

¹³C NMR (CDCl₃/TMS): d = 11.1, 13.9 (2 overlapping peaks), 22.2

(2 overlapping peaks), 25.4 (2 overlapping peaks), 29.4 (2 overlap-

ping peaks), 30.7 (2 overlapping peaks), 36.2 (2 overlapping peaks),

49.0, 119.9, 120.1, 120.3, 120.9, 122.5 (2 overlapping peaks), 126.1

(2 overlapping peaks), 127.1, 127.3, 137.4.

5-Methyl-2-[4,5-bis(pentylthio)-1,3-dithiole-2-yliden]-(1,3)-

dithiolo[4,5-c]pyrrol-4-yl-phenylmethanone (25)

Compound 21 (0.30 g, 0.43 mmol) was dissolved in DMSO (30

mL) and the solution stirred at 100 °C. Hg(OAc)₂(1.38 g, 4.34

mmol) was then added in one portion and the mixture stirred at the

same temperature for a further 1 h. (TLC analysis was performed af-

ter treatment of an aliquot with an aq solution of KI). The reaction

mixture was allowed to cooled to r.t. and an aq solution of KI (30

mL, 10%) was added. The mixture was extracted with CH₂Cl₂

(3 × 50 mL), the extracts were filtered through celite, and dried

(MgSO₄). Evaporation of the solvent gave the crude product, which

was purified by column chromatography (600 mL SiO₂, ∆ = 6 cm;

CH₂Cl₂–petroleum ether, 3:7) to give the title compound 25 as a red

brown solid; yield: 0.17 g (69%); mp 70–74 °C.

¹H NMR (CDCl₃/TMS): d = 0.92 (t, 6 H, J = 7.2 Hz), 1.11–1.41 (m,

8 H), 1.60 (quintet, 4 H, J = 7.1 Hz), 2.76 (t, 2 H, J = 7.2 Hz), 2.80

(t, 2 H, J = 7.1 Hz), 3.96 (br s, 3 H), 6.70 (s, 1 H), 7.50 (dd, 2 H,

J = 7.3, 6.9 Hz), 7.60 (d, 1 H, J = 7.3 Hz) 7.70 (d, 2 H, J = 6.9 Hz).

¹³C NMR (CDCl₃/TMS): d = 13.9 (2 overlapping peaks), 22.2 (2

overlapping peaks), 29.3 (2 overlapping peaks), 30.6 (2 overlap-

ping peaks), 36.3 (2 overlapping peaks), 38.2, 118.9, 121.9 (2 over-

lapping peaks), 127.3, 127.7, 128.4 (2 overlapping peaks), 128.8 (2

overlapping peaks), 131.8, 132.3, 138.3, 185.3

FT-MALDI-MS: m/z (%) = 641 (M⁺, 100).

FT-MALDI-HRMS: m/z calcd for C₂₈H₃₅NS₈, 641.0530; found,

641.0505.

Anal. Calcd for C₂₈H₃₅NS₈(641.5): C, 52.38; H, 5.49; N, 2.18; S,

39.95. Found: C, 52.76; H, 5.65; N, 2.17; S, 39.65.

4-(2-Phenylbenzo-1,3-dithiol-2-yl)-5-propyl-2-[4,5-bis(pen-

tylthio)-1,3-dithiole-2-yliden]-(1,3)-dithiolo[4,5-c]pyrrole (23)

Compound 17 (0.30 g, 0.61 mmol) and 2-phenyl-1,3-benzodithiol-

2-ylium tetrafluoroborate (19) (0.19 g, 0.61 mmol) were dissolved

in MeCN (50 mL) at 50 °C. Anhyd pyridine (0.3 mL, 3.7 mmol)

was then added to the dark red solution and the mixture stirred for

30 min at r.t. The reaction mixture was diluted with CH₂Cl₂(20

mL), H₂O (100 mL) was added, extracted with CH₂Cl₂(3 × 50 mL),

and the extracts were dried (MgSO₄). Evaporation of the solvent

gave the crude product, which was purified by column chromatog-

raphy (700 mL SiO₂, ∆ = 6 cm; CH₂Cl₂–petroleum ether, 1:1) to

give the title compound 23 as a yellow oil; yield: 0.33 g (75%).

¹H NMR (CDCl₃/TMS): d = 0.68 (t, 3 H, J = 7.1 Hz), 0.90–0.94 (m,

6 H), 1.29–1.52 (m, 10 H), 1.56–1.67 (m, 4 H), 2.84 (m, 4 H), 3.60

(br, 2 H), 6.53 (s, 1 H), 7.08 (dd, 2 H, J = 9.0, 3.1 Hz), 7.25 (dd, 2

H, J = 9.0, 3.1 Hz), 7.28–7.33 (m, 3 H), 7.61–7.65 (m, 2 H).

¹³C NMR (CDCl₃/TMS): d = 11.0, 14.0 (2 overlapping peaks), 22.2

(2 overlapping peaks), 29.4 (2 overlapping peaks), 30.6 (2 overlap-

ping peaks), 30.7 (2 overlapping peaks), 36.2 (2 overlapping peaks),

49.3, 116.6, 122.6, 126.3 (2 overlapping peaks), 127.5, 127.4,

FT-MALDI-MS: m/z (%) = 565 (M⁺, 100).

FT-MALDI-HRMS: m/z calcd for C₂₆H₃₁NS₆, 565.0724; found,

565.0739.

Anal. Calcd for C₂₆H₃₁NS₆(565.4): C, 55.18; H, 5.52; N, 2.48; S,

33.99. Found: C, 55.06; H, 5.62; N, 2.33; S, 33.73.

Synthesis 2005, No. 8, 1251–1260 © Thieme Stuttgart · New York

PAPER

Complete Sequential Functionalization of Monopyrrolotetrathiafulvalenes

1257

5-Propyl-2-[4,5-bis(pentylthio)-1,3-dithiole-2-yliden]-(1,3)-

dithiolo[4,5-c]pyrrole-4-carbaldehyde (26)

compound 28 as an orange yellow solid; yield: 0.40 g (49%); mp

71–72 °C.

Method B:

Compound 22 (0.20 g, 0.31 mmol) was dissolved in DMSO (20

mL) and the solution stirred at 100 °C. Hg(OAc)₂(1.00 g, 3.11

mmol) was then added in one portion and the mixture stirred at the

same temperature for a further 1 h (TLC analysis was performed af-

ter treatment of an aliquot with an aq solution of KI). The reaction

mixture was allowed to cool to r.t. and an aq solution of KI (30 mL,

10%) was added. The mixture was extracted with CH₂Cl₂(3 × 50

mL), the extracts were filtered through celite, and dried (MgSO₄).

Evaporation of the solvent gave the crude product, which was puri-

fied by column chromatography (500 mL SiO₂, ∆ = 6 cm; CH₂Cl₂–

petroleum ether, 1:1) to give the title compound 26 as a yellow oil;

yield: 0.11 g (70%).

¹H NMR (CDCl₃/TMS): d = 0.87–0.95 (m, 9 H), 1.10–1.59 (m, 8

H), 1.61–1.68 (m, 4 H), 1.79 (sextet, 2 H, J = 7.0 Hz), 2.80 (t, 4 H,

J = 7.0 Hz), 4.17 (t, 2 H, J = 7.2 Hz), 6.68 (s, 1 H), 9.56 (s, 1 H).

¹³C NMR (CDCl₃/TMS): d = 13.9 (2 overlapping peaks), 22.2 (2

overlapping peaks), 24.8 (2 overlapping peaks), 29.3 (2 overlapping

peaks), 29.4 (2 overlapping peaks), 30.6 (2 overlapping peaks),

36.2, 93.2, 117.8, 120.5, 120.8, 123.9, 127.1, 127.8, 155.0, 175.9.

Compound 20 (0.10 g, 0.16 mmol) and 1,3-benzodithiol-2-ylium

tetrafluoroborate (18) (0.078 g, 0.33 mmol) were dissolved in

MeCN (20 mL) at 50 °C. Anhyd pyridine (0.1 mL, 1.2 mmol) was

then added to the dark red solution and the mixture stirred for 20

minutes at r.t. The reaction mixture was diluted with CH₂Cl₂(20

mL), H₂O (100 mL) was added, extracted with CH₂Cl₂(3 × 50 mL),

and the extracts were dried (MgSO₄). Evaporation of the solvent

gave the crude product, which was purified by column chromatog-

raphy (700 mL SiO₂, ∆ = 6 cm; CH₂Cl₂–petroleum ether, 1:4) to

give the title compound 28 as an orange yellow solid; yield: 0.10 g

(80%); mp 70–73 °C.

¹H NMR (CDCl₃/TMS): d = 0.89 (t, 6 H, J = 7.3 Hz), 1.28–1.39 (m,

8 H), 1.58 (quintet, 4 H, J = 7.0 Hz), 2.78 (t, 4 H, J = 7.0 Hz), 3.59

(br s, 3 H), 6.25 (s, 2 H), 7.07 (dd, 4 H, J = 9.0, 3.3 Hz), 7.23 (dd, 4

H, J = 9.0, 3.3 Hz).

¹³C NMR (CDCl₃/TMS): d = 14.1, 22.3, 29.6, 30.8, 32.4, 36.4, 48.9,

120.3, 122.8 (2 overlapping peaks), 126.2 (2 overlapping peaks),

127.5, 137.1 (2 overlapping peaks)

FT-MALDI-MS: m/z (%) = 517 (M⁺, 100).

FT-MALDI-MS: m/z (%) = 765 (M⁺, 100).

FT-MALDI-HRMS: m/z calcd for C₂₂H₃₁NS₆: 517.07244; found:

517.0708.

FT-MALDI-HRMS: m/z calcd for C₃₃H₃₅NS₁₀, 764.9971; found,

765.0013.

5-Propyl-2-[4,5-bis(pentylthio)-1,3-dithiole-2-yliden]-(1,3)-

dithiolo[4,5-c]pyrrol-4-yl-phenylmethanone (27)

Anal. Calcd for C₃₃H₃₅NS₁₀(765.3): C, 51.73; H, 4.60; N, 1.83; S

41.84. Found: C, 51.84; H, 4.71; N, 1.87; S, 41.77.

Compound 23 (0.25 g, 0.35 mmol) was dissolved in DMSO (30

mL) and the solution stirred at 100 °C. Hg(OAc)₂(0.11 g, 3.48

mmol) was then added in one portion and the mixture stirred at the

same temperature for a further 1 h (TLC analysis was performed af-

ter treatment of an aliquot with an aq solution of KI). The reaction

mixture was allowed to cool to r.t. and an aq solution of KI (30 mL,

10%) was added. The mixture was extracted with CH₂Cl₂(3 × 50

mL), the combined extracts filtered through celite, and dried

(MgSO₄). Evaporation of the solvent gave the crude product, which

was purified by column chromatography (600 mL SiO₂, ∆ = 6 cm;

CH₂Cl₂–petroleum ether, 1:1) to give the title compound 27 as a red

brown oil; yield: 0.14 g (70%).

¹H NMR (CDCl₃/TMS): d = 0.85–0.89 (m, 9 H), 1.25–1.41 (m, 8

H), 1.61 (quintet, 4 H, J = 7.1 Hz), 1.78 (sextet, 2 H, J = 7.2 Hz),

2.73 (t, 2 H, J = 7.1 Hz), 2.80 (t, 2 H, J = 7.1 Hz), 4.27 (br, 2 H),

6.76 (s, 1 H), 7.50 (dd, 2 H, J = 7.2, 7.0 Hz), 7.60 (d, 1 H, J = 7.2

Hz) 7.70 (d, 2 H, J = 7.0 Hz).

4,6-Bis-(2-phenylbenzo-1,3-dithiol-2-yl)-5-methyl-2-[4,5-

bis(pentylthio)-1,3-dithiole-2-yliden]-(1,3)-dithiolo[4,5-c]pyr-

role (29)

Method A:

Compound 16 (0.30 g, 0.65 mmol) and 2-phenyl-1,3-benzodithiol-

2-ylium tetrafluoroborate (19) (1.02 g, 3.25 mmol) were dissolved

in MeCN (50 mL) at 50 °C. Anhyd pyridine (0.3 mL, 3.7 mmol)

was then added to the dark red solution and the mixture stirred under

reflux for 10 h. The reaction mixture was diluted with CH₂Cl₂(20

mL), H₂O (100 mL) was added, extracted with CH₂Cl₂(3 × 50 mL),

and the extracts were dried (MgSO₄). Evaporation of the solvent

gave the crude product, which was purified by column chromatog-

raphy (700 mL SiO₂, ∆ = 6 cm; CH₂Cl₂–petroleum ether, 1:4) to

give the title compound 29 as a yellow solid; yield: 0.26 g (45%);

mp 109–110 °C.

Method B:

¹³C NMR (CDCl₃/TMS): d = 11.0, 13.9, 22.2, 24.9, 28.9, 29.3, 29.4,

29.7, 30.6, 31.2, 36.3, 38.1, 52.1, 111.6, 118.9, 121.2, 127.3, 127.7,

128.4 (2 overlapping peaks), 128.8 (2 overlapping peaks), 132.3 (2

overlapping peaks), 138.5, 185.3

Compound 21 (0.10 g, 0.15 mmol) and 2-phenyl-1,3-benzodithiol-

2-ylium tetrafluoroborate (19) (0.11 g, 0.36 mmol) were dissolved

in MeCN (50 mL) at 50 °C. Anhyd pyridine (0.1 mL, 1.2 mmol)

was then added to the dark red solution and the mixture refluxed for

10 h. The reaction mixture was diluted with CH₂Cl₂(20 mL), H₂O

(100 mL) was added, extracted with CH₂Cl₂(3 × 50 mL), and the

extracts were dried (MgSO₄). Evaporation of the solvent gave the

crude product, which was purified by column chromatography (700

mL SiO₂, ∆ = 6 cm; CH₂Cl₂–petroleum ether, 1:4) to give the title

compound 29 as a yellow solid; yield: 0.092 g (68%); mp 109–

112 °C.

FT-MALDI-MS: m/z (%) = 593 (M⁺, 100).

FT-MALDI-HRMS: m/z calcd for C₂₈H₃₅NS₆, 593.1037; found,

593.1011.

4,6-Bis(benzo-1,3-dithiol-2-yl)-5-methyl-2-[4,5-bis(pentylthio)-

1,3-dithiole-2-yliden]-(1,3)-dithiolo[4,5-c]pyrrole (28)

Method A:

¹H NMR (CDCl₃/TMS): d = 0.92 (t, 6 H, J = 7.1 Hz), 1.30–1.42 (m,

8 H), 1.58 (quintet, 4 H, J = 7.3 Hz), 2.81 (t, 4 H, J = 7.3 Hz), 3.59

(br s, 3 H), 7.08 (dd, 4 H, J = 9.0, 3.1 Hz), 7.19–7.32 (m, 10 H),

7.59 (dd, 4 H, J = 9.0, 3.1 Hz).

¹³C NMR (CDCl₃/TMS): d = 14.0, 22.2, 29.4 (2 overlapping peaks),

30.7, 36.3, 72.4, 122.5 (2 overlapping peaks), 126.3 (2 overlapping

peaks), 127.4 (2 overlapping peaks), 128.6, 128.7 (2 overlapping

peaks), 137.4 (2 overlapping peaks), 138.5.

Compound 16 (0.50 g, 1.08 mmol) and 1,3-benzodithiol-2-ylium

tetrafluoroborate (18) (0.65 g, 2.72 mmol) were dissolved in MeCN

(50 mL) at 50 °C. Anhyd pyridine (0.3 mL, 3.7 mmol) was then

added to the dark red solution and the mixture stirred for 20 min at

r.t. The reaction mixture was diluted with CH₂Cl₂(20 mL), H₂O

(100 mL) was added, extracted with CH₂Cl₂(3 × 50 mL), and the

extracts were dried (MgSO₄). Evaporation of the solvent gave the

crude product, which was purified by column chromatography (700

mL SiO₂, ∆ = 6 cm; CH₂Cl₂–petroleum ether, 1:4) to give the title

1258

H. Gopee et al.

PAPER

FT-MALDI-MS: m/z (%) = 917 (M⁺, 30).

Method B:

FT-MALDI-HRMS: m/z calcd for C₄₅H₄₃NS₁₀, 917.0597; found,

917.0572.

Compound 23 (0.10 g, 0.14 mmol) and 2-phenyl-1,3-benzodithiol-

2-ylium tetrafluoroborate (19) (0.11 g, 0.36 mmol) were dissolved

in warm MeCN (50 mL). Anhyd pyridine (0.1 mL, 1.2 mmol) was

then added to the dark red solution and the mixture stirred under re-

flux for 10 h. The reaction mixture was diluted with CH₂Cl₂(20

mL), H₂O (100 mL) was added, extracted CH₂Cl₂(3 × 50 mL), and

the combined organic phases were dried (MgSO₄). Evaporation of

the solvent gave the crude product, which was purified by column

chromatography (400 mL SiO₂, ∆ = 6 cm; CH₂Cl₂–petroleum

ether, 1:4) to give the title compound 31 as a yellow solid; yield:

0.10 g (78%); mp 97–99 °C.

¹H NMR (CDCl₃/TMS): d = 0.25 (t, 3 H, J = 7.3 Hz), 0.91 (t, 6 H,

J = 7.1 Hz), 1.30–1.42 (m, 10 H), 1.61 (quintet, 4 H, J = 7.1 Hz),

2.81 (t, 4 H, J = 7.1 Hz), 3.60 (br, 2 H), 7.08 (dd, 4 H,

J = 8.9, 3.0 Hz), 7.20–7.31 (m, 10 H), 7.53 (dd, 4 H, J = 8.9,

3.0 Hz).

Anal. Calcd for C₄₅H₄₃NS₁₀(917.6): C, 58.85; H, 4.72; N, 1.52; S,

34.91. Found: C, 58.68; H, 4.91; N, 1.54; S, 34.71.

4,6-Bis(benzo-1,3-dithiol-2-yl)-5-propyl-2-[4,5-bis(pentylthio)-

1,3-dithiole-2-yliden]-(1,3)-dithiolo[4,5-c]pyrrole (30)

Method A:

Compound 17 (0.40 g, 0.82 mmol) and 1,3-benzodithiol-2-ylium

tetrafluoroborate (18) (0.49 g, 2.04 mmol) were dissolved in MeCN

(50 mL) at 50 °C. Anhyd pyridine (0.3 mL, 3.7 mmol) was then

added to the dark red solution and the mixture stirred for 20 min at

r.t. The reaction mixture was diluted with CH₂Cl₂(20 mL), H₂O

(100 mL) was added, extracted with CH₂Cl₂(3 × 50 mL) and the ex-

tracts were dried (MgSO₄). Evaporation of the solvent gave the

crude product, which was purified by column chromatography (500

mL SiO₂, ∆ = 6 cm; CH₂Cl₂–petroleum ether, 1:1) to give the title

compound 30 as a yellow solid; yield: 0.35 g (55%), mp 136–

138 °C.

¹³C NMR (CDCl₃/TMS): d = 10.7, 14.0, 22.2 (2 overlapping peaks),

29.4, 30.7 (2 overlapping peaks), 36.2, 48.3, 122.5 (2 overlapping

peaks), 126.3 (2 overlapping peaks), 127.3 (2 overlapping peaks),

128.5, 128.6 (2 overlapping peaks), 137.5 (2 overlapping peaks),

139.9

Method B:

Compound 22 (0.10 g, 0.16 mmol) and 1,3-benzodithiol-2-ylium

tetrafluoroborate (18) (0.49 g, 0.23 mmol) were dissolved in MeCN

(20 mL) at 50 °C. Anhyd pyridine (0.1 mL, 1.2 mmol) was then

added to the dark red solution and the mixture stirred for 20 min at

room temperature. The reaction mixture was diluted with CH₂Cl₂

(20 mL), H₂O (100 mL) was added, extracted with CH₂Cl₂(3 × 50

mL) and the extracts were dried (MgSO₄). Evaporation of the sol-

vent gave the crude product, which was purified by column chroma-

tography (500 mL SiO₂, ∆ = 6 cm; CH₂Cl₂–petroleum ether, 1:1)

to give the title compound 30 as a yellow solid; yield: 0.074 g

(60%), mp 136–138 °C.

¹H NMR (CDCl₃/TMS): d = 0.89 (t, 6 H, J = 7.1 Hz), 0.95 (t, 3 H,

J = 7.2 Hz), 1.26–1.42 (m, 8 H), 1.59 (quintet, 4 H, J = 7.0 Hz),

1.78 (sextet, 2 H, J = 7.0 Hz), 2.77 (t, 4 H, J = 7.0 Hz), 3.79 (br s,

2 H), 6.41 (s, 2 H), 7.07 (dd, 4 H, J = 9.1, 3.3 Hz), 7.21 (dd, 4 H,

J = 9.1, 3.3 Hz).

FT-MALDI-MS: m/z (%) = 945 (M⁺, 20).

FT-MALDI-HRMS: m/z calcd for C₄₇H₄₇NS₁₀: 945.0910; found:

945.0894.

Anal. Calcd for C₄₇H₄₇NS₁₀(945.7): C, 59.64; H, 5.00; N, 1.48; S,

33.87. Found: C, 59.87; H, 5.10; N, 1.56; S, 33.97.

5-Methyl-2-[4,5-Bis(pentylthio)-1,3-dithiole-2-yliden]-(1,3)-

dithiolo[4,5-c]pyrrole-4,6-dicarbaldehyde (32)

Compound 28 (0.30 g, 0.39 mmol) was dissolved in DMSO (20

mL) and the solution stirred at 100 °C. Hg(OAc)₂(1.25 g, 3.91