Synthesis of macrocyclic molecular rods as potential electronic devices

FULL PAPER

DOI: 10.1002/ejoc.200600336

Synthesis of Macrocyclic Molecular Rods as Potential Electronic Devices

Alfred Błaszczyk,^[a,b]Martin Chadim,^[a]Carsten von Hänisch,^[a]and Marcel Mayor*^[a,c]

Keywords: Macrocycles / Acetylene scaffolding / Molecular electronic / Sonogashira coupling

The design and synthesis of the macrocycles 1 and 2 as

model compounds for the investigation of negative differen-

tial conductance phenomena in molecular junctions are re-

ported. The macrocycles 1 and 2 comprise a molecular rod

subunit consisting of three ethynyl-linked phenyl rings.

While the rotational freedom along the rod axis of both ter-

minal phenyl rings is limited by the macrocyclic frame, the

central phenyl ring is revolving. The rod substructure is ter-

minally functionalized with acetyl-protected thiol groups to

enable its immobilization between gold contacts. The central

phenyl ring is functionalized with one and two nitro groups

for 1 and 2, respectively. The nitro groups are of particular

importance as i) both macrocycles are model compounds to

investigate a hypothetical intramolecular interaction of the

nitro group with the opposite macrocyclic subunits and ii) the

nitro group(s) result in limited thermal stability of the com-

pounds due to the intramolecular rearrangement to macro-

cycles comprising isatogen subunits. These highly function-

alized macrocycles have been assembled by acetylene scaf-

folding strategies in combination with functional group

transformation chemistry.

Germany, 2006)

electronic transparency of separated π systems^[13]and of

rods immobilized in the meta position.^[14]Recently, even a

single molecule diode has been realized.^[15]Correlations be-

tween molecular structures and electronic signature have

also been reported with other experimental setups like e.g.

mercury droplet^[7b]and crossed-wire junctions.^[7d]While

comparisons of molecular structures within the same setup

often displayed the expected correlations, comparison even

of the same structures between different experiments turned

out to be more troublesome, pointing at the importance of

both, the molecular structure and the close environment

(molecular and electronic).

In the field of molecular electronics, special attention has

been attracted by an NDR device consisting of a laterally

limited self-assembled monolayer (SAM) between two elec-

trodes (Figure 1, A).^[16]Systematic variation of the molecu-

lar structure of the SAM forming phenylethynyl-based mo-

lecular rods indicated that the nitro group at the central

unit is crucial to observe the NDR switching.^[17]While the

electronic property of the device enables the assembly of

more complex electronic functions,^[18]the origin of the ef-

fect is still debated and the topic of numerous theoretical

investigations. Many models assumes a change in the tor-

sion angles between adjacent phenyl rings of the phenyl-

ethynyl backbone in the SAM as the origin of the conduc-

tance changes.^[19]

Introduction

Integration of small assemblies and even single molecules

in electronic circuits has become experimentally feasible in

the last few years.^[1,2]Driven by the vision that molecules

as tailor-made nanoscale objects may serve as modular

functional units in future electronic devices, these funda-

mental investigations have attracted large interest.^[1–4]While

the vision that electronic functions may be engineered by

synthetic chemistry was already described by Hans Kuhn in

the sixties,^[5]the latest rebirth of the concept now called

“molecular electronics” is mainly due to the increasing con-

trol over nanoscale objects with the development of power-

ful manipulation and investigation tools.^[1–3,6]

Monomolecular films have been investigated as sandwich

structures between electrodes,^[7]and smaller assemblies

down to single molecules have been integrated by scanning

probe techniques.^[8]More symmetric electrode pairs for the

investigation of single molecules have been achieved by me-

chanically controlled break junctions (MCB),^[9,10]electro-

migration^[11]and lithographic techniques.^[12]Our systematic

variation of the structure of the investigated molecular rod

in a MCB enabled fundamental experiments displaying the

reflection of the molecules symmetry^[10]and the reduced

[a] Institute for Nanotechnology, Forschungszentrum Karlsruhe

GmbH,

From the point of view of molecular design, a particular

interesting explanation has been reported by Stokbro and

co-workers.^[20]On the basis of density functional theory

(DFT) calculations, they suggest an intermolecular interac-

tion between a nitro group and a phenyl ring of a neigh-

boring molecule in the SAM as the origin of the switching

Postfach 3640, 76021 Karlsruhe, Germany

E-mail: marcel.mayor@int.fzk.de

[b] Faculty of Commodity Science,

Al. Niepodleglos´ci 10, 60-967 Poznan´, Poland

[c] Department of Chemistry, University of Basel,

St. Johanns-Ring 19, 4056 Basel, Switzerland

E-mail: marcel.mayor@unibas.ch

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Figure 1. A) Schematic representation of the NDR device consisting of a laterally limited self-assembled monolayer of an oligophenylene-

ethynyl rod between two gold electrodes. The intermolecular interaction between the nitro group and the phenyl ring of the neighboring

molecule may play a key role in the observed electronic behavior. B) Schematic representation of a single-molecule experiment with the

macrocycle 1Ј immobilized between two gold electrodes. The macrocyclic structure of 1Ј enables the intramolecular proximity of the nitro

group and the phenyl subunit.

behavior. An intermolecular origin of the NDR is further

supported by the fact that such effects have not been ob-

served in single-molecule experiments on similar structures

even at low temperatures.^[21]

An appealing approach to integrate an NDR effect in a

single molecule would be to combine the nitro-group-func-

tionalized molecular rod and the neighboring phenyl ring

in a macrocyclic structure (Figure 1, B). Thereby the inter-

molecular interaction predicted in the SAM device becomes

intramolecular in a single-molecule experiment.

Numerous macrocycles have been assembled in the last

few years based on acetylene scaffolding strategies.^[22]In

particular, because of their unique properties like monodis-

persity and shape persistence, they are very interesting

building blocks in materials chemistry, as host structures^[23]

and as tailor-made nanoscale objects^[22e]for physical experi-

ments.^[24]While numerous macrocycles with high degrees of

structural symmetry have been synthesized on the basis of

modular strategies with repetitive reaction sequences, the

synthetic efforts presented here are rather inspired by the

step-by-step assembly strategies reported by the groups of

Moore^[25]and Haley.^[26]

Figure 2. The macrocyclic structures 1 and 2 comprising a revolv-

ing central unit C harnessed between both terminal units A which

is planarized by the handle B. The central unit C is functionalized

with nitro groups to enable intramolecular interactions with the

phenyl rings of B.

Here we present the design, synthesis and characteriza-

tion of a macrocycle intended for single-molecule investi-

gations between two gold electrodes.

The linear molecular rod substructure consists of three

ethynyl-linked phenyl rings A and C. Both terminal phenyl

rings A are additionally functionalized with acetyl-pro-

tected sulfur groups in the para position with respect to the

linear molecular rod. These acetyl-protected sulfur groups

are known to be ideally suited for the immobilization of the

Molecular Design and Synthetic Strategy

The targeted macrocycles 1 and 2 are displayed in Fig- macrocycle between both gold electrodes of a MCB.^[10,13–15]

ure 2. In the following, the design of the macrocyclic struc- Furthermore, the para positions of these anchor groups

ture of 1 is discussed in detail. However, the same argu- guarantee an intense coupling of the molecular rod sub-

ments are valid for macrocycle 2, which has an additional structure with the electronic levels of the electrodes,^[14]an

nitro group relative to 1. Generally, macrocycle 1 consists important requirement for an intense electronic signal upon

of five ethynyl-linked phenyl rings. It can be divided into conformational rearrangement of the molecular rod. Both

three structural units to which we will refer to as A, B and terminal phenyl rings are further functionalized with the

C, as indicated in Figure 2. These units comprise both ter- bridging handle B. This substructure consists of ethynyl-

minal phenyl rings A, the handle-like bridging substructure linked phenyl units; however, the handle is linked to the

B and the central phenyl ring of the molecular rod C.

terminal phenyl rings at the electronically weakly coupled

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Synthesis of macrocyclic molecular rods as potential electronic devices

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meta position to the sulfur anchor groups. Also the handle rotational position of C and hence the electronic trans-

substructure itself consists solely of the poorly conjugated parency through the rod substructure.

meta-diethynyl benzene unit. Hence, in an immobilized

The concept to harness a phenyl ring by acetylenes in a

macrocycle, the current is expected to be dominated by the macrocycle as an intramolecular revolving subunit has al-

strongly conjugated molecular rod substructure while only ready been realized in the turnstile structures of Moore and

minor contributions should arise from “leaking currents” co-workers.^[27]Recently, a comparable turnstile motif pro-

through the handle. The task of the handle is twofold. First, vided allosteric binding properties to a macrocyclic host

it locks the rotation of the terminal phenyl rings in a planar structure.^[28]

conformation. Second, the handle substructure enables the

The synthetic strategies that have been considered for the

phenyl ring to be in proximity of the nitro group of the assembly of the macrocyclic structures 1 and 2 are displayed

central phenyl unit of the molecular rod.The linear molecu- in Figure 3. In similarity to the design of the macrocycles 1

lar rod substructure consists of the central phenyl ring C, and 2, their structures have been divided into retrosynthetic

which is connected on opposite sites by ethynyl linkers to target structures A, B and C. The assembly of these targets

the terminal phenyl units A. Both ethynyl linkers in the para to the final macrocyclic structure is based on metal-cata-

position of the central phenyl ring C provide this central lyzed cross-coupling reactions. In particular, the Pd⁰- and

ring the freedom to rotate along the rod’s axis. Further- Cu^I-catalyzed substitution of leaving groups at the aromatic

more, the central phenyl ring C is functionalized with one building blocks by acetylenes, which originates from Sono-

and two nitro groups in the case of 1 and 2, respectively. gashira and co-workers^[29]and has been extended to tri-

The electronic transparency through such phenylethynyl flates as leaving groups,^[30]has been applied.

rods has been calculated to depend strongly on the torsion

The choice of the target structure A as the unit that has

angles between neighboring phenyl units.^[19,20]However, in the leaving groups and of B and C as the acetylene-bearing

1 both terminal phenyl rings A are locked by the handle B. units is to some extent coincidental. However, it is mainly

Hence the transport determining torsion angles are given driven by the straightforward accessibility of the acetylene-

by the relative rotational position of C with respect to the functionalized target structures B and C. To increase the

plane of the terminal phenyl rings A. Furthermore, the range of applicable conditions in these coupling reactions,

proximity of the nitro group of C and the phenyl ring of B the terminal sulfur groups have initially been masked by

should enable to profit from the proposed voltage-depend- stable tert-butyl groups, which are known to be transform-

ent interaction between these two subunits that alters the able to acetyl protecting groups under rather mild condi-

Figure 3. Retrosynthetic strategies to assemble the macrocycles 1 and 2 from the building blocks A, B and C. While not all indicated

retrosynthetic options have been investigated to the same extend, the grey retrosynthetic arrows ab, c and d indicate the here successfully

followed synthetic path to the macrocyclic structure.

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tions.^[31,32]To distinguish between both leaving groups of Synthesis and Characterization

the terminal target structure A, we have masked one of

both with a functional group that enabled its transforma-

Depending on the synthetic approach to the macrocycles,

tion into a leaving group after having substituted the first differently functionalized building blocks A are required. In

leaving group.

the assembly strategy ABC, first two building blocks A are

In the further text the different assembly strategies are linked to a building block B. Therefore a building block A

nominated according to the order of assembled subunits A, with an active leaving group in meta position and a masked

B and C. In particular to the approach displayed on the left leaving group in para position of the tert-butyl sulfanyl

side of Figure 3 will be referred to as assembly strategy function is required. In the assembly strategy ACB, two

ABC and to the approach displayed on the right side will building blocks A are connected to both ends of the central

be referred to as assembly strategy ACB.

unit C. For such an approach a building block A with an

The chemistry was mainly developed during the synthesis active leaving group in para position and a silent (masked)

of macrocycle 1, while the macrocycle 2 has been assembled leaving group in meta position is required.

in analogy to 1.

For the assembly strategy ABC, 5-(tert-butylsulfanyl)-2-

With suitable building blocks A, B and C in hand, we nitrophenyl trifluoromethanesulfonate (7, see Scheme 1) is

first focused on forming 1 in two subsequent coupling reac- ideally functionalized as building block A. The tert-butyl-

tions. While the assembly of suitable functionalized sub- sulfanyl group is a masked thiophenol as the tert-butyl

units A and B to D turned out to be feasible in good yields group can be transferred to an acetyl protecting group quite

(ab), the prior assembly of A and C to F was only achieved easily. Furthermore, the tert-butylsulfanyl group allows for

in very moderate yields of 14% (ac). We therefore further rather strong nucleophilic (basic) reaction conditions. The

investigated the assembly strategy ABC displayed on the nitro group is in place of the second leaving group. In subse-

left side of Figure 3. However, to harness both terminal quent reaction steps it can be reduced to an amino group

subunits of D with C in one step turned out to be trouble- and subsequently substituted by e.g. halogens in a Sand-

some (cd). The desired cycle structure was probably formed meyer reaction. Furthermore, the nitro group facilitates the

as the expected signal is observed in the MALDI-ToF mass aromatic nucleophilic substitution reactions in its para and

spectrum of the reaction mixture. However, its formation ortho positions. The triflate group of 7 allows already the

was accompanied by many side products such that we were coupling reaction with acetylenes. The synthesis of 7 is dis-

not able to isolate the macrocyclic structure. In addition, played in Scheme 1.

the yield of the cyclization reaction must be quite low to

Starting with commercially available 5-fluoro-2-nitrophe-

enable the formation of the numerous side products. An nol (3), the phenolic OH was first protected with a methyl-

alternative approach is to mask one acetylene of C with a methoxy (MOM) group by adding bromomethyl methyl

silyl protecting group and to cyclize the macrocycle in two ether to a solution of 3 in tetrahydrofurane (THF) over po-

subsequent coupling steps. As indicated in Figure 3 by grey tassium carbonate (K₂CO₃) at 0 °C. The MOM-protected

retrosynthetic arrows, this strategy turned out to be success- derivative 4 was isolated in 78% yield after column

ful. The coupling product E of D and C (c) has been iso- chromatography (CC) as yellow oil. The nitro group in para

lated in its acetylene-protected form and also as free acetyl- position makes the substitution of the fluorine atom of 4

ene.

much easier. Treatment of 4 with the sodium salt of tert-

Even though elegant strategies involving the coupling of butyl thioalcohol in dry dimethylformamide (DMF) at

a monoprotected diacetylene followed by deprotection and room temperature (room temp.) afforded the tert-butylsul-

subsequent coupling of the second acetylene have been re- fanyl-functionalized derivative 5 in 76% yield after CC. The

ported by Haley and co-workers,^[33,34]we preferred to iso- strong activation of the para and ortho position by the nitro

late and characterize these intermediates after the trouble- group is further confirmed by the substitution of the

some one-step synthesis (cd) described above. Finally, an MOM-protected phenol group by the tert-butylthiolate nu-

intramolecular cyclization reaction (d) of deprotected E led cleophile as main side reaction. The 2,4-bis(tert-butylsul-

to the macrocyclic structures.

fanyl)nitrobenzene was isolated in 10% yield from the reac-

Subsequent protection-group chemistry allowed the con- tion mixture. Deprotection of the MOM group of 5 with

version of the tert-butyl groups at the sulfur into the desired hydrochloric acid in methanol gave the phenol 6 in 95% as

acetyl-protected thiol functions.^[31,32]

yellow liquid. Treatment of 6 in dichloromethane (CH₂Cl₂)

Scheme 1. Synthesis of 7 as potential building block A for the synthetic strategy displayed in Figure 3 on the left side. a) BrCH₂OCH₃,

K₂CO₃, THF, 0 °C to room temp., 78%; b) tBuSNa, DMF, room temp., 1 h, 76%; c) HCl, MeOH, 60 °C, 1 h, 95%; d) Tf₂O, Et₃N,

CH₂Cl₂, 0 °C, 1 h, 89 %.

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Scheme 2. Synthesis of 13 as potential building block A for the synthetic strategy displayed in Figure 3 on the right side. a) 1. HCl,

NaNO₂, H₂O, 0 °C, 1.5 h, 2. KI, H₂O, 0 °C to room temp., overnight, 83%; b) 1. KOH, H₂O, 0 °C, 30 min, 2. ClCSNEt₂, THF, 0 °C to

room temp., overnight, 84%; c) 190 °C, 4 h, 86%; d) Sn, CH₃COOH, EtOH, 60 °C, 3 h, 91%; e) 1. BF₃·Et₂O, tBuONO, THF, –20 °C

to –5 °C, 2 h, 2. pyrrolidine, Na₂CO₃, H₂O, CH₃CN, 0 °C to room temp., 2 h, 49%.

and triethylamine (Et₃N) with trifluoromethanesulfonic an- reactions. Most reaction steps have been described in the

hydride (Tf₂O) at 0 °C gave the desired building block 7 in literature with to a large extent comparable structures.^[38]

89% after CC as yellow solid.

The synthesis of 17 is displayed in Scheme 3.

The assembly strategy ACB requires a protected thio-

phenol as building block A with a leaving group in the para

position and a masked leaving group in the meta position.

S-[4-Iodo-3-(pyrrolidin-1-yldiazenyl)phenyl] diethylthiocar-

bamate (13) ideally fulfils these requirements. Its thiophenol

function is protected as diethylthiocarbamate, which is

stable in basic conditions usually applied in acetylene coup-

ling reactions. Its iodo group in para position to the pro-

tected thiophenol allows for efficient Sonogashira coupling

reactions. Finally, the dialkyltriaza group is a stable precur-

sor of a second iodine as future leaving group in a subse-

quent coupling step.

Scheme 3. Synthesis of the diacetylene 17 as handle substructure

B. a) HCCSi(CH₃)₃, PdCl₂(PPh₃)₂, CuI, DBU, THF, H₂O, room

temp., 16 h, 81%; b) HCCSi(CH₃)₃, PdCl₂(PPh₃)₂, CuI, Et₃N,

PPh₃, THF, reflux, 4 h, 97%; c) K₂CO₃, MeOH, CH₂Cl₂, room

temp., 98%.

The assembly of 13 is displayed in Scheme 2. Starting

with commercial 4-amino-3-nitrophenol the amino function

was substituted by iodine in a Sandmayer reaction se-

Commercially available 1-bromo-3-iodobenzene (14) and

quence.^[35]The amino group was diazotized using HCl/ trimethylsilyl(TMS)acetylene yielded 3,3Ј-dibromotolane

NaNO₂and the diazotate subsequently iodinated with KI (15), following a literature procedure.^[38]Subsequently, both

to afford 4-iodo-3-nitrophenol (9) in 83% yield as red- bromines of 15 have been substituted with TMS acetylenes

orange crystalline solid. To introduce the protected thi- using Sonogashira coupling conditions. The doubly TMS-

ophenol function, the phenol group of 9 was first protected protected diacetylene 16 has been isolated in 97% yield af-

as O-(4-iodo-3-nitrophenyl) diethylthiocarbamate (10), ter CC as a white solid. Both TMS protecting groups have

which was converted into S-(4-iodo-3-nitrophenyl) diethyl- been removed almost quantitatively by treatment with po-

thiocarbamate (11) in a Newman–Kwart rearrangement.^[36]tassium carbonate in a mixture of methanol and dichloro-

Treatment of the potassium salt of 9 with N,N-diethylthi- methane. Diacetylene 17 was isolated as a white solid in

ocarbamoyl chloride in THF at 0 °C gave 10 in 84% yield 98% yield.

after crystallization as yellow crystals. Subsequent heating

In addition, the diacetylenes 20 and 28 are required as

of 10 to 190 °C gave the ester 11 in 86% yield as a yellow building blocks C in both synthetic strategies displayed in

crystalline solid after CC and recrystallization from etha- Figure 3. As both macrocycles 1 and 2 differ in their central

nol. Particular caution is needed for the rearrangement re- building block C, these diacetylene subunits had to be syn-

action. The reaction temperature has to be controlled care- thesized separately. Furthermore, for a stepwise closing of

fully as explosive decomposition of 10 has been observed the macrocycle, this building block is required in its mono-

applying too high temperatures. Reduction of the nitro protected form. While the subunit C of the macrocycle 1 was

group of 11 with tin in acetic acid and ethanol gave the deliberately synthesized as free diacetylene 20 and as mono-

corresponding aniline 12 in 91% yield after crystallization protected diacetylene 23, the subunit C of the macrocycle 2

from ethanol. The amino function of 12 was transformed was synthesized in its monoprotected form 27. However,

into a dialkyltriaza group by diazotising using BF₃·Et₂O/ the free acetylene 28 has been isolated as side product. Two

tBuONO conditions followed by treatment with pyrroli- different synthetic strategies have been applied for both

dine^[37]in acetonitrile at 0 °C to afford 13 in 49% yield as monoprotected diacetylenes 23 and 27. While for the syn-

a pink crystalline solid.

thesis of the monoprotected unit C, 23, of the macrocycle

Both synthetic strategies in Figure 3 require diacetylene 1 two acetylenes with different protecting groups have been

17 as the handle-like substructure B. Its assembly is straight introduced, the higher symmetry of the C unit of macro-

forward and is based on well-developed acetylene coupling cycle 2 enables for a monodeprotection strategy for the

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Scheme 4. Synthesis of the free diacetylenes 20 and 28 and their monoprotected derivatives 23 and 27 as central subunits C of the

macrocycles 1 and 2 respectively. a) HCCSi(CH₃)₃, PdCl₂(PPh₃)₂, CuI, Et₃N, THF, 61%; b) K₂CO₃, MeOH, CH₂Cl₂, room temp., 58%;

c) HCCSi(CH₃)₃, PdCl₂(PPh₃)₂, CuI, HNiPr₂, THF, room temp., 2 h, 53%; d) HCCSi[CH(CH₃)₂]₃, PdCl₂(PPh₃)₂, CuI, HNiPr₂, THF,

room temp., 16 h, 63%; e) K₂CO₃, MeOH, CH₂Cl₂, room temp., 96%; f) HNO₃, H₂SO₄, 95 °C, 17%; g) HCCSi(CH₃)₃, Pd(PPh₃)₄, CuI,

EtNiPr₂, THF, room temp., 16 h, 63%; h) KF, AcOH, MeOH, CH₂Cl₂, room temp., 33%.

monoprotected unit C, 27. The syntheses of the different statistical deprotection of 26, traces of acetic acid were

subunits C are displayed in Scheme 4.

added to a MeOH/CH₂Cl₂mixture prior to 0.5 equiv. po-

Starting with commercially available 1,4-dibromo-2- tassium fluoride. The acetic acid slows down the deprotec-

nitrobenzene, the TMS-protected diacetylene 19 was ob- tion kinetics probably by providing protons for the proton-

tained in moderate yields of 61% following a literature pro- ation of the formed acetylide. The mono-TMS-protected di-

cedure.^[39]The subsequent removal of both TMS protecting acetylene 27 was isolated in 33% yield by CC as whitish

groups of 19 using K₂CO₃in a MeOH/CH₂Cl₂mixture gave solid. Besides unreacted starting material, also the fully de-

1,4-diethynyl-2-nitrobenzene (20) in 58% again following protected diacetylene 28 was isolated in 43% yield as ex-

the procedure described in ref.^[39]

In analogy to the diacetylene 20, also the monoprotected

.

pected side product of the statistical deprotection reaction.

While for the assembly strategy ABC both acetylenes of

diacetylene 23 was assembled starting with 1,4-dibromo-2- the diacetylene 17 were further functionalized with a poten-

nitrobenzene (19). First, the bromine in the ortho position tial building block A, for the assembly strategy ACB both

to the nitro group was substituted with TMS-acetylene acetylenes of 20 were further functionalized. Both reaction

using palladium- and copper-catalyzed Sonogashira reac- steps are displayed in Scheme 5.

tion conditions. The TMS-protected acetylene 21 was iso-

Using palladium- and copper-catalyzed Sonogashira re-

lated in 53% yield after CC. Again Sonogashira reaction action conditions in THF and triethylamine (Et₃N) as base

conditions have been applied to substitute the remaining at room temp., the diacetylene 17 and the triflate 7 gave the

bromine of 21 with a tris(isopropylsilyl) (TIPS) acetylene. desired oligoethynylphenylene 29 in an excellent yield of

Diacetylene 22 comprising two different protecting groups 88% after CC. Even though the iodo group is known as

has been isolated in 63% yield after CC. Chemoselective powerful leaving group in Sonogashira coupling reac-

deprotection of the TMS group with K₂CO₃in a MeOH/ tions,^[29]the coupling of diacetylene 20 with iodophenyl 13

CH₂Cl₂mixture afforded the monoprotected target struc- turned out to be less efficient. The best result of this coup-

ture 23 as white solid in 96% yield.

ling reaction was achieved with similar reaction conditions

According to a literature procedure,^[40]nitration of 1,4- as applied for 17 and 7. However, the functionalized molec-

dibromobenzene (24) gave the desired 1,4-dibromo-2,3-dini- ular rod 30 was isolated as yellow oil in only 14% yield

trobenzene (25) in poor yields of 17%. The major product after CC.

of the nitration reaction is the mono-nitrated 1,4-dibromo-

The attractivity of the assembly strategy ACB decreased

2-nitrobenzene (18), which was isolated in 60% yield. Both considerably as all attempts to improve the yield of 30

bromines of 25 were substituted by TMS acetylenes to af- failed. We therefore focused our synthetic endeavour on the

ford the diprotected diacetylene 26 in 63% yield. For the more promising assembly strategy ABC.

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Scheme 5. First assembly steps of the strategy ABC (top) and of the strategy ACB (bottom). While the synthesis of 29 represents the

assembly of two units A with the subunit B, the synthesis of 30 represents the merging of two units A with a subunit C. a) PdCl₂-

(PPh₃)₂, CuI, Et₃N, THF, room temp., 4 h, 88%; b) PdCl₂(PPh₃)₂, CuI, Et₃N, THF, room temp., 16 h, 14%.

To introduce the central subunit C, both nitro groups of for the active Pd⁰species triphenylphosphane was added,

29 have to be transformed to leaving groups suitable for together with CuI as cocatalyst and diisopropylethylamine

acetylene coupling reactions. We intended to reduce the ni- as base. The course of the macrocyclization reaction was

tro groups to amines which can be converted to halide leav- monitored by thin layer chromatography and MALDI-

ing groups in a Sandmeyer reaction.

TOF-MS. Within a few hours numerous new compounds

Treatment of the dinitro compound 29 in THF with con- with very comparable polarities were formed. Investigation

centrated hydrochloric acid (HCl) and tin afforded the di- of the crude reaction mixture by MALDI-TOF-MS dis-

amine 31 as white solid in 95% yield after CC. Diazotizing played among numerous other signals also the one expected

of 31 in dry THF with BF₃·Et₂O/tBuONO gave the diazo- for the desired product (m/z 722) and the one of the open

nium salt as a yellow precipitate from cold THF/hexane.^[41]iodo precursor (m/z 849). However, the large number of side

Treatment of the precipitate with potassium iodide and iod- products with comparable polarities considerably reduced

ine in a mixture of acetonitrile (CH₃CN), and water (H₂O) the attractivity of the one-pot macrocyclization reaction as

afforded the desired diiodo compound 32 together with the route to the desired precursor 36.

monoiodinated derivative. Compound 32 was isolated in

38% yield as white solid by recrystallization from ethyl ace- stepwise by using the monoprotected diacetylene subunits

tate (Scheme 6). 23 and 27. However, the challenge of such a subsequent

Alternatively, the macrocycle 36 may also be assembled

Compound 32 comprises two terminal subunits A linked two-step ring-closing strategy is to minimize the substitu-

by the subunit B. Furthermore, both iodines are excellent tion of both iodines of 32 by the acetylene. To favor the

leaving groups to introduce the subunit C with a Sonoga- formation of the monosubstituted product over the disub-

shira coupling protocol.

stituted one, pseudo-high dilution conditions have been ap-

The reaction of 32 with the free diacetylene subunits C, plied.

20 or 28, may afford the desired macrocyclic precursors 36

An excess of 2 equiv. of the diiodo derivative 32 in a de-

or 39 in a one-pot cyclization reaction. Indeed, for 36 as gassed THF/(iPr)₂NEt mixture have been charged with

precursor of the macrocycle 1 this macrocyclization step has Pd(PPh₃)₄and CuI as catalysts. The acetylene 23 has been

been investigated to some extend. However, the control of added dropwise over a period of 10 h at room temp. After

the reaction of both bifunctional subunits 32 and 20 turned completed addition, the reaction mixture was kept at room

out to be troublesome.

temp. for another 16 h. From the crude reaction mixture

For the one-pot macrocyclization reaction between 32 the desired monosubstituted derivative 33 has been isolated

and 20 high-dilution conditions in THF using Pd(dba)₂· in 64% yield as yellow solid by CC, while the doubly substi-

CHCl₃as source of Pd⁰have been investigated. As ligand tuted compound 34 has been isolated in 30% yield. For the

Scheme 6. Transformation of both nitro groups of 29 into iodines of 32 via amines of 31. a) Sn/HCl, THF, room temp., 1 h, 95%; b) 1)

BF₃·Et₂O, tBuONO, THF, 2) KI/I₂in H₂O, CH₃CN/CH₂Cl₂, 38%.

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1

synthesis of the dinitro derivative 37, toluene has been used

The structures of 36 and 39 are both confirmed by H

as solvent instead of THF. Furthermore, the excess of 32 and ¹³C NMR spectroscopy and mass spectrometry

was reduced to 1.5 equiv.. Otherwise comparable reaction (MALDI-TOF-MS). In particular, the disappearance of the

conditions afforded 37 in only 23% yield after column singlets of the acetylene protons (δ = 3.27 ppm for 35 and

chromatography. The doubly acetylene-substituted side δ = 3.57 ppm for 38) documented successful cyclizations.

1

product was not isolated from the numerous by-products of Furthermore, a substantial reduction of signals in the H

the reaction mixture.

and ¹³C NMR spectra of 39 compared to the precursor 38

Deprotection of the TIPS-protected acetylene 33 with pointed to its increased symmetry. The MALDI-TOF mass

tetrabutylammonium fluoride (TBAF) in THF with traces spectra of 36 and 39 displayed with m/z 721.66 and

of acetic acid afforded the free acetylene 35 in 93% yield m/z 766.51 exclusively the signals expected for both [M⁺]

after CC. The TMS-protected acetylene of the dinitro deriv- ions. While the target compound 36 and its synthetic pre-

ative 37 was deprotected with potassium fluoride (KF) in a cursors are further characterized by elemental analysis, this

MeOH/CH₂Cl₂mixture to afford the acetylene 38 in 98% additional purity information was not available for 39 and

yield after CC. Usually potassium carbonate is used instead its intermediates due to the small-scale synthesis of the dini-

of KF for the deprotection of TMS-protected acetylenes. tro target structure 39.

However, these conditions applied to 37 results in the sub-

In addition, the side product 34 with two silyl-protected

stitution of one of both hydrogen atoms in the aromatic acetylenes is an ideal precursor for an extended macrocyclic

ring system activated with two nitro groups by methoxide structure. In an oxidative coupling both acetylenes may

nucleophiles and are therefore not suitable for the deprotec- close the macrocycle with an additional acetylenic C₂unit

tion of the dinitro derivative 37.

compared to the macrocycles 36 and 39.

The key step of the synthesis is an intramolecular ring-

Therefore, both silyl-functionalized acetylenes of 34 have

closing Sonogashira reaction as macrocyclization of the been deprotected with TBAF in THF to afford the diacetyl-

precursors 35 and 38. High-dilution (10^–4) reaction condi- ene 40 in 88% yield after CC. A 4×10^–5 solution of the

tions have been applied to favor the intramolecular reaction diacetylene 40 in acetonitrile was treated with 1 equiv. of

over intermolecular ones. The courses of the cyclization re- copper(II) acetate at 80 °C for 6 h. To dissolve 40 in aceto-

actions were monitored by MALDI-TOF-MS analysis. The nitrile, a minor amount of CH₂Cl₂was used, which proba-

most successful macrocyclization has been obtained with a bly evaporated during the course of the reaction. The

2.4·10^–4 solution of 35 in dry and degassed toluene. Diiso- macrocycle 41 was isolated in 36% yield after CC. Again

1

propylethylamine [(iPr)₂NEt] was added as base, followed the formation of 41 is confirmed by its H- and ¹³C NMR

by tetrakis(triphenylphosphane)palladium(0) [Pd(PPh₃)₄] spectra. In particular the disappearance of the acetylene

and copper(I) iodide (CuI) as catalysts. The reaction mix- proton singlet at δ = 3.29 ppm pointed to the successful

ture was stirred for 20 h at room temp. The desired macro- diacetylene formation. Furthermore, only a signal at

cycle 36 was isolated by CC in a fair yield of 30% as yellow m/z 890.49, which corresponds to [M⁺] of 41 is observed in

solid. The macrocyclization turned out to be very sensitive the MALDI-TOF mass spectra and corroborates the

to the reaction solvent. The use of THF instead of toluene, macrocyclic structure.

but otherwise similar reaction conditions as those described

All three macrocyclic structures 36, 39 and 41 are func-

above, reduced the yield of the targeted macrocycle 37 to tionalized with two terminal sulfur atoms which are pro-

17%. The ring-closing reaction to the dinitro macrocycle 39 tected with tert-butyl groups. To immobilize these rods on

was even more troublesome. A 3.8·10^–4 solution of the metal surfaces these sulfur groups have to be deprotected.

precursor 38 in dry and degassed toluene charged with However, these terminal thiophenol substructures tend to

(iPr)₂NEt, Pd(PPh₃)₄and CuI was stirred at room temp. for the formation of disulfides in the presence of oxygen, yield-

6 h. Only 11% of the desired macrocycle 39 were isolated ing in insoluble polymers of these bifunctional molecular

by CC as yellow solid. However, numerous side reactions rods. Ideally suited to store these compounds as monomer

during Sonogashira reactions with nitro-group-containing and for the in-situ deprotection followed by subsequent im-

aromatic units have been reported. In particular, the prox- mobilization on metal surfaces are acetyl protecting groups.

imity of the acetylene in ortho position of the nitro group The last step of the synthesis is hence the transprotection

is known to tend to the formation of a bicyclic nitrogen of S-tert-butyl groups into S-acetyl groups.^[31,32]

radical heterostructure called isatogen.^[42]According to the

First attempts were based on a protocol that we have

literature, successful coupling protocols for these nitro- developed ourselves.^[31]However, treatment of the macro-

group-containing compounds are characterized by lower cycle 36 in acetyl chloride with traces of bromine did not

temperatures, shorter reaction times and low concentrations result in the desired macrocycle 1 with acetyl-protected ter-

of base to reduce side reactions.^[43]In particular, com- minal sulfur groups. Most likely the poor solubility of 36

pounds with two nitro groups in the aromatic ring are in acetyl chloride prevents the desired transprotection reac-

reported to be very sensitive to any base.^[44]The consi- tion. Fortunately, a variation of the protocol reported from

derably lower yield of the ring-closing reaction for the Stuhr–Hansen^[32]was more successful. Compound 36 was

macrocycle 39 comprising two nitro groups each with an dissolved in CH₂Cl₂with toluene as cosolvent, the later is

acetylene in ortho position compared with 36 is therefore reported to be crucial for the successful transprotection re-

not surprising.

action. Treatment with acetyl chloride and boron tribro-

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Synthesis of macrocyclic molecular rods as potential electronic devices

FULL PAPER

mide (BBr₃) afforded the desired acetyl-protected macro- estingly, the enlarged macrocycle 41 is considerably more

cycle 1 as yellow solid in 49% yield after CC. A similar soluble than 36 and 39. The increased solubility is probably

protocol applied to the dinitro precursor 39 gave the acetyl- due to a less planar structure of the macrocycle compared

protected dinitro macrocycle 2 in 53% yield after CC. Inter- to 36 and 39. The additional ethynyl unit in 41 results in

Scheme 7. Macrocyclization reactions. a) Pd(dba)₂·CHCl₃, PPh₃, CuI, (iPr)₂NEt, THF; b) Pd(PPh₃)₄, CuI, (iPr)₂NEt, THF, room temp.,

24 h, (33–64%, 34–30%); c) Pd(PPh₃)₄, CuI, (iPr)₂NEt, toluene, room temp., 24 h, 23%; d) TBAF, AcOH, THF, room temp., 93%; e)

KF, MeOH/CH₂Cl₂, room temp., 98%; f) Pd(PPh₃)₄, CuI, toluene, (iPr)₂NEt, room temp., (36–30%, 39–11%); g) BBr₃, AcCl, CH₂Cl₂/

toluene, room temp., (1 49%, 2 53%); h) TBAF, AcOH, THF, room temp., 88%; i) Cu(OAc)₂, CH₃CN/CH₂Cl₂, 80 °C, 6 h, 36%; j) Br₂,

AcCl/AcOH/CH₂Cl₂, 37%.

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A. Błaszczyk, M. Chadim, C. v. Hänisch, M. Mayor

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an increased ring tension, which does no longer allow a ever, there was some hope that the increase of ring tension

planar arrangement of the macrocycle and thus, formation upon formation of the isatogen substructure might provide

of poorly soluble stacks is less favorable for the uneven these macrocyclic isatogen precursors with superior stability

macrocycle 41 (Scheme 7).

features. Generally, the macrocycle 36 displayed rather deli-

As consequence of the increased solubility of 41, the bro- cate stability features in solution. Most crystallization sam-

mine-catalyzed transprotection protocol^[31]was applied suc- ples of 36 in various solvents turned orange within several

cessfully. Treatment of 41 in CH₂Cl₂/AcCl/AcOH with bro- weeks. TLC investigations of the crystallization samples

mine gave the enlarged macrocycle 42 with terminal acetyl- monitored the formation of the isatogen 43 in solution at

protected sulfur groups in 37% yield after CC.

room temperature.

X-ray structures of the macrocycles are of particular

interest as they provide further insight into structural fea-

tures in general, but also into the interaction between the

central revolving unit C and the handle subunit B. There-

fore considerable endeavours were focused on the crystalli-

zation of the target structures 1 and 2. However, the very

poor solubility of the acetyl-protected macrocycles 1 and

2 did not allow for the growth of single crystals of these

compounds. We therefore focused our crystallization in-

vestigations on the slightly more soluble macrocycles 36

and 39. To increase the solubility of 36, a small sample in

toluene was gently heated with the heatgun. Upon heating,

a color change from yellow to orange was observed. The

orange decomposition product displayed an increased solu-

bility more suitable for the growth of single crystals. To fur-

ther investigate the origin of this temperature-induced color

change we expanded the crystallization investigations on

these “decomposed” macrocycles as well. A solution of the

Scheme 8. Formation of the macrocycle comprising an isatogen

subunit 43. a) toluene, reflux.

The fact that the already poor yields of the macrocycliza-

“decomposed” orange macrocycle in CH₂Cl₂overlaid with tion reactions of nitro group containing precursors 35 and

methanol yielded in single crystals suitable for X-ray analy- 38 was further reduced by increasing reaction temperature

sis. Figure 4 displays the X-ray structure of the orange de- is easily rationalized considering the efficient formation of

composition product.

macrocyclic isatogen derivatives.

As displayed in Scheme 8, an intramolecular rearrange-

ment reaction between the nitro group and the acetylene P1 with half a CH₂Cl₂molecule per formula unit.

The macrocycle 43 crystallizes in the triclinic space group

[45]

¯

This

unit in proximity yields in the heterobicyclic isatogen deriv- solvent molecule is disordered around the inversion center.

ative 43. The formation of isatogens and thus the delicate The C–C bond length of the acetylene groups are on

thermal stability features of ortho ethynyl- and nitro-func- average 119.7 pm, the acetylene bridge angles range be-

tionalized benzene structures have been reported.^[42]How- tween 174.4(3)° [C(47)–C(48)–C(9)] and 179.0(3)° [C(19)–

Figure 4. X-ray structure of the macrocyclic isatogen derivative 43. Selected bond lengths [pm] and bond angles [°]: S(1)–C(1) 186.4(3),

S(1)–C(5) 177.7(3), S(2)–C(24) 177.6(3), S(2)–C(27) 185.7(3), O(1)–N(1) 127.2(3), O(2)–C(12) 121.8(3), N(1)–C(11) 132.8(4), N(1)–C(14)

146.3(3), C(8)–C(11) 146.2(4), C(11)–C(12) 149.8(3), C(12)–C(13) 149.0(4), C(19)–C(20) 119.9(4), C(31)–C(32) 119.4(4), C(39)–C(40)

119.3(4), C(47)–C(48) 120.3(4); C(1)–S(1)–C(5) 102.76(2), C(24)–S(2)–C(27) 103.61(3).

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FULL PAPER

zene (4) as a yellowish liquid (78% yield, 27.457 g). ¹H NMR

(300 MHz, CDCl₃, 25 °C): δ = 3.56 (s, 3 H, CH₃), 5.31 (s, 2 H,

OCH₂), 6.79 (ddd, J_F,H= 9.0 Hz, J_H,H= 7.2 Hz, J_H,H= 2.5 Hz,

C(20)–C(21)], which essentially shows a linear arrangement.

The intramolecular sulfur–sulfur distance was determined

to 1.85(3) nm.

3

4

3

4

1 H), 7.06 (dd, J_F,H= 10.1 Hz, J_H,H= 2.6 Hz, 1 H), 7.91 (dd,

3

⁴J_F,H= 9.0 Hz, J_H,H= 6.0 Hz, 1 H) ppm. ¹³C NMR (75 MHz,

2

CDCl₃, 25 °C): δ = 57.0 (CH₃), 95.9 (OCH₂), 105.3 (d, J_F,C

27.0 Hz), 108.9 (d, J_F,C= 23.8 Hz), 127.7 (d, J_F,C= 11.3 Hz),

152.8 (d, J_F,C= 11.5 Hz), 165.5 (d, J_F,C= 255.8 Hz) ppm.

C₈H₈FNO₂(201.15): calcd. C 47.77, H 4.01, N 6.96; found C 47.69,

H 3.93, N 6.91. MS (EI): m/z (%) = = 201.1 (30) [M⁺], 170.0 (100)

[M⁺–OCH₃], 140.1 (50) [M⁺–C₂H₅O₂].

=

Conclusions

2

3

1

The synthesis of several macrocycles consisting of eth-

ynyl-linked phenyl units based on acetylene scaffolding stra-

tegies is described. These macrocycles have been designed

as model compounds to investigate the nature of switching

mechanisms on a single-molecule level. They are function-

alized by either tert-butyl- or acetyl-protected sulfanyl

groups and with one or two nitro groups. These nitro

groups were not only troublesome during the synthesis;

they considerably reduce the stability features of the final

macrocycles. Degradation of the ortho-nitro phenylethynyl

substructure by intramolecular rearrangement to the het-

erocyclic isatogen substructure has been observed either

upon heating or upon keeping these macrocycles for several

weeks in solution. With respect to the intended investiga-

tion of switching properties of these structures, their ten-

dency for intramolecular rearrangement reactions has to be

considered also as potential origin of alterations in elec-

tronic transparency along the structure.

4-(tert-Butylsulfanyl)-2-(methoxymethoxy)-1-nitrobenzene (5): To a

solution of 4 (14.0 g, 0.07 mol) in dry DMF (50 mL) was added

tBuSNa (1.1 equiv., 8.587 g) in several portions. The reaction mix-

tuire was stirred for 1 h at room temperature. The reaction mixture

was poured into satd. solution of NaCl and the organic products

were extracted with Et₂O. After removal of the solvents in vacuo,

flash chromatography on silica gel (hexane/EtOAc, 9:1) afforded 5

as a yellowish liquid (14.435 g, 76%). ¹H NMR (300 MHz, CDCl₃,

25 °C): δ = 1.34 (s, 9 H, CH₃), 3.51 (s, 3 H, CH₃), 5.31 (s, 2 H,

3

4

OCH₂), 7.21 (dd, J_H,H= 8.4 Hz, J_H,H= 1.8 Hz, 1 H), 7.48 (d,

⁴J_H,H= 1.6 Hz, 1 H), 7.75 (d, ³J_H,H= 8.4 Hz, 1 H) ppm. ¹³C NMR

(75 MHz, CDCl₃, 25 °C): δ = 31.2 (CH₃), 47.6 (SC), 56.8 (OCH₃),

95.4 (OCH₂), 124.9, 125.0, 129.3, 140.3, 141.0, 149.8 ppm.

C₁₂H₁₇NO₄S (271.33): calcd. C 53.12, H 6.32, N 5.16; found C

53.01, H 6.19, N 4.99. MS (EI): m/z (%) = 271.0 (25) [M⁺], 215.0

(40) [M⁺–C₄H₈], 57.2 (100) [C₄H₉⁺].

While the transport characteristics of these macrocycles

are currently investigated in electronic circuits, we are ap-

plying the concept of a revolving turnstile as subunit of a

macrocycle for molecular switches based on redox-switch-

able intramolecular interactions and for molecules compris-

ing well-defined and tuneable spectroscopic transport char-

acteristics.

5-(tert-Butylsulfanyl)-2-nitrophenol (6): The MOM-protected phe-

nol 5 (14.031 g, 0.0517 mol) was dissolved in methanol (200 mL)

and concentrated HCl (15 mL) was added. After heating for 1 h

to 60 °C, the reaction mixture was poured into cold water. After

extraction with Et₂O the combined organic phases were dried with

MgSO₄. Flash chromatography (silica gel, hexane/EtOAc, 9:1) af-

1

forded 6 as a yellow liquid (11.1654 g, 95%). H NMR (300 MHz,

3

CDCl₃, 25 °C): δ = 1.40 (s, 9 H, CH₃), 7.05 (dd, J_H,H= 8.7 Hz,

4

3

⁴J_H,H= 1.9 Hz, 1 H), 7.29 (d, J_H,H= 1.8 Hz, 1 H), 8.01 (d, J_H,H

= 8.9 Hz, 1 H), 10.65 (s, 1 H, OH) ppm. ¹³C NMR (75 MHz,

CDCl₃, 25 °C): δ = 31.3 (CH₃), 48.1 (SC), 124.7, 125.1, 126.5,

132.8, 147.0, 154.5 ppm. C₁₀H₁₃NO₃S (227.28): calcd. C 52.85, H

5.77, N 6.16; found C 52.45, H 5.71, N 6.07. MS (EI): m/z (%) =

227.1 (15) [M⁺], 171.0 (20) [M⁺–C₄H₈], 57.2 (100) [C₄H₉⁺].

Experimental Section

General Remarks: All chemicals for synthesis were purchased and

used without further purification. Toluene and THF have been

dried by distillation over sodium/benzophenone. Dry DMF and

dry CH₃CN have been used as delivered from Aldrich. CH₂Cl₂

has been dried by distillation over CaH₂. Characterizations were

performed with the following instruments: ¹H NMR and ¹³C NMR

spectra were recorded with a Bruker Ultra Shield 300 MHz or

500 MHz, the J values are given in Hz. MALDI-TOF spectra was

performed with a PerSeptive Biosystems Voyager –DE PRO time-

of-flight mass spectrometer and EI-MS on a LKB-9000S. Melting

points were measured with a Büchi Melting Point B-540 apparatus.

TLC was carried out on Merck silica gel 60 F₂₅₄plates and column

chromatography (CC) using Merck silica gel 60 (0.040–0.063 mm).

Elemental analyses were performed using the ThermoQuest

FlashEA 1112 N/Protein Analyzer.

5-(tert-Butylsulfanyl)-2-nitrophenyl Trifluoromethanesulfonate (7):

To a solution of the phenol 6 (16.0 g, 70.4 mmol) in dry CH₂Cl₂,

was added Et₃N (2 equiv., 140.8 mmol, 19.5 mL), and the reaction

mixture was cooled to 0 °C. After the dropwise addition of trifluor-

omethanesulfonic anhydride (1.1 equiv., 13 mL), the reaction was

stirred for 1 h at 0 °C. The reaction mixture was concentrated and

filtered through a silica plug. Flash chromatography on silica gel

(hexane/Et₂O, 9:1) afforded 7 as a yellow solid (22.5148 g, 89%).

1

M.p. 38–40 °C. H NMR (300 MHz, CDCl₃, 25 °C): δ = 1.39 (s, 9

4

3

H, CH₃), 7.56 (d, J_H,H= 1.7 Hz, 1 H), 7.66 (dd, J_H,H= 8.5 Hz,

⁴J_H,H= 1.8 Hz, 1 H), 8.12 (d, ³J_H,H= 8.5 Hz, 1 H) ppm. ¹³C NMR

(75 MHz, CDCl₃, 25 °C): δ = 31.1 (CH₃), 48.8 (SC), 118.7 (q, ¹J_F,C

4-Fluoro-2-(methoxymethoxy)-1-nitrobenzene (4): To a mixture of 5-

=

320 Hz), 126.4, 130.55, 130.57, 135.8, 140.9, 144.5 ppm.

C₁₁H₁₂F₃NO₅S₂(359.34): calcd. C 36.77, H 3.37, N 3.90; found C

37.06, H 3.02, N 4.03. MS (EI): m/z (%) = 359.1 (5) [M⁺], 57.2

(100) [C₄H₉⁺].

fluoro-2-nitrophenol (27.499 g, 0.175 mol) and potassium carbon-

ate (48.38 g, 0.35 mol) in dry THF (250 mL) was added dropwise

bromomethyl methyl ether (43.3 mL, 0.525 mol) at 0 °C. Then it

was stirred overnight (18 h) at room temperature. The reaction mix-

ture was poured into water and extracted with CH₂Cl₂. The com-

bined organic fractions were washed with sodium hydroxide to re-

move remaining starting material. After removing of the solvents

the residue was purified by flash chromatography on silica gel (hex-

ane/EtOAc, 9:1) to afford 4-fluoro-2-methoxymethoxy-1-nitroben-

4-Iodo-3-nitrophenol (9):^[35]A solution of NaNO₂(187 g, 2.71 mol)

in H₂O (280 mL) was added dropwise to a mechanically stirred

suspension of 4-amino-3-nitrophenol (8) (209 g, 1.36 mol) in con-

centrated HCl (500 mL) and H₂O (85 mL) over 1 h at 0 °C . Sub-

sequently, a solution of KI (450 g, 2.71 mol) in H₂O (350 mL) was

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A. Błaszczyk, M. Chadim, C. v. Hänisch, M. Mayor

FULL PAPER

4

added dropwise over 1.5 h at 0 °C. The speed at which both rea-

gents were added was chosen such that stirring was maintained in

spite of precipitation. After stirring the reaction mixture overnight

at room temperature, the precipitate was collected by filtration,

washed with water and dried under vacuum. CC of the crude prod-

uct (SiO₂, hexane/Et₂O, 4:1) afforded 9 as red-orange crystalline

solid (299 g, 83%). M.p. 155–156 °C. ¹H NMR (300 MHz, CDCl₃,

= 2.1 Hz, 1 H, 6-H), 6.94 (d, J_H,H= 2.1 Hz, 1 H, 2-H), 7.63 (d,

³J_H,H= 8.1 Hz, 1 H, 5-H) ppm. ¹³C NMR (75 MHz, CDCl₃,

25 °C): δ = 13.2, 13.8 (br. s, CH₃), 42.5, 85.6 (CH₂), 121.5, 126.6,

129.8, 139.2, 147.3, 165.4 (C=O) ppm. C₁₁H₁₅IN₂OS (350.22):

calcd. C 37.72, H 4.32, N 8.00; found C 37.85, H 4.17, N 7.95.

MS (MALDI-TOF): found m/z 350.7293, 349.9944 calculated for

C₁₁H₁₅IN₂OS.

3

4

25 °C): δ = 5.34 (br. s, 1 H, OH), 6.82 (dd, J_H,H= 8.5 Hz, J_H,H

= 3 Hz, 1 H, 6-H), 7.40 (d, J_H,H= 3.0 Hz, 1 H, 2-H), 7.85 (d,

S-[4-Iodo-3-(pyrrolidin-1-ylazo)phenyl] Diethylthiocarbamate (13):

A solution of 12 (187 g, 0.534 mol) in dry THF (600 mL) was

added over 30 min to a stirred solution of BF₃·Et₂O (268 mL,

2.13 mol) in THF under argon at –20 °C. Subsequently, a solution

of tBuONO (240 mL, 1.86 mol) in dry THF (600 mL) was added

over 45 min. The reaction mixture was warmed to –5 °C, during

another 40 min the diazonium salt precipitated. The precipitation

was completed by pouring the reaction mixture into cold EtOH

(2 L). The precipitation was collected on a fritted disc funnel,

washed with cold Et₂O (2×500 mL) and dissolved in CH₃CN

(500 mL). Pyrrolidine (132 mL, 1.60 mol) and an aqueous solution

of Na₂CO₃(170 g, 1.60 mol) were slowly added at 0 °C, and the

mixture was stirred for 2 h at room temperature. The crude product

was precipitated by pouring the reaction mixture into H₂O (2 L).

The precipitate was collected by filtration and washed with water.

A first portion was isolated by crystallization from EtOH. Evapo-

ration of the mother liquid and subsequent CC (SiO₂, hexane/Et₂O,

1:1) afforded another portion. Combination of both portions gave

the ester 13 as a pink crystalline solid (113 g, 49%). M.p. 106.5–

4

³J_H,H= 8.5 Hz, 1 H, 5-H), ppm. ¹³C NMR (75 MHz, CD₃CN,

25 °C): δ = 73.4, 113.4, 122.3, 143.0, 154.9 (br. s), 158.8 ppm.

C₆H₄INO₃(265.01): calcd. C 27.19, H 1.52, N 5.29; found C 27.43,

H 1.56, N 5.24. MS (EI): m/z (%) = 264.9 (100) [M⁺], 218.9 (26)

[M⁺–NO₂].

O-(4-Iodo-3-nitrophenyl) Diethylthiocarbamate (10): A solution of

KOH (51.1 g, 0.911 mol) in H₂O (155 mL) was added dropwise to

a stirred solution of 4-iodo-3-nitrophenol (9) (221 g, 0.834 mol) in

THF (1500 mL) over 25 min at 0 °C. Subsequently, a solution of

N,N-diethylthiocarbamoyl chloride (152 g, 1 mol) in THF (400 mL)

was added dropwise over 15 min at 0 °C. The reaction mixture was

stirred at room temperature for 16 h. The solid precipitate was re-

moved by filtration. The water phase of the filtrate was extracted

by CH₂Cl₂(2×250 mL) and combined with the organic phase of

the filtrate. Removing of the solvents resulted in an oil. Crystali-

zation from ethanol afforded 10 as yellow crystals (265 g, 84%).

M.p. 75.5–76.5 °C. ¹H NMR (300 MHz, CDCl₃, 25 °C): δ = 8.02

1

3

4

107 °C. H NMR (300 MHz, CDCl₃, 25 °C): δ = 1.21 (br. s, 6 H,

(d, J_H,H= 8.7 Hz, 1 H, 5-H), 7.65 (d, J_H,H= 2.7 Hz, 1 H, 2-H),

3

4

3

CH₃), 2.02 (br. s, 4 H, CH₂-β-N₃), 3.41 (q, J_H,H= 7.2 Hz, 4 H,

7.05 (dd, J_H,H= 8.7 Hz, J_H,H= 2.7 Hz, 1 H, 6-H), 3.87 (q, J_H,H

3

CH₂), 3.72 (br. s, 2 H, CH₂–N₃), 3.92 (br. s, 2 H, CH₂–N₃), 6.97

= 7.2 Hz, 2 H, CH₂), 3.68 (q, J_H,H= 7.2 Hz, 2 H, CH₂), 1.32 (t,

3

4

³J_H,H= 7.2 Hz, 3 H, CH₃), 1.31 (t, ³J_H,H= 7.2 Hz, 3 H, CH₃) ppm.

¹³C NMR (75 MHz, CDCl₃, 25 °C): δ = 11.7, 14.0 (CH₃), 44.7,

48.8 (CH₂), 82.4, 121.0, 128.9, 142.1, 152.8, 154.0, 185.2 ppm.

C₁₁H₁₃IN₂O₃S (380.20): calcd. C 34.75, H 3.45, N 7.37; found; C

34.73, H 3.19, N 7.27. MS (MALDI-TOF): found m/z 380.5582,

379.9686 calculated for C₁₁H₁₃IN₂O₃S.

(dd, J_H,H= 8.4 Hz, J_H,H= 2.1 Hz, 1 H, 6-H), 7.49 (d, J_H,H

=

2.1 Hz, 1 H, 2-H), 7.83 (d, J_H,H= 8.4 Hz, 1 H, 5-H) ppm. ¹³C

NMR (75 MHz, CDCl₃, 25 °C): δ = 13.2, 13.8 (br. s, CH₃), 23.6,

24.1 (br. s, CH₂-β-N₃), 42.4 (CH₂–N), 47.3 (CH₂–N₃), 51.1, 97.9,

124.3, 129.6, 133.3, 139.3, 150.8, 165.3 (C=O) ppm. C₁₅H₂₁IN₄OS

(432.32): calcd. C 41.67, H 4.90, N 12.96; found; C 41.94, H 4.94,

N 13.14. MS (MALDI-TOF): calcd. for C₁₅H₂₁IN₄OS 432.0475;

found 432.6874.

3

S-(4-Iodo-3-nitrophenyl) Diethylthiocarbamate (11): Ester 10 (235 g,

0.618 mol) was melted and heated at 190 °C for 4 h under argon.

(CAUTION: Upon heating to temperatures higher than 190 °C, the

melt decomposes with violent explosion!) After cooling to room

temperature, the crude product was purified by CC (SiO₂, CH₂Cl₂).

Crystallization from EtOH afforded 11 as yellow crystals (201 g,

3,3Ј-Dibromotolane (15): Compound 15 was synthesized according

to a literature procedure.^[38]Yield 81% (white solid). M.p. 105–

107 °C (ref.^[38]102 °C). ¹H NMR (300 MHz, CDCl₃, 25 °C): δ =

3

4

7.23 (t, J_H,H= 8.0 Hz, 2 H), 7.42–7.52 (m, 4 H), 7.68 (t, J_H,H

=

1.6 Hz, 2 H) ppm. ¹³C NMR (75 MHz, CDCl₃, 25 °C): δ = 89.2

(CϵC), 122.4, 124.9, 130.0, 130.3, 131.9, 134.5 ppm. MS (EI):

m/z (%) = 336.0 (100) [M⁺], 176.0 (75) [M⁺–2 Br].

1

86%). M.p. 81–81.5 °C. H NMR (300 MHz, CDCl₃, 25 °C): δ =

3

1.17 (br. s, 3 H, CH₃), 1.28 (br. s, 3 H, CH₃), 3.42 (q, J_H,H

=

3

4

7.2 Hz, 4 H, CH₂), 7.37 (dd, J_H,H= 8.1 Hz, J_H,H= 2.1 Hz, 1 H,

4

3

6-H), 8.00 (d, J_H,H= 2.1 Hz, 1 H, 2-H), 8.02 (d, J_H,H= 8.1 Hz,

1 H, 5-H) ppm. ¹³C NMR (75 MHz, CDCl₃, 25 °C): δ = 13.2, 14.0

(CH₃), 42.8, 87.3 (CH₂), 131.7, 131.9, 140.1, 142.1, 152.8, 163.3

(C=O) ppm. C₁₁H₁₃IN₂O₃S (380.20): calcd. C 34.75, H 3.45, N

7.37; found C 34.75, H 3.07, N 7.04. MS (MALDI-TOF): found

m/z 380.5272, 379.9686 calculated for C₁₁H₁₃IN₂O₃S.

3,3Ј-Bis(trimethylsilylethynyl)tolane (16): The dibromotolane 15

(8.70 g, 26.0 mmol) was dissolved in degassed dry THF (250 mL).

Subsequently trimethylsilylacetylene (3.5 equiv., 91.0 mmol,

12.8 mL), Pd(PPh₃)₂Cl₂(0.9124 g, 1.3 mmol), CuI (0.4951 g,

2.6 mmol) and Et₃N (40 mL) were added under nitrogen. After re-

fluxing for 4 h, all solvents were removed, the residue dissolved in

CH₂Cl₂and absorbed on silica gel. CC (silica gel, hexane) gave

16 as a white solid (9.3473 g, 97%). M.p. 112–113 °C. ¹H NMR

S-(3-Amino-4-iodophenyl) Diethylthiocarbamate (12): Tin powder

(205 g, 1.73 mol) was slowly added in portions to a solution of 11

(219 g, 0.576 mol) in EtOH (900 mL) and AcOH (260 mL,

4.55 mol) at 60 °C. The reaction mixture was refluxed for 3 h and

subsequently filtered through sea sand. The filtrate was evaporated

and the crude was distributed between 10% KOH (2 L) and CHCl₃.

The aqueous layer was extracted by CHCl₃(3×2 L) and the com-

bined organic layers dried with MgSO₄. Evaporation of the sol-

vents and crystallization from EtOH afforded 12 as beige crystal-

3

(300 MHz, CDCl₃, 25 °C): δ = 0.26 (s, 18 H, CH₃), 7.29 (t, J_H,H

3

= 7.7 Hz, 2 H), 7.43 (t, J_H,H= 7.7 Hz, 4 H), 7.64 (s, 2 H) ppm.

¹³C NMR (75 MHz, CDCl₃, 25 °C): δ = 0.06 (CH₃), 89.2 (CϵC),

95.2 (CϵC), 104.2 (CϵC), 123.4, 123.7, 128.5, 131.6, 131.9,

135.2 ppm. C₂₄H₂₆Si₂(370.63): calcd. C 77.77, H 7.07; found C

77.44, H 7.11. MS (MALDI-TOF): calcd. for C₂₄H₂₆Si₂370.1568;

found 370.0192.

line solid (183 g, 91%). M.p. 109.5–110 °C. ¹H NMR (300 MHz, 3,3Ј-Bis(ethynyl)tolane (17): K₂CO₃(6 equiv., 145.8 mmol, 20.15 g)

CDCl₃, 25 °C): δ = 1.16 (br. s, 3 H, CH₃), 1.25 (br. s, 3 H, CH₃), was added to a solution of 16 (9.01 g, 24.3 mmol) in degassed

3.41 (q, ³J_H,H= 7.2 Hz, 4 H, CH₂), 6.63 (dd, ³J_H,H= 8.1 Hz, ⁴J_H,HCH₂Cl₂/MeOH (200 mL, 1:1). After stirring for 1 h under N₂,

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Eur. J. Org. Chem. 2006, 3809–3825

Synthesis of macrocyclic molecular rods as potential electronic devices

FULL PAPER

water was added. Extraction with CH₂Cl₂and filtration through a

silica plug gave 11 (5.498 g, 98%) as a white solid. M.p. 109–110 °C.

¹H NMR (300 MHz, CDCl₃, 25 °C): δ = 3.11 (s, 2 H, ϵCH), 7.31

7.69, N 4.28; found C 70.02, H 7.91, N 4.40. MS (MALDI-TOF):

calcd. for C₁₉H₂₅NO₂Si 327.1649; found 327.7591.

1,4-Dibromo-2,3-dinitrobenzene (25): Synthesized according to

ref.^[40]. The desired product was separated by CC (silica, ether/hex-

ane, 1:1) to provide 25 as a yellowish solid (17% yield). M.p. 162–

163 °C (ref.^[44]159–160 °C). ¹H NMR (300 MHz, CDCl₃, 25 °C): δ

= 7.75 (s, 2 H) ppm. ¹³C NMR (75 MHz, CDCl₃, 25 °C): δ = 114.5,

137.0, 144.6 ppm. C₆H₂BrN₂O₄(325.90): calcd. C 22.11, H 0.62,

N 8.60; found C 22.13, H 0.63, N 8.84. MS (EI): m/z (%) = 325.8

(100) [M⁺].

3

(t, J_H,H= 7.8 Hz, 2 H), 7.48 (m, 4 H), 7.66 (s, 2 H) ppm. ¹³C

NMR (75 MHz, CDCl₃, 25 °C): δ = 78.0 (CϵC), 82.8 (CϵC), 89.1

(CϵC), 122.7, 123.4, 128.6, 132.0, 132.2, 135.3 ppm. C₁₈H₁₀

(226.27): calcd. C 95.55, H 4.45; found C 95.72, H 4.47. MS (EI):

m/z (%) = 226.1 (100) [M⁺], 224.0 (35) [M⁺–2H].

2-Nitro-1,4-bis(trimethylsilanylethynyl)benzene (19): Synthesized ac-

cording to ref.^[39]. Yield 61%. M.p. 78.5–79.5 °C. ¹H NMR

(300 MHz, CDCl₃, 25 °C): δ = 0.26 (s, 9 H, SiCH₃), 0.27 (s, 9 H,

SiCH₃), 7.56–7.58 (m, 2 H), 8.06–8.08 (m, 1 H) ppm. ¹³C NMR

(75 MHz, CDCl₃, 25 °C): δ = –0.3, –0.2, 99.2, 99.7, 102.0, 105.9,

118.0, 124.3, 127.9, 135.0, 135.6, 150.3 ppm. MS (EI): m/z (%) =

315.1 (28) [M⁺], 300.1 (100) [M⁺–CH₃].

2,3-Dinitro-1,4-bis(trimethylsilanylethynyl)benzene (26): Trimethyl-

silylacetylene (5.38 mL, 0.0381 mol) was added to a solution of 1,4-

dibromo-2,3-dinitrobenzene 25 (4.1422 g, 0.0127 mol), Pd(PPh₃)₄

(0.3669 g, 0.32 mmol), CuI (0.1209 g, 0.64 mmol) and (iPr)₂NEt

(3 mL) in degassed THF (100 mL). After stirring for 18 h at room

temperature, the solvents were removed and the residue was ab-

sorbed on silica gel. Purification by CC (silica, hexane/dichlorome-

than: 2:1) afforded 26 (2.8963 g, 63%) as a whitish solid. M.p. 98–

100 °C. ¹H NMR (300 MHz, CDCl₃, 25 °C): δ = 0.26 (s, 18 H,

CH₃), 7.66 (s, 2 H) ppm. ¹³C NMR (75 MHz, CDCl₃, 25 °C): δ = –

0.5 (CH₃), 95.8 (CϵC), 108.4 (CϵC), 118.4, 135.4 ppm.

C₁₆H₂₀N₂O₄Si₂(360.51): calcd. C 53.31, H 5.59, N 7.77; found C

53.67, H 5.58, N 7.51. MS (EI): m/z (%) = 360.1 (20) [M⁺], 345.1

(100) [M⁺–CH₃].

1,4-Diethynyl-2-nitrobenzene (20): Synthesized according to ref.^[39]

.

Yield 58%. M.p. 123–125 °C. ¹H NMR (300 MHz, CDCl₃, 25 °C):

δ = 3.31 (s, 1 H, ϵCH), 3.61 (s, 1 H, ϵCH), 7.63–7.67 (m, 2 H),

8.13–8.15 (m, 1 H) ppm. ¹³C NMR (75 MHz, CDCl₃, 25 °C): δ =

78.3, 80.8, 81.9, 87.1, 117.6, 123.9, 128.2, 135.6, 136.0, 150.2 ppm.

MS (EI): m/z (%) = 171.0 (100) [M⁺], 125.0 (31) [M⁺–NO₂].

(4-Bromo-2-nitrophenylethynyl)trimethylsilane (21): 1,4-Dibromo-2-

nitrobenzene (18.157 g, 64.6 mmol) was dissolved in dry and de-

gassed THF (250 mL). Pd(PPh₃)₂Cl₂(2.2671 g, 3.2 mmol), CuI

(1.2302 g, 6.46 mmol), iPr₂NH (6 mL) and trimethylsilylacetylene

(6.980 g, 71.0 mmol) were added. After stirring for 2 h at room

temperature under N₂, the solvents were removed and the residue

adsorbed on silica gel. CC (silica gel, hexane/ethyl acetate, 9:1) af-

(4-Ethynyl-2,3-dinitrophenylethynyl)trimethylsilane (27) and 1,4-Di-

ethynyl-2,3-dinitrobenzene (28): A solution of 26 (7.02 g,

0.0195 mol) in degassed CH₂Cl₂/MeOH (500 mL, 1:1) and acetic

acid (0.5 mL) was treated with portions of potassium fluoride

(0.5 equiv., 9.75 mmol, 0.5665 g). After stirring for 30 min at room

temperature, the reaction mixture was extracted with CH₂Cl₂. Puri-

fication by CC (silica, hexane/CH₂Cl₂, 1:1) afforded (4-ethynyl-2,3-

dinitrophenylethynyl)trimethylsilane as a whitish solid (1.8554 g,

33%) and 1,4-diethynyl-2,3-dinitrobenzene as beige solid (1.8192 g,

43%).

1

forded 13 (10.2101 g, 53%) as yellow liquid. H NMR (300 MHz,

3

CDCl₃, 25 °C): δ = 0.27 (s, 9 H, CH₃), 7.51 (d, J_H,H= 8.3 Hz, 1

3

4

H), 7.67 (dd, J_H,H= 8.3 Hz, J_H,H= 2.1 Hz, 1 H), 8.16 (d, J_H,H

= 2.1 Hz, 1 H) ppm. ¹³C NMR (75 MHz, CDCl₃, 25 °C): δ = –0.3

(CH₃), 98.5 (CϵC), 105.5 (CϵC), 117.5, 122.3, 127.7, 135.9, 136.2,

150.5 ppm. C₁₁H₁₂BrNO₂Si (298.21): calcd. C 44.30, H 4.06, N

4.70; found C 44.39, H 3.98, N 4.65. MS (EI): m/z (%) = 297.0 (25)

[M⁺], 282.0 (100) [M⁺–CH₃].

(4-(Ethynyl-2,3-dinitrophenylethynyl)trimethylsilane (27): M.p. 86–

87 °C. ¹H NMR (300 MHz, CDCl₃, 25 °C): δ = 0.25 (s, 9 H, CH₃),

2-Nitro-4-[(triisopropylsilanyl)ethynyl]-1-(trimethylsilanylethynyl)-

benzene (22): Triisopropylsilylacetylene (2.7521 g, 15.0 mmol) was

added to a solution of 21 (3.00 g, 10.0 mmol), Pd(PPh₃)₂Cl₂

(0.3509 g, 0.5 mmol), CuI (0.190 g, 1.0 mmol) and (iPr)₂NH (4 mL)

in degassed THF (150 mL). The reaction mixture was stirred for

16 h at room temperature. The solvents were removed and the resi-

due was absorbed on silica gel and purified by CC (hexane/ethyl

3

3.59 (s, 1 H, ϵCH), 7.67 (d, J_H,H= 8.6 Hz, 1 H), 7.70 (d, J_H,H

= 8.4 Hz, 1 H) ppm. ¹³C NMR (75 MHz, CDCl₃, 25 °C): δ = –06

(CH₃), 75.4 (CϵC), 88.5 (CϵC), 95.5 (CϵC), 108.9 (CϵC), 117.2,

119.1, 135.7, 135.9, 145.1, 145.4 ppm. C₁₃H₁₂N₂O₄Si (288.33):

calcd. C 54.15, H 4.19, N 9.72; found C 54.06, H 4.54, N 9.38. MS

(EI): m/z (%) = 288.0 (20) [M⁺], 273.1 (100) [M⁺–CH₃].

1,4-Diethynyl-2,3-dinitrobenzene (28): M.p. 170–173 °C. ¹H NMR

(300 MHz, CDCl₃, 25 °C): δ = 3.61 (s, 2 H, ϵCH), 7.74 (s, 2 H)

ppm. ¹³C NMR (75 MHz, CDCl₃, 25 °C): δ = 75.3 (CϵC), 88.9

(CϵC), 118.2, 136.1, 144.0 ppm. MS (EI): m/z (%) = 216.0 (100)

[M⁺], 127.0 (96), 99.0 (48), 98 (47), 86 (50).

1

acetate, 9:1) to afford 22 (2.5179 g, 63%) as a brownish liquid. H

NMR (300 MHz, CDCl₃, 25 °C): δ = 0.28 (s, 9 H, CH₃), 1.12 (ap-

parent s, 21 H, CH, CH₃), 7.52–7.62 (m, 2 H), 8.06 (s, 1 H) ppm.

¹³C NMR (75 MHz, CDCl₃, 25 °C): δ = –0.06 (SiCH₃), 11.6

(SiCH₃), 19.0 (CH₃), 96.7 (CϵC), 99.4 (CϵC), 104.2 (CϵC), 106.0

(CϵC), 118.1, 124.8, 128.1, 135.2, 135.9, 150.3 ppm; C₂₂H₃₃NO₂Si₂

(399.67): calcd. C 66.11, H 8.32, N 3.50; found C 66.03, H 8.11, N

3.39. MS (EI): m/z (%) = 399.1 (6) [M⁺], 356.1 (100) [M⁺–C₃H₇].

3,3Ј-Bis[(5ЈЈ-tert-butylsulfanyl-2ЈЈ-nitrophenyl)ethynyl]tolane (29): A

mixture of 17 (6.8 g, 0.03 mol), 7 (27.0 g, 0.075 mol), Pd(PPh₃)₄

(1.7175 g, 1.49 mmol), CuI (0.2856 g, 1.50 mmol) and triethylamine

(4-Ethynyl-3-nitrophenylethynyl)triisopropylsilane (23): K₂CO₃(50 mL) in dry, degassed THF (300 mL) was stirred for 4 h at room

(3 equiv., 0.017 mol, 2.3841 g) was added to a solution of 22 temperature. All solvents were removed and the residue was ad-

(2.30 g, 5.75 mmol) in degassed CH₂Cl₂/MeOH (1:1, 100 mL),. The sorbed on silica gel. CC (silica, CH₂Cl₂/hexane: 1:1) afforded 29 as

reaction mixture was stirred for 30 min at room temperature. Ex-

traction with CH₂Cl₂and filtration through a silica plug afforded

23 (1.8077 g, 96%) as a whitish solid. M.p. 42–43 °C. ¹H NMR

yellow solid (17.0227 g, 88 %). M.p.162–164 °C. ¹H NMR

(300 MHz, CDCl₃, 25 °C): δ = 1.38 (s, 18 H, CH₃), 7.39 (t, 2 H,

³J_H,H= 7.9 Hz), 7.53–7.62 (m, 6 H), 7.79 (s, 2 H), 7.86 (d, 2 H,

3

(300 MHz, CDCl₃, 25 °C): δ = 1.13 (apparent s, 21 H, CH, CH₃), ⁴J_H,H= 1.9 Hz), 8.04 (d, 2 H, J_H,H= 8.6 Hz) ppm. ¹³C NMR

3.61 (s, 1 H, ϵCH), 7.60–7.64 (m, 2 H), 8.11 (s, 1 H) ppm. ¹³C

NMR (75 MHz, CDCl₃, 25 °C): δ = 11.6 (SiCH), 19.0 (CH₃), 78.3

(75 MHz, CDCl₃, 25 °C): δ = 31.3 (CH₃), 47.9 (SC), 85.2 (CϵC),

89.3 (CϵC), 96.7 (CϵC), 118.7, 122.8, 123.6, 124.8, 128.8, 132.1,

(CϵC), 86.6 (CϵC), 96.7 (CϵC), 103.6 (CϵC), 116.7, 125.1, 127.7, 132.6, 135.3, 136.5, 140.6, 142.0, 149.2 ppm. C₃₈H₃₂N₂O₄S₂

135.2, 135.7, 150.4 ppm. C₁₉H₂₅NO₂Si (327.49): calcd. C 69.68, H (644.80): calcd. C 70.78, H 5.00, N 4.34; found C 70.98, H 5.21, N

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A. Błaszczyk, M. Chadim, C. v. Hänisch, M. Mayor

FULL PAPER

4.29. MS (MALDI-TOF): calcd. for C₃₈H₃₂N₂O₄S₂644.1798;

found 644.6097.

3

H), 7.54 (d, J_H,H= 7.9 Hz, 2 H), 7.58 (d, J_H,H= 7.8 Hz, 2 H),

7.68 (d, ⁴J_H,H= 2.1 Hz, 2 H), 7.79 (s, 2 H), 7.83 (d, ³J_H,H= 8.1 Hz,

2 H) ppm. ¹³C NMR (75 MHz, CDCl₃, 25 °C): δ = 31.1 (CH₃),

46.6 (SC), 89.3 (CϵC), 91.9 (CϵC), 92.7 (CϵC), 102.2, 123.3,

123.6, 128.8, 130.1, 131.7, 132.0, 133.3, 134.8, 138.5, 139.0,

140.9 ppm. C₃₈H₃₂I₂S₂(806.60): calcd. C 56.58, H 4.00; found C

56.93, H 4.01. MS (EI): m/z (%) = 806.8 (10) [M⁺], 749.7 (10) [M⁺–

C₄H₉], 694.1 (100) [M⁺–C₈H₁₇].

1,4-Bis{2Ј-[4ЈЈ-(diethylcarbamoylsulfanyl)-2ЈЈ-(pyrrolidin-1ЈЈЈ-ylazo)-

phenyl]ethynyl}-2-nitrobenzene (30): A solution of 1,4-diethynyl-2-

nitrobenzene (20) (0.058 g, 0.268 mmol), 13 (0.232 g, 2 equiv.,

0.536 mmol), Pd(PPh₃)₂Cl₂(9.4 mg, 0.0134 mmol), CuI (5.1 mg,

0.0268 mmol) and Et₃N (0.7 mL) in degassed THF (10 mL) was

stirred for 16 h at room temperature under nitrogen. All solvents

were removed, the residue was dissolved in CH₂Cl₂and absorbed

on silica gel. Purification by CC (silica, toluene/ethyl acetate, 8:2)

afforded 30 as a yellow oil (0.03 g, 14%). ¹H NMR (300 MHz,

CDCl₃, 25 °C): δ = 1.22 (br. s, 12 H, CH₃), 2.06 (br. s, 8 H, CH₂),

3.43 (q, ³J_H,H= 7.2 Hz, 8 H, CH₂), 3.72 (br. s, 4 H, CH₂), 3.92 (br.

3-{[5ЈЈ-tert-Butylsulfanyl-3ЈЈ-(2ЈЈЈ-nitro-4ЈЈЈ-triisopropylsilylethynyl-

phenyl)ethynyl]phenylethynyl}-3Ј-(5ЈЈЈЈ-tert-butylsulfanyl-2ЈЈЈЈ-iodo-

phenylethynyl)tolane (33) and 3,3Ј-Bis{[5ЈЈ-tert-butylsulfanyl-2ЈЈ-

(2ЈЈЈ-nitro-4ЈЈЈ-triisopropylsilylethynylphenyl)ethynyl]phenylethynyl}-

tolane (34): Pd(PPh₃)₄(0.3721 g, 0.322 mmol) and CuI (0.1206 g,

0.633 mmol) were added o a solution of 32 (2 equiv., 6.44 mmol,

5.2094 g) in degassed THF (500 mL), (iPr)₂NEt (4 mL). A solution

of 20 (1.0549 g, 3.22 mmol) in degassed THF (100 mL) was added

dropwise over 10 h at room temperature. The reaction mixture was

stirred for 16 h room temperature. The solvents were removed and

the residue adsorbed on silica gel. Purification by CC (silica, hex-

ane/CH₂Cl₂, 2:1) afforded the monosubstituted desired product 33

(2.0735 g, 64%) and the doubly substituted derivative 34 (1.166 g,

30%).

3

s, 4 H, CH₂), 7.22–7.28 (m, 2 H), 7.51 (d, J_H,H= 7.8 Hz, 1 H),

3

7.57 (d, J_H,H= 8.1 Hz, 1 H), 7.62–7.68 (m, 4 H), 8.18 (br. s, 1 H)

ppm. ¹³C NMR (75 MHz, CDCl₃, 25 °C): δ = 13.2 (br. s, CH₃),

13.8 (br. s, CH₃), 23.8 (br. s, CH₂), 24.2 (br. s, CH₂), 42.5 (CH₃),

47.2 (br. s, CH₂), 51.4 (br. s, CH₂), 90.1, 92.4, 94.8, 98.0, 117.5,

117.6, 118.6, 124.0, 124.5, 127.7, 130.9, 131.2, 131.4, 131.6, 133.0,

133.7, 134.9, 135.1, 147.5, 149.2, 153.0, 153.2, 165.25, 165.29 ppm.

MS (MALDI-TOF): calcd. for C₄₀H₄₅N₉O₄S₂779.3931; found

779.2193.

Compound 33: M.p. 74.5–76.5 °C (yellow solid). ¹H NMR

(300 MHz, CDCl₃, 25 °C): δ = 1.11 (s, 3 H, SiCH), 1.12 (s, 18 H,

CH₃), 1.31 (s, 9 H, CH₃), 1.34 (s, 9 H, CH₃), 7.17 (dd, ³J_H,H= 8.1,

3,3Ј-Bis[(2ЈЈ-amino-5ЈЈ-tert-butylsulfanylphenyl)ethynyl]tolane (31):

To a solution of compound 29 (16.0 g, 0.024 mol) in THF (200 mL)

was added concentrated HCl (10 mL) followed by portions of tin

powder (6 equiv., 0.144 mol, 17.091 g). The reaction mixture was

stirred for 1 h at room temperature. The reaction mixture was

poured into water. After neutralization with a NaOH solution the

organic phase was extracted with CH₂Cl₂. Filtration through a

short column with CH₂Cl₂afforded 31 as a white solid (13.3343 g,

3

⁴J_H,H= 2.2 Hz, 1 H), 7.37 (t, J_H,H= 7.7 Hz, 2 H), 7.48–7.64 (m,

3

7 H), 7.65–7.70 (m, 2 H), 7.75–7.81 (m, 3 H), 7.83 (d, J_H,H

=

8.2 Hz, 1 H), 8.17 (s, 1 H) ppm. ¹³C NMR (75 MHz, CDCl₃,

25 °C): δ = 11.4 (SiCH), 18.8 (CH₃), 31.1 (SCCH₃), 31.2 (SCCH₃),

46.6 (SC), 47.2 (SC), 88.1 (CϵC), 89.29 (CϵC), 89.33 (CϵC), 90.0

(CϵC), 91.9 (CϵC), 92.7 (CϵC), 93.6 (CϵC), 96.8 (CϵC), 97.1

(CϵC), 102.2 (CϵC), 104.1, 118.0, 123.3, 123.4, 123.55, 123.56,

124.7, 124.9, 126.1, 128.2, 128.7, 128.8, 130.1, 131.66, 131.74,

131.9, 132.0, 132.6, 133.29, 133.31, 134.7, 134.8, 135.0, 135.9,

137.1, 138.4, 138.9, 140.5, 140.9, 149.3 ppm. C₅₇H₅₆INO₂S₂Si

(1006.18): calcd. C 68.04, H 5.61, N 1.39; found C 68.22, H 5.77,

N 1.46. MS (MALDI-TOF): calcd. for C₅₇H₅₆INO₂S₂Si 1005.2561;

found 1005.4937.

1

95%). M.p. 208–210 °C. H NMR (300 MHz, CDCl₃, 25 °C): δ =

3

1.27 (s, 18 H, CH₃), 4.42 (br. s, 4 H, NH₂), 6.68 (d, 2 H, J_H,H

=

3

4

8.4 Hz), 7.29 (dd, J_H,H= 8.4 Hz, J_H,H= 2.1 Hz, 2 H), 7.36 (t,

³J_H,H= 7.6 Hz, 2 H), 7.50 (d, J_H,H= 7.9 Hz, 4 H), 7.54 (d, J_H,H

= 2.0 Hz, 2 H), 7.71 (s, 2 H) ppm. ¹³C NMR (75 MHz, CDCl₃,

25 °C): δ = 31.1 (CH₃), 45.9 (SC), 86.3 (CϵC), 89.5 (CϵC), 94.5

(CϵC), 108.1, 114.6, 120.6, 123.8, 123.9, 129.0, 131.68, 131.73,

134.8, 139.8, 141.5, 148.8 ppm. C₃₈H₃₆N₂S₂(584.84): calcd. C

78.04, H 6.20, N 4.79; found C 77.86, H 6.24, N 4.58. MS

(MALDI-TOF): calcd. for C₃₈H₃₆N₂S₂584.2314; found 583.6667.

3

4

Compound 34: M.p. 155–157 °C. ¹H NMR (300 MHz, CDCl₃,

25 °C): δ = 1.11 (s, 6 H, SiCH), 1.12 (s, 36 H, CH₃), 1.34 [s, 18 H,

3

SC(CH₃)], 7.37 (t, J_H,H= 7.8 Hz, 2 H), 7.49–7.64 (m, 10 H), 7.68

3,3Ј-Bis[(5ЈЈ-tert-butylsulfanyl-2ЈЈ-iodophenyl)ethynyl]tolane (32): To

a solution of 32 (13.012 g, 0.022 mol) in dry THF (250 mL) was

added BF₃·Et₂O (14 equiv., 0.31 mol) over 30 min at –20 °C until

the starting compound disappeared (monitored by TLC). tert-

BuONO (4 equiv., 0.088 mol) in THF (20 mL) was added over 15

min. The reaction mixture was warmed to –5 °C over 30 min. After

this time the yellow solid started to precipitate. Cold hexane

(100 mL) was added to effect precipitation of the yellow diazonium

salt. The salt was filtered and washed with cold hexane. The diazo-

nium salt was dissolved in cold acetonitrile (100 mL) and a solution

of KI (6 equiv.) and I₂(3 equiv.) in water/acetonitrile was added.

During this addition a brown solid was precipitated and CH₂Cl₂

(50 mL) was added in order to dissolve it. The reaction mixture

was stirred for 16 h at room temperature. Then it was extracted

with CH₂Cl₂and washed with a solution of Na₂S₂O₃in order to

remove unreacted iodine. The solvent was removed and the residue

was absorbed on silica gel. Purification by CC (silica, hexane/

3

4

(d, J_H,H= 8.1 Hz, 2 H), 7.75 (d, J_H,H= 1.7 Hz, 2 H), 7.77–7.79

(m, 2 H), 8.16 (d, J_H,H= 1.6 Hz, 2 H) ppm. ¹³C NMR (75 MHz,

4

CDCl₃, 25 °C): δ = 11.3, 18.8, 31.2, 47.2, 88.1, 89.3, 90.0, 93.6,

96.8, 97.1, 104.0, 118.0, 123.4, 123.6, 124.7, 124.9, 126.1, 128.2,

128.8, 131.7, 131.9, 132.6, 134.8, 134.98, 134.99, 135.9, 137.1,

140.5, 149.3 ppm. C₇₆H₈₀N₂O₄S₂Si₂(1204.76): calcd. C 75.70, H

6.69, N 2.32; found C 76.02, H 6.71, N 2.46. MS (MALDI-TOF):

calcd. for C₇₆H₈₀N₂O₄S₂Si₂1204.5093; found 1204.2429.

3-{[5ЈЈ-tert-butylsulfanyl-3ЈЈ-(4ЈЈЈ-Ethynyl-2ЈЈЈ-nitrophenyl)-

ethynyl]phenylethynyl}-3Ј-(5ЈЈЈЈ-tert-butylsulfanyl-2ЈЈЈЈ-iodophenyl-

ethynyl)tolane (35): To a solution of 33 (2.80 g, 2.78 mmol) in de-

gassed THF (200 mL) was added glacial acetic acid (3 drops), fol-

lowed by 16 mL of a 1  TBAF/THF solution. After stirring for

30 min at room temperature, the solvents were removed and the

residue adsorbed on silica gel. Purification by CC (silica, hexane/

CH₂Cl₂, 1:1) afforded 35 (2.202 g, 93%) as a yellow solid. M.p.

CH₂Cl₂, 1:1) afforded a mixture of the desired tolane 32 and the 80.0–81.5 °C. ¹H NMR (300 MHz, CDCl₃, 25 °C): δ = 1.31 (s, 9

3

monoiodinated derivative. Recrystallization from ethyl acetate af-

forded 32 as a whitish powder (6.76 g, 38%). M.p. 169.5–170.5 °C.

H, CH₃), 1.34 (s, 9 H, CH₃), 3.27 (s, 1 H, ϵCH), 7.17 (dd, J_H,H

4

3

4

= 8.1, J_H,H= 2.1 Hz, 1 H), 7.38 (td, J_H,H= 7.7, J_H,H= 3.0 Hz,

¹H NMR (300 MHz, CDCl₃, 25 °C): δ = 1.31 (s, 18 H, CH₃), 7.17 2 H), 7.49–7.61 (m, 6 H), 7.65 (dd, J_H,H= 8.1, J_H,H= 1.5 Hz, 1

3

4

3

4

3

(dd, J_H,H= 8.2, J_H,H= 2.2 Hz, 2 H), 7.38 (t, J_H,H= 7.8 Hz, 2

H), 7.68 (d, J_H,H= 2.1 Hz, 1 H), 7.72 (d, J_H,H= 8.0 Hz, 1 H),

3822

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Eur. J. Org. Chem. 2006, 3809–3825

Synthesis of macrocyclic molecular rods as potential electronic devices

FULL PAPER

4

7.75 (d, J_H,H= 1.6 Hz, 1 H), 7.77 (t, J_H,H= 1.5 Hz, 2 H), 7.84 0.36 mmol), CuI (0.0686 g, 0.36 mmol) and (4-ethynyl-2,3-dini-

(d, J_H,H= 8.2 Hz, 1 H), 8.21 (d, J_H,H= 1.5 Hz, 1 H) ppm. ¹³C

trophenylethynyl)trimethylsilane 27 (1.2739 g, 4.42 mmol) in de-

3

4

NMR (75 MHz, CDCl₃, 25 °C): δ = 31.1 (CH₃), 31.2 (CH₃), 46.6 gassed toluene (200 mL). CC (silica, hexane/CH₂Cl₂, 7:3) provided

(SC), 47.2 (SC), 81.0 (CϵC), 81.8 (CϵC), 88.2 (CϵC), 89.28 37 as a yellow solid (0.966 g, 23 %). M.p. 76–78 °C. ¹H NMR

(CϵC), 89.31 (CϵC), 89.8 (CϵC), 91.9 (CϵC), 92.7 (CϵC), 93.7 (300 MHz, CDCl₃, 25 °C): δ = 0.25 (s, 9 H, SiCH₃), 1.31 (s, 9 H,

(CϵC), 97.5 (CϵC), 102.2, 118.8, 123.31, 123.38, 123.41, 123.6,

124.9, 126.2, 128.5, 128.79, 128.81, 130.1, 131.7, 132.1, 132.6, 1 H), 7.39 (t, J_H,H= 7.8 Hz, 2 H), 7.48–7.61 (m, 6 H), 7.65 (d,

132.9, 133.32, 133.34, 134.8, 135.01, 135.05, 135.1, 136.1, 137.09,

137.11, 138.5, 139.0, 140.4, 140.9, 149.2 ppm. C₄₈H₃₆INO₂S₂= 8.3 Hz, 1 H), 7.74–7.79 (m, 3 H), 7.83 (d, J_H,H= 8.3 Hz, 1 H)

(849.84): calcd. C 67.84, H 4.27, N 1.65; found C 67.95, H 4.59, N

1.61. MS (MALDI-TOF): calcd. for C₄₈H₃₆INO₂S₂849.1227; (CH₃), 31.19 (CH₃), 46.6 (SC), 47.3 (SC), 86.4 (CϵC), 87.7 (CϵC),

CH₃), 1.34 (s, 9 H, CH₃), 7.17 (dd, ³J_H,H= 8.2 Hz, ⁴J_H,H= 2.2 Hz,

3

4

3

³J_H,H= 8.3 Hz, 1 H), 7.68 (d, J_H,H= 2.1 Hz, 1 H), 7.73 (d, J_H,H

3

ppm. ¹³C NMR (75 MHz, CDCl₃, 25 °C): δ = –0.5 (SiCH₃), 31.06

found 849.3932.

89.2 (CϵC), 89.4 (CϵC), 91.9 (CϵC), 92.7 (CϵC), 94.0 (CϵC),

95.8 (CϵC), 98.8 (CϵC), 102.2 (CϵC), 108.5, 118.3, 118.6, 123.1,

123.2, 123.46, 123.54, 126.3, 128.78, 128.83, 130.0, 131.7, 132.0,

132.7, 133.3, 134.7, 135.0, 135.3, 135.6, 136.0, 136.9, 138.4, 138.9,

140.4, 140.9, 144.3, 145.7 ppm. MS (MALDI-TOF): calcd. for

C₅₁H₄₃IN₂O₄S₂Si 966.1473; found 966.2072.

3,22-Bis(tert-butylsulfanyl)-28-nitro-5,6,12,13,19,20,25,26,31,32-de-

cadehydro-27,30-etheno-7,11:14,18-dimethenodibenzo[a,k]cycloocta-

cosane (36): Pd(PPh₃)₄(1 equiv., 1.6694 g) and CuI (1 equiv.,

0.2742 g) were added under nitrogen to a solution of 35 (1.2277 g,

1.44 mmol) in dry and degassed toluene (6 L), (iPr)₂NEt (20 mL).

The reaction mixture was stirred for 20 h at room temperature. All

solvents were removed and the residue was dissolved in CH₂Cl₂.

Absorption on silica gel and subsequent CC (silica, hexane/

3-{[5ЈЈ-tert-Butylsulfanyl-3ЈЈ-(4ЈЈЈ-ethynyl-2ЈЈЈ,3ЈЈЈ-dinitrophenyl)-

ethynyl]phenylethynyl}-3Ј-(5ЈЈЈЈ-tert-butylsulfanyl-2ЈЈЈЈ-iodophenyl-

ethynyl)tolane (38): A similar protocol as described for 35 has been

CH₂Cl₂, 1:2 to 1:1) afforded the macrocycle 36 as a yellow solid applied: Used were 37 (0.950 g, 0.98 mmol), KF (1.2 equiv.,

(0.3116 g, 30%). No m.p., compound decomposes above 345 °C. 1.18 mmol, 0.0685 g) and degassed MeOH/CH₂Cl₂(150 mL) for

¹H NMR (300 MHz, CDCl₃, 25 °C): δ = 1.35 (s, 18 H, CH₃), 7.39 1 h. The residue was purified by CC (silica, hexane/CH₂Cl₂, 1:1) to

3

(t, J_H,H= 7.6 Hz, 2 H), 7.48–7.58 (m, 7 H), 7.63 (d, J_H,H

=

provide 38 (0.8612 g, 98%) as a yellow solid. M.p. 95–97 °C. ¹H

NMR (300 MHz, CDCl₃, 25 °C): δ = 1.30 (s, 9 H, CH₃), 1.33 (s, 9

8.0 Hz, 1 H), 7.68–7.77 (m, 4 H), 7.97 (s, 2 H), 8.37 (s, 1 H) ppm.

¹³C NMR (75 MHz, [D₈]THF, 25 °C): δ = 29.0 (CH₃), 44.8 (SC), H, CH₃), 3.57 (s, 1 H, ϵCH), 7.15 (dd, J_H,H= 8.2 Hz, J_H,H

=

3

4

3

44.9 (SC), 86.5 (CϵC), 87.3 (CϵC), 87.4 (CϵC), 88.1 (CϵC), 90.1 2.2 Hz, 1 H), 7.36 (t, J_H,H= 7.7 Hz, 2 H), 7.44–7.59 (m, 6 H),

(CϵC), 90.5 (CϵC), 91.9 (CϵC), 92.0 (CϵC), 92.1 (CϵC), 95.1 7.65 (d, J_H,H= 8.2 Hz, 1 H), 7.67 (d, J_H,H= 2.1 Hz, 1 H), 7.71–

(CϵC), 116.4, 121.9, 122.0, 122.1, 122.8, 123.4, 123.6, 124.4, 124.5,

3

4

3

7.77 (m, 4 H), 7.81 (d, J_H,H= 8.2 Hz, 1 H) ppm. ¹³C NMR

126.2, 127.28, 127.34, 129.74, 129.72, 130.0, 130.1, 130.4, 130.8, (75 MHz, CDCl₃, 25 °C): δ = 31.0 (CH₃), 31.1 (CH₃), 46.5 (SC),

133.1, 133.2, 133.4, 133.8, 134.0, 135.3, 138.1, 148.6 ppm. 47.3 (SC), 75.3 (CϵC), 86.2 (CϵC), 87.6 (CϵC), 88.7 (CϵC), 89.2

C₄₈H₃₅NO₂S₂(721.93): calcd. C 79.86, H 4.89, N 1.94; found C

(CϵC), 89.4 (CϵC), 91.9 (CϵC), 92.6 (CϵC), 94.0 (CϵC), 99.2

79.63, H 4. 66, N 2.05. MS (MALDI-TOF): calcd. for (CϵC), 102.2, 117.1, 119.2, 123.0, 123.1, 123.2, 123.3, 123.4, 126.2,

C₄₈H₃₅NO₂S₂721.2104; found 721.6479.

128.7, 128.8, 129.9, 131.6 (broad), 131.96, 131.98, 132.7, 133.2,

134.5, 134.9, 135.5, 136.0, 136.1, 136.8, 138.4, 138.8, 140.3, 140.7,

143.9, 145.7 ppm. C₄₈H₃₅IN₂O₄S₂(894.84): calcd. C 64.43, H 3.94,

N 3.13; found C 64.43, H 4.18, N 3.33. MS (MALDI-TOF): calcd.

for C₄₈H₃₅IN₂O₄S₂894.1078; found 894.3807.

3,22-Bis(acetylsulfanyl)-28-nitro-5,6,12,13,19,20,25,26,31,32-de-

cadehydro-27,30-etheno-7,11:14,18-dimethenodibenzo[a,k]cycloocta-

cosane (1): To a solution of 36 (20.1 mg, 0.0278 mmol) in degassed

and dry CH₂Cl₂(25 mL), toluene (1 mL) and acetyl chloride

(5 mL) was added dropwise a solution of BBr₃in CH₂Cl₂(0.5 mL)

at room temperature. After the addition of BBr₃, the reaction mix-

ture was stirred for 15 min and subsequently pored on ice water.

The organic compounds were extracted with CH₂Cl₂. Evaporation

of the solvent, absorption of the residue on silica gel and subse-

quent purification by CC (silica, hexane/CH₂Cl₂, 1:2) afforded the

target compound 1 as a yellow solid (9.5 mg, 49 %). M.p. 296–

3,22-Bis(tert-butylsulfanyl)-28,29-dinitro-5,6,12,13,19,20,25,

26,31,32-decadehydro-27,30-etheno-7,11:14,18-dimethenodibenzo-

[a,k]cyclooctacosane (39): A similar protocol as described for 36

has been applied: Used were compound 38 (0.8601 g, 0.96 mmol),

Pd(PPh₃)₄(0.7513 g, 0.65 mmol), CuI (0.183 g, 0.96 mmol),

(iPr)₂NEt (5 mL) in degassed toluene (2.5 L) for 6 h at room tem-

perature. The course of the reaction was monitored by TLC. After

298 °C. ¹H NMR (500 MHz, C₂D₂Cl₄, 25 °C): δ = 2.47 (s, 6 H, disappearance of the starting material 38, the, solvents were re-

CH₃), 7.37–7.44 (m, 4 H), 7.54–7.59 (m, 4 H), 7.66 (d, J_H,H

3

=

moved and the residue was adsorbed on silica gel. Purification by

8.2 Hz, 1 H), 7.67–7.72 (m, 4 H), 7.74 (s, 1 H), 7.95–8.00 (m, 2 H),

CC (silica, hexane/CH₂Cl₂, 2:1 to 1:1) provided the macrocycle 39

8.38 (br. s, 1 H) ppm. ¹³C NMR (126 MHz, C₂D₂Cl₄, 25 °C): δ =

(0.0836 g, 11%) as a yellow solid. No m.p., compound decomposes

1

30.3 (CH₃), 87.8 (CϵC), 88.98 (CϵC), 89.03 (CϵC), 89.7 (CϵC), above 350 °C. H NMR (300 MHz, CDCl₃, 25 °C): δ = 1.35 (s, 18

91.9 (CϵC), 94.0 (CϵC), 94.1 (CϵC), 97.0 (CϵC), 100.3 (CϵC), H, CH₃), 7.40 (t, J_H,H= 7.6 Hz, 2 H), 7.49–7.59 (m, 8 H), 7.66–

117.9, 122.8, 122.9, 123.0, 123.1, 124.1, 125.2, 125.4, 126.3, 126.4,

3

7.70 (m, 2 H), 7.73–7.76 (m, 2 H), 8.03 (s, 2 H) ppm. ¹³C NMR

127.9, 128.69, 128.73, 129.7, 131.30, 131.33, 131.7, 131.8, 132.4, (125 MHz, CDCl₃, 25 °C): δ = 31.2 (CH₃), 47.4 (SC), 86.5 (CϵC),

132.9, 133.66, 133.67, 134.5, 134.7, 134.9, 135.1, 136.9, 149.2, 192.6

(C=O), 192.7 (C=O) ppm. C₄₄H₂₃NO₄S₂(693.79): calcd. C 76.17,

88.2 (CϵC), 89.3 (CϵC), 94.0 (CϵC), 99.1 (CϵC), 118.7, 123.3,

123.5, 123.8, 126.2, 129.2, 131.7, 132.1, 132.8, 134.8, 135.2, 136.2,

H 3.34, N 2.02; found C 75.98, H 3.31, N 2.16. MS (MALDI- 137.1, 140.1, 145.2 ppm. MS (MALDI-TOF): calcd. for

TOF): calcd. for C₄₄H₂₃NO₄S₂693.1063; found 693.2740. C₄₈H₃₄N₂O₄S₂766.1955; found 766.5106.

3-{[5ЈЈ-tert-Butylsulfanyl-3ЈЈ-(2ЈЈЈ,3ЈЈЈ-dinitro-4ЈЈЈ-trimethylsilyl- 3,22-Bis(acetylsulfanyl)-28,29-dinitro-5,6,12,13,19,20,25,26,31,32-

ethynylphenyl)ethynyl]phenylethynyl}-3Ј-(5ЈЈЈЈ-tert-butylsulfanyl-

2ЈЈЈЈ-iodophenylethynyl)tolane (37): A similar protocol as described

for 33 has been applied: 32 (1.5 equiv., 6.63 mmol, 5.3589 g), de-

gassed toluene (1000 mL), (iPr)₂NEt (4 mL), Pd(PPh₃)₄(0.4210 g,

decadehydro-27,30-etheno-7,11:14,18-dimethenodibenzo[a,k]cyclo-

octacosane (2): A similar protocol as described for 1 has been ap-

plied: Used were 39 (20.0 mg, 0.0261 mmol), degassed CH₂Cl₂

(25 mL), toluene (1 mL), acetyl chloride (5 mL) and a solution of

Eur. J. Org. Chem. 2006, 3809–3825

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3823

A. Błaszczyk, M. Chadim, C. v. Hänisch, M. Mayor

FULL PAPER

boron tribromide (0.5 mL of 1  solution in CH₂Cl₂). CC (silica,

hexane/CH₂Cl₂, 1:2) afforded target structure 2 (10.2 mg, 53%) as a

3,22-Bis(tert-butylsulfanyl)-30,33-carbonyl-5,6,12,13,19,20,25,26-

octadehydro-7,11:14,18:27,31-trimethenodibenzo[a,k]azacyclo-

yellow solid. M.p. Ͼ 410 °C. ¹H NMR (300 MHz, C₂D₂Cl₄/CDCl₃, nonacos-32-ene 32-Oxide (43): The macrocycle 36 was heated for

25 °C): δ = 2.47 (s, 6 H, CH₃), 7.36–7.44 (m, 4 H), 7.51–7.58 (m, 4 short time in order to dissolve it in toluene. During heating the

3

H), 7.62 (d, J_H,H= 8.1 Hz, 2 H), 7.67 (br. s, 4 H), 8.03 (s, 2 H)

ppm. ¹³C NMR (126 MHz, C₂D₂Cl₄, 25 °C): δ = 29.2, 85.7, 87.1,

88.7, 94.1, 98.3, 118.0, 122.3, 122.6, 123.6, 126.2, 128.5, 130.3,

131.1, 131.6, 132.7, 133.4, 134.4, 134.8, 136.6, 144.3, 192.3 ppm.

MS (MALDI-TOF): calcd. for C₄₄H₂₂N₂O₆S₂738.0914; found

738.3336.

yellow solution became orange. The solvent was removed and the

residue was dissolved in dichloromethane and methanol was added.

From this solution an appropriated crystal (orange crystal) was ob-

tained for performing of X-ray. No m.p., compound decomposes

1

above 380 °C. H NMR (300 MHz, CDCl₃, 25 °C): δ = 1.35 (s, 9

4

H, CH₃), 1.38 (s, 9 H, CH₃), 7.13 (t, J_H,H= 1.4 Hz, 1 H), 7.28–

7.56 (m, 8 H), 7.61–7.69 (m, 3 H), 7.73–7.78 (m, 2 H), 7.84 (br. s,

3,3Ј-Bis{[5ЈЈ-tert-butylsulfanyl-2ЈЈ-(4ЈЈЈ-ethynyl-2ЈЈЈ-nitrophenyl)-

ethynylphenyl]ethynyl}tolane (40): A similar deprotection protocol

has been applied as for the preparation of 35. Compound 40 was

obtained as a pale yellow solid (0.681 g, yield 88%). M.p. 204–

206 °C. ¹H NMR (300 MHz, CDCl₃, 25 °C): δ = 1.36 (s, 18 H,

3

4

1 H), 7.95 (dd, J_H,H= 7.5 Hz, J_H,H= 1.4 Hz, 1 H), 7.98 (br. s, 1

H) ppm. ¹³C NMR (75 MHz, CDCl₃, 25 °C): δ = 31.2 (CH₃), 31.3

(CH₃), 47.2 (SC), 47.3 (SC), 88.4 (CϵC), 89.0 (CϵC), 89.2 (CϵC),

89.3 (CϵC), 93.2 (CϵC), 92.9 (CϵC), 94.2 (CϵC), 95.6 (CϵC),

116.9, 122.2, 122.4, 123.1, 123.2, 123.4, 123.5, 124.0, 125.3, 126.5,

127.2, 128.9, 129.0, 130.2, 130.5, 130.7, 131.0, 131.2, 131.5, 131.7,

134.9, 135.6, 135.9, 136.0, 136.3, 136.5, 137.2, 139.8, 140.4, 148.2,

183.8 (C=O) ppm. MS (MALDI-TOF): calcd. for C₄₈H₃₅NO₂S₂

721.2104; found 721.4700.

3

CH₃), 3.29 (s, 2 H, ϵCH), 7.38 (t, J_H,H= 7.8 Hz, 2 H), 7.49–7.58

(m, 8 H), 7.61 (d, ³J_H,H= 8.0 Hz, 2 H), 7.64 (dd, ³J_H,H= 8.0, ⁴J_H,H

3

= 1.6 Hz, 2 H), 7.72 (d, J_H,H= 8.0 Hz, 2 H), 7.75–78 (m, 4 H),

4

8.19 (d, J_H,H= 1.5 Hz, 2 H) ppm. ¹³C NMR (75 MHz, CDCl₃,

25 °C): δ = 31.2, 47.2, 81.0, 81.8, 88.2, 89.3, 89.9, 93.7, 97.5, 118.8,

123.39, 123.44, 123.6, 124.9, 126.2, 128.4, 128.8, 131.91, 131.95,

132.6, 135.0, 135.1, 135.2, 136.1, 137.1, 140.4, 149.2 ppm.

C₅₈H₄₀N₂O₄S₂(893.08): calcd. C 78.00, H 4.51, N 3.14; found C

77.90, H 4. 53, N 3.14. MS (MALDI-TOF): calcd. for

C₅₈H₄₀N₂O₄S₂892.2424; found 892.4198.

Acknowledgments

We are thankful for financial support by the Volkswagen Founda-

tion (I 80–880) and by the German Ministry of Education and

Research within the network project MOLMEM (BMBF-FZK

13 N 8360).

2,23-Bis(tert-butylsulfanyl)-8,17-dinitro-5,6,11,12,13,14,19,20,25,

26,32,33,39,40-tetradecadehydro-7,10:15,18-dietheno-27,31:34,38-di-

methenodibenzo[a,o]cyclodotriacontane (41): To the open-chain pre-

cursor 40 (61.3 mg, 0.069 mmol) in acetonitrile (1500 mL) and

dichloromethane (20 mL) was added Cu(OAc)₂(66.7 mg,

3.34 mmol), and the mixture was heated to 80 °C for 6 h. After

removal of the solvents the residue was absorbed on silica gel. Puri-

fication by CC (silica, hexane/CH₂Cl₂, 1:1) afforded the macrocycle

41 (22.0 mg, 36%). No m.p., compound decomposes above 350 °C.

¹H NMR (300 MHz, CDCl₃, 25 °C): δ = 1.35 (s, 18 H, CH₃), 7.28–

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7.32 (m, 4 H), 7.49 (dd, 2 H, J_H,H= 8.1, J_H,H= 1.5 Hz), 7.51–

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1

above 190 °C. H NMR (300 MHz, CDCl₃, 25 °C): δ = 2.47 (s, 6

H, CH₃), 7.28–7.31 (m, 4 H), 7.44 (dd, ³J_H,H= 8.1, ⁴J_H,H= 1.5 Hz,

3

4

2 H), 7.47 (dd, J_H,H= 8.1, J_H,H= 1.5 Hz, 2 H), 7.49–7.54 (m, 2

H), 7.59–7.66 (m, 6 H), 7.76 (d, ³J_H,H= 8.1 Hz, 2 H), 8.13 (d, ⁴J_H,H

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6

3

¯

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=

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Received: April 17, 2006

Published Online: July 21, 2006

Eur. J. Org. Chem. 2006, 3809–3825

www.eurjoc.org

3825

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Synthesis of macrocyclic molecular rods as potential electronic devices

DOI: 10.1002/ejoc.200600336

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