(η3-allyl)palladium complexes bearing diphosphinidenecyclobutene ligands: Highly active catalysts for the hydroamination of 1,3-dienes

Article abstract of DOI:10.1002/1521-3773(20011203)40:23<4501::AID-ANIE4501>3.0.CO;2-K

Room-temperature hydroamination of 1,3-dienes with aniline [Eq. (1)] is efficiently catalyzed by cationic η³-allyl palladium complexes, prepared by treating [{(η³-allyl)PdCl)}₂] with 1,2-diaryl-3,4-bis[(2,4,6-tri-tert-buty

Full text of DOI:10.1002/1521-3773(20011203)40:23<4501::AID-ANIE4501>3.0.CO;2-K

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3
(
h -Allyl)palladium Complexes Bearing
R
R
+
Ar
P
OTf–
Diphosphinidenecyclobutene Ligands:
Highly Active Catalysts for the
Hydroamination of 1,3-Dienes**
Pd
P
Tatsuya Minami, Hideyuki Okamoto, Shintaro Ikeda,
Rika Tanaka, Fumiyuki Ozawa,* and Masaaki Yoshifuji
Ar
Ar = 2,4,6-tri-tert-butylphenyl
1
: R = H; 2: R = OMe; 3: R = CF3
Dedicated to Prof. FranÁois Mathey
on the occasion of his 60th birthday
(AgOTf) inCH Cl at room temperature, and isolated as
2
2
yellowish orange solids in 66 ± 96% yields.[ They are fairly
stable towards air insolutionand as solids; the solid materials
canbe stored at room temperature for mo tnh s without
notable decomposition.
14]
The catalytic hydroamination of unsaturated hydrocarbons
is a useful means of synthesizing nitrogen-containing organic
molecules.[ Intramolecular cyclization of aminoalkenes is
1]
[
2]
[15]
efficiently catalyzed by lanthanide complexes, and amine-
Figure 1 shows the molecular structure of 1. The diphos-
[3]
3
induced telomerization of butadienes and oxidative 1,4-
addition of amines to dienes[ are successfully conducted with
palladium catalysts. In contrast, simple intermolecular 1:1
addition of amines to alkenes or dienes is a rather difficult
process and has been conducted at high temperature.[
Hartwig et al. recently reported a significantly improved
catalyst, generated from [Pd(PPh ) ] an d CFCO H, which
phinidenecyclobutene ligand chelates the (h -allyl)palladium
4]
5, 6]
3
4
3
2
performs 1:1 addition of aniline to 1,3-dienes at room
temperature.[ However, eveninthis case, the reactiontakes
about a day for completion. Here we report that more
7]
2
efficient catalysts can be prepared by using sp -hybridized
phosphorus ligands, namely, 1,2-diaryl-3,4-bis[(2,4,6-tri-tert-
[
8]
butylphenyl)phosphinidene]cyclobutenes.
Figure 1. Molecular structure of the cationincrystals of
6 6
1 ¥ 2C H .
2
sp -Hybridized phosphorus compounds have a marked
Thermal ellipsoids are drawnat the 30% probability level. Triflate a ni o n,
propensity to engage in metal-to-phosphorus p backbonding
and have a strong p-acceptor property, comparable to that of
the carbonyl ligand.[9] Since the catalytic additionof anamine
benzene molecules (solvent of crystallization), and hydrogen atoms are
omitted for clarity. Selected bond lengths [ä] and angles [8]: Pd-P(1)
2.326(1), Pd-P(2) 2.322(1), Pd-C(53) 2.168(5), Pd-C(54) 2.168(5), Pd-C(55)
2
.178(4), P(1)-C(19) 1.667(4), P(2)-C(22) 1.671(4), C(19)-C(20) 1.476(5),
to a 1,3-diene probably involves nucleophilic attack of the
C(19)-C(22) 1.499(5), C(20)-C(21) 1.406(5), C(21)-C(22) 1.464(5), C(53)-
C(54) 1.383(8), C(54)-C(55) 1.376(8); P(1)-Pd-P(2) 85.50(4), Pd-P(1)-C(19)
3
amine on an (h -allyl)palladium(ii) or palladium(ii) diene
complex,[ we expected that diphosphinidenecyclobutene
ligands may effectively enhance the electrophilicity of palla-
dium intermediates and thus give highly active catalysts.
7a]
1
07.6(1), Pd-P(2)-C(22) 107.4(1), P(1)-C(19)-C(22) 119.6(3), C(20)-C(19)-
C(22) 87.8(2), P(2)-C(22)-C(19) 119.9(3), C(19)-C(22)-C(21) 88.5(3),
C(19)-C(20)-C(21) 91.7(3), C(20)-C(21)-C(22) 91.9(3), C(53)-C(54)-C(55)
1
19.9(5). Dihedral angles between least-squares planes [8]: [A]-[B] 2.3(1),
2
Although transition metal complexes of sp -hybridized phos-
[
A]-[C] 93.2(1), [A]-[D] 100.3(1), [B]-[E] 28.2(2), [B]-[F] 147.8(2).
phorus compounds have been extensively prepared in the last
[9]
decade, their applicationto catalysis has beenextremely
limited,[
10]
moiety through two phosphorus atoms. The aryl rings C and D
on the phosphorus atoms are nearly perpendicular to the main
framework A, whereas the almost parallel arrangement of
phenyl groups E and F and the cyclobutene ring B suggests
partial p conjugation between them. The C(53)ÀC(54) and
C(54)ÀC(55) bond lengths (1.383(8) and 1.376(8) ä) and the
except for phosphaaromatic compounds such as
[11, 12]
phosphabenzene and phosphaferrocene.
Complexes 1 ± 3 were synthesized by treating [{Pd-
3
[13]
(
h -allyl)Cl} ] with the corresponding diphosphinidenecy-
2
clobutene ligand and silver trifluoromethanesulfonate
[
*] Prof. Dr. F. Ozawa, Dr. T. Minami, H. Okamoto, S. Ikeda, R. Tanaka
Department of Applied Chemistry
Graduate School of Engineering
C(53)-C(54)-C(55) angle (119.9(5)8) are inthe typical ra ng es
3
for h -allyl ligands. The three PdÀC distances (2.168(5) ±
2
.178(4) ä) are comparable to those of diphosphane ana-
Osaka City University
[16]
logues (2.168 ± 2.201 ä).
Sumiyoshi-ku, Osaka 558-8585 (Japan)
Fax : (‡81)6-6605-2978
Complex 1 is extremely reactive towards amines [Eq. (1)].
Treatment of 1 with diethylamine (10 mol equiv) in benzene
E-mail: ozawa@a-chem.eng.osaka-cu.ac.jp
Prof. Dr. M. Yoshifuji
Department of Chemistry
Graduate School of Science
Tohoku University
Aoba, Sendai 980-8578 (Japan)
[
**] This work was supported by a Grant-in-Aid for Scientific Research
from the Ministry of Education, Science, Sports and Culture, Japan.
at room temperature led to instant formation of 3-(N,N-
diethylamino)propene in 82% yield. Similarly, the reaction
with aniline afforded a 45% yield of 3-(N-phenylamino)pro-
Supporting information for this article is available on the WWW under
http://www.angewandte.com or from the author.
Angew. Chem. Int. Ed. 2001, 40, No. 23
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1433-7851/01/4023-4501 $ 17.50+.50/0
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pene within a few minutes.[ In contrast, the diphosphane
17]
Table 2. Hydroamination of dienes with aniline catalyzed by 2.[a]
3
analogues [Pd(h -allyl)(dppe)]OTf (dppe ˆ 1,2-bis(diphenyl-
Product(s)[b]
Entry
Diene
Time
[h]
Yield
3
[c]
phosphanyl)ethane) and [Pd(h -allyl)(dppf)]OTf (dppf ˆ 1,1'-
[%]
bis(diphenylphosphanyl)ferrocene) were totally unreactive
towards aniline under the same reaction conditions.
The high reactivity of 1 was also demonstrated in the
catalytic hydroamination of 1,3-cyclohexadiene with anilines
1
6
80
[Eq. (2)]. A typical procedure follows: Aniline (0.18 mL,
1.98 mmol) was added to a solutionof 1 (21.0 mg, 0.020 mmol)
2
3
5
3
92
92
4
5
96
and 1,3-cyclohexadiene (0.10 mL, 1.05 mmol) in toluene
2 mL) under nitrogen. The mixture was stirred at room
(
temperature for 5 h. Analysis by GLC revealed complete
consumption of the diene. The reaction mixture was concen-
trated to dryness by pumping, and the residue purified by
5
6
6
85
68
columnchromatography (SiO , hexane/AcOEt 100/1) to give
2
162 mg (89% yield) of 3-(N-phenylamino)cyclohexene.
Representative results are listed in Table 1. The catalytic
activity significantly decreased with increasing solvent polar-
ity (entries 1 ± 5). Toluene was among the best solvents
examined. The reaction did not proceed in DMF, and
precipitationof palladium black occurred. Complex 2 (R ˆ
OMe) showed catalytic activity comparable to that of 1
24
[a] All reactions were conducted at room temperature in toluene (2 mL)
with diene (1.0 mmol), aniline (2.0 mmol), and catalyst (0.02 mmol).
1
[
b] The ratio of isomers was determined by H NMR analysis. [c] Yield of
(
entry 6), whereas CF -substituted 3 was less active (en-
3
isolated product.
[18]
try 9). Hydroamination with para-substituted anilines was
also successful (entries 7 and 8).
Table 1. Hydroamination of 1,3-cyclohexadiene with anilines catalyzed by
[
a]
1
± 3 [Eq. (2)].
Entry
Catalyst
Y
Solvent
Yield [%][b]
1
2
3
4
5
6
7
8
9
1
1
1
1
1
2
2
2
3
H
H
H
H
H
H
F
OMe
H
toluene
THF
dioxane
89
59
30
2
In conclusion, we have found highly active catalysts for the
hydroamination of 1,3-dienes with aniline. The reactions
readily proceed at room temperature to give the correspond-
ing 1,2- or 1,4-addition products in high yields. The use of
diphosphinidenecyclobutene ligands with sp -hybridized
phosphorus atoms having strong p-acceptor ability is of
CH
2 2
Cl
DMF
0
toluene
toluene
toluene
toluene
91
90
88
58
2
particular importance for the catalytic activity.
[
(
a] All reactions were conducted at room temperature for 5 h with diene
1.0 mmol), aniline (2.0 mmol), catalyst (0.02 mmol), and solvent (2 mL).
Received: July 26, 2001 [Z17610]
[
b] Yield of isolated product.
[
1] For reviews, see a) R. Taube in Applied Homogeneous Catalysis with
Organometallic Compounds, Vol. 1 (Eds.: B. Cornils, W. A. Herr-
mann), VCH, Weinheim, 1996, p. 507; b) T. E. M¸ller, M. Beller,
Chem. Rev. 1998, 98, 675.
Avariety of 1,3-dienes could be hydroaminated with aniline
ingood to excelle nt yields (Table 2). All reactions proceeded
smoothly at room temperature, except for entry 6, in which
about 30% of unconsumed diene starting material was
recovered. 1,2-Addition to a terminal vinyl group is preferred
when one of the termini of the diene unit is substituted
[
2] a) M. R. Gagn e¬ , C. L. Stern, T. J. Marks, J. Am. Chem. Soc. 1992, 114,
2
75; b) S. Tian, V. M. Arredondo, C. L. Stern, T. J. Marks, Organo-
metallics 1999, 18, 2568.
[
3] J. Tsuji, Transition Metal Reagents and Catalysts, Wiley, Chichester,
2000, p. 169.
(
entries 1, 2, and 5). Otherwise, 1,4-addition to the diene takes
[4] a) J. E. B‰ckvall, Acc. Chem. Res. 1983, 16, 335; b) J. E. B‰ckvall, Pure
Appl. Chem. 1992, 64, 429.
place exclusively (entries 3, 4, and 6).
[
5] a) M. Beller, H. Trauthwein, M. Eichberger, C. Breindl, J. Herwig,
T. E. M¸ller, O. R. Thiel, Chem. Eur. J. 1999, 5, 1306; b) M. Beller, H.
Trauthwein, M. Eichberger, C. Breindl, T. E. M¸ller, Eur. J. Inorg.
Chem. 1999, 1121; c) U. Radhakrishnan, M. Al-Masum, Y. Yamamoto,
The present catalysts were also effective for 1,2-addition of
aniline to styrene at 1008C [Eq. (3)]. Complex 2 gave the best
result: a 90% yield of {1-(N-phenylamino)ethyl}benzene.
4502
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COMMUNICATIONS
Tetrahedron Lett. 1998, 39, 1037; d) M. Al-Masum, M. Meguro, Y.
Yamamoto, Tetrahedron Lett. 1997, 38, 6071; e) R. Dorta, P. Egli, F.
Zurcher, A. Togni, J. Am. Chem. Soc. 1997, 119, 10857; f) L. Besson, J.
G o¬ re, B. Cazes, Tetrahedron Lett. 1995, 36, 3857; g) R. W. Armbruster,
M. M. Morgan, J. L. Schmidt, C. M. Lau, R. M. Riley, D. L. Zabrow-
ski, H. A. Dieck, Organometallics 1986, 5, 234; h) K. Takahashi, A.
Miyake, G. Hata, Bull. Chem. Soc. Jpn. 1972, 45, 1183.
1998, 1163; c) R. Shintani, M. M.-C. Lo, G. C. Fu, Org. Lett. 2000, 2,
3695; d) K. Tanaka, S. Qiao, M. Tobisu, M. M.-C. Lo, G. C. Fu, J. Am.
Chem. Soc. 2000, 122, 9870.
[13] Y. Tatsuno, T. Yoshida, S. Otsuka, Inorg. Synth. 1990, 28, 343.
[14] Complexes 1 ± 3 were characterized by NMR spectroscopy and
elemental analysis: see Supporting Information.
[15] A single crystal of dimensions ca. 0.40 Â 0.25 Â 0.15 mm was grownby
[
6] For the 1:1 addition of amines to activated alkenes such as enones, see
a) M. J. Gaunt, J. B. Spencer, Org. Lett. 2001, 3, 25; b) M. Kawatsura,
J. F. Hartwig, Organometallics 2001, 20, 1960; c) X. Cheng, K. K. Hii,
Tetrahedron 2001, 57, 5445.
slow evaporation of the benzene solution at room temperature.
Crystallographic data for 1 ¥ 2C
6
H
6
: C68
H
85
O
3
P
2
SF
3
Pd, M
r
ˆ 1207.82,
orthorhombic, space group Pbca (no. 61), a ˆ 29.3798(4), b ˆ
3
27.9193(4), c ˆ 16.6779(2) ä, Vˆ 13680.3(5) ä , Z ˆ 8,
1
calcd
ˆ
À3
À1
[
7] a) O. Lˆber, M. Kawatsura, J. F. Hartwig, J. Am. Chem. Soc. 2001, 123,
1.173 gcm , m(MoKa) ˆ 3.98 cm , Tˆ 296 K, 2qmax ˆ 55.08; of the
116497 reflections collected, 15690 were independent (Rint ˆ 0.044)
4
9
366; b) M. Kawatsura, J. F. Hartwig, J. Am. Chem. Soc. 2000, 122,
546.
and used for the structure refinement (625 parameters); R
1
ˆ 0.044,
2
2
2
[
8] a) R. Appel, V. Winkhaus, F. Knoch, Chem. Ber. 1987, 120, 243; b) G.
M‰rkl, P. Kreitmeier, H. Nˆth, K. Polborn, Angew. Chem. 1990, 102,
R(F ) ˆ 0.073, R
w
(F ) ˆ 0.133 for 8198 data with I > 3s(I); R(F ) ˆ
2
0.085, R
w
(F ) ˆ 0.158 for all data. Crystallographic data (excluding
9
58; Angew. Chem. Int. Ed. Engl. 1990, 29, 927; c) M. Yoshifuji, K.
structure factors) for the structure reported inthis paper have been
deposited with the Cambridge Crystallographic Data Centre as
supplementary publication no. CCDC-167652. Copies of the data
canbe obtai ne d free of charge onapplicationto CCDC, 12 U ni on
Road, Cambridge CB21EZ, UK (fax: (‡44)1223-336-033; e-mail:
deposit@ccdc.cam.ac.uk).
Toyota, M. Murayama, H. Yoshimura, A. Okamoto, K. Hirotsu, S.
Nagase, Chem. Lett. 1990, 2195; d) K. Toyota, K. Tashiro, M. Yoshifuji,
S. Nagase, Bull. Chem. Soc. Jpn. 1992, 65, 2297; e) M. Yoshifuji, Y.
Ichikawa, N. Yamada, K. Toyota, Chem. Commun. 1998, 27.
[
9] For reviews, see a) P. Le Floch, F. Mathey, Coord. Chem. Rev. 1998,
1
79/180, 771; b) F. Mathey, Acc. Chem. Res. 1992, 25, 90; M. Yoshifuji,
[16] a) T. Hayashi, A. Yamamoto, Y. Ito, E. Nishioka, H. Miura, K. Yanagi,
J. Am. Chem. Soc. 1989, 111, 6301; b) S. L. James, A. G. Orpen, P. G.
Pringle, J. Organomet. Chem. 1996, 525, 299.
J. Chem. Soc. Dalton Trans. 1998, 3343.
[
10] a) K. Toyota, K. Masaki, T. Abe, M. Yoshifuji, Chem. Lett. 1995, 221;
b) S. Ikeda, F. Ohhata, M. Miyoshi, R. Tanaka, T. Minami, F. Ozawa,
M. Yoshifuji, Angew. Chem. 2000, 112, 4686; Angew. Chem. Int. Ed.
[17] After rapid formationinthe i int ial phase, the reactionbecame
significantly slower, probably due to simultaneous decomposition of
palladium species (precipitationof palladium-black was no ted). The
yield of 3-(N-phenylamino)propene reached 72% after prolonged
reactiontime (24 h).
2
000, 39, 4512.
[
11] a) F. Mathey, P. Le Floch, Chem. Ber. 1996, 129, 263; b) F. Knoch, F.
Kremer, U. Schmidt, U. Zenneck, P. Le Floch, F. Mathey, Organo-
metallics 1996, 15, 2713; c) B. Breit, Chem. Commun. 1996, 437; d) B.
Breit, J. Mol. Catal. A 1999, 143, 143; e) B. Breit, R. Winde, T.
Mackewits, R. Paciello, K. Harms, Chem. Eur. J. 2001, 7, 3106.
3
[18] It was confirmed that the diphosphane complexes [Pd(h -allyl)-
3
(dppe)]OTf and [Pd(h -allyl)(dppf)]OTf were inactive towards the
catalytic reactionof Equation(2) at room temperature.
[
12] a) X. Sava, L. Ricard, F. Mathey, P. Le Floch, Organometallics 2000,
1
9, 4899; b) C. Ganter, C. Glinsbˆckel, B. Ganter, Eur. J. Inorg. Chem.
Angew. Chem. Int. Ed. 2001, 40, No. 23
¹ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
1433-7851/01/4023-4503 $ 17.50+.50/0
4503