C O M M U N I C A T I O N S
Figure 3. Intramolecular trapping of isobenzofurans.
Figure 2. Three-component coupling of aromatic ketimine, aldehyde, and
cyclooctene.
the aldehyde, intramolecular nucleophilic cyclization, reductive
elimination, and elimination of aniline. It is interesting to note that
the carbon-rhenium bonds show nucleophilicity which is a
characteristic property of early transition metals and that the rhenium
complex can be used as a catalyst via reductive elimination which
is usually observed for late transition metals.
Scheme 1
Acknowledgment. Financial support by a Grant-in-Aid for
Scientific Research on Priority Areas (No. 18037049, “Advanced
Molecular Transformations of Carbon Resources”) from the
Ministry of Education, Culture, Sports, Science, and Technology
of Japan and for Young Scientists (B) (No. 18750088) from the
Japan Society for the Promotion of Science is acknowledged.
Supporting Information Available: General experimental proce-
dure and characterization data for isobenzofuran derivatives and Diels-
Alder adducts. This material is available free of charge via the Internet
elimination of aniline. Because the formed aniline reacts with the
aldehyde, 2 equiv of the aldehyde is necessary to complete the
reaction.
References
(1) (a) Kakiuchi, F.; Murai, S. Top. Organomet. Chem. 1999, 3, 47. (b) Guari,
Y.; Sabo-Etiienne, S.; Chaudret, B. Eur. J. Inorg. Chem. 1999, 1047. (c)
Dyker, G. Angew. Chem., Int. Ed. 1999, 38, 1699. (d) Ritleng, V.; Sirlin,
C.; Pfeffer, M. Chem. ReV. 2002, 102, 1731.
(2) (a) Tan, K. L.; Bergman, R. G.; Ellman, J. A. J. Am. Chem. Soc. 2002,
124, 13964. (b) Lim, S.-G.; Ahn, J.-A.; Jun, C.-H. Org. Lett. 2004, 6,
4687. (c) Kuninobu, Y.; Nishina, Y.; Shouho, M.; Takai, K. Angew. Chem.,
Int. Ed. 2006, 45, 2766.
Isobenzofuran derivatives are useful compounds as building
blocks of bioactive compounds8 and functional materials.5c,9 In
addition, they have reactive diene moieties, and these can be used
for Diels-Alder reactions.10 In fact, when a reaction of ketimine
1a and benzaldehyde (2a) was conducted in the presence of
cyclooctene, a three-component coupling product 4a derived from
the Diels-Alder reaction of 3a and cyclooctene was produced in
83% yield in one pot (Figure 2). Isobenzofuran derivatives having
an alkenyl or an alkyl group which are readily oxidized by
atmospheric oxygen could also be trapped with cyclooctene in one
pot under an argon atmosphere. The corresponding adducts 4b and
4g were obtained in 69% and 79% yields, respectively, as stable
forms (Figure 2). The formed Diels-Alder adducts 4a, 4b, and 4g
were aromatized6d,8d,10 without isolation via the ring-opening
reaction of cyclic ether and the elimination of water by treatment
with acetic acid and sulfuric acid at 25 °C for 1.5 h.11 The reaction
produced the corresponding naphthalene derivatives 5a, 5b, and
5g in 73%, 67%, and 79% yields, respectively (Figure 2).
An aliphatic aldehyde, 5-hexenal, could be used as the aldehyde
component of the isobenzofuran formation (Figure 3, route A). In
addition, a ketimine which can isomerize to an enamine could be
employed (route B). Because the formed isobenzofuran was
unstable, it was trapped in situ by an intramolecular Diels-Alder
reaction. After acidic treatment, routes A and B produced a
naphthalene derivative 5h in 50% and 75% yields, respectively
(Figure 3).
(3) Kuninobu, Y.; Kawata, A.; Takai, K. J. Am. Chem. Soc. 2005, 127, 13498.
(4) Kuninobu, Y.; Tokunaga, Y.; Kawata, A.; Takai, K. J. Am. Chem. Soc.
2006, 128, 202.
(5) For the previous synthesis of isobenzofuran derivatives, see: (a) Cava,
M. P.; Mitchell, M. J.; Deana, A. A. J. Org. Chem. 1960, 25, 1481. (b)
Naito, K.; Rickborn, B. J. Org. Chem. 1980, 45, 4061. (c) Sharp, J. T.;
Skinner, C. E. D. Tetrahedron Lett. 1986, 27, 869. (d) Dodge, J. A.; Bain,
J. D.; Chamberlin, A. R. J. Org. Chem. 1990, 55, 4190. (e) Chan, S. H.;
Yick, C. Y.; Wong, H. N. C. Tetrahedron 2002, 58, 9413.
(6) Because isobenzofuran derivatives are readily oxidized by atmospheric
oxygen, the elemental analyses were performed with the corresponding
Diels-Alder adducts of cyclooctene.
(7) Wrrenner, R. N.; Shang, M.; Butler, D. N. Chem. Commun. 2001, 1550.
(8) (a) Pichon, N.; Harrison-Marchard, A.; Mailliet, P.; Maddaluno, J. J. Org.
Chem. 2004, 69, 7220. (b) Myers, A. G.; Tom, N. J.; Fraley, M. E.; Cohen,
S. B.; Madar, D. J. J. Am. Chem. Soc. 1997, 119, 6072. (c) Berkowitz, D.
B.; Choi, S.; Maeng, J.-H. J. Org. Chem. 2000, 65, 847. (d) Sutherland,
H. S.; Higgs, K. C.; Taylor, N. J.; Rodrigo, R. Tetrahedron 2001, 57,
309.
(9) (a) Maindron, T.; Dodelet, J. P.; Lu, J.; Hlil, A. R.; Hay, A. S.; D’Iorio,
M. Synth. Met. 2002, 130, 247. (b) For a quencher of singlet oxygen:
Nishide, N.; Miyoshi, N. Life Sci. 2002, 72, 321. (c) For green EL
devices: Li, J. Y.; Hong, Z. R.; Wang, P. F.; Lee, C. S.; Wong, N. B.;
Kwong, H. L.; Lee, S. T. Thin Solid Films 2004, 446, 111.
(10) For the Diels-Alder reactions of isobenzofuran derivatives, see: (a) Wittig,
G.; Krebs, A. Chem. Ber. 1961, 94, 3260. (b) Sasaki, T.; Kanematsu, K.;
Hayakawa, K.; Sugiura, M. J. Am. Chem. Soc. 1975, 97, 355. (c)
Christopfel, W. C.; Miller, L. L. J. Org. Chem. 1986, 51, 4169. (d) Binger,
P.; Wedemann, P.; Goddard, R.; Brinker, U. H. J. Org. Chem. 1996, 61,
6462. (e) Ernet, T.; Maulitz, A. H.; Wurthwein, E.-U.; Haufe, G. J. Chem.
Soc., Perkin Trans. 1 2001, 1929. (f) Mikami, K.; Ohkuma, H. Org. Lett.
2002, 4, 3355. (g) Luo, Y.; Herndon, J. W. Organometallics 2005, 24,
3099.
In summary, we have succeeded in the insertion of aldehydes
into a C-H bond of aromatic ketimines by using a rhenium
complex, [ReBr(CO)3(thf)]2, as a catalyst. The reactions provide
isobenzofuran derivatives via C-H bond activation, insertion of
(11) Jayanth, T. T.; Jeganmohan, M.; Cheng, C.-H. J. Org. Chem. 2004, 69,
8445.
JA065643E
9
J. AM. CHEM. SOC. VOL. 128, NO. 38, 2006 12377