Successive O-C/O-H and sp3 C-H bond activation of ortho substituents in allyl phenyl ethers and phenols by a ruthenium(0) complex

Article abstract of DOI:10.1021/om970911q

Successive O-C and sp³ C-H bond activation occurs in the reaction of Ru(COD)(COT) (1)/PMe₃ with allyl 2,6-xylyl ether to give Ru[OC₆H₃(o-CH₂)(o′-Me)](PMe ₃)₄ (4). Alternatively, 4 can be obtained by O-H and sp³ C-H bond activation in 2,6-xylenol by 1/PMe₃. In both cases, an η³-allyl fragment could be responsible for the sp³ C-H bond activation.

Full text of DOI:10.1021/om970911q

Organometallics 1998, 17, 501-503
501
Su ccessive O-C/O-H a n d sp 3 C-H Bon d Activa tion of
or th o Su bstitu en ts in Allyl P h en yl Eth er s a n d P h en ols
by a Ru th en iu m (0) Com p lex
Masafumi Hirano, Naoki Kurata, Tsuyoshi Marumo, and Sanshiro Komiya*
Department of Applied Chemistry, Faculty of Technology, Tokyo University of Agriculture and
Technology, 2-24-16 Nakacho, Koganei, Tokyo 184-8588, J apan
Received October 17, 1997
Summary: Successive O-C and sp3 C-H bond activa-
tion occurs in the reaction of Ru(COD)(COT) (1)/ PMe3
transition metals8 and ortho-substituted phenyl isocya-
nides by RuH(naphthyl)(dmpe)2.9
In the C-H bond activation process, the presence of
a hydrogen acceptor may facilitate metal-carbon bond
formation. We have previously reported oxidative ad-
dition of the O-C bond of allyl esters in the presence of
Ru(1,5-COD)(1,3,5-COT) (1; COD ) cyclooctadiene, COT
) cyclooctatriene) and a tertiary phosphine to give Ru-
(OCOR)(η3-C3H5)(PR′3)3.10 Because η3-allyl ligands are
known to be good hydride and halide acceptors,11 we
anticipated that the η3-allyl group in the ruthenium
complexes could promote further intramolecular activa-
tions. In this paper, we wish to communicate successive
O-C/O-H and sp3 C-H bond activations of ortho
substituents in allyl phenyl ethers and phenols by 1 in
the presence of tertiary phosphines under neutral and
mild conditions.
The reaction of allyl phenyl ether with 1 at 50 °C in
the presence of PMe3 resulted in the formation of Ru-
(OPh)(η3-C3H5)(PMe3)3 (2) in 37% yield (Scheme 1);12 the
molecular structure of 2 is depicted in Figure 1.13
The structure of 2 shows that oxidative addition of
the O-C bond of the ether had occurred to give an (η3-
allyl)(phenoxo)ruthenium(II) complex. Similarly, treat-
ment of 1/PMe3 with allyl 2-tolyl ether resulted in
with allyl 2,6-xylyl ether to give Ru[OC6H3(o-CH2)(o′-
Me)](PMe3)4 (4). Alternatively, 4 can be obtained by
O-H and sp3 C-H bond activation in 2,6-xylenol by
1/ PMe3. In both cases, an η3-allyl fragment could be
responsible for the sp3 C-H bond activation.
C-H bond activation by transition-metal complexes
is an important area of organometallic chemistry, due
to its potential utility in organic synthesis.1 Although
most recent efforts in this area concern the activation
of simple alkanes, selective C-H bond activation of
functionalized molecules is also important. Examples2
of this are known with low-valent ruthenium complexes,
e.g., regioselective C-H bond activation in acrylates3
and catalytic ortho C-H bond activation in pyridines4
and aromatic ketones.5 These results show the impor-
tance of prior coordination to bring the unreactive C-H
bond near the metal center. Although substitution at
ortho positions in a ligand has been used to block
undesired ortho metalation6 or to increase steric conges-
tion, C-H bond activation of ortho substituents by late-
transition-metal complexes is relatively unexplored.7
Published examples include the sp3 C-H bond activa-
tion of ortho-substituted aryloxo ligands by group 6
(6) For recent articles dealing with ortho metalations of aryl alcohols
and carboxylates by ruthenium complexes: (a) Hartwig, J . F.; Berg-
man, R. G.; Andersen, R. A. J . Organomet. Chem. 1990, 394, 417. (b)
Bag, N.; Bhanja Choudhury, S.; Pramanik, A.; Kumar Lahiri, G.;
Chakravorty, A. Inorg. Chem. 1990, 29, 5013. (c) Hartwig, J . F.;
Bergman, R. G.; Andersen, R. A. J . Am. Chem. Soc. 1991, 113, 3404.
(d) Hartwig, J . F.; Bergman, R. G.; Andersen, R. A. J . Am. Chem. Soc.
1991, 113, 6499. (e) Ozawa, F.; Yamagami, I.; Yamamoto, A. J .
Organomet. Chem. 1994, 473, 265.
(7) C-H bond activations of substituent groups at the ortho positions
are carried out by early-transition-metal aryloxides: (a) Rothwell, I.
P. Acc. Chem. Res 1988, 21, 153. (b) Yu, J . S.; Fanwick, P. E.; Rothwell,
I. P. J . Am. Chem. Soc. 1990, 112, 8171. (c) Visciglio, V. M.; Clark, J .
R.; Nguyen, M. T.; Mulford, D. R.; Fanwick, P. E.; Rothwell, I. P. J .
Am. Chem. Soc. 1997, 119, 3490 and references therein.
(8) (a) Rabinovich, D.; Zelman, R.; Parkin, G. J . Am. Chem. Soc.
1990, 112, 9632. (b) Rabinovich, D.; Zelman, R.; Parkin, G. J . Am.
Chem. Soc. 1992, 114, 4611. (c) Hascall, T.; Murphy, V. J .; Parkin, G.
Organometallics 1996, 15, 3910.
(9) (a) J ones, W. D.; Kosar, W. P. J . Am. Chem. Soc. 1986, 108, 5640.
(b) Hsu, G. C.; Kosar, W. P.; J ones, W. D. Organometallics 1994, 13,
385.
(10) Komiya, S.; Kabasawa, T.; Yamashita, K.; Hirano, M.; Fukuoka,
A. J . Organomet. Chem. 1994, 471, C6. Reaction of 1/PEt3 with vinyl
acetate: Komiya, S.; Suzuki, J .; Miki, K.; Kasai, N. Chem. Lett. 1987,
1287.
(11) (a) Minami, I.; Yamada, M.; Tsuji, J . Tetrahedron Lett. 1986,
27, 1805. (b) Maruyama, Y.; Sezaki, T.; Tekawa, M.; Sakamoto, T.;
Shimizu, I.; Yamamoto, A. J . Organomet. Chem. 1994, 473, 257. (c)
Nagashima, H.; Mukai, K.; Shiota, Y.; Yamaguchi, K.; Ara, K.;
Fukahori, T.; Suzuki, H.; Akita, M.; Moro-oka, Y.; Itoh, K. Organome-
tallics 1990, 9, 799.
* To whom correspondence should be addressed. E-mail: komiya@
cc.tuat.ac.jp. FAX +81-423-87-7500.
(1) (a) Shilov, A. E. The Activation of Saturated Hydrocarbons by
Transition Metal Complexes; Reidel: Dordrecht, The Netherlands, 1984.
(b) Crabtree, R. H. Chem. Rev. 1985, 85, 245. (c) Wasserman, E. P.;
Moore, C. B.; Bergman, R. G. Science 1992, 255, 315. (d) Homogeneous
Transition Metal Catalyzed Reactions; Moser, W. R., Slocum, D. W.,
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(2) For examples: (a) Ittel, S. D.; Tolman, C. A.; English, A. D.;
J esson, J . P. J . Am. Chem. Soc. 1978, 100, 7577. (b) Hartwig, J . F.;
Bergman, R. G.; Andersen, R. A. J . Am. Chem. Soc. 1991, 113, 3404.
(c) Hartwig, J . F.; Bergman, R. G.; Andersen, R. A. Organometallics
1991, 10, 3326, 3344. (d) Murahashi, S.-I.; Naota, T.; Taki, H.; Mizuno,
M.; Takaya, H.; Komiya, S.; Mizuho, Y.; Oyasato, N.; Hiraoka, M.;
Hirano, M.; Fukuoka, A. J . Am. Chem. Soc. 1995, 117, 12436. (e)
Gomez-Bengoa, E.; Cuerva, J . M.; Mateo, C.; Echavarren, A. M. J . Am.
Chem. Soc. 1996, 118, 8553.
(3) (a) Komiya, S.; Yamamoto, A. Chem. Lett. 1975, 475. (b) Komiya,
S.; Ito, T.; Cowie, M.; Yamamoto, A.; Ibers, J . A. J . Am. Chem. Soc.
1976, 98, 3874.
(4) Moore, E. J .; Pretzer, W. R.; O’Connell, T. J .; Harris, J .;
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5888.
(5) (a) Murai, S.; Kakiuchi, F.; Sekine, S.; Tanaka, Y.; Kamatani,
A.; Sonoda, M.; Chatani, N. Nature 1993, 366, 529. (b) Murai, S. J .
Synth. Org. Chem., J pn. 1994, 52, 992. (c) Sonoda, M.; Kakiuchi, F.;
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references therein.
S0276-7333(97)00911-4 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 01/27/1998

502 Organometallics, Vol. 17, No. 4, 1998
Communications
Sch em e 1
netically inequivalent PMe3 ligands at 0.90 (d, J ) 7.2
Hz, 9H), 1.00 (t, J ) 2.9 Hz, 18H), and 1.17 ppm (d, J
) 5.7 Hz, 9H), where the virtual triplet at 1.00 ppm
indicates two mutually trans PMe3 ligands. One of the
1
most significant features in the H NMR spectrum is a
triplet of triplets at 2.68 ppm, assignable to the ortho
methylene group coupled to two magnetically equivalent
(12) Spectroscopic and physical data (1H NMR at 300.4 MHz, 13C-
{1H} NMR at 75.5 MHz, 31P{1H} NMR at 121.6 MHz from H3PO4, in
C6D6, J in Hz) are as follows. Data for 2: 1H NMR δ 0.46 (d, J ) 8,
9H), 1.27 (d, J ) 8, 18H), 2.42 (dd, J ) 12, 4, 2H), 2.85 (d, J ) 8, 2H),
3.99 (m, 1H), 6.5-6.8 and 7.2-7.4 (m); 31P{1H} NMR δ 1.54 (d, J )
39, 2P), 28.1 (t, J ) 39, 1P). Anal. Found: C, 47.15; H, 8.61. Calcd for
C
18H37OP3Ru: C, 46.65; H, 8.05. Complex 3 was characterized spec-
troscopically. Data for 3: 1H NMR δ 0.48 (d, J ) 8, 9H), 1.25 (d, J )
7, 18H), 2.41 (d, J ) 12, 2H), 2.50 (br s, 3H), 3.01 (d, J ) 8, 2H), 4.01
(m, 1H), 6.6-7.3 (m, 4H); 31P{1H} NMR δ -1.92 (d, J ) 39, 2P), 25.1
(t, J ) 39, 1P). Data for 4: 1H NMR δ 0.90 (d, J ) 7.2, 9H), 1.00 (t, J
) 2.9, 18H), 1.17 (d, J ) 5.7, 9H), 2.53 (s, 3H), 2.68 (tt, J ) 14.3, 3.5,
2H), 6.7-6.9, 7.1-7.2, and 7.4-7.5 (m); 31P{1H} NMR δ -13.8 (td, J
) 24, 13, 1P), -0.96 (dd, J ) 32, 24, 2P), 10.7 (td, J ) 32, 13, 1P);
13C{1H} NMR δ 17.8 (s), 17.9 (td, J ) 11, 3), 22.4 (d, J ) 14), 23.2 (dq,
J ) 54, 10), 24.7 (d, J ) 24), 112.2 (s), 124.5 (s), 126.0 (s), 129.4 (s),
138.4 (s), 173.2 (s). Anal. Found: C, 45.90; H, 8.50. Calcd for C20H44
-
F igu r e 1. ORTEP drawing of 2. All hydrogen atoms are
omitted for clarity. Bond distances and angles for 2 are
included in the Supporting Information.
OP4Ru: C, 45.71; H, 8.44. Data for 6a : 1H NMR δ 0.53 (d, J ) 8.1,
9H), 1.09 (d, J ) 7.2, 9H), 1.26 (d, J ) 7.5, 9H), 1.91 (dd, J ) 12.3, 4.5,
1H), 2.95 (m, 1H), 4.20 (dq, J ) 12.3, 7.5, 1H), 4.89 (dt, J ) 7.5, 3.6,
1H), 6.66 (t, J ) 7.3, 1H), 6.85 (d, J ) 8.1, 1H), 7.15 (ddd, J ) 8.1, 7.3,
1.8, overlapped with C6H6), 7.41 (dd, J ) 7.3, 1.8, 1H); 31P{1H} NMR
δ -11.4 (t, J ) 25, 1P), -0.49 (dd, J ) 25, 16, 1P), -0.38 (dd, J ) 25,
16, 1P). Anal. Found: C, 46.75; H, 7.63; Calcd for C18H35OP3Ru: C,
46.85; H, 7.64. Data for 6b: 1H NMR δ 0.72 (dt, J ) 12.2, 7.6, 9H),
1.01 (dt, J ) 12.2, 7.6, 9H), 1.10 (dt, J ) 12.2, 7.6, 9H), 1.25 (dq, J )
14.6, 7.6, 3H), 1.57 (dq, J ) 14.6, 7.6, 3H), 1.73 (dq, J ) 14.6, 7.6, 3H
overlapped 1H), 1.88 (dq, J ) 14.6, 7.6, 3H), 2.01 (dq, J ) 14.6, 7.6,
3H), 3.03 (m, 1H), 4.63 (dq, J ) 19.7, 7.4, 1H), 5.60 (dt, J ) 7.4, 3.5,
1H), 6.67 (td, J ) 7.2, 1.2, 1H), 6.80 (d, J ) 8.1, 1H), 7.16 (overlapped
with C6H6), 7.46 (dd, J ) 7.5, 1.8, 1H); 31P{1H} NMR δ 21.0 (dd, J )
32, 12, 1P), 22.6 (dd, J ) 32, 12, 1P), 32.8 (t, J ) 32, 1P); 13C{1H}
NMR δ 9.0 (d, J ) 4), 9.4 (d, J ) 4), 9.6 (d, J ) 4), 21.2 (d, J ) 18),
22.4 (d, J ) 18), 22.9 (d, J ) 18), 47.1 (dd, J ) 23, 3), 71.4 (dd, J ) 23,
3), 92.5 (s), 111.8 (s), 118.2 (d, J ) 5), 127.2 (s), 130.7 (s), 172, 2 (d, J
) 8). Anal. Found: C, 55.10, H, 8.92. Calcd for C27H53OP3Ru: C, 55.18;
H, 9.09.
oxidative addition of the O-C bond to give Ru[OC6H4-
(o-Me)](η3-C3H5)(PMe3)3 (3) in 30% yield. Although
oxidative addition of the O-C bond of ethers to group
10 metals is well-established,14 such a reaction with
ruthenium is unprecedented.
When allyl 2,6-xylyl ether was employed in this
reaction, the analogous (η3-allyl)ruthenium(II) complex
was not formed and a new oxaruthenacycle complex, Ru-
[OC6H3(o-CH2)(o′-Me)](PMe3)4 (4), was isolated in 20%
yield with evolution of propylene (28%). The 31P{1H}
NMR spectrum of 4 showed an AM2X pattern at -13.8
(td, J ) 24, 13 Hz, 1P), -0.96 (dd, J ) 32, 24 Hz, 2P),
and 10.7 ppm (td, J ) 32, 13 Hz, 1P), indicating two
trans and two cis PMe3 ligands in an octahedral
(13) Crystallographic data for 2: monoclinic, P21/c (No. 14), a )
15.706(4) Å, b ) 9.197(4) Å, c ) 16.570(3) Å, â ) 109.27(2)°, V ) 2259-
(1) Å3, Z ) 4, Dcalcd ) 1.362 g cm-3, T ) 293 K, 5561 unique reflections,
2946 with I > 3σ(I), R (Rw) ) 0.043 (0.030).
(14) Yamamoto, A. Adv. Organomet. Chem. 1992, 34, 111 and
references therein.
1
geometry. The H NMR spectrum showed three mag-

Communications
Organometallics, Vol. 17, No. 4, 1998 503
and two inequivalent phosphorus atoms that acciden-
tally have similar coupling constants, while the ortho
methyl group appears as a singlet at 2.53 ppm.
The oxaruthenacycle 4 may be formed via an (η3-
allyl)(aryloxo)ruthenium(II) intermediate. It is likely
that this reaction involves oxidative addition of the C-H
bond of the ortho methyl group, followed by reductive
elimination of the allyl and the hydrido ligands, or direct
hydrogen abstraction by the allyl moiety. In either case,
the allyl ligand acts as an acceptor of the methyl’s
hydrogen. No trace of signals assignable to the proposed
intermediate could be detected during the reaction by
NMR, from which we conclude that once the O-C bond
is cleaved, the sp3 C-H reacts rapidly.
Complex 4 can also be obtained in 14% yield by the
reaction of 1 with 2,6-xylenol in the presence of PMe3
at 70 °C for 2 days. An NMR study revealed that this
reaction initially gave fac-Ru((6-η1):(1-3-η3)-C8H10)-
(PMe3)3 (5;15 36%), followed by formation of 4 (30%) with
liberation of 1,3-COD (34%). Accordingly, the yield of
4 was improved to 91%, when the isolated 5 was used
as the starting complex. Thus, complex 5 is an inter-
mediate in this reaction, with the allyl moiety in 5
behaving as a hydrogen acceptor in the C-H bond
activation process.
F igu r e 2. ORTEP drawing of 6b. All hydrogen atoms are
omitted for clarity. Bond distances and angles for 6b are
included in the Supporting Information.
between acyl and alkoxo/aryloxo groups is well docu-
mented.18 This reaction represents the transformation
of 2-allylphenol to benzopyran via sp3 C-H bond activa-
tion. Investigations of the reaction mechanism and
possible catalytic applications in organic synthesis are
in progress.
When 2-allylphenol was reacted with 5, the oxaruth-
enacycle Ru[OC6H4(o-η3-C3H4)](PMe3)3 (6a ) was isolated
in 11% yield. Similarly, treatment of 2-allylphenol with
1/PEt3 gave the PEt3 analogue 6b in 39% yield, the
structure of which is shown in Figure 2.16 Generation
of hydrogen was not observed by Toepler pump during
the reaction. NMR studies suggest that the reaction
goes to completion in over 38 h at 50 °C, with generation
of free 1,5-COD (86%) and 1,3-COD (82%). These facts
suggest that hydrogen atoms from the hydroxy and the
allyl groups in 2-allylphenol are used for the hydrogena-
tion of 1,3,5-COT to 1,3-COD.
An interesting feature of the oxaruthenacycle 6b is
the iodine-induced reductive elimination to give 2H-
benzopyran in 37% yield under ambient conditions.17
Such C-O bond formation mediated by transition
metals is quite rare, although reductive elimination
Ack n ow led gm en t. This work was financially sup-
ported by a Grant-in-Aid for Scientific Research from
the Ministry of Education, Science, Sports and Culture
of J apan and the Proposed-Based New Industry Cre-
ative Type Technology R&D Promotion Program from
the New Energy and Industrial Technology Develop-
ment Organization (NEDO) of J apan.
Su p p or tin g In for m a tion Ava ila ble: Text giving experi-
mental details and full characterization data, tables giving
X-ray crystallographic data, and ORTEP diagrams for Ru-
(OPh)(η3-C3H5)(PMe3)3 (2) and Ru[OC6H4(o-η3-C3H4)](PEt3)3
(6b) (24 pages). Ordering information is given on any current
masthead page.
OM970911Q
(15) Hirano, M.; Marumo, T.; Miyasaka, T.; Fukuoka, A.; Komiya,
S. Chem. Lett. 1997, 297.
(16) Crystallographic data for 6b: monoclinic, P21/n (No. 14), a )
14.171(5) Å, b ) 12.179(3) Å, c ) 17.778(4) Å, â ) 100.00(3)°, V ) 3021-
(1) Å3, Z ) 4, Dcalcd ) 1.292 g cm-3, T ) 293 K, 4307 unique reflections,
2858 with I > 3σ(I), R (Rw) ) 0.046 (0.041).
(17) 2H-Benzopyran was identified by comparison with an authentic
sample derived from 4-chromanone: Parham, W. E.; Huestis, L. D. J .
Am. Chem. Soc. 1962, 84, 813.
(18) (a) Komiya, S.; Akai, Y.; Tanaka, K.; Yamamoto, A. Organo-
metallics 1985, 4, 1130. (b) Sano, K.; Yamamoto, T.; Yamamoto, A. Z.
Naturforsch. 1985, 40B, 210. (c) Palucki, M.; Wolfe, J . P.; Buchwald,
S. L. J . Am. Chem. Soc. 1996, 118, 10333. (d) Mann, G.; Hartwig, J . F.
J . Am. Chem. Soc. 1996, 118, 13109. (e) Widenhoefer, R. A.; Zhong,
H. A.; Buchwald, S. L. J . Am. Chem. Soc. 1997, 119, 6787 and
references therein.