Nucleophilic Aromatic Substitution Reactions for the Synthesis of Ferrocenyl Aryl Ethers

Article abstract of DOI:10.1021/acs.organomet.6b00157

A range of ferrocenyl aryl ethers of type Fc-O-Ar (Fc = Fe(η⁵-C₅H₅)(η⁵-C₅H_nX_4-n); n = 2-4; X = H, P(O)(OEt)₂, SO₂CF₃; Ar = 2,4-(NO₂)₂-C₆H₃, 4-NO₂-C₆H₄) have been successfully prepared by using the nucleophilic aromatic substitution reaction (S_NAr) of Fc-OLi (1a-Li) and electron-deficient aryl fluorides, enabling a new pathway to this rarely described family of organometallic compounds. Initial studies of 1a-Li and o-phosphonato-substituted hydroxyferrocenes (1b-Li) have also been performed, indicating a low nucleophilicity of the oxygen atom. The S_NAr reaction protocol tolerates ortho substituents, e.g. phosphonato and sulfonyl groups, resulting in 1,2-X,O (X = S, P) ferrocenyl ethers that can be obtained in a one-pot synthesis procedure including 1,3-O C anionic phospho- and thia-Fries rearrangements. Within these studies, the first 1,3-diortho-functionalized ferrocenyl aryl ether could be synthesized. An electrochemical study of the redox potentials of the obtained compounds allows conclusions on the reactivity of the varying electronic properties and the electrophilicity of different aryl fluorides and the nucleophilicity of the functionalized hydroxyl ferrocenes, which is directly reflected by the potential of the first ferrocene related redox processes. Chiral-pool-based phosphonates rearrange to the aryl ethers with diastereomeric excesses of 74 and 81% after the anionic Fries rearrangement. The usage of aryl 1,2-/1,3-difluorides resulted in the synthesis of the first examples of bis(FcO)-substituted benzenes. Their electrochemical investigations reveal a splitting of the two redox processes of the ferrocenyls that decreases from 155 mV (1,2-substitution) to 130 mV (1,3-substitution) on the basis of electrostatic interactions.

Full text of DOI:10.1021/acs.organomet.6b00157

Article
pubs.acs.org/Organometallics
Nucleophilic Aromatic Substitution Reactions for the Synthesis of
Ferrocenyl Aryl Ethers
Marcus Korb,† Pieter J. Swarts,‡ Dominique Miesel,† Alexander Hildebrandt,† Jannie C. Swarts,‡
and Heinrich Lang*,†
†Technische Universitat Chemnitz, Faculty of Natural Sciences, Institute of Chemistry, Inorganic Chemistry, D−09107 Chemnitz,
̈
Germany
‡Department of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein, South Africa
S
* Supporting Information
ABSTRACT: A range of ferrocenyl aryl ethers of type Fc−O−Ar (Fc = Fe(η5-
C5H5)(η5-C5HnX4−n); n = 2−4; X = H, P(O)(OEt)2, SO2CF3; Ar = 2,4-
(NO2)2-C6H3, 4-NO2-C6H4) have been successfully prepared by using the
nucleophilic aromatic substitution reaction (SNAr) of Fc−OLi (1a−Li) and
electron-deficient aryl fluorides, enabling a new pathway to this rarely
described family of organometallic compounds. Initial studies of 1a−Li and o-
phosphonato-substituted hydroxyferrocenes (1b−Li) have also been per-
formed, indicating a low nucleophilicity of the oxygen atom. The SNAr reaction
protocol tolerates ortho substituents, e.g. phosphonato and sulfonyl groups,
resulting in 1,2-X,O (X = S, P) ferrocenyl ethers that can be obtained in a one-
pot synthesis procedure including 1,3-O → C anionic phospho- and thia-Fries
rearrangements. Within these studies, the first 1,3-diortho-functionalized
ferrocenyl aryl ether could be synthesized. An electrochemical study of the
redox potentials of the obtained compounds allows conclusions on the
reactivity of the varying electronic properties and the electrophilicity of different aryl fluorides and the nucleophilicity of the
functionalized hydroxyl ferrocenes, which is directly reflected by the potential of the first ferrocene related redox processes.
Chiral-pool-based phosphonates rearrange to the aryl ethers with diastereomeric excesses of 74 and 81% after the anionic Fries
rearrangement. The usage of aryl 1,2-/1,3-difluorides resulted in the synthesis of the first examples of bis(FcO)-substituted
benzenes. Their electrochemical investigations reveal a splitting of the two redox processes of the ferrocenyls that decreases from
155 mV (1,2-substitution) to 130 mV (1,3-substitution) on the basis of electrostatic interactions.
are rather weak ortho-directing groups and predominantly
result in 1,1′-disubstituted ferrocenes, requiring an intensive
purification process to separate the formed compounds.1,2
Ferrocenyl aryl ethers also do not allow for the introduction of
chiral information to the metallocenyl backbone, due to their
missing asymmetric information. Thus, we recently reported on
a new strategy for the synthesis of 1,2-P,O ferrocenes applying a
1,3-O → C anionic phospho-Fries rearrangement.4,5 Starting
from ferrocenyl phosphates, this intramolecular reaction
exclusively results in the formation of 1,2-disubstituted
ferrocenes in high yield at ambient temperature. In addition,
the usage of chiral-pool derived phosphates resulted in a
diastereoselectivity of 95% for the lithiation and rearrangement
process. However, the stereo information could not successfully
be transferred to a substrate within C,C cross-coupling
reactions, when P,O ferrocenes were applied, due to their
sterically nondemanding methoxy substituent.5 Thus, additional
research on the functionalization of the oxygen moiety within
this structural motif is required. For the final conversion of the
INTRODUCTION
■
Ferrocenyl phosphanes have shown a significant increase in the
catalytic activity for molecules containing a further oxygen
donor atom: for example, in the Suzuki−Miyaura reaction for
the synthesis of hindered biaryls.1,2 This enhancement was
ascribed to a better stabilization of the catalytically active
species due to a hemilabile binding of the oxygen atom to the
palladium atom.1 Due to its potential planar chirality, the
ferrocenyl backbone can be combined with a 1,2-substitution
pattern to act as a chiral bidentate ligand.1,3−8 However, the
1,2-P,O motif has rarely been described in the literature, owing
to difficulties in the introduction of the oxygen-containing
substituents. One possible route is adopted from the synthesis
of hydroxyl ferrocene in an Ullmann-type coupling starting
from ferrocenyl halides.9−11 This approach was extended to
aromatic and aliphatic alcoholates to yield the respective ethers
(A, Scheme 1),11,12 which, however, are not known to proceed
for compounds bearing a phosphorus substituent in the ortho
position. In contrast, substituted ferrocenes can easily be
modified with a variety of P functionalities, due to a great
variety of accessible phosphorus-containing electrophiles,3
except for ferrocenyl ethers. The present ether oxygen atoms
Received: February 25, 2016
© XXXX American Chemical Society
A
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deprotonated ferrocenol 1a−Li or its o-phosphonato-substi-
tuted derivative 1b−Li with well-known electrophiles, such as
benzyl bromide (a), propargyl derivatives (b, c), the conversion
to a thp ether (=tetrahydropyran) (d), and chlorosilanes (e, f)
(Table 1). The results are summarized in Table 1, indicating a
Scheme 1. Synthetic Methodologies Resulting in the
Formation of Ferrocenyl Aryl Ethers: (A) Recently Reported
Copper-Mediated Ullmann-Type Coupling12 and (B) SNAr
Reactions, with One of the Three Examples Known for
Ferrocenyl Derivatives (B1, [Si] = SitBuPh2)14,15
Table 1. Nucleophilic Substitution Reactions (SN2) of
c
Hydroxyl Ferrocenes 1a,b with Electrophiles
phosphonates into the 1,2-P,O-phosphanes, a reduction and
Stelzer-coupling process had to be carried out, which sets
certain requirements on the tolerance of functional groups.
Aromatic ethers are promising structural motifs, since they
are known to be stable under different reaction conditions
without a C,O bond cleavage, a potentially increased steric
demand, and a stabilizing effect on aromatic substrates.13
Recently, an increase in the enantioselectivity in atrop-selective
catalytic cross-coupling biaryl synthesis, due to attractive
intermolecular π−π interactions, has been reported.13 Liter-
ature-known ferrocenyl aryl ethers have predominantly been
obtained by applying a copper-mediated Ullmann reaction (A,
Scheme 1).12 One example of a nucleophilic C,C aromatic
substitution reaction (SNAr) has been reported for an
intramolecular cyclization of an enantiomerically pure (Sp)-
perfluorinated phenyl imine (B1, Scheme 1), which has been
observed accidentally.14 Furthermore, two examples of an SNAr
reaction with 4-chloroquinolines were reported.15
a
b
Based on 1a−H and 1b−H. A nucleophilic addition reaction occurs
c
instead of a substitution. The FcOLi compounds 1a−Li and 1b−Li
were generated by either lithiation of 1a−H using BuLi or by an 1,3-O
→ C anionic phospho-Fries rearrangement of diethylferrocenyl
phosphate (17) (Experimental Section). Legend: (i) thf or Et2O, 18
h, room temperature; (ii) (1) CH(OH)R′Ph, BuLi, ClPPh2, thf, (2)
2,6-dimethylcyclohexa-2,5-diene-1,4-dione, 1a−H, 18 h, room temper-
ature; (iii) HCl (∼3 M in thf), dichloromethane, 18 h, room
temperature. Ts = SO2-C6H4-p-CH3).
We herein report on the synthesis of singly and doubly ortho
substituted aromatic ferrocenyl ethers using SNAr reactions
(B2, Scheme 1). Furthermore, the reactivity of the hydroxyl
substituent toward several electrophiles is examined. The
presented synthesis protocol enables a high-yield synthesis
that can even be applied to singly and doubly ortho
functionalized compounds of the type Fc−O−Ar (Fc =
Fe(η5-C5H5)(η5-C5HnX4−n); n = 2−4; X = H, P(O)(OEt)2,
SO2CF3; Ar = 2,4-(NO2)2-C6H3, 4-NO2-C6H4) in a one-pot
approach after intramolecular rearrangements, such as the 1,3-
O → C anionic phospho- and thia-Fries rearrangement.
Electrochemical investigations estimate the nucleophilicity of
the Fc−OLi intermediates in dependency of the ortho
substituents. Previously published related ferrocenyl phos-
phates4,5 and phosphonates have also been taken into
consideration, and their redox potentials will be reported
herein.
low nucleophilicity of ferrocenolates toward SN2 reactions at
carbon atoms containing bromide (a), tosylate (b, c) and
phosphinates (d, e), due to a rapid oxidation of 1a−H by the
required quinone for d and e (Table 1).16
In contrast, the nucleophilic addition reaction of 3,4-dihydro-
2H-pyran (Table 1, f) and ferrocenol derivatives is known to
proceed with virtually quantitative yield10b,17 and can also
successfully be applied to the o-phosphonato ferrocenol 1b−H,
affording 2f in 99% yield, after an anionic phospho-Fries
rearrangement. Interestingly, 2f is not obtained as a racemic
mixture but as a mixture of both diastereomers in the ratio
0.68:0.32. The usage of chlorosilanes18 allows the synthesis of
the respective ferrocenyl silyl ethers rac-2g (56%) and rac-2h
(52%). However, silyl and thp ethers are known to be unstable
under long-term basic conditions at higher temperatures or in
Pd-catalyzed reactions.19
Phenols, as the benzene analogues of ferrocenols, can be
converted into aromatic ethers: e.g., by using iodonium20 or
diazonium compounds.21 Attempts to adopt these reaction
conditions for ferrocenol (1a−H) to give the appropriate
RESULTS AND DISCUSSION
For the conversion of the ferrocene-hydroxyl group with
electrophiles to ethers, we investigated the reaction of the
■
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ferrocenyl phenyl ether 4d by using diphenyliodonium triflate
and phenyldiazonium tetrafluoroborate failed, probably due to
the oxidation and decomposition of 1a−H.22
Scheme 2. Reaction of Ferrocenol (1a-H) with 1,3- (5) and
1,2-Difluorobenzenes (6) To Produce the Ferrocenyl Aryl
a
Ethers 7a−c and 8, Respectively
A further possibility for the introduction of aryl substituents
at oxygen-based nucleophiles is the usage of electron-deficient
aryl halides in SNAr reactions, which is well-known for phenyl
derivatives,23,24 whereas only three examples have been
reported for ferrocenyl-based compounds, i.e. reaction B1
(Scheme 1), and chloroquinones.14,15 Thus, we reacted FcOLi
(1a−Li) with Sangers reagent25 (3a), affording the respective
ferrocenyl ether 4a in 81% yield (Figure 1). The reaction
conditions were adopted from ref 23.
a
Legend: (i) (1) hexane, −30 °C, BuLi; (2) N,N-dimethylformamide,
5/6, 70 °C, 18 h.
In the case of 5, monofunctionalized 7b and a product
bearing an NMe2 moiety (7c), which results from the
nucleophilic attack of dmf (=N,N-dimethylformamide) at a
fluorine-bearing carbon atom,30 were formed. In contrast to 5,31
compound 6 is not known to undergo single substitution.31,32
Recently, we reported on the 1,3-O → C anionic phospho-
Fries rearrangement on ferrocenyl phosphates.4,5 The respec-
tive rearrangement products contain a hydroxy substituent that
should be suitable for SNAr reactions with aryl fluorides. This
prompted us to extend the substrate scope to o-phosphonato-
and sulfonyl-substituted hydroxyl ferrocenes that can be
obtained after the respective anionic phospho-4,5 and thia-
Fries10 rearrangements of 9 and 10 (Scheme 3). In a
consecutive one-pot synthesis, ferrocenyl phosphate 94,5 and
triflate (10)10 undergo the 1,3 O → C migration to give 1,2-
X,O (X = P, S) ferrocenolates 11−Li and 12−Li, respectively.
Their reaction with aryl fluorides 3a,b resulted in the formation
of ortho-substituted ferrocenyl aryl ethers rac-11a,b and rac-
12a, a rarely described structural motive in ferrocene
chemistry.33 In contrast to the phosphonato ferrocenes rac-
11a,b, the respective sulfonyl derivatives possess a lower
nucleophilicity of the hydroxyl oxygen, due to the highly
electron withdrawing character of the SO2CF3 moiety (vide
infra). Thus, no reaction with the less electrophilic aryl fluoride
3b to give ether rac-12b occurred. The ortho-substituted
ferrocenyl phosphate 11c and triflate 12c can undergo a further
anionic phospho-Fries rearrangement to result in the 1,3-
disubstituted ferrocenes rac-12−Li and rac-13−Li.4,5,10
Figure 1. Synthesis of the ferrocenyl aryl ethers 4a−f. (a) For 3f, the
η6-Cr(CO)3 complex was used. Legend: (i) BuLi, hexane, 3a−f, N,N-
dimethylformamide, 70 °C, 18 h.
The reaction of 4-nitrofluorobenzene (3b) with 1a−H
resulted in the formation of 4b in 74% yield (Experimental
Section). Less electron deficient derivatives such as 3c−e did
not undergo a SNAr reaction, which is in accordance with the
case for benzene-based compounds.23,24 An activation of 3d to
the respective tricarbonylchromium complex, known for
alkoxy26 and N nucleophiles,27 did not enhance the reactivity.
Nitrogen-containing aryl halides, e.g. pyridines, pyrimidines,
and pyrazines, are also not suitable for the reaction of
ferrocenol, in contrast to the phenyl-based derivatives.28 The
dependence between reactivity and the presence of multiple
electron-withdrawing substituents can be optically observed as a
rapid color change in the conversion of compound 3a to 4a,
whereas a decay of several minutes in the case of 3b indicates a
decreased reactivity for the single nitro-substituted derivative.
It should be noted that within the synthesis of 4a the excess
of Sanger’s reagent could not be removed, owing to an equal
chromatographic behavior. Thus, it was necessary to further
react the crude product of 4a with dicyclohexylamine and
K2CO3 in acetone at 40 °C to convert 3a into 2,4-dinitro-N,N-
dicyclohexylaniline, which could easily be separated by column
chromatography. This workup step could be avoided by adding
dicyclohexylamine directly to the reaction mixture.
Subsequent reaction of rac-13−Li with the most electrophilic
aryl fluoride 3a afforded the di-ortho-substituted ferrocenyl aryl
ether rac-13a in 49% yield. In comparison to 11−Li, 13−Li is
less nucleophilic, due to one additional electron-withdrawing
substituent, which obviously prevents the reaction with the less
electrophilic aryl fluoride 3b. This is comparable to SO2CF3-
bearing 12, which can only be converted using 3a, whereas for
doubly ortho substituted 14−Li, no reaction occurred. The
reactivity can be estimated by the determination of the redox
potential by cyclic voltammetry (CV) (vide infra).
The synthesis protocol for the ferrocenyl aryl ethers 4a,b
gave access to benzenes bearing two ferrocenyl ether groups by
the treatment of 1a−H with the 1,3- (5) or 1,2-
difluorobenzenes (6),29 resulting in the formation of the first
m- (7a) and o-disubstituted (8) bis(ferrocenyloxy) benzenes
(Scheme 2).
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Scheme 3. Synthesis of 1,2-Disubstituted (rac-11a,b,d, rac-12a) and 1,2,3-Trisubstituted (rac-13a) Ferrocenyl Aryl Ethers That
a
Can Be Obtained after an Anionic Phospho- (9, 11c) and Thia-Fries (10, 12c) Rearrangement
a
Legend: (i) 9/11c, LDA (=lithium diisopropylamide), tmeda (=tetramethylethylenediamine), hexane, 25 °C; (ii) 3a,b, dmf, 70 °C, 18 h; (iii)
ClP(O)(OCy)2; (iv) 10/12c, LDA, −80 °C, 1 h; (v) O(SO2CF3)2, 25 °C.
A carbo-Fries rearrangement, which has been reported for
phenyl-based derivatives, for example, alkyl amides,34 was also
investigated by treating ferrocenyl acetate with LDA at −80 °C.
However, instead of an ortho lithiation, a nucleophilic attack of
LDA at the carbonyl carbon atom occurred, resulting in the
formation of 1a−Li, and after subsequent reaction with 3a,
compound 4a is formed exclusively.
The Fries rearrangement to o-phosphonato ferrocenolates
can additionally be performed with the chiral-pool-based
di(1R)-α-fenchyl ferrocenyl phosphate 15,5 affording ethers
(Rp)-16a (de = 0.81) and (Rp)-16b (de = 0.74) (Scheme 4),
whereas the diastereomeric excess (de) was calculated on the
basis of the integrated 31P{1H} NMR spectra.5
between the two nitro substituents. The electron-donating
NMe2 group in 7c shifts the first signal to a higher field (6.26
ppm) in comparison to the OFc (7a, 6.68 ppm) or the rather
electron-withdrawing F substituent in 7b, which also splits both
signals into doublets (6.87 and 8.83 ppm) due to a JH,F coupling
of 11.9 (3J) and 7.6 Hz (4J). Characteristic resonance signals are
also present at 2.57 ppm for the terminal CH proton in 2b
and the methyl groups in 2c (1.90 ppm) and 7c (2.85 ppm).
Compounds rac-2g,h exhibit signals in the 29Si{1H} NMR at
−3.1 ppm for rac-2g and 17.8 ppm for rac-2h. A difference
between the 2,4-dinitro and the 4-nitro substituents on the
ferrocenyl backbone is negligible.
The respective resonances in the 31P{1H} NMR spectra are
found at 19.1 (rac-11a), 19.3 ppm (rac-11b), 20.5 ((Rp)-16a),
and 21.2/22.2 ppm ((Rp)-16b). Solely the phosphorus atom in
rac-13a, bearing two phosphonato substituents, is shifted to
higher field (17.4 ppm). The electron-donating influences of
the silyl (rac-2g, 24.9 ppm; rac-2h, 24.7 ppm) and phosphato
moieties (rac-11d, 21.2 ppm) also shield the phosphorus atom.
In the 13C{1H} NMR spectra, the decrease of the
withdrawing character of the nitro substituents shifts the C−
P or C−S carbon atom to higher field, as expected, from 63.4
(rac-11a) to 62.9 ppm (rac-11b), 69.4 (rac-12a) to 69.2 (rac-
12b) ppm, and 61.9 ((Rp)-16a) to 60.6 ((Rp)-16b) ppm. These
resonances in phosphonates rac-2g,h, rac-11a,b, rac-13a, and
Scheme 4. Synthesis of Diastereoenriched Planar Chiral
a
Ferrocenyl Aryl Ethers (Rp)-16a,b
1
(Rp)-16a,b occur as doublets with a JC,P coupling constant of
214−219 Hz, similar to the recently reported ferrocenyl
phosphonates.4,5 Interestingly, the influence on the C−O
binding carbon of the C5H4 and C5H3 rings is in contrast with
the electron-withdrawing character of the aryl substituent,
resulting in a downfield shift from 119.5 (4a) to 119.9 (4b)
ppm, 119.3 (rac-11a) to 120.1 (rac-11b) ppm, and 120.8 ((Rp)-
16a) to 121.6 ppm ((Rp)-16b).
a
Legend: (i) lithium tetramethylpiperidide, tmeda, hexane, 25 °C; (ii)
3a,b, dmf, 70 °C.
In the 1H NMR spectra of compounds 2b,c,e−h, 4a,b, 7a−c,
8, rac-11a,b, rac-12a, rac-13a, and (Rp)-16a,b, one singlet for
the C5H5 protons is found. For the C5H4 and C5H3
cyclopentadienyl protons either two pseutotriplets (2b,c,d−h,
4a,b, 7a−c, and 8), or three multiplets (11a,b, rac-12a, rac-13a,
and (Rp)-16a,b) are observed, as expected (Experimental
Section). The resonances of the phenylic aromatic protons
occur between 6.9 and 8.8 ppm. Compounds 7a−c exhibit two
resonances at 6.3−6.7 and 8.7−8.8 ppm for the protons located
In the 1,3-bisphosphonato species rac-13a, this signal is
observed at 118.6 ppm. Compound rac-13a is formed as a
mixture of two isomers regarding the rotation of the aromatic
1
C6H3(NO2)2 moiety, due to two sets of signals in the H and
13C{1H} NMR spectra formed in a ratio of approximately
0.8:0.2. The two sets exhibit similar JH,H values in the 1H NMR
spectrum, whereas the sum of the integrals of both signals is
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required for a comparison with the integrals of the ferrocenyl
and cyclohexyl protons and, thus, an impurity of further
aromatic compounds can be excluded.
The presence of electron-donating ferrocenyl35 and electron-
withdrawing NO2 substituents combined in one molecule
prompted us to investigate the solvatochromic behavior of
these species using UV/vis spectroscopy. Thus, we investigated
the π−π* absorption of compound 4a in five different solvents
from hexane (nonprotic, nonpolar) to ethanol (protic, polar)
with concentrations of 3 × 10−5 mol L−1 (Table SI8 in the
Supporting Information). The UV/vis spectra of 4a contain
one absorption between 250 and 350 nm, which can be
ascribed to the π−π* absorption band of the phenyl
substituent. However, a shift of 13 nm indicates that a
neglectable positive solvatochromic behavior is present,
probably due to the small +M/+I effect of the oxygen ether
atom.
The molecular structures of 4a,b, 6,29 7a−c, 8, and rac-12a in
the solid state have been determined by single-crystal X-ray
diffraction analysis at 110 K (Figures 2, 3, 4, and 5 and Figure
Figure 3. ORTEP diagrams (50% probability level) of the molecular
structures of 7a (top) and 8 (bottom) with the atom-numbering
scheme. Hydrogen atoms and solvent molecules (one molecule of
dichloromethane in 8) have been omitted for clarity. The intra-
molecular T-shaped π interaction between the centroids is represented
in pale blue: distance, 4.898(6) Å; intersection, 82.8(6)°.
those of 8 from boiling toluene solutions containing the
respective compounds. The compounds crystallize in triclinic
(P1, 4a, rac-12a) monoclinic (P2 /n, 4b, 7b; P2 , 7a; C2/c, 8)
̅
1
1
orthorhombic (P212121, 7c) and tetragonal (P43212, 6) space
groups with one (4b, 7a−c and rac-12a) two (4a), or a half of a
molecule (6) in the asymmetric unit. The ferrocenyl backbone
adopts an eclipsed conformation for 4a,b, 7a−c, and 8 (4a
0.1(2)° to 7 5.97(18)°) and a staggered rotation for 1,2-S,O-
substituted rac-12a (22.7(2)°). The phenyl ring mainly reveals
a perpendicular orientation toward the cyclopentadienyls for
7a,b, 8, and rac-12a (4b 82.00(11)° to 7b 88.74(10)°) or range
between 42.7(4) and 69.90(10)° for 4a and 7a−c (Table SI7).
In diferrocenyl-substituted compounds 7a and 8 the different
substitution patterns (1,3 in 7a; 1,2 in 8) affects the orientation
of the ferrocenyls with respect to each other. The increased
distance of the 1,3-disubstitution allows for a more flexible
rotation and, thus, a stabilization of the packing by an
intramolecular T-shaped π interaction between a C5H5 and a
C5H4 unit (Figure 3). In contrast, compound 8 reveals a near-
coplanar orientation of both ferrocenyls (deviation from
coplanarity 5.16(18)°) with their backbones directed away
from the phenylene core in perpendicular torsions (86.13(8),
85.65(8)°).
Figure 2. ORTEP diagrams (50% probability level) of the molecular
structures of 4a (top) and 4b (bottom) with the atom-numbering
scheme. All hydrogen atoms have been omitted for clarity.
SI7 in the Supporting Information). Crystal and structure
refinement data are displayed in the Experimental Section.
Selected bond distances, angles, and torsion angles, as well as
plane intersections, are given in Table SI7 in the Supporting
Information. Suitable single crystals of 6, 7b, and rac-12a were
obtained by evaporation of hexane solutions at ambient
temperature, those of 4a,b and 7a,c from boiling hexane, and
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possible, due to a small N1−O4···N1 angle of 94.49(14)°.
Equal N1−O3/4 bond distances of 1.222(3) and 1.227(3) Å
support this conclusion.
The NO2 substituents in 4a,b, 7b,c, and rac-12a, where steric
reasons are excluded, adopt plane intersection angles toward
the C6 phenyl plane between 0.04(4)° (4b) and 40.78(12)°
(7b), caused by packing effects (Table SI3 and Figure SI3 in
the Supporting Information). Interestingly, the [NO2]−[C6]
plane intersection of 37.0(5)° in 7c is rather small, although an
NMe2 group in an ortho position with rather coplanar C6−
N3−C18 torsions (24.9(11) and 22.5(18)°) is present. This
results in a significant twisting of the C3 and C4 atoms above
and C5 below the C6 ring (rms deviation 0.0381).36
The O−CFc and O−CPhenyl bond lengths at the ether oxygen
reveal a significantly enlarged O−CFc bond distance of
1.382(10)−1.416(14) Å in comparison to 1.325(15)−
1.373(4) Å for O−CPhenyl. This is in accordance with recently
reported ferrocenyl phosphates.5 The longer O−CFc bond (ca.
0.05 Å) might be due to the increased electron density at the
ferrocenyl groups and thus a weakening of the O−CFc bond. In
comparison to the four structures reported in the literature
containing a ferrocenyl aryl ether motif, electron-rich tert-butyl-
substituted phenyl ethers also exhibit enlarged O−CFc bonds
(e.g., O−Fc 1.377(3) Å vs O−Ar 1.396(3) Å and O−Fc
1.370(2) Å vs O−Ar 1.401(2) Å), which excludes an electronic
effect of the withdrawing aryl substituent.37 O−alkyl, e.g. O−
Me, ethers exhibit an opposite behavior owing to an sp3-
hybridized carbon atom. The angles of the ether oxygen atoms
range from 116.14(18)° (8) to 122.2(7)° (7a), whereas values
above 120° are caused by an intramolecular π interaction in 7a
or the distortion of the phenyl ring in 7c (Table SI7 in the
Supporting Information).
The reported ferrocenyl aryl ethers 4a, 7b,c, 8, and rac-12a
are also involved in intermolecular T-shaped and parallel
displaced π−π interactions in their crystal packing (Tables
SI1−SI6 and Figures SI1−SI6 in the Supporting Information).
Between the electropositive nitrogen and electronegative
oxygen atoms of the NO2 groups, short distances are observed
in the packing of 7a−c, the last compound also exhibits short
O···C contacts (Figures SI2−SI4). The present fluorine
substituents also interact over short distances within the sum
of the van der Waals radii: e.g., in F···F (rac-12a, Figure SI6)
and F···O (7b, Figure SI3) interactions.
Figure 4. ORTEP diagrams (50% probability level) of the molecular
structures of 7b (top) and 7c (bottom) with the atom-numbering
scheme. All hydrogen atoms and the second independent molecule of
the asymmetric unit of 7b have been omitted for clarity.
Electrochemistry. The electrochemical behavior of 4a,b,
7a−c, 8, 9, 10, rac-11a−d, rac-12a, rac-13a, and 17
(diethylferrocenyl phosphate) was investigated by cyclic
voltammetry and square wave voltammetry. An anhydrous
dichloromethane solution containing 0.1 mol L−1 of [NBu4]-
[B(C6F5)4] was used as supporting electrolyte. The cyclic
voltammetry measurements were performed at 25 °C. All
potentials are referenced to the FcH/FcH+ redox couple.38 The
data of the cyclic voltammetry experiments (scan rate 100 mV
s−1) are summarized in Table 2. Compounds 1010 and 1739
were measured with the [NBu4][B(C6F5)4] electrolyte for
comparison.
In the cyclic voltammograms of 9, 10, 11c,d, and 17 one
reversible redox event for the ferrocenyl unit was observed
(Figure SI8 in the Supporting Information). The ferrocenyl
redox processes of 9, 11d, and 17 can be found between 20 and
50 mV, indicating similar electron densities at the ferrocenyl
moieties in all three compounds. The second phosphonate
group in 11c and the triflate group in 10 led to decreased
electron densities at the ferrocenyls, and therefore the values for
Figure 5. ORTEP diagram (50% probability level) of the molecular
structure of rac-12a with the atom-numbering scheme. All hydrogen
atoms have been omitted for clarity.
The difference between the 1,2-/1,3-substitution pattern also
affects the rotation of the nitro groups. Thus, they are
approaching a coplanar orientation in 7a (22.9(13)°), whereas
the steric demand in 1,2-positioned 8 results in an almost
orthogonal orientation (77.2(3)°). An electrostatic interaction
between N2 and O4 is present, due to a separation far below
the sum of the van der Waals radii (∑ = 3.07 Å) of 2.6032(1)
Å. However, an interaction of O4 to the partially positively
charged N1 atom of an adjacent molecule does not seem to be
F
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Table 2. Cyclic Voltammetry Data (mV) of 4a,b, 7a−c, 8−
a
10, rac-11a−d, rac-12a, rac-13a, and 17
b
b
b
b
E°1′(NO2)
E°2′(NO2)
E°3′(Fc)
c
E°4′(Fc)
c
c
c
compd
(ΔEp)
(ΔEp)
(ΔEp)
(ΔEp)
4a
−1800 (86)
−1700 (92)
−1595 (89)
−1795 (89)
−1710 (96)
−1485 (70)
190 (64)
105 (70)
155 (79)
230 (85)
110 (80)
130 (75)
20 (83)
4b
7a
275 (85)
340 (79)
7b
−1465 (85)
−1330 (95)
7c
d
8
−1560 (101)
9
10
335 (69)
345 (72)
275 (83)
170 (63)
40 (74)
rac-11a
rac-11b
rac-11c
rac-11d
rac-12a
rac-13a
17
−1830 (84)
−1750 (211)
−1490 (76)
−1425 (73)
d
Figure 6. Cyclic voltammogram (solid line, scan rate 100 mV s−1) and
square wave voltammogram (dashed line) of rac-11a in dichloro-
methane solutions (1.0 mmol L−1) at 25 °C, with 0.1 mol L−1
[NBu4][B(C6F5)4] supporting electrolyte and a glassy-carbon working
electrode.
−1755 (80)
725 (73)
520 (70)
45 (76)
d
−1535 (125)
a
Potentials vs FcH/FcH+, scan rate 100 mV s−1 at a glassy-carbon
electrode with an analyte concentration of 1.0 mmol L−1 using 0.1 mol
L−1 [NBu4][B(C6F5)4] as supporting electrolyte in anhydrous
b
c
dichloromethane at 25 °C. E°′ = formal potential. ΔEp = difference
between the anodic and cathodic peak potential. The redox processes
d
are not reversible.
E°1′ are shifted to higher potentials (335 mV (10), 170 mV
(11c)).
The cyclic voltammograms of 4a,b show two (4b) or three
(4a) redox processes in a potential range of −1800 mV to +190
mV (Figure SI9 in the Supporting Information). The cathodic
events between −1800 and −1485 mV could be assigned to
redox processes of the nitro substituents (Figure SI9).40 The
second nitro group in 4a leads to a somewhat increased
potential for the ferrocenyl redox events (190 mV), in
comparison to 4b (105 mV).
For rac-11a,b, rac-12a, and rac-13a one reversible redox
process for the ferrocenyl groups was observed during the
electrochemical measurements (Figures 7 and 8). The redox
events for Fc/Fc+ in rac-11a,b are found at 345 mV (rac-11a)
and 275 mV (rac-11b), respectively. An increasing number of
phosphonate groups as well as a triflate group led to decreased
electron densities at the ferrocenyl motifs, resulting in increased
redox potentials (725 mV (rac-12a), 520 mV (rac-13a); Figure
SI10 in the Supporting Information). In rac-11a and rac-12a
two reversible redox events for the nitro groups between −1830
and −1425 mV are present (Figure 6 and Figure SI10). In
contrast, during electrochemical measurements of rac-11b and
rac-13a in the same potential limits, irreversible redox events
occurred (Figure SI10), indicating a decomposition of the
compounds during the electrochemical studies. A comparison
of the redox potentials of the ferrocenyl units of rac-11a,b with
those of 4a,b shows that the additional phosphonate group in
rac-11a,b leads to a decreased electron density at the ferrocenyl
and, therefore, to a shift of the redox events to higher
potentials.
Figure 7. Cyclic voltammograms (solid lines, scan rate 100 mV·s−1)
and square wave voltammograms (dashed lines) of 7a−c and 8 in
dichloromethane solutions (1.0 mmol L−1) at 25 °C, with 0.1 mol L−1
[NBu4][B(C6F5)4] supporting electrolyte and a glassy-carbon working
electrode.
(ΔE°′ = 120 mV). Furthermore, the CVs of 7a−c and 8 show
redox processes between −1795 and −1330 mV for the nitro
groups (Figure SI11 in the Supporting Information). With the
increased electron-withdrawing character of the substituent
bonded to the C6H2 rings in 7a−c, the potentials of the
ferrocenyl redox processes are shifted toward higher potentials.
The differences within the nucleophilicity can be confirmed
by comparing the potential of the first ferrocene-related redox
processes of the 2,4-dinitrophenyl ethers 4a and 11a−13a with
their electronic properties solely determined by their ortho
substituents. The potentials increase as 4a (190 mV, o-R = H)
< 11a (345 mV, o-R = P(O)(OCy)2) < 13a (520 mV, o-R =
(P(O)(OCy)2)2) < 12a (725 mV, o-R = SO2CF3), confirming
the sulfonyl substituent to be even more electronically
withdrawing than two phosphonato substituents. This leads
to the conclusion that the respective lithium ferrocenolato
compounds follow this trend within SNAr reactions.
In the cyclic voltammograms of 7a−c and 8 a reversible
event for each ferrocenyl unit was observed (7a, 155 and 275
mV; 7b, 230 mV; 7c, 110 mV; 8, 130 and 340 mV) (Figure 7).
The potential of the first redox event in the series increases (7c
< 7a < 7c), indicating an increased electron density at the
ferrocenyl moiety in 7c. The two ferrocenyl-related events in 8
(ΔE°′ = 210 mV) exhibit a larger splitting in comparison to 7a
The redox separation in 7a and 8 could be caused by either
electrostatic factors or an electronic interaction between the
two redox sites. Therefore, UV/vis/NIR measurements with 8
were carried out, for example. The UV/vis/NIR studies of
dichloromethane solutions containing 8 (2.0 mmol L−1) and
G
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[NBu4][B(C6F5)4] (0.1 mol L−1) as supporting electrolyte were
performed in an OTTLE (optically transparent thin-layer
electrochemical) cell.41 The UV/vis/NIR spectra of different
redox states of 8 are depicted in Figure 8. During the stepwise
phospho- and thia-Fries rearrangements. Also, the first 1,3-di-o-
phosphonato functionalized ferrocenyl aryl ether, rac-13a,
could be synthesized. An electrochemical study of the redox
potentials of the obtained compounds allows conclusions on
the reactivity of the varying electronic properties and the
electrophilicity of different aryl fluorides, decreasing from the
dinitro (3a) to the mononitro (3b) fluorobenzene. The
nucleophilicity and, thus, the reactivity toward SNAr reactions
of the functionalized oxyferrocenes was estimated by comparing
the potential of the first ferrocene-related redox processes,
revealing the trend o-H (190 mV) < P(O)(OCy)2 (345 mV) <
(P(O)(OCy)2)2 (520 mV) < SO2CF3 (725 mV). The usage of
aryl 1,2-/1,3-difluorides resulted in the first examples of doubly
FcO substituted benzenes. Electrochemical investigations reveal
a splitting of the two redox processes that decreases from 155
mV (1,2-substitution) to 130 mV (1,3-substitution) on the
basis of electrostatic interactions, as confirmed by in situ UV/
vis/NIR measurements for the 1,2-substituted derivative, due to
the absence of an IVCT absorption in the mono-oxidized
species.
Figure 8. UV/vis/NIR spectra of 8 at 25 °C in dichloromethane (2.0
mmol L−1) at rising potentials (−200 to 1200 mV vs Ag/AgCl);
[NBu4][B(C6F5)4] supporting electrolyte.
EXPERIMENTAL SECTION
■
General Considerations. All reactions were carried out under an
atmosphere of nitrogen using standard Schlenk techniques. For
column chromatography either silica with a particle size of 40−60 μm
(230−400 mesh (ASTM)) or alumina with a particle size of 90 μm
was used. The assignment and labeling of the H and C atoms in the
NMR of the (bi)cyclic aliphatic substituents follows the IUPAC
recommendations.43
increase of the potentials (step heights: 100, 50, 25 mV) the
compound was oxidized from the neutral 8 to the mixed-valent
[8]+ and finally to the fully oxidized species [8]2+. In the case of
an electronic interaction between the Fc/Fc+ termini an
intervalence charge transfer (IVCT) band should develop in
the NIR region during the oxidation to the mixed-valent species
and disappear during the oxidation to the fully oxidized species.
However, during the oxidation of 8 no such band developed
and, thus, no significant electron transfer between the Fc/Fc+
termini takes place, prohibited by the two oxygen atoms that
prevent a conjugation. Therefore, the redox separations in 8
result solely from electrostatic interactions, implying that
compound 7a should exhibit a similar behavior. In contrast,
for known compounds with ferrocenyl groups directly bonded
to the benzene ring, IVCT absorptions of weak strength were
found with the maximum for 1,4-diferrocenylbenzene.42 To
prove the reversibility after complete oxidation, compound 8
was reduced at −400 mV and the obtained UV/vis/NIR
spectrum was identical with the spectrum of the starting
material.
Reagents. Tetrahydrofuran and hexane were purified by distillation
from sodium/benzophenone ketyl; diethyl ether was purified by
distillation from sodium; dichloromethane, N,N-dimethylformamide
and N,N-diisopropyl amine were purified by distillation from calcium
hydride. Butyllithium (2.5 M solution in hexane; caution! BuLi is
highly inflammable in the presence of moisture), ferrocene, lithium
tetramethylpiperidide (Litmp), 2,4-dinitrofluorobenzene, 4-nitrofluor-
obenzene (3b), fluorobenzene (3d), 1,3-difluorobenzene (3c), 1,5-
difluoro-2,4-dinitrobenzene (5), and 3,4-dihydro-2H-pyran were
purchased from commercial suppliers and were used without further
purification. POCl3 and tmeda were distilled prior to use. Ferrocenol
(1a−H),4,5,9−12 dicyclohexylchlorophosphate,4
dicyclohexyl 2-
44
b,
(O,O-dicyclohexylphosphonato)ferrocenyl phosphate (9),4 O,O-
b
dicyclohexyl-(2-methoxyferrocenyl) phosphonate (11d),4 diethylfer-
b
rocenyl phosphate (17),5 di(1R)-α-fenchyl ferrocenyl phosphate
(15),4 ferrocenyl triflate (10),10 diphenyliodonium triflate,20 1-(tert-
b
butyl)-4-phenoxybenzene,20,22 1,2-difluoro-4,5-dinitrobenzene (6),29
2,6-dimethylcyclohexa-2,5-diene-1,4-dione,16 propargyl tosylate,45a
but-2-yn-1-yl tosylate,45b [NBu4][B(C6F5)4],46 and (fluorobenzene)
chromium tricarbonyl (3f)47 were synthesized according to literature
procedures reported elsewhere.
CONCLUSION
■
A wide range of ferrocenyl aryl ethers of type Fc−O−Ar (Fc =
Fe(η5-C5H5)(η5-C5HnX4−n); n = 2−4; X = H, P(O)(OEt)2,
SO2CF3; Ar = 2,4-(NO2)2-C6H3, 4-NO2-C6H4) have success-
fully been prepared by using the nucleophilic aromatic
substitution reaction (SNAr) between Fc−OLi (1a−Li)) and
electron-deficient 1-fluoro-2,4-dinitrobenzene (3a) and 4-nitro-
benzene (3b), respectively, enabling a new pathway to this
rarely described family of compounds. Initial studies of 1a−Li
and o-phosphonato -substituted hydroxyferrocenes have also
been performed, indicating a low nucleophilicity of the oxygen
atom in nucleophilic substitution reactions: e.g., benzyl
bromide and propargyl tosylates. However, oxophilic chlor-
osilanes could be converted in high yield. The SNAr reaction
protocol also tolerates o-phosphonato and sulfonyl substituents,
resulting in 1,2-X,O (X = S, P) ethers that can be obtained in a
one-pot synthesis procedure including 1,3-O → C anionic
A HCl solution in tetrahydrofuran was obtained by adding 50 mL of
H2SO4 (ω = 96%) dropwise to NaCl (200 g). The gas formed was
directed into 100 mL of anhydrous tetrahydrofuran for 30 min.
1
Instruments. NMR spectra (500.3 MHz for H, 125.8 MHz for
13C, 99.4 MHz for 29Si, and 202.5 MHz for 31P) are reported with
chemical shifts in δ (ppm) units downfield from tetramethylsilane with
the solvent as the reference signal (chloroform-d1: 1H at 7.26 ppm and
13C{1H} at 77.00 ppm) or with external standards (31P{1H} relative to
85% H3PO4 at 0.0 ppm and to P(OMe)3 at 139.0 ppm, 29Si{1H}
relative to SiMe4 at 0.0 ppm). The melting points were determined
using a Gallenkamp MFB 595 010 M melting point apparatus.
Elemental analyses were performed with a Thermo FlashAE 1112
instrument. High-resolution mass spectra were recorded with a Bruker
Daltonik micrOTOF-QII spectrometer.
Electrochemistry. Electrochemical measurements of 4a,b, 7−10,
rac-11a−d, rac-12a, rac-13a, and 17 (1.0 mmol L−1) using 0.1 mol L−1
[NBu4][B(C6F5)4] as the supporting electrolyte in dichloromethane
H
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were performed in a dried, argon-purged cell at 25 °C with a
Radiometer Voltalab PGZ 100 electrochemical workstation interfaced
with a personal computer. For the measurements a three-electrode cell
containing a Pt auxiliary electrode, a glassy-carbon working electrode
(surface area 0.031 cm2), and an Ag/Ag+ (0.01 mmol L−1 [AgNO3])
reference electrode fixed on a Luggin capillary was used. The working
electrode was pretreated by polishing on a Buehler microcloth first
with 1 μm and then 1/4 μm diamond paste. The reference electrode
was constructed from a silver wire inserted into a 0.01 mmol L−1
solution of [AgNO3] and 0.1 mol L−1 of an [NBu4][B(C6F5)4]
acetonitrile solution in a Luggin capillary with a Vycor tip. This Luggin
capillary was inserted in a second Luggin capillary containing a 0.1 mol
L−1 [NBu4][B(C6F5)4] dichloromethane solution and a Vycor tip.
Experiments under the same conditions showed that all reduction and
oxidation potentials were reproducible within 5 mV. Experimental
potentials were referenced against an Ag/Ag+ reference electrode, but
the presented results are referenced against ferrocene as an internal
standard as required by IUPAC.38 To achieve this, each experiment
was repeated in the presence of 1 mmol L−1 of decamethylferrocene
(Fc*). Data were processed on a Microsoft Excel worksheet to set the
formal reduction potentials of the FcH/FcH+ couple to 0.0 V. Under
our conditions the Fc*/Fc*+ couple was at −619 mV vs FcH/FcH+,
ΔEp = 60 mV, while the FcH/FcH+ couple itself was at 220 mV vs Ag/
Ag+, ΔEp = 61 mV.48
Spectroelectrochemistry. Spectroelectrochemical UV/vis/NIR
measurements of 2.0 mmol L−1 solutions of 8 in anhydrous
dichloromethane containing 0.1 mol L−1 of [NBu4][B(C6F5)4] as
the supporting electrolyte were performed in an OTTLE (optically
transparent thin-layer electrochemical)41 cell with a Varian Cary 5000
spectrophotometer at 25 °C.
Single-Crystal X-ray Diffraction Analysis. Data for 4a,b, 6, 7a−
c, 8, and rac-12a were collected at 110 K with graphite-
monochromated Mo Kα radiation (λ = 0.71073 Å). The molecular
structures were solved by direct methods using SHELXS-1349 and
refined by full-matrix least-squares procedures on F2 using SHELXL-
13.50,51 All non-hydrogen atoms were refined anisotropically, and a
riding model was employed in the treatment of the hydrogen atom
positions. Graphics of the molecular structures have been created by
using ORTEP.52 Crystallographic data of 4a,b, 6, 7a−c, 8 and rac-12a
are available from the Cambridge Crystallographic Database as file
numbers CCDC 1446860 (4a), 1446861 (4b), 1446862 (6), 1446863
(7a), 1446864 (7b), 1446865 (7c), 1446866 (8), and 1446867 (rac-
12a).
electrophile or the general procedure for nucleophilic aromatic
substitution reactions was applied (see below).
Procedure C5 (using Litmp as the Base). In a Schlenk tube lithium
tetramethylpiperidide (litmp) (2 equiv) and tetramethylethylenedi-
amine (2 equiv) were suspended in 3 mL of hexane and cooled to −30
°C. The mixture was stirred for 10 min at −30 °C, and then 15 (1
equiv) was added in a single portion. The obtained reaction mixture
was warmed to ambient temperature, and stirring was continued for 18
h. Afterward, the general procedure for nucleophilic aromatic
substitution reactions was applied (see below).
(Prop-2-yn-1-yloxy)ferrocene (2b). Ferrocenol (1a−H; 87 mg,
0.43 mmol) was diluted in 20 mL of diethyl ether, and BuLi (0.18 mL,
0.45 mmol) was added dropwise at −30 °C. After the mixture was
stirred for 10 min at this temperature, propargyl tosylate (136 mg, 0.65
mmol) was added in a single portion. The reaction mixture was
warmed to ambient temperature, and stirring was continued overnight.
Purification was realized by column chromatography (silica, 2 × 8 cm)
using a 1/1 hexane/dichloromethane mixture (v/v) as the eluent. All
volatiles were removed in vacuo, whereby compound 2b was obtained
as an orange oil.
Yield: 11 mg (0.46 mmol, 11% based on 1a−H). 1H NMR (CDCl3,
4
3,4
δ): 2.57 (t, JH,H = 2.4 Hz, 1 H, CH), 3.85 (pt,
J
= 1.9 Hz, 2 H,
H,H
C5H4), 4.19 (pt, 3,4JH,H = 1.9 Hz, 2 H, C5H4), 4.22 (s, 5 H, C5H5), 4.48
(d, JH,H = 2.4 Hz, 2 H, CH2). 13C{1H} NMR (CDCl3, δ): 56.1
4
(C5H4), 58.4 (CH2), 62.1 (C5H4), 68.7 (C5H5), 75.4 (CC), 79.1
(CC), 125.9 (CC H −O). HRMS (ESI-TOF, m/z): decomposed
5
4
before measurement.
(But-2-yn-1-yloxy)ferrocene (2c). According to the synthesis of
compound 2b, ferrocenol (1a−H; 182 mg, 0.90 mmol), BuLi (0.36
mL, 0.90 mmol), and methylpropargyl tosylate (243 mg, 1.08 mmol)
were reacted. Purification was realized by column chromatography first
on silica (2 × 6 cm, dichloromethane) followed by alumina (4 × 6 cm)
using dichloromethane as the eluent. All volatiles were removed in
vacuo, whereby compound 2c was obtained as an orange oil.
Yield: 48 mg (0.46 mmol, 21% based on 1a−H). 1H NMR (CDCl3,
5
5
δ): 1.90 (dd, JH,H = 2.3 Hz, JH,H = 2.3 Hz, 3 H, CH3), 3.84 (pt,
3+4
3+4
J
= 2.0 Hz, 2 H, C5H4), 4.16 (pt,
J
= 2.0 Hz, 2 H, C5H4),
H,H
H,H
4.21 (s, 5 H, C5H5), 4.44 (m, 2 H, CH2). 13C{1H} NMR (CDCl3, δ):
3.7 (CH3), 55.9 (C5H4), 58.9 (CH2), 62.0 (C5H4), 68.6 (C5H5), 74.4
(CC), 83.6 (CC), 125.8 (CC H −O). HRMS (ESI-TOF, m/z):
5
4
calcd for C14H14FeO 254.0389, found 254.0404 [M]+.
O,O-Diethyl (2-(Tetrahydro-2H-pyran-2-yloxy)ferrocenyl)-
phosphonate (2f). Diethylferrocenyl phosphate5 (17; 1.08 g, 3.2
mmol), diisopropylamine (0.89 mL, 6.4 mmol), and BuLi (2.56 mL,
6.4 mmol) were reacted according to the general procedure A for
anionic Fries rearrangements. Afterward, oxygen-free 10 N H2SO4 (1.3
mL, 12.8 mmol) and oxygen-free water (10 mL) were added in a
single portion. The mixture was extracted using oxygen-free diethyl
ether (3 × 50 mL), the combined organic layers were filtered through
oxygen-free MgSO4 and collected in a Schlenk tube, and all volatiles
were removed in vacuo. The tetrahydropyranyl substituent was
introduced related to ref 17 by diluting the precipitate with
dichloromethane, and HCl in tetrahydrofuran (0.3 mL, ∼3 M) and
3,4-dihydro-2H-pyran (0.87 mL, 9.6 mmol) were added. The reaction
mixture was stirred overnight, poured into 100 mL of NaOH (w =
5%), and extracted with diethyl ether (3 × 50 mL). The combined
organic layers were dried over Na2CO3, and all volatiles were removed
in vacuo. The crude product was purified by column chromatography
(alumina, 4 × 10 cm) using dichloromethane as the eluent, yielding
the title compound 2f as an orange oil with a ratio of both
diastereomers of 0.32:0.68.
General Procedure for the SNAr Reactions. To compounds
1a,b−Li, 9−Li, 10−Li, 11c−Li, and 12c−Li were added 3 mL of
oxygen-free N,N-dimethylformamide and 0.5 equiv of 5 and 6 or 3
equiv of 3a−f of the respective aryl fluorides. The solvent was reduced
to about 2 mL in vacuo. After the mixture was heated to 70 °C for 18
h, all volatiles were removed in vacuo. The residue was dissolved in
diethyl ether (50 mL) and washed with brine (400 mL) and the latter
species was extracted again with diethyl ether (3 × 50 mL).
Purification was realized by column chromatography (silica; for
column size see below) using different solvent mixtures (see below).
Anionic Fries Rearrangements: General Procedure. Proce-
dure A4 (using LDA as the Base). In a Schlenk tube tetrahydrofuran
(3 mL) and diisopropylamine (2 equiv) were cooled to −30 °C.
Afterward, BuLi (2 equiv) was added dropwise. The mixture was
stirred for 10 min at −30 °C and then 1b−H (1 equiv) or 10 (1 equiv)
was added in a single portion. The obtained reaction mixture was
stirred for 4 h between −30 and −15 °C. Afterward, either an
electrophile or the general procedure for the nucleophilic aromatic
substitution reactions was applied (see below).
1
Yield: 1.350 g (3.19 mmol, 99% based on 17). H NMR (CDCl3,
Procedure B5 (using LDA as the Base). In a Schlenk tube hexane (3
mL) and diisopropylamine (2 equiv) were cooled to −30 °C.
Afterward, BuLi (2 equiv) was added dropwise, followed by addition of
tetramethylethylenediamine (2 equiv). The mixture was stirred for 10
min at −30 °C, and then 9 (1 equiv) or 11c (1 equiv) was added in a
single portion. The obtained reaction mixture was warmed to ambient
temperature, and stirring was continued for 18 h. Afterward, either an
δ): 1.24−1.41 (m, 6 H, CH3), 1.54−1.69 (m, 3 H, CH2), 1.74−1.92
(m, 3 H, CH2), 3.58−3.61 (m, 0.68 H, CH2), 3.69−3.71 (m, 0.32 H,
CH2), 3.76−3.81 (m, 0.68 H, CH2), 4.05−4.39 (m, 12 H, CH2, C5H5,
C5H3), 4.48−4.51 (m, 0.32 H, C5H3), 4.93 (s, 0.32 H, CH), 5.36 (s,
0.68 H, CH). 13C{1H} NMR (CDCl3, δ): 16.4−16.6 (m, CH3), 18.4
(0.68 C, CH2), 18.6 (0.32 C, CH2), 25.2 (0.68 C, CH2), 25.3 (0.32 C,
1
CH2), 30.2 (0.68 C, CH2), 30.4 (0.32 C, CH2), 58.3 (d, JC,P = 213.9
I
DOI: 10.1021/acs.organomet.6b00157
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Hz, C−P), 59.4 (d, JC,P = 11.2 Hz, 0.68 C, C5H3), 60.3 (d, JC,P = 11.5
Hz, 0.32 C, C5H3), 61.5−62.1 (m, CH2), 64.5 (d, JC,P = 14.1 Hz, 0.32
C, C5H3), 14.2 (d, JC,P = 14.2 Hz, 0.68 C, C5H3), 66.8 (d, JC,P = 13.4
Hz, 0.68 C, C5H3), 66.9 (d, JC,P = 13.7 Hz, 0.32 C, C5H3), 70.1 (s, 3.4
C, C5H5), 70.6 (s, 1.6 C, C5H5), 99.6 (s, 0.68 C, CH), 99.9 (s, 0.32 C,
CH2, C5H3). 13C{1H} NMR (CDCl3, δ): 12.5 (CH), 16.3 (CH3), 16.4
(CH3), 16.46 (CH3), 16.51 (CH3), 17.82 (CH(CH3)2), 17.85
1
2
(CH(CH3)2), 57.2 (d, JC,P = 215.5 Hz, C−P), 61.29 (d, JC,P = 5.8
2
Hz, CH2), 61.34 (d, JC,P = 6.6 Hz, CH2), 61.9 (d, JC,P = 11.6 Hz,
C5H3), 63.5 (d, JC,P = 14.5 Hz, C5H3), 66.7 (d, JC,P = 14.3 Hz, C5H3),
2
70.53 (C5H5), 123.2 (d, JC,P = 9.3 Hz, CC H −O). 29Si{1H} NMR
2
CH), 124.9 (d, JC,P = 9.7 Hz, CC H −O). 31P{1H} NMR (CDCl3, δ):
5
3
5
3
(CDCl3, δ): 17.8. 31P{1H} NMR (CDCl3, δ): 24.7. HRMS (ESI-TOF,
m/z): calcd for C23H39FeO4PSi + H 495.1778, found 495.1717 [M +
H]+.
23.7 (0.68 P), 24.1 (0.32 P). HRMS (ESI-TOF, m/z): calcd for
C19H27FeO5P + Na 445.0838, found 455.0910 [M + Na]+.
((Diphenylmethyl)oxy)ferrocene (2e). 1,1-Diphenylmethanol
(275 mg, 1.5 mmol) was dissolved in tetrahydrofuran and cooled to
−30 °C, and BuLi (0.6 mL, 1.5 mmol) was added dropwise. After 15
min of stirring at this temperature, ClPPh2 (0.27 mL, 1.5 mmol) was
added dropwise and stirring was continued for an additional 30 min at
ambient temperature. Afterward, all volatiles were removed under
reduced pressure and 2,6-dimethylquinone (136 mg, 1.0 mmol) and
FcOH (1a−H) (200 mg, 1.0 mmol) were added in a single portion.
Oxygen-free dichloromethane (10 mL) was added, and the reaction
mixture was stirred for 18 h at ambient temperature. Purification was
performed by column chromatography (silica, 4 × 6 cm) using hexane
as the eluent. All volatiles were removed in vacuo, and compound 2e
was obtained as an orange solid.
Yield: 83 mg (0.23 mmol, 23% based on 1a−H). The spectroscopic
data are in agreement with those reported in the literature.12
2-(tBuPh2)silyloxyferrocenyl O,O-Diethyl Phosphonate (rac-
2g). Diethylferrocenyl phosphate5 (17; 1.102 g, 3.26 mmol),
diisopropylamine (0.92 mL, 6.52 mmol), BuLi (2.6 mL, 6.52
mmol), and tmeda (0.95 mL, 6.52 mmol) were reacted according to
the general procedure A for anionic Fries rearrangements. Afterward,
ClSitBuPh2 (2.5 mL, 9.77 mmol) was added in a single portion at −30
°C. The cooling bath was removed, and stirring was continued at
ambient temperature for 18 h. Purification was performed by column
chromatography (silica, 2 × 15 cm) using a 7/3 dichloromethane/
ethyl acetate mixture (v/v) (Rf = 0.31) as the eluent. All volatiles were
removed in vacuo, and compound rac-2g was obtained as an orange
oil.
1-Ferrocenyloxy-2,4-dinitrobenzene (4a). To ferrocenol (1a−
H; 218 mg, 1 mmol) in toluene (10 mL) was added BuLi (0.43 mL)
dropwise. Afterward, the general procedure for SNAr reactions was
applied using 1-fluoro-2,4-dinitrobenzene (3a; 101 mg, 0.50 mmol).
Dicyclohexylamine (97 mg, 0.54 mmol) was added in a single portion
to the solution, and stirring at 70 °C was continued for 3 h. Afterward,
the reaction mixture was cooled to ambient temperature and extracted
with diethyl ether (3 × 50 mL) and the solvent was removed under
reduced pressure. Purification was performed by column chromatog-
raphy (silica, 4 × 8 cm) using a 1/1 hexane/dichloromethane mixture
(v/v) as the eluent. All volatiles were removed in vacuo, and
compound 4a was obtained as an orange solid. Suitable single crystals
were obtained by recrystallization from boiling hexane.
Yield: 323 mg (0.88 mmol, 81% based on 1a−H). Anal. Calcd for
C16H12FeN2O5·1/6C6H14 (368.12·1/6(86.18) g/mol): C, 53.38; H,
3.78; N, 7.32. Found: C, 53.40; H, 3.63; N, 7.36. Mp: 125−128 °C. 1H
NMR (CDCl3, δ): 4.10 (pt, 3+4JH,H = 2.0 Hz, 2 H, C5H4), 4.36 (s, 5 H,
C5H5), 4.37 (pt, 3+4JH,H = 2.0 Hz, 2 H, C5H4), 7.11 (d, 3JH,H = 9.3 Hz,
1 H, H6), 8.28 (dd, 3JH,H = 9.3 Hz, 4JH,H = 2.8 Hz, 1 H, H5), 8.79 (d,
4JH,H = 28 Hz, 1 H, H3). 13C{1H} NMR (CDCl3, δ): 61.1 (C5H4),
64.3 (C5H4), 70.1 (C5H5), 116.9 (C6−C6H3), 119.5 (CC H −O), 121.7
5
4
(C3−C6H3), 128.7 (C5−C6H3), 138.6 (C2−C6H3), 140.9 (C4−
C6H3), 157.7 (C1−C6H3). HRMS (ESI-TOF, m/z): calcd for
C16H12FeN2O5 368.0090, found 368.0090 [M]+.
Crystal data for 4a: C16H12FeN2O5, Mr = 368.13 g mol−1, triclinic,
P1, λ = 0.71073 Å, a = 7.6575(5) Å, b = 12.3403(8) Å, c =
̅
Yield: 1.06 g (1.84 mmol, 56% based on 17). 1H NMR (CDCl3, δ):
1.10 (s, 9 H, C(CH3)3), 1.30 (t, 3JH,H = 7.1 Hz, 3 H, CH2−CH3), 1.44
(t, 3JH,H = 7.0 Hz, 3 H, CH2−CH3), 3.63 (ddd, JH,H = 2.8, 2.8 Hz, JH,P
= 1.5 Hz, 1 H, C5H3), 3.76 (dd, JH,H = 2.8, 2.8 Hz, 1 H, C5H3), 4.08−
4.17 (m, 7 H, CH2, C5H5), 4.19−4.21 (m, 1 H, C5H3), 4.26−4.36 (m,
2 H, CH2), 7.32−7.35 (m, 2 H, 2,6-C6H5), 7.40−7.43 (m, 1 H, 4-
C6H5), 7.46−7.54 (m, 3 H, 2,4,6-C6H5), 7.62−7.64 (m, 2 H, 3,5-
C6H5), 7.91−7.93 (m, 2 H, 3,5-C6H5). 13C{1H} NMR (CDCl3, δ):
16.1955(11) Å, α = 104.659(6)°, β = 92.163(5)°, γ = 98.373(5)°, V =
1460.35(17) Å3, Z = 4, ρcalcd = 1.674 Mg m−3, μ = 1.064 mm−1, T =
110(2) K, θ range 2.961−25.000°, 9912 reflections collected, 9912
independent reflections (Rint = 0.0291),53 R1 = 0.0397, wR2 = 0.0830
(I > 2σ(I)).
1-Ferrocenyloxy-4-nitrobenzene (4b). To ferrocenol (1a−H;
247 mg, 1.22 mmol) dissolved in toluene (10 mL) was added BuLi
(0.50 mL, 1.25 mmol) dropwise at −30 °C. Afterward, the general
procedure for the SNAr reaction was applied using 1-fluoro-4-
nitrobenzene (3b; 86 mg, 0.61 mmol). Dicyclohexylamine (110 mg,
0.60 mmol) was added, and stirring at 70 °C was continued for 3 h.
Afterward, the reaction mixture was cooled to ambient temperature
and extracted with diethyl ether (3 × 50 mL) and all volatiles were
removed under reduced pressure. Purification was performed by
column chromatography (silica, 4 × 10 cm) using a 1/1 hexane/
dichloromethane mixture (v/v) as the eluent. The title compound 4b
was obtained as a dark orange solid. Suitable single crystals were
obtained by recrystallization from boiling hexane.
3
3
16.4 (d, JC,P = 6.8 Hz, CH3), 16.6 (d, JC,P = 7.2 Hz, CH3), 19.4
1
(C(CH3)3), 26.5 (C(CH3)3), 57.1 (d, JC,P = 215.8 Hz, C−P), 61.4−
61.5 (m, CH2), 62.1 (d, JC,P = 11.3 Hz, C5H3), 63.8 (d, JC,P = 14.4 Hz,
C5H3), 66.3 (d, JC,P = 14.2 Hz, C5H3), 70.5 (C5H5), 123.0 (d, JC,P
2
=
9.0 Hz, CC H −O), 127.6 (2,6-C6H5), 127.8 (2,6-C6H5), 130.0 (4-
5
3
C6H5), 130.2 (4-C6H5), 132.1 (1-C6H5), 133.4 (1-C6H5), 135.6 (3,5-
C6H5), 135.8 (3,5-C6H5). 29Si{1H} NMR (CDCl3, δ): − 3.1. 31P{1H}
NMR (CDCl3, δ): 24.9. HRMS (ESI-TOF, m/z): calcd for
C30H37FeO4PSi 576.1543, found 576.1596 [M]+.
2-Triisopropylsilyloxyferrocenyl O,O-Diethyl Phosphonate
(rac-2h). In accordance with compound 2g, diethylferrocenyl
phosphate5 (17; 1.122 g, 3.32 mmol), diisopropylamine (0.92 mL,
6.64 mmol), BuLi (2.65 mL, 6.63 mmol), and tmeda (0.95 mL, 6.63
mmol) were reacted according to the general procedure A for anionic
Fries rearrangements. Afterward, ClSiiPr3 (1.4 mL, 6.63 mmol) was
added in a single portion at −30 °C. The cooling bath was removed,
and stirring was continued at ambient temperature for 18 h.
Purification was performed by column chromatography (silica, 2 ×
15 cm) using a 7/3 dichloromethane/ethyl acetate mixture (v/v) as
the eluent. All volatiles were removed in vacuo, and compound rac-2h
was obtained as an orange oil.
Yield: 184 mg (0.57 mmol, 74% based on 1a−H). Anal. Calcd for
C16H13FeN1O3 (323.12 g/mol): C, 59.47; H, 4.06; N, 4.33. Found: C,
59.96; H, 4.05; N, 4.29. Mp: 102−104 °C. 1H NMR (CDCl3, δ): 4.05
3+4
(pt,
J
= 2.0 Hz, 2 H, H2,5-C5H4), 4.28 (pt, 3+4JH,H = 2.0 Hz, 2 H,
H,H
H3,4-C5H4), 4.32 (s, 5 H, C5H5), 6.96−7.00 (m, 2 H, H2,6-C6H4),
8.13−8.16 (m, 2 H, H3,5-C6H4). 13C{1H} NMR (CDCl3, δ): 61.0
(C3,4-C5H4), 63.8 (C2,5-C5H4), 69.7 (C5H5), 115.8 (C2,6-C6H4),
119.9 (C −O), 125.6 (C3,5-C6H4), 142.3 (C4−C6H4), 164.8 (C1−
C5H4
C6H4). HRMS (ESI-TOF, m/z): calcd for C16H13FeN1O3 323.0239,
found 323.0257 [M]+.
Crystal data for 4b: C16H13FeNO3, Mr = 323.12 g mol−1
,
Yield: 845 g (1.71 mmol, 52% based on 17). 1H NMR (CDCl3, δ):
1.07 (d, 3JH,H = 7.1 Hz, 9 H, CH(CH3)2), 1.14 (d, 3JH,H = 7.1 Hz, 9 H,
CH(CH3)2), 1.17−1.24 (m, 3 H, CH(CH3)2), 1.29 (t, 3JH,H = 7.1 Hz,
3 H, CH2−CH3), 1.39 (t, 3JH,H = 7.1 Hz, 3 H, CH2−CH3), 3.95−3.96
(m, 1 H, C5H3), 4.02−4.14 (m, 2 H, CH2), 4.17−4.31 (m, 9 H, C5H5,
monoclinic, P21/n, λ = 0.71073 Å, a = 11.065(3) Å, b = 10.792(2)
Å, c = 11.8254(16) Å, β = 107.86(2)°, V = 1344.1(5) Å3, Z = 4, ρcalcd
=
1.597 Mg m−3, μ = 1.131 mm−1, T = 110(2) K, θ range 2.904−
24.999°, 4798 reflections collected, 2356 independent reflections (Rint
= 0.0536), R1 = 0.0483, wR2 = 0.0790 (I > 2σ(I)).
J
DOI: 10.1021/acs.organomet.6b00157
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
1,5-(Ferrocenyloxy)-2,4-dinitrobenzene (7a). To ferrocenol
(1a−H; 651 mg, 3.22 mmol) dissolved in toluene (10 mL) was
added BuLi (1.30 mL, 3.3 mmol) dropwise. Afterward, the general
procedure for SNAr reactions was applied using 1,5-difluoro-2,4-
dinitrobenzene (5; 328 mg, 1.61 mmol). Purification was performed
by column chromatography (silica, 4 × 10 cm) using a 1/1 hexane/
dichloromethane mixture (v/v) as the eluent. All volatiles were
removed in vacuo, and compound 7a was obtained as a reddish orange
solid. Suitable single crystals were obtained by recrystallization from
boiling hexane.
Crystal data for 7c: C18H17FeN3O5, Mr = 411.19 g mol−1
,
orthorhombic, P212121, λ = 0.71073 Å, a = 7.5258(7) Å, b =
10.2827(9) Å, c = 21.647(3) Å, V = 1675.1(3) Å3, Z = 4, ρcalcd = 1.630
Mg m−3, μ = 0.938 mm−1, T = 110(2) K, θ range 3.297−24.996°, 5577
reflections collected, 2899 independent reflections (Rint = 0.0669), R1
= 0.0877, wR2 = 0.1995 (I > 2σ(I)), absolute structure parameter28
0.50(2).
1,2-(Ferrocenyloxy)-4,5-dinitrobenzene (8). To ferrocenol
(1a−H; 864 mg, 4.25 mmol) dissolved in toluene (10 mL) was
added BuLi (1.70 mL) dropwise. Afterward, the general procedure for
SNAr reactions was applied using 1,2-difluoro-4,5-dinitrobenzene (6;
437 mg, 2.14 mmol). Purification was performed by column
chromatography (silica, 4 × 10 cm) using a 1/1 hexane/dichloro-
methane mixture (v/v) as the eluent. All volatiles were removed in
vacuo, and compound 8 was obtained as reddish orange crystals.
Crystals suitable for a single-crystal X-ray diffraction analysis were
obtained by recrystallization from boiling toluene.
Yield: 148 mg (0.26 mmol, 16% based on 1a−H). Anal. Calcd for
C26H20Fe2N2O6 (568.14 g/mol): C, 54.97; H, 3.55; N, 4.93. Found: C,
54.90; H, 3.48; N, 5.03. Mp: 167−170 °C. 1H NMR (CDCl3, δ): 3.96
3+4
3+4
(pt,
J
= 2.0 Hz, 4 H, C5H4), 4.19 (pt,
J
= 2.0 Hz, 4 H,
H,H
H,H
C5H4), 4.29 (s, 10 H, C5H5), 6.68 (s, 1 H, H6), 8.75 (s, 1 H, H3).
13C{1H} NMR (CDCl3, δ): 60.5 (C5H4), 64.0 (C5H4), 70.0 (C5H5),
104.3 (C6−C6H2), 119.5 (CC H −O), 125.1 (C3−C6H2), 132.0
5
4
Yield: 700 mg (1.02 mmol, 48% based on 1a−H). Anal. Calcd for
(C2,C4−C6H2), 157.9 (C1,C5−C6H2). HRMS (ESI-TOF, m/z):
C26H20Fe2N2O6·1/6C6H14 (568.14·1/6(86.18) g/mol): C, 55.67; H,
calcd for C26H20Fe2N2O6 568.0015, found 568.0039 [M]+.
3.86; N, 4.81. Found: C, 55.69; H, 3.99; N, 4.58. Mp: 182−184 °C. 1H
Crystal data for 7a: C26H20Fe2N2O6, Mr = 568.14 g mol−1,
monoclinic, P21, λ = 0.71073 Å, a = 7.6777(6) Å, b = 10.0784(6) Å, c
3+4
NMR (CDCl3, δ): 4.10 (pt,
J
= 2.0 Hz, 4 H, C5H4), 4.35−4.36
H,H
(m, 14 H, C5H4), 7.49 (s, 2 H, C6H2). 13C{1H} NMR (CDCl3, δ):
60.4 (C5H4), 64.1 (C5H4), 69.8 (C5H5), 111.7 (C3,6-C6H2), 120.4
(CC H −O), 137.1 (C4,5-C6H2), 151.7 (C1,2-C6H2). HRMS (ESI-
= 14.2577(13) Å, β = 105.261(9)°, V = 1064.34(15) Å3, Z = 2, ρcalcd
=
1.773 Mg m−3, μ = 1.414 mm−1, T = 110(2) K, θ range 3.413−
24.999°, 6350 reflections collected, 3045 independent reflections (Rint
= 0.0672), R1 = 0.0545, wR2 = 0.1061 (I > 2σ(I)), absolute structure
parameter28 0.22(4).
5
4
TOF, m/z): calcd for C26H20Fe2N2O6 568.0015, found 568.0000
[M]+.
Crystal data for 8: C27H21Cl3Fe2N2O6, Mr = 687.51 g mol−1,
monoclinic, C2/c, λ = 0.71073 Å, a = 19.9437(9) Å, b = 9.7162(5) Å, c
1-Ferrocenyloxy-5-fluoro-2,4-dinitrobenzene (7b). The title
compound 7b was obtained as a side product within the synthesis of
7a by reacting ferrocenol (1a−H; 651 mg, 3.22 mmol), BuLi (1.30
mL, 3.3 mmol), and 1,5-difluoro-2,4-dinitrobenzene (5; 328 mg, 1.61
mmol). Purification was performed by column chromatography (silica,
4 × 10 cm) using a 1/1 hexane/dichloromethane mixture (v/v). All
volatiles were removed in vacuo, and compound 7b was obtained as an
orange solid. Suitable single crystals were obtained by recrystallization
from hexane.
= 28.3252(14) Å, β = 94.255(4)°, V = 5473.6(5) Å3, Z = 8, ρcalcd
=
1.669 Mg m−3, μ = 1.399 mm−1, T = 110(2) K, θ range 2.884−
25.498°, 16021 reflections collected, 5094 independent reflections
(Rint = 0.0364), R1 = 0.0357, wR2 = 0.0857 (I > 2σ(I)).
O,O-Dicyclohexyl (2-(2,4-Dinitrophenoxy)ferrocenyl)-
phosphonate (rac-11a). Dicyclohexyl ferrocenyl phosphate (9;
200 mg, 0.45 mmol), diisopropylamine (0.13 mL, 0.90 mmol), BuLi
(0.36 mL, 0.9 mmol), and tmeda (0.14 mL, 0.93 mmol) were reacted
according to the general procedure B for anionic Fries rearrangements.
Afterward, 3a (250 mg, 1.34 mmol) was applied within the general
procedure for SNAr reactions. Purification was performed by column
chromatography (silica, 2 × 15 cm) using a 9/1 dichloromethane/
ethyl acetate mixture (v/v) as the eluent. All volatiles were removed in
vacuo, and compound rac-11a was obtained as an orange oil.
Yield: 200 mg (0.52 mmol, 16% based on 1a−H). Anal. Calcd for
C16H11FFeN2O5·0.3C6H14 (386.11·0.3(86.18) g/mol): C, 52.12; H,
3.81; N, 6.75. Found: C, 51.71; H, 3.41; N, 6.86. Mp: 150−152 °C. 1H
3+4
NMR (CDCl3, δ):. 4.13 (pt,
J
= 2.0 Hz, 2 H, C5H4), 4.37−4.38
H,H
(m, 7 H, C5H5, C5H4), 6.87 (d, 3JH,F = 11.9 Hz, 1 H, H6), 8.83 (d, 4JH,F
= 7.6 Hz, 1 H, H3). 13C{1H} NMR (CDCl3, δ): 61.1 (C5H4), 64.6
(C5H4), 70.2 (C5H5), 106.2 (d, 2JC,F = 26.5 Hz, C6), 119.3 (CC H −O),
5
4
Yield: 135 mg (0.22 mmol, 49% based on 9). 1H NMR (CDCl3, δ):
1.22−1.39 (m, 10 H, CH2), 1.48−1.53 (m, 3 H, CH2), 1.58−1.68 (m,
3 H, CH2), 1.72−1.81 (m, 2 H, CH2), 1.83−1.89 (m, 1 H, CH2),
1.91−2.00 (m, 1 H, CH2), 4.27 (dd, JH,H = 2.7 Hz, JH,H = 2.7 Hz, 1 H,
C5H3), 4.31−4.38 (m, 1 H, CH), 4.39−4.47 (m, 7 H, CH, C5H5,
125.1 (C3), 130.2 (d, 2JC,F = 7.9 Hz, C4), 134.4 (d, 4JC,F = 2.6 Hz, C2),
158.5 (d, 1JC,F = 273.9 Hz, C5), 159.1 (d, 3JC,F = 10.9 Hz, C1). HRMS
(ESI-TOF, m/z): calcd for C16H11FeN2O5F 385.9996, found 386.0024
[M]+.
Crystal data for 7b: C16H11FeN2O5F, Mr = 386.12 g mol−1,
monoclinic, P21/n, λ = 0.71073 Å, a = 18.0108(4) Å, b = 7.4492(2) Å,
3
C5H3), 4.52 (m, 1 H, C5H3), 7.01 (d, JH,H = 9.3 Hz, 1 H, H6), 8.24
3
4
(dd, JH,H = 9.3 Hz, 4JH,H = 2.7 Hz, 1 H, H5), 8.79 (d, JH,H = 2.6 Hz,
c = 22.7498(6) Å, β = 107.779(2)°, V = 2906.48(13) Å3, Z = 8, ρcalcd
=
H3). 13C{1H} NMR (CDCl3, δ): 23.6−23.7 (m, CH2), 25.1 (CH2),
1.765 Mg m−3, μ = 1.083 mm−1, T = 110(2) K, θ range 2.892−
24.994°, 14857 reflections collected, 5109 independent reflections
(Rint = 0.0314), R1 = 0.0354, wR2 = 0.0773 (I > 2σ(I)).
1
33.6−33.7 (m, CH2), 33.8−33.9 (CH2), 63.4 (d, JC,P = 219.2 Hz,
CC H −P), 64.5 (d, JC,P = 10.1 Hz, C5H3), 66.14 (d, JC,P = 13.6 Hz,
5
3
C5H3), 68.8 (d, JC,P = 13.6 Hz, C5H3), 71.9 (C5H5), 75.5 (d, 2JC,P = 6.7
5-Ferrocenyloxy-N,N-dimethyl-2,4-dinitroaniline (7c). The
title compound 7c was obtained as a side product within the synthesis
of 7a by reacting ferrocenol (1a−H; 651 mg, 3.22 mmol), BuLi (1.30
mL, 3.3 mmol), and 1,5-difluoro-2,4-dinitrobenzene (5; 328 mg, 1.61
mmol). Purification was performed by column chromatography (silica,
4 × 10 cm) using a 1/1 hexane/dichloromethane mixture (v/v). All
volatiles were removed in vacuo, and compound 7c was obtained as an
orange solid. Suitable single crystals were obtained by recrystallization
from boiling hexane.
2
2
Hz, CH), 75.7 (d, JC,P = 6.3 Hz, CH), 117.4 (C6), 119.3 (d, JC,P
=
9.2 Hz, CC H −O), 121.6 (C3), 128.5 (C5), 138.3 (C2), 141.0 (C4),
5
3
157.6 (C1). 31P{1H} NMR (CDCl3, δ): 19.1 (1JC,P = 219.2 Hz).
HRMS (ESI-TOF, m/z): calcd for C28H33FeN2PO8 + H 613.1397,
found 613.1347 [M + H]+ (50%); calcd for C28H33FeN2PO8 + Na
635.1217, found 635.1217 [M + Na]+ (100%); calcd for
(C28H33FeN2PO8)2 + Na 1247.2543, found 1247.2400 [M2 + Na]+
(35%).
Yield: 132 mg (0.32 mmol, 10% based on 1a−H). Mp: 170 °C. 1H
O,O-Dicyclohexyl (2-(4-Nitrophenoxy)ferrocenyl)-
phosphonate (rac-11b). Dicyclohexyl ferrocenyl phosphate (9;
200 mg, 0.45 mmol), diisopropylamine (0.13 mL, 0.90 mmol), BuLi
(0.36 mL, 0.9 mmol), and tmeda (0.14 mL, 0.93 mmol) were reacted
according to the general procedure B for anionic Fries rearrangements.
Afterward, 3b (190 mg, 1.34 mmol) was applied in the general
procedure for SNAr reactions. Purification was performed by column
chromatography (silica, 2 × 15 cm) using a 9/1 dichloromethane/
NMR (CDCl3, δ): 2.85 (s, 6 H, CH3), 4.06 (pt, 3+4JH,H = 2.0 Hz, 2 H,
3+4
C5H4), 4.35 (pt,
J
= 2.0 Hz, 2 H, C5H4), 4.36 (s, 5 H, C5H5),
H,H
6.26 (s, 1 H, H6), 8.69 (s, 1 H, H3). 13C{1H} NMR (CDCl3, δ): 42.3
(CH3), 61.1 (C5H4), 64.0 (C5H4), 70.0 (C5H5), 102.3 (C6−C6H2),
119.2 (CC H −O), 127.6 (C3−C6H2), 128.1 (C2/C4−C6H2), 130.6
5
4
(C2/C4−C6H2), 149.7 (C1−C6H2), 157.9 (C5−C6H2). HRMS (ESI-
TOF, m/z): calcd for C18H17FeN3O5 411.0512, found 411.0544 [M]+.
K
DOI: 10.1021/acs.organomet.6b00157
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
C5H2), 73.8 (s, C5H5), 76.0 (d, 2JC,P = 6.9 Hz, C
−O), 76.2 (d, 2JC,P
ethyl acetate mixture (v/v) as the eluent. All volatiles were removed in
C6H11
vacuo, and compound rac-11b was obtained as an orange oil.
2
= 6.5 Hz, CC H −O), 117.8 (C6−C6H3), 118.6 (t, JC,P = 9.5 Hz,
1
6
11
Yield: 85 mg (0.15 mmol, 33% based on 9). H NMR (CDCl3, δ):
CC H −O), 121.7 (C3−C6H3), 128.3 (C5−C6H3), 137.9 (C2−C6H3),
1.23−1.33 (m, 6 H, CH2), 1.38−1.52 (m, 6 H, CH2), 1.64−1.72 (m, 4
H, CH2), 1.79−1.88 (m, 4 H, CH2), 4.23 (dd, JH,H = 2.7 Hz, JH,H = 2.7
Hz, 1 H, C5H3), 4.35−4.44 (m, 9 H, CH, C5H5, C5H3), 6.92−6.95 (m,
2 H, H2,6), 8.12−8.15 (m, 2 H, H3,5). 13C{1H} NMR (CDCl3, δ):
23.4−23.5 (m, CH2), 25.17 (CH2), 25.19 (CH2), 33.6−33.8 (m,
5
2
141.1 (C4−C6H3), 157.4 (C1−C6H3). 31P{1H} NMR (CDCl3, δ):
17.4 (1JC,P = 215.1 Hz). HRMS (ESI-TOF, m/z): calcd for
C40H54FeN2O11P2 + H 857.2626, found 857.2593 [M + H]+
(100%); calcd for C40H54FeN2O11P2 + Na 879.2445, found
879.2407 [M + Na]+ (79%).
1
CH2), 62.8 (d, JC,P = 218.3 Hz, CC H −P), 64.5 (d, JC,P = 10.6 Hz,
5
3
(Rp)-O,O-Bis((1R)-α-fenchyl)-2-(2,4-dinitrophenyloxy)-
ferrocenyl Phosphonate ((Rp)-16a). Bis((1R)-α-fenchyl) ferrocenyl
phosphate5 (15; 521 mg, 0.94 mmol), litmp (227 mg, 1.88 mmol), and
tmeda (0.28 mL, 1.88 mmol) were reacted according to the general
procedure C for the anionic phospho-Fries rearrangement. Afterward,
3a (524 mg, 2.82 mmol) was applied within the general procedure for
SNAr reactions. Purification was performed by column chromatog-
raphy (silica, 2 × 20 cm) using a 98/2 dichloromethane/ethyl acetate
mixture (v/v) as the eluent. All volatiles were removed in vacuo, and
compound (Rp)-16a was obtained as an orange oil as a mixture of two
diastereomers (de = 0.81). Except as otherwise noted, merely the
signals of the main diastereomer are reported.
C5H3), 65.7 (d, JC,P = 13.7 Hz, C5H3), 68.6 (d, JC,P = 13.4 Hz, C5H3),
2
2
71.5 (C5H5), 75.1 (d, JC,P = 6.9 Hz, CH), 75.2 (d, JC,P = 6.1 Hz,
2
CH), 115.9 (C2,6-C6H4), 120.1 (d, JC,P = 9.7 Hz, CC H −O), 125.4
5
3
(C3,5-C6H4), 142.4 (C4−C6H4), 164.6 (C1−C6H4). 31P{1H} NMR
(CDCl3, δ): 19.3 (1JC,P = 218.4 Hz). HRMS (ESI-TOF, m/z): calcd
for C28H34FeNO6P + Na 590.1366, found 590.1331 [M + Na]+.
2-(2,4-Dinitrophenoxy)-1-((trifluoromethyl)sulfonyl)-
ferrocene (rac-12a). Ferrocenyl triflate (10; 150 mg, 0.45 mmol),
diisopropylamine (0.13 mL, 0.94 mmol), and BuLi (0.18 mL, 0.45
mmol) were reacted according to the general procedure A for anionic
Fries rearrangements at −80 °C. Afterward, the reaction mixture was
warmed to 0 °C and 3a (167 mg, 0.90 mmol) was applied within the
general procedure for SNAr reactions. Purification was performed by
column chromatography (silica, 2 × 15 cm) using a 1/1 hexane/
dichloromethane mixture (v/v) as the eluent. All volatiles were
removed in vacuo, and compound rac-12a was obtained as an orange
oil. Crystals suitable for single-crystal X-ray diffraction analysis were
grown from a hexane solution containing rac-12a at ambient
temperature.
1
Yield: 230 mg (0.32 mmol, 34% based on 15). H NMR (CDCl3,
δ): 067 (s, 3 H, CH3), 0.76 (s, 3 H, CH3), 0.90 (s, 3 H, CH3), 0.99 (s,
3 H, CH3), 1.08−1.21 (m, 10 H), 1.52−1.87 (m, 10 H), 3.96 (dd, JH,H
= 1.68 Hz, JH,H = 10.1 Hz, 1 H, C5H3), 4.15 (dd, JH,H = 1.68 Hz, JH,H
=
10.1 Hz, 1 H, C5H3), 4.29 (m, 1 H, C5H3), 4.47−4.50 (m, 2 H, H2),
4.53 (s, 5 H, C5H5), 7.34 (d, 3JH,H = 9.3 Hz, 1 H, H6), 8.31 (dd, 3JH,H
= 9.3 Hz, 4JH,H = 2.7 Hz, 1 H, H5), 8.83 (d, 3JH,H = 2.7 Hz, 1 H, H3).
13C{1H} NMR (CDCl3, δ): 19.6 (CH3), 19.8 (CH3), 21.0 (CH3), 21.6
(CH3), 25.8 (C5/6), 25.9 (C5/6), 26.0 (C5/6), 26.1 (C5/6), 29.5
Yield: 180 mg (0.36 mmol, 80% based on 10). Anal. Calcd for
C17H11F3FeN2O7S·0.17C6H14 (500.18·0.17(86.18) g/mol): C, 42.02;
H, 2.61; N, 5.44. Found: C, 41.78; H, 2.43; N, 5.54. Mp: 172−174 °C.
1H NMR (CDCl3, δ): 4.62 (pt, 3+4JH,H = 2.9 Hz, 1 H, C5H3), 4.72 (s, 5
3
3
(CH3), 30.1 (CH3), 39.2 (d, JC,P = 2.3 Hz, C3), 39.6 (d, JC,P = 2.3
3
Hz, C3), 41.1 (C7), 41.2 (C7), 47.8 (C4), 47.9 (C4), 49.3 (d, JC,P
=
H, C5H5), 4.73 (dd, JH,H = 2.9 Hz, JH,H = 1.5 Hz, 1 H, C5H3), 4.88 (dd,
JH,H = 2.9 Hz, JH,H = 1.5 Hz, 1 H, C5H3), 7.00 (d, 3JH,H = 9.2 Hz, 1 H,
H6), 8.33 (dd, 3JH,H = 9.2 Hz, 4JH,H = 2.7 Hz, 1 H, H5), 8.84 (d, 4JH,H
= 2.7 Hz, 1 H, H3). 13C{1H} NMR (CDCl3, δ): 67.0 (C5H3), 68.0
(C5H3), 69.8 (C5H3), 69.4 (q, 3JC,F = 2.3 Hz, C2−C5H3), 73.7 (C5H5),
4.8 Hz, C1), 49.5 (d, 3JC,P = 4.1 Hz, C1), 61.9 (d, 1JC,P = 217.9 Hz, C−
P), 63.7 (d, JC,P = 10.2 Hz, C5H3), 66.1 (d, JC,P = 13.3 Hz, C5H3), 68.8
2
(d, JC,P = 12.7 Hz, C5H3), 71.9 (C5H5), 88.6 (d, JC,P = 7.0 Hz, C2),
2
2
89.5 (d, JC,P = 7.1 Hz, C2), 118.3 (C6−C6H3), 120.8 (d, JC,P = 7.0
Hz, CC H −O), 122.0 (C3−C6H3), 128.4 (C5−C6H3), 139.3 (C2−
5
4
1
117.1 (C6), 119 (q, JC,F = 325.6 Hz, CF3), 119.6 (CC H −O), 122.1
C6H3), 141.4 (C4−C6H3), 157.0 (C1−C6H3). 31P{1H} NMR (CDCl3,
δ): 20.5. HRMS (ESI-TOF, m/z): calcd for C36H45FeN2O8P+Na
743.2156, found 743.2149 [M + Na]+.
5
3
(C3), 128.6 (C5), 139.3 (C2), 142.1 (C4), 156.1 (C1). HRMS (ESI-
TOF, m/z): calcd for C17H11FeN2O7SF3 + Na 522.9481, found
522.9499 [M + Na]+.
(Rp)-O,O-Bis((1R)-α-fenchyl)-2-(4-nitrophenyloxy)ferrocenyl
Phosphonate ((Rp)-16b). Bis((1R)-α-fenchyl) ferrocenyl phosphate
(15; 1.00 g, 1.80 mmol), litmp (530 mg, 3.61 mmol), and tmeda (0.54
mL, 3.61 mmol) were reacted according to the general procedure C
for the anionic phospho-Fries rearrangement. Afterward, 3b (763 mg,
5.41 mmol) was applied within the general procedure for SNAr
reactions. Purification was performed by column chromatography
(silica, 2 × 14 cm) using a 95/5 dichloromethane/ethyl acetate
mixture (v/v) as the eluent. All volatiles were removed in vacuo, and
compound (Rp)-16b was obtained as an orange oil as a mixture of two
diastereomers (de = 0.74).
Crystal data for rac-12a: C17H11F3FeN2O7S, Mr = 500.19 g mol−1,
triclinic, P1, λ = 0.71073 Å, a = 7.4788(5) Å, b = 8.7046(5) Å, c =
̅
14.8166(9) Å, α = 99.292(5)°, β = 92.546(5)°, γ = 105.141(5)°, V =
915.05(10) Å3, Z = 2, ρcalcd = 1.815 Mg m−3, μ = 1.015 mm−1, T =
110(2) K, θ range 3.044−25.499°, 6303 reflections collected, 3387
independent reflections (Rint = 0.0270), R1 = 0.0357, wR2 = 0.0811 (I
> 2σ(I)).
O,O,O′,O′-Tetracyclohexyl (2-(2,4-dinitrophenoxy)-
ferrocenyl-1,3-diyl)bis(phosphonate) (rac-13a). O,O-Dicyclohex-
yl 2-(O′,O′-dicyclohexyl phosphato) ferrocenyl phosphonate5 (11c;
200 mg, 0.29 mmol), diisopropylamine (0.1 mL, 0.58 mmol), BuLi
(0.24 mL, 0.6 mmol), and tmeda (0.09 mL, 0.68 mmol) were reacted
according to the general procedure B for anionic Fries rearrangements.
Afterward, 3a (162 mg, 0.87 mmol) was applied within the general
procedure for SNAr reactions. Purification was performed by column
chromatography (silica, 2 × 15 cm) using a 98/2 ethyl acetate/
methanol mixture (v/v) as the eluent. All volatiles were removed in
vacuo, and compound rac-13a was obtained as an orange oil.
Yield: 113 mg (0.17 mmol, 9% based on 15). Except as otherwise
1
noted, merely the signals of the main diastereomer are reported. H
NMR (CDCl3, δ): 0.73 (s, 3H, CH3), 0.82−1.84 (m, 31 H, C10H17),
3.63 (dd, 3JH,P = 9.8 Hz, JH,H = 1.6 Hz, 1 H, H2), 4.16 (dd, 3JH,P = 9.8
3+4
Hz, JH,H = 1.7 Hz, 1 H, H2), 4.25 (dd,
J
= 2.5 Hz, 1 H, C5H3),
H,H
4.34−4.36 (m, 1 H, C5H3), 4.46 (s, minor, C5H5), 4.47 (s, 5 H, C5H5),
4.50−4.51 (m, 1 H, C5H3), 7.14−7.17 (m, 2 H, 2,6-C6H4), 8.16−8.20
(m, 2 H, 3,5-C6H4). 13C{1H} NMR (CDCl3, δ): 19.3 (CH3), 19.8
(CH3), 21.3 (CH3), 21.6 (CH3), 25.8 (C5/C6), 26.0 (C5/C6), 26.1
1
Yield: 177 mg (0.21 mmol, 73% based on 11c). H NMR (CDCl3,
δ): 1.16−1.39 (m, 16 H, CH2), 1.47−1.55 (m, 6 H, CH2), 1.62−1.85
(m, 16 H, CH2), 1.94−1.97 (m, 4 H, CH2), 4.30−4.43 (m, 4 H, CH),
4.58−4.59 (m, 6 H, C5H5, C5H2), 4.67−4.76 (m, 1 H, C5H2), 6.93 (d,
3
(C5/C6), 29.1 (CH3), 29.9 (CH3), 39.3 (d, JC,P = 1.9 Hz, C3), 39.4
3
(d, JC,P = 1.3 Hz, C3), 40.8 (C7), 41.1 (C7), 47.9 (C4), 48.0 (C4),
49.1 (d, 3JC,P = 5.8 Hz, C1), 49.4 (d, 3JC,P = 4.8 Hz, C1), 60.6 (d, 1JC,P
= 216.5 Hz, C−P), 63.7 (d, JC,P = 10.8 Hz, C5H3), 65.7 (d, JC,P = 13.2
Hz, C5H3), 68.0 (d, JC,P = 11.8 Hz, C5H3), 71.3 (C5H5, minor), 71.5
3
3JH,H = 6.9 Hz, 0.8 H, H6), 7.02 (d, JH,H = 8.9 Hz, 0.2 H, H6), 8.22
3
4
3
(dd, JH,H = 9.3 Hz, JH,H = 2.7 Hz, 0.8 H, H5), 8.26 (dd, JH,H = 9.3
4
4
Hz, JH,H = 2.7 Hz, 0.2 H, H5), 8.81 (d, JH,H = 2.7 Hz, 0.8 H, H3),
8.84 (d, 4JH,H = 2.7 Hz, 0.2 H, H3). 13C{1H} NMR (CDCl3, δ): 23.4−
23.8 (m, CH2), 25.0−25.1 (m, CH2), 33.5−33.9 (m, CH2), 67.0 (dd,
2
2
(C5H5, major), 87.8 (d, JC,P = 6.1 Hz, C2), 89.1 (d, JC,P = 7.5 Hz,
2
C2), 116.8 (2,6-C6H4), 121.6 (d, JC,P = 10.5 Hz, CC H −O), 125.5
5
3
1JC,P = 216.6 Hz, JC,P = 9.1 Hz, C−P), 70.3 (pt,
J
C,P
= 13.8 Hz,
(3,5-C6H4), 142.6 (C4−C6H4), 163.9 (C1−C6H4). 31P{1H} NMR
3
2,3
L
DOI: 10.1021/acs.organomet.6b00157
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(CDCl3, δ): 21.2 (100%), 22.2 (6%), 22.5 (9%). HRMS (ESI-TOF,
m/z): calcd for C36H46FeNO6P 675.2407, found 675.2395 [M]+.
(20) (a) Lindstedt, E.; Ghosh, R.; Olofsson, B. Org. Lett. 2013, 15,
6070−6073. (b) Bielawski, M.; Olofsson, B. Chem. Commun. 2007,
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Olofsson, B. Org. Lett. 2011, 13, 1552−1555. (e) Hossain, D.; Ikegami,
Y.; Kitamura, T. J. Org. Chem. 2006, 71, 9903−9905.
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.6b00157.
(21) Eustathopoulos, H.; Court, J.; Bonnier, J.-M. J. Chem. Soc.,
Perkin Trans. 2 1983, 803−807.
(22) A test reaction using diphenyliodonium tetrafluoroborate and 4-
tert-butylphenol yielded the desired 1-tert-butyl-4-phenoxybenzene in
95% yield. For the NMR data of the product see: Jammi, S.; Sakthivel,
S.; Rout, L.; Mukherjee, T.; Mandal, S.; Mitra, M.; Saha, P.;
Punniyamurthy, T. J. Org. Chem. 2009, 74, 1971−1976.
Additional experimental and crystallographic data as well
as spectroscopic details for all new compounds (PDF)
Crystallographic data (CIF)
(23) (a) Yeom, C.-E.; Kim, H. W.; Lee, S. Y.; Kim, B. M. Synlett
2007, 2007, 0146−0150. (b) Raders, S. M.; Verkade, J. G. Tetrahedron
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377−379. (d) Pirkle, W. H.; Zabriskie, J. L. J. Org. Chem. 1964, 29,
3124−3126.
(24) Matsumoto, K.; Komuro, H.; Kai, T.; Jikei, M. Polym. J. 2013,
45, 909−914.
AUTHOR INFORMATION
Corresponding Author
*E-mail for H.L.: heinrich.lang@chemie.tu-chemnitz.de.
Notes
■
The authors declare no competing financial interest.
(25) Cook, H. G.; Saunders, B. C. Biochem. J. 1947, 41, 558−559.
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1999, 64, 3373−3375. (b) Davies, S. G.; Hume, W. E.; Roberts, P. M.;
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Mahaffy, C. A. L. Synth. React. Inorg. Met.-Org. Chem. 1986, 16, 1363−
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ACKNOWLEDGMENTS
M.K. thanks the Fonds der Chemischen Industrie for a Ph.D.
Chemiefonds fellowship.
■
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N
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