Preparation of new dialkyl benzene-, biphenyl-, and naphthalene- bis(α-oxoethanedithioates)

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Preparation of New Dialkyl Benzene-,

Biphenyl-, and Naphthalene-bis(α-

oxoethanedithioates)

Jürgen Voss ^a, Abraam Sarafidis ^a, Andrzej Sawluk ^a, Gunther

Schmidt ^a& Gunadi Adiwidjaja ^a

^aDepartment of Chemistry , University of Hamburg , Hamburg ,

Germany

Published online: 05 Nov 2010.

To cite this article: Jürgen Voss , Abraam Sarafidis , Andrzej Sawluk , Gunther Schmidt & Gunadi

Adiwidjaja (2010) Preparation of New Dialkyl Benzene-, Biphenyl-, and Naphthalene-bis(α-

oxoethanedithioates), Phosphorus, Sulfur, and Silicon and the Related Elements, 185:11, 2249-2276,

DOI: 10.1080/10426500903575409

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Phosphorus, Sulfur, and Silicon, 185:2249–2276, 2010

Copyright ^ꢀCTaylor & Francis Group, LLC

ISSN: 1042-6507 print / 1563-5325 online

DOI: 10.1080/10426500903575409

PREPARATION OF NEW DIALKYL BENZENE-, BIPHENYL-,

AND NAPHTHALENE-BIS(α-OXOETHANEDITHIOATES)

Ju¨rgen Voss, Abraam Saraﬁdis, Andrzej Sawluk,

Gunther Schmidt, and Gunadi Adiwidjaja

Department of Chemistry, University of Hamburg, Hamburg, Germany

Novel arene-bis- and -tris(α-oxoethanedithioate) esters of the benzene, the biphenyl, and, in

particular, the naphthalene series were prepared by reaction of the corresponding diazoacetyl

or bromoacetyl derivatives with elemental sulfur in the presence of triethylamine in dry DMF,

and subsequent direct alkylation of the produced dithiocarboxylate anions. The thiolation

reaction of the diazoketones was signiﬁcantly promoted by the addition of anhydrous cal-

cium chloride (calcium chloride–activated thiolation, or CAT). Certain carbonyl-activated

methylene and methyl compounds exhibiting no bromo or diazo substituents could be also

transformed into dithioesters by the CAT reaction. The structure of three dithioesters was

corroborated by X-ray structural analyses.

Supplemental materials are available for this article. Go to the publisher’s online edition of

Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental

ﬁle.

Keywords Alkyl β-aryl-α-oxo-ethanedithioates; α-bromoketones; calcium chloride activa-

tion; α-diazoketones; thiolation

INTRODUCTION

The preparation of methyl α-oxo-dithiocarboxylates^1–3was ﬁrst described in 1978

by Mayer et al.⁴Phenacyl halides were used as starting compounds. Their reaction with

a “thiolating mixture” consisting of elemental sulfur and triethylamine in an appropriate

solvent led to arenedithioglyoxalate salts, which ﬁnally were methylated to the correspond-

ing dithioesters.⁴Later on, aryl methyl ketones were shown to react with iodine/pyridine.

The resulting pyridinium salts were thiolated, and the intermediate arenedithioglyoxalates

were methylated to the dithioesters.⁵Hoepping and Mayer also described the forma-

tion of arenedithioglyoxalates by direct base-catalyzed (sodium tert-butylate) reaction of

acetophenones with diethyl sulﬁde,⁶whereas Hansen and Heinemann obtained aromatic

methyl α-oxo-dithiocarboxylates by reaction of acetophenones with sulfur dioxide in the

Received 28 September 2009; accepted 18 December 2009.

The Universita¨t Hamburg, the Konrad-Adenauer-Stiftung (graduate scholarship A. S.), and the Fonds der

Chemischen Industrie are gratefully acknowledged for ﬁnancial support. We thank Prof. Dr. U. Behrens (X-Ray),

Dr. Volker Sinnwell (NMR), and Manfred Didschun (preparations), Universita¨t Hamburg, for their competent

assistance.

Address correspondence to Prof. Dr. Ju¨rgen Voss, Department of Chemistry, University of Hamburg, Martin-

Luther-King-Platz 6, D-20146 Hamburg, Germany. E-mail: voss@chemie.uni-hamburg.de

2249

2250

J. VOSS ET AL.

presence of secondary amines and elemental sulfur, methylation of the intermediate 2-

aryl-2-iminiodithioacetates Ar C( NR₂)⁺CS₂under formation of the dithioesters

−

Ar C( NR₂)⁺CS₂Me, and hydrolysis of the iminium group of the latter.⁷Also, ben-

zaldehyde cyanohydrin can be transformed into an α-oxo-dithiocarboxylic ester⁸, and

the 2-benzoyl-1-methyl-1,3-dithiolium salts obtained from phenylglyoxal yield methyl

phenyldithioglyoxalate by a cycloreversion reaction.⁹

We have found out that α-oxo-dithiocarboxylate esters can be advantageously ob-

tained from acyl chlorides as well, which are, in many cases, more easily available starting

compounds compared with the corresponding α-haloacetophenones. The reaction of acid

chlorides with diazomethane leads to diazoketones,¹⁰which can be thiolated with ele-

mental sulfur in the presence of triethylamine.¹Moreover, we have discovered that the

thiolation of diazoketones is dramatically improved by the addition of anhydrous calcium

chloride to the reaction mixture (calcium chloride activated thiolation reaction, or CAT

reaction).¹We have successfully applied this CAT reaction for the preparation of quite a

number of aromatic and aliphatic alkyl α-oxo-dithiocarboxylates, including benzene-bis-

and benzene-tris-dithioglyoxalates.¹

In continuation of our EPR spectroscopic investigations on the radical anions of

α-oxo-dithiocarboxylate esters,^2,11,12the results of which will be published elsewhere, we

needed further specimens of this class of compounds. We were, in particular, interested in

the corresponding naphthalene derivatives, the preparation of which by various methods is

reported here.

RESULTS AND DISCUSSION

First, we prepared benzene-bis-dithioglyoxalates with alkyl substituents at the ben-

zene ring or a bulky S-isopropyl substituent, whose groups were expected to cause steric

hindrance. This would possibly change the conformation, i.e., the torsion of the functional

groups out of the plane of the benzene ring, whereas the known unsubstituted dimethyl

ester 7¹exhibits a torsion angle of only 16^◦(see below).

We applied the CAT route for the preparation of ﬁve new methylbenzene-

bis-dithioglyoxalates. The reaction of 2- and 4-methylisophthaloyl dichloride,

2-methylterephthaloyl dichloride, and 2,5-dimethylterephthaloyl dichloride with di-

azomethane led to the bis-diazoketones 1, 2, 5, and 6. Thiolation under CAT conditions

and subsequent alkylation with iodomethane or iodoethane gave the bis-dithioesters 3, 4,

8, 9, and 10 (Scheme 1). In view of the multiple steps during the course of the complex

CAT reaction, and the presence of each two diazoketone groups in the starting molecules,

expectedly the yields for the deciding last two steps of the ﬁve-step syntheses were quite

acceptable (23%, 24%, 42%, 22%, and 9%, respectively) and satisfactory for our intended

studies. The preparation of 8 via reaction of 5 with hydrogen bromide and thiolation of the

resulting 1,4-bis(bromoacetyl)-2-methylbenzene was disadvantageous, since both steps

gave low yields of only 14% each compared with the achieved 42% of 8 by the direct

one-step thiolation of 5. The 4% yield of 1,4-bis(bromoacetyl)-2,5-dimethylbenzene from

6 was even worse and thus not useful for the preparation of 9. Diisopropyl 1,4-benzene-

bis-dithioglyoxalate 11 was prepared via side-chain bromination of 1,4-diacetylbenzene,

thiolation of the resulting bis-bromoketone, and alkylation with 2-iodopropane. We were

also able to prepare the asymmetric 1,4-benzene-bis-dithioglyoxalate ester 12 with still

10% yield by successive alkylation of the dithioglyoxalate salt, ﬁrst with the less reactive

2-iodopropane and then with iodomethane (Scheme 1). Obviously, due to the pronounced

BENZENE-, BIPHENYL-, NAPHTHALENE-BIS(α-OXOETHANEDITHIOATES)

2251

CO-Cl

CO-CHN₂

R¹

CO-CS-SCH₃

R¹

(1)

(2), (3)

CO-Cl

CO-CHN₂

CO-CS-SCH₃

R²

1, 2

3: R¹= Me, R²= H

4: R¹= H, R²= Me

R²

Cl

O

CHN₂

O

(1)

(2), (3)

N₂HC

O

Cl

R¹

5, 6

R²

S

3

7: R¹= R²= H, R³= Me

8: R¹= H, R²= R³= Me

9: R¹= R²= R³= Me

O

S

R

³S

O

R

10: R¹= R²= Me, R³= Et

S

R¹

S

SiPr

O

CH₂Br

O

(4), (5)

iPrS

O

BrH₂C

S

11

S

SiPr

O

CHN₂

O

(4), (5), (3)

MeS

O

N₂HC

S

12

Cl

(2), (3)

//

O

Cl

O

(1)

Cl

N₂HC

O

tBu

13

14

O

(2), (3)

//

(1)

Cl

CH₂Cl

CHN₂

CH₂Cl

15

Scheme 1 (1): CH₂N₂; (2): S₈, NEt₃, CaCl₂, DMF; (3): Mel, (4): S₈, NEt₃, DMF; (5): iPrl.

steric hindrance, the reaction of 2-tert-butylterephthaloyl dichloride (13, R¹= tBu, R²=

H) with diazomethane took place with only one acyl chloride function under formation

of 2-tert-butyl-4-diazoacetylbenzoyl chloride 14. The corresponding bis-dithioester was

thus not available. Also, 2-(chloromethyl)diazoacetylbenzene 15, which we obtained from

2-(chloromethyl)benzoyl chloride, did not react in a CAT reaction.

2252

J. VOSS ET AL.

1,2-Bis(bromoacetyl)benzene is a delicate compound, and even its structure is not

quite unequivocal.¹³We have found that a well deﬁned monobromide 16 can be obtained

by selective bromination of 1,2-diacetylbenzene. Its thiolation with subsequent ethylation

led to two unexpected naphthoquinone derivatives 19 and 20 (Scheme 2). We assume the

expected α-oxo-dithiocarboxylate 17 to be formed ﬁrst. Intramolecular cyclization under

elimination of hydrogen sulﬁde could then yield 18, which reacts with either 17 to form 19

or with iodoethane to form 20.

O

−

S

−

(1)

CS₂

CH₃

CH₂Br

CH₃

H₂S

O

18

O

16

17

H₃C

O

S

SEt

17

"S"

EtI

18

−

I

O

19

20

Scheme 2 (1): S_8,NEt_3,DMF.

Furthermore, we have prepared the benzene-1,3,5-tris-dithioglyoxalate esters 22⁶

(6%), 23 (2%), and 24 (0.4%) by thiolation of 1,3,5-tris(bromoacetyl)benzene 21 and

subsequent alkylation (Scheme 3). Expectedly, only low yields were achieved. Although

we have already reported on the EPR spectra of the radical anions and radical trianions

of 22,¹¹we would like to make up for the preparation and full characterization of these

fascinating compounds here.

SR

O

CH₃

CH₂Br

O

S

(2)

(1)

S

H₃C

O

BrH₂C

O

RS

O

CH₃

CH₂Br

O

S

SR

22: R = Me

23: R = Et

24: R = iPr

21

Scheme 3 (1): Br₂, hv; (2): S₈, NEt₃, DMF.

Analogously, biphenyl-4,4^ꢁ-dicarbonyl dichloride was transformed into the bis-

diazoketone 25. Its CAT reaction and methylation yielded 21% of the bis-dithioester 26.

BENZENE-, BIPHENYL-, NAPHTHALENE-BIS(α-OXOETHANEDITHIOATES)

2253

CH₂N₂

CO-Cl

CO-CHN₂

Cl-CO

N₂CH-CO

25

(1) S₈, NEt₃, CaCl₂, DMF

(2) MeI

CO-CS-SMe

25

MeS-CS-CO

26

HBr

CO-CH₂Br

BrCH₂-CO

27

(1) S₈, NEt₃, DMF

(2) EtI

CO-CS-SEt

EtS-CS-CO

27

28

Scheme 4

Since, however, the corresponding ethylation with iodoethane did not give a satisfactory

result, we chose the alternate two-step procedure. First the diazoketone 25 was reacted with

hydrobromic acid¹⁰under formation of the corresponding bis-bromoketone 27, which was

then thiolated and ethylated to yield 36% of the bis-dithioester 28 (Scheme 4).

In the same way, biphenyl-2,2^ꢁ-dicarbonyl dichloride was transformed into the bis-

bromoketone 30 via the bis-diazoketone 29. The thiolation of 30 with subsequent methy-

lation did not, however, yield the desired bis-dithioester 31. Instead, extrusion of one

thiocarbonyl group occurred during the reaction, and only the asymmetric trithioester

1

32 was isolated, the structure of which was unequivocally proven by H and ¹³C NMR

spectroscopy (Scheme 5). A similar extrusion of CS occurs during the reaction of 1,4-

diacetylbenzene with thionyl chloride and subsequent methanolysis, which yields O-methyl

4-methoxycarbonylbenzene-(2-oxoethanethioate) instead of the expected O,O^ꢁ-dimethyl

1,4-benzene-bis-(2-oxoethanethioate).¹⁴

Our priority aim of the present investigation was to synthesize α-oxo-dithioacetate

esters of the naphthalene series. The two isomeric methyl naphthalenedithioglyoxylates 35⁵

and 36^4,5are known from the literature. We have prepared both these compounds by reaction

of α- and β-naphthoyl chloride with diazomethane and subsequent CAT reaction of the

diazoketones 33 and 34, whereas the ethyl (38, 39%) and isopropyl (39, 36%) dithioesters

of the β-naphthoyl series were prepared from 2-acetylnaphthalene via thiolation of 2-

(bromoacetyl)naphthalene 37 (Scheme 6).

Considering the complexity of the thiolation reaction, we expected a marked

decrease of the yields when we started to synthesize naphthalenes with two α-oxo-

dithioacetate substituents.We were met with the ﬁrst surprise when we subjected 1,3-

bis(bromoacetyl)naphthalene 41, which we obtained from the diazoketone 40, to the thi-

olation reaction. Alkylation of the produced salt with iodomethane, iodoethane, or benzyl

bromide did not yield the desired alkyl α-oxo-dithioacetates 42, 43, and 44. Instead, the

2254

J. VOSS ET AL.

CH₂N₂

HBr

CO-Cl

COCH₂Br

Cl-OC

CO-CHN₂

N₂CH-OC

BrCH₂-OC

29

30

(1), (2)

"CS"

//

CO-SMe

MeS-SC-OC

CO-CS-SMe

MeS-SC-OC

31

32

Scheme 5 (1): S₈, NEt₃, DMF; (2): Mel.

R¹

R²

(1)

(2), (3)

33: R¹= CO-CHN₂, R²= H

34: R¹= H, R²= CO-CCHN₂

R¹= CO-Cl, R²= H

R¹= H, R²= CO-Cl

35: R¹= CO-CS-SMe, R²= H

36: R¹= H, R²= CO-CS-SMe

O

SR

(4), (5)

CH₂Br

S

37

38: R = Et

39: R = iPr

Scheme 6 (1): CH₂N₂; (2): S₈, NEt₃, CaCl₂, DMF; (3): Mel; (4) S₈, NEt₃, DMF; (5): RI.

isomeric thieno-annellated naphthalene derivatives 45, 46, and 47 were formed. All ana-

lytical and spectroscopic data are in agreement with the proposed structures. The presence

of a hydroxy group is substantiated by the IR valence band at 3409 cm⁻¹and a signal at

10.40 ppm in the ¹H NMR spectrum of, e.g., 45, whereas the signal due to 2-H is missing.

Signals typical of Ar-SCH₃groups appear at δ = 2.45 ppm and δ = 21.72 ppm in the ¹H

and ¹³C NMR spectra of 45. Only one C O and C S ¹³C NMR signal each is found at

δ = 190.5 and 230.5 ppm instead of two different ones expected for the bis-1,3-dithioester

42. Corresponding spectroscopic results are observed for 46 and 47 (see the Experimental

section). They indeed do not unequivocally exclude isomeric structures that could arise

from intramolecular thiophene annellation by 3→4 (48) or 3→2 ring closure reactions,

and we were not able to grow suitable crystals for an X-ray crystallographic structure

determination. But fortunately, an NOE effect between the OH proton and the proton in the

8-position of the naphthalene moiety of 45 was observed. The assignment of 8-H (9-H of

45) is deﬁnite due to its chemical shift δ = 9.35 ppm and the doublet splitting J_H7,H8= 8.6

Hz, whereas the possible isomeric naphthothiophenes, e.g., 48, could only exhibit NOEs

between the OH proton and 2-H, or 4-H (singlet at δ = 8.10 ppm) of 48. The structures of

BENZENE-, BIPHENYL-, NAPHTHALENE-BIS(α-OXOETHANEDITHIOATES)

2255

O

Cl

O

CHN₂

CH₂Br

O

(2)

CHN₂

(1)

Cl

CH₂Br

41

40

O

SR

O

S

(3), (4)

//

42: R = Me

43: R = Et

S

41

44: R = CH₂Ph

SR

O

SR

OH

SR

HO

9

S

H

S

(3), (4)

S

41

4

H

SR

S

O

45: R = Me

46: R = Et

47: R = CH₂Ph

SR

48: R = Me

Scheme 7 (1): CH₂N₂; (2): HBr; (3): S₈, NEt₃, DMF; (4) RI.

45 and, by analogy, also of 46 and 47 can therefore be regarded as deﬁnitive. The formation

of the thiophene ring can be understood by assuming ﬁrst an intramolecular nucleophilic

attack of the dithiocarboxylate group at the electron-deﬁcient C-2 (two neighboring car-

bonyl groups!) of the naphthalene ring and concomitant 1,4-migration of the proton 2-H

from carbon to oxygen under formation of the aromatic thiophene ring (Scheme 7).

1,4-Bis(diazoacetyl)naphthalene 49 was easily available from naphthalene-1,4-

dicarbonyl dichloride. Its conversion into dimethyl 1,4-naphthalenedithioglyoxalate 58 by

the CAT reaction failed. The two-step procedure via the intermediate dibromoketone 52

was, however, successful (Scheme 8).

Similar results were observed in the 1,5-, 1,6-, and 1,7-naphthalene series. The

bis-diazoketones 50 and 51 were not suitable for the CAT reaction, but 1,5-, 1,6-, and

1,7-bis(bromoacetyl)naphthalenes 53, 54, and 55, which we prepared by bromination of

1,5- and 1,6-diacetylnaphthalene 56 and 57 or reaction of 1,7-bis(diazocetyl)naphthalene

51 with hydrogen bromide, could be successfully thiolated to form the dimethyl (59, 61,

63) and diethyl dithioesters (60 and 62), although with only moderate yields (Scheme 8).

1,8-Diacetylnaphthalene gave only decomposition products when we tried to bromi-

nate the methyl groups under various conditions.

2256

J. VOSS ET AL.

CO-CHN₂

CO-Cl

R⁴

R³

R⁴

(1)

R³

R¹

R²

R¹

R²

R¹= CO-Cl, R²−R⁴= H

49: R¹= CO-CHN₂, R²−R⁴= H

50: R¹= R³= R⁴= H, R²= CO-CHN₂

51: R¹−R³= H, R⁴= CO-CHN₂

R¹= R³= R⁴= H, R²= CO-Cl

R¹−R³= H, R⁴= CO-Cl

CO-CH₂Br

CO-CH₃

R⁴

(2)

(3)

49, 51

R³

R¹

R²

R¹

R²

52: R¹= CO-CH₂Br, R²−R⁴= H

56: R¹= R³= R⁴= H, R²= CO-CH₃

57: R¹= R²= R⁴= H, R³= CO-CH₃

53: R¹= R³= R⁴= H, R²= CO-CH₂Br

54: R¹= R²= R⁴= H, R³= CO-CH₂Br

55: R¹−R³= H, R⁴= CO-CH₂Br

SR⁵

S

O

R⁴

(4), (5)

52, 53, 54, 55

R³

R²

R¹

58: R¹= CO-CS-SR⁵, R²= R⁴= H, R⁵= Me

59: R¹= R³= R⁴= H, R²= CO-CS-SR⁵, R⁵= Me

60: R¹= R³= R⁴= H, R²= CO-CS-SR⁵, R⁵= Et

61: R¹= R²= R⁴= H, R³= CO-CS-SR⁵, R⁵= Me

62: R¹= R²= R⁴= H, R³= CO-CS-SR⁵, R⁵= Et

63: R¹−R³= H, R⁴= CO-CS-SR⁵, R⁵= Me

Scheme 8 (1): CH₂N₂; (2): HBr; (3): Br₂; (4): S₈, NEt₃, DMF; (5): R⁵l.

Furthermore, we synthesized the ﬁve bis-dithioesters 68, 69, 70, 71, and 72 of 2,6- and

2,7-naphthalenediglyoxylic acid via the bis-diazoketones 64 and 65 and bis-bromoketones

66 and 67 (Scheme 9).

We performed single crystal X-ray structural analyses of 7 (Figure 1) and 71

(Figure 2). Selected bond lengths, bond angles, and torsion angles are compiled in Table I.

The conformations of the two compounds are slightly different. A torsion angle of

16.0^◦between the plane of the arene ring and the ketone plane (C2/C1/C11/O1) of 7 is

found compared with only 5.3^◦for the corresponding torsion angle of 71 and 21.7^◦for

the related methyl benzene-α-oxodithioacetate.¹⁵The arrangement of the dithioester and

the ketone planes, on the other hand, is far from coplanar, irrespective of the loss of the

BENZENE-, BIPHENYL-, NAPHTHALENE-BIS(α-OXOETHANEDITHIOATES)

2257

R²

R¹

R²

R¹

CO-Cl

(1)

CO-CHN₂

64: R¹= CO-CHN₂, R²= H

65: R¹= H, R²= CO-CHN₂

R¹= CO-Cl, R²= H

R¹= H, R²= CO-Cl

R²

3

R²

CO-CS-S

CO-CH₂Br

R

(2)

(3), (4)

R¹

66: R¹= CO-CH₂Br, R²= H

67: R¹= H, R²= CO-CH₂Br

68: R¹= CO-CS-SMe, R²= H, R³= Me

69: R¹= CO-CS-SEt, R²= H, R³= Me

70: R¹= CO-CS-SCH₂Ph, R²= H, R³= CH₂Ph

71: R¹= H, R²= CO-CS-SMe, R³= Me

72: R¹= H, R²= CO-CS-SEt, R³= Et

Scheme 9 (1): CH₂N₂; (2): HBr; (3): S₈, NEt₃, DMF; (4): R₃l.

resonance interaction between the two parts. Torsion angles O C C S of 54.5^◦(7), 73.3^◦

(71), and 69.4^◦(methyl benzene-α-oxodithioacetate) are observed. This is obviously due

to steric repulsion between the sulfur atoms and the ortho- (7) and peri- (71) protons at the

arene rings. Not unexpectedly, the two thiocarbonyl groups of 71 are rotated into opposite

directions, which anti-orientation minimizes the total dipole moment of the molecule.

The direct thiolation of activated methyl groups under formation of dithioesters has

been studied by Hoepping and Mayer.⁶They used diethoxydisulfane in the presence of

potassium tert-butoxide as a base to prepare α-oxodithiocarboxylates from acetophenones.

In this way, they obtained 7 from 1,4-diacetylbenzene, and 22 in addition to two related

Figure 1 ORTEP view of the X-ray diffraction structure of 7. Since the molecule exhibits a center of symmetry,

the numbering is given for only one half of the atoms. Thermal ellipsoids are drawn at the 50% probability level.

Hydrogen atoms are not shown.

2258

J. VOSS ET AL.

Figure 2 ORTEP view of the X-ray diffraction structure of 71 with atom numbering. Thermal ellipsoids are

drawn at the 50% probability level. Hydrogen atoms are not shown.

bis-α-oxo-dithiocarboxylates from 1,3,5-triacetylbenzene. Certain methylarenes could also

be transformed into the corresponding arenecarbodithioates.

We have studied the reaction of methyl and methylene compounds under the CAT

conditions. When 1,4-diacetylbenzene was subjected to the CAT reaction, 7 was formed

with 80% yield (Scheme 10). 2,3-Dimethylchromone 73 was totally resistant to thiolation

in the absence of calcium chloride. However, the addition of the promoter led to a clean

and selective reaction under formation of 92% of the dithioester 74 (Scheme 10).

Table I Selected bond lengths d (pm), angles α (^◦), and torsion angles θ (^◦) in 7, 71, and 74

7

71

74

d

149.7

—

C1 C11

C11 C12

C11 O1

C12 S1

C12 S2

S2 C23

149.1

151.4

120.4

161.7

172.1

178.1

α

C2 C21

C21 C22

C21 O2

C22 S1

C22 S2

S2 C23

148.9

151.3

120.6

160.1

169.4

181.0

α

C2 C21

—

C21 S21

C21 S22

C22 S22

—

162.7

170.7

179.0

α

S1 C12 S2

S1 C12 C11

S2 C12 C11

C12 S2 C23

128.5

120.6

110.7

103.3

θ

S1 C22 S2

128.9

118.9

112.3

102.2

θ

S21 C21 S22

S21 C21 C2

S22 C21 C2

C22 S22 C21

128.3

119.6

112.1

102.9

θ

S1 C22 C21

S2 C22 C21

C22 S2 C23

C2 C1 C11 O1

O1 C11 C12 S2

S1 C12 S2 C23

16.0

54.5

3.2

C1 C2 C21 O2

O2 C21 C22 S2

S1 C22 S2 C23

5.3

C3 C2 C21 S21

—

S21 C21 S22 C22

−102.1

75.3

−2.9

—

2.3

BENZENE-, BIPHENYL-, NAPHTHALENE-BIS(α-OXOETHANEDITHIOATES)

2259

O

S

CH₃

(1), (2)

H₃C

S

H₃C

S

O

7

O

CH₃

(1), (2)

O

CS-SCH₃

S

73

74

CH₂CO₂H

CH₃

(1), (2)

- 2 CO₂

S

HO₂CCH₂

H₃C

S

75

X

CH₂X

(1)

S

X

76: X = CO₂Et

77: X = CN

Scheme 10 (1): S₈, NEt₃, CaCl₂, DMF; (2): Mel.

The reason for the activating effect of calcium chloride is not well understood, and

even the mechanism of the thiolation reaction itself is not known in detail.^6,16Obviously,

ﬁrst the cyclic sulfur molecule is cleaved by triethylamine under formation of open-chained

sulfur species. These polysulﬁde zwitter-ions may then react both as nucleophiles or elec-

trophiles, which attack the α-position of the carbonyl compound. In the absence of sulfur,

calcium chloride does not react with diazoketones. In a control experiment, which we have

performed, the diazoketone was recovered quantitatively from the reaction mixture. It is

probable that the electrophilicity of the sulfur species is increased due to ion pairing between

calcium ions and the anionic terminal of the sulfur chain. A similar effect has been observed

for the base-catalyzed cleavage of sodium S-benzylthiosulfates to thioaldehydes.¹⁷

The structure of 74 is obvious from its analytical and spectroscopic data. It was

corroborated by an X-ray structural analysis (Figure 3). Thus, the reagent unequivocally

attacks the methyl group in the 2-position of 73, which, due to the vinylogy principle, should

exhibit a higher C-H-acidity as compared with the methyl substituents in the 3-position.

After a prolonged reaction time (seven days at ambient temperature), the thiolation of

1,4-benzenediacetic acid with subsequent methylation ﬁnally resulted in the formation of a

2260

J. VOSS ET AL.

Figure 3 ORTEP view of the X-ray diffraction structure of 74 with atom numbering. Thermal ellipsoids are

drawn at the 50% probability level. Hydrogen atoms are not shown.

product, which unexpectedly turned out to be dimethyl tetrathioterephthalate 75 (Scheme

10). In this case, the addition of calcium chloride did not accelerate the reaction. Obviously,

ﬁrst an attack of the electrophilic sulfur species at the activated methylene groups occurs,

which is followed by decarboxylation of the intermediate in the basic reaction medium

(Scheme 10). Diethyl 1,2-benzenediacetate and 1,2-benzenediacetonitrile are attacked at

the methylene groups, too. Formally, one sulfur atom is simply introduced under elimination

of hydrogen sulﬁde and intramolecular cyclization to form the interesting, bright yellow,

and ﬂuorescing benzo[c]thiophene derivatives 76¹⁸and 77 (Scheme 10).

In pilot experiments, we have studied the transformation of the α-oxo-dithioesters

7 and 22 into the corresponding α-oxo-thionoesters. Acid-catalyzed transesteriﬁcation

failed. The reaction with sodium methoxide led, however, to the desired products 78 and

80, although with low yields. Only trace amounts of the thiono-ethylester 79 were formed

(Scheme 11).

CONCLUSION

The base-catalyzed reaction of diazoketones with elemental sulfur is signiﬁcantly

accelerated in the presence of anhydrous calcium chloride (CAT reaction). Bi- and trifunc-

tional α-oxo-dithioesters, in particular in the naphthalene series, can be obtained by the CAT

reaction or by thiolation of the corresponding bromoketones with subsequent alkylation.

In certain cases, intramolecular cyclization under formation of annellated thiophenes oc-

curs. Reaction of the α-oxo-dithioesters with sodium alkoxides leads to the corresponding

α-oxo-thionoesters.

BENZENE-, BIPHENYL-, NAPHTHALENE-BIS(α-OXOETHANEDITHIOATES)

2261

O

SMe

OR

NaOR

S

SMe

RO

O

7

78: R = Me

79: R = Et

SMe

S

OMe

O

S

NaOMe

S

O

MeS

MeO

O

S

SMe

S

OMe

22

80

Scheme 11

EXPERIMENTAL

Corrected melting points (mp) were determined on an Electrothermal apparatus. IR

spectra (ν in cm⁻¹, KBr pellets or ﬁlms) were measured on a Perkin-Elmer FT-IR 1720X

spectrometer. UV/Vis spectra [λ_maxin nm, (lgε), MeOH] were recorded on a Perkin-

Elmer 200 spectrometer. NMR spectra (δ in ppm vs. SiMe₄, J in Hz) were measured in

CDCl₃(if not stated otherwise) on Bruker AC 250 P (¹H: 250 MHz, ¹³C: 63 MHz) and

Bruker WM 400 (¹H: 400 MHz, ¹³C: 100.6 MHz) spectrometers. H,H- or H,C-COSY

experiments were performed when required. Mass spectra (EI, 70 eV; m/z; rel. intensities

in% of the most intensive peak) were measured on a Varian MAT spectrometer. Thin layer

chromatography (TLC) was performed on silica-coated Al foils (Kieselgel F₂₅₄, Merck,

Darmstadt, Germany). Column chromatography (CC) was performed on Kieselgel 60

(70–230 mesh, Merck, Darmstadt, Germany).

X-Ray Structure Analyses

The crystal data of 7, 71, and 74, and a summary of the experimental details are

reported in Table II. The structures were solved by the direct method MULTAN¹⁹(7 and

74) or SHELXTL Plus²⁰(71). All non-hydrogen atoms were localized. After reﬁnement

of these parameters, the hydrogen atoms were localized by differential Fourier synthesis.²¹

They are not shown in Figures 1–3 for the sake of clarity. The ﬁnal reﬁnement was performed

by least squares methods. In the case of 7, an experimental correction for absorption²²was

performed in addition to the usual Lorentz correction for polarization. Crystallographic data

have been deposited with the Cambridge Crystallographic Data Centre as supplementary

publications No. CCDC-746652 (7), No. CCDC-746651 (71), and No. CCDC 746650

(74). Copies of the data can be obtained free of charge upon application to CCDC, 12

2262

J. VOSS ET AL.

Table II Crystal data and structure reﬁnement for 7, 71, and 74

Compound

Diffractometer

Radiation

7

71

74

CAD 4

Enraf Nonius

Cu-K_α

Syntex P2₁

CAD 4-SDP

Enraf Nonius

Mo-K_α

λ = 0.71073 Å

298

C₁₆H₁₂O₂S₄

364.52

λ = 1.54184 Å

λ = 0.71073 Å

Temperature [K]

Empirical formula

Formula weight

Crystal system

Space group

a [pm]

298

C

₁₂H₁₀O₂S₄

314.47

Monoclinic

C2/c

1424.5 (1)

433.55 (3)

2357.0 (2)

90.00

C₁₂H₁₀O₂S₂

250.39

Monoclinic

P2₁/n

898.2 (2)

1064.2 (1)

1267.9 (1)

90.00

Triclinic

P-1

904.0 (2)

968.4 (2)

1086.2 (2)

66.99 (2)

78.04 (2)

88.74 (2)

0.854 (3)·10⁹

2

b [pm]

c [pm]

α [^◦]

β [^◦]

100.67 (1)

90.00

96.08 (2)

90.00

γ [^◦]

V [pm³]

1.430·10⁹

1.185·10⁹

Z

4

ρ_calcd.[g cm⁻³

]

1.46

59.6

648

2/70

1.42

5.58

376

2/25

1.40

4.19

520

2/24

µ [cm⁻¹

F(000)

]

θ-limits [^◦]

h/k/l-limits

0, 17/0, 5/–28, 28

1406

0, 10/0, 11/–14, 14

1606

Reﬂections collected (I > 3σ_I)

Number of parameters

3042

201

104

147

R-Index

R_w-Index (w = σ_I

0.036

0.030

0.0707

0.067

0.031

0.028

−2

)

Union Road, Cambridge CB2 IEZ, UK [Fax: (international) ++44–1223/336-033; E-mail:

deposit@ccdc.cam.uk].

Preparations

A ﬁvefold stoichiometric amount (related to the respective acid chloride as substrate)

of N-methyl-N-nitrosourea was used as starting material for the preparation of ethereal

solutions of diazomethane and their reaction with the acid chlorides to form the diazoketones

according to the literature.¹⁰

Warning: Diazomethane is explosive, carcinogenic, and toxic. Diazoketones decom-

pose upon heating under explosion. α-Haloketones are lacrimatory. Suitable precautions

must be taken while working with these compounds!

Please see the Supplemental Materials (available online) for complete spectroscopic

data.

Diazoketones¹⁰

1,3-Bis(diazoacetyl)-2-methylbenzene (1). Thereactionof2-methylisophthaloyl

dichloride²³(4.8 g, 0.022 mol) in diethyl ether (100 mL) with CH₂N₂gave 1 as a yellow

powder (2.1 g, 42%), mp 113–115^◦C. ¹H NMR (250 MHz): 2.50 (s, 3 H, CH₃), 5.50 (s, 2

H, CHN₂), 7.30 (t, J = 8.9, 1 H, 5-H), 7.42 (d, J = 9.0, 2 H, 4/6-H).

BENZENE-, BIPHENYL-, NAPHTHALENE-BIS(α-OXOETHANEDITHIOATES)

2263

1,3-Bis(diazoacetyl)-4-methylbenzene (2). Thereactionof4-methylisophthaloyl

dichloride²⁴(10.8 g, 0.050 mol) in diethyl ether (180 mL) with CH₂N₂gave 2 as a yellow

1

powder (8.8 g, 77%), mp 120–122^◦C. H NMR (250 MHz): 2.55 (s, 3 H, CH₃), 5.62 (s,

1 H, 1-CHN₂), 5.90 (s, 1 H, 3-CHN₂), 7.30 (d, J = 8.0, 1 H, 5-H), 7.62 (d, J = 8.0, 1 H,

6-H), 7.82 (s, 1 H, 2-H). ¹³C NMR (63 MHz): 20.37 (CH₃), 54.32 (CHN₂), 125.56 (C-5),

128.61 (C-6), 131.92 (C-2), 134.34 (C-4), 137.86 (C-1), 142.07 (C-3), 184.98 (C O).

Anal. calcd. for C₁₁H₈N₄O₂(228.21): C, 57.89; H, 3.53; N, 24.55; Found: C, 57.91; H,

3.47; N, 23.58.

1,4-Bis(diazoacetyl)-2-methylbenzene (5). Thereactionof2-methylterephtha-

loyl dichloride²⁵(6.0 g, 0.027 mol) in diethyl ether (100 mL) with CH₂N₂gave 5 as a yellow

powder (3.1 g, 52%), mp 126–130^◦C. ¹H NMR (250 MHz): 2.50 (s, 3 H, CH₃), 5.50 (s, 1

H, 1-CHN₂), 5.90 (s, 1 H, 4-CHN₂), 7.30–7.70 (m, 3 H, H_Ar).

1,4-Bis(diazoacetyl)-2,5-dimethylbenzene (6). The reaction of 2,5-

dimethylterephthaloyl dichloride^25,26(6.3 g, 0.027 mol) in diethyl ether (270 mL)

1

with CH₂N₂gave 6 as yellow leaﬂets (5.6 g, 89%), mp 155^◦C (decomp.). H NMR (250

MHz): 2.40 (s, 6 H, CH₃), 5.55 (s, 2 H, CHN₂), 7.72 (s, 2 H, 3/6-H). ¹³C NMR (63 MHz):

19.84 (CH₃), 56.50 (CHN₂), 129.99 (C-3/6), 134.02 (C-2/5), 139.53 (C-1/4), 189.06

(C O).

2-tert-Butyl-4-(diazoacetyl)benzoyl chloride (14). Into a stirred, boiling solu-

tion of 2-tert-butyl-1,4-dimethylbenzene²⁷(8.2 g, 0.050 mol) in pyridine (50 mL), KMnO₄

(38 g, 0.24 mol) was added in small portions. The mixture was stirred at 20^◦C for 14 h. The

MnO₂was ﬁltered off and washed with hot H₂O (30 mL). The ﬁltrates were concentrated to

10 mL under vacuum. Conc. aq. HCl (2 mL) was added under cooling. The precipitated acid

was washed with ice-cold H₂O, dissolved in NaOH, and again precipitated with dil. HCl

to yield 2-tert-butylterephthalic acid^28,29(6.8 g, 61%) as white crystals, mp 240–246^◦C.

This acid (6.4 g, 0.029 mol) and PCl₅(14.0 g, 0.074 mol) were heated to 100^◦C

until the evolution of HCl ceased (ca. 6 h). The POCl₃was removed under vacuum. The

residue was dissolved in ligroin, ﬁltered, and concentrated in a vacuum to yield 2-tert-

butylterephthaloyl dichloride²⁸13 (6.0 g, 81%) as a red-brown oil.

The reaction of 13 (1.1 g, 0.004 mol) in diethyl ether (45 mL) with CH₂N₂gave 14

as a yellow oil (1.0 g, 86%). ¹H NMR (250 MHz): 1.45 (s, 9 H, CH₃), 5.90 (s, 1 H, CH),

7.60 (m, 2 H, H_Ar), 7.95 (m, 1 H, H_Ar).

2-(Chloromethyl)-1-(diazoacetyl)benzene (15). The reaction of 2-

(chloromethyl)benzoyl chloride³⁰(28.0 g, 0.14 mol) in diethyl ether (150 mL with

diazomethane) gave 15 as yellow crystals (6.0 g, 21%), mp 40–42^◦C (lit.³⁰: bp

135^◦C/Torr). ¹H NMR (250 MHz): 4.90 (s, 2 H, CH₂), 5.70 (s, 1 H, CHN₂), 7.25–7.75 (m,

4 H, 3/4/5/6-H). ¹³C NMR (63 MHz): 43.95 (CH₂), 56.74 (CHN₂), 127.56 (C-5), 128.45

(C-6), 131.09 (C-4), 131.44 (C-1), 136.28 (C-3), 137.04 (C-2), 192.18 (C O). Anal.

calcd. for C₉H₇ClN₂O (194.62): C, 55.54; H, 3.62; Cl, 18.22; N, 14.39; Found: C, 55.64;

H, 3.55; Cl, 18.13; N, 14.24.

4,4^ꢀ-Bis(diazoacetyl)biphenyl (25). The reaction of biphenyl-4,4^ꢁ-dicarbonyl

dichloride³¹(6.0 g, 0.021 mol) in diethyl ether (150 mL) with CH₂N₂gave 25 as a yellow

1

powder (5.6 g, 89%), mp 163–168^◦C (lit.³¹mp 165^◦C). H NMR (250 MHz): 5.95 (s, 2

H, CHN₂), 7.60–7.75 (m, 4 H, 2/2^ꢁ/6/6^ꢁ-H), 7.80–7.90 (m, 4 H, 3/3^ꢁ/5/5^ꢁ-H). ¹³C NMR (63

MHz): 54.36 (CHN₂), 127.40 (C-2/2^ꢁ/6/6^ꢁ), 127.77 (C-3/3^ꢁ/5/5^ꢁ), 136.19 (C-1/1^ꢁ), 144.01

(C-4/4^ꢁ), 185.15 (C O).

2,2^ꢀ-Bis(diazoacetyl)biphenyl (29). The reaction of biphenyl-2,2^ꢁ-dicarbonyl

dichloride^32,33(18.4 g, 0.066 mol) in diethyl ether (500 mL) with CH₂N₂gave 29 as a

2264

J. VOSS ET AL.

yellow powder (18.0 g, 94%), mp 129–130^◦C [lit.³³: mp 134–135^◦C (benzene, decomp.)].

¹H NMR (250 MHz): 5.50 (s, 2 H, CHN₂), 7.10–7.20 (m, 2 H, 4/4^ꢁ-H), 7.35–7.40 (m, 4 H,

5/5^ꢁ/6/6^ꢁ-H), 7.55–7.60 (m, 2 H, 3/3^ꢁ-H). ¹³C NMR (100 MHz): 56.82 (CHN₂), 127.56 (C-

5/5^ꢁ), 127.88 (C-4/4^ꢁ), 130.72 (C-6/6^ꢁ), 131.69 (C-2/2^ꢁ), 137.75 (C-1/1^ꢁ), 139.31 (C-2/2^ꢁ),

189.46 (C O).

1-(Diazoacetyl)naphthalene (33). The reaction of 1-naphthoyl chloride (Fluka,

10.0 g, 0.052 mol) in diethyl ether (52 mL) with CH₂N₂gave 33 (9.3 g, 84%) as a yellow

powder, mp 52^◦C (lit.³⁴: 55^◦C). ¹H NMR (250 MHz): 5.70 (s, 1 H, CHN₂), 7.40–7.62 (m,

4 H, H_Ar), 7.82–8.00 (m, 2 H, H_Ar), 8.50 (d, J = 7.4, 1 H, 2-H). ¹³C NMR (63 MHz): 57.22

(CHN₂), 124.50 (C-6), 125.41 (C-7), 126.35 (C-3), 126.54 (C-5), 127.53 (C-4), 128.34

(C-8), 129.80 (C-4a), 131.88 (C-2), 133.85 (C-8a), 135.53 (C-1), 189.56 (C O).

2-(Diazoacetyl)naphthalene (34). The reaction of 2-naphthoyl chloride (Fluka,

15.0 g, 0.078 mol) in diethyl ether (80 mL) with CH₂N₂gave 34 (9.6 g, 62%) as yellow

crystals, mp 82–84^◦C [lit.³⁵: 73–75^◦C (hexane/Et₂O)]. ¹H NMR (250 MHz): 6.05 (s, 1 H,

CHN₂), 7.50–7.61 (m, 2 H, H_Ar), 7.80–7.92 (m, 4 H, H_Ar), 8.25 (s, 1 H, 1-H). ¹³C NMR

(63 MHz): 54.36 (CHN₂), 123.06 (C-6), 126.87 (C-7), 127.62 (C-5), 127.80 (C-8), 128.21

(C-4), 128.56 (C-3), 129.34 (C-1), 132.55 (C-4a), 134.02 (C-8a), 135.44 (C-2), 186.20

(C O). Anal. calcd. for C₁₂H₈N₂O (196.20): C, 73.45; H, 4.10; N, 14.27; Found: C, 73.91;

H, 4.18; N, 13.79.

1,3-Bis(diazoacetyl)naphthalene (40). Naphthalene-1,3-dicarboxylic acid³⁶

(5.0 g, 0.023 mol) and PCl₅(11.4 g, 0.055 mol) were heated to reﬂux for 6 h. The POCl₃

was removed in a vacuum to yield naphthalene-1,3-dicarbonyl dichloride (5.20 g, 89%) as

yellowish needles, mp 106^◦C (ligroin). Anal. calcd. for C₁₂H₆Cl₂O₂(253.08): C, 56.95;

H, 2.39; Cl, 28.02; Found: C, 56.94; H, 2.18; Cl, 27.95.

Reaction of this acid chloride (5.20 g, 0.021 mol) in diethyl ether (50 mL) with

1

CH₂N₂gave 40 as a yellow powder (4.30 g, 78%), mp 127^◦C (decomp.). H NMR (250

MHz): 5.85 (s, 1 H, 3-CHN₂), 6.10 (s, 1 H, 1-CHN₂), 7.50–7.70 (m, 2 H, 6/7-H), 7.95

(d, J = 8.0, 1 H, 5-H), 8.05 (s, 1 H, 4-H), 8.15 (s, 1 H, 8-H), 8.55 (s, 1 H, 2-H). ¹³C

NMR (63 MHz): 54.67 (3-CHN₂), 57.61 (1-CHN₂), 123.03 (C-6), 125.72 (C-7), 127.56

(C-5), 129.74 (C-8), 129.82 (C-4), 130.80 (C-4a), 131.80 (C-2), 132.70 (C-8a), 133.16

(C-3), 136.16 (C-1), 185.06 (3-C O), 191.15 (1-C O). MS: 264 (3) [M⁺], 208 (33) [M⁺

–2 N₂], 195 (27) [M⁺CHN₂, N₂], 167 (15) [M⁺COCHN₂, N₂], 152 (100) [C₁₂H₈⁺],

139 (34) [C₁₁H₇⁺], 126 (15) [M⁺2 COCHN₂], 76 (24) [C₆H₄⁺], 63 (26). Anal. calcd.

for C₁₄H₈N₄O₂(264.24): C, 63.64; H, 3.05; N, 21.20; Found: C, 63.35; H, 3.03; N,

19.54.

1,4-Bis(diazoacetyl)naphthalene (49). The reaction of naphthalene-1,4-

dicarbonyl dichloride³⁷(6.60 g, 0.026 mol) in diethyl ether (120 mL) with CH₂N₂gave

49 as a light yellow powder (5.95 g, 88%), mp 155–157^◦C. ¹H NMR (250 MHz): 5.70 (s,

2 H, CHN₂), 7.55–7.65 (m, 4 H, 5/6/7/8-H), 8.43 (bs, 2 H, 2/3-H). ¹³C NMR (63 MHz):

57.80 (CHN₂), 124.94 (C-6/7), 125.46 (C-5/8), 127.70 (C-2/3), 129.48 (C-4a/8a), 137.94

(C-1/4), 188.84 (C O). Anal. calcd. for C₁₄H₈N₄O₂(264.24): C, 63.64; H, 3.05; N, 21.20;

Found: C, 63.40; H, 2.97; N, 20.46.

1,5-Bis(diazoacetyl)naphthalene (50). The reaction of naphthalene-1,5-

dicarbonyl dichloride³⁸(5.20 g, 0.021 mol) in diethyl ether (50 mL) with CH₂N₂gave 50

as a yellow powder (4.50 g, 83%), mp 165^◦C. ¹H NMR (250 MHz): 5.70 (s, 2 H, CHN₂),

7.55–7.80 (m, 6 H, H_Ar).

1,7-Bis(diazoacetyl)naphthalene (51). The reaction of naphthalene-1,7-

dicarbonyl dichloride³⁹(1.40 g, 0.0060 mol) in diethyl ether (80 mL) with CH₂N₂gave

BENZENE-, BIPHENYL-, NAPHTHALENE-BIS(α-OXOETHANEDITHIOATES)

2265

51 as a yellow powder (1.20 g, 86%), mp 156–158^◦C. ¹H NMR (250 MHz): 5.80 (s, 1 H,

7-CHN₂), 6.15 (s, 1 H, 1-CHN₂), 7.10–7.20 (m, 2 H, H_Ar), 7.90–8.10 (m, 3 H, H_Ar), 8.95 (s,

1 H, 8-H). ¹³C NMR (63 MHz): 54.69 (CHN₂), 124.08 (C-3), 125.14 (C-4), 126.74 (C-5),

126.85 (C-6), 129.04 (C-2), 131.94 (C-8), 135.76 (C-7), 135.87 (C-1), 182.93 (C O). MS:

252 (13), 237 (31), 236 (3) [M⁺N₂], 208 (47) [M⁺2 N₂], 195 (26) [M⁺N₂, –CHN₂],

180 (13) [M⁺2 N₂, CO], 167 (12) [M⁺COCHN₂, N₂], 152 (100) [C₁₂H₈⁺], 139 (37)

[C₁₁H₇⁺], 126 (14) [M⁺2 COCHN₂], 76 (27) [C₆H₄⁺], 63 (28).

2,6-Bis(diazoacetyl)naphthalene (64). The reaction of naphthalene-2,6-

dicarbonyl dichloride⁴⁰(13.2 g, 0.052 mol) in diethyl ether (100 mL) with CH₂N₂gave 64

as a yellow powder (10.0 g, 78%), mp 200^◦C (decomp.). ¹H NMR (250 MHz): 5.30 (s, 2

H, CHN₂), 7.90–8.30 (m, 4 H, H_Ar), 8.05 (s, 2 H, 1/5-H).

2,7-Bis(diazoacetyl)naphthalene (65). The reaction of naphthalene-2,7-

dicarbonyl dichloride^40,41(5.4 g, 0.022 mol) in diethyl ether (100 mL) with CH₂N₂gave

65 as a yellow powder (4.9 g, 87%), mp 200^◦C (decomp.). ¹H NMR (250 MHz): 6.10 (s, 2

H, CHN₂), 7.90–8.00 (m, 4 H, 3/4/5/6-H), 8.30 (s, 2 H, 1/8-H). ¹³C NMR (63 MHz): 54.68

(CHN₂), 125.36 (C-4/5), 128.59 (C-3/6), 128.75 (C-1/8), 131.77 (C-4a), 131.81 (C-8a),

137.24 (C-2/7), 185.60 (C O). Anal. calcd. for C₁₄H₈N₄O₂(264.24): C, 63.64; H, 3.05;

N, 21.20; Found: C, 63.35; H, 3.02; N, 20.40.

Bromoketones from Diazoketones¹⁰

1,4-Bis(bromoacetyl)-2-methylbenzene. The reaction of 5 (1.10 g, 0.005 mol)

with aq. HBr (47%, 43 mL) in diethyl ether (500 mL) gave the bromoketone as a white

powder (0.22 g, 14%), mp 92–96^◦C. ¹H NMR (250 MHz): 2.55 (s, 3 H, CH₃), 4.38 (s, 2 H,

CH₂), 4.42 (s, 2 H, CH₂), 7.70–7.90 (m, 3 H, 3/5/6-H). ¹³C NMR (63 MHz): 21.04 (CH₃),

30.63 (CH₂), 33.35 (CH₂), 126.27 (C-5), 128.74 (C-6), 132.82 (C-3), 136.14 (C-2), 139.28

(C-4), 138.82 (C-1), 190.70 (C O), 194.21 (C O).

1,4-Bis(bromoacetyl)-2,5-dimethylbenzene. The reaction of 6 (2.7 g, 0.012

mol) with aq. HBr (47%, 60 mL) in diethyl ether (100 mL) gave the bromoketone as a

yellowish-white powder (0.15 g, 4%), mp 136–140^◦C. ¹H NMR (250 MHz): 2.50 (s, 6 H,

CH₃), 4.40 (s, 4 H, CH₂), 7.50 (s, 2 H, 3/6-H). ¹³C NMR (63 MHz): 20.60 (CH₃), 33.34

(CH₂), 131.84 (C-3/6), 136.54 (C-2/5), 137.63 (C-1/4), 194.05 (C O).

4,4^ꢀ-Bis(bromoacetyl)biphenyl (27). The reaction of 25 (14.4 g, 0.050 mol)

with aqu. HBr (47%, 250 mL) in diethyl ether (600 mL) gave 27 as a yellow powder (16.3

g, 83%), mp 211–215^◦C [lit.⁴²: mp 220–222^◦C (benzene, decomp.)]. ¹H NMR (250 MHz):

4.50 (s, 4 H, CH₂), 7.75 (d, J = 8.3, 4 H, 2/2^ꢁ/6/6^ꢁ-H), 8.10 (d, J = 8.2, 4 H, 3/3^ꢁ/5/5^ꢁ-H). ¹³

C

NMR (63 MHz): 30.59 (CH₂), 127.14 (C-2/2^ꢁ/6/6^ꢁ), 129.11 (C-3/3^ꢁ/5/5^ꢁ), 133.61 (C-4/4^ꢁ),

145.62 (C-1/1^ꢁ), 190.61 (C O). MS: 396 (10) [M⁺], 394 (4) [M⁺], 303 (81) [M⁺CH₂Br],

301 (100) [M⁺CH₂Br], 257 (11), 180 (23) [M⁺CH₂Br, COCH₂Br], 166 (37), 165

(66), 152 (35) [M⁺2 COCH₂Br], 151 (45), 126 (9), 104 (10) [C₇H₄O⁺], 76 (10) [C₆H₄⁺],

63 (28).

2,2^ꢀ-Bis(bromoacetyl)biphenyl (30). The reaction of 29 (3.0 g, 0.010 mol) with

aq. HBr (47%, 50 mL) in diethyl ether (500 mL) gave 30 as yellow crystals (2.7 g, 69%),

1

mp 87–88^◦C (EtOH) [lit.⁴³: 100–102^◦C (MeOH)]. H NMR (250 MHz): 4.06 (A-part of

AB-system, 2 H, J = 11.3, CH₂), 4.32 (B-part of AB-system, 2 H, J = 11.3, CH₂), 7.20

(m, 2 H, 5/5^ꢁ-H), 7.40–7.60 (m, 4 H, 4/4^ꢁ/6/6^ꢁ-H), 7.70–7.75 (m, 2 H, 3/3^ꢁ-H), ¹³C NMR

(63 MHz): 33.68 (CH₂), 128.08 (C-4/4^ꢁ), 128.94 (C-5/5^ꢁ), 130.91 (C-6/6^ꢁ), 132.05 (C-3/3^ꢁ),

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J. VOSS ET AL.

135.51 (C-1/1^ꢁ), 140.42 (C-2/2^ꢁ), 194.57 (C O). Anal. calcd. for C₁₆H₁₂Br₂O₂(396.09):

C, 48.52; H, 3.05; Br, 40.35; Found: C, 49.50; H, 3.16; Br, 39.60.

1,3-Bis(bromoacetyl)naphthalene (41). The reaction of 40 (4.3 g, 0.016 mol)

with aq. HBr (47%, 91 mL) in diethyl ether (400 mL) gave 41 as a yellow powder (5.3 g,

89%), mp 119^◦C. ¹H NMR (250 MHz): 4.60 (s, 2 H, 3-CH₂), 4.65 (s, 2 H, 1-CH₂), 7.70

(ddd, J = 1.2, 7.6, 8.0, 1 H, 6-H), 7.78 (ddd, J = 1.2, 7.9, 8.3, 1 H, 7-H), 8.05 (d, J =

7.9, 1 H, 5-H), 8.45 (s, 1 H, 4-H), 8.60 (d, J = 8.3, 1 H, 8-H), 8.65 (s, 1 H 2-H). ¹³C

NMR (63 MHz): 30.01 (3-CH₂), 33.69 (1-CH₂), 126.01 (C-6), 126.23 (C-7), 128.03 (C-5),

129.67 (C-4a), 130.41 (C-8), 131.53 (C-4), 132.87 (C-8a), 133.22 (C-3), 133.55 (C-1),

135.83 (C-2), 190.33 (3-C O), 193.86 (1-C O). MS: 372 (1) [M⁺], 370 (5) [M⁺], 368 (1)

[M⁺], 276 (49) [M⁺CH₂Br], 274 (79) [M⁺CH₂Br], 168 (34) [M⁺COCH₂Br, Br],

154 (35) [M⁺COCH₂Br, CH₂Br], 140 (53) [C₁₁H₈⁺], 139 (81) [C₁₁H₇⁺], 126 (100)

[M⁺2 COCH₂Br], 95 (18) [CH₂Br⁺], 93 (17) [CH₂Br⁺]. Anal. calcd. for C₁₄H₁₀Br₂O₂

(370.04): C, 45.44; H, 2.72; Br, 43.19; Found: C, 45.45; H, 2.73; Br, 42.32.

1,4-Bis(bromoacetyl)naphthalene (52). The reaction of 49 (3.2 g, 0.012 mol)

with aq. HBr (47%, 60 mL) in diethyl ether (350 mL) gave 52 as a yellow powder (3.4 g,

1

76%), mp 136^◦C. H NMR (250 MHz): 4.50 (s, 4 H, CH₂), 7.60–7.70 (m, 2 H, 6/7-H),

7.80 (s, 2 H, 2/3-H), 8.35–8.42 (m, 2 H, 5/8-H). ¹³C NMR (63 MHz): 33.85 (CH₂), 125.19

(C-6/7), 125.78 (C-5/8), 128.85 (C-2/3), 130.88 (C-4a/8a), 137.39 (C-1/4), 194.58 (C O).

Anal. calcd. for C₁₄H₁₀Br₂O₂(370.05): C, 45.44; H, 2.72; Br, 43.18; Found: C, 45.97; H,

2.80; Br, 43.76.

1,7-Bis(bromoacetyl)naphthalene (55). The reaction of 51 (1.2 g, 0.005 mol)

with aq. HBr (47%, 25 mL) in diethyl ether (140 mL) gave 55 as a beige powder (1.4

1

g, 83%), mp 121^◦C. H NMR (250 MHz): 4.60 (s, 2 H, 7-CH₂), 4.65 (s, 2 H, 1-CH₂),

7.70 (t, J = 8.2, 1 H, 3-H), 7.95 (d, J = 8.3, 1 H, 4-H), 8.05–8.20 (m, 3 H, 2/5/6-H),

9.45 (s, 1 H, 8-H) ¹³C NMR (63 MHz): 31.27 (7-CH₂), 33.29 (1-CH₂), 125.24 (C-3),

127.28 (C-4), 128.69 (C-5), 129.54 (C-6), 130.02 (C-4a), 130.04 (C-2), 132.95 (C-8a),

133.55 (C-7), 133.96 (C-1), 136.42 (C-8), 191.54 (7-C O), 193.91 (1-C O). MS: 372

(4) [M⁺], 370 (8) [M⁺], 368 (4) [M⁺], 278 (13) [M⁺CH₂Br], 277 (99) [M⁺CH₂Br],

276 (14) [M⁺CH₂Br], 275 (100) [M⁺CH₂Br], 197 (13) [M⁺CH₂Br, Br], 168 (35)

[M⁺COCH₂Br, Br], 154 (38) [M⁺COCH₂Br, CH₂Br], 140 (43) [C₁₁H₈⁺], 139 (43)

[C₁₁H₇⁺], 126 (48) [M⁺2 COCH₂Br]. Anal. calcd. for C₁₄H₁₀Br₂O₂(370.04): C, 45.44;

H, 2.72; Br, 43.19; Found: C, 46.00; H, 2.96; Br, 42.98.

2,6-Bis(bromoacetyl)naphthalene (66). The reaction of 64 (7.0 g, 0.028 mol)

with aq. HBr (47%, 140 mL) in diethyl ether (400 mL) gave 66 as a light yellow powder

(6.3 g, 63%), mp 225–227^◦C. ¹H NMR (250 MHz): 4.60 (s, 4 H, CH₂), 8.10–8.15 (m, 4 H,

3/4/7/8-H), 8.55 (s, 2 H, 1/5-H) ¹³C NMR (63 MHz): 30.57 (CH₂), 125.47 (C-4/8), 130.39

(C-3/7), 130.58 (C-1/5), 133.71 (C-4a/8a), 134.96 (C-2/6), 191.08 (C O).

2,7-Bis(bromoacetyl)naphthalene (67). The reaction of 65 (4.8 g, 0.018 mol)

with aq. HBr (47%, 60 mL) in diethyl ether (500 mL) gave 67 as a yellow powder

1

(5.0 g, 73%), mp 139–142^◦C. H NMR (250 MHz): 4.60 (s, 4 H, CH₂), 8.00 (d, J =

8.5, 2 H, 4/5-H), 8.20 (d, 2 H, J = 8.5, 2 H, 3/6-H), 8.70 (s, 2 H, 1/8-H). ¹³C NMR

(63 MHz): 30.41 (CH₂), 127.33 (C-4/5), 128.89 (C-3/6), 131.67 (C-4a), 132.38 (C-1/8),

138.18 (C-8a), 144.05 (C-2/7), 190.86 (C O). MS: 372 (5) [M⁺], 370 (11) [M⁺], 368 (5)

[M⁺], 278 (14) [M⁺CH₂Br], 277 (98) [M⁺CH₂Br], 276 (14) [M⁺CH₂Br], 275 (100)

[M⁺CH₂Br], 197 (4) [M⁺CH₂Br, Br], 180 (25), 154 (57) [M⁺COCH₂Br, CH₂Br],

126 (42) [M⁺2 COCH₂Br]. Anal. calcd. for C₁₄H₁₀Br₂O₂(370.04): C, 45.44; H, 2.72;

Br, 43.19; Found: C, 45.80; H, 2.62; Br, 43.00.

BENZENE-, BIPHENYL-, NAPHTHALENE-BIS(α-OXOETHANEDITHIOATES)

2267

Bromoketones from Ketones

1,3,5-Tris(bromoacetyl)benzene (21). 1,3,5-Triacetylbenzene⁴⁴(24.8 g, 0.100

mol) was dissolved in AcOH (100%). Br₂(48.0 g, 0.300 mol) was added with caution.

The reaction was started by irradiation with an electric bulb (60 W). The mixture soon

decolorized and began to boil. After cooling, the produced HBr was removed by suction.

The solution was diluted with sufﬁcient water. The precipitate was ﬁltered off, washed

with NaHCO₃-solution until neutral, and dried in a desiccator over P₂O₅to yield 21 (38.8

g, 88%), mp 110–112^◦C (lit.⁴⁴: mp 111^◦C), which could be used in the next step without

further puriﬁcation. IR: 1690 (C O). ¹H NMR: 5.90 (s, 6 H, CH₂), 8.83 (s, 3 H, 2/4/6-H).

Anal. calcd. for C₁₂H₉Br₃O₃(440.91): C, 32.69; H, 2.06; Br, 54.37; Found: C, 32.72; H,

1.95; Br, 56.00.

1,5-Bis(bromoacetyl)naphthalene (53). 1,5-Diacetylnaphthalene 56⁴⁵(3.5 g,

0.017 mol) was dissolved in AcOH (100%, 120 mL). A solution of Br₂(5.3 g, 0.033 mol)

in AcOH (10 mL) was added. When the red color had disappeared, a colorless precipitate

formed, which was recrystallized from AcOH/AcOEt to yield 53 as colorless crystals (3.3

g, 52%), mp 175^◦C [lit.⁴⁵: 181–182^◦C (AcOEt)]. ¹H NMR (250 MHz): 4.60 (s, 4 H, CH₂),

7.70 (dd, J = 8.3/7.8, 2 H, 3/7-H), 8.00 (d, J = 7.9, 2 H, 5/8-H), 8.80 (d, J = 8.5, 2 H,

2/6-H).

1,6-Bis(bromoacetyl)naphthalene (54). 1,6-Diacetylnaphthalene 57⁴⁶(7.3 g,

0.035 mol) was dissolved in AcOH (100%, 70 mL). A solution of Br₂(11.0 g, 0.069 mol)

in AcOH (20 mL) was added. When the red color had disappeared, a colorless precipitate

formed, which was recrystallized from AcOH/AcOEt to yield 54 as beige colored powder

(6.5 g, 51%), mp 124–128^◦C. ¹H NMR (250 MHz): 4.60 (s, 4 H, CH₂), 7.60 (t, J = 7.8, 1

H, 3-H), 8.05–8.25 (m, 3 H, 2/4/8-H), 8.60 (s, 1 H, 5-H), 8.80 (d, J = 8.5, 1 H, 7-H). ¹³C

NMR (100 MHz): 30.64 (6-CH₂), 33.30 (1-CH₂), 125.55 (C-3), 126.72 (C-4), 126.81 (C-

8), 130.99 (C-7), 131.12 (C-2), 131.88 (C-4a), 132.34 (C-8a), 133.27 (C-6), 133.29 (C-1),

135.38 (C-5), 190.94 (6-C O), 193.82 (1-C O). MS: 372 (5) [M⁺], 370 (10) [M⁺], 368

(5) [M⁺], 278 (14) [M⁺CH₂Br], 277 (98) [M⁺CH₂Br], 276 (14) [M⁺CH₂Br], 275

(100) [M⁺CH₂Br], 197 (48) [M⁺CH₂Br, Br], 154 (46) [M⁺COCH₂Br, CH₂Br],

140 (28) [C₁₁H₈⁺], 139 (27) [C₁₁H₇⁺], 126 (40) [M⁺2 COCH₂Br], 91 (20) [C₇H₇⁺].

Anal. calcd. for C₁₄H₁₀Br₂O₂(370.04): C, 45.44; H, 2.72; Br, 43.19; Found: C, 45.92; H,

2.64; Br, 42.31.

α-Oxo-dithioesters by CAT Reaction of Diazoketones

(General Prodedure)

A mixture of S₈(3 equivalents), NEt₃(3 equivalents), and dry CaCl₂(1.1 equivalents)

in dry DMF (100 mL if 0.1 mol of the diazoketone were used) was stirred at 20^◦C for 30 min.

Then the diazoketone (1 equivalent) was added portionwise. Stirring was continued at 20^◦C

(if not stated otherwise) at least until the evolution of N₂ceased. Since the progress of the

reaction could not be directly monitored by TLC, reaction times of up to 48 h were applied.

The mixture was cooled down to −10^◦C, and MeI or EtI (0.4 equivalents) was added.

After another 28 h stirring at 20^◦C, the reaction mixture was poured into ice-water and

neutralized with dil. HCl. The products were extracted with sufﬁcient CHCl₃. The extracts

were washed ﬁve to 10 times with H₂O to remove the DMF completely, dried over Na₂SO₄,

and evaporated under vacuum. The residues were pre-puriﬁed by ﬂash chromatography

(CHCl₃) and ﬁnally puriﬁed by recrystallization and/or column chromatography (CC) with

2268

J. VOSS ET AL.

suitable solvents and eluents. The α-oxo-dithioesters are deeply colored and more or less

foul-smelling compounds, which can be stored without decomposition in a refrigerator for

months.

Dimethyl 2-methyl-1,3-benzene-bis(α-oxoethanedithioate) (3). Thio-

lation of 1 (2.1 g, 0.009 mol) gave 3 as red crystals (0.7 g, 24%), mp 133–135^◦C

1

(CHCl₃/hexane). H NMR (250 MHz): 2.55 (s, 3 H, CH₃), 2.80 (s, 6 H, SCH₃), 7.30

(t, J = 8.3, 1 H, 5-H), 7.60 (d, J = 8.9, 2 H, 4/6-H). ¹³C NMR (63 MHz): 18.45

(CH₃), 18.58 (SCH₃), 124.61 (C-5), 132.95 (C-4/6), 137.12 (C-1/3), 138.42 (C-2),

189.96 (C O), 229.74 (C S). MS: 328 (1) [M⁺], 237 (10) [M⁺CS₂CH₃], 162 (7),

[M+ COCS₂CH₃, SCH₃], 160 (14), 158 (7), 85 (66), 83 (100), 47 (24). Anal. calcd. for

C₁₃H₁₂O₂S₄(328.50): C, 47.53; H, 3.68; S, 39.04; Found: C, 46.19; H, 4.49; S, 38.72.

Dimethyl 4-methyl-1,3-benzene-bis(α-oxoethanedithioate) (4). Thiola-

tion of 2 (3.5 g, 0.015 mol) gave 4 as red crystals (1.2 g, 23%), mp 63^◦C (CHCl₃/hexane).

¹H NMR (250 MHz): 2.60 (s, 3 H, CH₃), 2.80 (s, 6 H, SCH₃), 7.35 (d, J = 8.9,

1 H, 5-H), 7.90 (d, J = 8.8, 1 H, 6-H), 8.2 (s, 1 H, 2-H). ¹³C NMR (100 MHz):

18.39 (CH₃), 18.77 (1-SCH₃), 21.53 (3-SCH₃), 130.23 (C-5), 131.99 (C-6), 132.76

(C-1), 133.72 (C-2), 134.37 (C-3), 146.70 (C-4), 189.04 (1-C O), 189.64 (3-C O),

230.09 (1-C S), 230.10 (3-C S). MS: 328 (7) [M⁺], 281 (1) [M⁺SCH₃], 237 (100)

[M⁺CS₂CH₃], 209 (20) [M⁺COCS₂CH₃], 162 (8), [M⁺COCS₂CH₃, SCH₃],

118 (24) [M⁺COCS₂CH₃, CS₂CH₃], 90 (28) [M⁺2 COCS₂CH₃]. Anal. calcd. for

C₁₃H₁₂O₂S₄(328.50): C, 47.53; H, 3.68; S, 39.04; Found: C, 47.13; H, 3.52; S, 39.11.

Dimethyl 2-methyl-1,4-benzene-bis(α-oxoethanedithioate) (8). Thiola-

tion of 5 (1.63 g, 0.0071 mol) gave 8 as dark red crystals (0.98 g, 42%), mp 63–65^◦C

(CHCl₃/hexane). ¹H NMR (250 MHz): 2.50 (s, 3 H, CH₃), 2.75 (s, 6 H, SCH₃), 7.50–7.90

(m, 3 H, 3/5/6-H). ¹³C NMR (100 MHz): 18.40 (SCH₃), 18.76 (SCH₃), 20.85 (CH₃),

127.06 (C-5), 130.73 (C-3), 132.96 (C-6), 135.22 (C-2), 139.35 (C-4), 139.54 (C-1),

189.50 (C O), 189.75 (C O), 229.73 (C S), 230.01 (C S). MS: 328 (5) [M⁺], 237

(100) [M⁺CS₂CH₃], 209 (11) [M⁺COCS₂CH₃], 146 (25), [M⁺2 CS₂CH₃], 118 (66)

[M⁺COCS₂CH₃, CS₂CH₃], 91 (36) [C₇H₇⁺/CS₂CH₃⁺], 90 (28) [M⁺2 COCS₂CH₃],

89 (32). Anal. calcd. for C₁₃H₁₂O₂S₄(328.50): C, 47.53; H, 3.68; S, 39.04; Found: C,

47.51; H, 3.64; S, 39.12.

Dimethyl 2,5-dimethyl-1,4-benzene-bis(α-oxoethanedithioate) (9). Thio-

lation of 6 (1.0 g, 0.004 mol) gave 9 as red-violet crystals (0.3 g, 22%), mp 200–204^◦C

1

(CHCl₃/hexane). H NMR (250 MHz): 2.42 (s, 6 H, CH₃), 2.80 (s, 6 H, SCH₃), 7.35

(s, 2 H, 3/6-H). ¹³C NMR (100 MHz): 18.63 (SCH₃), 20.37 (CH₃), 133.29 (C-3/6),

136.19 (C-1/4), 137.28 (C-2/5), 190.12 (C O), 230.40 (C S). MS: 342 (2) [M⁺], 251

(100) [M⁺CS₂CH₃], 223 (7) [M⁺COCS₂CH₃], 160 (24), [M⁺2 CS₂CH₃], 132 (60)

[M⁺COCS₂CH₃, CS₂CH₃], 104 (18) [M⁺2 COCS₂CH₃], 91 (35) [C₇H₇⁺/CS₂CH₃⁺],

78 (17) [C₆H₆⁺], 77 (12) [C₆H₅⁺]. Anal. calcd. for C₁₄H₁₄O₂S₄(342.50): C, 49.09; H,

4.12; S, 37.44; Found: C, 48.97; H, 4.11; S, 37.47.

Diethyl 2,5-dimethyl-1,4-benzene-bis(α-oxoethanedithioate) (10). Thi-

olation of 6 (1.2 g, 0.005 mol) gave 10 as red crystals (0.15 g, 9%), mp 129–132^◦C

(CHCl₃/hexane). MS: 370 (3) [M⁺], 265 (100) [M⁺CS₂C₂H₅], 237 (9) [M⁺

COCS₂C₂H₅], 160 (24), [M⁺2 CS₂C₂H₅], 132 (57) [M⁺COCS₂C₂H₅, CS₂C₂H₅],

104 (15) [M⁺2 COCS₂C₂H₅], 103 (18), 78 (12) [C₆H₆⁺], 77 (11) [C₆H₅⁺]. Anal. calcd.

for C₁₆H₁₈O₂S₄(370.58): C, 51.86; H, 4.90; S, 34.61; Found: C, 51.57; H, 5.02; S,

34.66.

S-Isopropyl S’-methyl 1,4-benzene-bis(α-oxoethanedithioate) (12). The

thiolation mixture obtained from 1,4-bis(diazoacetyl)benzene⁴⁷(0.50 g, 0.0032 mol) was

BENZENE-, BIPHENYL-, NAPHTHALENE-BIS(α-OXOETHANEDITHIOATES)

2269

ﬁrst treated with 2-iodopropane (0.82 g, 0.0048 mol) for 2 h and subsequently with MeI

(0.45 g, 0.0032 mol). Careful CC (two times with toluene) removed the two accompanying

symmetric dithioesters 7 and 11 to give pure 12 as red oil (0.11 g, 10%). IR: 1680 (C O),

1250 (C S). ¹H NMR (250 MHz): 1.50 (d, J = 7.5, 6 H, CHCH₃), 2.84 (s, 3 H, SCH₃), 4.25

(sept, J = 7.5, 1 H, CH) 8.00 (s, 4 H, 2/3/5/6-H). Anal. calcd. for C₁₄H₁₄O₂S₄(342.53): C,

49.09; H, 4.12; S, 37.45; Found: C, 49.42; H, 4.58; S, 37.51.

Dimethyl 4,4^ꢀ-biphenyl-bis(α-oxoethanedithioate) (26). Thiolation of 25

(2.15 g, 0.007 mol) gave 26 as a salmon-colored powder (0.55 g, 21%), mp 152^◦C

(CHCl₃/hexane). ¹H NMR (250 MHz): 2.80 (s, 6 H, CH₃), 7.70 (d, J = 8.9, 4 H, 2/2^ꢁ/6/6^ꢁ-H),

8.10 (d, J = 8.9, 4 H, 3/3^ꢁ/5/5^ꢁ-H). ¹³C NMR (63 MHz): 18.41 (CH₃), 127.49 (C-2/2^ꢁ/6/6^ꢁ),

131.26 (C-3/3^ꢁ/5/5^ꢁ), 132.59 (C-4/4^ꢁ), 145.22 (C-1/1^ꢁ), 190.70 (C O), 230.83 (C S). MS:

390 (6) [M⁺], 299 (100) [M⁺CS₂CH₃], 271 (1), [M⁺COCS₂CH₃]. Anal. calcd. for

C₁₈H₁₄O₂S₄(390.57): C, 55.36; H, 3.61; S, 32.84; Found: C, 55.57; H, 3.46; S, 32.76.

Methyl 1-naphthalene-α-oxoethanedithioate (35). Thiolation of 33 (14.0 g,

0.096 mol) gave 35 as red crystals (1.5 g, 25%), mp 100–101^◦C (CHCl₃/hexane, lit.⁴mp

100–101^◦C). ¹H NMR (250 MHz): 2.84 (s, 3 H, CH₃), 7.44 (t, J = 7.7, 1 H, 3-H), 7.50–7.70

(m, 2 H, 6/7-H), 7.85–7.95 (m, 2 H, 5/8-H), 8.30 (d, J = 8.3, 1 H, 4-H), 8.82 (d, J = 8.2,

1 H, 2-H). ¹³C NMR (100 MHz): 18.74 (CH₃), 123.97 (C-6), 125.92 (C-7), 126.77 (C-3),

128.63 (C-4), 128.68 (C-4), 130.43 (C-4a), 131.32 (C-8a), 132.62 (C-8), 133.88 (C-1),

134.56 (C-2), 191.50 (C O), 232.20 (C S). MS: 246 (11) [M⁺], 231 (1) [M⁺CH₃], 155

(100) [M⁺CS₂CH₃], 127 (78) [M⁺COCS₂CH₃], 126 (12) [C₁₀H₆⁺], 101 (6), 91 (6)

[CS₂CH₃⁺], 77 (11) [C₆H₅⁺], 75 (7). Anal. calcd. for C₁₃H₁₀OS₂(246.35): C, 63.38; H,

4.09; S, 26.03; Found: C, 63.09; H, 4.00; S, 25.82.

Methyl 2-naphthalene-α-oxoethanedithioate (36). Thiolation of 34 (14.0 g,

0.096 mol) gave 36 as red crystals (2.3 g, 42%), mp 74–76^◦C (CHCl₃/hexane). ¹H NMR (250

MHz): 2.90 (s, 3 H, CH₃), 7.50–7.62 (m, 2 H, H_Ar), 7.83–8.20 (m, 4 H, H_Ar), 8.48 (s, 1 H,

1-H). ¹³C NMR (100 MHz): 18.46 (CH₃), 124.87 (C-6), 127.01 (C-7), 127.87 (C-5), 128.55

(C-8), 129.26 (C-4), 129.85 (C-3), 130.12 (C-4a), 132.18 (C-8a), 133.29 (C-1), 136.08 (C-

2), 190.94 (C O), 231.40 (C S). MS: 246 (11) [M⁺], 155 (100) [M⁺CS₂CH₃], 127 (75)

[M⁺COCS₂CH₃], 101 (7), 91 (5) [CS₂CH₃⁺], 77 (9) [C₆H₅⁺], 63 (5). Anal. calcd. for

C₁₃H₁₀OS₂(246.35): C, 63.38; H, 4.09; S, 26.03; Found: C, 63.36; H, 4.03; S, 25.92.

α-Oxo-dithioesters from Bromoketones and Other Substrates

(General Procedure)

A mixture of S₈(3 equivalents) and NEt₃(3 equivalents) in dry DMF (100 mL if

0.1 mol of bromoketone were used) was stirred at 20^◦C for 30 min. Then a solution of

the bromoketone (1 equivalent) or other substrate in DMF (30 mL) was slowly dropped

in. Stirring was continued at 20^◦C for 30 min. The mixture was cooled down to 5^◦C.

After the addition of the respective iodoalkane (3 equivalents), the mixture was stirred

at 20^◦C for at least 1 h. The formation of the dithioester was monitored by thin layer

chromatography (TLC, CHCl₃). Finally, the reaction mixture was poured into ice-water

and neutralized with dil. HCl. The products were extracted with sufﬁcient CHCl₃. The

extracts were washed 10 times with H₂O to remove the DMF completely, then dried over

Na₂SO₄and evaporated under vacuum. The residues were puriﬁed by CC (CHCl₃) and

ﬁnally puriﬁed by recrystallization and/or CC with suitable solvents and eluents.

Diisopropyl 1,4-benzene-bis(α-oxoethanedithioate) (11). Thiolation of 1,4-

bis(bromoacetyl)benzene^44,47(6.4 g, 0.020 mol) gave 11 as carmine red crystals (0.27 g,

3.7%), mp 115–117^◦C (CH₂Cl₂/hexane). IR: 1660 (C O). ¹H NMR (250 MHz): 1.50 (d,

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J. VOSS ET AL.

J = 7.5, 12 H, CH₃), 4.20 (sept, J = 7.4, 2 H, CH₂), 8.00 (s, 4 H, 2/3/5/6-H). Anal. calcd.

for C₁₆H₁₈O₂S₄(370.57): C, 51.85; H, 4.89; S, 34.60; Found: C, 51.52; H, 4.85; S, 34.87.

1,4-Naphthoquinone-2-yl 2-acetylbenzene-α-oxoethanedithioate (19).

A solution of 1,2-diacetylbenzene (Fluka, 1.0 g, 0.006 mol) in CHCl₃(13 mL) and a sepa-

rate solution of Br₂(0.5 g, 0.006 mol) in CHCl₃(6 mL) were cooled to –25^◦C and mixed

together in the cold environment. After warming to +20^◦C, the red color disappeared at

once. The reaction mixture was washed with icy water and NaHCO₃-solution. The solvent

was removed in a vacuum at low temp. The remaining 1-acetyl-2-(bromoacetyl)benzene

16 (1.45 g, 0.006 mol) was thiolated without further puriﬁcation to yield 19 (0.47 g, 21%)

as red crystals, mp 253^◦C (CHCl₃/hexane, decomp.). IR: 1700 (C O), 1650 (C O), 1600

1

(C C), 1240 (C S). UV/VIS: 527 (3.18), 282 (4.37), 246 (4.18), 206 (4.60). H NMR

(250 MHz): 1.87 (s, 3 H, CH₃), 6.93 (s, 1 H, CH), 7.66–8.03 (m, 8 H, H_Ar). MS: 380

(6) [M⁺], 233 (100), 189 (11), 147 (11), 76 (10) [C₆H₄⁺]. Anal. calcd. for C₂₀H₁₂O₄S₂

(380.44): C, 63.14; H, 3.18; S, 16.86; Found: C, 61.55; H, 3.09; S, 16.78. In addition,

2-ethylthio-1,4-naphthoquinone 20 was obtained after ethylation and careful separation by

CC (eluents: 1. diethyl ether, 2. CHCl₃) as yellow crystals (0.09 g, 7%), mp 141–142^◦C

[toluene/hexane; lit.⁴⁸: 141–142^◦C (CHCl₃)]. IR: 1680 (C O), 1660 (C O), 1600 (C C).

1

UV/VIS: 416 (3.54), 290 (4.09), 258 (4.45), 205 (4.56). H NMR (250 MHz): 1.37 (t,

J = 7.5, 3 H, CH₃), 3.00 (q, J = 7.5, 2 H, CH₂), 6.75 (s, 1 H, CH), 7.83–8.04 (m, 4 H,

H_Ar), in agreement with lit.⁴⁸MS: 218 (33) [M⁺], 189 (14) [M⁺C₂H₅], 147 (23), 76 (14)

[C₆H₄⁺], 45 (100).

Trimethyl 1,3,5-benzene-tris(α-oxoethanedithioate) (22). Thiolation of 21

(6.4 g, 0.020 mol) gave 22 as deep violet crystals (0.48 g, 5.6%), mp 98^◦C (CH₂Cl₂/hexane;

lit.⁶: mp 96^◦C). IR: 1660 (C O). ¹H NMR (250 MHz): 2.86 (s, 9 H, CH₃), 8.63 (s, 3 H,

2/4/6-H). Anal. calcd. for C₁₅H₁₂O₃S₆(432.64): C, 41.64; H, 2.79; S, 44.46; Found: C,

41.58; H, 2.65; S, 44.61.

Triethyl 1,3,5-benzene-tris(α-oxoethanedithioate) (23). Thiolation of 21

(6.4 g, 0.020 mol) gave 23 as violet crystals (0.19 g, 2%), mp 65^◦C (CH₂Cl₂/hexane).

IR: 1660 (C O). ¹H NMR (250 MHz): 1.46 (t, J = 7.5, 9 H, CH₃), 3.50 (q, J = 7.5, 6 H,

CH₂), 8.76 (s, 3 H, 2/4/6-H). Anal. calcd. for C₁₈H₁₈O₃S₆(474.70): C, 45.54; H, 3.82; S,

40.52; Found: C, 45.59; H, 3.75; S, 40.45.

Triisopropyl 1,3,5-benzene-tris(α-oxoethanedithioate) (24). Thiolation of

21 (6.4 g, 0.020 mol) gave 24 as carmine red crystals (0.044 g, 0.43%), mp 95^◦C

1

(CH₂Cl₂/hexane). IR: 1660 (C O). H NMR (250 MHz): 1.52 (d, J = 7.5, 18 H, CH₃),

3.50 (sept, J = 7.5, 3 H, CH), 8.65 (s, 3 H, 2/4/6-H). Anal. calcd. for C₂₁H₂₄O₃S₆(516.80):

C, 48.80; H, 4.68; S, 37.22; Found: C, 48.88; H, 4.55; S, 37.10.

Diethyl 4,4^ꢀ-biphenyl-bis(α-oxoethanedithioate) (28). Thiolation of 27

(4.0 g, 0.010 mol) gave 28 as a salmon-colored powder (1.5 g, 36%), mp 73–76^◦C

(CHCl₃/hexane). ¹H NMR (250 MHz): 1.50 (t, J = 7.5, 6 H, CH₃), 3.45 (q, J = 7.4, 4 H,

CH₂), 7.70 (d, J = 8.3, 4 H, 2/2^ꢁ/6/6^ꢁ-H), 8.05 (d, J = 8.3, 4 H, 3/3^ꢁ/5/5^ꢁ-H). ¹³C NMR

(100 MHz): 11.61 (CH₃), 29.05 (CH₂), 126.87 (C-2/2^ꢁ/6/6^ꢁ), 130.51 (C-3/3^ꢁ/5/5^ꢁ), 131.98

(C-4/4^ꢁ), 144.58 (C-1/1^ꢁ), 189.20 (C O), 229.85 (C S). MS: 418 (0.5) [M⁺], 313 (100)

[M⁺CS₂C₂H₅], 285 (2), [M⁺COCS₂C₂H₅], 180 (64) [M⁺CS₂C₂H₅, COCS₂C₂H₅],

152 (26), [M⁺2 COCS₂C₂H₅], 105 (5), 77 (9) [C₆H₅⁺]. Anal. calcd. for C₂₀H₁₈O₂S₄

(418.62): C, 57.38; H, 4.33; S, 30.64; Found: C, 57.00; H, 4.10; S, 30.00.

Methyl 2-(2^ꢀ-methylthiocarbonyl)biphenyl-α-oxoethanedithioate (32).

Thiolation of 30 (2.7 g, 0.06 mol) gave 32 as a red oil (0.7 g, 35%). ¹H NMR (250 MHz):

2.40 (s, 3 H, COSCH₃), 2.60 (s, 3 H, CS₂CH₃), 7.00 (d, J = 8.0, 1 H, 3^ꢁ-H), 7.35–7.50

BENZENE-, BIPHENYL-, NAPHTHALENE-BIS(α-OXOETHANEDITHIOATES)

2271

(m, 6 H, H_Ar), 7.70 (d, J = 8.0, 1 H, 3-H). ¹³C NMR (63 MHz): 16.64 (COSCH₃), 18.77

(CS₂CH₃), 123.84, 127.19, 128.24, 128.37, 129.69, 131.01, 131.29, 131.98 (8 CH_Ar),

134.82, 141.32, 142.31, 145.57 (4 C_qAr), 190.09 (C O), 195.98 (C O), 230.57 (C S).

Ethyl 2-naphthalene-α-oxoethanedithioate (38). Thiolation of 37⁴⁹(3.0 g,

1

0.012 mol) gave 38 as a red oil (1.6 g, 39%). H NMR (250 MHz): 1.48 (t, J = 7.5, 3

H, CH₃), 3.50 (q, J = 7.5, 2 H, CH₂), 7.55–7.70 (m, 2 H, 6/7-H), 7.85–7.95 (m, 3 H,

4/5/8-H), 8.10 (dd, J = 2.0, 8.9, 1 H, 3-H), 8.50 (s, 1 H, 1-H). ¹³C NMR (100 MHz): 11.65

(CH₃), 29.13 (CH₂), 124.30 (C-3), 126.41 (C-6), 127.26 (C-5), 127.93 (C-8), 128.64 (C-7),

129.26 (C-4), 129.53 (C-4a), 131.60 (C-8a), 132.65 (C-1), 135.47 (C-2), 190.10 (C O),

230.40 (C S). MS: 260 (16) [M⁺], 231 (3) [M⁺C₂H₅], 199 (2) [M⁺SC₂H₅], 155 (100)

[M⁺CS₂C₂H₅], 127 (70) [M⁺COCS₂C₂H₅]. Anal. calcd. for C₁₄H₁₂OS₂(260.37): C,

64.58; H, 4.65; S, 24.63; Found: C, 64.59; H, 4.67; S, 24.54.

Isopropyl 2-naphthalene-α-oxoethanedithioate (39). Thiolation of 37⁴⁹(4.0

g, 0.016 mol) gave 39 as a red oil (1.5 g, 36%). MS: 274 (5) [M⁺], 186 (12), 155 (100)

[M⁺CS₂C₃H₇], 127 (57) [M⁺COCS₂C₃H₇], 126 (13), 77 (7) [C₆H₅⁺]. Anal. calcd. for

C₁₅H₁₄OS₂(260.37): C, 65.65; H, 5.14; S, 23.37; Found: C, 65.60; H, 5.04; S, 23.25.

Methyl

1-Hydroxy-2-methylthio-naphtho[2,1-b]thiophene-4-(α-oxo-

ethanedithioate) (45). Thiolation of 41 (2.5 g, 0.007 mol) gave 45 (0.33 g, 13%)

as an orange powder, mp 184–187^◦C. IR: 3409 (OH), 3062, 2916, 1639 (C O), 1615,

1562, 1416, 1312, 1247 (C S), 1209, 1089, 1003, 973, 837, 760, 691, 579, 523, 435.

¹H NMR (400 MHz, DMSO-d₆): 2.45 (s, 3 H, SCH₃) 3.00 (s, 3H, CS₂CH₃), 7.70 (ddd,

J = 1.2, 7.0, 8.4, 1 H, 7-H), 7.90 (ddd, J = 1.2, 7.0, 8.5, 1 H, 8-H), 8.25 (d, J = 8.2,

1

1 H, 6-H), 8.60 (s, 1H, 5-H), 9.35 (d, J = 8.6, 1H, 9-H), 10.40 (s, 1 H, OH). H NMR

(250 MHz, CDCl₃): 2.40 (s, 3 H, SCH₃), 2.95 (s, 3H, CS₂CH₃), 6.75 (s, 1 H, OH), 7.55

(ddd, J = 1.2, 7.0, 8.4, 1 H, 7-H), 7.80 (ddd, J = 1.2, 7.0, 8.5, 1 H, 8-H), 7.95 (d, J =

8.2, 1 H, 6-H), 8.40 (s, 1H, 5-H), 9.15 (d, J = 8.6, 1 H, 9-H). ¹³C NMR (100 MHz,

DMSO-d₆): 19.45 (CS₂CH₃), 21.72 (2-SCH₃), 111.95 (C-2), 123.15 (C-1), 123.49 (C-9),

126.22 (C-7), 127.13, 129.57 (2 C_qu), 130.61 (C-8), 130.75 (C-6), 131.38, 132.19 (2 C_qu),

134.82 (C-5), 153.10 (C_qu), 190.54 (C O), 230.46 (C S). MS: 364 (28) [M⁺], 273 (100)

[M⁺CS₂CH₃], 245 (37) [M⁺COCS₂CH₃], 230 (25) [M⁺COCS₂CH₃, CH₃], 169

(11), 158 (30) [C₁₀H₆S⁺], 126 (21) [C₁₀H₆⁺] 125 (24) [C₁₀H₅⁺], 91 (34) [CS₂CH₂CH₃⁺].

Anal. calcd. for C₁₆H₁₂O₂S₄(364.52): C, 52.72; H, 3.32; S, 35.18; Found: C, 52.06; H,

3.24; S, 34.65.

Ethyl 1-hydroxy-2-ethylthio-naphtho[2,1-b]thiophene-4-(α-oxoethane-

dithioate) (46). Thiolation of 41 (2.8 g, 0.011 mol) gave 46 (0.3 g, 10%) as orange crys-

tals, mp 140^◦C. MS: 392 (38) [M⁺], 363 (14) [M⁺C₂H₅], 331 (2) [M⁺SC₂H₅], 287 (100)

[M⁺CS₂C₂H₅], 259 (24) [M⁺COCS₂C₂H₅], 230 (30) [M⁺COCS₂C₂H₅, C₂H₅],

158 (21) [C₁₀H₆S⁺], 126 (15) [C₁₀H₆⁺], 76 (8) [C₆H₄⁺]. Anal. calcd. for C₁₈H₁₆O₂S₄

(392.58): C, 55.07; H, 4.11; S, 32.67; Found: C, 54.64; H, 4.26; S, 33.19.

Benzyl

1-hydroxy-2-benzylthio-naphtho[2,1-b]thiophene-4-(α-oxo-

ethanedithio ate) (47). Thiolation of 41 (2.0 g, 0.005 mol) gave 47 (0.16

g, 6%) as orange red crystals, mp 173–175^◦C. MS: 516 (2) [M⁺], 425 (1)

[M⁺CH₂Ph], 349 (7) [M⁺CS₂CH₂Ph], 258 (3) [M⁺CS₂CH₂Ph, CH₂Ph], 230

(3) [M⁺COCS₂CH₂Ph, CH₂Ph), 121 (19), 91 (100) [C₇H₇⁺], 77 (8) [C₆H₅⁺], 65 (12)

[C₅H₅⁺]. Anal. calcd. for C₂₈H₂₀O₂S₄(515.72): C, 65.08; H, 3.90; S, 24.82; Found: C,

64.13; H, 3.66; S, 23.69.

Dimethyl 1,4-naphthalene-bis(α-oxoethanedithioate) (58). Thiolation

of 52 (3.4 g, 0.009 mol) gave 58 (0.7 g, 22%) as red crystals, mp 130–131^◦C

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J. VOSS ET AL.

1

(CHCl₃/hexane). H NMR (250 MHz): 2.80 (s, 6 H, CH₃), 7.60–7.68 (m, 2 H, 6/7-H),

7.75 (s, 2 H, 2/3-H), 8.45–8.55 (m, 2 H, 5/8-H). ¹³C NMR (63 MHz): 18.85 (CH₃),

126.02 (C-6/7), 127.97 (C-5/8), 128.64 (C-2/3), 131.32 (C-4a/8a), 136.43 (C-1/4),

189.77 (C O), 229.82 (C S). MS: 364 (7) [M⁺], 273 (100) [M⁺CS₂CH₃], 245 (15),

[M⁺COCS₂CH₃], 198 (12) [M⁺COCS₂CH₃, SCH₃], 182 (23), [M⁺2 CS₂CH₃], 154

(62) [M⁺COCS₂CH₃, CS₂CH₃], 126 (56) [M⁺2 COCS₂CH₃], 91 (35) [CS₂CH₃⁺].

Anal. calcd. for C₁₆H₁₂O₂S₄(364.53): C, 52.72; H, 3.32; S, 35.19; Found: C, 52.27; H,

3.22; S, 35.27.

Dimethyl 1,5-naphthalene-bis(α-oxoethanedithioate) (59). Thiolation of

53 (3.3 g, 0.009 mol) gave 59 (0.9 g, 28%) as a yellow-orange powder, mp 209–211^◦C

1

(CHCl₃/hexane). H NMR (250 MHz): 2.85 (s, 6 H, CH₃), 7.60 (dd, J = 7.3, 7.6, 2 H,

3/7-H), 7.95 (d, J = 7.3, 2 H, 4/8-H), 9.00 (d, J = 8.8, 2 H, 2/6-H). ¹³C NMR (63 MHz):

18.84 (CH₃), 126.52 (C-3/7), 131.49 (C-4a/8a), 131.73 (C-2/6), 131.76 (C-1/5), 132.34

(C-4/8), 188.98 (C O), 229.81 (C S). MS: 364 (0.4) [M⁺], 273 (28) [M⁺CS₂CH₃], 198

(4) [M⁺COCS₂CH₃, SCH₃], 154 (44) [M⁺COCS₂CH₃, CS₂CH₃], 126 (83) [M⁺

2

COCS₂CH₃], 91 (100) [CS₂CH₃⁺], 76 (7) [C₆H₄⁺]. Anal. calcd. for C₁₆H₁₂O₂S₄(364.53):

C, 52.72; H, 3.32; S, 35.19; Found: C, 51.66; H, 3.22; S, 35.16.

Diethyl 1,5-naphthalene-bis(α-oxoethanedithioate) (60). Thiolation of 53

(3.3 g, 0.009 mol) gave 60 (0.9 g, 28%) as red crystals, mp 130^◦C (CHCl₃/hexane).

MS: 392 (9) [M⁺], 288 (17), 287 (100) [M⁺CS₂C₂H₅], 259 (4) [M⁺COCS₂C₂H₅],

182 (4) [M⁺2 CS₂C₂H₅], 154 (42) [M⁺COCS₂C₂H₅, CS₂C₂H₅], 126 (37) [M⁺

2

COCS₂C₂H₅]. Anal. calcd. for C₁₈H₁₆O₂S₄(392.59): C, 55.07; H, 4.11; S, 32.67; Found:

C, 54.66; H, 4.03; S, 32.72.

Dimethyl 1,6-naphthalene-bis(α-oxoethanedithioate) (61). Thiolation

of 54 (3.5 g, 0.009 mol) gave 61 (1.1 g, 34%) as a violet powder, mp 135–137^◦C

1

(CHCl₃/hexane). H NMR (250 MHz): 2.85 (s, 3 H, 6-CH₃), 2.90 (s, 3 H, 1-CH₃),

7.50 (t, J = 8.3, 1 H, 3-H), 8.00 (d, J = 8.2, 1 H, 2-H), 8.10–8.20 (m, 2 H, 4/8-H),

8.50 (s, 1 H, 5-H), 8.80 (d, J = 8.6, 1 H, 7-H). ¹³C NMR (100 MHz): 18.45 (6-CH₃),

18.80 (1-CH₃), 125.25 (C-3), 126.53 (C-4), 127.86 (C-8), 130.86 (C-4a), 131.91 (C-8a),

132.82 (C-6), 133.03 (C-2), 133.94 (C-1), 134.66 (C-7), 135.77 (C-5), 190.11 (6-C O),

190.52 (1-C O), 230.61 (6-C S), 231.08 (1-C O). MS: 364 (5) [M⁺], 273 (100),

[M⁺CS₂CH₃], 245 (2) [M⁺COCS₂CH₃], 154 (45) [M⁺COCS₂CH₃, CS₂CH₃], 126

(40) [M⁺2 COCS₂CH₃], 91 (10) [CS₂CH₃⁺], 63 (12). Anal. calcd. for C₁₆H₁₂O₂S₄

(364.53): C, 52.72; H, 3.32; S, 35.18; Found: C, 52.71; H, 3.03; S, 35.90.

Diethyl 1,6-naphthalene-bis(α-oxoethanedithioate) (62). Thiolation of 54

(2.9 g, 0.008 mol) gave 62 (1.0 g, 31%) as red crystals, mp 85–87^◦C (CHCl₃/hexane).

MS: 392 (7) [M⁺], 287 (100) [M⁺CS₂C₂H₅], 259 (7) [M⁺COCS₂C₂H₅], 154 (59)

[M⁺COCS₂C₂H₅, CS₂C₂H₅], 126 (53) [M⁺2 COCS₂C₂H₅], 77 (9) [C₆H₅⁺]. Anal.

calcd. for C₁₈H₁₆O₂S₄(392.59): C, 55.07; H, 4.11; S, 32.67; Found: C, 55.12; H, 4.01; S,

32.81.

Dimethyl 1,7-naphthalene-bis(α-oxoethanedithioate) (63). Thiolation of

55 (1.4 g, 0.004 mol) gave 63 (0.6 g, 45%) as a violet powder, mp 90–93^◦C (CHCl₃/hexane).

¹H NMR (250 MHz): 2.85 (s, 3 H, 7-CH₃), 2.90 (s, 3 H, 1-CH₃), 7.60 (t, J = 8.2, 1 H, 3-H),

7.90–8.00 (m, 2 H, 4/5-H), 8.05–8.15 (m, 2 H, 2/6-H), 9.35 (s, 1 H, 8-H). ¹³C NMR (100

MHz): 17.92 (7-CH₃), 18.25 (1-CH₃), 125.07 (C-3), 126.70 (C-4), 128.68 (C-5), 129.40 (C-

4a), 130.73 (C-6), 131.68 (C-8a), 131.79 (C-7), 132.53 (C-2), 133.38 (C-8), 135.61 (C-1),

190.05 (2 C O), 230.16 (2 C S). MS: 364 (13) [M⁺], 273 (100), [M⁺CS₂CH₃], 245 (11)

[M⁺COCS₂CH₃], 182 (10) [M⁺2 CS₂CH₃], 154 (71) [M⁺COCS₂CH₃, CS₂CH₃],

BENZENE-, BIPHENYL-, NAPHTHALENE-BIS(α-OXOETHANEDITHIOATES)

2273

126 (65) [M⁺2 COCS₂CH₃], 91 (16) [CS₂CH₃⁺]. Anal. calcd. for C₁₆H₁₂O₂S₄(364.53):

C, 52.72; H, 3.32; S, 35.18; Found: C, 52.73; H, 3.26; S, 35.18.

Dimethyl 2,6-naphthalene-bis(α-oxoethanedithioate) (68). Thiolation of

66 (4.0 g, 0.010 mol) gave 68 (1.2 g, 31%) as red needles, mp 225–230^◦C (CHCl₃/hexane).

¹H NMR (250 MHz): 2.90 (s, 6 H, CH₃), 8.00–8.10 (m, 4 H, 3/4/5-H), 8.50 (s, 2 H,

1/5-H). ¹³C NMR (63 MHz): 18.47 (CH₃), 126.03 (C-4/8), 130.29 (C-3/7), 132.43 (C-1/5),

132.89 (C-4a/8a), 134.79 (C-2/6), 190.98 (C O), 230.18 (C S). MS: 364 (4) [M⁺], 273

(100), [M⁺CS₂CH₃], 245 (3) [M⁺COCS₂CH₃], 182 (14) [M⁺2 CS₂CH₃], 154 (92)

[M⁺COCS₂CH₃, CS₂CH₃], 126 (72) [M⁺2 COCS₂CH₃], 91 (27) [CS₂CH₃⁺], 63 (6).

Anal. calcd. for C₁₆H₁₂O₂S₄(364.53): C, 52.72; H, 3.32; S, 35.18; Found: C, 52.76; H,

3.32; S, 35.35.

Diethyl 2,6-naphthalene-bis(α-oxoethanedithioate) (69). Thiolation of 66

(1.2 g, 0.003 mol) gave 69 (0.33 g, 25%) as violet crystals, mp 113–117^◦C (CHCl₃/hexane).

MS: 392 (4) [M⁺], 287 (100) [M⁺CS₂C₂H₅], 272 (17) [M+ CS₂C₂H₅, CH₃], 259 (4)

[M⁺COCS₂C₂H₅], 182 (15) [M⁺CS₂C₂H₅], 154 (62) [M⁺COCS₂C₂H₅, CS₂C₂H₅],

126 (41) [M⁺2 COCS₂C₂H₅], 105 (4), 77 (9) [C₆H₅⁺]. Anal. calcd. for C₁₈H₁₆O₂S₄

(392.59): C, 55.07; H, 4.11; S, 32.67; Found: C, 54.91; H, 4.21; S, 32.74.

Dibenzyl 2,6-naphthalene-bis(α-oxoethanedithioate) (70). Thiolation

of 66 (2.1 g, 0.010 mol) gave 70 (0.8 g, 28%) as salmon-colored powder, mp

167–170^◦C (CHCl₃/hexane). MS: 516 (1) [M⁺], 349 (18) [M⁺CS₂CH₂Ph], 182 (3)

[M⁺2 CS₂CH₂Ph], 154 (17) [M⁺COCS₂CH₂Ph, CS₂CH₂Ph], 126 (10) [M⁺

2

COCS₂CH₂Ph], 91 (100) [C₇H₇⁺], 65 (12) [C₆H₅⁺]. Anal. calcd. for C₂₈H₂₀O₂S₄(516.73):

C, 65.08; H, 3.90; S, 24.82; Found: C, 64.72; H, 3.79; S, 24.93.

Dimethyl 2,7-naphthalene-bis(α-oxoethanedithioate) (71). Thiolation

of 67 (2.8 g, 0.008 mol) gave 71 (0.74 g, 27%) as violet crystals, mp 140–143^◦C

1

(CHCl₃/hexane). H NMR (250 MHz): 2.90 (s, 6 H, CH₃), 7.95 (d, J = 8.3, 2 H,

4/5-H), 8.15 (d, J = 8.5, 2 H, 3/6-H), 8.50 (s, 2 H, 1/8-H). ¹³C NMR (100 MHz): 18.49

(CH₃), 128.09 (C-4/5), 131.12 (C-4a), 131.35 (C-8a), 134.65 (C-1/8), 138.44 (C-2/7),

189.96 (C O), 230.48 (C S). MS: 364 (2) [M⁺], 273 (100), [M⁺CS₂CH₃], 154 (51)

[M⁺COCS₂CH₃, CS₂CH₃], 126 (49) [M⁺2 COCS₂CH₃], 91 (15) [CS₂CH₃⁺], 63 (6).

Anal. calcd. for C₁₆H₁₂O₂S₄(364.53): C, 52.72; H, 3.32; S, 35.18; Found: C, 52.64; H,

3.37; S, 36.02. See X-ray structure above and Figure 2.

Diethyl

2,7-naphthalene-bis(α-oxoethanedithioate)

(72). Thiolation

of 67 (2.0 g, 0.005 mol) gave 72 (0.3 g, 14%) as violet crystals, mp 88^◦C

(CHCl₃/hexane). MS: 287 (23) [M⁺CS₂C₂H₅], 259 (3) [M⁺COCS₂C₂H₅], 154

(52) [M⁺COCS₂C₂H₅, CS₂C₂H₅], 126 (100) [M⁺2 COCS₂C₂H₅], 105 (26), 76 (52)

[C₆H₄⁺]. Anal. calcd. for C₁₈H₁₆O₂S₄(392.59): C, 55.07; H, 4.11; S, 32.67; Found: C,

54.84; H, 4.15; S, 32.67.

Diethyl benzo[c]thiophene-1,3-dicarboxylate (76). Thiolation of diethyl 1,2-

benzenediacetate⁵⁰(1.00 g, 0.004 mol) gave 76 (0.35 g, 32%) as ﬂuorescing yellow crystals,

mp 152–153^◦C (CHCl₃/hexane); mp, spectroscopic, and analytical data are in agreement

with the literature.¹⁸

Benzo[c]thiophene-1,3-dicarbonitrile (77). Thiolation of 1,2-benzenediaceto-

nitrile⁵⁰(0.62 g, 0.004 mol) in the presence of CaCl₂gave 77 (0.10 g, 13%) as ﬂuo-

rescing yellow needles, mp 175–176^◦C (CHCl₃/hexane) [lit.⁵¹: 179–180^◦C; lit.⁵²: 183^◦C

(benzene)]. UV/VIS: 382 (4.01), 371 (4.05), 328 (3.88), 313 (3.76), 299 (3.64), 230 (4.45).

¹H NMR (250 MHz): 7.50–7.60 (m, 2 H, 4/7-H), 7.85–7.95 (m, 2 H, 5/6-H). ¹³C NMR

(63 MHz): 106.33 (C-1/3), 112.23 (CN), 120.91 (C-4/7), 129.04 (C-5/6), 142.22 (C-3a/7a).

2274

J. VOSS ET AL.

MS: 184 (100) [M⁺], 157 (10) [M⁺HCN]. Anal. calcd. for C₁₀H₄N₂S (184.22): C, 65.20;

H, 2.19; N, 15.21; S, 17.41; Found: C, 65.10; H, 2.11; N, 15.22; S, 17.35.

Dimethyl 1,4-benzene-bis(α-oxoethanedithioate) (7). Thiolation of 1,4-

diacetylbenzene (Fluka) (1.13 g, 0.007 mol) in the presence of CaCl₂gave 7 (1.76 g, 80%);

mp, IR, and ¹H NMR spectra are in agreement with an authentic sample.¹

Methyl 3-methyl-4H-chromone-2-carbodithioate (74). Thiolation of 2,3-

dimethyl-4H-chromone (73)⁵³(1.13 g, 0.0065 mol) in the presence of CaCl₂gave 74

(1.49 g, 92%) as red crystals, mp 106–107^◦C (MeOH/petroleum ether). IR: 1630 (C O),

1610 (C O), 1050 (C S). UV/VIS: 509 (1.98), 310 (4.14), 265 (4.29), 220 (4.43), 205

(4.40). ¹H NMR (250 MHz): 2.10 (s, 3 H, CH₃), 2.82 (s, 3 H, SCH₃), 7.41 (m, 2 H), 7.76

(m, 1 H), 8.21 (m, 1 H, 5-H). Anal. calcd. for C₁₂H₁₀O₂S₂(250.39): C, 57.58; H, 4.03; S,

25.62; Found: C, 57.75; H, 3.92; S, 25.67. See X-ray structure above and Figure 3.

Dimethyl benzene-1,4-bis-carbodithioate (75). Thiolation of 1,4-

benzenediacetic acid (Fluka) (0.1 g, 0.5 mmol) for a prolonged reaction time of 8

days gave dimethyl benzene-1,4-bis-carbodithioate 75 (0.05g, 38%), which was puriﬁed

1

by CC (CCl₄) and recrystallization from CHCl₃/hexane. H and ¹³C NMR: in agreement

with an authentic sample.⁵⁴Anal. calcd. for C₁₀H₁₀S₄(258.45): C, 46.47; H, 3.90; S,

49.63; Found: C, 46.38; H, 3.90; S, 49.56.

O,O’-Dimethyl 1,4-benzene-bis(α-oxoethanethioate) (78). A solution of 7

(0.37 g, 0.0012 mol) in CHCl₃(100 mL) was cooled to –10^◦C. A solution of Na (0.054 g,

0.0023 mol) in dry MeOH (10 mL) and CHCl₃(50 mL) was added under vigorous stirring.

After 30 min, the reaction mixture was warmed up to 20^◦C. The brown precipitates were

repeatedly ﬁltered off. The ﬁltrate was concentrated in a vacuum below 20^◦C and ﬁltrated

once more. The clear residue was puriﬁed by repeated CC on SiO₂(1. CHCl₃, 2. toluene)

and recrystallization from pentane/CHCl₃(2×) to yield 78 as light yellow crystals (71 mg,

21%), mp 120–122^◦C. IR: 1670 (C O). ¹H NMR (250 MHz): 4.33 (s, 6 H, CH₃), 8.03 (s,

4 H, 2/3/5/6-H). Anal. calcd. for C₁₂H₁₀O₄S₂(282.29): C, 51.05; H, 3.57; S, 22.71; Found:

C, 50.09; H, 3.47; S, 23.47.

O,O’-Diethyl 1,4-benzene-bis(α-oxoethanethioate) (79). The diethylester

79 was prepared as described for 78 by use of NaOEt instead of NaOMe. Repeated CC on

1

SiO₂(3× CHCl₃) gave 79 as a yellow oil (4 mg, 1%), IR: 1670 (C O). H NMR (250

MHz): 1.51 (t, J = 7.5 Hz, 6 H, CH₃), 4.78 (q, J = 7.5 Hz, 4 H, CH₂), 8.10 (s, 4 H,

2/3/5/6-H). MS: 104 (100), 77 (18), Anal. calcd. for C₁₄H₁₄O₄S₂(310.34): C, 54.18; H,

4.55; S, 20.66; Found: C, 54.23; H, 4.58; S, 20.80.

O,O’,O”-Trimethyl 1,3,5-benzene-tris(α-oxoethanethioate) (80). The trim-

ethylester 80 was prepared from 22 (0.45 g, 0.001 mol) as described for 78. Repeated CC

on SiO₂(3× CHCl₃) gave 80 as a yellow oil (23 mg, 5%), IR: 1670 (C O). ¹H NMR (250

MHz): 4.31 (s, 9 H, CH₃), 8.62 (s, 3 H, 2/4/6-H). Anal. calcd. for C₁₅H₁₂O₆S₃(384.45): C,

46.86; H, 3.15; S, 25.02; Found: C, 46.72; H, 3.08; S, 25.50.

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Article Doi

Preparation of new dialkyl benzene-, biphenyl-, and naphthalene- bis(α-oxoethanedithioates)

DOI: 10.1080/10426500903575409

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