Naphthalene formation by allylation of zirconaindenes in the ZnX2-Pd(PPh3)4 system

Article abstract of DOI:10.1039/b103674m

Zirconaindenes reacted with allyl halides in the presence of ZnX₂ (X = Cl or Br) and a catalytic amount of Pd(Pph₃)₄ to give naphthalene derives in good yield.

Full text of DOI:10.1039/b103674m

Naphthalene formation by allylation of zirconaindenes in the
ZnX –Pd(PPh ) system
2
3 4
a
b
a
Zheng Duan, Kiyohiko Nakajima and Tamotsu Takahashi*
a
Catalysis Research Center and Graduate School of Pharmaceutical Sciences, Hokkaido University, and
CREST, Science and Technology Corporation (JST), Sapporo 060-0811, Japan.
E-mail: tamotsu@cat.hokudai.ac.jp
b
Department of Chemistry, Aichi University of Education, Igaya, Aichi 448-8542, Japan
Received (in Cambridge, UK) 24th April 2001, Accepted 10th July 2001
First published as an Advance Article on the web 16th August 2001
Zirconaindenes reacted with allyl halides in the presence of
ZnX ( X = Cl or Br) and a catalytic amount of Pd(PPh to
give naphthalene derivatives in good yield.
Table 1 The formation of naphthalene derivatives
2
3 4
)
Zirconacyclopentadienes
Product
Yield (%)a
It has been believed for a long time that zirconacyclopenta-
dienes are inert toward C–C bond formation reactions. Re-
cently, we found that transmetalation reactions of zirconacyclo-
1
2
3
pentadienes to copper, nickel and lithium could open a way
85(59)
61(42)
68(40)
to various carbon–carbon bond formation reactions. In this
paper we would like to report the novel naphthalene formation
reaction of zirconaindenes in the presence of ZnX
3 4
catalytic amount of Pd(PPh ) .
4
2
and a
5
When we investigated novel transmetalation to Zn, we tried
the allylation reaction of zirconacyclopentadienes, since double
1
allylation of zirconacyclopentadienes proceeded in the pres-
ence of either a catalytic or stoichiometric amount of CuCl.1
79(47)
1.9+1
When only the zinc salts were used, the reactions were very
sluggish. However in the presence of a catalytic amount of
3 4
Pd(PPh ) the reaction dramatically changed. Monoallylation
products were clearly formed. The formation of double
allylation products was not observed [eqn. (1)].
(1)
7
3
7(51)
+1
This is in sharp contrast to the allylation in the presence of
1
CuCl. Then our attention was turned to the allylation reaction
of zirconaindenes. It is interesting to note that, when zircona-
6
indene 3a was used, substituted naphthalene 4a was clearly
a
GC yields. Isolated yields are given in parentheses.
formed as a single product [eqn. (2)].† The formation of
of the carbon in the –CNC group attached to Zr was enhanced by
introducing alkyl groups such as the Et group and the Pr group
instead of the Ph groups, carbon–carbon bond formation with
allyl halides at the –C(R)NC(R), R = Et or Pr, was observed.
The isomers 5d and 5e were obtained in the case of 3d and 3e,
respectively.
A possible mechanism of the naphthalene formation involves
(i) transmetalation of the Zr-phenyl carbon bond to Zn giving 6,
(ii) transmetalation of 6 with an allylpalladium halide formed by
oxidative addition of allyl halide to a Pd0 complex, (iii)
reductive elimination to give allylated intermediate 7, (iv)
transmetalation of the second Zr–C bonds to Pd forming 8, (v)
insertion of the vinyl group into the Pd–C bond (vi) b-hydrogen
elimination to give exo-methylene derivative 10 that isomerizes
to the corresponding naphthalene 4 (Scheme 1).
(
2)
regioisomer 5a was not observed. The use of only a catalytic
amount of Pd(PPh without zinc salt did not give a clean
3
)
4
reaction, although 4a was formed in 33% GC yield.
The structure of the compound 4a was confirmed by X-ray
analysis.‡ It clearly shows that the allylation reaction proceeded
selectively at the benzene-carbon attached to Zr. When
6 4 6 4
MeOC H - and MeC H - were used as substituents instead of
the Ph group, the similar perfect regiocontrol was observed as
shown in Table 1. This perfect regioselectivity is attributed to
the high reactivity of the benzene-carbon attached to Zr
compared with the carbon of the –C(Ph)NC(Ph) group attached
to Zr. It is interesting to note that when the nucleophilic property
Further investigations on mechanism and selectivity are
currently in progress.
1672
Chem. Commun., 2001, 1672–1673
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b103674m

‡
Crystallographic data of 4a: colorless prisms, monoclinic, space group
C2/c, a = 21.312(1), b = 10.6981(6), c = 16.2781(8) Å, b = 117.713(4)°,
Z = 8, R = 0.044, GOF = 1.84. CCDC 165561. See http://www.rsc.org/
suppdata/cc/b1/b103674m/ for crystallographic files in .cif or other
electronic format.
1
2
3
4
5
T. Takahashi, M. Kotora, K. Kasai and N. Suzuki, Organometallics,
994, 13, 4183.
T. Takahashi, F.-Y. Tsai, Y. Li., K. Nakajima and M. Kotora, J. Am.
Chem. Soc., 1999, 121, 11093.
T. Takahashi, S. Q. Huo, R. Hara, Y. Noguchi, K. Nakajima and W.-H.
Sun, J. Am. Chem. Soc., 1999, 121, 1094.
For a recent review of naphthalene formation from benzyne complexes,
see M. A. Bennett and E. Wenger, Chem. Ber.,1997, 130, 1029.
For recent examples of naphthalene formation using transition metal
compounds, see D. Peña, D. Pérez, E. Guitián and L. Castedo, J. Am.
Chem. Soc., 1999, 121, 5827; E. Yoshikawa and Y. Yamamoto, Angew.
Chem., Int. Ed., 2000, 39, 173; E. Yoshikawa, K. V. Radhakrishnan and
Y. Yamamoto, J. Am. Chem. Soc., 2000, 122, 7280; T. Takahashi, R.
Hara, Y. Nishihara and M. Kotora, J. Am. Chem. Soc., 1996, 118, 5154;
T. Takahashi, Z. F. Xi, A. Yamazaki, Y. H. Liu, K. Nakajima and M.
Kotora, J. Am. Chem. Soc., 1998, 120, 1672; R. C. Larock, M. J. Doty,
Q. P. Tian and J. M. Zenner, J. Org. Chem., 1997, 62, 7536; N. Iwasawa,
M. Shido, K. Maeyama and H. Kusama, J. Am. Chem. Soc., 2000, 122,
1
Scheme 1
1
0226.
Notes and references
6
For transmetalation of acyclic organozirconium to Zn, see E. Negishi,
D. E. Van Horn, T. Yoshida and C. L. Rand, Organometallics, 1983, 2,
563.
†
Typical procedure: to zirconaindene 3a prepared according to the
literature were added 2 eq. of ZnBr , a catalytic amount of Pd(PPh (5
2
3 4
)
mol%) and 2 eq. allyl bromide. The mixture was stirred at 50 °C for 12 h.
Only 4a was formed in 85% GC yield. After isolation and purification by
column chromatography, 4a was obtained in 59% isolated yield.
7 G. Erker, J. Organomet. Chem., 1977, 134, 189; K. Kropp and G. Erker,
Organometallics, 1982, 1, 1246; S. L. Buchwald and B. T. Watson, J. Am.
Chem. Soc., 1986, 108, 7411.
Chem. Commun., 2001, 1672–1673
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