Preparation of 2-arylated-1,4-phenylenediamines by palladium-catalyzed cross-coupling reactions

Article abstract of DOI:10.1016/S0022-328X(02)01156-7

Protected 2-iodol-1,4-phenylenediamines were converted to the corresponding magnesium derivative by performing an iodine-magnesium exchange. After transmetalation with zinc bromide, a palladium(0)-catalyzed cross-coupling with various aryl iodides and 5-bromo-2-carbethoxyfuran furnished the expected cross-coupling products in 52-79% yield.

Full text of DOI:10.1016/S0022-328X(02)01156-7

Journal of Organometallic Chemistry 653 (2002) 122–128
www.elsevier.com/locate/jorganchem
Preparation of 2-arylated-1,4-phenylenediamines by
palladium-catalyzed cross-coupling reactions
Anne Eeg Jensen, Paul Knochel *
Department Chemie, Ludwig-Maximilians-Uni6ersita¨t Mu¨nchen, Butenandtstr. 5-13, Building F, D-81377 Munich, Germany
Received 28 August 2001; accepted 27 September 2001
Abstract
Protected 2-iodo-1,4-phenylenediamines were converted to the corresponding magnesium derivative by performing an iodine–
magnesium exchange. After transmetalation with zinc bromide, a palladium(0)-catalyzed cross-coupling with various aryl iodides
and 5-bromo-2-carbethoxyfuran furnished the expected cross-coupling products in 52–79% yield. © 2002 Elsevier Science B.V. All
rights reserved.
Keywords: Cross-coupling; Palladium; Zinc; Magnesium; Polyfunctional organometallics
,
1. Introduction
(4 A) at 120 °C (2 h reaction time). The tetraallylated
amine (3) is prepared by treatment of 1 with allyl
bromide (16 equivalents) in the presence of sodium
carbonate (eight equivalents) in DMF (100 °C, 3 h) [6]
(Scheme 1).
Preliminary experiments indicate that for both sub-
strates (2 and 3), the iodine–magnesium exchange oc-
The preparation of polyfunctional aryl- and het-
eroaryl magnesium reagents obtained by an iodine–
magnesium exchange has opened paths to a wide range
of functional products using these new functionalized
organomagnesium reagents as key intermediates [1,2].
Recently, we have shown that functionalized magnesi-
ated aniline derivatives can be prepared and reacted
with various electrophiles [3]. Herein, we wish to report
the preparation of 2-magnesiated-1,4-phenylenedi-
amines and their use in cross-coupling reactions with
various aryl halides.
curs smoothly (THF, −10 °C,
3
h). After
transmetalation with CuCN·2LiCl [7], a clean allylation
with allyl bromide or ethyl (bromomethyl)acrylate [8]
occurs, furnishing the expected products 4 and 5a–b in
81–88% yield (Scheme 2). Having demonstrated that
the aminated Grignard reagent can be readily prepared
and allylated, we then investigated the transmetalation
of the intermediate arylmagnesium compounds to the
corresponding organozinc reagents for use in palla-
dium(0) catalyzed cross-coupling with various aryl and
heteroaryl iodides [9]. Preliminary results indicate that
the iododiimine 2 is the better suited for the perfor-
mance of Negishi cross-coupling reactions [9]. The best
source of palladium(0) was found to be bis(dibenzylide-
neacetone)palladium(0) (Pd(dba)2) [10]. Tris-o-furyl
phosphine (tfp) [11] proved to be an excellent ligand for
these cross-coupling reactions [12]. Most cross-coupling
reactions were complete within 16 h at r.t. affording the
expected products of type 6 in 52–79% yield (Scheme 3
and Table 1).
2. Results and discussion
2-Iodo-1,4-phenylenediamine (1) is readily prepared
in two steps from 4-nitroaniline by an iodination (I2,
AgSO4, EtOH, r.t., 1 h; 95% yield) [4] followed by a
reduction with SnCl2·2H2O in concentrated HCl
(50 °C, 12 h; 68% yield) [5]. Compound 1 can be
converted into the corresponding diimine 2 by treat-
ment with benzaldehyde in toluene in the presence of a
catalytic amount of conc. H2SO4 and molecular sieves
* Corresponding author. Tel.: +49-89-2180-7681; fax: +49-89-
2180-7680.
E-mail address: paul.knochel@cup.uni-muenchen.de (P. Knochel).
Various m- or p-substituted aryl iodides rapidly un-
dergo the expected cross-coupling reaction leading to
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(02)01156-7

A.E. Jensen, P. Knochel / Journal of Organometallic Chemistry 653 (2002) 122–128
123
Table 1
the products 6a–f in satisfactory yield (entries 1–6 of
Table 1). Interestingly, the sterically more hindered
o-methoxyiodobenzene reacts well, leading to 6g in 74%
yield (entry 7). Heterocyclic bromides such as 5-bromo-
2-carbethoxyfuran undergo the coupling reaction, fur-
nishing the heterocycle 6h in 52% yield (entry 8). The
resulting protected diamines 4 and 6 can be converted
to the free diamines by a rapid treatment with concen-
trated sulfuric acid in methanol (r.t., 0.5 min) [13],
leading to products 9 and 10 in 93–95% yield (Scheme
4).
2-Arylated-1,4-phenylenediamines prepared by Pd(0) catalyzed cross-
coupling between protected 2-zincated-1,4-phenylenediamine and
aryliodides
3. Conclusion
In summary, we have shown that 2-magnesiated-1,4-
phenylenediamine derivatives can be transmetalated to
the corresponding zinc reagents, which undergo a
smooth cross-coupling reaction with various aryl io-
Scheme 1.
a
Isolated yield of analytically pure products.
dides, leading to polyfunctional 1,4-diamines. Efforts to
convert several of these products to polyfunctional
heterocycles are currently underway in our laboratory.
Scheme 2.
4. Experimental
4.1. General considerations
All reactions were carried out under an argon atmo-
sphere. THF was distilled from sodium–benzophenone.
Zinc bromide was freshly dried before use for 2 h at
150 °C and less than 0.1 mmHg. Reactions were moni-
Scheme 3.

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A.E. Jensen, P. Knochel / Journal of Organometallic Chemistry 653 (2002) 122–128
tored by gas chromatography (GC) analysis of reaction
aliquots. Analytical thin-layer chromatography (TLC)
was performed using Merck silica gel (60 F-254) plates
(0.25 mm) precoated with a fluorescent indicator.
Column chromatography was carried out on silica gel
60 (43–60 mesh). 1,4-Phenylenediamine derivatives
were purified by solid phase extraction on Varian Bond
Elut tubes. The bonded silica sorbent was modified
with benzenesulfonic acid for strong cationic exchange
(SCX). NMR spectra were recorded on a 300 MHz
NMR spectrometer. The ionization method used was
electron impact ionization (EI, 70 eV). Elemental analy-
ses were performed by the Microanalytical Service Lab-
oratory of Universita¨t Mu¨nchen.
before slowly adding a solution of SnCl2·2H2O (25.0 g,
125 mmol) in concentrated HCl (40 ml). The reaction
was left for 3 h at this temperature before being cooled
to 0 °C on an ice bath and basified with a 50% NaOH
solution. The precipitate was filtered and dried in a
dessicator, then extracted several times with hot
dichloromethane. After concentration, recrystallization
from dichloromethane produced the product as yellow
crystals. Yield (4.7 g, 68%).
M.p.: 112 °C. IR (KBr, cm−1): w 3395 (m), 3284 (m),
1
3183 (m), 1607 (m), 1492 (s). H-NMR (CDCl3, 200
MHz): l 8.55 (d, J=2.4 Hz, 1H), 8.04 (dd, J=2.4 and
8.8 Hz, 1H), 6.70 (d, J=8.8 Hz, 1H). 13C-NMR
(CDCl3, 75 MHz): l 141.8, 141.4, 127.5, 119.5, 117.9,
86.5. MS (EI, 70 eV): 234 (100), 107 (33), 80 (18), 53
(10). Anal. Calc. for C6H7N2I: C, 30.79; H, 3.02; N,
11.97. Found: C, 30.86; H, 2.97; N, 11.85%.
4.2. Preparation of 2-iodo-4-nitroaniline
4-Nitroaniline (13.8 g, 100 mmol) was added to a
mixture of iodine (25.4 g, 100 mmol) and silver sulfate
(31.1 g, 100 mmol) in ethanol (250 ml) and left stirring
for 30 min at r.t. The solution was filtered and concen-
trated in vacuo. The residue was taken up in
dichloromethane, and washed with 5% NaOH solution,
and water, then dried over MgSO4 and concentrated.
The product was found to be of satisfactory purity, and
was obtained as a yellow powder. Yield (25.3 g, 95%).
M.p.: 107 °C. IR (KBr, cm−1): w 3480 (m), 3373 (s),
4.4. Preparation of 2-iodo-N1,N4-di[(E)-
phenylmethylidene]-benzene-1,4-diamine (2)
2-Iodo-p-phenylenediamine (3.5 g, 15 mmol) was dis-
solved in dry toluene (15 ml), then benzaldehyde (3.8 g,
36 mmol), H2SO4 (conc., a few drops) and molecular
,
sieves (4 A, 400 mg) were added and the mixture heated
to reflux for 2 h. The solution was filtered and concen-
trated in vacuo, the obtained yellow oil crystallized
upon addition of diethyl ether. Recrystallization from
ether yielded the product as yellow needles. Yield (4.9
g, 79%).
1
1609 (s), 1581 (m), 1491 (s), 1303 (s). H-NMR (CDCl3,
200 MHz): l 8.48 (d, J=2.4 Hz, 1H), 7.99 (dd, J=2.4
and 9.2 Hz, 1H) 6.77 (d, J=9.2 Hz, 1H). 13C-NMR
(CDCl3, 75 MHz): l 152.9, 139.5, 135.9, 126.1, 112.6,
80.9. MS (EI, 70 eV): 264 (100), 234 (47), 218 (13), 91
(56). Anal. Calc. for C6H5N2I: C, 27.29; H, 1.90; N,
10.61. Found: C, 27.08; H, 1.61; N, 10.48%.
M.p.: 118 °C. IR (KBr, cm−1): w 3436 (w), 1622 (s),
1
1577 (m), 1469 (m). H-NMR (CDCl3, 300 MHz): l
8.36 (s, 1H), 8.24 (s, 1H), 7.90–7.79 (m, 4H), 7.70 (d,
J=2.1 Hz, 1H), 7.41–7.36 (m, 6H), 7.17 (dd, J=2.1
and 8.4 Hz, 1H), 6.94 (d, J=8.4 Hz, 1H). 13C-NMR
(CDCl3, 75 MHz): l 160.8, 160.7, 151.9, 136.4, 136.3,
132.1, 131.4, 129.5, 129.3, 129.2, 123.0, 118.8, 96.4. MS
(EI, 70 eV): 410 (100), 281 (10), 178 (18), 152 (16).
Anal. Calc. for C20H15N2I: C, 58.55; H, 3.69; N, 6.83.
Found: C, 58.54; H, 3.67; N, 6.75%.
4.3. Preparation of 2-iodo-p-phenylenediamine (1)
2-Iodo-4-nitroaniline (8.0 g, 30 mmol) was suspended
in concentrated HCl (40 ml) and warmed to 50 °C
4.5. Preparation of N1,N1,N4,N4-tetraallyl-1-
iodobenzene-1,4-diamine (3)
2-Iodo-p-phenylenediamine (2.6 g, 11 mmol) was dis-
solved in dry dimethylformamide (100 ml). Allyl bro-
mide (16 ml, 185 mmol) and Na2CO3 (9.3 g, 87 mmol)
were added and the mixture heated to 100 °C for 3 h.
The solution was filtered after cooling to r.t., the filter
cake was washed with diethyl ether and the combined
organic phases poured into water (200 ml). The water
was extracted three times with diethyl ether (3×100
ml), the combined organic layers were dried over
MgSO4 and concentrated in vacuo. The obtained oil
was purified by bulb-to-bulb distillation (10−2 mbar,
200 °C) to give the product as an orange oil. Yield (3.2
g, 74%).
Scheme 4.

A.E. Jensen, P. Knochel / Journal of Organometallic Chemistry 653 (2002) 122–128
125
IR (KBr, cm−1): w 3077 (w), 2979 (w), 2810 (w), 1596
(s), 1496 (s), 1229 (m), 919 (m). H-NMR (CDCl3, 300
MHz): l 6.86 (d, J=6.0 Hz, 1H), 6.48–6.43 (m, 2H),
5.79–5.71 (m, 5H), 5.13–4.95 (m, 10H), 3.80–3.77 (m,
5H), 3.40–3.38 (m, 5H). 13C-NMR (CDCl3, 75 MHz):
l 144.6, 138.7, 137.3, 136.4, 135.0, 133.6, 122.8, 115.6,
115.1, 114.1, 113.0, 109.7, 56.3, 52.0, 34.3. MS (EI, 70
eV): 308 (88), 267 (64), 226 (100), 185 (48), 170 (50),
157 (42), 143 (26), 130 (30). Anal. Calc. for C21H28N2:
C, 81.77; H, 9.15; N, 9.08. Found: C, 81.78; H, 9.19; N,
8.96%.
1
MHz): l 7.09 (d, J=3.0 Hz, 1H), 6.77 (d, J=8.7 Hz,
1H), 6.54 (dd, J=3.0 and 8.7 Hz, 1H), 5.73 (m, 4H),
5.04 (m, 8H), 3.76 (m, 4H), 3.42 (m, 4H). 13C-NMR
(CDCl3, 75 MHz): l 147.1, 141.4, 135.9, 134.1, 124.6,
123.1, 117.6, 116.8, 113.1, 103.1, 57.4, 53.3. MS (EI, 70
eV): 394 (100), 353 (81), 225 (39), 183 (24), 157 (27),
130 (30). Anal. Calc. for C18H23N2I: C, 54.83; H, 5.88;
N, 7.10. Found: C, 54.36; H, 6.24; N, 7.10%.
4.6.2. 2-Allyl-N1,N4-di[(E)-phenylmethylidene]-
benzene-1,4-diamine (4)
4.6. General procedure for the preparation of
compounds of type 4 and 5. Preparation of ethyl
2-[2,5-bis(diallylamino)benzyl]acrylate (5b)
From 2 (1.23 g, 3 mmol) and allyl bromide (1.08 g, 9
mmol). Purification by flash chromatography (pen-
tane–ether–TEA 20:1:5) yielded 4 as a yellow powder
(812 mg, 83%).
A dry and argon flushed 10 ml Schlenk-flask,
equipped with a magnetic stirrer, was charged with 3
(394 mg, 1 mmol) in dry THF (1 ml) and cooled to
−10 °C. iPrMgBr (3.3 ml, 0.6 M in THF, 2 mmol)
was added slowly. After 1 h the exchange was complete
(checked by TLC analysis) and CuCN·2LiCl (1.0 ml, 1
M in THF, 1 mmol) was added slowly. After 30 min
ethyl 2-(bromomethyl)acrylate (576 mg, 3 mmol) was
added and the reaction mixture allowed to warm to r.t.
overnight. The reaction was quenched with NH4Cl–
NH3 9:1 (3 ml), poured into water (20 ml) and ex-
tracted with ether (3×40 ml). The combined organic
fractions were washed with brine (100 ml), then dried
over Na2SO4 and concentrated in vacuo. The crude
product was purified by flash chromatography (pen-
tane–EtOAc 95:5) to yield 5b as a pale yellow oil (309
mg, 81%).
M.p.: 57 °C. IR (KBr, cm−1): w 3059 (w), 2874 (w),
1
1623 (s), 1576 (m), 756 (s), 691 (s). H-NMR (CDCl3,
300 MHz): l 8.44 (s, 1H), 8.35 (s, 1H), 7.86–7.82 (m,
4H), 7.43–7.39 (m, 6H), 7.09 (s, 1H), 7.01 (d, J=6.9
Hz, 2H). 13C-NMR (CDCl3, 75 MHz): l 159.8, 159.4,
150.3, 148.9, 137.6, 136.9, 136.7, 135.7, 131.6, 129.2,
122.6, 120.1, 118.8, 116.1, 18.1. MS (EI, 70 eV): 324
(44), 323 (100), 220 (16), 115 (18). Anal. Calc. for
C23H20N2: C, 85.15; H, 6.21; N, 8.63. Found: C, 84.75;
H, 6.38; N, 8.52%.
4.7. General procedure for the preparation of
compounds of type 6: preparation of ethyl 2%,5%-
bis{[(E)-phenylmethylidene]amino}[1,1%-biphenyl]-4-
carboxylate (6a)
IR (KBr, cm−1): w 3078 (w), 2980 (m), 1717 (s), 1607
A dry and argon flushed 10 ml Schlenk-flask,
equipped with a magnetic stirrer, was charged with 2
(410 mg, 1 mmol) in dry THF (1 ml) and cooled to
−10 °C. iPrMgBr (3.3 ml, 0.6 M in THF, 2 mmol)
was added slowly. After 1 h the exchange was complete
(checked by TLC analysis) and ZnBr2 (0.8 ml, 1.5 M in
THF, 1.1 mmol) was added. The reaction was allowed
to warm to r.t.. Another dry and argon flushed 10 ml
Schlenk-flask, equipped with a magnetic stirrer, was
charged with Pd(dba)2 (29 mg, 0.05 mmol) and tfp (23
mg, 0.10 mmol) in dry THF (1 ml). After formation of
the active catalyst ethyl 4-iodobenzoate (191 mg, 0.7
mmol) was added followed by the zinc reagent. The
reaction mixture was stirred at r.t. for 16 h, then
quenched with NH4Cl (2 ml), poured into water (50 ml)
and extracted with ether (3×40 ml). The combined
organic fractions were washed with brine (70 ml), then
dried over Na2SO4 and concentrated in vacuo. The
crude product was purified by flash chromatography
(pentane–ether–TEA 20:1:2) to yield 6a as a pale yel-
low oil (868 mg, 81%).
1
(m), 1508 (s). H-NMR (CDCl3, 300 MHz): l 6.88 (d,
J=8.7 Hz, 1H), 6.48 (dd, J=3.3 and 8.7 Hz, 1H), 6.40
(d, J=3.3 Hz, 1H), 6.12 (s, 1H), 5.77–5.71 (m, 4H),
5.24 (s, 1H), 5.11–4.94 (m, 8H), 4.13(q, J=7.2 Hz,
2H), 3.77 (d, J=6 Hz, 4H), 3.64 (s, 2H), 3.36 (d, J=6
Hz, 4H), 1.20 (t, J=7.2 Hz, 3H). 13C-NMR (CDCl3, 75
MHz): l 167.9, 145.9, 141.3, 140.2, 136.7, 136.4, 134.8,
126.9, 125.8, 124.5, 117.0, 116.5, 114.8, 111.4, 60.6,
57.7, 53.4, 33.4, 14.6. MS (EI, 70 eV): 380 (100), 339
(30), 297 (17), 265 (18). Anal. Calc. for C24H32N2O2: C,
75.75; H, 8.48; N, 7.36. Found: C, 75.94; H, 7.98; N,
6.98%.
The products 4 and 5a were prepared according to
this method.
4.6.1. N1,N1,N4,N4,2-pentaallyl-1-iodobenzene-
1,4-diamine (5a)
From 3 (394 mg, 1 mmol) and allyl bromide (360 mg,
3 mmol). Purification by flash chromatography (pen-
tane–EtOAc 95:5) yielded 5a as a colorless oil (270 mg,
88%).
IR (KBr, cm−1): w 3430 (br), 1712 (w), 1622 (s), 1576
IR (KBr, cm−1): w 3077 (w), 2978 (w), 1639 (W9,
1607 (m), 1507 (s), 917 (s). 1H-NMR (CDCl3, 300
(m), 755 (m), 691 (s). H-NMR (CDCl3, 300 MHz): l
1
8.33 (s, 1H), 8.21 (s, 1H), 7.88–7.84 (m, 2H), 7.80–7.76

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A.E. Jensen, P. Knochel / Journal of Organometallic Chemistry 653 (2002) 122–128
(m, 2H), 7.68 (d, J=2.1 Hz, 1H), 7.38–7.22 (m, 1H),
7.15 (dd, J=2.1 and 8.4 Hz, 1H), 6.92 (d, J=8.4 Hz,
1H), 2.43 (q, J=7.2 Hz, 2H), 0.93 (t, J=7.3 Hz, 3H).
13C-NMR (CDCl3, 75 MHz): l 189.3, 160.8, 160.7,
151.8, 136.3, 132.0, 130.9, 130.0, 129.5, 129.3, 127.9,
127.4, 123.0, 118.8, 46.7, 11.9. MS (EI, 70 eV): 432
(100), 355 (48), 327 (47), 281 (13), 254 (22), 77 (9).
HRMS: Calc. for C29H24N2O2: 432.1838. Found:
432.1851%.
7.03 (d, J=8.4 Hz, 1H). 13C-NMR (CDCl3, 75 MHz):
l 160.1, 150.4, 147.8, 138.2, 136.8, 136.7, 135.8, 133.5,
132.0, 129.3, 129.0, 123.2, 122.3, 121.6, 120.0. MS (EI,
70 eV): 394 (21), 317 (25), 207 (100), 191 (9), 133 (8).
Anal. Calc. for C26H19N2Cl: C, 79.08; H, 4.85; N, 7.09.
Found: C, 78.90; H, 5.19; N, 6.94%.
4.7.4. 4%-Methoxy-N2,N2-bis[(E)-phenylmethylidene]-
[1,1%-biphenyl]2,5-diamine (6e)
The products 6b–h were prepared according to this
method.
From 2 (410 mg, 1 mmol) and 4-iodoanisol (164 mg,
0.7 mmol). Purification by flash chromatography (pen-
tane–ether–TEA 20:1:2) yielded 6e as a yellow oil (215
mg, 79%).
4.7.1. 2%,5%-Bis{[(E)-phenylmethylidene]amino}[1,1%-
biphenyl]-4-carbonitrile (6b)
From 2 (410 mg, 1 mmol) and 4-iodobenzonitrile
(160 mg, 0.7 mmol). Purification by flash chromatogra-
phy (pentane–ether–TEA 20:1:2) yielded 6b as a yellow
oil (162 mg, 60%).
IR (KBr, cm−1): w 3430 (br), 3058 (w), 2957 (w),
1624 (s), 1578 (m), 1493 (m), 1451 (m), 1250 (m), 754
1
(s), 692 (s). H-NMR (CDCl3, 300 MHz): l 8.44 (s,
1H), 8.29 (s, 1H), 7.81–7.79 (m, 2H), 7.60–7.57 (m,
2H), 7.36–6.75 (m, 13H), 3.51 (s, 3H). 13C-NMR
(CDCl3, 75 MHz): l 160.1, 160.0, 132.0, 131.7, 129.3,
129.2, 129.0, 128.9, 128.7, 123.8, 122.3, 121.8, 120.7,
119.7, 111.1, 55.9. MS (EI, 70 eV): 390 (100), 359 (71),
284 (77), 181 (36), 139 (24). HRMS Calc. for
C27H22N2O: 390.1732. Found: 390.1718%.
IR (KBr, cm−1): w 3407 (m), 2960 (m), 2225 (m),
1618 (s), 1603 (s), 1495 (s). 1H-NMR (CDCl3, 300
MHz): l 8.35 (s, 1H), 8.31 (s, 1H), 7.63–7.61 (m, 2H),
7.54 (d, J=9 Hz, 2H), 7.41 (d, J=9 Hz, 2H), 7.33–
7.24 (m, 6H), 7.18–7.16 (m, 5H). 13C-NMR (CDCl3, 75
MHz): l 155.4, 145.5, 144.0, 141.1, 137.9, 135.8, 134.8,
130.1, 129.9, 127.7, 126.9, 126.2, 118.0, 113.1, 109.1.
MS (EI, 70 eV): 386 (83), 296 (9), 154 (17), 133 (30), 91
(100). HRMS Calc. for C27H19N3: 385.1579. Found:
385.1568%.
4.7.5. Ethyl 2%,5%-bis{[(E)-phenylmethylidene]amino}-
[1,1%-biphenyl]-3-carboxylate (6f)
From 2 (410 mg, 1 mmol) and ethyl 4-iodobenzoate
(191 mg, 0.7 mmol). Purification by flash chromatogra-
phy (pentane–ether–TEA 20:1:2) yielded 6f as a yellow
oil (188 mg, 62%).
4.7.2. 4%-Methyl-N2,N2-bis[(E)-phenylmethylidene]-
[1,1%-biphenyl]2,5-diamine (6c)
From 2 (410 mg, 1 mmol) and 4-iodo-1-methylben-
zene (153 mg, 0.7 mmol). Purification by flash chro-
matography (pentane–ether–TEA 20:1:2) yielded 6c as
a yellow oil (188 mg, 71%).
IR (KBr, cm−1): w 3414 (br), 3060 (w), 2870 (w),
1714 (s), 1623 (s), 1578 (m), 1365 (s), 1270 (s), 692 (s).
1H-NMR (CDCl3, 300 MHz): l 8.46 (s, 1H), 8.40 (s,
1H), 8.21 (s, 1H), 7.92 (d, J=7.8 Hz, 1H), 7.84–7.67
(m, 5H), 7.38–7.30 (m, 8H), 7.20 (dd, J=2.1 and 8.1
Hz, 1H), 7.06 (d, J=8.1 Hz, 1H), 4.23 (q, J=7.1 Hz,
2H), 1.19 (t, J=7.1 Hz, 3H). 13C-NMR (CDCl3, 75
MHz): l 167.1, 160.4, 150.5, 147.9, 139.8, 136.8, 136.6,
136.0, 135.1, 131.9, 131.7, 130.9, 129.2, 128.7, 128.6,
127.3, 121.8, 61.3, 14.7. MS (EI, 70 eV): 432 (15), 147
(13), 197 (13), 133 (17), 123 (24), 109 (43), 95 (70), 83
(58), 55 (100). HRMS Calc. for C29H24N2O2: 432.1838.
Found: 432.1847%.
IR (KBr, cm−1): w 3419 (br), 3026 (w), 2960 (s), 1594
(m), 1495 (s), 1451 (m). 1H-NMR (CDCl3, 300 MHz): l
8.32 (s, 1H), 8.30 (s, 1H), 7.64–7.63 (m, 2H), 7.35–7.04
(m, 12H), 6.86 (d, J=8.4 Hz, 1H), 6.56 (d, J=2.7 Hz,
1H), 6.40 (dd, J=2.7 and 8.4 Hz, 1H), 2.28 (s, 1H).
13C-NMR (CDCl3, 75 MHz): l 156.6, 130.5, 129.1,
128.9, 128.9, 128.7, 128.6, 127.7, 127.3, 121.3, 119.3,
115.6, 113.1, 35.3. MS (EI, 70 eV): 375 (45), 281 (11),
253 (8), 207 (100). HRMS Calc. for C27H22N2:
374.1783. Found: 374.1799%.
4.7.6. 2%-Methoxy-N2,N2-bis[(E)-phenylmethylidene]-
[1,1%-biphenyl]2,5-diamine (6g)
4.7.3. 4%-Chloro-N2,N2-bis[(E)-phenylmethylidene]-
[1,1%-biphenyl]2,5-diamine (6d)
From 2 (410 mg, 1 mmol) and 2-iodoanisol (164 mg,
0.7 mmol). Purification by flash chromatography (pen-
tane–ether–TEA 20:1:2) yielded 6g as a yellow oil (200
mg, 74%).
From 2 (410 mg, 1 mmol) and 1-chlor 4-iodobenzene
(167 mg, 0.7 mmol). Purification by flash chromatogra-
phy (pentane–ether–TEA 20:1:2) yielded 6d as a yellow
oil (170 mg, 62%).
IR (KBr, cm−1): w 3429 (br), 2957 (w), 1623 (s), 1600
1
(m), 1577 (m), 1492 (m), 1452 (m). H-NMR (CDCl3,
IR (KBr, cm−1): w 3436 (br), 2869 (w), 1619 (s), 1577
300 MHz): l 8.44 (s, 1H), 8.29 (s, 1H), 7.81–7.79 (m,
2H), 7.60–7.57 (m, 2H), 7.36–6.75 (m, 13H), 3.51 (s,
3H). 13C-NMR (CDCl3, 75 MHz): l 160.1, 160.0,
132.0, 131.7, 129.3, 129.2, 129.0, 128.9, 128.7, 123.8,
1
(m), 1494 (m), 1473 (m), 1450 (m), 688 (s). H-NMR
(CDCl3, 300 MHz): l 8.43 (s, 1H), 8.39 (s, 1H), 7.82–
7.80 (m, 2H), 7.70–7.67 (m, 2H), 7.39–7.12 (m, 12H),

A.E. Jensen, P. Knochel / Journal of Organometallic Chemistry 653 (2002) 122–128
127
122.3, 121.8, 120.7, 119.7, 111.1, 55.9. MS (EI, 70 eV):
390 (100), 359 (71), 284 (77), 181 (36), 139 (24). HRMS
Calc. for C27H22N2O: 390.1732. Found: 390.1748%.
IR (KBr, cm−1): w 3348 (br), 2981 (w), 1708 (s), 1608
(s), 1513 (m), 1498 (s), 1284 (s), 1103 (s). 1H-NMR
(CDCl3, 300 MHz): l 8.00 (dd, J=2.1 and 6.6 Hz, 2H),
7.43 (dd, J=2.1 and 6.6 Hz, 2H), 6.58–6.46 (m, 3H),
4.3 (q, J=7.2 Hz, 2H), 3.16 (br, 4H), 1.42 (t, J=7.2
Hz, 3H). 13C-NMR (CDCl3, 75 MHz): l 166.9, 144.9,
139.1, 130.3, 129.5, 128.2, 117.9, 117.3, 61.4, 14.7. MS
(EI, 70 eV): 256 (100), 228 (82), 211 (6), 183 (49), 154
(9), 91 (22). HRMS Calc. for C15H16N2O2: 256.1212.
Found: 256.1208%.
4.7.7. Ethyl 5-(2,5-bis{[(E)-phenylmethylidene]amino}-
phenyl-2-furoate (6h)
From 2 (410 mg, 1 mmol) and ethyl 5-iodo-2-furoate
(153 mg, 0.7 mmol). Purification by flash chromatogra-
phy (pentane–ether–TEA 20:1:2) yielded 6g as a yellow
oil (153 mg, 52%).
IR (KBr, cm−1): w 3421 (br), 1711 (s), 1624 (s), 1578
1
(m), 1495 (m), 1300 (s), 1208 (m), 1141 (m). H-NMR
4.9. General procedure for the deprotection of
N,N-diallylamine deri6ati6es: preparation of
2-allyl-1,4-phenylenediamine (9)
(CDCl3, 300 MHz): l 8.50 (s, 1H), 8.38 (s, 1H), 7.88–
7.84 (m, 4H), 7.45–7.39 (m, 6H), 7.19–7.13 (m, 3H),
6.96 (d, J=9 Hz, 1H), 4.30 (q, J=7.2 Hz, 2H), 1.29 (t,
J=7.2 Hz, 3H). 13C-NMR (CDCl3, 75 MHz): l 192.8,
160.8, 160.5, 155.1, 150.4, 147.6, 143.7, 136.5, 132.1,
131.9, 129.1, 129.0, 123.1, 119.6, 118.6, 114.1, 61.3,
14.8. MS (EI, 70 eV): 422 (12), 281 (13), 207 (100), 191
(11), 133 (8), 96 (9). HRMS Calc. for C27H22N2O3:
422.1630. Found: 422.1647%.
In a dry and argon flushed flask Pd(PPh3)4 (23 mg,
0.02 mmol) and N,N%-dimethylbarbituric acid (936 mg,
6 mmol) was mixed before adding N1,N1,N4,N4-tetraal-
lyl-1-allylbenzene-1,4-diamine (150 mg, 0.5 mmol) in
dry degassed dichloromethane (3 ml). The suspension
was warmed to 35 °C and left for 2 h. After cooling to
r.t. the dichloromethane was distilled off and the
residue taken up in diethyl ether, then washed with
NaHCO3 solution. The organic layer was dried over
MgSO4, concentrated and purified on a SCX column as
described above. Yield (63 mg, 85%).
4.8. General procedure for the deprotection of N-
phenylmethyleneamine deri6ati6es. Preparation of
2-allyl-1,4-phenylenediamine (9)
2-Allyl- N1,N4 -di[(E)-phenylmethylidene] -benzene-
1,4-diamine (324 mg, 1 mmol) was dissolved in
methanol (10 ml) and a few drops of a 2 M sulfuric acid
were added. The solution immediately became deep red,
then decolorized within 30 s. The solution was concen-
trated in vacuo. The product was purified by cation
exchange extraction on a Varian bond elute SCX
column. The SCX column was conditioned with 10%
acetic acid in methanol, then the product was applied
with methanol and the column washed with methanol
and acetonitrile. For the elution of the product 10%
ammonia in methanol was employed. The product was
obtained after concentration of the latter fractions.
Yield (140 mg, 95%).
Acknowledgements
We thank the Deutsche Forschungsgemeinschaft
(Leibniz program) for financial support. A.E.J. thanks
L’Ore´al (Aulnay/s/bois) for a fellowship. We thank
BASF AG, Degussa AG and Chemetall GmbH for
generous gifts of chemicals.
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