Synthesis of fluorine-containing molecular rotors and their assembly on gold nanoparticles

FULL PAPER

DOI: 10.1002/ejoc.201000252

Synthesis of Fluorine-Containing Molecular Rotors and Their Assembly on

Gold Nanoparticles

Dominic Thibeault,^[a]Michèle Auger,^[a]and Jean-François Morin*^[a]

Keywords: Alkynes / Gold / Nanostructures / C-C coupling / Molecular machines

A series of eight rotors containing thiol groups for attachment

to gold surfaces and fluorine atoms for solid-state ¹⁹F NMR

spectroscopy have been prepared through linear, multistep

synthesis. The common rotating part of the rotors (rotator),

consisting of a 2,6-difluorobenzene moiety, is introduced into

rotors were assembled on gold nanoparticles (AuNPs) and

preliminary characterization was performed on these AuNPs

in order to study the effects of the sizes of the molecules on

the packing behaviour on the AuNP surfaces. As expected,

we found that linear molecules adopt more closely packed

the rotor structure through an unusual regioselective Sono- structures on the surfaces than their bulky analogues. This

gashira coupling with 2,6-difluoro-1,4-diiodobenzene. Rotors

with different bulky trityl headgroups were prepared, along

with their linear, less hindered analogues. These molecular

offers a very promising opportunity to study rotation dynam-

ics at the molecular level by solid-state NMR spectroscopy.

preparation, which makes the investigation of large num-

bers of rotors very tedious. Investigation of several mole-

cules is necessary, however, for identification of the param-

eters that influence the rotation dynamics at the molecule

level and for the eventual development of faster and more

efficient rotors. Two different strategies through which to

increase the analytical capability can hence be employed:

1) the development of a more versatile and rapid characteri-

zation technique, or 2) adaptation of an already existing

useful technique to allow studies of motions on surfaces.

Because the second strategy is much more realistic and easy

to undertake, we envisaged the use of solid-state NMR

spectroscopy to study the rotation dynamics of molecular

rotors mounted on gold nanoparticles (AuNPs). AuNPs

could be very useful because they offer higher surface con-

tact and organic content than flat surfaces, thus providing

enough signals in solid-state NMR spectroscopy to allow

dynamic study on surfaces to be carried out. The first steps

towards the validation of our strategy are to prepare a vari-

ety of rotors that exhibit structural variation, to assemble

them on AuNPs and to characterize the resulting AuNPs in

order to assess whether or not they are suitable and reliable

test beds for further rotor investigation.

As the first step of this long-term project, here we report

the detailed synthesis of fluorine-containing rotors featur-

ing structural differences with regard to the stator and the

anchoring groups used for attachment on AuNPs. An ideal-

ized schematic representation of the rotors attached to the

surface of a gold nanoparticle is presented in Figure 1. The

primary goal of this study was to find efficient and versatile

synthetic pathways for the preparation of a series of thiol-

containing rotors that can be assembled on gold nanopar-

ticles. The synthesis and characterization of AuNPs by ther-

Introduction

Synthetic molecular machines, or nanomachines, mim-

icking the functions of those found in nature, have attracted

lot of attention in the past fifteen years.^[1–4]Their prepara-

tion, but most importantly their characterization and their

use in real devices, is one of the biggest challenges facing

researchers involved in nanoscience. The inherent difficult-

ies in predicting the dynamic behaviour of such tiny ma-

chines arises from the non-deterministic nature of quantum

mechanics, which governs motion at the molecular level.

Nonetheless, researchers have developed very powerful

tools to study the dynamics of motions in both simple and

complex molecules. Among others, NMR spectroscopy has

proved to be a very useful and versatile tool to study rapid

molecular motions, especially rotation and translation, both

in solution^[5–8]and in the solid state.^[9–12]

The characterization of molecular motions on surfaces

and at interfaces is much more difficult, however, because

NMR spectroscopy is not suitable for the study of mole-

cules on flat surfaces, because of the low concentrations of

the active molecules per surface unit. More sophisticated

techniques such as scanning tunnelling microscopy (STM)

have thus been used extensively to obtain information on

molecular dynamics on surfaces.^[13–17]Although very help-

ful, STM analysis suffers from time-consuming sample

[a] Département de chimie and Centre de recherche sur les

matériaux avancés (CERMA), Université Laval, Pavillon

A.-Vachon,

1045 Ave. de la Médecine, Québec, QC G1V 0A6, Canada

Fax: +1-418-656-7916

E-mail: jean-francois.morin@chm.ulaval.ca

Supporting information for this article is available on the

WWW under http://dx.doi.org/10.1002/ejoc.201000252.

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mogravimetric analysis (TGA) and transmission electron

microscopy (TEM) are also presented. The preliminary

characterization of AuNPs was undertaken in order to de-

termine the influence of the size of the stator on the foot-

print of the molecular rotor on an AuNP surface in the

context of the creation of free volume inside the monolayer.

It also helps evaluation of the quality of AuNPs obtained

when bulky molecules are used as surface ligands during

the synthesis. It should be noted that the thorough charac-

terization of the nanoparticles and their solid-state ¹⁹F

NMR analysis will be presented in forthcoming articles.

Figure 1. Idealized schematic representation of a molecular rotor

on an AuNP surface.

Figure 2. Structures of rotors 1–8.

Results and Discussion

The structural characteristics of the rotors were espe-

For the purpose of our study, we decided to evaluate

cially designed to maximize speeds of rotation and to pro- three different trityl derivatives – the 4-octyloxy derivative

vide clear and strong NMR signals. Firstly, the rotator part, 15 (Scheme 2, below), the 3-methyl derivative 16 and the

containing fluorine atoms, is attached to two ethynyl groups 3,5-di-tert-butyl derivative 17 – as stators. These groups are

in a para relationship, because the rotation of a phenyl expected to provide different packing behaviour patterns on

group around an alkyne is almost barrierless in the gas the AuNP surfaces. It is also well known that the endgroups

phase, allowing fast rotation at room temperature.^[18]Sec- of molecules attached to AuNPs can change their solubili-

ondly, fluorine atoms were introduced on the rotator of ties and aggregation properties.^[23]For purposes of com-

each rotor because ¹⁹F is one of the most sensitive nuclei in parison in the context of free volume creation on AuNP

NMR spectroscopy, thus providing strong signals even surfaces, linear, less hindered analogues of all the bulky

when the molar percentage of fluorine in a molecule is rotors were also synthesized.

low.^[19]Thirdly, trityl derivatives were used as the stators

The syntheses of the rotors are shown in Scheme 1 to

because they provide good protecting pockets around the Scheme 9. Firstly, the rotator (compound 10, Scheme 1), the

rotators by creating free volume around them.^[9–12]The cre- central building block of all the rotors, was synthesized in

ation of free volume near the rotator is of particular impor- two steps starting from 2,6-difluoroaniline, on which we

tance for ensuring fast rotation of the rotator, as has been performed an iodination by a procedure published by Em-

shown several times by the Garcia–Garibay group in crys- manuvel et al.^[24]to obtain compound 9 in modest yields

talline state rotors.^[20–22]Additionally, the presence of trityl (53%). Some other iodination methods including the use

groups at the top of the monolayer is expected to protect of benzyltrimethylammonium dichloroiodate,^[25]molecular

the rotator from intermolecular contacts (AuNP–AuNP) in iodine with HgO^[26]and iodine with Ag₂SO₄^[27]gave poorer

the solid state and interdigitation of the long alkyl chains yields or no reaction at all. The conversion yield of 2,6-

used to solubilize AuNPs. Finally, a thiol group was intro- difluoroaniline into 9 in our hands is as good as that re-

duced onto each rotor to allow attachment to AuNPs. It is ported in the literature with molecular iodine and

worth mentioning that different spacers between the rotator AgNO₃.^[28]The amino group was then transformed into a

and the thiol have been used in order to study the influence diazonium salt by treatment with BF₃·Et₂O and tBuONO.

of the F–Au distance on solid-state ¹⁹F NMR spectra in Interestingly, the use of KI to afford compound 10 directly

further experiments. The structures of all the rotors pre- from the diazonium salt intermediate was unsuccessful and

pared for this study are presented in Figure 2.

a large amount of the protonated intermediate was reco-

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Fluorine-Containing Molecular Rotors and Assembly on Gold Nanoparticles

vered. To overcome this problem, diethylamine was added

to the diazonium salt in order to provide a triazene interme-

diate, which after filtration through silica gel was heated at

160 °C in iodomethane under argon in a pressurized vessel.

Compound 10 was then obtained in good yield (81%) from

the aniline 9. The reaction time and the temperature needed

to convert the triazene intermediate into its iodo derivative

(compound 10) were much higher than usually required in

examples reported in the literature for different sub-

strates.^[29]In fact, we observed that the reactivity at the 1-

position in 2,6-difluorobenzene derivatives is much lower

than we had expected and so we exploited the low reactivity

of compound 10 at its 1-position to perform a regioselective

Sonogashira coupling with hex-5-yn-1-ol to provide solely

compound 11, in 95% yield and with no sign of reaction at

the site between the two fluorine atoms.

Scheme 2. Synthesis of the trityl stators.

Scheme 1. Synthesis of fluorine-containing building block.

The synthesis of the rotor 1 is shown in Scheme 2 and

Scheme 3. For this model we chose to introduce octyl

chains to improve the solubility of the nanoparticles. Nucleo-

philic substitution of 4-bromophenol on 1-bromooctane

afforded compound 12 in very good yield (92%). This bro-

moaryl was then converted into compound 13 by treatment

with nBuLi and diethylcarbonate in 68% yield. The alcohol

was efficiently converted into an alkyne by treatment with

acetyl chloride and subsequently with ethynylmagnesium

bromide, providing compound 15 in an excellent yield

(95%).

This compound was then coupled to compound 10 to

afford compound 18 in 78% yield (Scheme 3). Because

compounds 15 and 18 have similar polarities, an excess of

compound 10 was required to ensure complete conversion

of compound 15.

Scheme 3. Synthesis of rotor 1.

For the same reasons as mentioned above, Sonogashira

coupling between compound 18 and propargyl alcohol was

difficult to achieve. Indeed, 1.5 equiv. of propargyl alcohol, thesis of compound 19 in a satisfactory yield of 69%. This

4 mol-% of palladium catalyst and 4 mol-% of CuI in THF lower reactivity of the iodine atom between the two fluorine

at 60 °C for several hours were needed to perform the syn- atoms is consistent with what we had observed in the syn-

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D. Thibeault, M. Auger, J.-F. Morin

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thesis of compound 11. Similar low reactivity (15–30% compound 10 was necessary to achieve complete conversion

yields) has recently been reported for Sonogashira coupling of compound 22 into compound 23 and to enable purifica-

under harsh conditions with 1,4-dibromo-2,3,5,6-tetra- tion. The synthesis of compound 24 was achieved in a 91%

fluorobenzene as substrate.^[30]

yield by Sonogashira coupling between compound 23 and

The alcohol function of compound 19 was replaced by a propargyl alcohol under the more severe conditions de-

thioacetate by treatment with thioacetic acid under Mitsu- scribed previously for the synthesis of compound 19. The

nobu conditions to afford compound 20 in good yield alcohol was then replaced by a bromine atom (PPh₃/CBr₄)

(66%). Finally, the thioacetate 20 was converted into the to afford 25 in excellent yield (92%). Compound 25 was

rotor 1 in 80% yield by acidic hydrolysis followed by a mild converted into compound 26 in 96% yield by treatment

oxidation with molecular iodine.^[31,32]

with potassium thioacetate. This method was used instead

Our comparative model for the rotor 1 was the linear, of the Mitsunobu reaction – as in the case of compound

less hindered rotor 2 (Figure 2), and the synthetic pathway 20 – because the latter method leads to a significant amount

used to prepare this is shown in Scheme 4. Initially, com- of side products, which makes purification difficult. Finally,

pound 12 was converted in excellent yield (96%) into com- the rotor 2 was obtained from compound 26 in modest

pound 21 under Buchwald conditions for Sonogashira cou- yield (54%) by the same pathway as shown in Scheme 3 for

pling of unactivated aryl bromides.^[33]It is worth men- the rotor 1.

tioning that, in our hands, standard Sonogashira conditions

The synthesis of the rotor 3 (Figure 2) is shown in

failed to provide compound 21 in reasonable yield. The al- Scheme 5 and was similar to the synthesis described above.

kyne was then deprotected and compound 22 was coupled Compound 11 was coupled with compound 15 under the

with compound 10 under Sonogashira coupling conditions improved Sonogashira conditions described above to afford

to provide compound 23 in good yield (80%). As in the compound 27 in 91% yield. Addition of propargyl alcohol

synthesis of compound 15 discussed above, an excess of at the end of the reaction as a “workup” technique is neces-

sary to destroy any residual compound 11 left and, conse-

quently, to enable purification of 27 by column chromatog-

raphy. The yield obtained for this reaction is quite high in

view of the very low reactivity of compound 11 observed

previously in Sonogashira coupling at room temperature.

To obtain such a yield however, the reactions have to be

run for two days at 60 °C with twice the amount of catalyst

Scheme 4. Synthesis of rotor 2.

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Scheme 5. Synthesis of rotors 3, 5, and 51.

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Fluorine-Containing Molecular Rotors and Assembly on Gold Nanoparticles

and copper(I), thus providing further evidence of the low performed as shown in Scheme 5. A Sonogashira coupling

reactivities of the 1-positions in 2,6-difluorobenzene deriva- between compound 16 and compound 11 was performed

tives. The further synthetic steps used were the same as under the improved conditions to afford compound 28 in

those described previously, with compounds 30 and 33 and 99% yield. This compound was then converted into com-

the rotor 3 being obtained in 97%, 92% and 86% yields, pounds 31 and 34 and the rotor 5 in 97%, 94% and 75%

respectively.

yields, respectively.

The rotor 4 (Figure 2), the less hindered analogue of the

The rotor 6 (Figure 2), the less hindered analogue of the

rotor 3, was synthesized as shown in Scheme 6. Sonogashira rotor 5, was synthesized as shown in Scheme 6. A Sonoga-

coupling between compounds 22 and 11 afforded com- shira coupling between 3-ethynyltoluene and compound 11

pound 36 in 80% yield. As in the case of compound 27, afforded compound 37 in 57% yield, and this was further

addition of propargyl alcohol to destroy any residual com- transformed into compounds 39 and 41 and the rotor 6 in

pound 11 was necessary during the synthesis of 36. This 96%, 90% and 99% yields.

compound was further transformed into compounds 38 and

In order to simplify the synthesis of the rotors, we at-

40 and the rotor 4 in 96%, 95% and 94% yields, respec- tempted to assemble them through Sonogashira reactions

tively, under the usual reaction conditions.

either with the thioacetate derivative of 11 (I, Figure 3) or

with the disulfide derivative (II).^[34]This would have given

us the opportunity to perform fewer reactions once the

stator (trityl) group was attached to the rotor. In a first

attempt we used compound 15 and, surprisingly, no reac-

tion occurred. The reaction was also unsuccessful even with

a simpler alkyne such as propargylic alcohol. We believe

that catalyst poisoning with these intermediates is responsi-

ble for the failure of this reaction. Poisoning by sulfur is a

well known undesired event in palladium-catalysed sys-

tems.^[35,36]This inconvenience led us to use Sonogashira

coupling with 11 instead of I or II, resulting in a three-

steps-longer process for each rotor.

Scheme 6. Synthesis of rotors 4 and 6.

Figure 3. Sulfur-containing iodoarene.

In many cases the chromatographic purification of the

low-polarity synthetic intermediates described so far was

difficult because of similarities in the polarities of impuri-

To complete our study we needed a very bulky and hin-

ties and of the desired compounds. Moreover, co-elution dered model, so we designed the rotor 7 (Figure 2) as shown

phenomena that we attributed to the presence of long, fatty in Scheme 7 and the less hindered analogue rotor 8 (Fig-

octyl chains were also observed. This serious drawback ure 2) as shown in Scheme 8. Use of a diyne unit was cho-

prompted us to design another class of compounds, because sen in order to overcome van der Waals contacts between

we were expecting difficulties in the purification of the cor- the fluorine atoms and the tert-butyl groups. A Cadiot–

responding nanoparticles, which mostly relies on solubility Chodkiewicz cross-coupling reaction, the most commonly

and polarity differences. We therefore decided to synthesize used method to prepare unsymmetrical diynes,^[37,38]was

the rotors 5 and 6 by the same pathway as we had used for used for the synthesis of our models. Compound 42 was

the rotors 3 and 4. As shown in Scheme 2, 3-bromotoluene therefore prepared from compound 11 and TMSA in 99%

was converted into compound 14 in 93% yield by treatment yield under the improved Sonogashira conditions. Desi-

with nBuLi and diethylcarbonate. This alcohol was ef- lylation and bromination of 42 with AgNO₃and NBS af-

ficiently converted into compound 16 in good yield (81%) forded compound 43 in 74% yield. To avoid degradation,

by successive treatment with acetyl chloride and ethynyl- this compound has to be stored under argon in a dark place

magnesium bromide. The synthesis of the rotor 5 was then if not used immediately.

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Scheme 8. Synthesis of rotor 8.

suspected, so we attempted the reaction in the presence of

TMEDA, but this approach also failed. We also attempted

the palladium-catalysed cross-coupling reaction in pyrrol-

idine with PdCl₂(PPh₃)₂and CuI, by Alami’s procedure,^[39]

with the commercially available dodec-1-yne rather than

Scheme 7. Synthesis of rotor 7.

The bulky compound 17 (Scheme 2), synthesized by the compound 17 in order to prevent the waste of synthetic

same strategy as presented for other trityl derivatives (61% product. Unfortunately, the reaction simply failed, even

yield over four steps), was then coupled to compound 43 in when Pd₂(dba)₃·CHCl₃was used. Lei et al. recently re-

a palladium-catalysed Cadiot–Chodkiewicz reaction^[38]to ported a new hindered and electron-rich ligand designed to

give compound 44 in a low 32% yield (Scheme 7). It is note- accelerate the reductive elimination process and, conse-

worthy that palladium-catalysed coupling with Pd₂(dba)₃· quently, to improve the yields of palladium-catalysed Ca-

CHCl₃was used rather than the classical Cadiot–Chodkie- diot–Chodkiewicz reactions.^[40]In fact, competitive homo-

wicz conditions (CuCl, HONH₂·HCl, EtNH₂, MeOH)^[37]coupling of both alkynes and bromoalkynes is a major

because it is much more conveniently applied to large problem, which decreases cross-coupling yields consider-

hydrophobic molecules. In an attempt to improve the yield ably. We synthesized this ligand by Lei’s procedure^[41]and

of our reaction we performed the same reaction at 60 °C used it in the diyne synthesis under the optimized condi-

but only a poor 6% yield was obtained, indicating that tions described above, but no improvement was observed.

these conditions are not amenable to heating. We also at-

An alternative approach, used by Zhao et al.,^[42]to ob-

tempted to increase the efficiency of the coupling through tain the desired diyne was to synthesize a TMS-protected

the use of PdCl₂(PPh₃)₂under conventional Sonogashira diyne through a statistical Glaser reaction between 17 and

conditions, but the homocoupling by-product of 43 and 17 TMSA, followed by deprotection of the terminal diyne and

were the only products recovered, whereas the use of Sonogashira coupling with compound 11. Surprisingly, no

Pd(dba)₂in place of Pd₂(dba)₃·CHCl₃gives a slightly lower reaction occurred, even after several attempts to optimize

yield. Poor solubility of the cuprate intermediate of 17 was this reaction. We suspect the terminal diyne is unstable in

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Fluorine-Containing Molecular Rotors and Assembly on Gold Nanoparticles

solution, because the solution rapidly turned dark before its ble in common organic solvents to allow purification by

addition to the reaction mixture. In final attempts, classical precipitation. The best results were obtained by Brust’s

Cadiot–Chodkiewicz cross-coupling was performed by method,^[48]which enables the preparation of AuNPs of spe-

Gung’s^[43]and Negishi’s^[44]procedures, but both reactions cific dimensions (1–5 nm) with use of Murray’s modifica-

failed. The low reactivity of compound 17 at room tempera- tion.^[23]Indeed, the traditional Brust procedure consists of

ture is likely attributable to the steric hindrance caused by the reduction of a gold salt (HAuCl₄) with NaBH₄in the

the multiple tert-butyl groups on the trityl moieties. Heating presence of the desired thiol in a biphasic toluene/water

the reaction mixture in an attempt to accelerate the reaction mixture with tetrabutylammonium bromide (TBAB) as

also failed, with production of several unknown side prod- phase transfer agent. In Murray’s procedure, control of the

ucts.

core size is achieved by varying the temperature and ad-

The rotor 7 (Figure 2) was obtained in the same way as dition rate of the reducing agent, but also, more import-

used for the other rotors (Scheme 7). Compound 44 was antly, the HAuCl₄/disulfide molar ratio. An increase in this

further transformed into compound 45, compound 46 and molar ratio results in an increase in the nanoparticles’ dia-

rotor 7 in 94%, 87% and 82% yields, respectively, under meters. Subsequent reduction of HAuCl₄with NaBH₄in

the usual conditions.

the presence of TBAB and the desired disulfide afforded

The rotor 8 (Figure 2), the linear analogue of the rotor NP1–NP8 (NP1 corresponds to AuNP functionalized with

7, was synthesized in a similar manner as the other com- the rotor 1, and so on) in good quantities. The reaction

pounds (Scheme 8). 1-Bromo-3,5-di-tert-butylbenzene was conditions were carefully chosen to provide AuNPs with

coupled to TMSA by Sonogashira coupling and the TMS diameters of about 2.0 nm. All AuNPs were purified by suc-

group was removed by basic hydrolysis. Palladium-catalysed cessive precipitation and size exclusion chromatography. As

Cadiot–Chodkiewicz coupling of compounds 47 and 43 un- expected, the nature of the ligands dictates the solubilities

der the best conditions described above provided com- of the AuNPs; detailed purification procedures for all the

pound 48 in a good 67% yield, again indicating that the AuNPs are presented in the Experimental Section. Unfortu-

low reactivity of 17 with 43 was responsible for the poor nately, it was not possible to obtain NP1 and NP2 in pure

32% yield obtained for compound 44. Finally, the rotor 8 form despite all the purification steps performed. Similarly,

was obtained by the same approach as described for the NP3 and NP4 were found to contain small amounts (Ͻ5%)

other rotors: compound 48 was converted into compounds of unlinked ligand molecules. It is noteworthy that after a

49 and 50 and rotor 8 in 99%, 72% and 75% yields, respec- few precipitation cycles the AuNPs become cleaner and suc-

tively.

cessive attempts to precipitate them failed. The presence of

In order to assess whether or not the diyne linker is long small amounts of unlinked materials can be attributed to

enough to overcome the steric hindrance between the tert- van der Waals interactions between octyl chains of free and

butyl groups and the fluoroaryl rotator, the monoyne ana- attached ligands when precipitated in an unsuitable solvent.

logue, the rotor 51 (Scheme 5), was synthesized by the same Furthermore, size exclusion chromatography with Bio-

procedures as used for the rotors 3 and 5. However, the beads^©S-X1 was not suitable for removing the unlinked

synthesis of compound 29 under standard Sonogashira materials completely from NP1–NP4. NP1 and NP2 were

coupling conditions with trityl 17 once more gave a poor therefore discarded for TGA analysis, although NP3 and

yield, which is again attributable to the steric hindrance NP4 were analysed despite the presence of very small

caused by the six tert-butyl groups. It should be noted that amounts of unlinked materials.

rotor 51 was not assembled on AuNPs in the course of this

The NP1–NP8 diameter measurements were conducted

study, because we do not expect significant differences in by transmission electron microscopy (TEM; see the Sup-

the assembly behaviour of this molecule on AuNPs in rela- porting Information for all the images obtained). Examples

tion to rotor 7. Rotor 51 will be further assembled on of images obtained for NP5 and NP6 are shown in Fig-

AuNPs and studied by solid-state NMR to assess the im- ure 4. The AuNP diameters were calculated with the aid of

portance of the length of the alkyne spacer on the rotation ImageJ 1.41o software by conventional treatments such as

rate.

baseline correction, threshold adjustment and exclusion of

With rotors 1–8 in hand we proceeded to the synthesis poorly spherical shapes. Averages over hundreds of particles

of the AuNPs. In attempts to obtain high-quality AuNPs, afforded values with standard deviations similar to those

different synthetic methods were tried with varying degrees reported in the literature. The average AuNP sizes are

of success. As a first try, the synthesis of nanoparticles shown in Table 1. As predicted, the AuNP diameters range

capped with 4-dimethylaminopyridine (DMAP) as ligand from 1.8 to 2.3 nm with a standard deviation of ca. 25%,

according to Lennox’s procedure was attempted.^[45]How- which is consistent with other AuNPs prepared by the Mur-

ever, the reaction failed, with the recovery of a black pre- ray-modified Brust method.^[23]As shown in Figure 3, the

cipitate in a milky solution. We also attempted the synthesis AuNPs appears as individual particles of similar size and

of Schmid’s cluster,^[46]

a

phosphane-capped cluster no aggregation is observed. This behaviour has been ob-

[Au₅₅(PPh₃)₁₂Cl₆], by the improved procedure developed by served for all AuNPs synthesized in this study. This indi-

Hutchison.^[47]This procedure is essentially the same as the cates that the AuNPs synthesized in this study do not dis-

Brust approach but with triphenylphosphane as ligand. Un- play specific interaction that could lead to formation of ag-

fortunately, the AuNPs obtained in this case were too solu- gregates in the solid state.

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D. Thibeault, M. Auger, J.-F. Morin

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ing), MW_thiolis the alkanethiol molecular weight in mass

per molecule, γ is the coverage (ratio of thiolates to surface

Au atoms), ρ_Auis the atom density of bulk gold (58.01

atoms nm^–3) and AW_Auis the atomic weight of Au in mass

per atom. The γ values for NP3–NP8 are shown in Table 1.

These γ values are well below the 0.66 value (i.e., approx.

two thiolates per three surface gold atoms) calculated for

thioalkanes as ligands of AuNPs^[23]because NP3–NP8 do

not benefit from the strong van der Waals interactions of

alkanethiolates, which favour close packing on the sur-

face.^[49]

The organic loadings of AuNPs were also calculated as

molar ratios of organic ligands on surface gold atoms.

These calculations were performed through the use of the

number of surface gold atoms per total gold atoms as a

function of AuNP size.^[23]All data and graphs for the calcu-

lation of this molar ratio are available in the Supporting

Information. Briefly, the organic loss during TGA measure-

ment was converted into moles of organic materials and the

areas of nanoparticles were obtained by assumption of a

spherical shape, because this approximation has proved to

be very consistent with the true shape of AuNPs.^[49]Two

plots were then made with values reported by Hostetler:

1) the number of total gold atoms as a function of AuNP

radius and 2) the number of surface gold atoms as a func-

tion of total gold atoms of AuNPs. From the first graph we

obtained the total number of gold atoms from the radii of

NP3–NP8. These values were used in the second graph to

provide the corresponding number of surface gold atoms

from the radii of NP3–NP8. A simple ratio of the surface

gold atoms to total gold atoms afforded a surface coeffi-

cient, which was multiplied by the number of remaining

moles of gold after TGA measurements. This provides the

number of moles of gold atoms on the surface for NP3–

NP8. Finally, the ratio of moles of organic to moles

of surface gold atoms afforded the values reported in

Table 1.

The ratio values shown in Table 1 correlated surprisingly

well with the γ values calculated previously. These results

are in agreement with our hypothesis that sterically hin-

dered rotors provide lower surface loadings than their less

hindered analogues. In fact, NP3, NP5 and NP7 show mo-

lar ratios of 0.21, 0.23 and 0.20 and γ values of 0.22, 0.24

and 0.20, respectively, which means that about one mole-

cule is linked to about five surface gold atoms. In compari-

son, both NP4 and NP6 show a molar ratio of 0.32 and a

γ value of 0.33, suggesting about one molecule per three

surface gold atoms. The lower molar ratio and γ value of

NP8, 0.24 in both methods, could be explained by the more

significant van der Waals radius of the 3,5-di-tert-

butylphenyl unit, leading to poorer packing than in the

cases of NP4 and NP6. Nonetheless, the molar ratio of the

trityl analogue is below 0.24 with a value of 0.20. In light

of these results, one can agree that the use of a trityl group

Figure 4. Transmission electron micrographs of a) NP5 and

b) NP6. Scale bar = 20 nm.

Table 1. Sizes and compositions of NP3 – NP8.

AuNP Diameters

[nm]

Mass loss

[%]

γ

Organic/Au surface

[mol/mol]

NP3

NP4

NP5

NP6

NP7

NP8

1.8Ϯ0.6

2.0Ϯ0.5

1.9Ϯ0.5

2.0Ϯ0.5

2.2Ϯ0.6

2.3Ϯ0.7

35.7

28.2

26.0

23.2

29.6

20.9

0.22

0.33

0.24

0.33

0.20

0.24

0.21

0.32

0.23

0.32

0.20

0.24

In order to confirm the creation of free volume by the

trityl moieties on AuNPs, thermogravimetric analysis

(TGA) was performed to measure the numbers of rotors

per surface unit on the AuNPs. By comparison of the bulky

rotors with their linear analogues we wanted to assess

whether or not trityl groups were more efficient than single

phenyl groups for isolation of the rotator. The TGA results

are shown in Table 1. Values for NP1 and NP2 are not rep-

resented; these were discarded from our study because we

had not been able to obtain materials of satisfactory purity

(as discussed above and as shown by ¹⁹F NMR). We then

focused our analysis on NP3–NP8, which were much easier

to purify.

The organic loadings (or coverages) at the surfaces of

NP3–NP8 were calculated by the Equation (1):^[49]

where χ_organicis the mass fraction of alkanethiolate in the to create free volume in AuNP monolayers is efficient, as

cluster, R_Auis the crystallographic radius of a gold atom expected, but that solvent molecules are likely to be interca-

(0.145 nm), ρ_HCPis the number density of surface gold lated inside the monolayer. This assumption will be tested

atoms (13.89 atoms nm^–2, assuming hexagonal close pack- shortly by solid-state NMR and XPS spectroscopy.

3056

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Eur. J. Org. Chem. 2010, 3049–3067

Fluorine-Containing Molecular Rotors and Assembly on Gold Nanoparticles

perature. KIO₄(19.6 g, 85.2 mmol) was added, followed by NaCl

Conclusions

(9.96 g, 170 mmol) and I₂(10.8 g, 42.6 mmol). The mixture was

stirred overnight and diluted in water (1 L), and the acetic acid was

carefully neutralized with KOH in an ice-bath until pH 8–9 was

We report the synthesis of molecular rotors containing

fluorine atoms. Both trityl and linear derivatives of those

rotors were assembled on AuNPs by the Murray-modified reached. The mixture was washed three times with CH₂Cl₂and

the combined organic layers were washed with saturated aqueous

Na₂SO₃until the disappearance of the dark colouration. The or-

ganic phase was dried with Na₂SO₄and the solvent was removed

under reduced pressure. The crude product was purified by fil-

tration through silica gel with pure hexanes, followed by EtOAc/

hexanes (3%) as eluents to provide the title compound 9 (10.5 g,

Brust method. AuNPs with diameters of about 2 nm were

synthesized and TGA analysis showed that the footprints

of trityl-containing rotors are higher than those measured

for the linear analogues. This supports the idea that a more

sterically hindered stator should create more free volume in

the monolayer, thus increasing the chances of fast rotation

of the rotator. From these results, one can assume that

AuNPs represent a promising test-bed for kinetic studies on

surface-bound molecular rotors. This will be tested soon by

1

53% yield) as an orange solid. H NMR (CDCl₃): δ = 7.13 (d, J =

7.2 Hz, 2 H ar.), 3.76 (brs, NH₂) ppm. ¹³C NMR (CDCl₃): δ =

151.8 (dd, J = 243.4, J = 8.0 Hz, 2 C), 124.3 (t, J = 16.0 Hz), 120.3

(m*, 2 C), 74.3 (t, J = 9.9 Hz) ppm. ¹⁹F NMR (CDCl₃): δ = –131.2

study of these AuNPs by variable-temperature solid-state (d, J = 7.5 Hz) ppm. HRMS: calcd. for [C₆H₄F₂IN]*⁺254.9351

[M]*⁺; found 254.9355. (m*: The complex multiplicity of this signal

is attributed to coupling with fluorine).

¹⁹F NMR experiments.

Experimental Section

Compound 10: Compound 9 (4.85 g, 19.0 mmol) was dissolved in

Et₂O (60 mL) and the solution was cooled to –20 °C under argon,

after which BF₃·Et₂O (7.16 mL, 57.0 mmol) was added. The re-

sulting mixture was stirred for 20 min and tBuONO (4.51 mL,

38.0 mmol) was added. The resulting mixture was stirred for one

hour at –20 °C. A solution of Et₂NH (9.87 mL, 95.0 mmol) in ace-

tonitrile (24 mL) was then added and the temperature was raised

to room temperature for two hours. Water was added and the mix-

ture was extracted three times with CH₂Cl₂. The combined organic

layers were dried with Na₂SO₄and the solvents were removed un-

der reduced pressure to provide the crude triazene. Filtration on

silica gel with EtOAc/hexanes (2%) as eluent provide the triazene

compound, which was pure enough to use in the next step without

further purification. The triazene was dissolved in CH₃I (40 mL)

in a pressurized vessel and heated at 150 °C for 8 h. Note: Adequate

shielding is necessary to avoid risks of injuries! The crude compound

was next purified by flash chromatography on silica gel with

EtOAc/hexanes (0.5%) as eluent to provide the title compound

10(5.62 g, 81% yield over two steps from 7) as a white solid. ¹H

NMR (CDCl₃): δ = 7.23 (d, J = 7.0 Hz, 2 H ar.) ppm. ¹³C NMR

(CDCl₃): δ = 162.3 (d, J = 334.0, J = 7.5 Hz, 2 C), 121.0 (m*, 2

C), 92.2 (t, J = 12.7 Hz), 71.4 (t, J = 38.9 Hz) ppm. ¹⁹F NMR

(CDCl₃): δ = –91.3 (d, J = 5.4 Hz) ppm. HRMS: calcd. for

[C₆H₂F₂I₂]*⁺365.8208 [M]*⁺; found 365.8205. (m*: The complex

multiplicity of this signal is attributed to coupling with fluorine).

General Methods: Ethynylmagnesium bromide in THF (0.5 ) and

butyllithium in hexanes (2.5 ) were purchased from Sigma–Ald-

rich Co., Canada. Others chemical reagents were purchased from

Sigma–Aldrich Co., Canada, Alfa Aesar Co., TCI America Co. or

Oakwood Products Inc. and were used as received. Solvents used

for organic synthesis were obtained from Fisher Scientific (except

THF, from Sigma–Aldrich Co. Canada) and purified with a Sol-

vent Purifier System (SPS) (Vacuum Atmosphere Co., Hawthorne,

USA). Other solvents were obtained from Fisher Scientific and

were used as received. Tetrahydrofuran (THF) and triethylamine

(Et₃N) used for Sonogashira reactions were degassed 30 min prior

to use. All anhydrous and air-sensitive reactions were performed in

oven-dried glassware under positive argon pressure. Analytical

thin-layer chromatography was performed with pre-coated TLC

plates (silica gel 60 F₂₅₄, 0.25 mm, Silicycle, Québec, Canada).

Compounds were visualized with the aid of 254 nm and/or 365 nm

UV and/or aqueous sulfuric acid solution of ammonium heptamo-

lybdate tetrahydrate (10 g/100 mL H₂SO₄+ 900 mL H₂O). Prepar-

ative thin-layer chromatography was performed with pre-coated

TLC plates (silica gel 60 F₂₅₄, 1.00 mm, Silicycle, Québec, Canada).

Flash column chromatography was performed on silica gel (230–

400 mesh, R10030B, Silicycle, Québec, Canada). Nuclear magnetic

resonance (NMR) spectra were recorded with a Varian Inova

AS400 spectrometer (Varian, Palo Alto, USA) at 400 MHz (¹H),

376 MHz (¹⁹F) or 100 MHz (¹³C). Signals are reported as m (mul-

tiplet), s (singlet), d (doublet), dd (doublet of doublet), brs (broad

singlet) and ar (aromatic) and coupling constants are reported in

Hertz (Hz). The chemical shifts are reported in ppm (δ) relative to

residual solvent peak. High-resolution mass spectra (HRMS) were

recorded with an Agilent 6210 Time-of-Flight (TOF) LC-MS appa-

ratus with an ESI or APPI ion source (Agilent Technologies, To-

ronto, Canada). Thermogravimetric analysis (TGA) measurements

were performed with a Mettler-Toledo Model TGA SDTA 851e ap-

paratus (Mettler–Toledo, Schwerzenbach, Switzerland) from 50 °C

to 800 °C at a heating rate of 20 °Cmin^–1under nitrogen. TEM

observations were performed as follows: gold nanoparticles were

dissolved in toluene and 5 µL was deposited on a nickel grid reco-

vered with formvar. After drying, the grid was observed with a

JEOL JEM-1230 TEM (JEOL, Tokyo, Japan) at 80 kV. Diameters

of nanoparticles were calculated with the aid of ImageJ 1.41o soft-

ware.

Compound 11: Hex-5-yn-1-ol (1.77 mL, 16.4 mmol) and compound

10 (5.44 g, 14.9 mmol) were dissolved in THF (75 mL) at room

temperature under argon. Et₃N (8.30 mL, 59.5 mmol) was added,

followed by PdCl₂(PPh₃)₂(209 mg, 0.30 mmol) and CuI (57 mg,

0.30 mmol), and the resulting solution was stirred overnight. The

mixture was then diluted in CH₂Cl₂and washed with saturated

aqueous NH₄Cl, and the organic layer was dried with Na₂SO₄.

The solvents were removed under reduced pressure and the crude

product was purified by flash chromatography on silica gel with

EtOAc/hexanes (25%) as eluent to provide the title compound 11

(4.75 g, 95% yield) as a pale orange and gummy oil. ¹H NMR

(CDCl₃): δ = 6.87 (d, J = 6.7 Hz, 2 H ar.), 3.68 (t, J = 5.8 Hz,

CH₂–O), 2.87 (brs, OH), 2.43 (t, J = 6.4 Hz, CH₂–CϵC), 1.69 (m,

4 H alkyl) ppm. ¹³C NMR (CDCl₃): δ = 162.7 (dd, J = 246.6, J =

6.8 Hz, 2 C), 126.7 (t, J = 11.4 Hz), 114.3 (m*, 2 C), 93.6, 78.6 (t,

J = 3.7 Hz), 70.7 (t, J = 29.4 Hz), 62.0, 31.7, 24.7, 19.2 ppm. ¹⁹F

NMR (CDCl₃): δ = –93.0 (d, J = 6.7 Hz) ppm. HRMS: calcd. for

C₁₂H₁₂F₂IO 336.9901 [M + H]⁺; found 336.9893. (m*: The complex

multiplicity of this signal is attributed to coupling with fluorine).

Compound 9: 2,6-Difluoroaniline (8.34 mL, 77.5 mmol) was dis-

solved in a mixture of acetic acid/H₂O (230:25 mL) at room tem-

Eur. J. Org. Chem. 2010, 3049–3067

www.eurjoc.org

3057

D. Thibeault, M. Auger, J.-F. Morin

FULL PAPER

Compound 12: 4-Bromophenol (5.00 g, 28.9 mmol) and 1-bromo-

octane (8.37 g, 43.4 mmol) were dissolved in acetone (100 mL), fol-

lowed by addition of K₂CO₃(9.98 g, 72.3 mmol). The mixture was

stirred overnight at reflux, after which it was allowed to cool to

room temperature. The white precipitate was removed by filtration

and washed with acetone. The filtrate was then concentrated to

dryness under reduced pressure. The crude product was purified by

flash chromatography on silica gel with pure hexanes as eluent to

6 H ar.), 6.79 (d, J = 8.8 Hz, 6 H ar.), 3.92 (t, J = 6.5 Hz, 3ϫCH₂–

O), 2.64 (s, HCϵC), 1.78 (m, 6 H alkyl), 1.44 (m, 6 H alkyl), 1.29

(m, 24 H alkyl), 0.88 (t, J = 6.8 Hz, 3ϫCH₃) ppm. ¹³C NMR

(CDCl₃): δ = 157.7 (3ϫ), 137.3 (3ϫ), 130.0 (6ϫ), 113.7 (6ϫ), 90.

5, 72.6, 67.9 (3ϫ), 53.4, 31.8 (3ϫ), 29.4 (3ϫ), 29.3 (6ϫ), 26.1

(3ϫ), 22.7 (3ϫ), 14.1 (3ϫ) ppm. HRMS: calcd. for C₄₅H₆₅O₃

653.4928 [M + H]⁺; found 653.4932.

Compound 16: Compound 14 (3.83 g, 12.67 mmol) was dissolved

in acetyl chloride (115 mL) at room temperature under argon and

stirred overnight. The excess acetyl chloride was removed under

reduced pressure and the crude product was dried under high vac-

uum for two hours. The gummy oil was dissolved in toluene at

room temperature, ethynylmagnesium bromide (63.3 mmol) was

added under argon, and the solution was stirred overnight. Water

was then added and the mixture was extracted three times with

CH₂Cl₂. Combined organic layers were dried with Na₂SO₄and

concentrated under reduced pressure. The crude product was puri-

fied by flash chromatography on silica gel with CH₂Cl₂/hexanes

(2%) as eluent to provide the title compound 16(3.17 g, 81% yield)

as a pale yellow and sticky gum, which became a pale yellow solid

1

provide the title compound 12(7.61 g, 92% yield) as a clear oil. H

NMR (CDCl₃): δ = 7.32 (d, J = 8.7 Hz, 2 H ar.), 6.73 (d, J =

8.7 Hz, 2 H ar.), 3.86 (t, J = 6.5 Hz, CH₂–O), 1.74 (m, 2 H alkyl),

1.40 (m, 2 H alkyl), 1.29 (m, 8 H alkyl), 0.88 (t, J = 6.5 Hz, CH₃–

C) ppm. ¹³C NMR (CDCl₃): δ = 158.2, 132.1 (2ϫ), 116.2 (2ϫ),

112.5, 68.2, 31.8, 29.4, 29.3, 29.2, 26.0, 22.7, 14.1 ppm. HRMS:

calcd. for [C₁₄H₂₁BrO]*⁺284.0770 [M]*⁺; found 284.0768).

Compound 13: nBuLi (44.2 mmol) was added at –78 °C to a solu-

tion of compound 12 (12.0 g, 42.1 mmol) in THF (100 mL) and

the solution was stirred for 30 min. Diethylcarbonate (1.68 mL,

13.9 mmol) was added dropwise and the resulting mixture was al-

lowed to warm to room temperature and stirred for an additional

3 h. The solution was then diluted with water and extracted three

times with CH₂Cl₂. The combined organic layers were dried with

Na₂SO₄, and the solvents were removed under reduced pressure.

The crude product was purified by flash chromatography on silica

gel with EtOAc/hexanes (3%) as eluent to provide the title com-

1

after long-term vacuum. H NMR (CDCl₃): δ = 7.28 (m, 6 H ar.),

7.14 (m, 6 H ar.), 2.80 (s, HCϵC), 2.42 (s, 3ϫCH₃) ppm. ¹³C NMR

(CDCl₃): δ = 145.0 (3ϫ), 137.7 (3ϫ), 129.9 (3ϫ), 127.9 (3ϫ), 127.7

(3ϫ), 126.4 (3ϫ), 90.2, 73.4, 55.4, 21.7 (3ϫ) ppm. HRMS: calcd.

for C₂₄H₂₃311.1794 [M + H]⁺; found 311.1790).

1

pound 13 (6.13 g, 68% yield) as a clear oil. H NMR (CDCl₃): δ

Compound 17: nBuLi (8.13 mL, 19.5 mmol) was slowly added at

–78 °C to a solution of 3,5-di-tert-butylbromobenzene (5.00 g,

18.6 mmol) in THF (90 mL) and the solution was stirred for

30 min. Diethylcarbonate (0.72 mL, 5.94 mmol) was added drop-

wise and the resulting mixture was allowed to warm to room tem-

perature and stirred for an additional 3 h. The solution was then

diluted with water and extracted three times with CH₂Cl₂. The

combined organic layers were dried with Na₂SO₄and the solvents

were removed under reduced pressure. Filtration on silica gel with

EtOAc/hexanes (2%) as eluent provided the crude product (3.55 g),

which was used in the next step without further purification. The

crude product was then dissolved in acetyl chloride (90 mL) at

room temperature under argon and stirred for 4 h. The acetyl chlo-

ride was then removed under reduced pressure and the crude com-

pound was dried under high vacuum for two hours. The gummy

oil was dissolved in THF at room temperature, ethynylmagnesium

bromide (29.8 mmol) was added under argon, and the solution was

= 7.14 (d, J = 8.8 Hz, 6 H ar.), 6.80 (d, J = 8.8 Hz, 6 H ar.), 3.93

(t, J = 6.5 Hz, 3ϫCH₂–O), 2.70 (s, OH), 1.76 (m, 6 H alkyl), 1.44

(m, 6 H alkyl), 1.25 (m, 24 H alkyl), 0.88 (t, J = 6.7 Hz, 3ϫCH₃–

C) ppm. ¹³C NMR (CDCl₃): δ = 158.1 (3ϫ), 139.5 (3ϫ), 129.0

(6ϫ), 113.6 (6ϫ), 81.2, 67.9 (3ϫ), 31.8 (3ϫ), 29.4 (3ϫ), 29.3 (6ϫ),

26.1 (3ϫ), 22.7 (3ϫ), 14.1 (3ϫ) ppm. HRMS: calcd. for C₄₃H₆₃O₃

627.4772 [M – OH]⁺; found 627.4789.

Compound 14: nBuLi (71.59 mmol) was added at –78 °C to a solu-

tion of 3-bromotoluene (11.66 g, 68.18 mmol) in THF (120 mL)

and the solution was stirred for 30 min. Diethylcarbonate (2.75 mL,

22.73 mmol) was added dropwise and the resulting mixture was

allowed to warm to room temperature and stirred for an additional

3 h. The solution was then diluted with water and extracted three

times with CH₂Cl₂. The combined organic layers were dried with

Na₂SO₄, and the solvents were removed under reduced pressure.

The crude product was purified by flash chromatography on silica

gel with EtOAc/hexanes (1%to 2%) as eluents to provide the title stirred overnight. Water was then added and the mixture was ex-

compound 14 (6.42 g, 93% yield) as a clear and gummy oil. ¹H

tracted three times with CH₂Cl₂. Combined organic layers were

NMR (CDCl₃): δ = 7.36, (m, 6 H ar.), 7.23 (m, 6 H ar.), 2.47 (s, dried with Na₂SO₄and the solvents were removed under reduced

3ϫCH₃) ppm. ¹³C NMR (CDCl₃): δ = 147.1 (3ϫ), 137.4 (3ϫ), pressure. The crude product was purified by flash chromatography

128.5 (3ϫ), 127.9 (3ϫ), 127.7 (3ϫ), 125.3 (3ϫ), 82.0, 21.6

(3ϫ) ppm. HRMS: calcd. for C₂₂H₂₀285.1643 [M – OH]*⁺; found

285.1647.

on silica gel with pure hexanes in order to remove impurities, fol-

lowed by EtOAc/hexanes (1%) as eluents to provide the title com-

pound 17 (2.18 g, 61% yield) as a white solid. H NMR (CDCl₃):

1

δ = 7.25 (s, 3 H ar.), 7.00 (s, 6 H ar.), 2.61 (s, HCϵC), 1.20 (brs,

18ϫCH₃) ppm. ¹³C NMR (CDCl₃): δ = 149.6 (6ϫ), 144.6 (3ϫ),

123.8 (6ϫ), 119.8 (3ϫ), 90.7, 71.6, 34.8 (3ϫ), 31.5 (18ϫ) ppm.

HRMS: calcd. for C₄₅H₆₅605.5081 [M + H]⁺; found 605.5076.

Compound 15: Compound 13 (6.04 g, 9.36 mmol) was dissolved in

acetyl chloride (100 mL) at room temperature under argon and

stirred overnight. The excess acetyl chloride was removed under

reduced pressure and the crude product was dried under high vac-

uum for two hours. The gummy oil was dissolved in toluene at

room temperature, ethynylmagnesium bromide (28.1 mmol) was

added under argon, and the solution was stirred overnight. Water

was added and the mixture was extracted three times with CH₂Cl₂.

Combined organic layers were dried with Na₂SO₄and concentrated

under reduced pressure. The crude product was purified by flash

chromatography on silica gel with EtOAc/petroleum ether (1%) as

Compound 18: Compound 10 (108 mg, 0.29 mmol) and compound

15 (160 mg, 0.25 mmol) were dissolved in THF (1.5 mL) and Et₃N

(137 µL, 0.98 mmol) was added, followed by PdCl₂(PPh₃)₂(3 mg,

0.005 mmol) and CuI (1 mg, 0.005 mmol). The resulting solution

was stirred at room temperature overnight under argon. The mix-

ture was then diluted in CH₂Cl₂and washed with saturated aque-

ous NH₄Cl, and the organic layer was dried with Na₂SO₄. The

eluent to provide the title compound 15(5.80 g, 95% yield) as a solvents were removed under reduced pressure and the crude prod-

yellow and gummy oil. ¹H NMR (CDCl₃): δ = 7.14 (d, J = 8.8 Hz,

uct was purified by preparative TLC on silica gel with EtOAc/hex-

3058

www.eurjoc.org

Eur. J. Org. Chem. 2010, 3049–3067

Fluorine-Containing Molecular Rotors and Assembly on Gold Nanoparticles

anes (1%) as eluent to provide the title compound 18 (171 mg, 78%

resulting mixture was stirred overnight at 50 °C. A saturated solu-

yield) as a pale yellow oil. ¹H NMR (CDCl₃): δ = 7.14 (d, J = tion of I₂in CH₂Cl₂was added to this solution until persistence of

8.8 Hz, 6 H ar.), 6.98 (d, J = 6.5 Hz, 2ϫHC–CF), 6.81 (d, J =

the brown colouration. The mixture was stirred for 15 min, diluted

8.8 Hz, 6 H ar.), 3.93 (t, J = 6.5 Hz, 3ϫCH₂–O), 1.77 (m, 6 H in CH₂Cl₂and washed with saturated aqueous Na₂S₂O₃until the

alkyl), 1.44 (m, 6 H alkyl), 1.29 (m, 24 H alkyl), 0.88 (t, J = 6.7 Hz,

3ϫCH₃) ppm. ¹³C NMR (CDCl₃): δ = 162.3 (dd, J = 245.7, J =

6.9 Hz, 2 C), 158.0 (3ϫ), 137.1 (3ϫ), 130.0 (6ϫ), 126.5 (t, J =

disappearance of the brown colouration. The organic layer was

dried with Na₂SO₄and the solvents were removed under reduced

pressure. The crude product was purified by preparative TLC on

11.4 Hz), 114.4 (m*, 2 C), 113.9 (6ϫ), 99.7, 81.8 (t, J = 3.5 Hz), silica gel with EtOAc͞hexanes (4%) as eluent to provide the title

71.0 (t, J = 29.4 Hz), 68.0 (3ϫ), 54.1, 31.8 (3ϫ), 29.4 (3ϫ), 29.3

(6ϫ), 26.1 (3ϫ), 22.7 (3ϫ), 114.1 (3ϫ) ppm. ¹⁹F NMR (CDCl₃):

δ = –92.9 (d, J = 6.6 Hz) ppm. HRMS: calcd. for C₅₁H₆₆F₂IO₃

891.4019 [M + H]⁺; found 891.4000. (m*: The complex multiplicity

of this signal is attributed to coupling with fluorine).

compound 1 (240 mg, 80% yield) as a yellow oil. ¹H NMR

(CDCl₃): δ = 7.14 (d, J = 8.7 Hz, 12 H ar.), 7.00 (d, J = 7.3 Hz,

4ϫHC–CF), 6.81 (d, J = 8.7 Hz, 12 H ar.), 3.93 (s, 2ϫCH₂–S),

3.93 (t, J = 6.5 Hz, 6ϫCH₂–O), 1.76 (m, 12 H alkyl), 1.44 (m, 12

H alkyl), 1.29 (m, 48 H alkyl), 0.88 (t, J = 6.6 Hz, 6ϫCH₃) ppm.

¹³C NMR (CDCl₃): δ = 162.8 (dd, J = 251.8, J = 6.9 Hz, 4 C),

158.0 (6ϫ), 137.1 (6ϫ), 129.9 (12ϫ), 125.5 (t, J = 11.8 Hz, 2 C),

114.4 (m*, 4 C), 113.8 (12ϫ), 101.8 (t, J = 19.8 Hz, 2 C), 100.5

(2ϫ), 96.5 (t, J = 3.1 Hz, 2 C), 82.2 (t, J = 3.5 Hz, 2 C), 71.4 (2ϫ),

67.9 (6ϫ), 54.1 (2ϫ), 31.8 (6ϫ), 29.4 (6ϫ), 29.3 (6ϫ), 29.2 (6ϫ),

28.9 (2ϫ), 26.1 (6ϫ), 22.7 (6ϫ), 14.1 (6ϫ) ppm. ¹⁹F NMR

(CDCl₃): δ = –108.3 (d, J = 7.3 Hz) ppm. HRMS: calcd. for

C₁₀₈H₁₃₅F₄O₆S₂1667.9636 [M + H]⁺; found 1667.9642. (m*: The

complex multiplicity of this signal is attributed to coupling with fluor-

ine).

Compound 19: Compound 18 (1.64 g, 1.84 mmol) was dissolved in

THF (10 mL) and Et₃N (1.03 mL, 7.36 mmol) was added, followed

by PdCl₂(PPh₃)₂(26 mg, 0.04 mmol), CuI (7 mg, 0.04 mmol) and

propargyl alcohol (0.16 mL, 2.76 mmol). The resulting solution

was stirred overnight at 60 °C under argon. After the reaction mix-

ture had been allowed to cool to room temperature, it was diluted

in CH₂Cl₂and washed with saturated aqueous NH₄Cl, and the

organic layer was dried with Na₂SO₄. The solvents were removed

under reduced pressure and the crude product was purified by flash

chromatography on silica gel with EtOAc/hexanes (20%) as eluent

to provide the title compound 19 (1.04 g, 69% yield) as a clear oil.

¹H NMR (CDCl₃): δ = 7.15 (d, J = 8.7 Hz, 6 H ar.), 6.99 (d, J =

7.2 Hz, 2ϫHC–CF), 6.81 (d, J = 8.7 Hz, 6 H ar.), 4.49 (s, CϵC–

CH₂–O), 3.92 (t, J = 6.4 Hz, 3ϫCH₂–O), 2.59 (brs, OH), 1.75 (m,

6 H alkyl), 1.43 (m, 6 H alkyl), 1.28 (m, 24 H alkyl), 0.88 (t, J =

6.5 Hz, 3ϫCH₃) ppm. ¹³C NMR (CDCl₃): δ = 162.7 (dd, J =

253.3, 6.9 Hz, 2 C), 157.9 (3ϫ), 137.1 (3ϫ), 129.9 (6ϫ), 125.6 (t,

J = 12.2 Hz), 114.3 (m*, 2 C), 113.8 (6ϫ), 101.6 (t, J = 19.1 Hz),

100.5, 98.7 (t, J = 3.1 Hz), 82.2 (t, J = 3.8 Hz), 72.2, 67.9 (3ϫ),

54.1, 51.4, 31.8 (3ϫ), 29.3 (3ϫ), 29.2 (6ϫ), 26.0 (3ϫ), 22.6 (3ϫ),

Compound 21: Compound 12 (3.00 g, 10.5 mmol) was dissolved in

THF (30 mL) at room temperature under argon. Et₃N (4.26 mL,

42.1 mmol) was added, followed by PdCl₂(PhCN)₂(121 mg,

0.32 mmol), CuI (40 mg, 0.21 mmol), P(tBu)₃(0.63 mmol) and

TMSA (2.91 mL, 21.0 mmol). The resulting solution was stirred

overnight. The mixture was then diluted in CH₂Cl₂and washed

with saturated aqueous NH₄Cl, and the organic layers were dried

with Na₂SO₄. The solvent was removed under reduced pressure.

The crude product was purified by flash chromatography on silica

gel with hexanes to EtOAc/hexanes (1%) as eluents to provide the

title compound 21 (3.07 g, 96% yield) as a deep orange oil. ¹H

NMR (CDCl₃): δ = 7.38 (d, J = 8.7 Hz, 2 H ar.), 6.79 (d, J =

8.7 Hz, 2 H ar.), 3.93 (t, J = 6.6 Hz, CH₂–O), 1.76 (m, 2 H alkyl),

1.44 (m, 2 H alkyl), 1.29 (m, 8 H alkyl), 0.89 (t, J = 6.7 Hz, CH₃),

0.23 (s, TMS-C) ppm. ¹³C NMR (CDCl₃): δ = 159.3, 133.4 (2ϫ),

115.0, 114.3 (2ϫ), 105.3, 92.2, 68.0, 31.8, 29.4, 29.2 (2ϫ), 26.0,

22.7, 14.1 ppm. HRMS: calcd. for C₁₉H₃₁OSi 303.2144 [M + H]⁺;

found 303.2143.

14.1 (3ϫ) ppm. ¹⁹F NMR (CDCl₃):

δ = –108.2 (d, J =

7.2 Hz) ppm. HRMS: calcd. for C₅₄H₆₉F₂O₄819.5158 [M + H]⁺;

found 819.5150. (m*: The complex multiplicity of this signal is at-

tributed to coupling with fluorine).

Compound 20: A solution of PPh₃(1.00 g, 3.81 mmol) and DIAD

(0.64 mL, 3.81 mmol) in THF (12 mL) was stirred at 0 °C for

30 min. A solution of compound 19 (1.04 g, 1.27 mmol) and thio-

acetic acid (0.27 mL, 3.81 mmol) in THF (8 mL) was added to this

solution and the mixture was allowed to warm to room tempera-

ture and stirred for 3 h. After addition of water, the mixture was

extracted three times with CH₂Cl₂and the organic layers were dried

with Na₂SO₄. The solvents were removed under reduced pressure

to provide the crude thioacetate. Purification by preparative TLC

on silica gel with EtOAc/hexanes (2%) as eluent afforded the title

compound 20(730 mg, 66% yield) as a pale yellow oil. ¹H NMR

(CDCl₃): δ = 7.14 (d, J = 8.5 Hz, 6 H ar.), 6.98 (d, J = 7.2 Hz,

2ϫHC–CF), 6.81 (d, J = 8.5 Hz, 6 H ar.), 3.94 (s, CH₂–S), 3.93

(t, J = 6.8 Hz, 3ϫCH₂–O), 2.37 (s, CH₃–C=O), 1.75 (m, 6 H alkyl),

1.44 (m, 6 H alkyl), 1.28 (m, 24 H alkyl), 0.88 (m, 3ϫCH₃) ppm.

¹³C NMR (CDCl₃): δ = 193.6, 162.8 (d, J = 251.8, J = 6.9 Hz, 2

C), 158.0 (3ϫ), 137.1 (3ϫ), 129.9 (6ϫ), 125.4 (t, J = 11.8 Hz),

114.3 (m*, 2 C), 113.9 (6ϫ), 101.8 (t, J = 19.8 Hz), 100.5, 95.6 (t,

J = 3.1 Hz), 82.2 (t, J = 3.8 Hz), 69.7, 68.0 (3ϫ), 54.1, 31.8 (3ϫ),

30.1, 29.4 (3ϫ), 29.3 (6ϫ), 26.1 (3ϫ), 22.7 (3ϫ), 18.6, 14.1

(3ϫ) ppm. ¹⁹F NMR (CDCl₃): δ = –108.4 (d, J = 7.2 Hz) ppm.

HRMS: calcd. for C₅₆H₇₁F₂O₄S 877.5036 [M + H]⁺; found

877.5032. (m*: The complex multiplicity of this signal is attributed

to coupling with fluorine).

Compound 22: Compound 21 (1.44 g, 4.76 mmol) was dissolved in

a THF/MeOH/H₂O mixture (10:10:2 mL) at room temperature.

KOH (1.60 g, 28.6 mmol) was then added and the resulting solu-

tion was stirred for 4 h, after which additional water was added.

The mixture was extracted three times with CH₂Cl₂. The combined

organic layers were dried with Na₂SO₄and solvents were removed

under reduced pressure. The crude product was purified by flash

chromatography on silica gel with EtOAc/hexanes (1%) as eluent

to provide the title compound 22 (1.08 g, 99% yield) as an orange

1

oil. H NMR (CDCl₃): δ = 7.41 (d, J = 8.7 Hz, 2 H ar.), 6.82 (d,

J = 8.7 Hz, 2 H ar.), 3.93 (t, J = 6.6 Hz, CH₂–O), 2.98 (s, HCϵC),

1.77 (m, 2 H alkyl), 1.43 (m, 2 H alkyl), 1.30 (m, 8 H alkyl), 0.88

(t, J = 6.7 Hz, CH₃) ppm. ¹³C NMR (CDCl₃): δ = 159.5, 133.5

(2ϫ), 114.4 (2ϫ), 113.8, 83.8, 75.6, 68.0, 31.8, 29.3, 29.2 (2ϫ),

26.0, 22.7, 14.1 ppm. HRMS: calcd. for C₁₆H₂₃O 231.1749 [M +

H]⁺; found 231.1741.

Compound 23: Compound 10 (2.41 g, 6.59 mmol) and compound

22 (1.38 g, 5.99 mmol) were dissolved in THF (15 mL) and Et₃N

(3.34 mL, 24.0 mmol) was added, followed by PdCl₂(PPh₃)₂

(84 mg, 0.12 mmol) and CuI (23 mg, 0.12 mmol). The resulting

solution was stirred overnight at room temperature. The mixture

Compound 1: Compound 20 (314 mg, 0.36 mmol) was dissolved in

a solution of HCl/MeOH (1 , 6 mL) with THF (6 mL) and the

Eur. J. Org. Chem. 2010, 3049–3067

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3059

D. Thibeault, M. Auger, J.-F. Morin

FULL PAPER

was then diluted in CH₂Cl₂and washed with saturated aqueous

NH₄Cl, and the organic layer was dried with Na₂SO₄. The solvents

were removed under reduced pressure. The crude product was puri-

fied by flash chromatography on silica gel with CH₂Cl₂/hexanes

(5%) as eluent to provide the title compound 23 (2.25 g, 80% yield)

ganic layer was dried with Na₂SO₄. The solvents were removed

under reduced pressure and the crude compound was purified by

flash chromatography on silica gel with EtOAc/hexanes (2%) as

eluent to provide the thioacetate 26 (1.55 g, 96% yield) as an

1

orange solid. H NMR (CDCl₃): δ = 7.40 (d, J = 8.4 Hz, 2 H ar.),

1

as a yellow solid. H NMR (CDCl₃): δ = 7.37 (d, J = 8.6 Hz, 2 H

6.95 (d, J = 7.4 Hz, 2ϫHC–CF), 6.83 (d, J = 8.4 Hz, 2 H ar.), 3.94

(s, CH₂–S), 3.90 (t, J = 6.4 Hz, CH₂–O), 2.35 (s, CH₃–C=O), 1.75

(m, 2 H alkyl), 1.42 (m, 2 H alkyl), 1.28 (m, 8 H alkyl), 0.88 (t, J

ar.), 6.90 (d, J = 6.7 Hz, 2ϫHC–CF), 6.78 (d, J = 8.6 Hz, 2 H ar.),

3.85 (t, J = 6.5 Hz, CH₂–O), 1.73 (m, 2 H alkyl), 1.39 (m, 2 H

alkyl), 1.27 (m, 8 H alkyl), 0.88 (t, J = 6.6 Hz, CH₃) ppm. ¹³C = 6.5 Hz, CH₃) ppm. ¹³C NMR (CDCl₃): δ = 193.5, 162.8 (dd, J

NMR (CDCl₃): δ = 163.1 (dd, J = 247.1, J = 7.1 Hz, 2 C), 159.8,

= 253.5, J = 6.7 Hz, 2 C), 159.9, 133.3 (2ϫ), 125.5 (t, J = 11.9 Hz),

133.2 (2ϫ), 126.5 (t, J = 11.5 Hz), 114.5 (2ϫ), 113.9 (m*, 2 C), 114.7 (2ϫ), 114.0 (m*, 2 C), 113.8, 101.6 (t, J = 20.0 Hz), 95.7 (t,

113.7, 92.9, 85.5 (t, J = 3.8 Hz), 70.8 (t, J = 29.4 Hz), 68.0, 31.9,

29.4, 29.3, 29.2, 26.1, 22.7, 14.2 ppm. ¹⁹F NMR (CDCl₃): δ = –92.5

(d, J = 6.2 Hz) ppm. HRMS: calcd. for [C₂₂H₂₃OF₂I]*⁺468.0756

[M]*⁺; found 468.0754. (m*: The complex multiplicity of this signal

is attributed to coupling with fluorine).

J = 2.8 Hz), 93.6, 86.0 (t, J = 3.7 Hz), 69.8, 68.1, 31.9, 30.0, 29.4,

29.3, 29.2, 26.1, 22.7, 18.7, 14.1 ppm. ¹⁹F NMR (CDCl₃):

δ

=

–108.3 (d,

J

=

7.1 Hz) ppm. HRMS: calcd. for

[C₂₇H₂₈O₂SF₂]*⁺455.1855 [M]*⁺; found 455.1851. (m*: The com-

plex multiplicity of this signal is attributed to coupling with fluorine).

Compound 2: Compound 26 (1.48 g, 3.26 mmol) was dissolved in a

solution of HCl/MeOH (1 , 10 mL) with THF (10 mL) and stirred

overnight at 50 °C. A saturated solution of I₂in CH₂Cl₂was added

to this solution until persistence of a brown colouration. The mix-

ture was stirred for 15 min, diluted in CH₂Cl₂and washed with

saturated aqueous Na₂S₂O₃until the disappearance of the brown

colour. The organic layer was dried with Na₂SO₄and the solvents

were removed under reduced pressure. The crude product was puri-

fied by flash chromatography on silica gel with CH₂Cl₂͞hexanes

(20%) as eluent to provide the title compound 2 (727 mg, 54%

yield) as a yellow solid, together with the corresponding thiol

Compound 24: Compound 23 (2.20 g, 4.69 mmol) was dissolved in

THF (15 mL) and Et₃N (2.61 mL, 18.7 mmol) was added, followed

by PdCl₂(PPh₃)₂(132 mg, 0.19 mmol), CuI (18 mg, 0.09 mmol) and

propargyl alcohol (0.55 mL, 9.37 mmol). The resulting solution

was stirred overnight at 60 °C for 2 d. The mixture was then diluted

in CH₂Cl₂and washed with saturated aqueous NH₄Cl, and the

organic layer was dried with Na₂SO₄. The solvents were removed

under reduced pressure. The crude product was purified by flash

chromatography on silica gel with CH₂Cl₂in hexanes (50% to

60%) as eluents to provide the title compound 24 (1.69 g, 91%

1

yield) as a white solid. H NMR (CDCl₃): δ = 7.41 (d, J = 8.8 Hz,

1

(253 mg, 19% yield). H NMR (CDCl₃): δ = 7.41 (d, J = 8.6 Hz,

2 H ar.), 6.99 (d, J = 7.3 Hz, 2ϫHC–CF), 6.85 (d, J = 8.8 Hz, 2

H ar.), 4.56 (d, J = 5.7 Hz, CϵC–CH₂–O), 3.94 (t, J = 6.5 Hz,

CH₂–O), 2.39 (m, OH), 1.77 (m, 2 H alkyl), 1.44 (m, 2 H alkyl),

1.29 (m, 8 H alkyl), 0.89 (t, J = 6.6 Hz, CH₃) ppm. ¹³C NMR

(CDCl₃): δ = 162.7 (dd, J = 253.4, J = 6.7 Hz, 2 C), 159.9, 133.3

(2ϫ), 125.7 (t, J = 11.9 Hz), 114.7 (2ϫ), 114.1 (m*, 2 C), 113.8,

101.4 (t, J = 20.0 Hz), 98.6 (t, J = 3.1 Hz), 93.6, 85.9 (t, J = 3.8 Hz),

72.6, 68.2, 51.6, 31.8, 29.4, 29.3, 29.2, 26.0, 22.7, 14.1 ppm. ¹⁹F

NMR (CDCl₃): δ = –108.4 (d, J = 7.6 Hz) ppm. HRMS: calcd. for

C₂₅H₂₇F₂O₂397.1974 [M + H]⁺; found 397.1979. (m*: The complex

multiplicity of this signal is attributed to coupling with fluorine).

4 H ar.), 6.98 (d, J = 7.3 Hz, 4ϫHC–CF), 6.84 (d, J = 8.6 Hz, 4

H ar.), 3.92 (m, 2ϫCH₂–S and 2ϫCH₂–O), 1.76 (m, 4 H alkyl),

1.43 (m, 4 H alkyl), 1.29 (m, 16 H alkyl), 0.89 (t, J = 6.4 Hz,

2ϫCH₃) ppm. ¹³C NMR (CDCl₃): δ = 162.8 (dd, J = 246.7, J =

6.7 Hz, 4 C), 159.9 (2ϫ), 133.3 (4ϫ), 125.5 (t, J = 11.9 Hz, 2 C),

114.6 (4ϫ), 114.0 (m*, 4 C), 113.8 (2ϫ), 101.7 (t, J = 20.0 Hz, 2

C), 96.5 (t, J = 2.9 Hz, 2 C), 93.5 (2ϫ), 86.0 (t, J = 3.6 Hz, 2 C),

71.5 (2ϫ), 68.1 (2ϫ), 31.8 (2ϫ), 29.4 (2ϫ), 29.3 (2ϫ), 29.2 (2ϫ),

29.0 (2ϫ), 26.0 (2ϫ), 22.7 (2ϫ), 14.1 (2ϫ) ppm. ¹⁹F NMR

(CDCl₃): δ = –108.2 (d, J = 7.2 Hz) ppm. HRMS: calcd. for

C₅₀H₅₁O₂S₂F₄823.3261 [M + H]⁺; found 823.3250. (m*: The com-

plex multiplicity of this signal is attributed to coupling with fluorine).

Compound 25: CBr₄(3.47 g, 10.5 mmol) and PPh₃(2.75 g,

10.5 mmol) were added at room temperature to a solution of the

compound 24 (1.66 g, 4.19 mmol) in THF (25 mL) and the re-

sulting mixture was stirred for 30 min. The solution was then di-

luted in CH₂Cl₂and washed with water, and the organic layer was

dried with Na₂SO₄. The solvents were removed under reduced pres-

sure and the crude product was filtered through silica gel with

EtOAc/hexanes (2%)as eluent to provide the title compound 25

Compound 27: Compound 11 (750 mg, 2.23 mmol) and compound

15 (1.73 g, 2.68 mmol) were dissolved in THF (8 mL) and Et₃N

(1.24 mL, 8.93 mmol) was added, followed by PdCl₂(PPh₃)₂

(63 mg, 0.09 mmol) and CuI (17 mg, 0.09 mmol). The resulting

solution was stirred at 60 °C under argon for 2 d. Propargyl alcohol

(1 mL) was then added (to remove the unreacted compound 11)

and the mixture was stirred for another day at 60 °C. The mixture

was then diluted in CH₂Cl₂and washed with saturated aqueous

NH₄Cl, and the organic layer was dried with Na₂SO₄. The solvents

were removed under reduced pressure. The crude product was puri-

fied by flash chromatography on silica gel with EtOAc/hexanes

(20%)as eluent to provide the title compound 27 (1.75 g, 91%

yield) as a pale yellow oil. ¹H NMR (CDCl₃): δ = 7.22 (d, J =

8.7 Hz, 6 H ar.), 6.89 (d, J = 7.2 Hz, 2ϫHC–CF), 6.80 (d, J =

8.7 Hz, 6 H ar.), 3.90 (t, J = 6.4 Hz, 3ϫCH₂–O), 3.62 (t, J =

6.0 Hz, CH₂–O), 2.39 (t, J = 6.4 Hz, CϵC–CH₂), 2.13 (s, OH), 1.74

(m, 6 H alkyl), 1.65 (m, 4 H alkyl), 1.43 (m, 6 H alkyl), 1.28 (m,

26 H alkyl), 0.87 (t, J = 6.5 Hz, 3ϫCH₃) ppm. ¹³C NMR (CDCl₃):

δ = 162.8 (dd, J = 252.9, J = 7.0 Hz, 2 C), 157.9 (3ϫ), 137.2 (3ϫ),

130.0 (6ϫ), 125.1 (t, J = 11.8 Hz), 114.2 (m*, 2 C), 113.8 (6ϫ),

107.8 (t, J = 3.1 Hz), 102.5 (t, J = 19.8 Hz), 93.6, 79.1 (t, J =

3.5 Hz), 71.7, 67.9 (3ϫ), 62.1, 54.7, 31.9 (3ϫ), 31.8, 29.4 (3ϫ),

29.3 (6ϫ), 26.1 (3ϫ), 25.3, 22.7 (3ϫ), 19.2, 14.1 (3ϫ) ppm. ¹⁹F

1

(1.77 g, 92% yield) as a yellow solid. H NMR (CDCl₃): δ = 7.43

(d, J = 8.7 Hz, 2 H ar.), 7.01 (d, J = 7.4 Hz, 2ϫHC–CF), 6.86 (d,

J = 8.7 Hz, 2 H ar.), 4.19 (s, CH₂–Br), 3.95 (t, J = 6.5 Hz, CH₂–

O), 1.78 (m, 2 H alkyl), 1.44 (m, 2 H alkyl), 1.31 (m, 8 H alkyl),

0.89 (t, J = 6.5 Hz, CH₃) ppm. ¹³C NMR (CDCl₃): δ = 162.8 (dd,

J = 253.8, J = 6.8 Hz, 2 C), 160.0, 133.4 (2ϫ), 126.2 (t, J =

12.1 Hz), 114.7 (2ϫ), 114.1 (m*, 2 C), 133.7, 101.1 (t, J = 19.9 Hz),

95.1 (t, J = 3.0 Hz), 93.9, 85.9 (t, J = 3.8 Hz), 73.6, 68.1, 31.8, 29.4,

29.2 (2ϫ), 26.0, 22.7, 14.3, 14.1 ppm. ¹⁹F NMR (CDCl₃):

δ

=

–107.9 (d,

J

=

7.0 Hz) ppm. HRMS: calcd. for

[C₂₅H₂₅OBrF₂]*⁺458.1051 [M]*⁺; found 458.1049. (m*: The com-

plex multiplicity of this signal is attributed to coupling with fluorine).

Compound 26: Compound 25 (1.63 g, 3.55 mmol) and potassium

thioacetate (811 mg, 7.10 mmol) were dissolved in THF (14 mL)

and the resulting mixture was heated at 60 °C overnight. The mix-

ture was then diluted in CH₂Cl₂and washed with water. The or-

3060

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Eur. J. Org. Chem. 2010, 3049–3067

Fluorine-Containing Molecular Rotors and Assembly on Gold Nanoparticles

NMR (CDCl₃): δ = –108.3 (d, J = 7.2 Hz) ppm. HRMS: calcd. for

C₅₇H₇₅F₂O₄861.5633 [M + H]⁺; found 861.5628. (m*: The complex

multiplicity of this signal is attributed to coupling with fluorine).

0.87 (t, J = 6.4 Hz, 3ϫCH₃) ppm. ¹³C NMR (CDCl₃): δ = 162.9

(dd, J = 252.6, J = 6.8 Hz, 2 C), 157.9 (3ϫ), 137.2 (3ϫ), 130.0

(6ϫ), 124.8 (t, J = 11.4 Hz), 114.3 (m*, 2 C), 113.8 (6ϫ), 107.8 (t,

J = 3.1 Hz), 102.6 (t, J = 19.8 Hz), 93.2, 79.4 (t, J = 3.8 Hz), 71.6,

67.9 (3ϫ), 54.7, 32.9, 31.8 (3ϫ), 31.7, 29.4 (3ϫ), 29.3 (6ϫ), 26.8,

26.1 (3ϫ), 22.7 (3ϫ), 18.6, 14.1 (3ϫ) ppm. ¹⁹F NMR (CDCl₃): δ

= –108.2 (d, J = 7.1 Hz) ppm. HRMS: calcd. for C₅₇H₇₄BrF₂O₃

923.4784 [M + H]⁺; found 923.4797. (m*: The complex multiplicity

of this signal is attributed to coupling with fluorine).

Compound 28: Compound 11 (300 mg, 0.89 mmol) and compound

16 (416 mg, 1.34 mmol) were dissolved in THF (3 mL) and Et₃N

(0.50 mL, 3.57 mmol) was added, followed by PdCl₂(PPh₃)₂

(25 mg, 0.04 mmol) and CuI (7 mg, 0.04 mmol). The resulting solu-

tion was stirred at 60 °C under argon for 2 d. Propargyl alcohol (1

mL) was then added (to remove the unreacted compound 11) and

the mixture was stirred for another day at 60 °C. The mixture was

then diluted in CH₂Cl₂and washed with saturated aqueous NH₄Cl,

and the organic layer was dried with Na₂SO₄. The solvents were

removed under reduced pressure and the crude product was puri-

fied by flash chromatography on silica gel with CH₂Cl₂/hexanes

(60%) as eluent to provide the title compound 28 (457 mg, 99%

Compound 31: CBr₄(711 mg, 2.15 mmol) and PPh₃(563 mg,

2.15 mmol) were added at room temperature to a solution of the

compound 28 (445 mg, 0.86 mmol) in THF (4 mL) and the re-

sulting mixture was stirred for 30 min. The solution was then di-

luted with CH₂Cl₂and washed with water, and the organic layer

was dried with Na₂SO₄. The solvents were removed under reduced

pressure and the crude product was filtered through silica gel with

1

yield) as a pale yellow oil. H NMR (CDCl₃): δ = 7.27 (brs, 3 H

ar.), 7.15 (m, 3 H ar.), 7.04 (m, 6 H ar.), 6.90 (d, J = 7.2 Hz, EtOAc/hexanes (4%) as eluent to provide the title compound 31

1

2ϫHC–CF), 3.61 (t, J = 5.8 Hz, CH₂–O), 2.39 (t, J = 6.4 Hz,

(486 mg, 97% yield) as a yellow oil. H NMR (CDCl₃): δ = 7.26

CϵC–CH₂), 2.28 (s, 3ϫCH₃), 1.64 (m,4 H alkyl) ppm. ¹³C NMR (brs, 3 H ar.), 7.16 (m, 3 H ar.), 7.05 (m, 6 H ar.), 6.90 (d, J =

(CDCl₃): δ = 162.9 (dd, J = 252.9, J = 7.2 Hz, 2 C), 144.7 (3ϫ), 7.2 Hz, 2ϫHC–CF), 3.37 (t, J = 6.6 Hz, CH₂–Br), 2.38 (t, J =

137.6 (3ϫ), 129.9 (3ϫ), 127.8 (3ϫ), 127.7 (3ϫ), 126.3 (3ϫ), 125.1

7.0 Hz, CϵC–CH₂), 2.28 (s, 3ϫCH₃), 1.94 (m, 2 H alkyl), 1.69 (m,

(t, J = 11.7 Hz), 114.3 (m*, 2 C), 107.4 (t, J = 3.1 Hz), 102.5 (t, J 2 H alkyl) ppm. ¹³C NMR (CDCl₃): δ = 162.9 (dd, J = 252.5, J =

= 20.2 Hz), 94.0, 79.1 (t, J = 3.6 Hz), 72.3, 62.1, 56.5, 31.7, 24.7, 7.0 Hz, 2 C), 144.6 (3ϫ), 137.6 (3ϫ), 129.9 (3ϫ), 127.8 (3ϫ), 127.7

21.5 (3ϫ), 19.2 ppm. ¹⁹F NMR (CDCl₃): δ = –108.1 (d, J =

(3ϫ), 126.3 (3ϫ), 124.9 (t, J = 11.9 Hz), 114.3 (m*, 2 C), 107.4 (t,

7.6 Hz) ppm. HRMS: calcd. for C₃₆H₃₃F₂O 519.2494 [M + H]⁺; J = 3.1 Hz), 102.6 (t, J = 20.2 Hz), 93.3, 79.3 (t, J = 3.7 Hz), 72.2,

found 519.2487. (m*: The complex multiplicity of this signal is at-

tributed to coupling with fluorine).

56.5, 32.9, 31.7, 26.7, 21.5 (3ϫ), 18.6 ppm. ¹⁹F NMR (CDCl₃): δ

= –108.0 (d, J = 7.2 Hz) ppm. HRMS: calcd. for [C₃₆H₃₁BrF₂]*⁺

580.1572 [M]*⁺; found 580.1561. (m*: The complex multiplicity of

this signal is attributed to coupling with fluorine).

Compound 29: Compound 11 (0.500 mg, 1.49 mmol) and com-

pound 17 (1.00 g, 1.65 mmol) were dissolved in THF (7 mL) and

Et₃N (0.92 mL, 6.61 mmol) was added, followed by PdCl₂(PPh₃)

Compound 32: CBr₄(306 mg, 0.92 mmol) and PPh₃(242 mg,

0.92 mmol) were added at room temperature to a solution of the

compound 29 (300 mg, 0.37 mmol) in THF (4 mL) and the re-

sulting mixture was stirred for 30 min. The solution was then di-

luted in CH₂Cl₂and washed with water, and the organic layer was

dried with Na₂SO₄. The solvents were removed under reduced pres-

sure and the crude product was filtered through silica gel with

EtOAc/hexanes (1%) as eluent to provide the title compound 32 in

quantitative yield as a pale yellow solid. ¹H NMR (CDCl₃): δ =

7.28 (s, 3 H ar.), 7.08 (brs, 6 H ar.), 6.92 (d, J = 7.1 Hz, 2ϫHC–

CF), 3.43 (t, J = 6.6 Hz, CH₂–Br), 2.43 (t, J = 6.9 Hz, CϵC–CH₂),

2.00 (m, 2 H alkyl), 1.74 (m, 2 H alkyl), 1.23 (brs, 18ϫCH₃) ppm.

(46 mg, 0.07 mmol) and CuI (13 mg, 0.07 mmol). The resulting

2

solution was stirred at 60 °C under argon for 2 d. The mixture was

then diluted in CH₂Cl₂and washed with saturated aqueous NH₄Cl,

and the organic layer was dried with Na₂SO₄. The solvents were

removed under reduced pressure and the crude product was puri-

fied by flash chromatography on silica gel with EtOAc/hexanes

(20%)as eluent to provide the title compound 29 (348 mg, 29%

yield) as a white solid, together with compound 11(309 mg, 62%

1

recovery). H NMR (CDCl₃): δ = 7.29 (s, 3 H ar.), 7.11 (brs, 6 H

ar.), 6.93 (d, J = 7.0 Hz, 2ϫHC–CF), 3.64 (t, J = 5.7 Hz, CH₂–

O), 2.41 (t, J = 6.1 Hz, CϵC-CH₂), 1.67 (m, 4 H alkyl), 1.24 (brs,

18ϫCH₃) ppm. ¹³C NMR (CDCl₃): δ = 163.0 (dd, J = 252.4, J = ¹³C NMR (CDCl₃): δ = 162.9 (dd, J = 252.7, J = 7.0 Hz, 2 C),

7.0 Hz, 2 C), 149.8 (6ϫ), 144.6 (3ϫ), 124.7 (t, J = 11.7 Hz), 123.9

(6ϫ), 119.8 (3ϫ), 114.2 (m*, 2 C), 108.3 (t, J = 2.9 Hz), 102.9 (t,

J = 20.3 Hz), 93.6, 79.2 (t, J = 3.6 Hz), 70.9, 62.0, 57.3, 34.8 (6ϫ),

31.7, 31.4 (18ϫ), 24.7, 19.1 ppm. ¹⁹F NMR (CDCl₃): δ = –108.5

(d, J = 7.1 Hz) ppm. HRMS: calcd. for C₅₇H₇₅F₂O [M + H]⁺

813.5780; found 813.5788. (m*: The complex multiplicity of this sig-

nal is attributed to coupling with fluorine).

149.8 (6ϫ), 144.6 (3ϫ), 124.4 (t, J = 11.7 Hz), 123.9 (6ϫ), 119.9

(3ϫ), 114.2 (m*, 2 C), 108.4 (t, J = 3.1 Hz), 103.1 (t, J = 20.2 Hz),

92.8, 79.4 (t, J = 3.5 Hz), 70.8, 57.3, 34.8 (6ϫ), 32.9, 31.6, 31.4

(18ϫ), 26.8, 18.6 ppm. ¹⁹F NMR (CDCl₃): δ = –108.4 (d, J =

7.3 Hz) ppm. HRMS: calcd. for C₅₇H₇₄BrF₂875.4936[M + H]⁺;

found 875.4953. (m*: The complex multiplicity of this signal is at-

tributed to coupling with fluorine).

Compound 30: CBr₄(1.68 g, 5.08 mmol) and PPh₃(1.33 g,

5.08 mmol) were added at room temperature to a solution of the

compound 27 (1.75 g, 2.03 mmol) in THF (14 mL) and the re-

sulting mixture was stirred for 30 min. The solution was then di-

luted in CH₂Cl₂and washed with water, and the organic layer was

dried with Na₂SO₄. The solvents were removed under reduced pres-

sure and the crude product was filtered through silica gel with

EtOAc/hexanes (2%) as eluent to provide compound 30 (1.81 g,

97% yield) as a yellow oil. ¹H NMR (CDCl₃): δ = 7.21 (d, J =

8.6 Hz, 6 H ar.), 6.89 (d, J = 7.0 Hz, 2ϫHC–CF), 6.80 (d, J =

Compound 33: Compound 30 (1.81 g, 1.96 mmol) and potassium

thioacetate (448 mg, 3.92 mmol) in THF (10 mL) were heated at

60 °C overnight. The mixture was diluted in CH₂Cl₂and washed

with water, and the organic layer was dried with Na₂SO₄. The sol-

vents were removed under reduced pressure and the crude product

was purified by flash chromatography on silica gel with EtOAc/

hexanes (2%) as eluent to provide the title compound 33 (1.65 g,

92% yield) as a yellow oil. ¹H NMR (CDCl₃): δ = 7.21 (d, J =

8.7 Hz, 6 H ar.), 6.89 (d, J = 7.1 Hz, 2ϫHC–CF), 6.79 (d, J =

8.7 Hz, 6 H ar.), 3.90 (t, J = 6.3 Hz, 3ϫCH₂–O), 2.87 (t, J =

8.6 Hz, 6 H ar.), 3.91 (t, J = 6.4 Hz, 3ϫCH₂–O), 3.39 (t, J = 6.9 Hz, CH₂–S), 2.37 (t, J = 6.6 Hz, CϵC–CH₂), 2.28 (s, CH₃–

6.6 Hz, CH₂–Br), 2.39 (t, J = 6.8 Hz, CϵC–CH₂), 1.96 (m, 2 H C=O), 1.74 (m, 8 H alkyl), 1.62 (m, 2 H alkyl), 1.42 (m, 6 H alkyl),

alkyl), 1.73 (m, 8 H alkyl), 1.43 (m, 6 H alkyl), 1.28 (m, 24 H alkyl), 1.28 (m, 24 H alkyl), 0.87 (t, J = 6.9 Hz, 3ϫCH₃) ppm. ¹³C NMR

Eur. J. Org. Chem. 2010, 3049–3067

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3061

D. Thibeault, M. Auger, J.-F. Morin

FULL PAPER

(CDCl₃): δ = 195.3, 163.1 (dd, J = 252.9, J = 7.0 Hz, 2 C), 158.0

(m, 12 H alkyl), 1.27 (m, 48 H alkyl), 0.87 (t, J = 6.8 Hz,

(3ϫ), 137.2 (3ϫ), 130.1 (6ϫ), 125.0 (t, J = 11.9 Hz), 114.6 (m*, 2 6ϫCH₃) ppm. ¹³C NMR (CDCl₃): δ = 163.0 (dd, J = 252.5, J =

C), 113.8 (6ϫ), 108.7 (t, J = 2.9 Hz), 102.6 (t, J = 20.3 Hz), 93.5,

79.3 (t, J = 3.5 Hz), 71.7, 67.8 (3ϫ), 54.7, 31.9 (3ϫ), 30.5, 29.4

(3ϫ), 29.3 (6ϫ), 28.8, 28.5, 27.3, 26.1 (3ϫ), 22.7 (3ϫ), 19.0, 14.1

(3ϫ) ppm. ¹⁹F NMR (CDCl₃): δ = –108.3 (d, J = 7.2 Hz) ppm.

6.7 Hz, 4 C), 157.9 (6ϫ), 137.2 (6ϫ), 130.0 (6ϫ), 125.0 (t, J =

11.8 Hz, 2 C), 114.2 (m*, 4 C), 93.6 (2ϫ), 79.3 (t, J = 3.3 Hz, 2

C), 71.6 (2ϫ), 67.8 (6ϫ), 54.7 (2ϫ), 38.2 (2ϫ), 31.8 (6ϫ), 29.4

(6ϫ), 29.3 (12ϫ), 28.2 (2ϫ), 27.0 (2ϫ), 26.1 (6ϫ), 22.7 (6ϫ), 19.0

HRMS: calcd. for C₅₉H₇₇F₂O₄S 919.5511 [M + H]⁺; found (2ϫ), 14.1 (6ϫ) ppm. ¹⁹F NMR (CDCl₃): δ = –108.2 (d, J =

919.5494. (m*: The complex multiplicity of this signal is attributed

to coupling with fluorine).

7.2 Hz) ppm. HRMS: calcd. for [C₁₁₄H₁₄₆F₄O₆S₂]*⁺1751.0492

[M]*⁺; found 1751.0504. (m*: The complex multiplicity of this signal

is attributed to coupling with fluorine).

Compound 34: Compound 31 (440 mg, 0.76 mmol) and potassium

thioacetate (173 mg, 1.51 mmol) in THF (4 mL) were heated at

60 °C overnight. The mixture was diluted in CH₂Cl₂and washed

with water, and the organic layer was dried with Na₂SO₄. The sol-

vents were removed under reduced pressure and the crude product

was purified by flash chromatography on silica gel with EtOAc/

Compound 5: Compound 34 (373 mg, 0.65 mmol) was dissolved in

a solution of HCl/MeOH (1 , 2 mL) with THF (2 mL) and stirred

overnight at 50 °C. A saturated solution of I₂in CH₂Cl₂was added

to this solution until persistence of the brown colouration. The

mixture was stirred for 15 min, diluted in CH₂Cl₂and washed with

saturated aqueous Na₂S₂O₃until disappearance of the brown col-

hexanes (5%)as eluent to provide the title compound 34 (411 mg,

1

94% yield) as a yellow oil. H NMR (CDCl₃): δ = 7.25 (brs, 3 H our. The organic layer was dried with Na₂SO₄and the solvents

ar.), 7.16 (m, 3 H ar.), 7.05 (m, 6 H ar.), 6.91 (d, J = 7.2 Hz, were removed under reduced pressure. The crude product was puri-

2ϫHC–CF), 2.89 (t, J = 6.9 Hz, CH₂–S), 2.39 (t, J = 6.6 Hz,

CϵC–CH₂), 2.29 (s, 3ϫCH₃and CH₃–C=O), 1.70 (m, 2 H alkyl),

1.64 (m, 2 H alkyl) ppm. ¹³C NMR (CDCl₃): δ = 195.6, 162.9 (dd,

J = 252.8, J = 6.7 Hz, 2 C), 144.7 (3ϫ), 137.6 (3ϫ), 129.9 (3ϫ),

127.8 (3ϫ), 127.7 (3ϫ), 126.3 (3ϫ), 125.0 (t, J = 11.8 Hz), 114.3

(m*, 2 C), 107.3 (t, J = 3.1 Hz), 102.5 (t, J = 20.1 Hz), 93.5, 79.2

(t, J = 3.7 Hz), 72.3, 56.5, 30.6, 28.7, 28.5, 27.3, 26.1 (3ϫ),

19.0 ppm. ¹⁹F NMR (CDCl₃): δ = –108.3 (d, J = 7.4 Hz) ppm.

HRMS: calcd. for [C₃₈H₃₄F₂OS]*⁺576.2293 [M]*⁺; found

576.2305. (m*: The complex multiplicity of this signal is attributed

to coupling with fluorine).

fied by flash chromatography on silica gel with EtOAc͞hexanes

(4%)as eluent to provide of the title compound 5 (258 mg, 75%

yield) as an orange oil. H NMR (CDCl₃): δ = 7.26 (brs, 6 H ar.),

1

7.16 (m, 6 H ar.), 7.05 (m, 12 H ar.), 6.90 (d, J = 7.3 Hz, 4ϫHC–

CF), 2.69 (t, J = 7.1 Hz, 2ϫCH₂–S), 2.39 (t, J = 6.7 Hz, 2ϫCϵC–

CH₂), 2.28 (s, 6ϫCH₃), 1.83 (m, 4 H alkyl), 1.66 (m, 4 H

alkyl) ppm. ¹³C NMR (CDCl₃): δ = 162.8 (dd, J = 252.5, J =

6.8 Hz, 4 C), 144.6 (2ϫ), 137.6 (2ϫ), 129.9 (2ϫ), 127.8 (2ϫ), 127.7

(2ϫ), 126.3 (2ϫ), 125.0 (t, J = 11.8 Hz, 2 C), 114.2 (m*, 4 C),

107.4 (t, J = 3.1 Hz, 2 C), 102.5 (t, J = 20.2 Hz, 2 C), 93.6 (2ϫ),

79.3 (t, J = 3.5 Hz, 2 C), 72.2 (2ϫ), 56.5 (2ϫ), 38.2 (2ϫ), 28.2

(2ϫ), 27.0 (2ϫ), 21.5 (6ϫ), 19.0 (2ϫ) ppm. ¹⁹F NMR (CDCl₃): δ

= –108.1 (d, J = 7.1 Hz) ppm. HRMS: calcd. for C₇₂H₆₃F₄S₂

1067.4307 [M + H]⁺; found 1067.4287. (m*: The complex multi-

plicity of this signal is attributed to coupling with fluorine).

Compound 35: Compound 32 (310 mg, 0.35 mmol) and potassium

thioacetate (121 mg, 1.06 mmol) were heated at 60 °C in THF

(5 mL) overnight. The mixture was diluted in CH₂Cl₂and washed

with water, and the organic layer was dried with Na₂SO₄. The sol-

vents were removed under reduced pressure and the crude product

was purified by preparative TLC on silica gel with EtOAc/hexanes

Compound 51: Compound 35 (238 mg, 0.27 mmol) was dissolved

in a solution of HCl/MeOH (1 , 2 mL) with THF (2 mL) and

(2%) as eluent to provide the title compound 35 (260 mg, 85% stirred overnight at 50 °C. A saturated solution of I₂in CH₂Cl₂was

1

yield) as a yellow solid. H NMR (CDCl₃): δ = 7.29 (s, 3 H ar.),

7.09 (brs, 6 H ar.), 6.93 (d, J = 7.0 Hz, 2ϫHC–CF), 2.90 (t, J =

added to this solution until persistence of the brown colouration.

The mixture was stirred for 15 min, diluted in CH₂Cl₂and washed

6.9 Hz, CH₂–S), 2.41 (t, J = 6.5 Hz, CϵC–CH₂), 2.29 (s, CH₃– with saturated aqueous Na₂S₂O₃until disappearance of the brown

C=O), 1.73 (m, 2 H alkyl), 1.66 (m, 2 H alkyl), 1.23 (brs,

18ϫCH₃) ppm. ¹³C NMR (CDCl₃): δ = 195.4, 162.9 (dd, J =

252.6, J = 6.9 Hz, 2 C), 149.8 (6ϫ), 144.6 (3ϫ), 124.6 (t, J =

11.6 Hz), 123.9 (6ϫ), 119.9 (3ϫ), 114.2 (m*, 2 C), 108.3 (t, J =

3.1 Hz), 103.0 (t, J = 20.3 Hz), 93.2, 79.4 (t, J = 3.6 Hz), 70.9, 57.3,

colour. The organic layer was dried with Na₂SO₄and the solvents

were evaporated under reduced pressure. The crude product was

purified by preparative TLC on silica gel with EtOAc͞hexanes

(3%) as eluent to provide the title compound 51 (207 mg, 91%

1

yield) as a pale yellow solid. H NMR (CDCl₃): δ = 7.28 (s, 6 H

34.8 (6ϫ), 31.4 (18ϫ), 30.5, 28.8, 28.5, 27.3, 18.9 ppm. ¹⁹F NMR ar.), 7.08 (brs, 12 H ar.), 6.92 (d, J = 7.4 Hz, 4ϫHC–CF), 2.73 (t,

(CDCl₃): δ = –108.6 (d, J = 7.1 Hz) ppm. HRMS: calcd. for

C₅₉H₇₇F₂OS 871.5658 [M + H]⁺; found 871.5677. (m*: The com-

plex multiplicity of this signal is attributed to coupling with fluorine).

J = 7.1 Hz, 2ϫCH₂–S), 2.42 (t, J = 6.8 Hz, 2ϫCϵC–CH₂), 1.86

(m, 4 H alkyl), 1.69 (m, 4 H alkyl), 1.23 (brs, 36ϫCH₃) ppm. ¹³C

NMR (CDCl₃): δ = 162.9 (dd, J = 252.3, J = 6.7 Hz, 4 C), 149.8

(12ϫ), 144.6 (6ϫ), 124.5 (t, J = 11.7 Hz, 2 C), 123.9 (12ϫ), 119.9

(6ϫ), 114.2 (m*, 4 C), 108.4 (t, J = 2.8 Hz, 2 C), 103.1 (t, J =

20.2 Hz, 2 C), 93.2 (2ϫ), 79.4 (t, J = 3.3 Hz, 2 C), 70.9 (2ϫ), 57.3

(2ϫ), 38.3 (2ϫ), 34.8 (12ϫ), 31.4 (36ϫ), 28.2 (2ϫ), 27.0 (2ϫ),

Compound 3: Compound 33 (1.60 g, 1.74 mmol) was dissolved in a

solution of HCl/MeOH (1 , 7 mL) with THF (7 mL) and stirred

overnight at 50 °C. A saturated solution of I₂in CH₂Cl₂was added

to this solution until persistence of the brown colouration. The

mixture was stirred for 15 min, diluted in CH₂Cl₂and washed with

saturated aqueous Na₂S₂O₃until the disappearance of the brown

colour. The organic layer was dried with Na₂SO₄and the solvents

were removed under reduced pressure. The crude product was puri-

fied by flash chromatography on silica gel with EtOAc͞hexanes

19.0 (2ϫ) ppm. ¹⁹F NMR (CDCl₃):

δ = –108.5 (d, J =

7.7 Hz) ppm. HRMS: calcd. for [C₁₁₄H₁₄₆F₄S₂] 1655.0802 [M];

found 1655.0786. (m*: The complex multiplicity of this signal is at-

tributed to coupling with fluorine).

Compound 36: Compound 11 (1.31 g, 3.91 mmol) and compound

22 (1.08 g, 4.69 mmol) were dissolved in THF (15 mL)and Et₃N

(1%) as eluent to provide the title compound 3 (1.31 g, 86% yield)

1

as an orange oil. H NMR (CDCl₃): δ = 7.21 (d, J = 8.7 Hz, 12 H (2.61 mL, 18.8 mmol) was added, followed by PdCl₂(PPh₃)₂

ar.), 6.89 (d, J = 7.2 Hz, 4ϫHC–CF), 6.80 (d, J = 8.7 Hz, 12 H

ar.), 3.90 (t, J = 6.3 Hz, 6ϫCH₂–O), 2.68 (t, J = 7.1 Hz, 2ϫCH₂–

S), 2.38 (t, J = 6.4 Hz, 2ϫCϵC–CH₂), 1.74 (m, 20 H alkyl), 1.42

(132 mg, 0.19 mmol) and CuI (36 mg, 0.19 mmol). The resulting

solution was stirred at 60 °C under argon for 2 d. Propargyl alcohol

(1 mL) was then added (to remove the unreacted compound 11)

3062

www.eurjoc.org

Eur. J. Org. Chem. 2010, 3049–3067

Fluorine-Containing Molecular Rotors and Assembly on Gold Nanoparticles

and the mixture was stirred another day at 60 °C. The mixture was

then diluted in CH₂Cl₂and washed with saturated aqueous NH₄Cl,

and the organic layer was dried with Na₂SO₄. The solvents were

removed under reduced pressure and the crude product was puri-

fied by flash chromatography on silica gel with EtOAc/hexanes

(25%) as eluent to provide the title compound 36 (1.375 g, 80%

yield) as a brown solid. ¹H NMR (CDCl₃): δ = 7.49 (d, J = 8.6 Hz,

2 H ar.), 6.93 (d, J = 7.4 Hz, 2ϫHC–CF), 6.87 (d, J = 8.7 Hz, 2

Compound 39: CBr₄(1.44 g, 4.35 mmol) and PPh₃(1.14 g,

4.35 mmol) were added at room temperature to a solution of com-

pound 37 (565 mg, 1.74 mmol) in THF (4 mL). The resulting mix-

ture was stirred for 30 min, after which CH₂Cl₂was added. The

organic layer was washed with water and dried with Na₂SO₄. The

solvents were removed under reduced pressure and the crude prod-

uct was filtered through silica gel with EtOAc/hexanes (1%) as elu-

ent to provide the title compound 39 (650 mg, 96% yield) as a white

1

H ar.), 3.96 (t, J = 6.6 Hz, CH₂–O-ar.), 3.71 (t, J = 5.5 Hz, alkyl- solid. H NMR (CDCl₃): δ = 7.33 (m, 2 H ar.), 7.19 (m, 1 H ar.),

CH₂–O), 2.46 (t, J = 6.4 Hz, CϵC–CH₂), 1.77 (m,2 H alkyl), 1.71

7.12 (m, 1 H ar.), 6.89 (d, J = 7.3 Hz, 2ϫHC–CF), 3.39 (t, J =

(m, 4 H alkyl), 1.44 (m, 2 H alkyl), 1.30 (m, 8 H alkyl), 0.89 (t, J 6.6 Hz, CH₂–Br), 2.39 (t, J = 6.9 Hz, CϵC–CH₂), 2.31 (s, CH₃),

= 6.6 Hz, CH₃) ppm. ¹³C NMR (CDCl₃): δ = 163.1 (dd, J = 252.3,

J = 6.8 Hz, 2 C), 159.8, 133.3 (2ϫ), 124.9 (t, J = 11.8 Hz), 114.6

(2ϫ), 114.3 (m*, 2 C), 102.6 (t, J = 20.0 Hz), 100.5 (t, J = 3.1 Hz),

94.0, 79.2 (t, J = 3.7 Hz), 74.9, 68.1, 62.4, 31.8 (2ϫ), 29.4, 29.2

1.94 (m, 2 H alkyl), 1.69 (m, 2 H alkyl) ppm. ¹³C NMR (CDCl₃):

δ = 162.4 (dd, J = 253.3, J = 6.7 Hz, 2 C), 138.1, 132.3, 130.0,

128.9, 128.3, 125.3 (t, J = 11.7 Hz), 122.2, 114.3 (m*, 2 C), 102.4

(t, J = 20.2 Hz), 100.6 (t, J = 2.9 Hz), 93.7, 79.3 (t, J = 3.8 Hz),

(2ϫ), 26.0, 24.8, 22.7, 19.3, 14.1 ppm. ¹⁹F NMR (CDCl₃): 75.8, 33.0, 31.8, 26.9, 21.2, 18.6 ppm. ¹⁹F NMR (CDCl₃): δ =

δ = –108.9 (d, J = 7.6 Hz) ppm. HRMS: calcd. for [C₂₈H₃₂F₂O₂]*⁺

438.2365 [M]*⁺; found 438.2367. (m*: The complex multiplicity of

this signal is attributed to coupling with fluorine).

–108.2 (d, J = 7.8 Hz) ppm. HRMS: calcd. for [C₂₁H₁₇BrF₂]*⁺

386.0476 [M]*⁺; found 386.0478). (m*: The complex multiplicity of

this signal is attributed to coupling with fluorine).

Compound 37: Compound 11 (1.21 g, 3.60 mmol) and 3-ethynyltol-

uene (550 mg, 4.74 mmol) were dissolved in THF (10 mL) and

Et₃N (2 mL, 14.4 mmol) was added, followed by PdCl₂(PPh₃)₂

(101 mg, 0.14 mmol) and CuI (14 mg, 0.14 mmol). The resulting

solution was stirred at 60 °C under argon for 2 d. Propargyl alcohol

(1 mL) was then added (to remove the unreacted compound 11)

and the mixture was stirred for another day at 60 °C. The mixture

was then diluted in CH₂Cl₂and washed with saturated aqueous

NH₄Cl, and the organic layer was dried with Na₂SO₄. The solvents

were removed under reduced pressure and the crude product was

purified by flash chromatography on silica gel with EtOAc/hexanes

(25%) as eluent to provide the title compound 37(660 mg, 57%

Compound 40: Compound 38 (1.38 g, 2.74 mmol) and potassium

thioacetate (470 mg, 4.11 mmol) were heated at 60 °C overnight in

THF (10 mL). The mixture was then diluted in CH₂Cl₂and washed

with water. The organic layer was dried with Na₂SO₄and the sol-

vents were removed under reduced pressure. The crude product was

purified by flash chromatography on silica gel with EtOAc/hexanes

(3%) as eluent to provide the title compound 40 (1.29 g, 95% yield)

1

as a yellow solid. H NMR (CDCl₃): δ = 7.46 (d, J = 8.3 Hz, 2 H

ar.), 6.91 (d, J = 7.1 Hz, 2ϫHC–CF), 6.83 (d, J = 8.6 Hz, 2 H ar.),

3.90 (t, J = 6.5 Hz, CH₂–O), 2.89 (t, J = 6.9 Hz, CH₂–S), 2.40 (t,

J = 7.0 Hz, CϵC–CH₂), 2.31 (s, CH₃–C=O), 1.69 (m, 6 H alkyl),

1.41 (m, 2 H alkyl), 1.27 (m, 8 H alkyl), 0.88, (t, J = 6.3 Hz,

CH₃) ppm. ¹³C NMR (CDCl₃): δ = 195.5, 163.1 (dd, J = 252.9, J

= 6.9 Hz, 2 C), 159.8, 133.3 (2ϫ), 124.9 (t, J = 11.8 Hz), 114.5

(2ϫ), 114.3 (m*, 2 C), 114.2, 102.7 (t, J = 20.2 Hz), 100.7 (t, J =

2.9 Hz), 93.7, 79.3 (t, J = 3.7 Hz), 74.9, 68.1, 31.9, 30.5, 29.4, 29.3,

29.2, 28.8, 28.5, 27.4, 26.1, 22.7, 19.0, 14.1 ppm. ¹⁹F NMR

(CDCl₃): δ = –108.7 (d, J = 6.8 Hz) ppm. HRMS: calcd. for

[C₃₀H₃₄F₂O₂S]*⁺496.2242 [M]*⁺; found 496.2241. (m*: The com-

plex multiplicity of this signal is attributed to coupling with fluorine).

1

yield) as a brown solid. H NMR (CDCl₃): δ = 7.35 (m, 2 H ar.),

7.21 (m, 1 H ar.), 7.13 (m, 1 H ar.), 6.92 (d, J = 7.4 Hz, 2ϫHC–

CF), 3.64 (t, J = 5.8 Hz, CH₂–O), 2.77 (brs, OH), 2.42 (t, J =

6.4 Hz, CϵC–CH₂), 2.31 (s, CH₃), 1.67 (m,4 H alkyl) ppm. ¹³C

NMR (CDCl₃): δ = 162.4 (dd, J = 252.9, J = 6.7 Hz, 2 C), 138.1,

132.3, 130.0, 128.9, 128.3, 125.5 (t, J = 11.9 Hz), 122.2, 114.4 (m*,

2 C), 102.3 (t, J = 20.2 Hz), 100.5 (t, J = 2.9 Hz), 94.3, 79.1 (t, J =

3.8 Hz), 75.8, 62.0, 31.8, 24.8, 21.2, 19.3 ppm. ¹⁹F NMR (CDCl₃):

δ = –108.4 (d, J = 7.6 Hz) ppm. HRMS: calcd. for [C₂₁H₁₈F₂O]*⁺

324.1320 [M]*⁺; found 324.2520. (m*: The complex multiplicity of

this signal is attributed to coupling with fluorine).

Compound 41: Compound 39 (573 mg, 1.48 mmol) and potassium

thioacetate (338 mg, 2.96 mmol) were heated at 60 °C in THF

(4 mL) overnight. The mixture was then diluted in CH₂Cl₂and

washed with water. The organic layer was dried with Na₂SO₄and

the solvents were removed under reduced pressure. The crude prod-

uct was purified by flash chromatography on silica gel with EtOAc/

hexanes (1%) as eluent to provide the title compound 41(510 mg,

Compound 38: CBr₄(2.48 g, 7.47 mmol) and PPh₃(1.96 mg,

7.47 mmol) were added at room temperature to a solution of com-

pound 36 (1.31 g, 2.99 mmol) in THF (12 mL). The resulting mix-

ture was stirred for 30 min, after which CH₂Cl₂was added. The

organic layer was washed with water and dried with Na₂SO₄. The

solvents were removed under reduced pressure and the crude prod-

uct was filtered through silica gel with EtOAc/hexanes (2%) as elu-

ent to provide the title compound 38 (1.44 g, 96% yield) as a pale

1

90% yield) as a white solid. H NMR (CDCl₃): δ = 7.35 (m, 2 H

ar.), 7.22 (m, 1 H ar.), 7.14 (m, 1 H ar.), 6.92 (d, J = 7.4 Hz,

2ϫHC–CF), 2.89 (t, J = 7.0 Hz, CH₂–S), 2.40 (t, J = 6.8 Hz,

CϵC–CH₂), 2.32 (s, CH₃), 2.31 (s, CH₃), 1.70 (m, 2 H alkyl), 1.64

(m, 2 H alkyl) ppm. ¹³C NMR (CDCl₃): δ = 195.6, 162.4 (dd, J =

252.9, J = 6.5 Hz, 2 C), 138.1, 132.3, 129.9, 128.9, 128.3, 125.4 (t,

J = 11.7 Hz), 122.2, 114.4 (m*, 2 C), 102.3 (t, J = 20.0 Hz), 100.5

(t, J = 2.9 Hz), 93.9, 79.2 (t, J = 3.7 Hz), 75.8, 30.6, 28.8, 28.5, 27.3,

21.2, 19.0 ppm. ¹⁹F NMR (CDCl₃): δ = –108.4 (d, J = 7.5 Hz) ppm.

HRMS: calcd. for [C₂₃H₂₀F₂OS]*⁺382.1197 [M]*⁺; found

382.1202. (m*: The complex multiplicity of this signal is attributed

to coupling with fluorine).

1

yellow solid. H NMR (CDCl₃): δ = 7.45 (d, J = 8.6 Hz, 2 H ar.),

6.90 (d, J = 7.3 Hz, 2ϫHC–CF), 6.82 (d, J = 8.6 Hz, 2 H ar.), 3.88

(t, J = 6.6 Hz, CH₂–O), 3.40 (t, J = 6.6 Hz, CH₂–Br), 2.40 (t, J =

6.9 Hz, CϵC–CH₂), 1.96 (m, 2 H alkyl), 1.71 (m, 4 H alkyl), 1.39

(m, 2 H alkyl), 1.27 (m, 8 H alkyl), 0.88 (t, J = 6.5 Hz, CH₃) ppm.

¹³C NMR (CDCl₃): δ = 163.1 (dd, J = 252.3, J = 6.5 Hz, 2 C),

159.9, 133.3 (2ϫ), 124.8 (t, J = 11.9 Hz), 114.5 (2ϫ), 114.3 (m*, 2

C), 114.2, 102.7 (t, J = 20.1 Hz), 100.8 (t, J = 3.0 Hz), 93.4, 79.4

(t, J = 3.7 Hz), 74.9, 68.1, 33.0, 32.1, 31.8, 29.6, 29.5, 29.4, 26.9,

26.1, 22.8, 18.7, 14.2 ppm. ¹⁹F NMR (CDCl₃): δ = –108.6 (d, J =

7.2 Hz) ppm. HRMS: calcd. for [C₂₈H₃₁F₂BrO]*⁺500.1521 [M]*⁺;

found 500.1519. (m*: The complex multiplicity of this signal can be

attributed to coupling with fluorine).

Compound 4: Compound 40 (1.11 g, 2.24 mmol) was dissolved in a

solution of HCl/MeOH (1 , 7 mL) with THF (7 mL) and stirred

overnight at 50 °C. A saturated solution of I₂in CH₂Cl₂was added

to this solution until persistence of the brown colouration. The

Eur. J. Org. Chem. 2010, 3049–3067

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3063

D. Thibeault, M. Auger, J.-F. Morin

FULL PAPER

mixture was stirred for 15 min, diluted in CH₂Cl₂and washed with

saturated aqueous Na₂S₂O₃until disappearance of the brown col-

our. The organic layer was dried with Na₂SO₄and the solvents

were removed under reduced pressure. The crude product was puri-

fied by flash chromatography on silica gel with EtOAc͞hexanes

(3%) as eluent to provide the title compound 4 (956 mg, 94% yield)

found 306.1262. (m*: The complex multiplicity of this signal is at-

tributed to coupling with fluorine).

Compound 43: Compound 42 (1.38 g, 4.50 mmol) was dissolved in

acetone (25 mL) at room temperature in darkness, followed by NBS

(1.84 g, 10.4 mmol) and AgNO₃(115 mg, 0.68 mmol), and the re-

sulting solution was stirred for 4 h. The mixture was then diluted

in CH₂Cl₂and washed with water, and the organic layer was dried

with Na₂SO₄. The solvents were removed under reduced pressure

and the crude product was purified by flash chromatography on

silica gel with EtOAc/hexanes (25%) as eluent to provide the title

compound 43 (1.07 g, 76% yield) as an orange oil. Note: It is

strongly recommended to use freshly synthesized bromoalkyne 43.

Well stored 43 retains its orange colour whereas improper storage

leads to a red bromoalkyne, which is less efficient. Moreover, the

compound is degraded to about 50% (by ¹⁹F NMR) after one year

and optimal efficiency is already lost after one month. ¹H NMR

(CDCl₃): δ = 6.57 (d, J = 7.4 Hz, 2ϫHC–CF), 3.38 (t, J = 5.4 Hz,

CH₂–Br), 2.14 (t, J = 5.5 Hz, CϵC–CH₂), 1.40 (m,4 H alkyl) ppm.

¹³C NMR (CDCl₃): δ = 163.7 (dd, J = 253.9, J = 6.3 Hz, 2 C),

126.7 (t, J = 11.8 Hz), 114.8 (m*, 2 C), 101.7 (t, J = 19.8 Hz), 95.5,

79.3 (t, J = 3.5 Hz), 67.8, 62.2, 61.7 (t, J = 2.8 Hz), 32.3, 25.3,

19.7 ppm. ¹⁹F NMR (CDCl₃): δ = –108.4 (d, J = 7.4 Hz) ppm.

HRMS: calcd. for [C₁₄H₁₁BrF₂O]*⁺311.9956 [M]*⁺; found

311.9961. (m*: The complex multiplicity of this signal is attributed

to coupling with fluorine).

1

as a white solid. H NMR (CDCl₃): δ = 7.45 (d, J = 8.4 Hz, 4 H

ar.), 6.91 (d, J = 7.3 Hz, 4ϫHC–CF), 6.82 (d, J = 8.4 Hz, 4 H ar.),

3.88 (t, J = 6.5 Hz, 2ϫCH₂–O), 2.69 (t, J = 6.8 Hz, 2ϫCH₂–S),

2.40 (t, J = 6.7 Hz, 2ϫCϵC–CH₂), 1.82 (m, 4 H alkyl), 1.73 (m,

4 H alkyl), 1.66 (m, 4 H alkyl), 1.40 (m, 4 H alkyl), 1.27 (m, 16 H

alkyl), 0.88 (t, J = 6.1 Hz, 2ϫCH₃) ppm. ¹³C NMR (CDCl₃): δ =

163.1 (dd, J = 252.6, J = 6.8 Hz, 4 C), 159.8 (2ϫ), 124.9 (2ϫ),

133.3 (4ϫ), (t, J = 11.8 Hz, 2 C), 114.5 (4ϫ), 114.3 (m*, 4 C),

114.2 (2ϫ), 102.7 (t, J = 20.1 Hz, 2 C), 100.7 (t, J = 2.8 Hz, 2 C),

93.8 (2ϫ), 79.3 (t, J = 3.6 Hz, 2 C), 74.9 (2ϫ), 68.0 (2ϫ), 38.3

(2ϫ), 31.9 (2ϫ), 29.4 (2ϫ), 29.3 (2ϫ), 29.2 (2ϫ), 28.3 (2ϫ), 27.1

(2ϫ), 26.1 (2ϫ), 22.7 (2ϫ), 19.1 (2ϫ), 14.1 (2ϫ) ppm. ¹⁹F NMR

(CDCl₃): δ = –108.5 (d, J = 7.7 Hz) ppm. HRMS: calcd. for

[C₅₆H₆₂F₄O₂S₂]*⁺906.4122 [M]*⁺; found 906.4102. (m*: The com-

plex multiplicity of this signal is attributed to coupling with fluorine).

Compound 6: Compound 41 (402 mg, 1.05 mmol) was dissolved in

a solution of HCl/MeOH (1 , 4 mL) with THF (4 mL) and stirred

overnight at 50 °C. A saturated solution of I₂in CH₂Cl₂was added

to this solution until persistence of the brown colouration. The

mixture was stirred for 15 min, diluted in CH₂Cl₂and washed with

saturated aqueous Na₂S₂O₃until disappearance of the brown col-

our. The organic layer was dried with Na₂SO₄and the solvents

were removed under reduced pressure. The crude product was puri-

fied by flash chromatography on silica gel with EtOAc͞hexanes

(1%) as eluent to provide the title compound 6 (354 mg, 99% yield)

Compound 44: Compounds43 (100 mg, 0.32 mmol) and 17 (213 mg,

0.35 mmol) were dissolved in THF (1.5 mL) and DIPEA (0.50 mL,

2.87 mmol) was added, followed by Pd₂(dba₃)₃·CHCl₃(17 mg,

0.02 mmol) and CuI (3 mg, 0.02 mmol). The resulting solution was

stirred overnight at room temperature under argon. The mixture

was then diluted in CH₂Cl₂and washed with saturated aqueous

NH₄Cl, and the organic layer was dried with Na₂SO₄. The solvents

were removed under reduced pressure and the crude product was

purified by flash chromatography on silica gel with EtOAc/hexanes

(1%) to provide the trityl compound 17 (121 mg, 57% recovery)

followed with EtOAc/hexanes (25%) as eluent to provide the title

compound 44 (85 mg, 32% yield) as a brown solid. ¹H NMR

(CDCl₃): δ = 7.29 (s, 3 H ar.), 6.99 (brs, 6 H ar.), 6.90 (d, J =

7.4 Hz, 2ϫHC–CF), 3.68 (t, J = 5.7 Hz, CH₂–O), 2.45 (t, J =

6.3 Hz, CϵC–CH₂), 1.70 (m, 4 H ar.), 1.23 (brs, 18ϫCH₃) ppm.

¹³C NMR (CDCl₃): δ = 163.6 (dd, J = 254.4, J = 6.3 Hz, 2 C),

150.0 (6ϫ), 143.9 (3ϫ), 126.0 (t, J = 11.9 Hz), 123.8 (6ϫ), 120.2

(3ϫ), 114.3 (m*, 2 C), 101.5 (t, J = 19.9 Hz), 94.9, 92.9, 85.0, (t, J

= 2.9 Hz), 79.1 (t, J = 3.6 Hz), 68.3, 63.6, 62.2, 57.3, 34.8 (6ϫ),

31.8, 31.4 (18ϫ), 24.7, 19.3 ppm. ¹⁹F NMR (CDCl₃): δ = –107.5

(d, J = 7.2 Hz) ppm. HRMS: calcd. for C₅₉H₇₅F₂O 837.5780 [M +

H]⁺; found 837.5815. (m*: The complex multiplicity of this signal is

attributed to coupling with fluorine).

1

as a yellow oil. H NMR (CDCl₃): δ = 7.35 (m, 4 H ar.), 7.22 (m,

2 H ar.), 7.14 (m, 2 H ar.), 6.92 (d, J = 7.4 Hz, 4ϫHC–CF), 2.71

(t, J = 7.2 Hz, 2ϫCH₂–S), 2.41 (t, J = 6.8 Hz, 2ϫCϵC–CH₂),

2.32 (s, 2ϫCH₃), 1.83 (m, 4 H alkyl), 1.67 (m, 4 H alkyl) ppm. ¹³

C

NMR (CDCl₃): δ = 162.4 (dd, J = 253.2, J = 7.0 Hz, 4 C), 138.1

(2ϫ), 132.3 (2ϫ), 129.9 (2ϫ), 128.9 (2ϫ), 128.3 (2ϫ), 125.3 (t, J

= 11.7 Hz, 2 C), 122.2 (2ϫ), 114.4 (m*, 4 C), 102.3 (t, J = 20.1 Hz,

2 C), 100.5 (t, J = 3.0 Hz, 2 C), 94.0 (2ϫ), 79.3 (t, J = 3.8 Hz, 2

C), 75.8 (2ϫ), 38.3 (2ϫ), 28.3 (2ϫ), 27.0 (2ϫ), 21.2 (2ϫ), 19.1

(2ϫ) ppm. ¹⁹F NMR (CDCl₃): δ = –108.3 (d, J = 7.4 Hz) ppm.

HRMS: calcd. for C₄₂H₃₅F₄S₂679.2111 [M + H]; found 679.2101.

(m*: The complex multiplicity of this signal can be attributed to

coupling with fluorine).

Compound 42: Compound 11 (3.64 g, 10.8 mmol) and TMSA

(4.59 mL, 32.5 mmol) were dissolved in THF (55 mL) and Et₃N

(6.04 mL, 43.3 mmol) was added, followed by PdCl₂(PPh₃)₂

(304 mg, 0.43 mmol) and CuI (83 mg, 0.43 mmol). The resulting

solution was stirred at 60 °C under argon for 2 d. The mixture was

then diluted in CH₂Cl₂and washed with saturated aqueous NH₄Cl,

and the organic layer was dried with Na₂SO₄. The solvents were

removed under reduced pressure and the crude product was puri-

fied by flash chromatography on silica gel with EtOAc/hexanes

(25%) as eluent to provide the title compound 42 (3.31 g, 99%

Compound 45: CBr₄(623 mg, 1.88 mmol) and PPh₃(493 mg,

1.88 mmol) were added at room temperature to a solution of the

compound 44 (629 mg, 0.75 mmol) in THF (4 mL)and the resulting

mixture was stirred for 30 min. The solution was then diluted in

CH₂Cl₂and washed with water, and the organic layer was dried

with Na₂SO₄. The solvents were removed under reduced pressure

yield) as a pale yellow oil. ¹H NMR (CDCl₃): δ = 6.89 (d, J = and the crude product was filtered through silica gel with EtOAc/

7.5 Hz, 2ϫHC–CF), 3.69 (t, J = 5.9 Hz, CH₂–O), 2.45 (t, J =

6.5 Hz, CϵC–CH₂), 1.93 (brs, OH), 1.69 (m,4 H alkyl), 0.27 (s,

hexanes (1%) as eluent to provide the title compound 45 (625 mg,

1

94% yield) as a yellow solid. H NMR (CDCl₃): δ = 7.30 (s, 3 H

TMS-C) ppm. ¹³C NMR (CDCl₃): δ = 162.9 (dd, J = 253.6, J = ar.), 7.01 (brs, 6 H ar.), 6.89 (d, J = 7.2 Hz, 2ϫHC–CF), 3.39 (t,

6.8 Hz, 2 C), 125.8 (t, J = 11.9 Hz), 114.3 (m*, 2 C), 107.0 (t, J =

3.1 Hz), 102.0 (t, J = 20.1 Hz), 94.4, 90.7, 79.0 (t, J = 3.7 Hz), 62.2,

31.8, 24.7, 19.3, –0.3 (3ϫ) ppm. ¹⁹F NMR (CDCl₃): δ = –108.2 (d,

J = 7.5 Hz) ppm. HRMS: calcd. for [C₁₇H₂₀F₂OSi] 306.1251 [M];

J = 6.5 Hz, CH₂–Br), 2.42 (t, J = 6.8 Hz, CϵC–CH₂), 1.98 (m, 2

H alkyl), 1.73 (m, 2 H alkyl), 1.24 (brs, 18ϫCH₃) ppm. ¹³C NMR

(CDCl₃): δ = 163.6 (dd, J = 254.7, J = 6.3 Hz, 2 C), 150.1 (6ϫ),

144.1 (3ϫ), 125.9 (t, J = 11.6 Hz), 123.8 (6ϫ), 120.2 (3ϫ), 114.3

3064

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Eur. J. Org. Chem. 2010, 3049–3067

Fluorine-Containing Molecular Rotors and Assembly on Gold Nanoparticles

(m*, 2 C), 101.6 (t, J = 19.9 Hz), 94.4, 93.2, 85.1, (t, J = 2.8 Hz),

δ = 150.8 (2ϫ), 126.4 (2ϫ), 123.1, 122.2, 106.6, 92.6, 34.9 (2ϫ),

79.3 (t, J = 3.5 Hz), 68.4, 63.7, 62.2, 57.5, 34.8 (6ϫ), 32.7, 31.7, 31.5 (6ϫ), 0.3 (3ϫ) ppm. HRMS: calcd. for C₁₉H₃₀Si, 286.2117

31.4 (18ϫ), 26.7, 18.6 ppm. ¹⁹F NMR (CDCl₃): δ = –107.2 (d, J = [M]; found 286.2124.

7.3 Hz) ppm. HRMS: calcd. for C₅₉H₇₄BrF₂899.4936 [M + H]⁺;

Compound 48: Compound 47 (1.17 g, 4.08 mmol) was dissolved in

found 899.4942. (m*: The complex multiplicity of this signal is at-

THF/MeOH/H₂O (18:5:5 mL) in the presence of NaOH (1.63 g,

40.8 mmol) and the mixture was stirred for 90 min at room tem-

tributed to coupling with fluorine).

Compound 46: Compound 45 (585 mg, 0.66 mmol) and potassium

thioacetate (227 mg, 1.99 mmol) were heated at 60 °C in THF

(4 mL) overnight. The mixture was then diluted in CH₂Cl₂and

washed with water. The organic layer was dried with Na₂SO₄and

solvents were removed under reduced pressure. The crude product

was purified by flash chromatography on silica gel with EtOAc/

hexanes (1%) as eluent to provide the title compound 46 (507 mg,

perature. The solution was acidified until pH ≈ 6 and extracted

three times with CH₂Cl₂, and the combined organic layers were

dried with Na₂SO₄. The solvents were removed under reduced pres-

sure and filtration through silica gel with hexanes as eluent afforded

the crude deprotected compound, which was dried 30 min prior to

use. The previously obtained compound and compound 43 (1.07 g,

3.40 mmol) were then dissolved in THF (17 mL) with DIPEA

(5.33 mL, 30.6 mmol), followed by Pd₂(dba₃)₃·CHCl₃(176 mg,

1

87% yield) as a yellow solid. H NMR (CDCl₃): δ = 7.30 (s, 3 H

ar.), 7.01 (brs, 6 H ar.), 6.90 (d, J = 7.3 Hz, 2ϫHC–CF), 2.90 (t, 0.17 mmol) and CuI (32 mg, 0.17 mmol). The resulting solution

J = 6.9 Hz, CH₂–S), 2.42 (t, J = 6.5 Hz, CϵC–CH₂), 2.29 (s, CH₃–

was stirred under argon overnight at room temperature. The mix-

ture was then diluted in CH₂Cl₂and washed with saturated aque-

ous NH₄Cl, and the organic layer was dried with Na₂SO₄. The

solvents were removed under reduced pressure and the crude prod-

uct was purified by flash chromatography on silica gel with EtOAc/

hexanes (25%) as eluent to provide the title compound 48 (1.02 g,

C=O), 1.71 (m, 2 H alkyl), 1.65 (m, 2 H alkyl), 1.24 (brs,

18ϫCH₃) ppm. ¹⁹F NMR (CDCl₃):

δ = –107.3 (d, J =

7.3 Hz) ppm. ¹³C NMR (CDCl₃): δ = 195.4, 163.7 (dd, J = 254.5,

J = 6.3 Hz, 2 C), 150.0 (6ϫ), 143.9 (3ϫ), 125.9 (t, J = 11.8 Hz),

123.8 (6ϫ), 120.2 (3ϫ), 114.3 (m*, 2 C), 101.5 (t, J = 19.9 Hz),

94.5, 92.9, 85.1 (t, J = 3.0 Hz), 79.2 (t, J = 3.8 Hz), 68.3, 63.6, 57.3,

34.8 (6ϫ), 31.4 (18ϫ), 30.5, 28.8, 28.4, 27.3, 19.0 ppm. HRMS:

calcd. for C₆₁H₇₇F₂OS 895.5658[M + H]⁺; found 895.5691. (m*:

The complex multiplicity of this signal is attributed to coupling with

fluorine).

1

67% yield) as a brown solid. H NMR (CDCl₃): δ = 7.47 (s, 1 H

ar.), 7.40 (m, 2 H ar.), 6.90 (d, J = 7.4 Hz, 2ϫHC–CF), 3.67 (t, J

= 5.8 Hz, CH₂–O), 2.62 (s, OH), 2.44 (t, J = 6.2 Hz, CϵC–CH₂),

1.69 (m, 4 H alkyl), 1.32 (brs, 6ϫCH₃) ppm. ¹³C NMR (CDCl₃):

δ = 163.5 (dd, J = 254.8, J = 6.1 Hz, 2 C), 151.1 (2ϫ), 126.8 (2ϫ),

126.5 (t, J = 11.9 Hz), 124.3, 120.3, 114.4 (m*, 2 C), 101.2 (t, J =

20.1 Hz), 95.3, 85.7, 84.5 (t, J = 2.7 Hz), 79.1 (t, J = 3.7 Hz), 72.4,

67.6, 62.0, 34.8 (2ϫ), 31.8, 31.2 (6ϫ), 24.8, 19.3 ppm. ¹⁹F NMR

(CDCl₃): δ = –107.3 (d, J = 7.5 Hz) ppm. HRMS: calcd. for

C₃₀H₃₃F₂O 447.2494 [M + H]⁺; found 447.2497. (m*: The complex

multiplicity of this signal is attributed to coupling with fluorine).

Compound 7: Compound 46 (474 mg, 0.54 mmol) was dissolved in

a solution of HCl/MeOH (1 , 2 mL) with THF (2 mL) and stirred

for 4 h at 50 °C. A saturated solution of I₂in CH₂Cl₂was added

to this solution until persistence of the brown colouration. The

mixture was stirred for 15 min, diluted in CH₂Cl₂and washed with

saturated aqueous Na₂S₂O₃until the disappearance of the brown

colour. The organic layer was dried with Na₂SO₄and the solvents

were removed under reduced pressure. The crude product was puri-

fied by preparative TLC on silica gel with EtOAc͞hexanes (2%) as

eluent to provide the title compound 7 (378 mg, 82% yield) as a

yellow solid, together with residual compound 46 (47 mg, 10%

Compound 49: CBr₄(1.80 g, 5.43 mmol) and PPh₃(1.42 g,

5.43 mmol) were added at room temperature to a solution of com-

pound 48 (970 mg, 2.17 mmol) in THF (6 mL) and the resulting

mixture was stirred for 30 min. The solution was then diluted in

CH₂Cl₂and washed with water, and the organic layer was dried

yield). ¹H NMR (CDCl₃): δ = 7.27 (s, 6 H ar.), 6.97 (brs, 12 H ar.), with Na₂SO₄. The solvents were removed under reduced pressure

6.89 (d, J = 7.4 Hz, 4ϫHC–CF), 2.73 (t, J = 7.1 Hz, 2ϫCH₂–S),

2.44 (t, J = 6.9 Hz, 2ϫCϵC–CH₂), 1.84 (m, 4 H alkyl), 1.70 (m,

4 H alkyl), 1.21 (brs, 36ϫCH₃) ppm. ¹³C NMR (CDCl₃): δ = 163.6

(dd, J = 254.4, J = 6.3 Hz, 4 C), 150.0 (12ϫ), 144.0 (6ϫ), 125.9

and the crude product was filtered through silica gel with EtOAc/

hexanes (1%) as eluent to provide the title compound 49 in quanti-

tative yield as a yellow oil. ¹H NMR (CDCl₃): δ = 7.46 (s, 1 H ar.),

7.40 (m, 2 H ar.), 6.89 (d, J = 7.4 Hz, 2ϫHC–CF), 3.44 (t, J =

(t, J = 11.9 Hz, 2 C), 123.8 (12ϫ), 120.2 (6ϫ), 114.3 (m*, 4 C), 6.6 Hz, CH₂–Br), 2.45 (t, J = 6.9 Hz, CϵC–CH₂), 2.00 (m, 2 H

101.6 (t, J = 20.1 Hz, 2 C), 94.5 (2ϫ), 93.0 (2ϫ), 85.0 (t, J =

2.3 Hz, 2 C), 79.2 (t, J = 3.6 Hz, 2 C), 68.3 (2ϫ), 63.6 (2ϫ), 57.3

(2ϫ), 38.1 (2ϫ), 34.8 (12ϫ), 31.4 (36ϫ), 28.2 (2ϫ), 26.9 (2ϫ),

alkyl), 1.75 (m, 2 H alkyl), 1.32 (brs, 6ϫCH₃) ppm. ¹³C NMR

(CDCl₃): δ = 163.4 (dd, J = 254.4, J = 6.1 Hz, 2 C), 151.0 (2ϫ),

126.7 (2ϫ), 126.2 (t, J = 11.9 Hz), 124.2, 120.1, 114.4 (m*, 2 C),

101.2 (t, J = 20.1 Hz), 94.6, 85.7, 84.4 (t, J = 2.7 Hz), 79.2 (t, J =

19.0 (2ϫ) ppm. ¹⁹F NMR (CDCl₃):

δ = –107.5 (d, J =

7.7 Hz) ppm. HRMS: calcd. for C₁₁₈H₁₄₇F₄S₂1704.0875 3.7 Hz), 72.4, 67.5, 34.7 (2ϫ), 31.7, 31.2 (6ϫ), 26.7, 18.6 ppm. ¹⁹

F

[M + H]⁺; found 1704.0904. (m*: The complex multiplicity of this

signal is attributed to coupling with fluorine).

NMR (CDCl₃): δ = –107.0 (d, J = 7.4 Hz) ppm. HRMS: calcd. for

[C₃₀H₃₁BrF₂]*⁺508.1572 [M]*⁺; found 508.1572. (m*: The complex

multiplicity of this signal is attributed to coupling with fluorine).

Compound 47: 3,5-Di-tert-butylbromobenzene (2.00 g, 7.43 mmol)

was dissolved in THF (35 mL) and Et₃N (4.14 mL, 29.7 mmol) was

added, followed by PdCl₂(PPh₃)₂(209 mg, 0.30 mmol), CuI (57 mg,

0.30 mmol) and TMSA (3.09 mL, 22.3 mmol). The resulting solu-

tion was stirred at 60 °C under argon for two days. The mixture

was then diluted in CH₂Cl₂and washed with saturated aqueous

NH₄Cl, and the organic layer was dried with Na₂SO₄. The solvents

were removed under reduced pressure and the crude product was

purified by flash chromatography on silica gel with pure hexanes

Compound 50: Compound 49 (1.13 g, 2.22 mmol) and potassium

thioacetate (760 mg, 6.65 mmol) in THF (10 mL) was heated at

60 °C overnight. The mixture was then diluted in CH₂Cl₂and

washed with water. The organic layer was dried with Na₂SO₄and

the solvents were removed under reduced pressure. The crude prod-

uct was purified by flash chromatography on silica gel with EtOAc/

hexanes (1%) as eluent to provide the title compound 50 (807 mg,

1

72% yield) as a yellow solid. H NMR (CDCl₃): δ = 7.47 (s, 1 H

as eluent to provide the title compound 47 (1.99 g, 94% yield) as a ar.), 7.41 (m, 2 H ar.), 6.90 (d, J = 7.4 Hz, 2ϫHC–CF), 2.90 (t, J

white solid. ¹H NMR (CDCl₃): δ = 7.37 (m, 1 H ar.), 7.32 (m, 2 H

ar.), 1.31 (s, 6ϫCH₃), 0.26 (s, TMS-C) ppm. ¹³C NMR (CDCl₃):

= 6.9 Hz, CH₂–S), 2.42 (t, J = 6.6 Hz, CϵC–CH₂), 2.31 (s, CH₃–

C=O), 1.69 (m, 4 H alkyl), 1.32 (brs, 6ϫCH₃) ppm. ¹³C NMR

Eur. J. Org. Chem. 2010, 3049–3067

www.eurjoc.org

3065

D. Thibeault, M. Auger, J.-F. Morin

FULL PAPER

(CDCl₃): δ = 195.5, 163.5 (dd, J = 254.6, J = 6.1 Hz, 2 C), 151.1

NP2: HAuCl₄: 191 mg, 0.49 mmol; TOAB: 664 mg, 1.22 mmol;

(2ϫ), 126.8 (2ϫ), 126.4 (t, J = 12.0 Hz), 124.2, 120.3, 114.4 (m*, compound 2: 200 mg, 0.24 mmol; NaBH₄: 184 mg, 4.86 mmol.

2 C), 101.2 (t, J = 19.9 Hz), 94.9, 85.7, 84.4 (t, J = 2.8 Hz), 79.1

(t, J = 3.6 Hz), 72.4, 67.6, 34.8 (2ϫ), 31.2 (6ϫ), 30.5, 28.8, 28.5,

27.3, 19.0 ppm. ¹⁹F NMR (CDCl₃): δ = –107.2 (d, J = 7.5 Hz) ppm.

HRMS: calcd. for [C₃₂H₃₄F₂OS]*⁺504.2293 [M]*⁺; found

504.2309. (m*: The complex multiplicity of this signal is attributed

to coupling with fluorine).

Amount of nanoparticles recovered after purification: 136 mg.

NP3: HAuCl₄: 138 mg, 0.35 mmol; TOAB: 477 mg, 0.87 mmol;

compound 3: 306 mg, 0.17 mmol; NaBH₄: 132 mg, 3.49 mmol.

Amount of nanoparticles recovered after purification: 79 mg.

NP4: HAuCl₄: 174 mg, 0.44 mmol; TOAB: 603 mg, 1.10 mmol;

compound 4: 200 mg, 0.22 mmol; NaBH₄: 167 mg, 4.41 mmol.

Amount of nanoparticles recovered after purification: 121 mg.

Compound 8: Compound 50 (736 mg, 1.46 mmol) was dissolved in

a solution of HCl/MeOH (1 , 6 mL) with THF (6 mL) and stirred

4 h at 50 °C. A saturated solution of I₂in CH₂Cl₂was added to

this solution until persistence of the brown colouration. The mix-

ture was stirred for 15 min, diluted in CH₂Cl₂and washed with

saturated aqueous Na₂S₂O₃until the disappearance of the brown

colour. The organic layer was dried with Na₂SO₄and the solvents

were removed under reduced pressure. The crude product was puri-

fied by preparative TLC on silica gel with EtOAc͞hexanes (2%) as

eluent to provide the title compound 8 (503 mg, 75% yield) as a

yellow solid, together with residual compound 50(65 mg, 9% yield).

¹H NMR (CDCl₃): δ = 7.47 (s, 2 H ar.), 7.40 (m, 4 H ar.), 6.90 (d,

J = 7.4 Hz, 4ϫHC–CF), 2.72 (t, J = 7.1 Hz, 2ϫCH₂–S), 2.43 (t,

J = 6.9 Hz, 2ϫCϵC–CH₂), 1.83 (m, 4 H alkyl), 1.70 (m, 4 H

alkyl), 1.32 (brs, 12ϫCH₃) ppm. ¹³C NMR (CDCl₃): δ = 163.5

(dd, J = 254.7, J = 6.2 Hz, 4 C), 151.1 (4ϫ), 126.8 (4ϫ), 126.4 (t,

J = 11.8 Hz, 2 C), 124.2 (2ϫ), 120.2 (2ϫ), 114.4 (m*, 4 C), 101.2

(t, J = 20.0 Hz, 2 C), 95.0 (2ϫ), 85.7 (2ϫ), 84.5 (t, J = 2.6 Hz, 2

C), 79.2 (t, J = 3.8 Hz, 2 C), 72.4 (2ϫ), 67.6 (2ϫ), 38.2 (2ϫ), 34.8

(4ϫ), 31.2 (12ϫ), 28.2 (2ϫ), 27.0 (2ϫ), 19.1 (2ϫ) ppm. ¹⁹F NMR

(CDCl₃): δ = –107.1 (d, J = 7.3 Hz) ppm. HRMS: calcd. for

C₆₀H₆₃F₄S₂923.4302 [M + H]⁺; found 923.4311. (m*: The complex

multiplicity of this signal is attributed to coupling with fluorine).

NP5: HAuCl₄: 179 mg, 0.46 mmol; TOAB: 622 mg, 1.14 mmol;

compound 5: 243 mg, 0.23 mmol; NaBH₄: 172 mg, 4.55 mmol.

Amount of nanoparticles recovered after purification: 143 mg.

NP6: HAuCl₄: 308 mg, 0.78 mmol; TOAB: 1.07 g, 1.96 mmol; com-

pound 6: 266 mg, 0.39 mmol; NaBH₄: 296 mg, 7.84 mmol. Amount

of nanoparticles recovered after purification: 245 mg.

NP7: HAuCl₄: 162 mg, 0.41 mmol; TOAB: 561 mg, 1.03 mmol;

compound 7: 350 mg, 0.21 mmol; NaBH₄: 155 mg, 4.11 mmol.

Amount of nanoparticles recovered after purification: 114 mg.

NP8: HAuCl₄: 256 mg, 0.65 mmol; TOAB: 888 mg, 1.62 mmol;

compound 8: 300 mg, 0.32 mmol; NaBH₄: 246 mg, 6.50 mmol.

Amount of nanoparticles recovered after purification: 205 mg.

Supporting Information (see footnote on the first page of this arti-

cle): ¹H and ¹³C NMR spectra of all new compounds, transmission

electron microscope (TEM) images, thermogravimetric analysis

(TGA) and calculation details of the organic/gold ratio for the

nanoparticles.

Acknowledgments

General Procedure for the Preparation of NP1–NP8: A solution of

tetraoctylammonium bromide (0.034 , 5 equiv.) in toluene was

added to a stirred solution of HAuCl₄(0.032 , 2 equiv.) in nano-

pure H₂O and stirred vigorously for 15 min. The two phases were

separated and the aqueous phase was discarded. The disulfide

(1 equiv.) in a minimal volume of toluene was then added to the

brown organic phase and stirred for 5 min. A freshly prepared solu-

tion of NaBH₄(0.39 , 20 equiv.) in nanopure H₂O was then

quickly added and the resulting mixture was vigorously stirred for

one hour. The two phases were then separated and the black or-

ganic layer was washed once with H₂SO₄(0.1 ), once with NaOH

(0.1 ) and once with H₂O. The solvent was removed in vacuo until

≈3 mL of toluene remained. The crude nanoparticles were then pre-

cipitated with ethanol (≈150 mL) and centrifuged for 15 min,

washed with ethanol and dissolved again in a minimal volume of

toluene (≈2 mL), and the purification process was then repeated

again as described previously to provide the gold nanoparticles

NP1–NP4 as black solids. These products were further purified by

size exclusion chromatography (SEC) on Bio-Beads^®S-X1 (Bio-

Rad Laboratories, Hercules, USA) with toluene as eluent. The gold

nanoparticles NP5–NP8 were precipitated once and purified on

Bio-Beads^®S-X1 as described previously. For NP5–NP6, a further

purification step was as follows: the compounds were each dis-

solved in a minimal amount of CH₂Cl₂(≈2 mL), precipitated in

hexanes (≈ 200 mL) and centrifuged for 15 min to provide gold

nanoparticles NP5 and NP6 as black solids.

This work has been supported by the Université Laval, the Fonds

québécois de la recherche sur la nature et les technologies

(FQRNT) through the Team research program, the Centre québé-

cois sur les matériaux fonctionnels (CQMF) and the Canadian

Foundation for Innovation (CFI). We thank Pierre Audet for his

help with NMR analysis and Jean-Benoît Giguère for his help in

the synthesis of a few compounds.

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Published Online: April 26, 2010

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3067

Article Doi

Synthesis of fluorine-containing molecular rotors and their assembly on gold nanoparticles

DOI: 10.1002/ejoc.201000252

Source and publish data:

Authors:

Article abstract of DOI:10.1002/ejoc.201000252

Full text of DOI:10.1002/ejoc.201000252

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