Ferrocenyl derivatives with one, two, or three sulfur-containing arms for self-assembled monolayer formation

Article abstract of DOI:10.1021/jo9909812

Self-assembled monolayers of electroactive molecules can form on gold electrodes if the molecules include a sulfur-containing group to coordinate with the gold surface. We have prepared a molecule with a tripod of sulfur groups that has the potential of fixing the geometry of the molecule relative to the gold surface. The target (3) contained the good one-electron donor ferrocene connected through a benzene spacer to an isobutane tripod, with each arm of the tripod ending in a methylthio group. Analogous compounds with one (1) and two (2) coordinating arms were also prepared.

Full text of DOI:10.1021/jo9909812

VOLUME 65, NUMBER 8
APRIL 21, 2000
© Copyright 2000 by the American Chemical Society
Articles
F er r ocen yl Der iva tives w ith On e, Tw o, or Th r ee Su lfu r -Con ta in in g
Ar m s for Self-Assem bled Mon ola yer F or m a tion
J ian Hu and Daniell Lewis Mattern*
Chemistry Department, University of Mississippi, University, Mississippi 38677
Received J une 21, 1999
Self-assembled monolayers of electroactive molecules can form on gold electrodes if the molecules
include a sulfur-containing group to coordinate with the gold surface. We have prepared a molecule
with a tripod of sulfur groups that has the potential of fixing the geometry of the molecule relative
to the gold surface. The target (3) contained the good one-electron donor ferrocene connected through
a benzene spacer to an isobutane tripod, with each arm of the tripod ending in a methylthio group.
Analogous compounds with one (1) and two (2) coordinating arms were also prepared.
In tr od u ction
nonuniform shape may form less-ordered SAMs. The
electroactive end groups may be able to approach closer
to the electrode, as has been suggested for silane-tethered
groups,6 perhaps at tilt domain boundaries.7 Such excur-
sions could influence the observed electrochemistry.
Molecules that include a sulfur-containing group, such
as thiols (R-S-H), disulfides (R-S-S-R), or sulfides
(R-S-R), can spontaneously form self-assembled mono-
layers (SAMs) on a gold surface when the sulfur coordi-
nates with the gold.1 Long alkyl chains tend to promote
stability in SAMs, by increasing interchain van der Waals
forces.2 These chains can also serve as tethers for
electroactive end groups, such as ferrocene, which can
be detected electrochemically by using the gold surface
as an electrode.3 Ferrocene is an excellent one-electron
donor which exhibits a reversible cyclic voltammogram.4
We sought to prepare a molecule with a tripod of
anchoring sulfur groups. By using a rigid isobutane
tripod, the electroactive group would be fixed in distance
and in geometry, with its molecular axis perpendicular
to the electrode surface. Three-point anchoring, rather
than van der Waals interactions, would then control the
geometry of the SAM. For comparison, we also sought
analogues with two coordinating anchors,8 whose move-
ment would be constrained to swinging back and forth
in one dimension, and analogues with one anchor, which
would enjoy the capability of complete two-dimensional
movement. Variations in electrochemical properties could
be sought with such compounds.
We have been interested in preparing SAMs of elec-
troactive donor-σ-acceptor systems. One question that
arises is the orientation of the electroactive group with
respect to the surface. Measurements indicate that
simple alkanethiols form closely packed monolayers at
a 30° angle to the gold surface.5 But molecules of
(5) Bryant, M. A.; Pemberton, J . E. J . Am. Chem. Soc. 1991, 113,
8284.
(6) Murray, R. W. Acc. Chem. Res. 1980, 13, 135.
(7) Chidsey, C. E. D.; Bertozzi, C. R.; Putvinski, T. M.; Mujsce, A.
M. J . Am. Chem. Soc. 1990, 112, 4301.
(8) Wooster, T. T.; Gamm, P. R.; Geiger, W. E.; Oliver, A. M.; Black,
A. J .; Craig, D. C.; Paddon-Row, M. N. Langmuir 1996, 12, 6616.
(1) Dubois, L. H.; Nuzzo, R. G. Annu. Rev. Phys. Chem. 1992, 43,
437.
(2) Bain, C. D.; Whitesides, G. M. J . Am. Chem. Soc. 1989, 111, 7164.
(3) He, Z.; Bhattacharyya, S.; Cleland, W. E. J .; Hussey, C. L. J .
Electroanal. Chem. 1995, 397, 305.
(4) Gritzer, G.; Kuta, J . Pure Appl. Chem. 1984, 56, 461.
10.1021/jo9909812 CCC: $19.00 © 2000 American Chemical Society
Published on Web 03/28/2000

2278 J . Org. Chem., Vol. 65, No. 8, 2000
Hu and Mattern
Sch em e 1
We report here the preparation of a ferrocene anchored
by three methyl sulfide groups (3), along with the
analogous two- and one-arm anchored sulfides (2 and 1,
respectively). Thiols would be preferable coordinating
groups, as they form SAMs much more robustly than
sulfides;9-12 however, they can be difficult to work with
due to their tendency to oxidize or act as nucleophiles.
This turned out to be the case here: although we were
able to prepare the corresponding one-armed thiol 4, we
have so far been unable to isolate the two-armed thiol 5
in pure form.
Sch em e 2
A three-armed thiol (6) based on a tripropyl methyl-
amine tripod has been used to attach polyalanine to a
gold surface.13 Further, a derivative with three of these
tripods attached to one polyalanine provided nine points
of attachment. The extra methylenes in these compounds
allow potential flexibility that is avoided in compound 3.
Resu lts a n d Discu ssion
Initial attempts to connect ferrocene directly to an
isobutane tripod failed and prompted us to include a
benzene ring as a spacer. To attach the ferrocene donor
to the phenyl spacer, we employed the diazonium cou-
pling reaction of aryl diazonium salts to ferrocene/
ferrocenium mixtures in sulfuric acid.14 Thus, 2-(4-
ferrocenylphenyl)ethanol (10) could be prepared from
diazotized 8, which was obtained by catalytic hydrogena-
tion of 7 (Scheme 1). Alcohol 10 was converted to bromide
11 with bromine and triphenylphosphine,15 and thence
to the thiouronium salt 12. Conversion of 12 to the one-
armed analogues methyl sulfide 1 and thiol 4 proceeded
in good yields as shown in Scheme 1.
tion16a,b of phenylmalonate (13) gave 2-phenyl-1,3-pro-
panediol, which was protected18 as the diacetate 14.
Following nitration, the acetate groups were removed to
improve solubility for the aqueous ferrocene coupling
reaction, giving diol 15. Catalytic hydrogenation of the
nitro group, diazotization, and ferrocene coupling gave
16. Conversion of hydroxyls to bromides proceeded as
before to give 17, but the direct displacement of bromide
with thiomethoxide was much preferable in this case to
the thiourea method in producing the two-armed bis-
sulfide ferrocene 2. An apparent side reaction in this last
step was elimination of HBr, leading to the formation of
Scheme 2 shows the route to two-armed analogues.
Literature procedures were followed to obtain 14: reduc-
(9) J ung, C.; Dannenberger, O.; Xu, Y.; Buck, M.; Grunze, M.
Langmuir 1998, 14, 1103.
(10) Troughton, E. B.; Bain, C. D.; Whitesides, G. M.; Nuzzo, R. G.;
Allara, D. L.; Porter, M. D. Langmuir 1988, 4, 365.
(11) Trevor, J . L.; Lykke, K. R.; Pellin, M. J .; Hanley, L. Langmuir
1998, 14, 1664.
(12) Zhong, C.-J .; Brush, R. C.; Anderegg, J .; Porter, M. D. Langmuir
1999, 15, 518.
(13) Whitesell, J . K.; Chang, H. K. Science 1993, 261, 73.
(14) Weinmayr, V. J . Am. Chem. Soc. 1955, 77, 3012.
(15) Wiley, G. A.; Hershkowitz, R. L.; Rein, B. M.; Chung, B. C. J .
Am. Chem. Soc. 1964, 86, 964.
(16) (a) Searles, S., J r.; Nickerson, R. G.; Witsiepe, W. K. J . Org.
Chem. 1959, 24, 1839. (b) Marshall, P. A.; Prager, R. H. Aust. J . Chem.
1977, 30, 141.
(17) Adkins, H.; Billica, H. R. J . Am. Chem. Soc. 1948, 70, 3121.
(18) Guanti, G.; Narisano, E.; Podgorski, T.; Thea, S.; Williams, A.
Tetrahedron 1990, 46, 7081.

Ferrocenyl Derivatives
J . Org. Chem., Vol. 65, No. 8, 2000 2279
Sch em e 3
alkene 19, which was removed chromatographically.
At high reaction temperatures, 19 became the major
product.
Treatment of the dibromide 17 with thiocyanate pro-
duced the bisthiocyanate 18, and reduction with LiAlH4
gave a crude product whose spectra were consistent with
the two-armed dithiol ferrocene 5. However, chromato-
graphic purification attempts appeared to cause poly-
merization and/or cyclization, and we were unable to
isolate pure 5 for analysis.
Difficulty might be expected in using these straight-
forward synthetic approaches to incorporate the three
required sulfur groups into a sterically congested target
like 3. SN2 reactions capable of placing three sulfurs in
the required neopentyl positions are known, however. For
example, excess methanethiolate can convert 20 (X ) Cl19
or X ) Br20) to 21; ethanethiolate can also be used.21
Thiocyanate can displace the tosylates of 23 to form 24.22
Similarly, the hexasulfide 25 has been prepared from 23
for use as a hexa-coordinating “supertripodal” ligand.23,24
Even the congested, chiral tris-sulfide 22 can be prepared
by sequential displacement steps on a suitable precur-
sor.25 These successes suggested that a route to 3 through
the key tribromo intermediate 30 might be feasible.
coupling reaction of the corresponding diazonium salt did
not result in significant amounts of product 34. A likely
cause of the difficulty was the low solubility of 35 in the
aqueous coupling medium.
We then attempted to perform the coupling before the
thiocyanations. Hydrogenation of 30, followed by diazo-
tization and ferrocene coupling, resulted in a <2% yield
of 33, again probably due to solubility problems, and
analysis of the product mixture following treatment of
33 with thiocyanate indicated cleavage of the ferrocene
from the benzene spacer group rather than formation of
34.
The Wittig reaction26 of 4-nitrobenzaldehyde with
(methoxymethyl)triphenylphosphonium chloride gave ni-
trophenylacetaldehyde 28, which was subjected to a
Tollens condensation27-29 (a double aldol addition of
formaldehyde followed by a Cannizzaro reduction with
formaldehyde as the hydride donor) to give the triol 29,30
as shown in Scheme 3. Bromination proceeded as before
to give the tribromide 30.
We next attempted to perform the ferrocene coupling
on the aniline derived from triol 29; its improved water
solubility allowed isolation of the coupled product 32 in
20% yield. However, attempted bromination of 32 re-
sulted in decomposition of the ferrocene, as indicated by
loss of ferrocene signals in the NMR spectrum of crude
material.
Displacement of the three bromines with thiocyanate
was successful, giving 31, and reduction to the aniline
35 was accomplished with SnCl2. However, the ferrocene
(19) Brodersen, K.; Roelz, W.; J ordan, G.; Gerbeth, R.; Ellermann,
J . Chem. Ber. 1978, 111, 132.
(20) Ali, R.; Higgins, S. J .; Levason, W. Inorg. Chim. Acta 1984, 84,
65.
(21) Riley, D. P.; Oliver, J . D. Inorg. Chem. 1986, 25, 1814.
(22) Kolomyjec, C.; Whelan, J .; Bosnich, B. Inorg. Chem. 1983, 22,
2343.
(23) Thorne, C. M.; Rawle, S. C.; Admans, G. A.; Cooper, S. R. Inorg.
Chem. 1986, 25, 3848.
(24) Cooper, S. R. Pure Appl. Chem. 1990, 62, 1123.
(25) Soltek, R.; Huttner, G.; Zsolnai, L.; Driess, A. Inorg. Chim. Acta
1998, 269, 143.
(26) Taber, D. F.; Mack, J . F.; Rheingold, A. L.; Geib, S. J . J . Org.
Chem. 1989, 54, 3831.
(27) Cho, S. D.; Kim, I. D.; J o, J . H.; Chung, J . S. Taehan Hwahakhoe
Chi 1990, 34, 501; Chem. Abstr. 1991, 114, 81127u.
(28) Newkome, G. R.; Baker, G. R. Org. Prep. Proced. Int. 1986, 18,
117.
Thiomethoxide was capable of adding three methylthio
groups to 30 (Scheme 4). (A side reaction appeared to be
denitration, judging from the shielded aromatic NMR
signals of a byproduct chromatography fraction; nitro
groups are known to be potential leaving groups in
nucleophilic aromatic substitutions.31) Reduction with
SnCl2,32 diazotization, and ferrocene coupling provided
the target three-armed ferrocene 3, albeit in low yield.
Analysis of self-assembled monolayers of 1-3 will be
reported elsewhere.
(29) Weibull, B.; Matell, M. Acta Chem. Scand. 1962, 16, 1062.
(30) Analysis of carbon for 29 was 0.49 below the calculated value.
(31) Beck, J . R. Tetrahedron 1978, 34, 2057.
(32) Bellamy, F. D.; Ou, K. Tetrahedron Lett. 1984, 25, 839.

2280 J . Org. Chem., Vol. 65, No. 8, 2000
Hu and Mattern
1H NMR (CDCl3): δ 7.29 (d, J ) 8.2 Hz, 2H), 7.11 (d, J ) 8.2
Hz, 2H), 4.60 (t, J ) 1.9 Hz, 2H), 4.27 (t, J ) 1.9 Hz, 2H). 4.02
(s, 5H), 2.85 (m, 2H), 2.75 (m, 2H), 2.12 (s, 3H). Anal. Calcd
for C19H20FeS: C, 67.86; H, 5.99; S, 9.53. Found: C, 67.80; H,
6.03; S, 9.38.
Sch em e 4
2-(4-F er r ocen ylp h en yl)-1-eth a n eth iol (4). Compound 11
(1.85 g, 5.01 mmol) and thiourea (761 mg, 10.0 mmol) were
dissolved in 20 mL of DMSO. The solution was stirred for 1
day at room temperature. NaOH (20%) was added dropwise
until the pH was 11-12. The solution was then acidified with
hydrochloric acid and extracted with Et2O. After rotary
evaporation of the solvent, 4 was recrystallized from hexanes
at -78 °C to give a 71% yield of a dark red solid, mp 59-60
1
°C. H NMR (CDCl3): δ 7.42 (d, J ) 8.1 Hz, 2H), 7.12 (d, J )
8.1 Hz, 2H), 4.61 (t, J ) 1.7 Hz, 2H), 4.30 (t, J ) 1.7 Hz, 2H),
4.04 (s, 5H), 2.97-2.79 (m, 4H), 1.41 (t, 1H). IR (KBr): 2562
cm-1. Anal. Calcd for C19H18FeS: C, 67.09; H, 5.63; S, 9.95.
Found: C, 67.36; H, 5.37; S, 9.94.
2-(4-Nit r op h en yl)p r op a n e-1,3-d iol (15). 1,3-Diacetoxy-
2-phenylpropane18 (14, 1.18 g, 5.00 mmol), trifluoroacetic
anhydride (4.20 g, 20.0 mmol), and ammonium nitrate (405
mg, 5.06 mmol) were put in 10 mL of dry CHCl3 and reacted
at 0 °C for 2 h and then at room temperature for 10 h. The
mixture was poured into ice-water and extracted with CHCl3.
The organic layer was dried with MgSO4 and concentrated by
rotary evaporation, giving a 96% crude yield of 1,3-diacetoxy-
2-(4-nitrophenyl)propane.
The crude nitroarene was dissolved in 20 mL of 5% NaOH
in 50% aqueous ethanol, refluxed for 1 day, and extracted with
EtOAc. The organic layer was dried with MgSO4, concentrated
by rotary evaporation, and purified by column chromatography
(1:3 EtOAc:hexanes) to give a 40% yield of 15 (based on
compound 14) as a white solid, mp 98-99 °C. 1H NMR (DMSO-
d6): δ 8.15 (d, J ) 8.6 Hz, 2H), 7.53 (d, J ) 8.6 Hz, 2H), 4.70
(t, J ) 5.2 Hz, 2H), 3.74-3.61 (m, 4H), 2.98 (m, 1H). IR: 3538,
3254 cm-1. Anal. Calcd for C9H11NO4: C, 54.82; H, 5.62; N,
7.10. Found: C, 55.12; H, 5.50; N, 7.12.
Exp er im en ta l Section
Gen er a l Meth od s. Starting materials and reagents were
purchased from Aldrich unless otherwise noted. Column
chromatography was performed using E. Merck silica gel, 230-
400 mesh. Melting points are not corrected. Elemental analy-
ses were carried out by Desert Analytics, Tucson, AZ.
2-(4-F er r ocen ylp h en yl)-1-eth a n ol (10). 2-(4-Nitrophen-
yl)-1-ethanol (7, 16.7 g, 100 mmol) was dissolved in 150 mL of
EtOH. Pt/C (100 mg) was added, and the mixture was shaken
under 40-60 psi of H2 for 2 h. The catalyst was removed by
filtration, and the solvent was removed by rotary evaporation,
giving a quantitative crude yield of 2-(4-aminophenyl)-1-
ethanol (8). This material was dissolved in 30% H2SO4, and
sodium nitrite (8.3 g, 0.12 mol) in water was added dropwise
at 0 °C. After 15 min of stirring, the resulting diazonium salt
(9) was used as follows.
A mixture of 37.2 g (200 mmol) of ferrocene in 50 mL of
concd H2SO4 was left standing overnight and then was poured
into sufficient ice water to make the H2SO4 concentration 30%.
The diazonium salt solution was added to the resulting blue
ferrocenium solution. The solution was kept at 0 °C for 15 h
and then was neutralized with 20% sodium hydroxide and
extracted with EtOAc. The organic layer was dried with
MgSO4 and concentrated by rotary evaporation. Column
chromatography (1:3 EtOAc:hexanes) gave a 40% yield of 10
as a dark red powder, mp 93-94 °C. 1H NMR (CDCl3): δ 7.43
(d, J ) 8.2 Hz, 2H), 7.13 (d, J ) 8.2 Hz, 2H), 4.61 (t, J ) 1.8
Hz, 2H), 4.30 (t, J ) 1.8 Hz, 2H), 4.15 (s, 1H), 4.04 (s, 5H),
3.87 (t, J ) 6.4 Hz, 2H), 2.85 (t, J ) 6.4 Hz, 2H). IR: 3252
cm-1. The analytical sample was crystallized from hexanes.
Anal. Calcd for C18H18FeO: C, 70.61; H, 5.93. Found: C, 70.88;
H, 5.83.
2-(4-F er r ocen ylp h en yl)p r op a n e-1,3-d iol (16). Treatment
of 3.55 g (18.0 mmol) of nitroarene 15 with the procedure used
to prepare 10 gave a 24% yield of dark red 16, mp 135-136
1
°C. H NMR (CDCl3): δ 7.43 (d, J ) 8.1 Hz, 2H), 7.15 (d, J )
8.1 Hz, 2H), 4.62 (t, J ) 1.8 Hz, 2H), 4.32 (t, J ) 1.8 Hz, 2H),
4.05 (s, 5H), 3.98 (m, 4H), 3.10 (m, 1H), 1.99 (t, J ) 5.6 Hz,
2H). IR: 3265 cm-1. Anal. Calcd for C19H20FeO2: C, 67.88; H,
6.00. Found: C, 68.18; H, 6.00.
2-(4-F er r ocen ylp h en yl)-1,3-d ibr om op r op a n e (17). To a
suspension of triphenylphosphine (1.44 g, 5.49 mmol) in 10
mL of dry acetonitrile was added bromine (0.88 g, 5.5 mmol)
in 5 mL of acetonitrile dropwise under nitrogen at 0 °C. After
10 min, the diol 16 (603 mg, 1.79 mmol) in 5 mL of acetonitrile
was added dropwise. The resulting solution was refluxed for
1.5 h and then extracted with hexanes. The organic layer was
concentrated by rotary evaporation and purified by column
chromatography (1:20 EtOAc:hexanes) to give a 90% yield of
2-(4-F er r ocen ylp h en yl)-1-br om oeth a n e (11). To a sus-
pension of 3.94 g (15.0 mmol) of triphenylphosphine in 30 mL
of dry acetonitrile was added bromine (2.40 g, 15.0 mmol)
dropwise at 0 °C under nitrogen. After 10 min, 3.06 g (10.0
mmol) of 10 in 10 mL of acetonitrile was added dropwise. The
resulted solution was refluxed for 4 h, and then extracted with
hexanes. Column chromatography (1:20 EtOAc:hexanes) gave
1
17 as a dark red solid, mp 145-146 °C. H NMR (CDCl3): δ
7.45 (d, J ) 8.3 Hz, 2H), 7.14 (d, J ) 8.3 Hz, 2H), 4.62 (t, J )
1.8 Hz, 2H), 4.31 (t, J ) 1.8 Hz, 2H), 4.04 (s, 5H), 3.77 (m,
4H), 3.36 (m, 1H). Anal. Calcd for C19H18Br2Fe: C, 49.40; H,
3.93; Br, 34.59. Found: C, 49.73; H, 3.83; Br, 34.44.
1
a 90% yield of 11 as a dark red solid, mp 76-77 °C. H NMR
2-(4-F er r ocen ylp h en yl)-1,3-d ith iocya n op r op a n e (18).
Compound 17 (500 mg, 1.08 mmol) and potassium thiocyanate
(1.94 g, 20.0 mmol) were refluxed in 20 mL of ethylene glycol
dimethyl ether for 4 h. Water (100 mL) was added, and the
mixture was extracted with EtOAc. Rotary evaporation of the
MgSO4-dried organic phase and purification by column chro-
matography (1:4 EtOAc:hexanes) afforded a 41% yield of 18,
mp 154-155 °C. 1H NMR (CDCl3): δ 7.45 (d, J ) 8.3 Hz, 2H),
7.14 (d, J ) 8.3 Hz, 2H), 4.62 (t, J ) 1.8 Hz, 2H), 4.31 (t, J )
1.8 Hz, 2H), 4.04 (s, 5H), 3.83-3.71 (m, 4H), 3.40-3.31 (m,
1H). IR (KBr): 2148, 2072. Anal. Calcd for C21H18FeN2S2: C,
60.29; H, 4.34; N, 6.60; S, 15.33. Found: C, 60.17; H, 4.27; N,
6.54; S, 15.32.
(CDCl3): δ 7.42 (d, J ) 8.2 Hz, 2H), 7.13 (d, J ) 8.2 Hz, 2H),
4.62 (t, J ) 1.6 Hz, 2H), 4.31 (t, J ) 1.6 Hz, 2H), 4.04 (s, 5H),
3.58 (t, J ) 7.7 Hz, 2H), 3.14 (t, J ) 7.7 Hz, 2H). The analytical
sample was crystallized from hexanes at -78 °C. Anal. Calcd
for C18H17BrFe: C, 58.58; H, 4.64; Br, 21.65. Found: C, 58.80;
H, 4.65; Br, 21.30.
2-(4-F er r ocen ylp h en yl)-1-(m eth ylth io)eth a n e (1). Bro-
mide 11 (369 mg, 1.00 mmol) and thiourea (761 mg, 10.0 mmol)
were dissolved in 5 mL of DMSO. After 15 h, the mixture was
cooled on an ice bath and basified to pH 11-12 with 10%
NaOH. After 15 min at room temperature, the flask was
returned to the ice bath, and 1.0 mL (16 mmol) of CH3I was
added dropwise. After 2 h at room temperature, the mixture
was extracted with Et2O; rotary evaporation of the solvent
gave an 85% yield of 1 as a dark red powder, mp 79-80 °C.
2-(4-Fer r ocen ylph en yl)-1,3-bis(m eth ylth io)pr opan e (2).
Sodium thiomethoxide (350 mg, 5.00 mmol) was added to a
solution of dibromide 17 (924 mg, 2.00 mmol) in 10 mL of DMF.

Ferrocenyl Derivatives
J . Org. Chem., Vol. 65, No. 8, 2000 2281
After standing at room temperature overnight, the solution
was poured into 100 g of ice and 100 mL of 10% HCl. The
mixture was extracted with Et2O, and the organic layer was
dried with MgSO4, concentrated by rotary evaporation, and
purified by column chromatography (1:100 EtOAc:hexanes) to
give a 34% yield of 2 as a dark red solid, mp 85-86 °C. 1H
NMR (CDCl3): δ 7.43 (d, J ) 8.2 Hz, 2H), 7.15 (d, J ) 8.2 Hz,
2H), 4.62 (t, J ) 1.9 Hz, 2H), 4.29 (t, J ) 1.9 Hz, 2H), 4.03 (s,
5H), 3.00-2.83 (m, 5H), 2.03 (s, 6H). 13C NMR (CDCl3): δ
140.3, 137.9, 127.6, 126.2, 85.2, 69.6, 68.8, 66.4, 45.2, 39.9
(CH2), 16.3. Anal. Calcd for C21H24FeS2: C, 63.63; H, 6.10; S,
16.18. Found: C, 63.73; H, 6.14; S, 16.20. Evidence for the
formation of 2-(4-ferrocenylphenyl)-3-methylthio-1-propene
(19) as a byproduct was afforded by 1H NMR (CDCl3) of a
chromatography fraction: δ 7.43 (m, 4H), 5.50 (d, J ) 1.1 Hz,
1H), 5.16 (d, J ) 1.1 Hz, 1H), 4.63 (t, J ) 1.9 Hz, 2H), 4.31 (t,
J ) 1.8 Hz, 2H), 4.05 (s, 5H), 3.58 (s, 2H), 2.06 (s, 3H).
4-Nitr op h en yleth a n a l (28). To a suspension of (meth-
oxymethyl)triphenylphosphonium chloride (6.51 g, 19.0 mmol)
in 50 mL of dry Et2O at 0 °C was added phenyllithium (10
mL, 18 mmol, 1.8 M in hexanes) dropwise. After standing at
room temperature for 4 h, the mixture was cooled again to 0
°C and 4-nitrobenzaldehyde (26, 907 mg, 6.00 mmol) was
added in 10 mL of dry THF. After standing for 12 h at room
temperature, the mixture was filtered and the filtrate was
concentrated by rotary evaporation. The enol ether residue (27)
was dissolved in 20 mL of EtOH, and 5 mL of 10% HCl was
added. This mixture was refluxed for 3 h and then was
extracted with Et2O. The organic layer was dried with MgSO4,
concentrated by rotary evaporation, and purified by column
chromatography to give a 35% yield of 28 as a pale yellow solid,
potassium thiocyanate (9.72 g, 100 mmol) were heated at 100
°C in DMF for 10 h. Water (100 mL) was added, and the
mixture was extracted with EtOAc. The organic layer was
dried with MgSO4 and concentrated by rotary evaporation. The
residue was crystallized from 1:1 EtOAc:hexanes to give 31
in 51% yield, mp 163-164 °C. 1H NMR (DMSO-d6): δ 8.78 (d,
J ) 8.9 Hz, 2H), 7.94 (d, J ) 8.9 Hz, 2H), 3.96 (s, 6H). IR
(KBr): 2151 cm-1. Anal. Calcd for C13H10N4O2S3: C, 44.56; H,
2.88; N, 15.99; S, 27.45. Found: C, 44.60; H, 2.71; N, 15.78; S,
27.68.
2-(4-F er r ocen ylp h en yl)-2-(h yd r oxym et h yl)p r op a n e-
1,3-d iol (32). The procedure used to prepare compound 10
(varied as follows: the diazonium salt was prepared in 25%
H2SO4, and the ferrocenium solution was diluted to make 20%
H2SO4) converted 1.24 g (5.50 mmol) of 29 to 32 in 20% yield;
1
mp 161-162 °C. H NMR (DMSO-d6): δ 7.42 (d, J ) 8.5 Hz,
2H), 7.33 (d, J ) 8.5 Hz, 2H), 4.70 (t, J ) 1.8 Hz, 2H), 4.42 (t,
J ) 5.2 Hz, 3H), 4.30 (t, J ) 1.8 Hz, 2H), 4.03 (s, 5H), 3.72 (d,
J ) 5.2 Hz, 6H). IR (KBr): 3344 cm-1
.
2-(4-Nit r op h en yl)-1,3-b is(m et h ylt h io)-2-(m et h ylt h io-
m eth yl)p r op a n e (36). The procedure that was used to
prepare compound 2 was employed on 2.16 g (5.19 mmol) of
tribromide 30, except that the reaction conditions were 0 °C
for 3 h. Pale yellow needles of 36 were obtained in 43% yield,
1
mp 51-52 °C. H NMR (CDCl3): δ 8.22 (d, J ) 9.0 Hz, 2H),
7.57 (d, J ) 9.0 Hz, 2H), 3.17 (s, 6H), 2.02 (s, 9H). Anal. Calcd
for C13H19NO2S3: C, 49.18; H, 6.03; S, 30.30. Found: C, 49.13;
H, 6.01; S, 30.37.
2-(4-F er r ocen ylp h en yl)-1,3-b is(m et h ylt h io)-2-(m et h -
ylth iom eth yl)p r op a n e (3). Tin(II) chloride dihydrate (4.51
g, 20.0 mmol) was added to a solution of 635 mg of nitroarene
36 (2.00 mmol) in 20 mL of dry EtOH. After the solution was
refluxed for 12 h, 100 mL of 5% EDTA (aq) was added and
the mixture was extracted with EtOAc. The organic layer was
dried with MgSO4 and concentrated by rotary evaporation to
give a 66% yield of crude aniline 37.
1
mp 84-85 °C (lit.33 mp 85-86 °C). H NMR (CDCl3): δ 9.82
(t, J ) 1.6 Hz, 1H), 8.25 (d, J ) 1.8 Hz, 2H), 7.41 (d, J ) 1.8
Hz, 2H), 3.88 (d, J ) 1.6 Hz, 2H).
2-(4-Nit r op h en yl)-2-(h yd r oxym et h yl)p r op a n e-1,3-d i-
ol (29). (4-Nitrophenyl)ethanal (28, 519 mg, 3.14 mmol),
calcium hydroxide (934 mg, 12.6 mmol), and paraformaldehyde
(378 mg, 12.6 mmol) were refluxed in 30 mL of THF for 3 days.
The mixture was filtered, and the filtrate was concentrated
by rotary evaporation and purified by column chromatography
(3:1 EtOAc:hexanes) to give a 37% yield of 29 as an orange
The ferrocene coupling procedure used to prepare compound
10 converted 37 to 3 as a dark red gum in 15% yield based on
1
36. H NMR (CDCl3): δ 7.45 (d, J ) 8.6 Hz, 2H), 7.29 (d, J )
8.6 Hz, 2H), 4.64 (t, J ) 1.9 Hz, 2H), 4.30 (t, J ) 1.9 Hz, 2H),
4.00 (s, 5H), 3.16 (s, 6H), 1.98 (s, 9H). Anal. Calcd for C23H28
-
1
FeS3: C, 60.51; H, 6.18; S, 21.07. Found: C, 60.76; H, 6.33; S,
21.44.
powder, mp 115-118 °C. H NMR (DMSO-d6): δ 8.14 (d, J )
9.0 Hz, 2H), 7.71 (d, J ) 9.0 Hz, 2H), 4.60 (t, J ) 5.1 Hz, 3H),
3.73 (d, J ) 5.1 Hz, 6H). IR: 3487, 3413, 3325 cm-1. Anal.
Calcd for C10H13NO5: C, 52.86; H, 5.77; N, 6.16. Found: C,
52.37; H, 5.49; N, 6.00.
Ack n ow led gm en t. We thank Dr. Charles Hussey
(in whose laboratory Zhuoli He conducted preliminary
CV experiments); Dr. Charles Panetta and Dr. Walter
Cleland for helpful discussions; and the National Sci-
ence Foundation and the State of Mississippi for finan-
cial support through the Mississippi EPSCoR program.
2-(4-Nit r op h en yl)-1,3-d ib r om o-2-(b r om om et h yl)p r o-
p a n e (30). The procedure used to prepare compound 17
converted 1.39 g (6.13 mmol) of 29 to 30 as a white powder in
1
68% yield, mp 124-125 °C. H NMR (CDCl3): δ 8.27 (d, J )
8.9 Hz, 2H), 7.50 (d, J ) 8.9 Hz, 2H), 3.95 (s, 6H). Anal. Calcd
for C10H10Br3NO2: C, 28.88; H, 2.42; Br, 57.64; N, 3.37.
Found: C, 28.88; H, 2.23; Br, 57.96; N, 3.25.
Su p p or tin g In for m a tion Ava ila ble: Experimental de-
tails for the preparation of compound 14 from 13 and the
attempted syntheses of compounds 5 and 34; IR spectral data
for all compounds prepared. This material is available free of
charge via the Internet at http://pubs.acs.org.
2-(4-Nit r op h en yl)-1,3-d it h iocya n o-2-(t h iocya n om et h -
yl)p r op a n e (31). Compound 30 (2.30 g, 5.53 mmol) and
(33) Weerman, R. A. J ustus Liebigs Ann. Chem. 1913, 401, 1.
J O9909812