Tsuji-Trost allylations with palladium recovery by phosphines/Pd(0)-triolefinic macrocyclic catalysts

Article abstract of DOI:10.1016/j.jorganchem.2010.01.033

The allylation of several nitrogen and oxygen based nucleophiles with ethyl cinnamyl carbonate under mild conditions is described. The processes take place in the absence of added base and in the presence of the precatalytic system Pd(0)-triolefinic macrocycle/1,1′-bis(diphenylphosphino)ferrocene. The macrocyclic ligand plays a key role in the recovery of the metal in the form of the initial macrocyclic complex.

Full text of DOI:10.1016/j.jorganchem.2010.01.033

Journal of Organometallic Chemistry 695 (2010) 1231–1236
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Tsuji–Trost allylations with palladium recovery by phosphines/Pd(0)-triolefinic
macrocyclic catalysts
*
Anna Serra-Muns, Roser Pleixats
Chemistry Department, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, 08193-Barcelona, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
The allylation of several nitrogen and oxygen based nucleophiles with ethyl cinnamyl carbonate under
mild conditions is described. The processes take place in the absence of added base and in the presence
of the precatalytic system Pd(0)-triolefinic macrocycle/1,10-bis(diphenylphosphino)ferrocene. The mac-
rocyclic ligand plays a key role in the recovery of the metal in the form of the initial macrocyclic complex.
Ó 2010 Elsevier B.V. All rights reserved.
Received 17 December 2009
Received in revised form 22 January 2010
Accepted 25 January 2010
Available online 2 February 2010
Dedicated to Prof. Pelayo Camps Garcia on
the occasion of his 65th birthday
Keywords:
Allylation
Catalysis
Macrocyclic ligands
Olefin complex
Palladium
1. Introduction
allylation of ambident nucleophilic heterocycles [1j], frequently
providing higher regioselectivities than classical alkylation meth-
The palladium(0)-catalyzed allylation of nucleophiles (the
Tsuji–Trost reaction) is the displacement of a leaving group from
an allylic framework by a nucleophile under Pd(0) catalysis. It con-
stitutes a powerful method for C–C and C-heteroatom bond forma-
tion which has gained high recognition in organic synthesis due to
its versatility, broad scope and easy experimental procedure [1].
Although many leaving groups in the allyl system have been
reported in the literature for the in situ generation of cationic
ods. Extensive work on this subject has been reported by the group
of Moreno-Mañas [3]. The classical catalytic systems in Tsuji–Trost
reactions involve the use of palladium(0) (e.g., Pd(PPh3)4,
Pd2(dba)3) or palladium(II) (e.g., Pd(OAc)2) precursors and phos-
phine ligands to stabilize the intermediate cationic g
3-allyl com-
plex, these ligands being either present in the precursor complex
or added externally.
Some years ago in the group of Moreno-Mañas we serendipi-
tously discovered [2c] air- and moisture-stable phosphine-free
azamacrocyclic triolefinic palladium(0) complexes of the type
Pd-1 (Scheme 1). The preparation [4,5] of the required 15-mem-
bered triolefinic macrocycles 1, their coordination properties
[5,6] with transition metals, and the activity of Pd-1 as recyclable
catalysts [5,7] has been reported. Thus, complexes Pd-1 were ac-
tive in Suzuki cross-couplings with activated aryl iodides [7a].
Polymeric versions (polystyrene-grafted catalyst [7a] and macro-
cycle-based polypyrrole-modified electrodes [7e]) were efficiently
recovered and reused. Activated and deactivated aryl iodides were
good substrates for Suzuki couplings under catalysis by recyclable
silica hybrid materials containing macrocyclic complexes cova-
lently anchored [7d,f,g]. Although these results were promising,
the activity in Suzuki couplings was limited to aromatic iodides.
The cross-coupling between arenediazonium salts and potassium
organotrifluoroborates [7h], the Mizoroki-Heck reactions with
arenediazonium tetrafluoroborates as electrophilic partners [7c],
g
3-allylic palladium complexes, the acetoxy and the alcoxycarbon-
yloxy groups have remained the most popular since the corre-
sponding acetates and mixed carbonates are very reactive and
easily available. Allylic carbonates offer advantages over acetates
as addition of external base is not required for pronucleophiles
which are more acidic than alcohols in the reaction medium. The
alcoxide anion formed in situ as counter-anion of the electrophilic
g
3-allyl palladium intermediate generates the conjugate base of
the pronucleophile and the allylation takes place formally in neu-
tral medium. Therefore, they have been the most extensively used
substrates for this kind of reaction since 1982 [1k]. We have de-
scribed the palladium(0)-catalyzed allylation of several highly
acidic and non nucleophilic compounds using allylic carbonates
[2]. The Tsuji–Trost reaction has also been broadly applied to the
* Corresponding author. Tel.: +34 93 581 2067; fax: +34 93 581 1265.
E-mail address: roser.pleixats@uab.cat (R. Pleixats).
0022-328X/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.01.033

1232
A. Serra-Muns, R. Pleixats / Journal of Organometallic Chemistry 695 (2010) 1231–1236
Scheme 1. Triolefinic azamacrocycles 1 and the corresponding Pd(0) complexes Pd-1. The role of 1 and Pd-1 in a catalytic cycle in the presence of phosphine ligands.
and the hydroarylation of alkynes in ionic liquids [7b] catalyzed by
these macrocyclic complexes have also been described. On the
other hand, complexes Pd-1 were not active in telomerisation of
butadiene in the presence of methanol. However, upon addition
of phosphines, the reaction took place and the catalytic species
could be recycled up to four times by addition of fresh phosphine
at each time [8]. Subsequent studies showed that Pd-1 complexes
reacted with monodentate or bidentate phosphines to furnish PdLn
complexes [9]. After catalysis came to an end, if the phosphine was
oxidized, palladium(0) reverted to the free macrocycle ligand, thus
preventing agglomeration and precipitation of palladium black and
remaining available for a new run, which required addition of fresh
phosphine but not fresh palladium (Scheme 1). Later on, we per-
formed successful Suzuki cross-couplings on aryl and heteroaryl
bromides and chlorides by using a catalytic system that was a com-
for one day and then dried by distillation from sodium-benzophe-
none ketyl just before use. 1H NMR spectra (250 or 360 MHz) and
13C NMR (62.5 or 90 MHz) were usually recorded on a Bruker DPX-
250 or on a Bruker DPX-360. Chemical shifts (d, ppm) are
referenced to Me4Si (1H and 13C). The abbreviations used are s
for singlet, d for doublet, dd for double doublet, t for triplet, q for
quartet, dt for double triplet, and m for multiplet. IR data were ob-
tained on a Bruker Tensor 27 spectrophotometer with ATR Golden
Gate. Mass spectra (MS-ESI and HRMS-ESI) were recorded at the
Servei d’Anàlisi de la Universitat Autònoma de Barcelona using
an Esquire 3000 quadrupole instrument and a MicroTOFQ Bruker
Daltonic operating in the positive ion mode (ES+) at a probe tip
voltage of 3 kV. Elemental analyses were performed at the Servei
d’Anàlisi de la Universitat Autònoma de Barcelona. Macrocycle 1
and its palladium(0) complex Pd-1 were prepared as previously re-
ported [7a].
bination of a bulky aliphatic
r-donor phosphine with a macrocy-
clic complex of type Pd-1 [10]. The addition of highly
nucleophilic and sterically demanding phosphines allowed activa-
tion of the more challenging bromides and chlorides [11], and the
macrocycle 1 allowed the recovery of the metal in the form of the
initial macrocyclic complex. Subsequent kinetic and mechanistic
studies were undertaken in collaboration with Jutand on the first
step of this Suzuki process, that is, the oxidative addition of aryl
halides to the PdLn complexes generated in situ from a Pd(0)-trio-
lefinic macrocyclic complex and phosphines [12]. This investiga-
tion emphasized the key role played by the unsaturated
macrocyclic ligands 1 on the kinetics of the oxidative addition.
With all these precedents in mind, we decided to test the palla-
dium(0)-catalyzed allylation using a catalytic precursor system
consisting of a mixture of complex Pd-1 and a phosphine, with
the aim to achieve the recovery of the metal in the form of the mac-
rocyclic complex. Preliminary experiments [9] performed in the
NMR tube revealed that, as in the telomerisation processes previ-
ously mentioned, the presence of a phosphine ligand was required
to achieve the allylation reaction. The disappearance of Pd-1 com-
plexes upon addition of phosphines, with concomitant appearance
of free macrocycle 1 and PdLn species, was observed by NMR. These
in situ formed PdLn intermediates would react with the allylic sub-
2.2. Preparation of allylation products
2.2.1. General procedure: Preparation of N-cinnamyl-N-methylaniline,
4a
Ethyl cinnamyl carbonate 2 (58 mg, 0.281 mmol), Pd-1 (25 mg,
0.022 mmol) and dppf (15.7 mg, 0.028 mmol) were added into a
Schlenk flask. Three vacuum/argon cycles were made. N-methylan-
iline 3a (31 lL, 0.989 g/mL, 0.281 mmol) and anhydrous and de-
gassed THF (3 mL) were added. The mixture was magnetically
stirred at room temperature under argon for 22 h. The solvent
was evaporated and the residue was purified by flash-chromatog-
raphy (silica gel) with hexane-ethyl acetate 97:3, to afford 4a [13]
as an oil (53 mg, 86% yield); 1H NMR (CDCl3) d = 2.97 (s, 3H), 4.07
(d, J = 5.5 Hz, 2H), 6.23 (dt, J = 15.7 and 5.4 Hz, 1H), 6.51 (d,
J = 15.7 Hz, 1H), 6.75 (m, 3H), 7.22 (m, 7H); 13C NMR (CDCl3)
d = 38.1, 55.0, 112.8, 116.7, 125.9, 126.5, 127.5, 128.7, 129.3,
131.4, 137.1, 149.7. Then, a mixture Pd-1:1 97:3 (15 mg, 94%
recovery) was eluted.
2.2.2. Preparation of allylation products 4b–k
The other compounds 4 were prepared in a similar manner (see
Table 2 for differences in experimental conditions).
strates to form the cationic g
3-allyl palladium complexes. Now, we
present herein the results of the reactions of ethyl cinnamyl carbon-
ate with several nitrogen and oxygen-based nucleophiles.
2.2.2.1. N-cinnamyl-N-methyl-4-chloroaniline, 4b. Eluent: hexane–
2. Experimental
ethyl acetate 97:3–90:10; IR (ATR):
m
= 3026, 1596, 1499, 1448,
1355, 1199, 1116, 964, 808 cmꢀ1
;
1H NMR (CDCl3) d = 2.96 (s,
2.1. General remarks
3H), 4.04 (d, J = 5.2 Hz, 2H), 6.19 (dt, J = 15.7 and 5.4 Hz, 1H), 6.48
(d, J = 15.7 Hz, 1H), 6.67 (d, J = 9.0 Hz, 2H), 7.16 (d, J = 9.0 Hz, 2H),
7.31 (m, 5H); Anal. Calc. for C16H16NCl: C, 74.55; H, 6.26; N, 5.43.
Found: C, 73.98; H, 6.33; N, 5.09%.
Experiments were carried out with standard high-vacuum and
Schlenk techniques. THF was stored over potassium hydroxide

A. Serra-Muns, R. Pleixats / Journal of Organometallic Chemistry 695 (2010) 1231–1236
1233
Table 1
Optimization of Tsuji–Trost reaction between ethyl cinnamyl carbonate, 2, and N-methylaniline, 3a.
Entrya
L
Equivalents (L)b
Time (h)
Conversion (%)c
Yield 4a (%)d
Pd-1:1e
f
1
2
3
4
5
6
PCy3
2.0
2.3
2.0
2.0
2.0
1.3
15
24
24
20
3
70
60
100
100
100
100
70
55
89
72
69
86
0:100
0:100
87:13
97:3
85:15
97:3
dppb
PPh3
PPh2(o-tolyl)
dppe
dppf
22
a
b
c
d
e
f
[2] = 0.09–0.10 M, 2:3a = 1:1, 5% molar of Pd-1, anhydrous and degassed THF, argon atmosphere, room temperature.
Equivalents of L with respect to Pd-1.
Conversion determined by 1H NMR.
Isolated yields of 4a by chromatography.
Ratio Pd-1:1 determined by 1H NMR in the recovered mixture separated from 4a by chromatography.
Commercial solution of PCy3 in toluene (20% w/w) was used.
Table 2
Tsuji–Trost reactions between ethyl cinnamyl carbonate 2 and N- and O-nucleophiles 3 to give allylation products 4.
Entrya
1
T
Time (h)
15
Carbonate [2]
Nucleophile
3
2:3
1:1
Product
4
Yield (%)b
70
Pd-1:1c
r.t.
0.09
3b
4b
86:14
Me
HN
Cl
Cl
Ph
N
Me
2
3
r.t.
r.t.
15
20
0.08
0.09
3c
1:1
1:1
4c
21d,e
81:19
50:50
NO2
NO2
H2N
Ph
Ph
N
H
3d
4d
90f
HN(C6H13 2
)
C6H13
N
C6H13
4
5
r.t.
r.t.
20
20
0.08
0.09
3e
3f
1:1
1:1
4e
73f,g
19:81
0:100
H2NC12H25
Ph
N
Ph
N
C12H25
4f 4’f
33
58
N
N
N
H
N
Ph
N
N
N
N
Ph
6
r.t.
14
0.25
3g
5:1
4g
49
0:100
O2
Ph
Ph
Ph
Ph
O2
N S N
H2N S NH2
7
8
refl.
refl.
21
21
0.10
0.11
3h
3i
1:0.9
1:0.9
4h
4i
100
29d
92:8
HO
Ph
Ph
Ph
O
O2N
56:44
O2N
HO
O
O
9
refl.
r.t.
21
15
0.11
0.13
3j
1:0.9
1:0.9
4j
58d
78
55:45
88:12
NO2
NO2
HO
HO
10
3k
4k
Ph
O
a
b
c
d
e
f
5% molar of Pd-1, 5% molar of dppf, anhydrous and degassed THF, argon atmosphere.
Isolated yields of 4 by chromatography.
Ratio Pd-1:1 determined by 1H NMR in the recovered mixture separated from 4 by chromatography.
Other secondary products are obtained (see text).
23% conversion of 3c.
Yield determined by 1H NMR integration on the eluted fraction by chromatography.
Yield based on 2.
g

1234
A. Serra-Muns, R. Pleixats / Journal of Organometallic Chemistry 695 (2010) 1231–1236
2.2.2.2. N-cinnamyl-4-nitroaniline, 4c [2a,14]. Eluent: hexane–ethyl
acetate 80:20–70:30; 1H NMR (CDCl3) d = 4.04 (dd, J = 5.7 and
1.5 Hz, 2H), 4.68 (br s, 1H), 6.26 (dt, J = 16.0 and 5.7 Hz, 1H), 6.60
(m, 3H), 7.31 (m, 5H), 8.10 (d, J = 9.2 Hz, 2H).
3. Results and discussion
We initially studied the reaction between ethyl cinnamyl car-
bonate, 2, and N-methylaniline, 3a, in the presence of a 5% molar
of Pd-1 (see Scheme 1, Ar = 2, 4, 6-triisopropylphenyl) and several
phosphine ligands (aromatic and aliphatic monodentate phos-
phines; bidentate phosphines) (Table 1). In all cases the reactions
were performed under inert atmosphere, with equimolar amounts
of reagents, in anhydrous and degassed tetrahydrofuran at room
temperature. Treatment of the crude mixtures by column chroma-
tography through silica gel permitted the obtention of moderate to
good yields of N-cinnamyl-N-methylaniline, 4a, and also the recov-
ery of a mixture of palladium(0) complex Pd-1 and the free macro-
cycle 1 in the molar ratios mentioned in Table 1. The recovery of
macrocycle was nearly quantitative in all cases (if we consider
the sum of its free and metal coordinated forms). 1H NMR spectra
distinguish very well free macrocycles from their palladium(0)
complexes since free macrocycles present signals for the olefinic
protons at d ca. 5.50–5.80, whereas in palladium complexes strong
upfield shifts are observed, up to d ca. 2.50–4.40 depending of the
proton considered [2c,5]. When the aliphatic and bulky monoden-
tate tricyclohexylphosphine (Table 1, entry 1) and the bidentate
1,4-bis(diphenylphosphino)butane (Table 1, entry 2) were used,
partial conversion and total decomplexation was observed (ratio
Pd-1:1 of 0:100). Fortunately, using triphenylphosphine, PPh2-
(o-tolyl), 1,2-bis(diphenylphosphino)ethane (dppe) or 1,10-bis-
(diphenylphosphino)ferrocene (dppf) as ligands, full conversions
and good yields of 4a were achieved (Table 1, entries 3–6), mono-
dentate PPh2(o-tolyl) (entry 4) and bidentate dppf (entry 6) provid-
ing almost complete recovery of the metal in the form of Pd-1
(ratio Pd-1:1 of 97:3). Taking into account the best compromise
between isolated product yield and palladium recovery, the condi-
tions of entry 6 were adopted for subsequent experiences with
other nucleophiles (but 1.0 equivalent of bidentate phosphine with
respect to palladium was used instead of 1.3 equivalents in further
experiments). The recovered mixture Pd-1:1 97:3 of entry 6 was
used in a second run under the same conditions to afford complete
conversion of the substrates to 4a in the given time (85% isolated
yield of 4a; a 96:4 mixture of Pd-1:1 was recovered).
To extend the scope of the reaction we first tested other aro-
matic secondary and primary amines such as 4-chloro-N-methy-
laniline (3b) and 4-nitroaniline (3c) (Table 2, entries 1 and 2,
respectively), as well as secondary and primary aliphatic amines
such as di-n-hexylamine (3d) and n-dodecylamine (3e) (Table 2,
entries 3 and 4, respectively). Using the secondary amine 3b, N-
cinnamyl-N-methyl-4-chloroaniline, 4b, was obtained in 70% iso-
lated yield and quite good recovery of palladium was achieved
(Table 2, entry 1). Highly acidic and non-nucleophilic 4-nitroan-
iline (3c) (pKa value in DMSO: 20.9, as compared with methanol:
29.0) [18] reacted at room temperature with the carbonate 2 un-
der palladium catalysis, presumably through its conjugate base
[2], but N-cinnamyl-4-nitroaniline, 4c, was obtained in low yield
due to a low conversion (76% of 3c was recovered) and to
decomposition of allylic carbonate 2 during the reaction (Table
2, entry 2). Minor amounts of secondary products derived from
2 such as cinnamyl alcohol and cinnamaldehyde were also ob-
tained. The yields of 4c were not improved with other phosphine
ligands such as PPh3 and PPh2(o-tolyl). Allylation of aniline
derivatives under palladium catalysis has previously been re-
ported with N-allylpyridinium salts [19], allylic carbonates [2a]
and allylic alcohols [20].
2.2.2.3. N-cinnamyl-N, N-dihexylamine, 4d. Eluent: hexane–ethyl
acetate 96:4; IR (ATR):
m ;
= 2927, 2857, 1465, 1376, 782 cmꢀ1 1H
NMR (CDCl3) d = 0.88 (t, J = 6.6 Hz, 6H), 1.28 (m, 12H), 1.47 (m,
4H), 2.45 (m, 4H), 3.24 (d, J = 6.5 Hz, 2H), 6.28 (dt, J = 15.7 and
6.5 Hz, 1H), 6.50 (d, J = 15.7 Hz, 1H), 7.28 (m, 5H); 13C NMR (CDCl3)
d = 14.2, 22.8, 27.1, 27.4, 32.0, 54.1, 56.8, 126.4, 127.3, 128.2, 128.6,
132.1, 137.4. HRMS (ESI): m/z = 302.2839 (calcd for C21H35N + H:
302.2842).
2.2.2.4. N, N-dicinnamyl-N-dodecylamine, 4e. Eluent: hexane–ethyl
acetate 90:10; IR (ATR):
m
= 3025, 2923, 2852, 1599, 1494, 1449,
1362, 1317, 1150, 965, 742, 692, 659, 629 cmꢀ1
;
1H NMR (CDCl3)
d = 0.88 (t, J = 6.6 Hz, 3H), 1.25 (m, 18H), 1.52 (m, 2H), 2.50 (m,
2H), 3.30 (d, J = 6.5 Hz, 4H), 6.30 (dt, J = 15.7 and 6.7 Hz, 2H), 6.52
(d, J = 15.7 Hz, 2H), 7.27 (m, 10H); MS-ESI: m/z = 418 [M+H]+;
HRMS (ESI): m/z = 418.3462 (calcd for C30H44N: 418.3468).
2.2.2.5. 1-Cinnamylbenzotriazole, 4f and 2-cinnamylbenzotriazole, 40
f. Eluent: hexane–ethyl acetate 100:0–95:5; 4f [3f]: 1H NMR
(CDCl3) d = 5.36 (d, J = 6.2 Hz, 2H), 6.36 (dt, J = 15.7 and 6.2 Hz,
1H), 6.65 (d, J = 15.7 Hz, 1H), 7.35 (m, 7H), 7.54 (dt, J = 8.4 and
1.1 Hz, 1H), 8.05 (dt, J = 8.4 and 1.1 Hz, 1H); 40f [3f]: 1H NMR
(CDCl3) d = 5.50 (dd, J = 6.7 and 1.2 Hz, 2H), 6.55 (dt, 15.8 and
6.6 Hz, 2H), 6.79 (d, J = 15.8 Hz, 1H), 7.34 (m, 7H), 7.88 (m, 2H).
2.2.2.6. N, N, N’, N’-tetracinnamylsulfamide, 4g [2b]. Eluent: hex-
ane–ethyl acetate 100:0–90:10; IR (ATR):
m
= 3026, 2924, 2852,
1495, 1448, 1322, 1145, 966, 902, 746, 692 cmꢀ1
;
1H NMR (CDCl3)
d = 4.03 (d = 6.5 Hz, 8H), 6.23 (dt, J = 15.8 and 6.7 Hz, 4H), 6.55 (d,
J = 15.8 Hz, 4H), 7.29 (m, 20H).
2.2.2.7. (Cinnamyloxy)benzene, 4h [15]. Eluent: hexane–ethyl ace-
tate 100:0–98:2; 1H NMR (CDCl3) d = 4.69 (d, J = 5.7 Hz, 2H), 6.41
(dt, J = 16.0 and 5.7 Hz, 1H), 6.73 (d, J = 16.0 Hz, 1H), 6.96 (m,
3H), 7.32 (m, 7H).
2.2.2.8. 1-Cinnamyloxy-2-nitrobenzene, 4i [16]. Eluent: hexane–
ethyl acetate 98:2–90:10; 1H NMR (CDCl3) d = 4.86 (d, J = 5.5 Hz,
2H), 6.39 (dt, J = 16.0 and 5.5 Hz, 1H), 6.79 (d, J = 16.0 Hz, 1H),
7.1–7.6 (m, 8H), 7.85 (dd, J = 8.0 and 1.5 Hz, 1H); MS: m/z = 255
[M+].
2.2.2.9. 1-Cinnamyloxy-4-nitrobenzene, 4j [17]. Eluent: hexane–
ethyl acetate 100:0–90:10; IR (ATR):
m
= 2927, 1590, 1515, 1495,
1339, 1255, 1108, 996, 970, 854, 789, 750 cmꢀ1
;
1H NMR (CDCl3)
d = 4.80 (d, J = 6.0 Hz, 2H), 6.38 (dt, J = 16.0 and 6.0 Hz, 1H), 6.76
(d, J = 16.0 Hz, 1H), 7.01 (d, J = 9.2 Hz, 2H), 7.32 (m, 5H), 8.21 (d,
J = 9.5 Hz, 2H); 13C NMR (CDCl3) d = 69.2, 114.7, 122.8, 125.8,
126.5, 128.2, 128.6, 134.1, 135.9, 163.5. HRMS (ESI): m/
z = 278.0782 (calcd for C15H13NO3 + Na: 278.0788).
2.2.2.10. 1-Cinnamyloxy-4-tert-butylbenzene, 4k. Eluent: hexane–
ethyl acetate 100:0–97:3; IR (ATR):
m = 2960, 2926, 1513, 1260,
1016, 799, 744, 692 cmꢀ1 1H NMR (CDCl3) d = 1.34 (s, 9H), 4.72
;
(d, J = 5.8 Hz, 2H), 6.46 (dt, J = 15.9 and 5.7 Hz, 1H), 6.63 (d,
J = 15.9 Hz, 1H), 6.94 (d, J = 8.6 Hz, 2H), 7.2-7.4 (m, 5H), 7.45 (d,
J = 7.2 Hz, 2H); 13C NMR (CDCl3) d = 31.7, 34.2, 68.8, 114.3, 124.9,
126.4, 126.7, 127.9, 128.7, 132.9, 136.6, 143.7, 156.5; HRMS
(ESI): m/z = 289.1552 (calcd for C19H22O + Na: 289.1563).
A more nucleophilic secondary aliphatic amine 3d afforded 4d
in good yield in a room temperature reaction (Table 2, entry 3)
and the primary amine 3e gave the diallylation product 4e under
similar conditions when equimolar amounts of reagents were used

A. Serra-Muns, R. Pleixats / Journal of Organometallic Chemistry 695 (2010) 1231–1236
1235
(73% yield with respect to 2) (Table 2, entry 4). Unfortunately, the
Acknowledgements
recovery of the palladium complex was inferior in these cases (ra-
tios Pd-1:1 of 50:50 and 19:81 for entries 3 and 4). However, it
must be taken into account that palladium is catalytic and the
Pd-1 complex acts as a precatalyst and metal reservoir. Thus, all
the recovered mixtures containing complexed palladium are useful
to be reused in a second run.
Financial support from MEC and MICINN of Spain (Projects
CTQ2005-04968/BQU, CTQ2006-04204/BQU, and predoctoral
scholarship to A.S-M.), Consolider Ingenio 2010 (Project
CSD2007-00006), and Generalitat de Catalunya (Projects
SGR2005-00305 and SGR2009-01441) is gratefully acknowledged.
We thank A. Monge for technical assistance.
The reaction with an ambident nucleophilic heterocycle such as
benzotriazole (3f) under these mild conditions provided a mixture
of the regioisomers 4f and 40f derived from the allylation at N-1
and N-2 positions in an excellent 91% global yield and a selectivity
of 1:1.8 in favour of 40f (Table 2, entry 5). Although the macrocycle
1 was fully recovered uncomplexed, it is worth to mention that
previous essays in our group [3f] with the same nucleophile in
refluxing dioxane under Pd(PPh3)4 catalysis afforded a mixture of
compounds with lower yields and a lower regioselectivity (ratio
4f:40f of 1:1.4). Later on, Sinou [21] reported also mixtures of
regioisomers in the allylation of 3f with a carbonate derived from
an unsaturated carbohydrate. Benzotriazole has been found to
form palladium complexes [22]. The competition of 3f with our
macrocycle as ligand for the metal could be on the origin of the
recovery of fully uncomplexed macrocycle 1. Tetraallylation of
highly acidic and non nucleophilic sulfamide was achieved in the
absence of external base using an excess of the carbonate (2:3 ratio
of 5:1) at room temperature (Table 2, entry 6). Decomplexation of
Pd-1 after the reaction was also observed. It is worth to mention
that although reactions of sulfamide with carbonyl groups and
with nitriles are well precedented [23], this is not so for alkyla-
tions, and substituted sulfamides are best prepared by nucleophilic
attack of amines on the sulphur atom with elimination of ammonia
[24]. Next, we turned to oxygen-based nucleophiles such as phenol
(3h), 2-nitrophenol (3i), 4-nitrophenol (3j) and 4-tert-butylphenol
(3k) (Table 2, entries 7–10, respectively). For 3h, 3i and 3j the reac-
tion mixture was heated at reflux in order to enhance the reaction
rate. Ether 4h was obtained from phenol in quantitative yield (Ta-
ble 2, entry 7). For the electron-poor and more acidic nitrophenols
3i and 3j (pKa = 10.8 for 3j in DMSO) [18], the isolated yields were
modest and secondary products derived from the carbonate 2 were
detected by GC–MS, such as cinnamyl alcohol and cinnamyl ethyl
ether (Table 2, entries 8 and 9). For the more electron-rich phenol
3k, good yield of 4k was achieved at room temperature (Table 2,
entry 10). The recovery of Pd-1 varies depending on the nucleo-
phile (ratio Pd-1:1 from 98:2 for phenol to 55:45 for 4-nitrophe-
nol). In all cases the O-allylation products were obtained as in
other previously reported synthesis of allylic aryl ethers from
allylic carbonates and phenols under palladium catalysis [25]
although C-allylation of naphthols and benzene polyols by allyl
alcohols [26] and allylic carbonates [25b] has also been described.
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