Synthesis of functionalized diaryldiazenes by formal [3+3] cyclizations of 1,3-bis(silyloxy)-1,3-butadienes with 2-aryldiazenyl-3-silyloxy-2-en-1-ones

Synthesis of Functionalized Diaryldiazenes by Formal [3+3] Cyclizations

of 1,3-Bis(silyloxy)-1,3-butadienes with 2-Aryldiazenyl-3-silyloxy-2-en-1-

ones

Jennifer Hefner^a, Simone Ladzik^a, Martin Hein^a, Manuela Harms^b, Michael Lalk^b,

Nazken Kelzhanova^a, Amanzhan T. Saginayev^c, Qamar Rahman^d, Alexander Villinger^a,

Christine Fischer^e, and Peter Langer^a,e

a

Institut für Chemie, Universität Rostock, Albert-Einstein-Str. 3a, 18059 Rostock, Germany

Institut für Pharmazie, Ernst-Moritz-Arndt-Universität Greifswald, F.-L.-Jahn-Str. 17, 17487

b

Greifswald, Germany

Atyrau Institute of Oil and Gas, Atyrau, Republic of Kazakhstan

Amity University, Lucknow Campus, Viraj Khand-5, Gomti Nagar, Lucknow – 226010, India

Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Str. 29a, 18059

c

d

e

Rostock, Germany

Reprint requests to Prof. Peter Langer. Fax: +381 4986412. E-mail: peter.langer@uni-rostock.de

Z. Naturforsch. 2014, 69b, 924 – 944 / DOI: 10.5560/ZNB.2014-3198

Received July 22, 2013; in revised form March 27, 2014

The formal [3+3] cyclization of 1,3-bis(silyloxy)-1,3-butadienes with 2-aryldiazenyl-3-silyloxy-

2-en-1-ones afforded a variety of functionalized diaryl-diazenes.

Key words: Azo Compounds, Cyclizations, Diazenes, Silyl Enol Ethers, Salicylates

Introduction

It inhibits the release of leukotriene B₄, thromboxane

B₂, and prostaglandin and shows interesting transport

In 1995, 800.000 t of organic dyes were produced properties in vivo [4]. Diazene B, the dye Alizarin

every year. Half of this amount is based on azo com- Yellow R, shows inhibition of amyloid ﬁbril forma-

pounds which can be used to realize various kinds tion [5 – 9].

of colors and show excellent pigment properties [1].

Diaryl-diazenes have been prepared by electrophilic

Chrysoidin, developed in 1875, represents the ﬁrst syn- substitution reactions of benzene derivatives with aryl-

thetic azo dye which is still used today for coloring pa- diazonium salts. Despite the general usefulness of this

per (Fig. 1). The bis-azo dyes Naphthol Blueblack 6B method, the synthesis of highly substituted and func-

and Kongo Red are used for textiles [1]. Azo dyes are tionalized derivatives is problematic, due to the for-

also used in analytical chemistry. For example, methyl mation of mixtures of ortho/para regioisomeres and

orange is used as an indicator. The use of azo com- due to the limited availability of the required start-

pounds, such as Butter Yellow or Brown FK (E154), ing materials. Instead of the formation of a C–N

as food dyes is limited by their toxicity. For exam- bond, diaryl-diazenes have also been prepared by for-

ple, Druckrey was the ﬁrst to show that Butter Yellow mation of two C–C bonds based on cyclization re-

can cause liver cancer. This resulted in prohibition of actions of diazene-containing building blocks. The

this dye for food industries as early as in 1938 [2, 3]. cyclization of 2-aryldiazenyl-1,3-diones with guani-

More recently, diaryl-diazenes have been shown to dine [10], sulfuryl diamide [11], hydroxylamine [12],

be interesting lead structures in medicinal chemistry. hydrazines [13, 14], hydrazides [15], and anilines [16]

Pharmacologically active derivatives include, for ex- afforded various aryl-hetaryl-diazenes [18 – 21]. Re-

ample, the salicylate-derived diazene A (Fig. 1) which cently, we reported preliminary results [22] related to

exhibits anti-cancer, cytotoxic, apoptosis-inducing, an- the ﬁrst synthesis of functionalized diaryl-diazenes,

tiallergic, antihistaminic, and protein-binding activity. containing two benzene moieties, based on a building

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J. Hefner et al. · Functionalized Diaryldiazenes

925

Fig. 1. Important diaryl-diazenes.

block approach. These reactions, which rely on the for-

mal [3+3] cyclization of 2-aryldiazenyl-3-silyloxy-2-

en-1-ones with 1,3-bis(silyloxy)-1,3-butadienes [23],

allow for a convenient synthesis of salicylate-derived

diazenes which are not readily available by other meth-

ods. Herein, we wish to report full details and a study

related to the preparative scope.

Results and Discussion

Synthesis

The reaction of pentane-2,4-dione with various ani-

lines, following a known procedure [17], afforded the

2-aryldiazenyl-1,3-diones 1a–m (Scheme 1, Tables 1A

and 1B). Derivatives 1c–e, g, m are new. The sily-

lation of 1a–m gave the 2-aryldiazenyl-3-silyloxy-

2-en-1-ones 2a–m. The TiCl₄-mediated reaction of

various 1,3-bis(trimethylsilyloxy)-1,3-butadienes with

2a–m, readily available from the corresponding 1,3-

dicarbonyl compounds [24 – 28], afforded the diaryl-

diazenes 3a–ao. During the optimization, it proved

Scheme 1. Synthesis of diaryl-diazenes 3a–aq.

to be important to carry out the reaction in a highly Solid-state structures

concentrated solution. The products are formed by

TiCl₄-mediated attack of the terminal carbon atom of

The structures of several products in the solid state

the 1,3-bis(trimethylsilyloxy)-1,3-butadiene onto the were studied by X-ray crystal structure analyses. Ta-

3-silyloxy-2-en-1-one, cyclization via the central car- ble 2 shows crystal data. All compounds show in-

bon atom of the diene onto the carbonyl group, and tramolecular hydrogen bonds also contained in Ta-

aromatization. The yields of the products were in the ble 2. For those compounds, where the hydroxyl pro-

range of 12 – 66%. The low yields can be explained by tons were not reﬁned freely, the distances to the car-

incomplete conversion and by TiCl₄-mediated oxida- bonyl oxygen atoms are given without standard devi-

tive dimerization of the diene, which is a known pro- ation. The distances d(O–H···O) are in the range of

cess [27, 28]. In addition, the difﬁcult chromatographic 1.65 – 1.95 Å, the distances d(O···O) are in the range of

puriﬁcation resulted in a decrease of the yield in many 2.512 – 2.621 Å. The values are similar to that reported

cases. The base-mediated cyclization of 3h afforded for salicylic acid (d(O···O) = 2.590 – 2.620 Å; d(O–

chromane 4 in 76% yield (Scheme 2).

H···O) = 1.690 – 1.704 Å) [29, 30]. In Table 2 only the

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J. Hefner et al. · Functionalized Diaryldiazenes

3

R¹

R²

R³

R⁴

Yield (%) (3)^a

M. p. (^◦C)

λ_max(nm)

Table 1A. Synthesis of 3a–v.

a

b

c

d

e

f

g

h

i

j

k

l

m

n

o

p

q

r

s

H

Me

Et

OMe

nUndec

H

OMe

OEt

H

Me

H

66

60

50

51

41

35

46

41

31

33

30

32

31

41

60

30

41

30

37

31

23

31

82

228, 335, 457

66 – 67

88 – 90

75 – 77

79 – 80

OMe

OiPr

OMe

OEt

OiPr

OMe

OEt

226, 338, 457

227, 340, 467

227, 338, 459

(CH₂)₃Cl

86 – 87

140 – 143

74 – 75

H

Me

H

Me

H

232, 335, 457

245, 335, 453

Et

iPr

tBu

n-Dec

OMe

231, 340, 455

82 – 84

49 – 50

(CH₂)₃Cl

62 – 64

70 – 72

137 – 139

62 – 64

97

H

Me

H

230, 335, 453

245, 337, 450

t

u

v

OiPr

OEt

OMe

42 – 43

Ph(CH₂)₂

a

Isolated yields.

Table 1B. Synthesis of 3w–

aq.

3

w

x

y

R¹

Me

H

R²

OMe

OEt

R³

OMe

R⁴

Yield (%) (3)^a

M. p. (^◦C)

131 – 132

77 – 78

77 – 79

95 – 96

85 – 87

91 – 93

86 – 88

85 – 86

61 – 63

125 – 127

80 – 82

122 – 123

95 – 98

121 – 122

96 – 98

99 – 100

61 – 63

111 – 113

107 – 109

56 – 57

λ_max(nm)

H

36

31

33

22

38

55

39

32

30

39

22

11

44

35

32

40

47

20

21

12

24

245, 340, 444

(CH₂)₂OMe OMe

z

(CH₂)₃Cl

OMe

OEt

OMe

SMe

aa

ab

ac

ad

ae

af

ag

ah

ai

aj

ak

al

am

an

ao

ap

aq

H

Me

Et

H

245, 356, 451

(CH₂)₂OMe SMe

Allyl

(CH₂)₃Cl

nPr

H

Me

OMe

H

OMe

OEt

OMe

OEt

SMe

COOEt

Cl

245, 348, 468

230, 340, 456

Et

H

Br

231, 341, 461

(CH₂)₃Cl

H

OCF₃

-O-CH₂-O

245, 339, 453

245, 354, 446

OEt

116 – 117

a

Isolated yields.

distances between the hydrogen donor and acceptor as also reported [36, 37] for azo-benzene (d(N–

oxygens are given because the determination of the ex- N) = 1.171 – 1.243 Å) (Table 3). The C–N bond

act positions of the hydrogen atoms is unreliable (see lengths are also in the range as reported for azo-

also the section Crystal Structure Determination).

benzene (d(C–N) = 1.433 – 1.472 Å) [32]. In all cases,

The bond lengths of the azo group are in the the azo group exists in the thermodynamically favored

range of d(N–N) = 1.207 – 1.259 Å (for comparison: E-conﬁguration ((C–N–N–C) ∼ 180^◦). The torsion

d_cov(N=N) = 1.20 Å; d_cov(N≡N) = 1.10 Å [31]) angles to the azo-phenyl group are quite different

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J. Hefner et al. · Functionalized Diaryldiazenes

927

Scheme 2. Synthesis of chroman 3ar.

and vary in the range of (N1–N2–C–C) = 0.2 – 26.8^◦.

The largest angle is observed for diazene 3d. The azo

phenyl moiety and the salicylate moiety are ortho-

gonal to each other (= 90^◦) (Fig. 2). This structure is

stabilized in the crystal lattice by intermolecular short

contacts between a hydrogen atom of the azophenyl

group and an oxygen atom of the hydroxyl group of

a neighboring molecule (d(C–H···O) ∼ 2.5 Å) with

a distance of the hydrogen donor and acceptor atoms

Fig. 2. ORTEP plot of the molecular structure of 3d in the

solid (displacement ellipsoids at the 50% probability level;

hydrogen atoms as spheres with arbitrary radius).

(d(C15···O3*) = 3.257 Å. Related structures are found tances [33 – 37]. The intra- and intermolecular hydro-

for derivatives 3am and 3q (Figs. 3, 4). Table 3 shows gen bonds are more relevant (vide infra).

selected bond lengths and torsion angles (d in Å, in

The structure of 3an is shown in Fig. 6. The unit cell

deg).

contains two independent molecules, with the second

To study the importance of π stacking in the crys- molecule disordered. The structural parameters of

tal structures, the shortest intermolecular distance be- both molecules differ greatly from each other and are

tween the phenyl groups were inspected for all com- discussed separately. In both molecules intramolec-

pounds (Table 4). The angles between the planes of ular hydrogen bonds were found. In molecule 1 the

the rings were not taken into consideration. The short- distance between the hydrogen donor and acceptor

est distance d_min= 3.645 Å is observed for derivative oxygen atoms is d(O3···O1) = 2.528 Å. For molecule

3a (Fig. 5). In general, the π stacking is stronger for 2 (disordered) the values are d(O6a···O4a) = 2.668 Å

derivatives containing a hydrogen atom located next (major occupancy) and d(O6b···O4b) = 2.49 Å (minor

to the hydroxyl group (3a, 3i, 3q, 3an) as compared occupancy). The difference of the d(O···O) values

to those containing a hydrogen atom next to an alkyl for the two molecules of 3an is due to the carboxyl

group located (3d, 3am), presumably due to the steric group, which is not in the aromatic ring plane for

effect of the latter. However, for all products the π- molecule 2 [molecule 1: (C2–C1–C7–O1) = +4.9^◦,

stacking effects are not predominant for the structure molecule 2: (C18a–C17a–C23a–O4a) = +31.1^◦(ma-

of the crystal lattice because of the relatively large dis- jor occupancy) and (C18b–C17b–C23b–O4b) = −16^◦

Table 2. Overview of crystal struc-

ture analyses.

Crystal system Space group

Z

Intramolecular hydrogen bonds

d(O···O) (Å)

3a

3d

3am

3q

3an

orthorhombic

monoclinic

triclinic

Pbca

P2₁/n

P1

8

4

8

4

2.517(2)

2.542(2)

2.541(3)

2.513(4)^aand 2.512(4)^a

2.528(3)^a,b, 2.668(10)^a,b(major occupancy)

and 2.49(3)^a,b(minor occupancy)

2.523(1)

3i

triclinic

P1

2

a

b

Two symmetry-independent molecules per cell unit; the difference between the d(O···O)

values for the 2 molecules of 3an is due to the carboxyl group, which is not in the aromatic ring

plane for the second (disordered) molecule.

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J. Hefner et al. · Functionalized Diaryldiazenes

Fig. 3. ORTEP plot of the molecular structure of 3am in the Fig. 4. ORTEP plot of the molecular structure of 3q in the

solid (displacement ellipsoids at the 50% probability level; solid (displacement ellipsoids at the 50% probability level;

hydrogen atoms as spheres with arbitrary radius).

d(N–N)

d(C–N1)

d(N2–C)

(C–N–N–C)

(N1–N2–C–C)

Table 3. Selected bond lengths (Å) and di-

hedral angles (deg).

3a

1.259(2)^a

1.425(2)^a

1.459(8)^a

1.448(2)

1.440(2)

1.418(3)^b

1.423(4)^b

1.419(3)^b

1.439(2)^a

−178.7(1)^a

+178.7(5)^a

−179.6(1)

−177.0(1)

−179.0(2)^b

+179.6(2)^b

−177.0(2)^b

+0.2(3)^a

−11(1)^a

1.21(1)^a

1.47(1)^a

3d

3am

3q

1.216(2)

1.233(2)

1.216(3)^b

1.207(3)^b

1.229(2)^b

1.443(3)

1.436(2)

1.436(3)^b

1.451(4)^b

1.425(3)^b

+26.8(2)

+16.0(3)

−9.0(4)^b

−5.3(5)^b

−5.0(4)^b

+3.1(4)^a,b

−1(2)^a,b

−20.9(1)

3an

1.238(3)^a,b1.431(3)^a,b1.438(3)^a,b−179.6(3)^a,b

1.237(9)^a,b1.417(7)^a,b1.424(7)^a,b+180(1)^a,b

3i

1.254(1)

1.421(1)

1.431(1)

−179.47(8)

a

Disordered; ^btwo symmetry-independent molecules per cell unit.

Table 4. π-Stacking effects.

Compound

d_min

Compound

d_min

(stacking) (Å)

3a

3d

3am

3.645

4.978

4.303

3q

3an

3i

3.743

3.849

3.691

(minor occupancy)]. The N–N bond lengths of

the azophenyl moiety are d(N1–N2) = 1.229 Å,

d(N3a–N4a) = 1.238 (major occupancy) and d(N3b–

N4b) = 1.237 Å (minor occupancy) for molecules

1 and 2, respectively. The torsion angles of the

azophenyl moieties are (N1–N2–C11–C12) = –5.0^◦,

Fig. 5. π-Stacking of 3a (the disorder of the molecules is not

(N3a–N4a–C27a–C28a) = 3.1^◦(major occupancy) shown).

and (N3b–N4b–C27b–C28b) = –0.7^◦(minor occu-

pancy) for molecules 1 and 2, respectively. In addition (d(O4b···O3) = 3.138 Å for minor occupancy

to intramolecular hydrogen bonds, intermolecular of molecule 2) and d(O1···O6a) = 3.024 Å

hydrogen bonds are observed in the range of 2.3 (d(O1···O6b) = 2.926 Å for minor occupancy

to 2.5 Å [distances between the hydrogen donor of molecule 2)]. The distance between the car-

and acceptor oxygens: d(O4a···O3) = 3.133 Å bonyl

oxygen

atoms

(d(O1···O4a) = 2.787 Å

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Fig. 6. Dimer formation of 3an without showing the disorder of molecule 2 (displacement ellipsoids at the 50% probability

level; hydrogen atoms as spheres with arbitrary radius).

d(O1···C10**) = 3.514 Å; ** = neighboring molecule

2). The distance between the oxygen atoms O(1)

is d(O1···O1**) = 3.628 Å. Weak interactions are

also observed between another proton of the methyl

group C10 (H10c) and carbon atoms C15* and

C16* of the azophenyl moiety of another neighbor-

ing molecule (distances between hydrogen donor

and acceptor atoms: d(C10···C15*) = 3.748 Å and

d(C10···C16*) = 3.582 Å; * = neighboring molecule

1). Layers are formed in the crystal lattice as depicted

in Fig. 8.

Spectroscopic studies

For all products, intramolecular hydrogen bonds

are present in solution as indicated by the low-

ﬁeld shifts in the ¹H NMR spectra in the range

of δ = 11.09 – 11.51 ppm (CDCl₃). UV/Vis spectro-

scopic studies were carried out in dichloromethane.

All products show three bands. The spectrum of 3a

is discussed in detail as an representative example

for all other derivatives (Fig. 9). The ﬁrst absorp-

tion (λ = 228 nm, ε_max= 18468) with a shoulder at

λ = 250 nm and the second absorption (λ = 334 nm,

Fig. 7. ORTEP plot of the molecular structure of 3ar in the

crystal showing the disordered heterocyclic ring (displace-

ment ellipsoids at the 50% probability level; hydrogen atoms

as spheres with arbitrary radius).

and d(O1···O4b) = 2.756 Å) is shorther than the

sum of the van der Waals radii (r_vdW(O) = 1.5 Å,

d_vdW(O···O) = 3.0 Å [38]).

The structure of 3ar was also studied by X-ray crys-

tal structure analysis (Fig. 7). The heterocyclic ring is

disordered in the solid state.

ε

_max= 16 195) can be assigned to the π →π* transi-

tions of the molecule. Azo compounds usually exhibit

low lying (n,π*)-electronic states which are coupled to

other (lower) energy states. The weak third absorption

located at λ = 457 nm (ε_max= 568) can be assigned to

such coupled n → π* transitions. A systematic inﬂu-

ence of the substituents on the absorptions was not ob-

served.

The puckering parameters [39] of the sequence

O3–C2–C3–C11a–C12a–C13a (heterocyclic ring) are

Q = 0.478(7) Å, θ = 128.2(7)^◦and φ = 85.4(9)^◦.

This results in

a

conformation between ⁶H₅

(H = semi-chair) and ⁶S₅(S = screw-boat) [40].

For the sequence O3–C2–C3–C11b–C12b–C13b

the values are Q = 0.494(9) Å, θ = 51,7(1)^◦and

φ = 273.3(1)^◦. Weak intermolecular O···H inter-

actions are observed between O1 and a proton

of the methyl group C10** (H10a**) (distance

Pharmacological activity

The cytotoxicity of three derivatives were studied

between hydrogen donor and acceptor atom: using the immortalized human keratinocyte cell line

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J. Hefner et al. · Functionalized Diaryldiazenes

Fig. 8. Layers of 3ar formed in the crystal (dashed lines show weak intermolecular interactions; the disorder of the dihy-

dropyrane rings is not shown).

Conclusions

In conclusion, we have reported formal [3 +

3] cyclizations of 1,3-bis(silyloxy)-1,3-butadienes

with readily available 2-aryldiazenyl-3-silyloxy-2-en-

1-ones. These reactions provided a convenient ap-

proach to various functionalized diaryl-diazenes which

are not readily available by other methods. The struc-

tures in solution and in the solid state were studied in

detail.

Experimental Section

Fig. 9. UV/Vis spectrum of 3a (1.0 mg in 100 mL of

dichloromethane).

General comments

All solvents were dried by standard methods, and all

reactions were carried out under an inert atmosphere. For

HaCaT. The incubation with the test compounds was

¹H and ¹³C NMR spectra the deuterated solvents were

carried out for three days, with several parallel ex-

used as indicated. Mass spectrometric data (MS) were ob-

periments and the results conﬁrmed by two indepen-

tained by electron impact ionization (EI, 70 eV), chem-

dent screenings. At a high concentration of 100 µM

all compounds showed a weak (3al) or strong (3e and

3am) cytotoxicity. The IC₅₀values of 3e and 3am were

44.5 µM und 63.8 µM, respectively. At lower concen-

trations (< 12.5 µM) the compounds proved to be non-

toxic. The presence of chlorine atoms plays a minor

role for the cytotoxicity. In contrast, the presence of

the substituent located next to the hydroxyl groups, as

present in case of 3e and 3am, seems to be advanta-

geous for the cytotoxicity.

ical ionization (CI, isobutane) or electrospray ionization

(ESI). For preparative-scale chromatography silica gel 60

(0.063 – 0.200 mm, 70 – 230 mesh) was used.

General procedure for the synthesis of

3-aryldiazenyl-4-hydroxy-pent-3-en-2-ones 1a–m

To a solution of the aniline (0.02 mol) in 4.3 mL of hy-

drochloric acid was slowly added 0.02 mol of NaNO₃(dis-

solved in 2.4 mL of water) at −5 ^◦C. To the mixture was

added 0.15 mol of NaOAc dissolved in 75 mL of water and

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1

75 mL of ethanol at 0 ^◦C. Subsequently, 0.02 mol of acetyl- m. p.: 61 – 62 ^◦C. – H NMR (300 MHz, CDCl₃): δ = 0.86

acetone was added, and the solution was stirred for 15 min. (t, ³J = 6.7 Hz, 3H, CH₂CH₃), 1.24 – 1.33 (m, 14H, 7 ×

A precipitate formed which was ﬁltered off, washed with ice- CH₂), 1.55 – 1.68 (m, 2H, CH₂), 2.47 (s, 3H, CH₃), 2.59

cold water, and dissolved in ether or dichloromethane. The (s, 3H, CH₃), 2.60 (t, ³J = 7.7 Hz, 2H, CH₂Ar), 7.20 (d,

solution was dried (Na₂SO₄), ﬁltered, and the solvent of the ³J = 8.5 Hz, 2H, ArH), 7.32 (d, ³J = 8.5 Hz, 2H, ArH),

ﬁltrate was removed in vacuo to give 1a–m. The synthesis of 14.81 ppm (s, 1H, OH). – ¹³C NMR (63 MHz, CDCl₃):

1a, b, h–k has been previously reported [17].

δ = 14.1 (CH₂CH₃), 22.7 (CH₂CH₃), 26.6 (CH₃), 29.2

(CH₂), 29.3 (CH₂), 29.5 (CH₂), 29.6 (br) (CH₂), 31.4

(CH₂), 31.6 (CH₃), 31.9 (CH₂), 35.4 (CH₂), 116.3 (CH_Ar),

129.6 (CH_Ar), 132.9 (n-Dec), 139.4 (C_ArN=N), 141.1

(C-3), 197.1, 197.7 ppm (COH, C=O). – IR (ATR, cm⁻¹):

3-(4-iso-Propylphenyldiazenyl)-4-hydroxy-pent-3-en-2-one

(1c)

Starting with 4-isopropylaniline (2.7 g, 20.0 mmol),

sodium nitrite (1.38 g, 20.0 mmol) and acetylacetone (2.0 g,

20.0 mmol), 1c was isolated as a yellow solid (4.08 g, 83%);

˜

ν = 3064 (w), 2953 (w), 2919 (s), 2847 (m), 1667 (s), 1621

(m), 1585 (w), 1495 (s), 1464 (w), 1426 (w), 1371 (m),

1351 (m), 1321 (m), 1311 (w), 1270 (m), 1195 (s), 1176 (s),

1166 (s), 1115 (w), 1055 (m), 1024 (w). – MS (GC, 70 eV):

m/z (%) = 344 (100) [M]⁺, 217 (39), 106 (66), 43 (56). –

Anal. for C₂₁H₃₂N₂O₂(344.20): calcd. C 73.22, H 9.36, N

8.13; found C 73.37, H 9.21, N 8.23.

1

m. p.: 62 – 64 ^◦C. – H NMR (250 MHz, CDCl₃): δ = 1.26

(d, ³J = 6.92 Hz, 6H, CH(CH₃)₂), 2.45 (s, 3H, CH₃), 2.60

(s, 3H, CH₃), 2.84 – 3.01 (sept, ³J = 6.89 Hz, 1H, CH),

7.24 – 7.28 (m, 2H, Ar), 7.33 – 7.37 (m, 2H, Ar), 14.81 ppm

(s, 1H, OH). – ¹³C NMR (63 MHz, CDCl₃): δ = 23.9

(CH(CH₃)₂), 26.6, 31.6 (CH₃), 33.7 (CH), 116.4, 127.6

(CH_Ar), 132.9, 139.4, 147.1 (C_Ar/C–N), 197.1, 197.7 ppm

3-(4⁰-Methylthio)phenyldiazenyl-4-hydroxy-pent-3-en-

2-one (1g)

(CO/COH). – IR (ATR, cm⁻¹): ν = 3330 (w), 3043

˜

(w), 2959 (w), 1676 (s), 829 (m), 792 (m). – MS (GC,

70 eV): m/z (%) = 246 (100) [M]⁺, 231 (32), 134 (48), 120

(55), 91 (35), 43 (80). – HRMS (EI): m/z = 246.135907

(calcd. 246.13628 for C₁₄H₁₈N₂O₂, [M]⁺). – Anal. for

C₁₄H₁₈N₂O₂(246.30): calcd. C 68.27, H 7.37, N 11.37;

found C 68.11, H 7.29, N 11.22.

Starting with 4-methylthioaniline (2.78 g, 20.0 mmol),

sodium nitrite (1.38 g, 20.0 mmol) and acetylacetone (2.0 g,

20.0 mmol), 1g was isolated as a red-brown solid (4.2 g,

1

84%); m. p.: 115 – 116 ^◦C. – H NMR (300 MHz, CDCl₃):

δ = 2.46 (s, 3H, CH₃), 2.49 (s, 3H, CH₃), 2.59 (s, 3H,

SCH₃), 7.26 – 7.25 (m, 4H, ArH), 14.80 ppm (s, 1H, OH). –

¹³C NMR (63 MHz, CDCl₃): δ = 16.3 (SCH₃), 26.6 (CH₃),

31.6 (CH₃), 116.8 (CH_Ar), 128.0 (CH_Ar), 133.1 (C_ArSCH₃),

136.1 (C_ArN=N), 139.1 (C-3), 197.0, 197.9 ppm (COH,

3-(4-tert-Butylphenyldiazenyl)-4-hydroxy-pent-3-en-2-one

(1d)

C=O). – IR (ATR, cm⁻¹): ν = 3312 (w), 3232 (w), 2979

˜

Starting with 4-tert-butylaniline (3.0 g, 20.0 mmol),

sodium nitrite (1.38 g, 20.0 mmol) and acetylacetone (2.0 g,

20.0 mmol), 1c was isolated as a yellow solid (4.74 g, 91%);

(w), 2916 (w), 1666 (s), 1621 (s), 1572 (m), 1510 (s), 1493

(m), 1411 (m), 1364 (m), 1345 (m), 1325 (m), 1314 (s),

1300 (s), 1266 (s), 1202 (s), 1184 (s), 1166 (s), 1119 (w),

1107 (w), 1088 (m), 1049 (w), 1023 (m). – MS (GC, 70 eV):

m/z (%) = 250 (69) [M]⁺, 138 (100), 43 (25). – Anal. for

C₁₂H₁₄N₂O₂S (250.08): calcd. C 57.58, H 5.64, N 11.19, S

12.81; found C 57.82, H 5.83, N 11.18, S 12.97.

1

m. p.: 81 – 82 ^◦C. – H NMR (250 MHz, CDCl₃): δ = 1.33

(s, 9H, C(CH₃)₃), 2.48 (s, 3H, CH₃), 2.60 (s, 3H, CH₃),

7.33 – 7.36 (m, 2H, Ar), 7.41 – 7.45 (m, 2H, Ar), 14.80 ppm

(s, 1H, OH). – ¹³C NMR (63 MHz, CDCl₃): δ = 26.6 (CH₃),

31.3 (C(CH₃)₃), 31.6 (CH₃), 34.6 (C(CH₃)₃), 116.0, 126.5

(CH_Ar), 133.0, 139.1, 149.3 (C_Ar/C–N), 197.0, 197.7 ppm

3-((3,5-Dimethylphenyl)diazenyl)-4-hydroxy-pent-3-en-

2-one (1m)

(CO/COH). – IR (ATR, cm⁻¹): ν = 2960 (w), 1666 (s),

˜

1618 (m), 1519 (s), 1186 (s), 835 (s), 748 (m). – MS (GC,

70 eV): m/z (%) = 260 (73) [M]⁺, 245 (100), 134 (40), 43

(66). – HRMS (EI): m/z = 260.15183 (calcd. 260.15139

for C₁₅H₂₀N₂O₂, [M]⁺). – Anal. for C₁₅H₂₀N₂O₂(260.33):

calcd. C 69.20, H 7.74, N 10.76; found C 69.40, H 7.94, N

10.41.

Starting with 3,5-dimethylaniline (2.42 g, 20.0 mmol),

sodium nitrite (1.38 g, 20.0 mmol) and acetylacetone (2.0 g,

20.0 mmol), 1m was isolated as a yellow solid (3.76 g, 81%);

1

m. p.: 91 – 92 ^◦C. – H NMR (300 MHz, CDCl₃): δ = 2.35

(s, 6H, CH₃), 2.50 (s, 3H, CH₃), 2.60 (s, 3H, CH₃), 6.85

(s, 1H, Ar), 7.03 (s, 2H, Ar), 14.71 ppm (s, 1H, OH). –

¹³C NMR (63 MHz, CDCl3): δ = 21.4, 26.7, 31.6 (CH₃),

114.1, 127.8 (CH_Ar), 133.0, 139.5, 141.5 (C_Ar/CN), 197.2,

˜

3-(4⁰-n-Decyl)phenyldiazenyl-4-hydroxy-pent-3-en-2-one

(1e)

Starting with 4-decylaniline (4.67 g, 20.0 mmol), sodium 197.8 ppm (CO/COH). – IR (ATR, cm⁻¹): ν = 3360 (w),

nitrite (1.38 g, 20.0 mmol) and acetylacetone (2.0 g, 2921 (w), 1673 (s), 1519 (s), 1450 (m), 1183 (s), 787 (m).

20.0 mmol), 1e was isolated as a yellow solid (2.4 g, 35%); – MS (GC, 70 eV): m/z (%) = 232 (100) [M]⁺, 121 (55),

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J. Hefner et al. · Functionalized Diaryldiazenes

120 (59), 105 (35), 43 (83). – HRMS (EI): m/z = 232.12046 Si(CH₃)₃), 1.30 (s, 9H, C(CH₃)₃), 2.44 (s, 3H, CH₃), 2.56

(calcd. 232.12063 for C₁₃H₁₆N₂O₂, [M]⁺). – Anal. for (s, 3H, CH₃), 7.30 – 7.33 (m, 2H, Ar), 7.38 – 7.42 ppm (m,

C₁₃H₁₆N₂O₂(232.28): calcd. C 67.22, H 4.94, N 12.06; 2H, Ar).

found C 66.52, H 6.83, N 11.97.

3-(4⁰-n-Decyl)phenyldiazenyl-4-trimethylsilyloxy-pent-

General procedure for the synthesis of 3-aryldiazenyl-

3-en-2-one (2e)

4-trimethylsilyloxy-pent-3-en-2-ones 2a–m

Starting with 1e (2.5 g, 7.3 mmol), NEt₃(1.6 mL,

11.7 mmol) and Me₃SiCl (1.7 mL, 13.1 mmol) in CH₂Cl₂

(40 mL), 2j was isolated as a yellow solid (0.96 g, 32%).

To a pentane or dichloromethane solution of 1.0 mmol of

1 was added 1.6 mmol of triethylamine. The solution was

stirred for 1 – 2 h, and then 1.8 mmol TMSCl was added. The

stirring was continued for 3 d. After ﬁltration under argon at-

mosphere, the solvent was removed in vacuo to give 2a–m.

Due to their unstable nature, 2a–m were characterized only

by ¹H NMR spectroscopy and used directly after their prepa-

ration.

–

¹H NMR (300 MHz, CDCl₃): δ = 0.00 – 0.32 (m, 9H,

Si(CH₃)₃), 0.87 (t, ³J = 7.0 Hz, 3H, CH₂CH₃), 1.18 – 1.35

(m, 16H, 8 × CH₂), 1.52 – 1.67 (m, 2H, CH₂Ar), 2.47, 2.59

(s, 3H, CH₃), 7.20, 7.32 ppm (d, ³J = 8.5 Hz, 2H, ArH).

3-(4⁰-Methoxy)phenyldiazenyl-4-trimethylsilyloxy-

pent-3-en-2-one (2f)

3-(Phenyldiazenyl)-4-(trimethylsilyloxy)-pent-3-en-2-one

Starting with 1f (3.2 g, 13.7 mmol), NEt₃(3.0 mL,

21.9 mmol) and Me₃SiCl (3.2 mL, 24.6 mmol) in CH₂Cl₂

(30 mL), 2b was isolated as a slightly yellow solid (3.6 g,

(2a)

Starting with 1a (3.063 g, 15.0 mmol), NEt₃(1.973 g,

19.5 mmol) and Me₃SiCl (2.444 g, 22.5 mmol) in CH₂Cl₂

(30 mL) 2a was isolated as an orange-yellow solid (3.814 g,

92%). – ¹H NMR (300 MHz, CDCl₃): δ = 0.09 (s, 9H,

Si(CH₃)₃), 2.34 (s, 3H, CH₃), 2.45 (s, 3H, CH₃), 7.01 – 7.10

(m, 3H, ArH), 7.15 – 7.20 ppm (m, 2H, ArH).

1

86%). – H NMR (300 MHz, CDCl₃): δ = 0.12 – 0.15 (m,

9H, Si(CH₃)₃), 2.36, 2.49 (s, 3H, CH₃), 3.72 (s, 3H, OCH₃),

6.84, 7.26 ppm (d, ³J = 8.7 Hz, 2H, ArH).

3-(4⁰-Methylthio)phenyldiazenyl-4-trimethylsilyloxy-pent-

3-en-2-one (2g)

3-(4⁰-Ethyl)phenyldiazenyl-4-trimethylsilyloxy-pent-3-en-

2-one (2b)

Starting with 1g (3.5 g, 14.0 mmol), NEt₃(3.1 mL,

22.4 mmol) and Me₃SiCl (3.2 mL, 25.2 mmol) in pentane

(50 mL), 2g was isolated as a brown solid (4.2 g, 93%). –

¹H NMR (300 MHz, CDCl₃): δ = 0.22 (s, 9H, Si(CH₃)₃),

2.46, 2.47, 2.49 (s, 3H, 2 × CH₃, SCH₃), 7.11, 7.28 ppm (d,

³J = 8.7 Hz, 2H, ArH).

Starting with 1b (3.2 g, 13.8 mmol), NEt₃(3.1 mL,

22.1 mmol) and Me₃SiCl (3.2 mL, 24.8 mmol) in CH₂Cl₂

(30 mL), 2b was isolated as a brown solid (3.25 g, 77%).

–

¹H NMR (300 MHz, CDCl₃): δ = 0.05 – 0.16 (m, 9H,

Si(CH₃)₃), 1.07 – 1.17 (m, 3H, CH₂CH₃), 2.37, 2.49 (s, 3H,

CH₃), 2.55 (q, ³J = 8.2 Hz, 2H, CH₂CH₃), 6.92 – 7.15 ppm

(m, 4H, ArH).

3-(4⁰-Ethoxycarbonyl)phenyldiazenyl-4-trimethylsilyloxy-

pent-3-en-2-one (2h)

3-((4-iso-Propylphenyl)diazenyl)-4-(trimethylsilyloxy)-

pent-3-en-2-one (2c)

Starting with 1h (3.0 g, 8.6 mmol), NEt₃(1.9 mL,

13.8 mmol) and Me₃SiCl (1.98 mL, 15.5 mmol) in CH₂Cl₂

(50 mL), 2d was isolated as a yellow solid (1.0 g, 33%). –

¹H NMR (300 MHz, CDCl₃): δ = 0.23 (s, 9H, Si(CH₃)₃),

1.38 – 1.41 (m, 3H, OCH₂CH₃), 2.50, 2.60 (s, 3H, CH₃), 4.37

(q, ³J = 7.0 Hz, 2H, OCH₂), 7.42, 8.08 ppm (d, ³J = 8.8 Hz,

2H, Ar).

Starting with 1c (2.461 g, 10.0 mmol), NEt₃(1.315 g,

13.0 mmol) and Me₃SiCl (1.630 g, 15.0 mmol) in CH₂Cl₂

(20 mL), 2c was isolated as an orange-yellow solid (2.962 g,

93%). – ¹H NMR (250 MHz, CDCl₃): δ = 0.16 (s, 9H,

Si(CH₃)₃), 1.19 (d, ³J = 6.9 Hz, 6H, CH(CH₃)₂), 2.41 (s,

3H, CH₃), 2.53 (s, 3H, CH₃), 3.02 (sept, ³J = 6.9 Hz, 1H,

CH), 7.03 – 7.06 (m, 2H, ArH), 7.17 – 7.21 ppm (m, 2H,

ArH).

3-((4-Chlorophenyl)diazenyl)-4-(trimethylsilyloxy)-pent-

3-en-2-one (2i)

Starting with 1i (2.506 g, 10.5 mmol), NEt₃(1.381 g,

13.7 mmol) and Me₃SiCl (1.717 g, 15.8 mmol) in CH₂Cl₂

(20 mL), 2i was isolated as an orange-yellow solid (2.938 g,

3-((4-tert-Butylphenyl)diazenyl)-4-(trimethylsilyloxy)-

pent-3-en-2-one (2d)

Starting with 1d (2.603 g, 10.0 mmol), NEt₃(1.315 g, 90%). – ¹H NMR (250 MHz, CDCl₃): δ = 0.14 (s, 6H,

13.0 mmol) and Me₃SiCl (1.630 g, 15.0 mmol) in CH₂Cl₂Si(CH₃)₂), 0.16 (s, 3H, SiCH₃), 2.39 (s, 3H, CH₃), 2.51 (s,

(20 mL), 2d was isolated as an orange-yellow solid (3.026 g, 3H, CH₃), 7.17 – 7.18 (m, 2H, Ar), 7.25 – 7.27 ppm (m, 2H,

91%). – ¹H NMR (250 MHz, CDCl₃): δ = 0.03 (s, 9H, Ar).

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933

3-((4-Bromophenyl)diazenyl)-4-(trimethylsilyloxy)-pent-

Methyl 4,6-dimethyl-5-phenyldiazenyl-salicylate (3a)

3-en-2-one (2j)

Starting with 2a (276 mg, 1.0 mmol), 4a (391 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3a was isolated as a red solid (188 mg, 66%);

m. p.: 82 ^◦C. – ¹H NMR (300 MHz, CDCl₃): δ = 2.31

(s, 3H, CH₃), 2.61 (s, 3H, CH₃), 3.99 (s, 3H, OCH₃),

6.78 (s, 1H, Ar), 7.49 – 7.56 (m, 3H, N=NAr), 7.86 – 7.89

(m, 2H, N=NAr), 11.23 ppm (s, 1H, OH). – ¹³C NMR

(75 MHz, CDCl₃): δ = 17.3, 20.5 (CH₃), 52.2 (OCH₃),

111.4 (CAr), 118.3, 122.4, 129.1, 130.9 (CH_Ar) 136.8,

137.3 (C_ArCH₃), 145.4, 152.6 (C_ArN=N), 161.7 (C_ArOH),

Starting with 1j (2.831 g, 10.0 mmol), NEt₃(1.315 g,

13.0 mmol) and Me₃SiCl (1.630 g, 15.0 mmol) in CH₂Cl₂

(20 mL), 2j was isolated as an orange-yellow solid (3.127 g,

88%). – ¹H NMR (300 MHz, CDCl₃): δ = 0.03 (s, 9H,

Si(CH₃)₃), 2.44 (s, 3H, CH₃), 2.56 (s, 3H, CH₃), 7.23 – 7.25

(m, 2H, Ar), 7.47 – 7.50 ppm (m, 2H, Ar).

3-(4⁰-Triﬂuoromethoxy)phenyldiazenyl-4-trimethylsilyloxy-

pent-3-en-2-one (2k)

172.0 ppm (COOCH₃). – IR (KBr, cm⁻¹): ν = 3018 (w),

˜

Starting with 1k (3.0 g, 10.4 mmol), NEt₃(2.3 mL,

16.7 mmol) and Me₃SiCl (2.4 mL, 18.7 mmol) in CH₂Cl₂

(40 mL), 2k was isolated as a yellow solid (1.25 g, 42%). –

¹H NMR (300 MHz, CDCl₃): δ = 0.14 (s, 9H, Si(CH₃)₃),

2.48, 2.60 (s, 3H, CH₃), 7.26, 7.42 ppm (d, ³J = 8.8 Hz,

2H, ArH). – ¹⁹F NMR (282 MHz, CDCl₃): δ = −58.1 ppm

(OCF₃).

2964 (w), 1620 (s), 1445 (s), 1239 (s), 1083 (m), 689 (s). –

UV/Vis (CH₂Cl₂, nm): λ_max(logε) = 228 (4.27), 335 (4.21),

457 (2.75). – MS (GC, 70 eV): m/z (%) = 284 (99) [M]⁺,

179 (100), 147 (91), 77 (59). – HRMS (EI): m/z = 284.11567

(calcd. 284.11554 for C₁₆H₁₆N₂O₃, [M]⁺). – Anal. for

C₁₆H₁₆N₂O₃(284.31): calcd. C 67.59, H 5.67, N 9.85; found

C 66.97, H 5.89, N 9.29.

3-(3⁰-4⁰Dioxolo)phenyldiazenyl-4-trimethylsilyloxy-pent-

3-en-2-one (2l)

Ethyl 4,6-dimethyl-5-phenyldiazenyl-salicylate (3b)

Starting with 2a (276 mg, 1.0 mmol), 4b (412 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3b was isolated as a red solid (179 mg, 60%); m. p.:

66 – 67 ^◦C. – ¹H NMR (250 MHz, CDCl₃): δ = 1.44 (t, ³J =

7.1 Hz, 3H, CH₂CH₃), 2.31 (s, 3H, CH₃), 2.62 (s, 3H, CH₃),

4.47 (q, ³J = 7.1 Hz, 2H, CH₂), 6.78 (s, 1H, Ar), 7.48 – 7.57

(m, 3H, N=NAr), 7.85 – 7.89 (m, 2H, N=NAr), 11.31 ppm

(s, 1H, OH). – ¹³C NMR (63 MHz, CDCl₃): δ = 14.2,

17.4, 20.5 (CH₃), 61.8 (CH2), 111.6 (C_Ar), 118.3, 122.4,

129.1, 130.9 (CH_Ar) 136.8, 137.3 (C_ArCH₃), 145.4, 152.6

(C_ArN=N), 161.8 (C_ArOH), 171.6 ppm (COOCH₂CH₃). – IR

Starting with 1l (3.0 g, 12.1 mmol), NEt₃(2.7 mL,

19.4 mmol) and Me₃SiCl (2.8 mL, 21.8 mmol) in CH₂Cl₂

(60 mL), 2l was isolated as a brown solid (1.42 g, 37%).

–

¹H NMR (300 MHz, CDCl₃): δ = 0.02 – 0.25 (m, 9H,

Si(CH₃)₃), 2.44, 2.57 (s, 3H, CH₃), 5.99 (s, 2H, CH₂),

6.71 – 6.80 (m, 2H, ArH), 7.05 ppm (s, 1H, ArH).

3-((3,5-Dimethylphenyl)diazenyl)-4-(trimethylsilyloxy)-

pent-3-en-2-one (2m)

Starting with 1m (2.323 g, 10.0 mmol), NEt₃(1.315 g,

13.0 mmol) and Me₃SiCl (1.630 g, 15.0 mmol) in CH₂Cl₂

(20 mL), 2m was isolated as an orange-yellow solid (2.740 g,

90%). – ¹H NMR (250 MHz, CDCl₃): δ = 0.06 (s, 6H,

Si(CH₃)₂), 0.15 (s, 3H, SiCH₃, 2.35 (s, 6H, CH₃), 2.49 (s,

3H, CH₃), 2.59 (s, 3H, CH₃), 6.85 (s, 1H, Ar), 7.03 ppm (s,

2H, Ar).

(ATR, cm⁻¹): ν = 2989 (w), 2935 (w), 1644 (s), 1471 (m),

˜

1243 (s), 1083 (m), 690 (s). – MS (GC, 70 eV): m/z (%) =

298 (100) [M]⁺, 193 (57), 147 (72), 77 (58). – HRMS

(EI): m/z = 298.13163 (calcd. 298.13119 for C₁₇H₁₈N₂O₃,

[M]⁺). – Anal. for C₁₇H₁₈N₂O₃(298.34): calcd. C 68.44, H

6.08, N 9.39; found C 68.11, H 6.10, N 9.14.

General procedure for the synthesis of diaryl-diazenes

3a–aq

Methyl 3,4,6-trimethyl-5-phenyldiazenyl-salicylate (3c)

Starting with 2a (276 mg, 1.0 mmol), 4c (412 mg,

To a CH₂Cl₂solution (3 ml) of 1.0 mmol of 2a–m was 1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

added 1.5 mmol of the 1,3-bis(silyl enol ether). The solution CH₂Cl₂, 3c was isolated as a red solid (149 mg, 50%); m. p.:

was cooled to −78 ^◦C and 1.1 mmol TiCl₄was added. The 88 – 90 ^◦C. – ¹H NMR (250 MHz, CDCl₃): δ = 2.18 (s, 3H,

mixture was stirred overnight and was then allowed to warm CH₃), 2.25 (s, 3H, CH₃), 2.42 (s, 3H, CH₃), 3.97 (s, 3H,

up to room temperature and poured into an aqueous solu- OCH₃), 7.50 – 7.57 ppm (m, 3H, N=NAr), 7.89 – 7.91 (m,

tion of hydrochloric acid (10%) and extracted with CH₂Cl₂2H, N=NAr), 11.51 (s, 1H, OH). – ¹³C NMR (75 MHz,

three times. The collected organic layers were dried with CDCl₃): δ = 11.7, 15.8, 17.3 (CH₃), 52.2 (OCH₃), 110.6

Na₂SO₄, ﬁltered, and the ﬁltrate was concentrated in vacuo. (C_Ar), 122.5 (CH_Ar), 123.9 (C_Ar), 129.1 (CH_Ar), 130.2

The residue was puriﬁed by chromatography (heptanes-ethyl (C_ArCH₃), 131.1 (CH_Ar), 135.8 (C_ArCH₃), 146.3, 152.5

acetate) to give products 3a–aq.

(C_ArN=N), 159.7 (C_ArOH), 172.7 ppm (COOCH₃). – IR

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J. Hefner et al. · Functionalized Diaryldiazenes

(ATR, cm⁻¹): ν = 3036 (w), 2958 (w), 1650 (s), 1438 (m), calcd. C 69.21, H 6.45, N 8.97; found C 68.45, H 6.52, N

1208 (s), 1100 (m), 805 (m), 688 (s). – UV/Vis (CH₂Cl₂, 8.67.

˜

nm): λ_max(logε) = 226 (4.09), 338 (3.90), 457 (2.82). – MS

(EI, 70 eV): m/z (%) = 298 (92) [M]⁺, 266 (48) [M]⁺, 256

Methyl 4,6-dimethyl-5-phenyldiazenyl-3-undecyl-salicylate

(3f)

(37), 193 (79), 161 (91), 77 (44). – HRMS (EI): m/z =

298.13183 (calcd. 298.13119 for C₁₇H₁₈N₂O₃, [M]⁺). –

Starting with 2a (276 mg, 1.0 mmol), 4j (622 mg,

Anal. for C₁₇H₁₈N₂O₃(298.34): calcd. C 68.44, H 6.08, N

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

9.39; found C 67.98, H 6.05, N 9.08.

CH₂Cl₂, 3f was isolated as a red oil (154 mg, 35%). –

¹H NMR (300 MHz, CDCl₃): δ = 0.86 – 0.91 (m, 3H,

Methyl 3-methoxy-4,6-dimethyl-5-phenyldiazenyl-salicylate

(3d)

(CH₂)₉CH₃), 1.27 (s, 18H, (CH₂)₉CH₃), 2.20 (s, 3H, CH₃),

2.39 (s, 3H, CH₃), 2.71 – 2.76 (m, 2H, CH₂Ar), 3.97 (s, 3H,

OCH₃), 7.52 – 7.55 (m, 3H, N=NAr), 7.88 – 7.91 (m, 2H,

N=NAr), 11.44 ppm (s, 1H, OH). – ¹³C NMR (63 MHz,

CDCl₃): δ = 14.1, 15.2, 17.4 (CH₃), 22.7, 26.2, 29.0, 29.3,

29.6, 29.6, 29.7, 30.0, 31.9 (CH₂), 52.2 (OCH₃), 110.8 (C_Ar),

122.5 (CH_Ar), 128.7 (C_Ar), 129.1 (CH_Ar), 129.9 (C_ArCH₃),

131.1 (CH_Ar), 135.4 (C_ArCH₃), 146.5, 152.5 (C_ArN=N),

159.7 (C_ArOH), 172.7 ppm (COOCH₃). – IR (ATR, cm⁻¹):

Starting with 2a (276 mg, 1.0 mmol), 4d (436 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3d was isolated as a red solid (128 mg, 41%);

1

m. p.: 75 – 77 ^◦C. – H NMR (250 MHz, CDCl₃): δ = 2.24

(s, 3H, CH₃), 2.47 (s, 3H, CH₃), 3.87 (s, 3H, OCH₃), 3.99

(s, 3H, OCH₃), 7.50 – 7.58 (m, 3H, N=NAr), 7.86 – 7.90

(m, 2H, N=NAr), 11.09 ppm (s, 1H, OH). – ¹³C NMR

(63 MHz, CDCl₃): δ = 12.3, 16.8 (CH₃), 52.4, 60.3 (OCH₃),

112.4 (C_Ar), 122.5, 129.1 (CH_Ar), 129.6, 129.8 (C_Ar),

131.1 (CH_Ar), 145.2 (C_Ar), 145.4, 152.5 (C_ArN=N), 155.0

˜

ν = 3020 (w), 2922 (s), 1656 (s), 1439 (s), 1206 (m), 766

(m), 690 (m). – MS (EI, 70 eV): m/z (%) = 438 (100) [M]⁺,

406 (33), 333 (64), 116 (27). – HRMS ((+)-ESI): m/z =

439.29588 (calcd. 439.29552 for C₂₇H₃₉N₂O₃, [M+H]⁺).

(C_ArOH), 172.0 ppm (COOCH₃). – IR (ATR, cm⁻¹): ν =

˜

2999 (w), 2964 (w), 1659 (s), 1436 (s), 1205 (s), 1115 (m),

1066 (m), 691 (m). – UV/Vis (CH₂Cl₂, nm): λ_max(logε) =

227 (4.10), 340 (3.97), 467 (2.38). – MS (GC, 70 eV):

m/z (%) = 314 (100) [M]⁺, 282 (37), 209 (68), 177 (83),

77 (73). – HRMS (EI): m/z = 314.12618 (calcd. 314.12611

for C₁₇H₁₈N₂O₄, [M]⁺). – Anal. for C₁₇H₁₈N₂O₄(314.34):

calcd. C 64.96, H 5.77, N 8.91; found C 63.86, H 5.93, N

8.73.

iso-Propyl-4,6-dimethyl-5-phenyldiazenyl-salicylate (3g)

Starting with 2a (276 mg, 1.0 mmol), 4g (433 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3g was isolated as a red oil (145 mg, 46%). – H

1

NMR (250 MHz, CDCl₃): δ = 1.43 (d, ³J = 6.3 Hz, 6H,

CH(CH₃)₂), 2.32 (s, 3H, CH₃), 2.62 (s, 3H, CH₃), 5.28 – 5.43

(sept, ³J = 6.3 Hz, 1H, CH), 6.77 (s, 1H, Ar), 7.48 – 7.57

(m, 3H, N=NAr), 7.85 – 7.89 (m, 2H, N=NAr), 11.33 ppm

(s, 1H, OH). – ¹³C NMR (63 MHz, CDCl₃): δ = 17.5, 20.5

(CH₃), 21.9 (CH(CH₃)₂), 69.9 (CH_iPr), 111.9 (C_Ar), 118.2,

122.4, 129.1, 130.8 (CH_Ar) 136.6, 137.2 (C_ArCH₃), 145.4,

152.7 (C_ArN=N), 161.7 (C_ArOH), 171.0 ppm (COOiPr). –

Methyl 4,6-dimethyl-3-ethyl-5-phenyldiazenyl-salicylate

(3e)

Starting with 2a (276 mg, 1.0 mmol), 4e (433 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3e was isolated as a red solid (159 mg, 51%);

IR (ATR, cm⁻¹): ν = 3060 (w), 2979 (w), 1651 (s), 1448

˜

(m), 1235 (s), 1101 (s), 764 (s), 686 (s). – MS (GC, 70 eV):

m/z (%) = 312 (85) [M]⁺, 252 (41), 165 (100), 147 (70),

77 (58). – HRMS (EI): m/z = 312.14668 (calcd. 312.14684

for C₁₈H₂₀N₂O₃, [M]⁺). – Anal. for C₁₈H₂₀N₂O₃(312.36):

calcd. C 69.21, H 6.45, N 8.97; found C 69.70, H 6.62, N

8.66.

1

m. p.: 79 – 80 ^◦C. – H NMR (250 MHz, CDCl₃): δ = 1.15

(t, ³J = 7.5 Hz, 3H, CH₂CH₃), 2.21 (s, 3H, CH₃), 2.40

(s, 3H, CH₃), 2.78 (q, ³J = 7.5 Hz, 2H, CH₂CH₃), 3.97

(s, 3H, OCH₃), 7.51 – 7.57 (m, 2H, N=NAr), 7.88 – 7.92

(m, 3H, N=NAr), 11.47 ppm (s, 1H, OH). – ¹³C NMR

(63 MHz, CDCl₃): δ = 13.2, 14.9, 17.4 (CH₃), 19.4 (CH₂),

52.2 (OCH₃), 110.8 (C_Ar), 122.5, 129.1 (CH_Ar), 129.8, 130.0

(C_Ar), 131.1 (CH_Ar), 135.2 (C_Ar), 146.5, 152.5 (C_ArN=N),

159.6 (C_ArOH), 172.7 ppm (COOCH₃). – IR (ATR, cm⁻¹):

Methyl 3-(3-chloropropyl)-4,6-dimethyl-5-phenyldiazenyl-

salicylate (3h)

˜

ν = 3024 (w), 2965 (w), 1652 (s), 1438 (s), 1205 (m), 1035

Starting with 2a (276 mg, 1.0 mmol), 4h (506 mg,

(m), 766 (s), 689 (s). – UV/Vis (CH₂Cl₂, nm): λ_max(logε) = 1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

227 (4.21), 338 (4.05), 459 (2.38). – MS (GC, 70 eV): CH₂Cl₂, 3h was isolated as a red solid (148 mg, 41%);

m/z (%) = 312 (100) [M]⁺, 280 (56), 207 (87), 175 (50), m. p.: 86 – 87 ^◦C. – ¹H NMR (250 MHz, CDCl₃): δ =

77 (60). – HRMS (EI): m/z = 312.14677 (calcd. 312.14684 1.97 – 2.09 (m, 2H, CH₂), 2.21, 2.39 (s, 3H, CH₃), 2.90

for C₁₈H₂₀N₂O₃, [M]⁺). – Anal. for C₁₈H₂₀N₂O₃(312.36): (m, ³J = 7.9 Hz, 2H, ArCH₂), 2.63 (m, ³J = 6.6 Hz, 2H,

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J. Hefner et al. · Functionalized Diaryldiazenes

935

CH₂Cl), 3.97 (s, 3H, OCH₃), 7.51 – 7.57 (m, 3H, N=NAr), – UV/Vis (CH₂Cl₂, nm): λ_max(logε) = 245, 335, 453. –

7.87 – 7.91 (m, 2H, N=NAr), 11.51 ppm (s, 1H, OH). MS (EI, 70 eV): m/z (%) = 312 (100) [M]⁺, 297 (24), 281

–

¹³C NMR (63 MHz, CDCl₃): δ = 15.2, 17.4 (CH₃), (22), 280 (68), 279 (73), 252 (28), 251 (55), 223 (21), 179

23.7, 31.8, 45.2 (CH₂), 52.3 (OCH₃), 110.9 (C_Ar), 122.5 (98), 149 (21), 147 (89), 105 (55), 91 (40), 77 (29). HRMS

(CH_Ar), 126.7 (C_Ar), 129.2 (CH_Ar), 130.5 (C_ArCH₃), 131.2 (EI): m/z = 312.146649 (calcd. 312.14684 for C₁₈H₂₀N₂O₃,

(CH_Ar), 135.6 (C_ArCH₃), 146.6, 152.4 (C_ArN=N), 159.7 [M]⁺).

(C_ArOH), 172.6 ppm (COOCH₃). – IR (ATR, cm⁻¹): ν =

˜

Methyl 5-(4⁰-ethylphenyl)diazenyl-3,4,6-trimethyl-salicylate

(3k)

3012 (w), 2960 (w), 1652 (s), 1435 (s), 1208 (s), 767

(m), 691 (m). – HRMS ((+)-ESI): m/z = 361.13137 (calcd.

361.13135 for C₁₉H₂₁ClN₂O₃, [M+H; ³⁵Cl]⁺). – Anal. for

C₁₉H₂₁ClN₂O₃(360.83): calcd. C 63.24, H 5.87, N 7.76;

found C 63.36, H 6.00, N 7.12.

Starting with 2b (305 mg, 1.0 mmol), 4c (412 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3k was isolated as a red oil (92 mg, 30%). – ¹H

NMR (300 MHz, CDCl₃): δ = 1.30 (t, ³J = 7.6 Hz, 3H,

CH₂CH₃), 2.14 (s, 3H, CH₃), 2.23 (s, 3H, CH₃), 2.38 (s, 3H,

CH₃), 2.74 (q, ³J = 7.6 Hz, 2H, CH₂), 3.96 (s, 3H, OCH₃),

0

Methyl 4,6-dimethyl-5-((3,5-dimethylphenyl)diazenyl)-

salicylate (3i)

Starting with 2m (305 mg, 1.0 mmol), 4a (391 mg, 7.36 (d, ³J = 8.3 Hz, 2H, CH_Ar), 7.82 (d, ³J = 8.3 Hz,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of 2H, CH_Ar), 11.47 ppm (s, 1H, OH). – ¹³C NMR (63 MHz,

0

CH₂Cl₂, 3i was isolated as a red solid (97 mg, 30%); m. p.: CDCl₃): δ = 11.7 (CH₂CH₃), 15.5, 15.7, 17.2 (CH₃),28.8

140 – 143 ^◦C. – ¹H NMR (300 MHz, CDCl₃): δ = 2.27 (s, (CH₂), 52.2 (OCH₃), 110.6 (C-3), 122.6 (CH_Ar), 123.8

0

3H, CH₃), 2.43 (s, 6H, CH₃), 2.59 (s, 3H, CH₃), 3.98 (s, (C_ArCH₃), 128.6 (CH_Ar), 130.0, 135.7 (C_ArCH₃), 146.5

3H, OCH₃), 6.77 (s, 1H, Ar), 7.15 (s, 1H, N=NAr), 7.48 (s, (C-1⁰), 148.0 (C-1), 150.8 (C-4⁰), 159.5 (COH), 172.7 ppm

2H, N=NAr), 11.19 ppm (s, 1H, OH). – ¹³C NMR (63 MHz, (C=O). – IR (ATR, cm⁻¹): ν = 3026 (w), 2962 (w), 2930

˜

CDCl₃): δ = 17.3, 20.3, 21.3 (CH₃), 52.3 (OCH₃), 111.4 (w), 2872 (w), 1731 (w), 1653 (s), 1598 (m), 1562 (m), 1515

(C_Ar), 114.1, 118.2, 120.2, 132.6 (CH_Ar), 136.2, 137.2, (m), 1437 (s), 1393 (w), 1378 (w), 1350 (s), 1312 (s), 1258

138.8 (C_ArCH₃), 145.7, 152.8 (C_ArN=N), 161.6 (C_ArOH), (s), 1209 (s), 1176 (s), 1150 (m), 1104 (s), 1049 (w), 1031

172.1 ppm (COOCH₃). – IR (ATR, cm⁻¹): ν = 3003 (w), (m), 1012 (m). – MS (GC, 70 eV): m/z (%) = 326 (100)

˜

2954 (w), 1647 (s), 1444 (s), 1243 (m), 805 (m), 683 (s). [M]⁺, 294 (54), 293 (40), 265 (33), 193 (73), 161 (67), 105

– UV/Vis (CH₂Cl₂, nm): λ_max(logε) = 232 (4.26), 335 (35), 79 (29), 77 (34). – HRMS (EI): m/z = 326.162149

(4.19), 457 (2.91). – HRMS ((+)-ESI): m/z = 335.13728 (calcd. 326.16249 for C₁₉H₂₂N₂O₃, [M]⁺).

(calcd. 335.13661 for C₁₈H₂₀N₂O₃Na, [M+Na]⁺). – Anal.

Methyl 4,6-dimethyl-5-((4-iso-propylphenyl)diazenyl)-

salicylate (3l)

for C₁₈H₂₀N₂O₃(312.36): calcd. C 69.21, H 6.45, N 8.97;

found C 69.50, H 6.74, N 9.11.

Methyl 4,6-dimethyl-5-(4⁰-ethylphenyl)diazenyl-salicylate

(3j)

Starting with 2c (319 mg, 1.0 mmol), 4a (391 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3l was isolated as a red oil (104 mg, 32%). – ¹H

Starting with 2b (305 mg, 1.0 mmol), 4a (391 mg, NMR (300 MHz, CDCl₃): δ = 1.31 (d, ³J = 6.9 Hz, 6H,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of CH(CH₃)₂), 2.28 (s, 3H, CH₃), 2.56 (s, 3H, CH₃), 2.90 – 3.06

CH₂Cl₂, 3j was isolated as a red solid (104 mg, 33%); (m, 1H, CH), 3.98 (s, 3H, OCH₃), 6.77 (s, 1H, Ar),

m. p.: 74 – 75 ^◦C. – ¹H NMR (300 MHz, CDCl₃):δ = 1.29 7.37 – 7.40 (m, 2H, N=NAr), 7.81 – 7.84 (m, 2H, N=NAr),

(t, ³J = 7.7 Hz, 3H, CH₂CH₃), 2.27 (s, 3H, CH₃), 2.56 (s, 11.19 ppm (s, 1H, OH). – ¹³C NMR (63 MHz, CDCl₃):

3H, CH₃), 2.74 (q, ³J = 7.6 Hz, 2H, CH₂), 3.97 (s, 3H, δ = 17.2, 20.3 (CH₃), 23.8 (CH(CH₃)₂), 34.1 (CH_iPr), 52.2

OCH₃), 6.76 (s, 1H, H-5), 7.35 (d, ³J = 8.5 Hz, 2H, CH_Ar), (OCH₃), 111.4 (C_Ar), 118.2, 122.5, 127.1 (CH_Ar) 136.2,

0

7.80 (d, ³J = 8.5 Hz, 2H, CH_Ar), 11.17 ppm (s, 1H, OH). 137.2 (C_ArCH₃), 145.6 (C_ArN=N), 150.9 (C_AriPr), 152.3

0

–

¹³C NMR (63 MHz, CDCl₃):δ = 15.5 (CH₂CH₃), 17.2, (C_ArN=N), 161.5 (C_ArOH), 172.0 ppm (COOCH₃). – IR

20.3 (CH₃), 28.8 (CH₂), 52.2 (OCH₃), 111.4 (C-3), 118.2 (ATR, cm⁻¹): ν = 2958 (m), 1661 (s), 1439 (m), 1350

˜

0

(CH_Ar), 122.5, 128.6 (CH_Ar), 136.2, 137.3 (C_ArCH₃), 145.7 (m), 1235 (m), 1160 (s), 802 (m). – UV/Vis (CH₂Cl₂,

(C-1⁰), 147.8 (C-1), 150.9 (C-4⁰), 161.5 (COH), 172.1 ppm nm): λ_max(logε) = 231 (4.43), 340 (4.35), 455 (3.03). –

(C=O). – IR (ATR, cm⁻¹): ν = 2960 (w), 2924 (w), 2873 HRMS ((+)-ESI): m/z = 327.17067 (calcd. 327.17032 for

˜

(w), 1666 (s), 1560 (m), 1554 (m), 1517 (w), 1503 (w), C₁₉H₂₂N₂O₃, [M+H]⁺). – Anal. for C₁₉H₂₂N₂O₃(326.39):

1477 (w), 1440 (s), 1342 (m), 1329 (m), 1309 (s), 1259 (m), calcd. C 69.92, H 6.79, N 8.85; found C 69.44, H 6.36, N

1212 (w), 1195 (m), 1158 (s), 1079 (s), 1029 (m), 1012 (m). 8.33.

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936

J. Hefner et al. · Functionalized Diaryldiazenes

3

Methyl 3,4,6-trimethyl-5-((4-iso-propylphenyl)diazenyl)-

CH(CH₃)₂), 1.42 (d, J = 6.3 Hz, 6H, CH(CH₃)₂), 2.28 (s,

salicylate (3m)

3H, CH₃), 2.58 (s, 3H, CH₃), 3.01 (sept, ³J = 6.9 Hz, 1H,

CH), 5.35 (sept, ³J = 6.3 Hz, 1H, CH), 6.77 (s, 1H, Ar),

7.37 – 7.41 (m, 2H, N=NAr), 7.81 – 7.84 (m, 2H, N=NAr),

11.30 ppm (s, 1H, OH). – ¹³C NMR (63 MHz, CDCl₃):

δ = 17.5, 20.3 (CH₃), 21.9, 23.9 (CH(CH₃)₂), 34.1, 69.9

(CH_iPr), 111.9 (C_Ar), 118.1, 122.5, 127.1 (CH_Ar), 135.9,

137.1 (C_ArCH₃), 145.7, 151.0 (C_ArN=N), 152.3 (C_AriPr),

161.5 (C_ArOH), 171.1 ppm (COOiPr). – IR (ATR, cm⁻¹):

Starting with 2c (319 mg, 1.0 mmol), 4c (412 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3m was isolated as a red solid (105 mg, 31%);

m. p.: 82 – 84 ^◦C. – H NMR (300 MHz, CDCl₃): δ = 1.32

1

(d, ³J = 6.9 Hz, 6H, CH(CH₃)₂), 2.14 (s, 3H, CH₃), 2.24

(s, 3H, CH₃), 2.39 (s, 3H, CH₃), 3.02 (sept, ³J = 6.9 Hz,

1H, CH), 3.97 (s, 3H, OCH₃), 7.38 – 7.42 (m, 2H, N=NAr),

˜

ν = 3028 (w), 2961 (m), 1653 (s), 1451 (m), 1236 (s), 1102

7.83 – 7.86 (m, 2H, N=NAr), 11.49 ppm (s, 1H, OH). – ¹³

C

(s), 840 (m), 803 (m). – MS (EI, 70 eV): m/z (%) = 354

(100) [M]⁺, 311 (42), 294 (61), 251 (60), 165 (91), 147

(55). – HRMS (EI): m/z = 354.19379 (calcd. 354.19379

for C₂₁H₂₆N₂O₃, [M]⁺). – Anal. for C₂₁H₂₆N₂O₃(354.44):

calcd. C 71.16, H 7.39, N 7.90; found C 71.00, H 7.51, N

7.68.

NMR (63 MHz, CDCl₃): δ = 11.7, 15.7, 17.3 (CH₃), 23.9

(CH(CH₃)₂), 34.2 (CH_iPr), 52.2 (OCH₃), 110.6 (C_Ar), 122.6

(CH_Ar), 123.8 (C_Ar), 127.2 (CH_Ar), 129.8, 135.7 (C_ArCH₃),

146.5, 150.9 (C_ArN=N), 152.5 (C_AriPr), 159.5 (C_ArOH),

172.7 ppm (COOCH₃). – IR (ATR, cm⁻¹): ν = 3029 (w),

˜

2962 (m), 1648 (s), 1434 (m), 1210 (s), 1099 (m), 805

(m). – MS (GC, 70 eV): m/z (%) = 240 (62) [M]⁺, 177

(100), 164 (46), 161 (69), 149 (45). – HRMS (EI): m/z =

340.178041(calcd. 340.17814 for C₂₀H₂₄N₂O₃, [M]⁺). –

Anal. for C₂₀H₂₄N₂O₃(340.42): calcd. C 70.56, H 7.11, N

8.23; found C 69.8, H 7.10, N 7.63.

Ethyl 3-(3-chloropropyl)-4,6-dimethyl-5-((4-isopropyl-

phenyl)diazenyl)-salicylate (3p)

Starting with 2c (319 mg, 1.0 mmol), 4h (506 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3p was isolated as a red solid (121 mg, 30%); m. p.:

62 – 64 ^◦C. – ¹H NMR (250 MHz, CDCl₃): δ = 1.32 (d,

³J = 6.9 Hz, 6H, CH(CH₃)₂), 1.97 – 2.09 (m, 2H, CH₂), 2.19

(s, 3H, CH₃), 2.37 (s, 3H, CH₃), 2.87 – 2.93 (m, 2H, ArCH2),

3.02 (sept, ³J = 6.9 Hz, 1H, CH(CH₃)₂), 3.63 (t, ³J =

6.6 Hz, 2H, CH₂Cl), 3.97 (s, 3H, OCH₃), 7.39 – 7.42 (m, 2H,

N=NAr), 7.83 – 7.86 (m, 2H, N=NAr), 11.48 ppm (s, 1H,

OH). – ¹³C NMR (75 MHz, CDCl₃): δ = 15.1, 17.3 (CH₃),

23.7 (CH₂), 23.9 (CH₃), 31.8 (CH₂), 34.2 (CH), 45.1 (CH₂),

52.2 (OCH₃), 110.9 (C_Ar), 122.6 (CH_Ar), 126.6 (C_Ar), 127.2

(CH_Ar) 130.2, 135.5 (C_ArCH₃), 146.7, 150.8 (C_ArN=N),

152.7 (C_AriPr), 159.5 (C_ArOH), 172.6 ppm (COOCH₃). –

Ethyl 4,6-dimethyl-5-((4-iso-propylphenyl)diazenyl)-

salicylate (3n)

Starting with 2c (319 mg, 1.0 mmol), 4b (412 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3n was isolated as a red solid (140 mg, 41%);

1

m. p.: 49 – 50 ^◦C. – H NMR (250 MHz, CDCl₃): δ = 1.31

(d, ³J = 6.9 Hz, 6H, CH(CH₃)₂), 1.44 (t, ³J = 7.1 Hz ,

3H, CH₂CH₃), 2.28 (s, 3H, CH₃), 2.58 (s, 3H, CH₃), 3.01

(sept, ³J = 6.9 Hz, 1H, CH), 4.46 (q, ³J = 7.1 Hz, 2H,

CH₂CH₃), 6.77 (s, 1H, Ar), 7.37 – 7.41 (m, 2H, N=NAr),

7.81 – 7.84 (m, 2H, N=NAr), 11.28 ppm (s, 1H, OH). –

¹³C NMR (63 MHz, CDCl₃): δ = 14.2, 17.4, 20.3 (CH₃),

23.9 (CH(CH₃)₂), 34.2 (CH_iPr), 61.7 (CH₂), 111.5 (C_Ar),

118.1, 122.5, 127.1 (CH_Ar), 136.1, 137.2 (C_ArCH₃), 145.7

(C_ArN=N), 151.0 (C_AriPr), 152.4 (C_ArN=N), 161.6 (C_ArOH),

IR (ATR, cm⁻¹): ν = 3027 (w), 2955 (m), 1651 (s), 1437

˜

(s), 1213 (m), 1100 (m), 806 (m). – MS (EI, 70 eV):

m/z (%) = 404 (27) [M; ³⁷Cl]⁺, 402 (81) [M; ³⁵Cl]⁺, 255

(90), 219 (56), 120 (100), 119 (83), 91 (81). – HRMS ((+)-

ESI): m/z = 403.1788 (calcd. 403.1783 for C₂₂H₂₈ClN₂O₃,

[M+H; ³⁵Cl]⁺). – Anal. for C₂₂H₂₈ClN₂O₃(402.91): calcd.

C 65.58, H 6.75, N 6.95; found C 64.10, H 6.80, N 6.57.

171.6 ppm (COOCH₂CH₃). – IR (ATR, cm⁻¹): ν = 2958

˜

(m), 2927 (m), 1650 (s), 1446 (m), 1239 (s), 1079 (m),

801 (s). – MS (EI, 70 eV): m/z (%) = 340 (100) [M]⁺,

294 (31), 293 (32), 251 (41), 193 (57), 147 (44). – HRMS

(EI): m/z = 340.17896 (calcd. 340.17814 for C₂₀H₂₄N₂O₃,

[M]⁺). – Anal. for C₂₀H₂₄N₂O₃(340.42): calcd. C 70.56, H

7.11, N 8.23; found C 69.34, H 7.60, N 7.97.

Methyl 4,6-dimethyl-5-((4-tertbutylphenyl)diazenyl)-

salicylate (3q)

Starting with 2d (333 mg, 1.0 mmol), 4a (391 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3q was isolated as a red solid (140 mg, 41%);

Iso-Propyl 4,6-dimethyl-5-((4-iso-propylphenyl)diazenyl)-

salicylate (3o)

1

m. p.: 70 – 72 ^◦C. – H NMR (250 MHz, CDCl₃): δ = 1.93

(s, 9H, C(CH₃)₃), 2.28 (s, 3H, CH₃), 2.60 (s, 3H, CH₃),

Starting with 2c (319 mg, 1.0 mmol), 4g (433 mg, 3.99 (s, 3H, OCH₃), 6.78 (s, 1H, Ar), 7.54 – 7.58 (m, 2H,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of N=NAr), 7.81 – 7.85 (m, 2H, N=NAr), 11.18 ppm (s, 1H,

1

CH₂Cl₂, 3o was isolated as a red oil (211 mg, 60%). – H OH). – ¹³C NMR (63 MHz, CDCl₃): δ = 17.2, 20.3 (CH₃),

NMR (250 MHz, CDCl₃): δ = 1.32 (d, ³J = 6.9 Hz, 6H, 31.3 (C(CH₃)₃), 35.0 (C(CH₃)₃), 52.2 (OCH₃), 111.4 (C_Ar),

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J. Hefner et al. · Functionalized Diaryldiazenes

937

118.2, 122.2, 126.0 (CH_Ar), 136.1, 137.2 (C_ArCH₃), 145.7, iso-Propyl 4,6-dimethyl-5-((4-tert-butylphenyl)diazenyl)-

150.5 (C_ArN=N), 154.6 (C_Ar), 161.5 (C_ArOH), 172.0 ppm salicylate (3t)

(COOCH₃). – IR (KBr, cm⁻¹): ν = 3037 (w), 2957 (w),

˜

Starting with 2d (333 mg, 1.0 mmol), 4g (433 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

1666 (s), 1446 (s), 1245 (s), 1078 (m), 839 (m), 807 (m). –

UV/Vis (CH₂Cl₂, nm): λ_max(logε) = 230 (4.20), 335 (4.15),

CH₂Cl₂, 3t was isolated as a red solid (114 mg, 31%);

453 (2.98). – MS (EI, 70 eV): m/z (%) = 340 (100) [M]⁺,

m. p.: 97 ^◦C. – ¹H NMR (250 MHz, CDCl₃): δ = 1.39

179 (79), 163 (40), 147 (40), 134 (86). – HRMS (EI): m/z =

(s, 9H, C(CH₃)₃), 1.42 (d, ³J = 6.3 Hz, 6H, CH(CH₃)₂),

340.178405 (calcd. 340.17814 for C₂₀H₂₄N₂O₃, [M]⁺). –

2.28 (s, 3H, CH₃), 2.57 (s, 3H, CH₃), 5.28 – 5.43 (sept,

Anal. for C₂₀H₂₄N₂O₃(340.42): calcd. C 70.56, H 7.11, N

8.23; found C 69.29, H 7.13, N 7.85.

³J = 6.3 Hz, 1H, CH), 6.77 (s, 1H, Ar), 7.54 – 7.57 (m,

2H, N=NAr), 7.81 – 7.84 (m, 2H, N=NAr), 11.30 ppm (s,

1H, OH). – ¹³C NMR (63 MHz, CDCl₃): δ = 17.5, 20.2,

Methyl 3,4,6-trimethyl-5-((4-tert-butylphenyl)diazenyl)-

salicylate (3r)

21.9, 31.3 (CH₃), 35.0 (C_tBu), 69.9 (CH_iPr), 111.9 (C_Ar),

118.1, 122.2, 126.0 (CH_Ar), 135.9, 137.1 (C_ArCH₃), 145.7,

150.6 (C_ArN=N), 154.5 (C_Ar), 161.5 (C_ArOH), 171.1 ppm

Starting with 2d (333 mg, 1.0 mmol), 4c (412 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3r was isolated as a red solid (106 mg, 30%);

m. p.: 137 – 139 ^◦C. – ¹H NMR (250 MHz, CDCl₃): δ = 1.39

(s, 9H, C(CH₃)₃), 2.15 (s, 3H, CH₃), 2.24 (s, 3H, CH₃),

2.39 (s, 3H, CH₃), 3.97 (s, 3H, OCH₃), 7.56 – 7.59 (m,

2H, N=NAr), 7.83 – 7.87 (m, 2H, N=NAr), 11.49 ppm (s,

1H, OH). – ¹³C NMR (63 MHz, CDCl₃): δ = 11.7, 15.7,

17.3 (CH₃), 31.3 (C(CH₃)₃), 35.0 (C(CH₃)₃), 52.2 (OCH₃),

110.6 (C_Ar), 122.3 (CH_Ar), 123.8 (C_Ar), 126.1 (CH_Ar),

130.0, 135.7 (C_ArCH₃), 146.5, 150.3 (C_ArN=N), 154.8 (C_Ar),

159.6 (C_ArOH), 172.7 ppm (COOCH₃). – IR (ATR, cm⁻¹):

(COOiPr). – IR (ATR, cm⁻¹): ν = 3037 (w), 2964 (m), 1660

˜

(s), 1460 (m), 1213 (m), 1099 (s), 800 (m). – MS (EI, 70 eV):

m/z (%) = 368 (100) [M]⁺, 308 (37), 251 (31), 165 (89),

147 (39). – HRMS (EI): m/z = 368.20992 (calcd. 368.20944

for C₂₂H₂₈N₂O₃, [M]⁺). – Anal. for C₂₂H₂₈N₂O₃(368.47):

calcd. C 71.71, H 7.66, N 7.60; found C 71.82, H 7.82, N

7.02.

Ethyl 4,6-dimethyl-5-(4⁰-n-decylphenyl)diazenyl-salicylate

(3u)

Starting with 2e (417 mg, 1.0 mmol), 4b (412 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3u was isolated as a red solid (100 mg, 23%);

m. p.: 42 – 43 ^◦C. – ¹H NMR (300 MHz, CDCl₃): δ = 0.87 (t,

³J = 7.0 Hz, 3H, CH₂CH₃), 1.24 – 1.55 (m, 19H, OCH₂CH₃,

8 × CH₂), 1.61 – 1.70 (m, 2H, CH₂Ar), 2.26 (CH₃), 2.27

(CH₃), 4.44 (q, ³J = 7.2 Hz, 2H, OCH₂), 6.75 (s, 1H, H-

˜

ν = 3052 (w), 2966 (m), 1651 (s), 1435 (m), 1260 (s),

1102 (s), 805 (s). – HRMS ((+)-ESI): m/z = 355.20203

(calcd. 355.20162 for C₂₁H₂₇N₂O₃, [M+H]⁺). – Anal. for

C₂₁H₂₇N₂O₃(354.44): calcd. C 71.16, H 7.39, N 7.90; found

C 71.44, H 7.41, N 7.58.

Ethyl 4,6-dimethyl-5-((4-tert-butylphenyl)diazenyl)-

salicylate (3s)

3

0

5), 7.31 (d, J = 8.5 Hz, 2H, CH_Ar), 7.78 (d, J = 8.5 Hz,

2H, CH_Ar), 11.24 ppm (s, 1H, OH). – ¹³C NMR (63 MHz,

0

Starting with 2d (333 mg, 1.0 mmol), 4b (412 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3s was isolated as a red solid (130 mg, 37%); m. p.:

62 – 64 ^◦C. – ¹H NMR (250 MHz, CDCl₃): δ = 1.39 (s,

9H, C(CH₃)₃), 1.44 (t, ³J = 7.1 Hz, 2H, CH₂CH₃), 2.28

CDCl₃): δ = 14.1, 14.2 (CH₂CH₃), 17.4, 20.3 (CH₃) 22.7,

29.3, 29.3, 29.5, 29.6, 29.6, 31.4, 31.9, 35.9 (CH₂), 61.7

0

(OCH₂), 111.6 (C-3), 118.2 (CH_Ar), 122.4, 129.1 (CH_Ar),

136.1, 137.2 (C_ArCH₃), 145.7 (C-1⁰), 146.6 (C-1) 150.9

(C_ArC₁₀H₂₁), 161.6 (COH), 171.6 ppm (C=O). – IR (ATR,

3

(s, 3H, CH₃), 2.58 (s, 3H, CH₃), 4.46 (q, J = 7.1 Hz, 2H,

cm⁻¹): ν = 2997 (w), 2949 (w), 2918 (s), 2847 (m), 1910

˜

CH₂CH₃), 6.77 (s, 1H, Ar), 7.54 – 7.58 (m, 2H, N=NAr),

(w), 1647 (s), 1601 (w), 1567 (m), 1465 (m), 1444 (w), 1428

(w), 1399 (w), 1374 (m), 1344 (s), 1309 (m), 1244 (s), 1182

(w), 1167 (m), 1146 (w), 1112 (w), 1080 (m), 1048 (w),

1032 (w), 1011 (m). – UV/Vis (CH₂Cl₂, nm): λ_max(logε) =

245, 337, 450. – HRMS ((+)-ESI): m/z = 439.29545 (calcd.

439.29552 for C₂₇H₃₉N₂O₃, [M+H]⁺).

7.81 – 7.85 (m, 2H, N=NAr), 11.28 ppm (s, 1H, OH). – ¹³

C

NMR (75 MHz, CDCl₃): δ = 14.2, 17.4, 20.3, 31.3 (CH₃),

35.0 (C_tBut), 61.7 (CH₂), 111.5 (C_Ar), 118.1, 122.2, 126.0

(CH_Ar), 136.1, 137.2 (C_ArCH₃), 145.7, 150.5 (C_ArN=N),

154.6 (C_Ar), 161.6 (C_ArOH), 171.6 ppm (COOCH₂CH₃).

– IR (ATR, cm⁻¹): ν = 2975 (w), 2953 (w), 1651 (s),

˜

1473 (m), 1242 (s), 1084 (m), 806 (m). – MS (EI, 70 eV):

m/z (%) = 354 (100) [M]⁺, 308 (37), 251 (41), 193 (77), 147

(43). – HRMS (EI): m/z = 354.193642 (calcd. 354.19379

for C₂₁H₂₆N₂O₃, [M]⁺). – Anal. for C₂₁H₂₆N₂O₃(354.44):

Methyl 4,6-dimethyl-3-(2-phenylethyl)-5-(4⁰-methoxy-

phenyl)diazenyl-salicylate (3v)

Starting with 2f (306 mg, 1.0 mmol), 4i (547 mg,

calcd. C 71.16, H 7.39, N 7.90; found C 71.25, H 7.64, N 1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

1

7.80.

CH₂Cl₂, 3v was isolated as a red oil (100 mg, 23%). – H

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938

J. Hefner et al. · Functionalized Diaryldiazenes

NMR (300 MHz, CDCl₃): δ = 2.10 (s, 3H, CH₃), 2.37 (s, 2H, OCH₂), 6.75 (s, 1H, H-5), 7.01 (d, ³J = 9.1 Hz, 2H,

3

0

3H, CH₃), 2.78 – 2.84 (m, 2H, CH₂), 2.99 – 3.05 (m, 2H, CH_Ar), 7.86 (d, J = 9.1 Hz, 2H, CH_Ar), 11.22 ppm (s, 1H,

CH₂), 3.90 (s, 3H, OCH₃), 3.97 (s, 3H, OCH₃), 7.03 (d, OH). – ¹³C NMR (63 MHz, CDCl₃): δ = 14.2, 17.3 (CH₃)

³J = 9.1 Hz, 2H, CH_Ar), 7.16 – 7.32 (m, 5H, Ar), 7.88 (d, 20.2 (OCH₂CH₃), 55.6 (OCH₃), 61.7 (OCH₂), 111.5 (C-3),

³J = 9.1 Hz, 2H, CH_Ar), 11.46 ppm (s, 1H, OH). – ¹³C NMR 114.2 (CH_Ar) 118.1 (CH_Ar), 124.2 (CH_Ar), 135.7, 137.2

0

(75 MHz, CDCl₃): δ = 15.0, 17.4 (CH₃), 28.7, 35.0 (CH₂), (C_ArCH₃), 145.6 (C-1), 147.0 (C-1⁰), 161.4, 162.0 (C–O),

52.2, 55.6 (OCH₃), 110.9 (C-3), 114.2, 124.3 (CH_Ar), 125.8 171.6 ppm (C=O). – IR (ATR, cm⁻¹): ν = 3002 (w), 2966

(CH_Ar), 127.4 (CH₂Ar), 128.3, 128.4 (CH_Ar), 129.8, 135.4 (w), 2924 (w), 2870 (w), 2834 (w), 1661 (s), 1603 (m), 1583

(C_ArCH₃), 142.4 (C_Ar), 146.6 (C-1), 146.9 (C-1⁰), 159.4, (m), 1558 (m), 1504 (m), 1469 (m), 1449 (m), 1395 (m),

˜

0

162.2 (C-O), 172.7 ppm (C=O). – IR (ATR, cm⁻¹): ν = 1369 (m), 1338 (m), 1234 (s), 1198 (w), 1181 (m), 1162 (m),

˜

3060 (w), 3024 (w), 3000 (w), 2950 (w), 2837 (w), 1731 1147 (m), 1103 (m), 1079 (m), 1051 (w), 1030 (m), 1017 (s).

(w), 1653 (s), 1599 (s), 1583 (m), 1562 (w), 1502 (s), 1438 – UV/Vis (CH₂Cl₂, nm): λ_max(logε) = 245, 340, 444. – MS

(s), 1392 (m), 1353 (m), 1312 (m), 1296 (w), 1247 (s), 1209 (EI, 70 eV): m/z (%) = 328 (100) [M]⁺, 299 (29), 283 (21),

(s), 1176 (m), 1141 (s), 1103 (w), 1029 (s). – MS (EI, 70 eV): 282 (70), 281 (61), 254 (27), 193 (35), 165 (24), 147 (41),

m/z (%) = 418 (40) [M]⁺, 295 (31), 267 (50), 176 (100), 107 (60), 77 (22). – HRMS (EI): m/z = 328.141515 (calcd.

123 (63), 122 (32), 108 (69), 107 (38), 92 (22), 91 (81) 77 328.14176 for C₁₈H₂₀N₂O₄, [M]⁺).

(39), 69 (22), 65 (24), 57 (21), 44 (22), 43 (21). – HRMS

Methoxyethyl 4,6-dimethyl-5-(4⁰-methoxyphenyl)diazenyl-

salicylate (3y)

(EI): m/z = 418.189312 (calcd. 418.18871 for C₂₅H₂₆N₂O₄,

[M]⁺).

Starting with 2f (306 mg, 1.0 mmol), 4k (457 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

Methyl 5-(4⁰-methoxyphenyl)diazenyl-3,4,6-trimethyl-

salicylate (3w)

CH₂Cl₂, 3y was isolated as a red solid (117 mg, 33%); m. p.:

Starting with 2f (306 mg, 1.0 mmol), 4c (412 mg, 77 – 79 ^◦C. – ¹H NMR (300 MHz, CDCl₃): δ = 2.26 (s, 3H,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of CH₃), 2.56 (s, 3H, CH₃), 3.40 (s, 3H, CH₂OCH₃), 3.72 (t,

CH₂Cl₂, 3w was isolated as a red solid (118 mg, 36%); ³J = 4.7 Hz, 2H, CH₂), 3.88 (s, 3H, OCH₃), 4.52 (t, ³J =

m. p.: 131 – 132 ^◦C. – ¹H NMR (300 MHz, CDCl₃): δ = 2.13 4.7 Hz, 2H, CH₂), 6.75 (s, 1H, H-5), 7.01 (d, ³J = 9.1 Hz,

(s, 3H, CH₃), 2.23 (s, 3H, CH₃), 2.36 (s, 3H, CH₃), 3.89 2H, CH_Ar), 7.86 (d, ³J = 9.1 Hz, 2H, CH_Ar), 10.85 ppm

0

(s, 3H, OCH₃), 3.95 (s, 3H, OCH₃), 7.02 (d, ³J = 8.9 Hz, (s, 1H, OH). – ¹³C NMR (63 MHz, CDCl₃): δ = 17.2 20.2

3

0

2H, CH_Ar) 7.88 (d, J = 8.9 Hz, 2H, CH_Ar), 11.44 ppm (s, (CH₃), 55.6, 58.9 (OCH₃), 64.3, 70.0 (CH₂), 111.7 (C-3),

1H, OH). – ¹³C NMR (63 MHz, CDCl₃): δ = 11.7, 15.6, 114.2 (CH_Ar), 118.1 (CH_Ar), 124.2 (CH_Ar), 135.9, 137.2

17.2 (CH₃), 52.1, 55.6 (OCH₃), 110.5 (C-3), 114.2, 123.7 (C_ArCH₃), 145.7 (C-1⁰), 147.0 (C-1), 161.0, 162.0 (C–O),

0

(C_ArCH₃), 124.3 (CH_Ar), 129.6, 135.6 (C_ArCH₃), 146.4 (C- 171.0 ppm (C=O). – IR (ATR, cm⁻¹): ν = 2981 (w), 2925

1⁰), 146.9 (C-1), 159.3, 162.2 (C–O), 172.7 ppm (C=O). – (w), 2884 (w), 2842 (w), 2813 (w), 1650 (m), 1600 (m),

˜

0

IR (ATR, cm⁻¹): ν = 3016 (w), 2958 (w), 2842 (w), 2743 1582 (m), 1556 (m), 1502 (m), 1468 (m), 1456 (w), 1435

˜

(w), 2581 (w), 1649 (m), 1600 (m), 1582 (m), 1503 (m), (m), 1410 (m), 1382 (m), 1375 (m), 1345 (m), 1305 (s),

1442 (m), 1429 (m), 1398 (m), 1362 (m), 1311 (m), 1297 1243 (s), 1198 (m), 1180 (m), 1166 (m), 1143 (w), 1129 (m),

(m), 1251 (s), 1212 (s), 1199 (m), 1179 (m), 1145 (m), 1099 1099 (m), 1079 (m), 1055 (w), 1026 (s). – MS (EI, 70 eV):

(m), 1047 (w), 1020 (s). – MS (EI, 70 eV): m/z (%) = 328 m/z (%) = 358 (100) [M]⁺, 299 (25), 282 (71), 281 (53),

(100) [M]⁺, 296 (64), 295 (38), 268 (21), 240 (26), 193 254 (27), 163 (28), 147 (36), 107 (46), 59 (32). – HRMS

(66), 161 (81), 135 (26), 108 (27), 107 (96), 105 (27), 92 (EI): m/z = 358.151695 (calcd. 358.15232 for C₁₉H₂₂N₂O₅,

(49), 91 (24), 79 (27), 78 (24), 77 (86), 64 (23). – HRMS [M]⁺).

(EI): m/z = 328.141857 (calcd. 328.14176 for C₁₈H₂₀N₂O₄,

Methyl 3-(n-chloropropyl)-4,6-dimethyl-5-(4⁰-methoxy-

phenyl)diazenyl-salicylate (3z)

[M]⁺).

Ethyl 4,6-dimethyl-5-(4⁰-methoxyphenyl)diazenyl-salicylate

Starting with 2f (490 mg, 1.6 mmol), 4h (805 mg,

(3x)

2.4 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

Starting with 2f (306 mg, 1.0 mmol), 4b (412 mg, CH₂Cl₂, 3z was isolated as a red solid (137 mg, 22%); m. p.:

1

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of 95 – 96 ^◦C. – H NMR (300 MHz, CDCl₃): δ = 1.97 – 2.06

CH₂Cl₂, 3x was isolated as a red solid (101 mg, 31%); (m, 2H, CH₂), 2.34 (s, 3H, CH₃), 2.71 (s, 3H, CH₃), 2.88

1

m. p.: 77 – 78 ^◦C. – H NMR (300 MHz, CDCl₃): δ = 1.42 (t, ³J = 7.6 Hz, 2H, CH₂Ar), 3.61 (t, ³J = 7.0 Hz, 2H,

(t, ³J = 7.2 Hz, 3H, OCH₂CH₃), 2.26 (s, 3H, CH₃), 2.55 CH₂Cl), 3.90 (s, 3H, OCH₃), 3.96 (s, 3H, OCH₃), 7.03 (d,

(s, 3H, CH₃), 3.89 (s, 3H, OCH₃), 4.44 (q, ³J = 7.2 Hz, ³J = 8.8 Hz, 2H, CH_Ar), 7.88 (d, J = 8.8 Hz, 2H, CH_Ar),

3

0

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J. Hefner et al. · Functionalized Diaryldiazenes

939

11.45 ppm (s, 1H, OH). – ¹³C NMR (63 MHz, CDCl₃): δ = 172.7 ppm (C=O). – IR (ATR, cm⁻¹): ν = 3016 (w), 2956

15.1, 17.3 (CH₃), 23.7, 31.8, 45.2 (CH₂), 52.2, 55.6 (OCH₃), (w), 2922 (w), 2851 (w), 1650 (s), 1599 (w), 1586 (w), 1563

˜

0

110.9 (C-3), 114.2, 124.4 (CH_Ar), 126.5 (C-5), 130.0, 135.5 (w), 1487 (w), 1441 (m), 1332 (m), 1354 (m), 1314 (m), 1255

(C_ArCH₃), 146.7 (C-1⁰), 146.9 (C-1), 159.4, 162.3 (C–O), (s), 1213 (s), 1198 (m), 1177 (w), 1151 (m), 1001 (w), 1088

172.6 ppm (C=O). – IR (ATR, cm⁻¹): ν = 3014 (w), 2 959 (m), 1030 (m), 1007 (m). – MS (EI, 70 eV): m/z (%) = 344

˜

(w), 2870 (w), 2836 (w), 1651 (s), 1602 (m), 1585 (m), (100) [M]⁺, 312 (68), 311 (32), 265 (24), 193 (63), 161 (83),

1574 (w), 1564 (w), 1558 (w), 1504 (m), 1454 (m), 1435 139 (23), 124 (30), 123 (34). – HRMS (EI): m/z = 344.11891

(m), 1395 (m), 1360 (m), 1309 (m), 1294 (w), 1267 (w), (calcd. 344.11891 for C₁₈H₂₀N₂O₃S, [M]⁺).

1247 (s), 1227 (w), 1211 (s), 1176 (m), 1141 (s), 1103 (w),

Methyl 4,6-dimethyl-3-ethyl-5-(4⁰-methylthiophenyl)-

diazenyl-salicylate (3ac)

1088 (w), 1071 (w), 1048 (w), 1026 (s). – HRMS ((+)-ESI):

m/z = 391.14194 (calcd. 391.14191 for C₂₀H₂₄ClN₂O₃S,

[M+H; ³⁵Cl]⁺).

Starting with 2g (323 mg, 1.0 mmol), 4e (433 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

Ethyl 4,6-dimethyl-5-(4⁰-methylthiophenyl)diazenyl-

salicylate (3aa)

CH₂Cl₂, 3ac was isolated as a red solid (140 mg, 39%);

1

m. p.: 86 – 88 ^◦C. – H NMR (300 MHz, CDCl₃): δ = 1.13

Starting with 2g (323 mg, 1.0 mmol), 4b (412 mg, (t, ³J = 7.5 Hz, 3H, CH₂CH₃), 2.18 (s, 3H, SCH₃), 2.37

3

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of (s, 3H, CH₃), 2.55 (s, 3H, CH₃), 2.76 (q, J = 7.6 Hz, 2H,

CH₂Cl₂, 3aa was isolated as a red solid (132 mg, 38%); CH₂), 3.95 (s, 3H, OCH₃), 7.36 (d, ³J = 8.7 Hz, 2H, CH_Ar),

0

m. p.: 85 – 87 ^◦C. – H NMR (300 MHz, CDCl₃): δ = 1.43 7.82 (d, ³J = 8.7 Hz, 2H, CH_Ar), 11.42 ppm (s, 1H, OH).

1

0

(t, ³J = 7.2 Hz, 3H, OCH₂CH₃), 2.28 (s, 3H, SCH₃), 2.55

–

¹³C NMR (75 MHz, CDCl₃): δ = 13.2 (CH₂CH₃), 14.9

(s, 3H, CH₃), 2.59 (s, 3H, CH₃), 4.45 (q, ³J = 7.2 Hz, (SCH₃), 15.3, 17.4 (CH₃), 19.4 (CH₂), 52.2 (OCH₃), 110.9

2H, OCH₂), 6.75 (s, 1H, H-5), 7.34 (d, ³J = 8.9 Hz, 2H, (C-3), 122.9, 126.0 (CH_Ar), 129.8, 130.0 (C_ArCH₃), 135.2

0

CH_Ar), 7.80 (d, ³J = 8.9 Hz, 2H, CH_Ar), 11.25 ppm (s, (C-1), 143.1 (C-1⁰), 146.5 (C-5), 149.8 (C_ArSCH₃), 159.4

0

1H, OH). – ¹³C NMR (75 MHz, CDCl₃): δ = 14.2 (SCH₃), (COH), 172.7 ppm (C=O). – IR (ATR, cm⁻¹): ν = 3013

˜

15.4, 17.4 (CH₃), 20.5 (OCH₂CH₃), 61.8 (OCH₂), 111.6 (w), 2971 (w), 2954 (w), 2931 (w), 2872 (w), 1648 (s), 1586

0

(C-3), 118.2 (CH_Ar), 122.9, 126.1 (CH_Ar), 136.6, 137.3 (m), 1564 (m), 1488 (m), 1440 (m), 1429 (m), 1393 (m),

(C_ArCH₃), 142.8 (C-1), 145.5 (C-1⁰), 150.0 (C_ArSCH₃), 1360 (s), 1317 (s), 1290 (w), 1270 (m), 1239 (w), 1212 (s),

161.7 (COH), 171.6 ppm (C=O). – IR (ATR, cm⁻¹): ν = 1198 (s), 1177 (w), 1153 (m), 1108 (m), 1086 (m), 1048

˜

2960 (w), 2913 (w), 1909 (w), 1659 (m), 1651 (m), 1585 (w), 1035 (m), 1007 (w). – MS (EI, 70 eV): m/z (%) = 358

(m), 1556 (m), 1464 (m), 1444 (m), 1429 (m), 1393 (m), (100) [M]⁺, 327 (25), 326 (80), 325 (49), 311 (25), 279

1368 (m), 1336 (m), 1306 (m), 1249 (s), 1218 (w), 1198 (35), 207 (78), 191 (27), 175 (45), 139 (31), 124 (33), 123

(w), 1163 (m), 1106 (w), 1079 (m), 1050 (w), 1008 (s). (34). – HRMS (EI): m/z = 358.135016 (calcd. 358.13456 for

– UV/Vis (CH₂Cl₂, nm): λ_max(logε) = 245, 356, 451. – C₁₉H₂₂N₂O₃S, [M]⁺).

MS (EI, 70 eV): m/z (%) = 344 (100) [M]⁺, 315 (30), 298

(52), 297 (61), 251 (36), 193 (39), 165 (36), 163 (34), 147

(67), 139 (33), 124 (50), 123 (52), 91 (26), 45 (30), 44

2-Methoxyethyl 4,6-dimethyl-5-(4⁰-methylthiophenyl)-

diazenyl-salicylate (3ad)

(42), 43 (26). – HRMS ((+)-ESI): m/z = 367.10852 (calcd.

Starting with 2g (323 mg, 1.0 mmol), 4k (457 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3ad was isolated as a red solid (120 mg, 32%);

367.10868 for C₁₈H₂₀N₂O₃S, [M+Na]⁺).

Methyl 5-(4⁰-methylthiophenyl)diazenyl-3,4,6-trimethyl-

salicylate (3ab)

1

m. p.: 85 – 86 ^◦C. – H NMR (300 MHz, CDCl₃): δ = 2.29

(s, 3H, SCH₃), 2.54 (s, 3H, CH₃), 2.60 (s, 3H, CH₃), 3.40

Starting with 2g (323 mg, 1.0 mmol), 4c (412 mg, (s, 3H, OCH₃), 3.72 (t, ³J = 4.7 Hz, 2H, CH₂), 4.52 (t, ³J =

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of 4.7 Hz, 2H, CH₂), 6.75 (s, 1H, H-5), 7.34 (d, ³J = 8.7 Hz,

3

0

CH₂Cl₂, 3ab was isolated as a red solid (190 mg, 55%); 2H, CH_Ar), 7.80 (d, J = 8.7 Hz, 2H, CH_Ar), 10.88 ppm (s,

m. p.: 91 – 93 ^◦C. – H NMR (300 MHz, CDCl₃): δ = 2.15 1H, OH). – ¹³C NMR (75 MHz, CDCl₃): δ = 15.4 (SCH₃),

1

(s, 3H, CH₃), 2.23 (s, 3H, SCH₃), 2.39 (s, 3H, CH₃), 2.55 17.2, 20.5 (CH₃), 58.9 (OCH₃), 64.3, 70.0 (CH₂), 111.8

(s, 3H, CH₃), 3.99 (s, 3H, OCH₃), 7.36 (d, ³J = 8.7 Hz, 2H, (C-3), 118.2 (CH_Ar), 122.9, 126.0 (CH_Ar), 136.8, 137.4

0

CH_Ar), 7.82 (d, J = 8.7 Hz, 2H, CH_Ar), 11.48 ppm (s, 1H, (C_ArCH₃), 142.8 (C-1), 145.5 (C-1⁰), 150.0 (C_ArSCH₃),

3

0

OH). – ¹³C NMR (75 MHz, CDCl₃): δ = 11.7 (SCH₃), 15.4, 161.2 (COH), 170.9 ppm (C=O). – IR (ATR, cm⁻¹): ν =

15.8, 17.3 (CH₃), 52.2 (OCH₃), 110.6 (C-3), 123.0 (CH_Ar), 3009 (w), 2964 (w), 2914 (w), 2879 (w), 2850 (w), 2809 (w),

˜

0

123.8 (C_ArCH₃), 126.0 (CH_Ar), 130.1, 135.8 (C_ArCH₃), 2736 (w), 1657 (s), 1598 (w), 1587 (w), 1574 (m), 1568 (m),

143.1 (C-1), 146.3 (C-1⁰), 149.8 (C_ArSCH₃), 159.6 (COH), 1475 (m), 1449 (m), 1435 (m), 1386 (s), 1375 (s), 1348 (s),

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940

J. Hefner et al. · Functionalized Diaryldiazenes

1310 (s), 1254 (s), 1227 (w), 1197 (m), 1168 (s), 1130 (s), m/z = 407.11897 (calcd. 407.11907 for C₂₀H₂₄N₂O₃ClS,

1085 (s), 1029 (s). – MS (EI, 70 eV): m/z (%) = 374 (100) [M+H; ³⁵Cl]⁺).

[M]⁺, 315 (30), 298 (62), 297 (45), 251 (38), 223 (21), 163

Methyl 4,6-dimethyl-3-(n-propyl)-5-(4⁰-methylthiophenyl)-

diazenyl-salicylate (3ag)

(24), 147 (44), 124 (21), 123 (26), 59 (42). – HRMS ((+)-

ESI): m/z = 397.1192 (calcd. 397.11925 for C₁₉H₂₂N₂O₄S,

[M+Na]⁺).

Starting with 2g (323 mg, 1.0 mmol), 4f (454 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3ag was isolated as a red solid (82 mg, 22%); m. p.:

80 – 82 ^◦C. – ¹H NMR (300 MHz, CDCl₃): δ = 1.00 (t, ³J =

7.4 Hz, 3H, CH₂CH₃), 1.50 – 1.59 (m, 2H, CH₂CH₃), 2.17

(s, 3H, SCH₃), 2.36 (s, 3H, CH₃), 2.55 (s, 3H, CH₃), 2.70

Methyl 3-allyl-4,6-dimethyl-5-(4⁰-methylthiophenyl)-

diazenyl-salicylate (3ae)

Starting with 2g (323 mg, 1.0 mmol), 4l (451 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3ae was isolated as a red solid (110 mg, 30%);

(t, ³J = 8.1 Hz, 2H, CH₂Ar), 3.95 (s, 3H, OCH₃), 7.36 (d,

1

m. p.: 61 – 63 ^◦C. – H NMR (300 MHz, CDCl₃): δ = 2.16

3

³J = 8.6 Hz, 2H, CH_Ar), 7.82 (d, J = 8.6 Hz, 2H, CH_Ar),

11.41 ppm (s, 1H, OH). ). – ¹³C NMR (75 MHz, CDCl₃):

δ = 14.4 (CH₂CH₃), 15.2, 15.4 (CH₃), 17.4 (SCH₃), 22.2,

0

(s, 3H, SCH₃), 2.39 (s, 3H, CH₃), 2.55 (s, 3H, CH₃), 3.51 (d,

³J = 5.9 Hz, 2H, CH₂Ar), 3.96 (s, 3H, OCH₃), 4.92 – 5.02

(m, 2H, CH₂=CH), 5.89 – 6.02 (m, 1H, CH=CH₂), 7.36

0

28.2 (CH₂), 52.2 (OCH₃), 110.8 (C-3), 122.9, 126.1 (CH_Ar),

(d, ³J = 8.9 Hz, 2H, CH_Ar), 7.82 (d, ³J = 8.9 Hz, 2H,

0

128.4, 129.8 (C_ArCH₃), 135.6 (C-5), 143.1 (C-1), 146.5 (C-

CH_Ar), 11.46 ppm (s, 1H, OH). – ¹³C NMR (75 MHz,

0

1⁰), 149.9 (C_ArSCH₃), 159.6 (COH), 172.7 ppm (C=O). – IR

CDCl₃): δ = 15.2 (SCH₃), 15.3, 17.4 (CH₃), 30.2 (CH₂Ar),

(ATR, cm⁻¹): ν = 2956 (m), 2927 (w), 2867 (w), 1715 (w),

˜

0

52.2 (OCH₃), 111.0 (C-3), 114.8 (CH₂=CH), 123.0 (CH_Ar),

1651 (s), 1584 (m), 1555 (m), 1489 (w), 1430 (s), 1388 (m),

1360 (s), 1312 (m), 1255 (s), 1211 (s), 1196 (w), 1172 (m),

1148 (w), 1113 (m), 1089 (m), 1037 (m), 1007 (w). – MS

(EI, 70 eV): m/z (%) = 372 (100) [M]⁺, 340 (51), 339 (28),

325 (23), 293 (24), 221 (48), 205 (31), 189 (25), 139 (33),

124 (37). – HRMS (EI): m/z = 372.15009 (calcd. 372.15021

for C₂₀H₂₄N₂O₃S, [M]⁺).

0

125.2 (C_ArCH₃), 126.0 (CH_Ar), 130.8 (C_ArCH₃), 135.4

(CH=CH₂), 136.3 (C-5), 143.2 (C-1), 146.5 (C-1⁰), 149.8

(C_ArSCH₃), 159.5 (COH), 172.6 ppm (C=O). – IR (ATR,

cm⁻¹): ν = 3067 (w), 2960 (w), 2924 (w), 1731 (w), 1656

˜

(s), 1584 (m), 1556 (m), 1487 (w), 1435 (s), 1390 (m), 1356

(s), 1310 (m), 1257 (s), 1214 (m), 1197 (m), 1175 (m), 1151

(w), 1088 (s), 1023 (s). – GC-MS (EI, 70 eV): m/z (%) = 370

(100) [M]⁺, 338 (30), 337 (33), 323 (43), 291 (22), 219

(45), 187 (23), 139 (27), 124 (25), 123 (24). – HRMS ((+)-

ESI): m/z = 371.1426 (calcd. 371.14239 for C₂₀H₂₃N₂O₃S,

[M+H]⁺).

Ethyl 4,6-dimethyl-5-(4⁰-ethoxycarbonylphenyl)diazenyl-

salicylate (3ah)

Starting with 2h (350 mg, 1.0 mmol), 4a (391 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3ah was isolated as a red solid (40 mg, 11%); m. p.:

122 – 123 ^◦C. – ¹H NMR (300 MHz, CDCl₃): δ = 1.42 (t,

Methyl 3-(n-chlorpropyl)-4,6-dimethyl-5-(4⁰-methylthio-

phenyl)diazenyl-salicylate (3af)

Starting with 2g (323 mg, 1.0 mmol), 4h (506 mg, ³J = 7.2 Hz, 3H, OCH₂CH₃), 2.36 (s, 3H, CH₃), 2.67 (s, 3H,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of CH₃), 3.99 (s, 3H, OCH₃), 4.41 (q, ³J = 7.1 Hz, 2H, OCH₂),

CH₂Cl₂, 3af was isolated as a red solid (315 mg, 39%); 6.77 (s, 1H, H-5), 7.86 (d, ³J = 8.9 Hz, 2H, CH_Ar), 8.18

0

m. p.: 125 – 127 ^◦C. – ¹H NMR (300 MHz, CDCl₃): δ = (d, J = 8.9 Hz, 2H, CH_Ar), 11.28 ppm (s, 1H, OH). – ¹³C

3

0

1.97 – 2.06 (m, 2H, CH₂), 2.19 (s, 3H, SCH₃), 2.36 (s, NMR (63 MHz, CDCl₃): δ = 14.3 (OCH₂CH₃), 17.5, 21.2

3H, CH₃), 2.55 (s, 3H, CH₃), 2.88 (t, ³J = 7.6 Hz, 2H, (CH₃), 52.4 (OCH₃), 61.3 (OCH₂), 118.6 (CH_Ar), 122.2,

CH₂Ar), 3.61 (t, ³J = 6.6 Hz, 2H, CH₂Cl), 3.96 (s, 3H, 130.6 (CH_Ar), 132.0 (C-3), 137.7, 138.2 (C_ArCH₃), 145.3

0

OCH₃), 7.36 (d, ³J = 8.7 Hz, 2H, CH_Ar), 7.82 (d, ³J = (C-1⁰), 155.2 (C-1), 157.1 (C_ArCOOEt), 162.4 (COH), 166.1,

0

8.7 Hz, 2H, CH_Ar), 11.48 ppm (s, 1H, OH). – ¹³C NMR 172.0 ppm (C=O). – IR (ATR, cm⁻¹): ν = 2963 (w), 2924

(75 MHz, CDCl₃): δ = 15.2 (SCH₃), 15.3, 17.4 (CH₃) 23.7 (w), 2906 (w), 2874 (w), 2849 (w), 1711 (s), 1667 (s), 1644

(CH₂Ar), 31.8 (CH₂), 45.1 (CH₂Cl), 52.3 (OCH₃), 110.9 (w), 1601 (w), 1566 (m), 1501 (w), 1470 (w), 1435 (s), 1407

˜

0

(C-3), 123.0, 126.0 (CH_Ar), 126.6, 130.5 (C_ArCH₃), 135.6 (w), 1392 (w), 1361 (s), 1310 (m), 1275 (s), 1243 (s), 1221

(C-5), 143.3 (C-1), 146.5 (C-1⁰), 149.8 (C_ArSCH₃), 159.6 (m), 1198 (m), 1161 (m), 1142 (m), 1129 (m), 1105 (w),

(COH), 172.6 ppm (C=O). – IR (ATR, cm⁻¹): ν = 2959 1092 (m), 1082 (m), 1009 (m). – UV/Vis (CH₂Cl₂, nm):

˜

(w), 2921 (w), 2869 (w), 1934 (w), 1705 (w), 1651 (s),

λ_max(logε) = 245, 348, 468. – MS (EI, 70 eV): m/z (%) =

1586 (m), 1563 (m), 1490 (w), 1432 (s), 1396 (s), 1359 (s), 356 (65) [M]⁺, 179 (100), 147 (76), 120 (27). – HRMS

1316 (s), 1294 (w), 1266 (m), 1247 (m), 1211 (s), 1176 (m), (EI): m/z = 356.136569 (calcd. 356.13667 for C₁₉H₂₀N₂O₅,

1141 (m), 1087 (s), 1049 (w), 1030 (m). – HRMS ((+)-ESI): [M]⁺).

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J. Hefner et al. · Functionalized Diaryldiazenes

941

Methyl 5-((4-chlorophenyl)diazenyl)-4,6-dimethyl-salicylate

(3ai)

(m, 2H, N=NAr), 11.10 ppm (s, 1H, OH). – ¹³C NMR

(63 MHz, CDCl₃): δ = 12.5, 16.9 (CH₃), 52.4, 60.3 (OCH₃),

112.5 (C_Ar), 123.7, 129.4 (CH_Ar), 130.0, 130.3, 137.1, 145.1

(CAr), 145.2, 150.9 (C_ArN=N), 155.3 (C_ArOH), 171.9 ppm

Starting with 2i (311 mg, 1.0 mmol), 4a (391 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3ai was isolated as a red solid (140 mg, 44%);

(COOCH₃). – IR (ATR, cm⁻¹): ν = 3031 (w), 2943 (w),

˜

1654 (s), 1438 (s), 1217 (m), 1114 (m), 1071 (m), 834

(m), 802 (m). – MS (EI, ): m/z (%) = 348 (34) [M;

³⁵Cl]⁺, 315 (22), 256 (25), 111 (29). – HRMS ((+)-ESI):

m/z = 349.09504 (calcd. 349.09496 for C₁₇H₁₈ClN₂O₄,

[M+H; ³⁵Cl]⁺). – Anal. for C₁₇H₁₈ClN₂O₄(348.78): calcd.

C 58.54, H 4.91, N 8.03; found C 58.79, H 5.23, N 7.52.

1

m. p.: 95 – 98 ^◦C. – H NMR (250 MHz, CDCl₃): δ = 2.32

(s, 3H, CH₃), 2.62 (s, 3H, CH₃), 3.99 (s, 3H, OCH₃),

6.77 (s, 1H, Ar), 7.47 – 7.51 (m, 2H, N=NAr), 7.79 – 7.82

(m, 2H, N=NAr), 11.25 ppm (s, 1H, OH). – ¹³C NMR

(63 MHz, CDCl₃): δ = 17.3, 20.8 (CH₃), 52.3 (OCH₃),

111.6 (C_Ar), 118.4, 123.6, 129.3 (CH_Ar), 136.8 (C_Ar), 137.5,

137.6 (C_ArCH₃), 145.0, 151.0 (C_ArN=N), 162.0 (C_ArOH),

Ethyl 5-((4-chlorophenyl)diazenyl)-4,6-dimethyl-salicylate

(3al)

171.9 ppm (COOCH₃). – IR (KBr, cm⁻¹): ν = 2992 (w),

˜

2955 (w), 1668 (s), 1444 (s), 1239 (m), 1089 (s), 833 (s).

– UV/Vis (CH₂Cl₂, nm): λ_max(logε) = 230 (3.86), 340

(3.79), 456 (1.76). – MS (GC, 70 eV): m/z (%) = 320 (29)

[M; ³⁷Cl]⁺, 318 77) ([M; ³⁵Cl]⁺, 179 (100), 147 (97), 111

(46). – HRMS (EI): m/z = 318.07708 (calcd. 318.07657 for

C₁₆H₁₅ClN₂O₃, [M; ³⁵Cl]⁺). – Anal. for C₁₆H₁₅ClN₂O₃

(318.75): calcd. C 60.29, H 4.74, N 8.79; found C 60.42, H

4.98, N 8.04.

Starting with 2i (311 mg, 1.0 mmol), 4b (412 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3al was isolated as a red solid (133 mg, 40%);

m. p.: 99 – 100 ^◦C. – ¹H NMR (250 MHz, CDCl₃): δ = 1.44

(t, ³J = 7.1 Hz, 3H, CH₂CH₃), 2.32 (s, 3H, CH₃), 2.64 (s,

3H, CH₃), 3.99 (s, 3H, OCH₃), 4.47 (q, ³J = 7.1 Hz, 2H,

CH₂CH₃), 6.77 (s, 1H, Ar), 7.47 – 7.50 (m, 2H, N=NAr),

7.79 – 7.82 (m, 2H, N=NAr), 11.33 ppm (s, 1H, OH). –

¹³C NMR (63 MHz, CDCl₃): δ = 14.2, 17.5, 20.8 (CH₃),

61.9 (CH₂), 111.7 (C_Ar), 118.4, 123.6, 129.3 (CH_Ar), 136.8

(C_Ar), 137.4, 137.6 (C_ArCH₃), 145.0, 151.0 (C_ArN=N), 162.1

Methyl 5-((4-chlorophenyl)diazenyl)-3,4,6-trimethyl-

salicylate (3aj)

(C_ArOH), 171.5 ppm (COOEt). – IR (ATR, cm⁻¹): ν = 2970

Starting with 2i (311 mg, 1.0 mmol), 4c (412 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3aj was isolated as a red solid (115 mg, 35%);

m. p.: 121 – 122 ^◦C. – ¹H NMR (250 MHz, CDCl₃): δ = 2.18

(s, 3H, CH₃), 2.24 (s, 3H, CH₃), 2.43 (s, 3H, CH₃), 3.97

(s, 3H, OCH₃), 7.48 – 7.52 (m, 2H, N=NAr), 7.81 – 7.85

(m, 2H, N=NAr), 11.53 ppm (s, 1H, OH). – ¹³C NMR

(63 MHz, CDCl₃): δ = 11.7, 15.9, 17.4 (CH₃), 52.3 (OCH₃),

110.7 (C_Ar), 123.7 (CH_Ar), 124.0 (C_Ar), 129.4 (CH_Ar), 130.8

(C_Ar), 136.0, 137.0 (C_ArCH₃), 146.0, 150.9 (C_ArN=N), 159.9

˜

(w), 2926 (w), 1659 (s), 1467 (m), 1245 (s), 1083 (m), 804

(s). – MS (GC, 70 eV): m/z (%) = 334 (39) [M; ³⁷Cl]⁺,

332 (100) [M; ³⁵Cl]⁺, 286 (46), 193 (64), 147 (88), 111

(53). – HRMS (EI): m/z = 332.09166 (calcd. 332.09222 for

C₁₇H₁₇ClN₂O₃, [M; ³⁵Cl]⁺). – Anal. for C₁₇H₁₇ClN₂O₃

(332.78): calcd. C 61.36, H 5.15, N 8.42; found C 62.00, H

4.97, N 7.90.

Methyl 5-((4-chlorophenyl)diazenyl)-3-ethyl-4,6-dimethyl-

salicylate (3am)

(C_ArOH), 172.6 ppm (COOCH₃). – IR (ATR, cm⁻¹): ν =

˜

2992 (w), 2961 (w), 1656 (s), 1438 (s), 1213 (s), 1085 (m),

833 (m), 802 (m). – MS (EI, 70 eV): m/z (%) = 334 (33)

[M; ³⁷Cl]⁺, 332 (100) [M; ³⁵Cl]⁺, 300 (52), 193 (95), 161

(78). – HRMS (EI): m/z = 332.09240 (calcd. 332.09222 for

C₁₇H₁₇ClN₂O₃, [M; ³⁵Cl]⁺). – Anal. for C₁₇H₁₇ClN₂O₃

(332.78): calcd. C 61.36, H 5.15, N 8.42; found C 60.78, H

5.17, N 8.17.

Starting with 2i (311 mg, 1.0 mmol), 4f (433 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3am was isolated as a red solid (162 mg, 47%);

1

m. p.: 61 – 63 ^◦C. – H NMR (250 MHz, CDCl₃): δ = 1.15

(t, ³J = 7.5 Hz, 3H, CH₂CH₃), 2.21 (s, 3H, CH₃), 2.40

(s, 3H, CH₃), 2.77 (q, ³J = 7.5 Hz, 2H, CH₂CH₃), 3.97

(s, 3H, OCH₃), 7.49 – 7.52 (m, 2H, N=NAr), 7.81 – 7.85

(m, 2H, N=NAr), 11.48 ppm (s, 1H, OH). – ¹³C NMR

(63 MHz, CDCl₃): δ = 13.2, 15.1, 17.5 (CH₃), 19.4 (CH₂),

52.2 (OCH₃), 111.0 (C_Ar), 123.7, 129.4 (CH_Ar), 130.0, 130.6

Methyl 5-((4-chlorophenyl)diazenyl)-3-methoxy-

4,6-dimethyl-salicylate (3ak)

Starting with 2i (311 mg, 1.0 mmol), 4d (436 mg, (C_Ar), 135.4, 137.0 (C_ArCH₃), 146.2, 150.9 (C_ArN=N), 159.8

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of (C_ArOH), 172.6 ppm (COOCH₃). – IR (ATR, cm⁻¹): ν =

˜

CH₂Cl₂, 3ak was isolated as a red solid (111 mg, 32%); 3055 (w), 2948 (w), 1653 (s), 1434 (s), 1207 (m), 1086

1

m. p.: 96 – 98 ^◦C. – H NMR (250 MHz, CDCl₃): δ = 2.24 (m), 805 (m). – MS (GC, 70 eV): m/z (%) = 348 (13) [M;

(s, 3H, CH₃), 2.44 (s, 3H, CH₃), 3.86 (s, 3H, OCH₃), 3.99 ³⁷Cl]⁺, 346 (37) [M; ³⁵Cl]⁺, 314 (23), 207 (100), 175

(s, 3H, OCH₃), 7.48 – 7.52 (m, 2H, N=NAr), 7.80 – 7.84 (20). – HRMS (EI): m/z = 346.10780 (calcd. 346.10787 for

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J. Hefner et al. · Functionalized Diaryldiazenes

C₁₈H₁₉ClN₂O₃, [M; ³⁵Cl]⁺). – Anal. for C₁₈H₁₉ClN₂O₃440.03199 for C₁₉H₂₀N₂O₃Cl⁸¹Br, [M; ⁸¹Br, ³⁵Cl]⁺),

(346.81): calcd. C 62.34, H 5.52, N 8.08; found C 61.41, H 438.033671 (calcd. 438.03403 for C₁₉H₂₀N₂O₃ClBr, [M;

5.78, N 7.74.

⁷⁹Br, ³⁷Cl]⁺).

Ethyl 4,6-dimethyl-5-(4⁰-triﬂuoromethoxyphenyl)diazenyl-

salicylate (3ap)

Methyl 5-((4-bromophenyl)diazenyl)-4,6-dimethyl-salicylate

(3an)

Starting with 2j (355 mg, 1.0 mmol), 4a (391 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3an was isolated as a red solid (73 mg, 20%); m. p.:

111 – 113 ^◦C. – ¹H NMR (250 MHz, CDCl₃): δ = 2.32 (s,

3H, CH³), 2.62 (s, 3H, CH₃), 3.99 (s, 3H, OCH₃), 6.79 (s,

1H, Ar), 7.63 – 7.67 (m, 2H, N=NAr), 7.71 – 7.75 (m, 2H,

N=NAr), 11.24 ppm (s, 1H, OH). – ¹³C NMR (75 MHz,

CDCl₃): δ = 17.4, 20.9 (CH₃), 52.3 (OCH₃), 111.6 (C_Ar),

118.5, 123.9 (CH_Ar), 125.2 (C_Ar), 132.3 (CH_Ar), 137.5,

137.7 (C_ArCH₃), 145.0, 151.4 (C_ArN=N), 162.0 (C_ArOH),

Starting with 2k (360 mg, 1.0 mmol), 4b (412 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3ap was isolated as a red solid (45 mg, 12%);

1

m. p.: 56 – 57 ^◦C. – H NMR (300 MHz, CDCl₃): δ = 1.44

(t, ³J = 7.0 Hz, 3H, OCH₂CH₃), 2.32 (s, 3H, CH₃), 2.63

(s, 3H, CH₃), 4.46 (q, ³J = 7.2 Hz, 2H, OCH₂), 6.76 (s,

1H, H-5), 7.35 (d, ³J = 8.9 Hz, 2H, CH_Ar), 7.89 (d, ³J =

0

8.9 Hz, 2H, CH_Ar), 11.30 ppm (s, 1H, OH). – ¹³C NMR

0

(63 MHz, CDCl₃): δ = 14.2 (OCH₂CH₃), 17.5, 20.8 (CH₃),

61.9 (OCH₂), 111.8 (C-3), 118.4 (CH_Ar), 118.7 (C_ArCH₃),

172.0 ppm (COOCH₃). – IR (KBr, cm⁻¹): ν = 3037 (w),

˜

0

121.4 (CH_Ar), 122.1 (C_ArCH₃), 123.9 (CH_Ar), 137.4, (C-

1), 137.7 (C-1⁰), 145.0 (C_ArOCF₃), 150.8 (J_C,F=2.2 Hz,

OCF₃), 162.1 (COH), 171.5 ppm (C=O). – ¹⁹F NMR

(282 MHz, CDCl₃): δ = −57.73 ppm (CF₃). – IR (ATR,

2959 (w), 1663 (s), 1442 (s), 1235 (m), 1083 (m), 834 (s),

806 (m). – UV/Vis (CH₂Cl₂, nm): λ_max(logε) = 231 (4.12),

341 (4.11), 461 (3.15). – MS (EI, 70 eV): m/z (%) = 364

(26) [M; ⁸¹Br]⁺, 362 (27) [M; ⁷⁹Br]⁺, 173 (100), 112

(76). – HRMS (EI): m/z = 362.02605 (calcd. 362.02606 for

C₁₆H₁₅BrN₂O₃, [M; ⁷⁹Br]⁺). – Anal. for C₁₆H₁₅BrN₂O₃

(363.21): calcd. C 52.91, H 4.16, N 7.71; found C 52.16, H

4.17, N 7.42.

cm⁻¹): ν = 2952 (w), 2931 (w), 2906 (w), 2854 (w),

˜

1909 (w), 1651 (m), 1592 (w), 1564 (m), 1498 (w), 1475

(m), 1449 (m), 1430 (m), 1397 (m), 1374 (m), 1349 (m),

1304 (w), 1245 (s), 1212 (s), 1199 (s), 1156 (s), 1096

(m), 1081 (m), 1028 (w), 1011 (m). – UV/Vis (CH₂Cl₂,

nm): λ_max(logε) = 245, 339, 453. – MS (GC, 70 eV):

m/z (%) = 382 (100) [M]⁺, 353 (25), 336 (42), 335 (46),

193 (43), 165 (28), 147 (61), 95 (26), 91 (24). – HRMS (EI):

m/z = 382.113612 (calcd. 382.11349 for C₁₈H₁₇F₃N₂O₄,

[M]⁺).

Methyl 3-(n-chloropropyl)-4,6-dimethyl-5-(4⁰-bromo-

phenyl)diazenyl-salicylate (3ao)

Starting with 2j (355 mg, 1.0 mmol), 4h (506 mg,

1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

CH₂Cl₂, 3ao was isolated as a red solid (83 mg, 21%);

m. p.: 107 – 109 ^◦C. – ¹H NMR (300 MHz, CDCl₃): δ =

1.97 – 2.06 (m, 2H, CH₂), 2.21, 2.39 (s, 3H, CH₃), 2.89 (t,

³J = 7.6 Hz, 2H, CH₂), 3.61 (t, ³J = 6.6 Hz, 2H, CH₂),

Ethyl 4,6-dimethyl-5-(3⁰,4⁰dioxolophenyl)diazenyl-salicylate

(3aq)

3.97 (s, 3H, OCH₃), 7.66, 7.75 (d, ³J = 8.9 Hz, 2H, CH_Ar),

Starting with 2l (320 mg, 1.0 mmol), 4b (412 mg,

0

11.51 ppm (s, 1H, OH). – ¹³C NMR (63 MHz, CDCl₃): 1.5 mmol) and TiCl₄(0.12 mL, 1.1 mmol) in 3 mL of

δ = 15.3, 17.5 (CH₃), 23.7, 31.8, 45.1 (CH₂), 52.3 (OCH₃), CH₂Cl₂, 3aq was isolated as a red solid (82 mg, 24%); m. p.:

111.1 (C-3), 124.0, 125.6, 126.8 (C_ArCH₃), 131.1 (C-1), 116 – 117 ^◦C. – ¹H NMR (300 MHz, CDCl₃): δ = 1.42 (t,

132.4 (CH_Ar), 135.8 (C-1 ), 146.3 (C-5), 151.2 (C-4 ), 160.0 ³J = 7.2 Hz, 3H, OCH₂CH₃), 2.26 (s, 3H, CH₃), 2.56 (s,

0

(COH), 172.5 ppm (C=O). – IR (ATR, cm⁻¹): ν = 2957 3H, CH₃), 4.44 (q, ³J = 7.0 Hz, 2H, OCH₂), 6.06 (s, 2H,

˜

(w), 2928 (w), 2870 (w), 1899 (w), 1738 (w), 1715 (w), CH₂), 6.75 (s, 1H, H-5), 6.94 (d, ³J = 8.3 Hz, 1H, H-2⁰), 7.35

1651 (s), 1594 (m), 1558 (m), 1489 (w), 1435 (s), 1392 (d, ³J = 1.7 Hz, 1H, H-5⁰), 7.53 (dd, ³J = 6.2 Hz, 1H, H-

(m), 1356 (s), 1310 (m), 1295 (m), 1268 (m), 1247 (m), 6⁰), 11.23 ppm (s, 1H, OH). – ¹³C NMR (63 MHz, CDCl₃):

1228 (w), 1211 (s), 1173 (m), 1143 (m), 1090 (m), 1064 δ = 14.2 (OCH₂CH₃), 17.4, 20.4 (CH₃),61.7 (OCH₂), 98.3

0

(m), 1028 (m), 1006 (m). – MS (EI, 70 eV): m/z (%) = (CH_Ar), 101.9 (CH₂), 107.9 (CH_Ar), 111.6 (C-3), 118.2,

442 (15) [M; ⁸¹Br, ³⁷Cl]⁺, 440 (60) [M; ⁸¹Br, ³⁵Cl]⁺, 123.3 (CH_Ar), 136.2, 137.3 (C_ArCH₃), 145.3 (C-1⁰), 148.6

0

438 (45) [M; ⁷⁹Br, ³⁷Cl]⁺, 408 (30), 07 (22), 406 (24), (C-1), 148.8 (C-3⁰), 150.2 (C-4⁰), 161.5 (COH), 171.6 ppm

405 (21), 404 (44), 403 (24), 402 (56), 387 (26), 373 (C=O). – IR (ATR, cm⁻¹): ν = 2993 (w), 2970 (w), 2928

˜

(42), 371 (46), 327 (32), 323 (26), 257 (23), 255 (75), (w), 2901 (w), 1650 (s), 1598 (m), 1565 (m), 1538 (w), 1506

239 (22), 235 (36), 223 (32), 219 (100), 204 (50), 191 (w), 1481 (w), 1469 (s), 1435 (m), 1417 (m), 1399 (m), 1371

(23), 187 (23), 173 (48), 171 (51), 92 (29), 91 (33), 65 (s), 1346 (s), 1308 (s), 1239 (s), 1220 (m), 1164 (m), 1128

(28), 43 (28). – HRMS (EI): m/z = 440.031848 (calcd. (w), 1110 (w), 1077 (m), 1030 (m), 1014 (m). – UV/Vis

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J. Hefner et al. · Functionalized Diaryldiazenes

943

(CH₂Cl₂, nm): λ_max(logε) = 245, 354, 446. – HRMS ((+)- Crystal structure determinations [41]

ESI): m/z = 343.12871 (calcd. 343.12885 for C₁₈H₁₉N₂O₅,

Suitable single crystals were cooled to 173(2) K (3a, 3d,

3i) or 298(2) K (3an, 3q, 3am, 3ar) for the measurements.

The data were collected on a Bruker-Nonius Apex-X8 CCD

diffractometer using graphite-monochromatized MoK_αradi-

ation (λ = 0.71073 Å). The structures were solved by Di-

rect Methods (SHELXS-97) [42 – 44] and reﬁned by full-

matrix least squares procedures (SHELXL-97, SHELXL-

2013) [42 – 44]. Semi-empirical absorption corrections were

applied (SADABS) [45]. All non hydrogen atoms were re-

ﬁned anisotropically (exception: 3a: The atoms of the mi-

nor part of the disordered azo-benzene group were reﬁned

isotropically). Hydrogen atoms bound to carbon atoms were

included in the reﬁnement at calculated positions using a rid-

ing model, while hydrogen atoms bound to oxygen atoms

were reﬁned freely (exceptions: 3a: The hydrogen atom of

the hydroxyl group (H1) was included in the reﬁnement at

a calculated position using a riding model, but the torsion

angle of the OH group was allowed to reﬁne; 3q: The hydro-

gen atom of the hydroxyl group O3b–H3b was included in

the reﬁnement at a calculated position using a riding model,

but the torsion angle of the OH group was allowed to reﬁne).

Torsion angles of all methyl groups were allowed to reﬁne

(exception: 3q: The torsion angles of all methyl groups were

reﬁned in idealized staggered geometry).

[M+H]⁺).

Synthesis of methyl 5,7-dimethyl-6-phenyldiazenyl-

chroman-8-carboxylate (3ar)

Compound 3h (1.0 equiv.) was dissolved in DMF (15 mL

per mmol), and TBAI (2.0 equiv.) and NaH (60% disper-

sion in mineral oil, 2.3 equiv.) were added under argon at-

mosphere. After stirring for 20 h, ethyl acetate (5 mL) and

ice-cold water (5 mL) were added, and the mixture was neu-

tralized by hydrochloric acid (10%). The mixture was ex-

tracted with ethyl acetate (3 × 20 mL), and the combined

organic layers were dried (Na₂SO₄) and ﬁltered, and the

ﬁltrate was concentrated in vacuo. The residue was puri-

ﬁed by chromatography (heptane-EtOAc = 10 : 1 → 3 :

1). Starting with 3h (0.100 g, 0.28 mmol), TBAI (0.222 g,

0.42 mmol) and NaH (60%, 0.017 g, 0.416 mmol) in DMF

(4.0 mL), 3ar was isolated as a red solid (0.068 g, 76%;

m. p. 124 – 125 ^◦C. – R_f= 0.17 (n-heptane-EtOAc = 3 : 1).

–

¹H NMR (300 MHz, CDCl₃): δ = 2.04 – 2.11 (m, 2H,

OCH₂CH₂), 2.24 (s, 3H, CH₃), 2.25 (s, 3H, CH₃), 2.71 (t,

³J = 6.6 Hz, 2H, (C_ArCH₂), 3.92 (s, 3H, OCH₃), 4.18 – 4.21

(t, 2H, OCH₂), 7.50 (m, 3H, (N=NAr), 7.85 – 7.88 ppm (m,

2H, N=NAr). – ¹³C NMR (75.5 MHz, CDCl₃): δ = 14.2,

15.9 (CH₃), 22.0, 22.6 (CH₂), 52.2 (OCH₃), 66.3 (OCH₂),

119.9 (C_Ar), 122.4 (CH_Ar), 122.5, 126.5 (C_Ar), 129.0, 130.8

(CH_Ar), 133.0 (C_ArCH₃), 145.1, 151.6 (C_ArN=N), 152.7

Cytotoxic experiments

The experiments were carried out following the procedure

previously reported [46].

(C_ArO), 168.9 ppm (COOCH₃). – IR (ATR, cm⁻¹): ν = 3061

˜

(w), 2935 (w), 1728 (s), 1568 (m), 1436 (m), 1275 (s), 1117

(m), 690 (s). – MS (GC, 70 eV): m/z (%) = 324 (100) [M]⁺,

309 (32), 293 (20), 219 (97), 191 (24), 77 (35).– HRMS

(EI): m/z = 324.14641 (calcd. 324.14684 for C₁₉H₂₀N₂O₃,

Acknowledgement

Financial support by the State of Mecklenburg-Vorpom-

[M]⁺). – Anal. for C₁₉H₂₀N₂O₃(324.37): calcd. C 70.35, H mern and by the Deutsche Forschungsgemeinschaft is grate-

6.21, N 8.64; found C 69.95, H 6.31, N 8.52.

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Article Doi

Synthesis of functionalized diaryldiazenes by formal [3+3] cyclizations of 1,3-bis(silyloxy)-1,3-butadienes with 2-aryldiazenyl-3-silyloxy-2-en-1-ones

DOI: 10.5560/ZNB.2014-3198

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