Regioselective Chlorocarbonylation of Polybenzyl Cores and Functionalization Using Dendritic and Organometallic Nucleophiles

Article abstract of DOI:10.1021/jo9914622

Regiospecific chlorocarbonylation of the polybenzyl cores PhCH₂CH₂Ph, C₆(CH₂CH₂Ph)₆, 7, and {CH(CH₂Ph)₂}₄-1,2,4,5-C₆H ₂, 8, in the para position of the benzyl groups gives the chlorocarbonyl derivatives 2, 9, and 10, respectively, in good yields. The octachlorocarbonyl derivative 10 reacts with Newkome's aminotripod NH₂C(CH₂OCH₂CH₂CN)₃ to give the 24-nitrile dendrimer 13 which is characterized by its molecular peak in the MALDITOF mass spectrum and with (5-aminopentyl)-1-ferrocene to give the octaferrocene complex 14. Reactions of 2, 9, and 10 with sodium methanolate in methanol gives the methyl esters 3, 15, and 16 which are reduced by LiAlH₄ to the primary alcohols 4, 17, and 18; reactions of these alcohols with NaI and BF₃·Et₂O yield the iodomethyl derivatives 5, 19, and 20. The organoiron nucleophile [Fe^IICp(η⁵-C₆Me₅CH ₂)], 1, reacts with 5, 19, and 20 leading to C-C bond formation and recovery of the aromatic structure of the ligand. This reaction with 5 yields a soluble complex, [Fe^IICp(η⁶-C₆Me₅CH ₂CH₂C₆H₄CH₂-)] ₂, 6, in which the two redox groups, separated by 14 carbon atoms, are independent, being reversibly reduced at approximately the same potential in an overall two-electron wave recorded by cyclic voltammetry. The analogous reaction with 19 and 20, however, gave almost insoluble hexa- and octa-iron complexes 21 and 22 with mediocre purities.

Full text of DOI:10.1021/jo9914622

1996
J . Org. Chem. 2000, 65, 1996-2002
Regioselective Ch lor oca r bon yla tion of P olyben zyl Cor es a n d
F u n ction a liza tion Usin g Den d r itic a n d Or ga n om eta llic
Nu cleop h iles
Christine Vale´rio,† Franc¸oise Moulines,† J aime Ruiz,† J ean-Claude Blais,‡ and Didier Astruc*,†
Groupe de Chimie Supramole´culaire des Me´taux de Transition, LCOO, UMR CNRS No. 5802,
Universite´ Bordeaux I, 33405 Talence Cedex, France, and Laboratoire de Chimie Structurale Organique
et Biologique, Universite´ Paris VI, France
Received September 15, 1999
Regiospecific chlorocarbonylation of the polybenzyl cores PhCH2CH2Ph, C6(CH2CH2Ph)6, 7, and
{CH(CH2Ph)2}4-1,2,4,5-C6H2, 8, in the para position of the benzyl groups gives the chlorocarbonyl
derivatives 2, 9, and 10, respectively, in good yields. The octachlorocarbonyl derivative 10 reacts
with Newkome’s aminotripod NH2C(CH2OCH2CH2CN)3 to give the 24-nitrile dendrimer 13 which
is characterized by its molecular peak in the MALDI TOF mass spectrum and with (5-aminopentyl)-
1-ferrocene to give the octaferrocene complex 14. Reactions of 2, 9, and 10 with sodium methanolate
in methanol gives the methyl esters 3, 15, and 16 which are reduced by LiAlH4 to the primary
alcohols 4, 17, and 18; reactions of these alcohols with NaI and BF3‚Et2O yield the iodomethyl
derivatives 5, 19, and 20. The organoiron nucleophile [FeIICp(η5-C6Me5CH2)], 1, reacts with 5, 19,
and 20 leading to C-C bond formation and recovery of the aromatic structure of the ligand. This
reaction with 5 yields a soluble complex, [FeIICp(η6-C6Me5CH2CH2C6H4CH2-)]2, 6, in which the two
redox groups, separated by 14 carbon atoms, are independent, being reversibly reduced at
approximately the same potential in an overall two-electron wave recorded by cyclic voltammetry.
The analogous reaction with 19 and 20, however, gave almost insoluble hexa- and octa-iron
complexes 21 and 22 with mediocre purities.
In tr od u ction
1). Likewise, the CpFe+-induced octamethylation, octaal-
lylation, and octabenzylation of durene were achieved
selectively (eq 2).4
Among the plethora of organotransition-metal activa-
tion types,1 a number of them have now enriched the field
of organic synthesis2 and molecular engineering.3 An
efficient C-H activation/C-C bond formation system
that we disclosed two decades ago was the CpFe+-induced
hexamethylation of hexamethylbenzene using excess
t-BuOK and CH3I,4a a reaction further extended to
hexabenzylation, hexaalkylation, and hexaallylation4b (eq
† Universite´ Bordeaux I.
‡ Universite´ Paris VI.
(1) (a) Crabtree, R. H. The Organometallic Chemistry of the Transi-
tion Metals, 2nd ed.; Wiley: New York, 1994. (b) Collman, J . P.;
Hegedus, L. S. Norton, J . R.; Finke R. G. Principles and Applications
of Organotransition Metal Chemistry, 2nd ed.; University Science
Books: Mill Valey, CA, 1987. (c) Elschenbroich, Ch.; Salzer, A.
Organometallics, 2nd ed.; VCH: Weinheim, 1992.
(2) (a) Hegedus, L. S. Transition Metals in the Synthesis of Complex
Organic Molecules; University Sciences Books: Mill Valley, CA, 1994.
(b) Harrington, P. H. Transition Metals in Total Synthesis; Wiley: New
York, 1990. (c) McQuillin, F. J .; Parker, D. G.; Stephenson, G. R.
Transition Metal Organometallics for Organic Synthesis; Cambridge
University Press: Cambridge, 1991. (d) Organometallics in Synthesis;
Schlosser, M., Ed.; Wiley: New York, 1994.
These reactions are easy to carry out and proved useful
to synthesize star cores, star polymers, and metalloden-
drimers.4b,c Thus, hexa- and octabenzyl cores are readily
accessible by this method which may be attractive if
subsequent functionalization can be achieved regiospe-
cifically. In part of a preliminary communication, we
disclosed the regiospecific chlorocarbonylation of an
octabenzyl core resulting from the CpFe+-induced octa-
benzylation of durene.4c We now detail this reaction here
with di-, hexa-, and octabenzyl cores,4f together with the
reactions of these polychlorocarbonylated cores with
amines and alcohol nucleophiles. We have chosen these
nucleophiles as a function of their use either to introduce
an organic dendron or a redox-active organometallic
group. Direct reaction of the polychlorocarbonyl core with
useful amines containing a dendron or a ferrocene
termini is indeed achieved; alternatively, reaction with
methanol followed by reduction and iodation introduces
the iodomethyl function in benzylic position which allows
(3) (a) Lehn, J .-M. Supramolecular Chemistry; Concepts and Per-
spectives; VCH: Weinheim, 1995. (b) Vo¨gtle, F. Supramolecular
Chemistry, 2nd ed.; Wiley: Chichester, 1993.
(4) (a) Astruc, D.; Hamon, J .-R.; Althoff, G.; Roma´n, E.; Batail, P.;
Michaud, P.; Mariot, J .-P.; Varret, F.; Cozak, D. J . Am. Chem. Soc.
1979, 101, 5445. (b) recent reviews: Vale´rio, C.; Alonso, E.; Ruiz, J .;
Fillaut, J .-L.; Guittard, J .; Blais, J .-C.; Astruc, D. Pure Appl. Chem.
1998, 70, 809. Astruc, D.; Blais, J .-C.; Cloutet, E.; Djakovitch, L.;
Rigaut, S.; Ruiz, J .; Sartor, V.; Vale´rio, C. Top. Curr. Chem. 2000, in
press. (c) Preliminary communication of the chlorocarbonylation reac-
tion of 8: Vale´rio, C.; Alonso, E.; Ruiz, J .; Blais, J .-C.; Astruc, D. Angew.
Chem., Int. Ed. Engl. 1999, 38, 1747. (d) Astruc, D.; Hamon, J .-R.;
Roman, E.; Michaud, P. J . Am. Chem. Soc. 1981, 103, 7502. (e) Trujillo,
H. A.; Casado, C. M.; Ruiz, J .; Astruc, D. J . Am. Chem. Soc. 1999,
121, 5674. (f) Vale´rio, C.; Gloaguen, B.; Fillaut, J .-L., Astruc, D. Bull.
Soc. Chim. Fr. 1996, 133, 101.
10.1021/jo9914622 CCC: $19.00 © 2000 American Chemical Society
Published on Web 03/16/2000

Regioselective Chlorocarbonylation
J . Org. Chem., Vol. 65, No. 7, 2000 1997
further reaction with the nucleophile [FeIICp(η5-C6Me5-
CH2)], 1.4d This nucleophile, isoelectronic to ferrocene, is
obtained by the reaction of O2 with the 19-electron
complex [FeICp(C6Me6)] or by deprotonation of the 18-
electron cation [FeIICp(C6Me6)]+.4d It allows us to intro-
duce iron sandwiches with a permethylated arene ring
on the termini of star branches. The complex 1 is a good
nucleophile, but also an excellent base (the pKa of the
acid [FeIICp(C6Me6)][PF6] is 28.2 in DMSO),4e so that it
cannot be used in positions where dehydrohalogenation
can occur such as the termini of alkyl chains. Organo-
metallic stars and metallodendrimers are now a quickly
growing area.5,6 Various stars and dendritic structures
are already known with ferrocene termini.7-12
Sch em e 1
Resu lts
We have carried out the Friedel-Crafts chlorocarbo-
nylation of diphenyl-1,2-ethane, a commercial compound,
as a model reaction. The aromatic Friedel-Crafts chlo-
rocarbonylation is a known reaction13 first reported by
Neubert.13a The reaction product 2 was also published
by Taramu using another route via the diacid.14 It is an
air-stable, white powder which is not very sensitive to
hydrolysis in the solid state and was obtained in 94%
yield from of diphenyl-1,2-ethane. It was esterified with
sodium methanolate in methanol which gave the diester
3 in 90% yield. Then, the diester was reduced to the diol
4 in 90% yield using LiAlH4 in ether/THF (12 h, 40 °C).
This diol is a white hygroscopic powder which is soluble
in THF and alcohols. The compound 4 was then treated
with NaI/BF3‚Et2O in acetonitrile (12h, RT) to give the
diiodomethyl compound 5 in 79% yield. The reaction of
5 with 1 was carried out in THF (12 h, RT) which gave
a 31% yield of the air-stable, yellow dinuclear complex 6
after chromatographic purification. The complex 6 is well
soluble in dichloromethane and acetonitrile. In cyclic
voltammetry, it shows a single chemically- and electro-
chemically reversible two-electron wave at -1.88 V vs
FeCp20/+ in DMF, using ferrocene as internal standard.15
These reactions are summarized in Scheme 1.
a
(i) (COCl)2, AlCl3, CH2Cl2, 15 °C, 1 h; (ii) CH3OH, 2 days, RT;
(iii) LiAlH4, 40 °C, ether/THF, 14 h; (iv) NaI, BF3‚Et2O, CH3CN,
RT, 12 h; (v) [FeIICp(η5-C6Me5CH2)], THF, 12 h.
Given the success of this scheme on the model diphen-
ylethane, it was applied to the hexabenzyl and octabenzyl
cores 7 and 8 available by the CpFe+-induced hexaben-
zylation of hexamethylbenzene and octabenzylation of
durene, respectively. The chlorocarbonylation proceeds
well with 7 and 8, and the hexa- and octachlorocarbonyl
compounds 9 and 10 were both obtained in 86% yields.
The polychlorocarbonyl derivatives 9 and 10 are white
powders which are much more sensitive toward hydroly-
sis in air than 2, however, so that great care must be
taken during the workup (see Experimental Section). For
instance, NMR spectra recorded in DMSO-d6 show
resonances that are attributed to the presence of the
polycarboxylic acids 11 and 12 due to fast hydrolysis by
residual water in DMSO-d6. Thus 9 and 10 must be
quickly used for reactions with alcohol and amine nu-
cleophiles.
To construct dendrimers rapidly, reaction of 10 was
carried out with Newkome’s aminotripod NH2C(CH2-
OCH2CH2CN)316 in CH2Cl2 in the presence of NEt3. This
reaction gave the 24-nitrile dendrimer 13 in 61% yield
after chromatographic purification, which was character-
ized by its molecular peak in the MALDI-TOF mass
spectrum (m/z ) 3328.57 [M + Na+], see Figure 1).
Similarly, reaction of 10 with (5-aminopentyl)-1-fer-
(5) (a) Dendrimers: Newkome, G. R., Moorefield, C. N., Vo¨gtle, F.
Dendritic Molecules: Concepts, Syntheses and Perspectives; VCH: New
York, 1996. (b)Topics in Current Chemistry; Vo¨gtle, F., Ed.; Springer-
Verlag: Berlin, 1998; Vol. 197. (c) Astruc, D.; Ardoin, N. Bull. Soc.
Chim. Fr. 1995, 132, 875. (d) See also ref 6.
(6) Comprehensive reviews on metallodendrimers: (a) Newkome,
G. R.; He, E.; Moorefield, C. N. Chem. Rev. 1999, 99, 1689. (b)
Hearshaw, M. A.; Moss, J . R. Advances in Macromolecules; Newkome,
G., Ed.; J AI Press Inc: Stamford, CT, 1999; Vol. 4, pp 1-60.
(7) (a) Cuadrado. I.; Mora´n, M.; Casado, C.-M.; Alonso, B.; Losada,
J . Organometallics 1996, 15, 5278. (b) Cuadrado. I.; Mora´n, M.; Casado,
C.-M.; Alonso, B.; Losada, J . In Advances in Dendritic Macromolecules;
Newkome, G., Ed.; J AI Press: Greenwich, CT, 1996; Vol. 3, pp 151-
195. (c) Cuadrado. I.; Mora´n, M.; Casado, C.-M.; Alonso, B.; Losada,
J .; Belsky, V. J . Am. Chem. Soc. 1997, 119, 7613. (d) Losada, J .,
Cuadrado. I.; Mora´n, M.; Casado, C.-M.; Alonso, B.; Barranco, M. Anal.
Chim. Acta 1997, 338, 191. (e) Takada, K.; Diaz, D. J .; Abrun˜a, H. D.;
Cuadrado. I.; Casado, C.-M.; Alonso, B.; Mora´n, M.; Losada, J . J . Am.
Chem. Soc. 1997, 119, 10763. (f) Castro, R.; Cuadrado. I.; Casado, C.-
M.; Alonso, B.; Casado, C.-M.; Mora´n, M.; Kaifer, A. E. J . Am. Chem.
Soc. 1997, 119, 5760.
(8) Ko¨llner, C., Pugin, B., Togni, A. J . Am. Chem. Soc. 1999, 120,
10274.
(9) J utzi, P.; Batz, C.; Neumann, B.; Stammler, H.-G. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 2118.
(10) Deschenaux, R.; Serrano, E.; Levelut, A. M. Chem. Commun.
1997, 1577.
(11) Kayser, B.; Altman, J .; No¨th, H.; Knizek, J .; Beck, W. Eur. J .
Inorg. Chem. 1998, 1791.
(12) Shu, C.-F., Shen, H.-M. J . Mater. Chem. 1997, 7, 47.
(13) (a) Neubert, M. E.; Fishel, D. L. Mol. Cryst. Liq. Cryst. 1979,
53, 101. (b) Osman, M. A. Helv. Chim. Acta 1982, 65, 2448.
(14) Taramu, V. Rev. Chim. 1989, 486.
(15) For the determination of the number of electrons involved in a
single reversible polyelectron wave, see: (a) Flanagan, J . B.; Margel,
S.; Bard, A. J .; Anson, F. C. J . Am. Chem. Soc. 1957, 79, 376. (b)
Moulines, F.; Djakovitch, L.; Boese, R.; Gloaguen, B.; Thiel, W.; Fillaut,
J .-L.; Delville, M.-H.; Astruc, D. Angew. Chem., Int. Ed. Engl. 1993,
32, 1075. (c) Astruc, D. Electron Transfer and Radical Processes in
Transition Metal Chemistry; VCH: New York, 1995; Chapter 2.

1998 J . Org. Chem., Vol. 65, No. 7, 2000
Vale´rio et al.
F igu r e 1. MALDI TOF mass spectrum of the 24-CN dendrimer 13. The molecular peak is M + Na+ ) at 3328.57 (isotopic
distribution on the right).
rocene17 gave the orange powdery octaferrocene deriva-
proposed structures 21a (Cp ring in 1), 21b (n-butylCp
ring in 1b instead of the Cp ring in 1) and 22. In 22 (Cp
ring in 1), the analysis shows that about 6% of iron
sandwich is missing. These insoluble materials can be
considered as polydisperse polymers, although it appears
that, statistically, a weak proportion of the material must
have the complete hexa-or octametallic structure.
tive 14 in 81% yield (Scheme 2).1
Reactions of 9 and 10 with sodium methanolate in
methanol gave the methyl esters 15 and 16 in 85 and
90% yields, respectively. These esters were reduced by
LiAlH4 to the primary alcohols 17 and 18 which were
obtained as white powders in 96 and 85% yields, respec-
tively. Then, reactions of the alcohols 17 and 18 with NaI/
BF3‚Et2O gave, respectively, 85 and 55% yields of the
hexa- and octaiodomethyl derivatives 19 and 20 as white
powders. Finally, reactions between the polyiodo com-
pounds 19 and 20 with 1 in THF gave yellowish powders
which were almost completely insoluble in all solvents
(Scheme 3). The introduction of an n-butyl substituent
on the Cp ring of 1 did not provide a clear improvement
of solubility. Their pale-yellow color and Mo¨ssbauer
Discu ssion
The chlorocarbonylation of polybenzyl stars is an
excellent means of functionalization and further star or
dendritic extension of the cores. What is remarkable and
most useful is the complete regioselectivity in the para
position obtained in all cases, contrary to other electro-
philic aromatic reactions such as chloromethylation and
iodination that have also been probed with 7. It is known
that the aromatic chloromethylation is not regiospecific.19
The selectivity of the bromomethylation reaction is good
under certain conditions,20 but attempts with 7 gave no
reaction. All the organic reactions involved in the chem-
istry described here proceed under smooth conditions and
high yields. Although the polychlorocarbonyl chlorides
are air-sensitive toward hydrolysis, they are free of any
spectra (IS ) 0.56 mm s-1 vs iron; QS ) 2.00 mm s-1
)
are very characteristic of a [FeIICp(η6-C6Me5CH2R)]+
structure. Cyclic voltammetry at 60 °C in DMF showed
0/+
the classical reversible wave at E1/2 ) -1.88 V vs FeCp2
also characteristic of a [FeIICp(η6-C6Me5CH2R)]+ struc-
ture. The number of electrons involved in the reduction
could not be measured, however, because the amount of
solubilized product was uncertain. Although the poly-
nuclear complexes could not be purified otherwise than
by washing the insoluble solids with solvents in order to
remove all the soluble impurities, the elemental analyses
were carried out. They indicate that the number of iron
sandwich units is close to the expected number in the
(18) The oxidation potential of the ferrocene center (0.39 V vs SCE)
is shifted by 150 mV toward cathodic potentials upon addition of 1
equiv of [n-Bu4N] [H2PO4] and by 50 mV with 1 equiv of [n-Bu4N]-
[HSO4]) in CH2Cl2 containing 0.1 M [n-Bu4N][BF4] on Pt electrode
(auxiliary electrode: Pt, reference electrode: SCE, 20 °C, 100 mV/s).
Compare with better dendritic sensors: Vale´rio, C.; Fillaut, J .-L., Ruiz,
J .; Guittard, J .; Blais, J .-C.; Astruc, D. J . Am. Chem. Soc. 1997, 119,
2588.
(19) (a) Belen’kii, L., II.; Vol’kenshtein, Y. B.; Karmanova, I. B. Russ.
Chem. Rev. 1977, 46, 891. (b) Olah, G. A.; Kuhn, S. J . J . Am. Chem.
Soc. 1960, 82, 2380. (c) Gross, H.; Rieche, A.; Matthey, G. Chem. Ber.
1963, 96, 8.
(16) Newkome, G. R.; Lin, X., Young, J . K. Synlett 1992, 53.
(17) (a) (5-Aminopentyl)-1-ferrocene was synthesized from (4-iodo-
pentyl)-1-ferrocene17b by reaction with KCN in DMF at room temper-
ature followed by reduction of the nitrile by LiAlH4 in ether at room
temperature.17c (b) Fillaut, Linares, J .; Astruc, D. Angew. Chem., Int.
Ed. Engl. 1994, 33, 2460. (c) Ruiz, J .; Astruc, D. Unpublished results.
(20) Mitchell, R. H., Iyer, V. S. Synlett 1989, 55.

Regioselective Chlorocarbonylation
J . Org. Chem., Vol. 65, No. 7, 2000 1999
Sch em e 2
a
(i) PhCH2Br, KOH, 10 d, 40 °C; (ii) hνUV-vis (Hg lamp), MeCN, 12 h; (iii) (COCl)2, AlCl3, CH2Cl2, 15 °C, 1 h; (iv) NH2C(CH2OCH2CH2CN)3,
NEt3, CH2Cl2, 10 d, RT; (v) NH2(CH2)5Fc, NEt3, CH2Cl2, RT, 10 d.
impurity after the workup because acidic fractions even-
tually formed (even on a single branch) lead to insoluble
products that are eliminated from the medium. The
MALDI TOF mass spectrum of the 24-nitrile dendrimer
13 obtained indicates that it is remarkably free of defect.
Thus the chlorocarbonylation is a key reaction toward
rapid dendritic syntheses. We have already used it to
synthesize 24-amidoferrene and 24-[Cp*Feη6-(N-alkyl-
aniline)]+ dendrimers which have outstanding properties
of sensors for various anions with dramatic dendritic
effects.4c The octaferrocene derivative 14 obtained by a
similar reaction is another example of sensor. It can be
used for the recognition of the dihydrogenophosphate and
hydrogenosulfate anions by cyclic voltammetry in DMF.
Its sensitivity is not as good as those of 9- and 18-
amidoferrocene dendrimers that have already been re-
ported, however, because the distance between the amido
group and the ferrocene termini is larger than that in
the amidoferrocene dendrimers.15
yields and solubilities of the binuclear product 6 formed.
The fact that only a single two-electron wave is observed
in cyclic voltammetry shows that the two iron centers
are far enough from each other to be completely inde-
pendent (their benzene ligands are separated by 14
carbon atoms) even from the point of view of the
electrostatic factor. Thus, this strategy was successful for
the formation of C-C bonds between a core and the
organometallic synthon. Further exploitation of this
binuclear compound can be envisaged and pursued. A
major drawback in this chemistry, however, is the
insolubility of the hexa- and octametallic complexes 21
and 22 which prevents us from further use of these two
compounds in dendritic chemistry. An initial goal was
to perbenzylate 21 and 22 as in eq 1 in order to develop
the dendritic structures, and this objective was obviously
frustrated by the insolubility of these polymetallic stars.
Fortunately, the reaction of the polychlorocarbonyl de-
rivatives with nucleophiles are not marred by such
problems and can lead to clean dendrimers as exemplified
The reaction of the organoiron nucleophile 1 with the
diiodomethyl derivative is very satisfactory in terms of

2000 J . Org. Chem., Vol. 65, No. 7, 2000
Vale´rio et al.
Sch em e 3
a
(i) (COCl)2, AlCl3, CH2Cl2, 15 °C, 1 h; (ii) CH3OH, 2 days, RT; (iii) LiAlH4, 40 °C, ether/THF, 14 h; (iv) NaI, BF3‚Et2O, CH3CN, RT,
10 d (19) or 18 d (20); (v) [FeIICp(η5-C6Me5CH2)], THF, 3 d.
spectra were recorded with a Brucker AC 200 (200 MHz)
spectrometer. 13C NMR spectra were obtained at 50.327 MHz.
Electronic spectra (UV and visible) were recorded at 20 °C with
10 or 1 mm quartz cells. Care was taken in the cyclic
voltammetry experiments to minimize the effects of solution
resistance on the measurements of peak potentials (the use
of positive feedback iR compensation and dilute solution
(≈10-3 mol/L) maintained currents between 1 and 10 µA). The
additional redox couple [FeCp2]/[FeCp2]+ was used when
possible as a control for iR compensation. Thermodynamic
potentials were recorded with reference to an aqueous SCE
in THF (0.1 M n-Bu4NBF4). The value of the [FeCp2]/[FeCp2]+
redox couple was 0.382 V vs SCE on Pt in MeCN and 0.475 V
vs SCE on Pt in CH2Cl2. The QRE potential was calibrated by
adding the reference couple [FeCp2]/[FeCp2]+. The counter
electrode was platinum. Mo¨ssbauer spectra were recorded with
a 25 mCi 57Co source on Rh, using a symmetric triangular
sweep mode. Elemental analyses were performed by the
Center of Microanalyses of the CNRS at Lyon-Villeurbanne,
France.
here by the reaction of 10 with Newkome’s aminotripod
to give the very useful dendrimer 13.4c
Con clu sion
The cholorocarbonylation of di-, hexa-, and octabenzyl
cores, a remarkably regiospecific reaction, has opened
new synthetic routes toward molecular materials. It is
especially useful as a complement to the well-established
CpFe+-induced perbenzylation of polymethylbenzene de-
rivatives. Examples of the direct use of the polychloro-
carbonylated compounds with amines is provided by the
syntheses of the 24-nitrile dendrimer 13 and the octa-
ferrocene compound 14 using the octachlorocarbonyl
derivative 10. Dimetalation of the linear-chain dichloro-
carbonyl compound 2 using the organoiron synthon 1
gives a stable, soluble complex 6 which is a reservoir of
two electrons at two remote, independent redox centers.
On the other hand, hexa- and octametalation with 1 of
the iodomethylated hexa- and octabenzyl cores leads to
almost insoluble hexa- and octametalated complexes with
mediocre purities.
Syn th esis of th e P olyca r bon yl Ch lor id e Der iva tives
2, 9, a n d 10 a n d P olyca r boxylic Acid s 11 a n d 12. Gen er a l
P r oced u r e. Aluminum chloride (2 equiv per branch) is
introduced into a Schlenk flask and deaerated under vacuum.
Dry, deaerated dichloromethane (6 mL) and then oxalyl
chloride (3 equiv per branch) are added dropwise in 20 min at
15 °C. The polybenzyl derivative in 6 mL dry, deaerated
dichloromethane is introduced dropwise in 1 h, and the
reaction mixture is stirred at 15 °C. Rapid hydrolysis is carried
out by adding a mixture of 120 g ice and 5 g calcium chloride
to the reaction medium at 0 °C. The organic phase is quickly
extracted using dichloromethane at 0 °C and dried over sodium
sulfate, and the cold solvent is removed under vacuum. A white
solid is obtained and stored in the freezer at -20 °C.
Dica r bon yl ch lor id e, 2: from bibenzyl (1 g, 5.59 mmol),
aluminum chloride (2.98 g, 22.4 mmol), and oxalyl chloride
(2.9 mL, 33.5 mmol) is obtained 1.63 g (94% yield) of the known
compound 2 (see ref 14). NMR (CDCl3, δppm); 1H: 2.82 (s, 4H),
7.25-7.87 (AA′BB′ system, 8H); 13C: 37.79, 128.3, 128.1, 129.3,
135.9, 167.0. Infrared (NaCl plates, cm-1): 1770 (νas CdO);
1740 (νs CdO), 1600 (ν CdC Ar).
Exp er im en ta l Section
Gen er a l Da ta . Reagent-grade tetrahydrofuran (THF), di-
ethyl ether, and pentane were predried over Na foil and
distilled from sodium-benzophenone ketyl under argon im-
mediately prior to use. Acetonitrile (CH3CN) was stirred under
argon overnight over phosphorus pentoxide, distilled from
sodium carbonate, and stored under argon. Methylene chloride
(CH2Cl2) was distilled from calcium hydride just before use.
All other chemicals were used as received. The complex 1 was
synthesized according to ref 4d. The hexa-and octabenzyl cores
7 and 8 were prepared according to ref 4f. All manipulations
were carried out using Schlenk techniques or in a nitrogen-
filled Vacuum Atmospheres drylab. Infrared spectra were
recorded in solution (0.1 mm cells with NaCl windows),
between NaCl disks in Nujol, or in KBr pellets. 1H NMR

Regioselective Chlorocarbonylation
J . Org. Chem., Vol. 65, No. 7, 2000 2001
Hexa ca r bon yl ch or id e, 9: from hexaphenylethylbenzene,
7 (0.5 g, 0.711 mmol), aluminum chloride (1.14 g, 8.55 mmol),
and oxalyl chloride (1.12 mL, 12.8 mmol) is obtained 0.661 g
of 9 (86% yield). Infrared (NaCl plates): 1770 (νas CdO); 1740
(νs CdO), 1600 (ν CdC Ar). The compound 9 is then trans-
formed into the hexaacid 11 for further characterization by
dissolving into a saturated aqueous NaOH solution, washing
this solution twice with dichloromethane, precipitation by
addition of a concentrated chlorhydric acid solution, washing
with water, and drying under vacuum. Analysis for 11, calcd
for C60H54O12: C 74.52, H 5.63; found: C 74.24; H 5.60; NMR
(CD3SOCD3, δppm); 1H: 2.82 (broad m, 24H), 7.26-7.87 (AA′BB′
system, 24H), 13.52 (s, 6H); 13C: 31.15, 36.87, 128.35, 128.1,
129.3, 135.9, 146.8, 167.0. Infrared (NaCl plates, ν, cm-1): 3400
(OH), 1680 (CdO), 1600 (CdCAr), 1280 (C-O).
Oct a ca r b on yl ch lor id e 10 a n d oct a ca r b oxylic a cid
12: from tetrakis-1,2,3,4-(1-benzyl-2-phenylethyl)benzene, 8
(0.3035 g, 0.354 mmol), aluminum chloride (0.668 g, 4.26
mmol), and oxalyl chloride (0.75 mL, 6.39 mmol) is obtained
0.481 g of 10 (86% yield). Infrared (NaCl plates): 1770 (νas
CdO), 1740 (νs CdO), 1600 (ν CdC Ar). The compound 10 is
then transformed into the octaacid 12 as described above in
the case of 9 for further characterization. Analysis for 12, calcd
for C74H62O16: C 73.62, H 5.18; found: C 73.51, H 5.12. NMR
(CD3SOCD3, δppm); 1H: 2.35-2.67 (two broad m, 16H), 3.26
(broad m), 6.92-7.7.75 (AA′BB′ system, 32H), 7.05 (s, 2H),
13.40, (s, 8H, CO2H); 13C: 40.90, 42.35, 125.69, 128.8, 129.1,
129.2, 138.4, 145.4, 167.0. Infrared (NaCl plates, ν, cm-1): 3400
(OH), 1680 (CdO), 1600 (CdCAr), 1280 (C-O).
Syn th esis of th e 24-Nitr ile Den d r im er 13. Newkome’s
amino-tripod NH2C(CH2OCH2CH2CN)316 (3.10 g, 10.80 mmol,
2 equiv per branch of 10), synthesized according to ref 16, is
dissolved under argon in 20 mL of dichloromethane in a
Schlenk flask, triethylamine (4 mL, 54 mmol, 10 equiv per
branch of 10) is added, and then the octaacid chloride 10 (0.914
g, 0.675 mmol) is dissolved in 20 mL of dichloromethane and
added to the flask. The reaction mixture is allowed to stir for
10 days at room temperature, the volatiles are removed under
vacuum, and the solid residue is dissolved in dichloromethane.
The organic solution is washed with water to remove triethyl-
amine hydrochloride, dried over sodium sulfate, and filtered,
and the solvent is removed under vacuum. The light-brown
solid residue is chromatographed on an alumina column
(activity II-III) using a dichloromethane/methanol 1/1 mix-
ture, which gives 1.363 g (0.412 mmol, 61% yield) of 13 as an
4.01 (broad m, 54H), 6.66-7.49 (broad s, 8H); 13C: 26.85, 29.4,
30.8, 40.0, 41.4, 41.45, 66.95, 67.9, 68.4, 77.2, 125.9, 127.0,
129.0, 132.4, 137.5, 143.0, 167.2. Infrared (KBr plates, ν, cm-1):
3310 (amide NH), 3070 (CHFc), 2920 (νas CH2), 2840 (νs CH2),
2250 (nitrile CN), 1625 (amide CdO), 1610 (CdCAr), 1540
(CH2), 1290 (amide C-N), 1100 (ether C-O).
Syn th eses of th e P olym eth yl Ester s 3, 15, a n d 16.
Gen er a l P r oced u r e. Under argon is progressively introduced
sodium metal (1.5 equiv per branch) into a Schlenk flask
containing 30 mL of freshly distilled methanol. When all
sodium has reacted, this solution is transferred into another
Schlenk flask containing the polycarbonyl chloride derivative,
and the reaction mixture is stirred for 2 days at room
temperature. Methanol is removed under vacuum, the white
solid residue is dissolved in methyl acetate, this solution is
washed with an aqueous solution saturated with sodium
chloride, the organic layer is dried over sodium sulfate and
filtered, the solvent is removed under vacuum, and the off-
white solid residue is dissolved in the minimum of dichlo-
romethane and precipitated using excess pentane. After
leaving the flask overnight at -20 °C, the ester is obtained as
a white solid by filtration.
Diester 3: from 2 (1.9 g, 6.19 mmol) and Na (0.427 g, 6.19
mmol), a 90% yield of 3 is obtained (1.66 g, 5.57 mmol). NMR
(CDCl3, δppm), 1H: 2.78 (s, 4H), 3.96 (s, 6H), 7.25-8.02 (AA′BB′
system, 8H); 13C: 37.4, 52.2, 128.1, 128.5, 130.1, 136.5, 168.7.
Infrared (NaCl plates, ν, cm-1): 1720 (CdO), 1600 (CdCAr),
1260 (C-O).
Hexa ester 15: from 9 (0.5595 g, 0.52 mmol) and Na (0.107
g, 4.67 mmol) is obtained a 85% yield of 15 (0.461 g, 0.439
mmol). Anal. Calcd for C66H66O12: C 75.41, H 6.33. Found: C
75.33, H 6.40. NMR (CDCl3, δppm), 1H: 2.91-2.98 (two complex
m, 24H), 3.95 (s, 18H), 7.26-8.03 (AA′BB′ system, 24H); 13C:
32.4, 37.80, 52.15, 128.1, 128.5, 130.1, 136.5, 147.1, 168.8.
Infrared (NaCl plates, ν, cm-1): 2920 (CHAr), 1720 (CdO), 1610
(CdCAr), 1270 (C-O).
Octa ester 16: from 10 (0.4195 g, 0.309 mmol) and Na
(0.071 g, 3.71 mmol) is obtained a 90% yield of 16 (0.371 g,
0.281 mmol). Anal. Calcd for C82H78O16
: C 74.63, H 5.96.
Found: C 74.61, H 5.98. NMR (CDCl3, δppm), 1H: 2.38-2.56
(two complex m, 16H), 3.26 (quintuplet, 4H), 3.74 (s, 24H),
6.75-7.82 (AA′BB′ system, 32H), 7.19 (s, 27); 13C: 41.7, 41.9,
52.0, 125.9, 128.4, 129.2, 129.7, 138.95, 145.1, 166.7. Infrared
(NaCl plates, ν, cm-1): 2920 (CHAr), 1720 (CdO), 1600 (Cd
C
Ar), 1260 (C-O).
off-white hygroscopic powder. Analysis calcd for C178H210
34N32: C 63.89, H 6.36, found: C 63.77, H 6.48. NMR (CDCl3,
ppm), 1H: 1.92-2.45 (broad d, CH2, 16H), 2.53 (broad t, 48H),
-
Syn th eses of th e P olyols. Gen er a l P r oced u r e. Under
O
δ
argon, a suspension of LiAlH4 (2.5 equiv per branch ester) in
15 mL of freshly distilled ether is refluxed for 3 h in a Schlenk
flask, and then the ester in 15 mL of freshly distilled THF is
added by cannula at room temperature. The reaction mixture
is refluxed for 2 h, LiAlH4 (2.5 equiv per branch ester) is added
at room temperature to the reaction mixture which is then
refluxed for 12 h, and LiAlH4 is hydrolyzed at room temper-
ature by dropwise addition of an aqueous solution saturated
with sodium sulfate. The white precipitates of Al(OH)3 and
LiOH are extracted using 6 × 50 mL of a methanol/THF
mixture. The solvent is removed under vacuum, leaving a
white hygroscopic solid which is dissolved in a minimum of
methanol and reprecipitated by addition of ether. After stand-
ing at -20 °C overnight, the polyol, a white powdery solid, is
filtered.
Diol 4: from the ester 3 (1.37 g, 4.59 mmol) and LiAlH4 (2
× 0.528 g, 2 × 22.96 mmol) is obtained the alcohol 4 (0.945 g,
3.90 mmol) in 85% yield. NMR (CD3COCD3, δppm), 1H: 2.78
(s, 4H), 4.57 (s, 6H), 7.11-7.24 (AA′BB′ system, 8H); 13C: 37.4,
65.1, 128.4, 128.9, 138.8, 140.53. Infrared (NaCl plates, ν,
cm-1): 3350 (free OH), 3380 (bound OH), 2900 (CHAr), 2830
(CH2), 1610 (CdCAr), 1010 (C-O).
3.35 (broad m, 4H), 3.61 (broad t, 48H), 3.83 (s, 48H), 6.50
(broad s, 8H), 6.95 (broad s, 2H), 6.78-7.60 (AA′BB′ system,
32H); 13C: 18.8, 41.45, 41.5, 50.0, 65.8, 69.0, 118.3, 120.0,
127.2, 129.5, 132.6, 138.5, 144.2, 167.9. Infrared (NaCl plates,
ν, cm-1): 3410 (free amide NH), 3320 (bound amide NH), 3050
(CHAr), 2920 (νas CH2), 2880 (νs CH2), 2250 (nitrile CN), 1650
(amide CdO), 1610 (CdCAr), 1290 (amide C-N), 1100 (ether
C-O).
Syn th esis of th e Octa fer r ocen e 14. Under argon are
introduced (5-amino-pentyl)-1-ferrocene17 (1.01 g, 3.72 mmol,
2 equiv per branch) in 20 mL of dichloromethane and triethyl-
amine (2.7 mL, 18.6 mmol, 10 equiv per branch) and 10 (0.315
g, 0.233 mmol) in 20 mL of dichoromethane into a Schlenk
flask, and the reaction mixture is allowed to stir for 10 days
at room temperature. Then, the volatiles are removed under
vacuum, and the orange solid residue is dissolved in 20 mL of
dichloromethane. This solution is washed with water to
eliminate triethylamine hydrochloride and the excess amine
and dried over sodium sulfate, and the solvent is removed
under vacuum. The orange solid is dissolved in 10 mL of
dichloromethane and 50 mL of pentane are added to precipi-
tate 14 as an orange powder which is dried under vacuum
(0.613 g, 0.190 mmol, 81% yield from 10). Anal. Calcd for
Hexol 17: from the ester 15 (1.335 g, 1.27 mmol) and
LiAlH4 (2 × 0.438 g, 2 × 19.04 mmol) is obtained the hexol 17
(1.007 g, 1.14 mmol) in 90% yield. Anal. Calcd for C60H66O6:
C 81.60, H 7.53. Found: C 81.55, H 7.57. NMR (CD3OD, δppm),
1H: 2.72-2.87 (two complex m, 24H), 4.57 (s, 18H), 7.11-7.24
(AA′BB′ system, 24H); 13C: 33.7, 38.7, 65.2, 128.4, 129.3, 137.7,
C
194H214O8N8Fe8: C 70.51, H 6.77, N 3.39, Fe 13.52. Found:
C 70.41, H 6.73, N 3.57, Fe 13.26. NMR (CDCl3, δppm), 1H:1.28-
1.41 (broad m, 48H), 2.24 5 (broad m, 16H), 2.21-2.61 (two
complex m, 16H), 3.27 (broad m, 10H), 3.50 (broad m, 4H),

2002 J . Org. Chem., Vol. 65, No. 7, 2000
Vale´rio et al.
140.5, 142.5. Infrared (NaCl plates, ν, cm-1): 3350 (free OH),
3380 (bound OH), 2900 (CHAr), 1610 (CdCAr), 1010 (C-O).
Octol 18: from the ester 16 (0.904 g, 0.685 mmol) and
LiAlH4 (2 × 0.39 g, 2 × 10.28 mmol) is obtained the alcohol
17 (0.724 g, 0.661 mmol) in 96% yield. Anal. Calcd for
C74H78O8: C 81.14, H 7.18. Found: C 80.87, H 7.45. NMR (CD3-
OD, δppm), 1H: 2.42-2.61 (two complex m, 16H), 3.57 (quin-
tuplet, 4H), 4.46 (s, 16H), 6.83-7.16 (AA′BB′ system, 32H);
13C: 42.5, 44.18, 65.1, 126.2, 127.9, 130.6, 140.3, 140.7, 141.1.
Infrared (NaCl plates, ν, cm-1): 3360 (free OH), 3370 (bound
OH), 2910 (CHAr), 1600 (CdCAr), 1010 (C-O).
Syn th eses of th e P olyiod om eth yl Der iva tives 5, 19,
a n d 20. Gen er a l P r oced u r e. The polyol and sodium iodide
(5 equiv per branch) are added into a flamed Schlenk flask
under argon and deaerated under vacuum, 15 mL of dry
acetonitrile are added, and a solution of BF3‚Et2O (5 equiv.
per branch) in 5 mL of dry acetonitrile is added over 15 min.
The reaction mixture is stirred in the dark at room-temper-
ature all the longer, as the number of branches is higher (0.5
day for 5, 10 days for 19, 18 days for 20). Then, the solvent is
removed under vacuum, and the yellow solid residue is washed
with 4 × 75 mL of dichoromethane. This solution is treated
with an aqueous solution saturated with sodium thiosulfate
to remove iodine, washed with water, and dried over sodium
sulfate, and the solvent is removed under vacuum. The
remaining off-white solid residue is dissolved in the minimum
of dichloromethane; then addition of pentane yields the
polyiodomethyl derivative as a white powdery precipitate
which is filtered.
an aqueous solution saturated with potassium iodide and then
with water, dried over sodium sulfate, and filtered, and the
solvent is removed under vacuum. The yellow solid residue is
chromatographed over a column of neutral activated alumina
which gives 6 as a yellow solid. In the case of polyiron
complexes 21 and 22, these solids are insoluble in dichlo-
romethane and almost insoluble in all the other organic
solvents and water. They are very slightly soluble in DMF and
DMSO upon sonification and warming to 60 °C. So, the solids
are washed with 3 × 30 mL of dichloromethane, filtered, and
dried under vacuum.
Diir on com p lex 6: from 1 (0.660 g, 2.34 mmol) and 5
(0.300 g, 0.65 mmol) is obtained a 31% yield of 6 after
chromatography and reprecipitation from
a concentrated
dichloromethane solution with ether. Anal. Calcd for C50H60I2-
Fe2: C 58.50, H 5.89, Fe 10.88. Found: C 59.18, H 6.32, Fe
10.59. NMR (CD3CN, δppm), 1H: 2.44 (s, 18H), 2.49 (s, 12H),
2.73-2.33 (complex m, 8H), 2.89 (s, 4H), 4.58 (s, 5H), 7.18 (s,
8H); 13C: 17.5, 18.1, 34.25, 35.5, 37.95, 79.2, 100.2, 100.3,
103.2, 129.55-129.75, 139.5, 140.5. Cyclic voltammetry: re-
versible wave (ia/ic ) 1, Epa-Epc ) 60 mV at 20 °C (Epa + Epc
)
/2 ) 1.88V vs ferrocene as internal standard in DMF on Pt.
The number of electrons involved in this wave was determined
vs the intensity of the ferrocene wave, corrected according to
ref 18, which gave 2.00 electrons.
Hexa ir on com p lex 21a : from 19 (0.444 g, 0.288 mmol)
and 1 (0.973 g, 3.45 mmol) is obtained a 44% yield of 6 (0.416
g, 0.128 mmol). Anal. Calcd for C162H192I6Fe6: C 60.13, H 5.98.
Found: C 58.79, H 5.91. Cyclic voltammetry in DMF at 60 °C
on Pt: reversible wave (ia/ic ) 1, Epa - Epc ) 60 mV) at 20 °C,
(Epa + Epc)/2 ) 1.88V vs ferrocene as internal standard.
Mo¨ssbauer spectrum: Isomer shift (IS) vs iron metal ) 0.56
Diiod o 5: from the diol 4 (0.874 g, 3.6 mmol) and NaI (5.41
g, 36 mmol) is obtained a 79% yield of 5 (1.31 g, 2.84 mmol).
Anal. Calcd for C16H16I2: C 41.59, H 3.49. Found: C 41.98, H
1
mm s-1. Quadrupole splitting (QS) ) 2.00 mm s-1
.
3.93. NMR (CDCl3, δppm), H: 2.78 (s, 4H), 4.38 (s, 4H), 7.03-
7.20 (AA′BB′ system, 8H); 13C: 6.1, 37.4, 128.8, 129.0, 137.0,
141.5 (inner CAr q).
Hexa ir on com p lex 21b: from 19 (0.300 g, 0.65 mmol) and
[FeII(η5-n-Bu-C5H4)(η5-C6Me5CH2)], 1b, (0.660 g, 2.34 mmol)
is obtained a 21% yield of 6 (0.500 g, 0.136 mmol) using the
same procedure as above. Anal. Calcd for C186H240I6Fe6: C
62.54, H 6.77. Found: C 65.82, H 7.13, corresponding to 12%
of iron sandwich missing. Cyclic voltammetry in DMF at 60
°C on Pt: reversible wave (ia/ic ) 1, Epa - Epc ) 60 mV) at 20
°C, (Epa + Epc)/2 ) 1.89 V vs ferrocene as internal standard.
Octa ir on com p lex 22: from 20 (0.486 g, 0.246 mmol) and
1 (1.666 g, 5.90 mmol) is obtained a 50.7% yield of 6 (0.528 g,
0.125 mmol). Anal. Calcd for C210H246I8Fe8: C 59.57, H 5.86.
Found: C 61.56, H 6.38, corresponding to 6.5% of iron
sandwich missing. Cyclic voltammetry in DMF at 60 °C on
Pt: reversible wave (ia/ic ) 1, Epa - Epc ) 60 mV) at 20 °C,
(Epa + Epc)/2 ) 1.88 V vs ferrocene as internal standard.
Mo¨ssbauer spectrum: IS vs iron metal ) 0.56 mm s-1; QS )
Hexa iod o 19: from the hexol 17 (0.150 g, 0.164 mmol) and
NaI (0.75 g, 4.93 mmol) is obtained a 85% yield of 19 (0.22 g,
0.142 mmol). Anal. Calcd for C60H60I6: C 48.35, H 4.37.
1
Found: C 48.27, H 4. 08. NMR (CDCl3, δppm), H: 2.83-2.94
(two complex m, 24H), 4.51 (s, 12H), 7.25-7.36 (AA′BB′
system, 24H); 13C: 6.15, 32.4, 37.5, 128.7, 129.1, 136.6, 137.3,
141.9, 142.5.
Octa iod o 20: from the octol 18 (0.724 g, 0.662 mmol) and
NaI (3.968 g, 2.65 mmol) is obtained a 55% yield of 20 (0.722
g, 0.365 mmol). Anal. Calcd for C74H70I8: C 45.01, H 3.57.
Found: C 44.98, H 3.47. NMR (CDCl3, δppm), 1H: 2.37-2.58
(two complex m, 16H), 3.29 (quintuplet, 4H), 4.29 (s, 16H),
6.73-7.17 (AA′BB′ system, 32H), 6.81 (s, 2H); 13C: 6.9, 41.45,
41.8, 126.5, 128.6, 129.8, 137.0, 138.95, 140.0.
Syn th esis of th e P olyir on Com p lexes 6, 21, a n d 22.
Gen er a l P r oced u r e. The iodo derivative is dissolved in 3 mL
of freshly distilled THF, and this solution is introduced under
argon into a Schlenk flask and deaerated. The deep-red
complex [FeIICp(η5-C6Me5CH2)], 1, is prepared under anhy-
drous conditions according to ref 4d in another Schlenk flask
and dissolved in 4 mL of freshly distilled THF, and the THF
solution of the polyiodo derivative is transferred dropwise into
this flask by cannula. A yellow precipitate immediately ap-
pears. The reaction mixture is stirred for 12 h at room
temperature, the solvent is removed under vacuum, the solid
residue is washed with anhydrous pentane under argon to
remove unreacted 1, and dichloromethane is added. In the case
of 6, the solid residue is soluble, the solution is washed with
2.00 mm s-1
.
Ack n ow led gm en t. Financial support from the In-
stitut Universitaire de France, the Centre National de
la Recherche Scientifique, the Ministe`re de la Recherche
et de la Technologie (thesis grant to C.V.), and the
University Bordeaux I is gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: NMR peak assign-
ments for the new compounds. This material is available free
of charge via the Internet at http://pubs.acs.org.
J O9914622