Benzidine rearrangement reactions of polyether tethered cyclic N,N′-Diaryl hydrazides

Article abstract of DOI:10.1021/ol071320r

N,N′-Diaryl hydrazides tethered with a polyether group at the meta positions undergo [5,5]-sigmatropic (benzidine) rearrangement reactions to furnish 4,4′-diamino-biphenyls (benzidines) strapped with a polyether unit at the 2,2′-positions.

Full text of DOI:10.1021/ol071320r

ORGANIC
LETTERS
2007
Vol. 9, No. 16
3185-3186
Benzidine Rearrangement Reactions of
Polyether Tethered Cyclic N,N
′-Diaryl
Hydrazides
Hee-Yeon Kim, Woo-Jin Lee, Hong-Min Kang, and Cheon-Gyu Cho*
Department of Chemistry, Hanyang UniVersity, Seoul, Korea 133-791
ccho@hanyang.ac.kr
Received June 4, 2007
ABSTRACT
N,N
furnish 4,4
′
-Diaryl hydrazides tethered with a polyether group at the meta positions undergo [5,5]-sigmatropic (benzidine) rearrangement reactions to
-diamino-biphenyls (benzidines) strapped with a polyether unit at the 2,2 -positions.
′
′
The acid-catalyzed [5,5]-sigmatropic rearrangement of hy-
drazobenzenes, conventionally known as the benzidine
rearrangement,1 affords 4,4′-diamino biaryls (benzidines),
useful synthetic building blocks for azo dyes, polyaromatics,
polyimides, and polyfluorenes.2 In addition, their N-arylation
products are important hole transporting materials for light-
emitting display devices.3 However, the conventional ben-
zidine rearrangement reaction itself has little synthetic value
because of the formation of inseparable isomeric byproducts4
as well as the lack of general synthetic methods for the
starting hydrazobenzenes.5
We have recently demonstrated that N,N′-diaryl hydrazides
undergo acid-catalyzed [3,3]- and [5,5]-sigmatropic rear-
rangement reactions to afford 2,2′-diamino-1,1′-biaryls and
4,4′-diamino-1,1′-biaryls (benzidines), respectively.6 More
importantly, N,N′-diaryl hydrazides are much more readily
accessed than N,N′-diaryl hydrazines (hydrazobenzenes), by
means of the Pd- or Cu(I)-catalyzed coupling reactions of
N-aryl hydrazides with aryl halides.6,7
Benzidines incorporating alkyl, polyether, or polyaza
chains are versatile chemical motifs, easily convertible into
biphenyl-based cyclophanes8 by various synthetic methods
(1) (a) Hoffman, A. W. Proc. R. Soc. London 1863, 12, 576. (b) Dewar,
M. J. S. In Molecular Rearrangement; de Mayo, P., Ed.; Interscience: New
York, 1969; Vol 1, p 323. (c) Banthorpe, D. V. Chem. ReV. 1970, 70, 295.
(d) Olah, G. A.; Dunne, K.; Kelly, D. P.; Mo, Y. K. J. Am. Chem. Soc.
1972, 94, 7438. (e) Cox, R. A.; Buncel, E. In The Chemistry of the Hydrazo,
Azo, and Azoxy Groups; Patai, S., Ed.; Wiley: New York, 1975; p 775. (f)
Bunton, C. A.; Rubin, R. J. J. Am. Chem. Soc. 1976, 98, 4236. (g) Shine,
H. J.; Kupczyk-Subotkowska, L.; Subotkowski, W. J. Am. Chem. Soc. 1985,
107, 6674. (h) Park, K. H.; Kang, J. S. J. Org. Chem. 1997, 62, 3794. (i)
Park, K. H.; Park, M.-K.; Cho, Y. H. Bull. Korean Chem. Soc. 1998, 19,
1090.
(2) (a) Chen, R.-F.; Fan, Q.-L.; Zheng, C.; Huang, W. Org. Lett. 2006,
8, 203. (b) Chan, K. L.; McKiernan, M. J.; Towns, C. R.; Holmes, A. B. J.
Am. Chem. Soc. 2005, 127 (21), 7662.
(3) (a) Popovic, Z. D.; Aziz, H. J. Appl. Phys. 2005, 98, 13510. (b) Tung,
C.-H.; Zhang, L.-P.; Li, Y.; Cao, H.; Tanimoto, Y. J. Am. Chem. Soc. 1997,
119, 5348.
(5) They are generally prepared from nitroarenes via the reductive
coupling reaction with NaBH4 or from azobenzenes through a Zn-mediated
reduction process that are moderately effective only for symmetric hydra-
zobenzenes.
(6) (a) Kang, H.-M.; Lim, Y.-K.; Shin, I.-J.; Kim, H.-Y.; Cho, C.-G.
Org. Lett. 2006, 8, 2047. (b) Lim, Y. K.; Jung, J. W.; Lee, H.; Cho, C.-G.
J. Org. Chem. 2004, 69, 5778.
(7) (a) Peters, M. V.; Goddard, R.; Hecht, S. J. Org. Chem. 2006, 71,
7846. (b) Peters, M. V.; Stoll, R. S.; Goddard, R.; Buth, G.; Hecht, S. J.
Org. Chem. 2006, 71, 7840. (c) Lim, Y.-K.; Choi, S.; Park, K. B.; Cho,
C.-G. J. Org. Chem. 2004, 69, 2603. (d) Kim, K.-Y.; Shin, J.-T.; Lee, K.-
S.; Cho, C.-G. Tetrahedron Lett. 2004, 45, 117. (e) Lim, Y.-K.; Pang, S.-
J.; Paik, S. U.; Cho, C.-G. Bull. Korean Chem. Soc. 2003, 24, 543. (f) Lim,
Y.-K.; Lee, K.-S.; Cho, C.-G. Org. Lett. 2003, 5, 979. (g) Lee, K.-S.; Lim,
Y.-K.; Cho, C.-G. Tetrahedron Lett. 2002, 43, 7463.
(8) (a) Shishkina, S. V.; Shishkin, O. V.; Grygorash, R. Y.; Mazepa, A.
V.; Rakipov, I. M.; Yakshin, V. V.; Kotlyar, S. A.; Kamalov, G. L. J. Mol.
Struct. 2007, 832, 199. (b) Burguete, M. I.; Diaz, P.; Garc´ıa-Espan˜a, E.;
Luis, S. V.; Miravet, J. F.; Querol, M.; Ramirez, J. A. Chem. Commun.
1999, 649. (c) Artz, S. P.; Cram, D. J. J. Am. Chem. Soc. 1984, 106, 2160.
(d) Rebek, J. Acc. Chem. Res. 1984, 17, 258.
(4) (a) Cheng, J. D.; Shine, H. J. J. Org. Chem. 1975, 40, 703. (b) Zhu-
Ohlbach, A.; Gleiter, R.; Bleiter, R.; Schmidt, H. L.; Reda, T. Eur. J. Org.
Chem. 1998, 11, 2409. (c) Buncel, E. Can. J. Chem. 2000, 78, 1251. (d)
Feiring, A. E.; Auman, B. C.; Wonchoba, E. R. Macromolecules 1993, 26,
2779. (b) Shine, H. J.; Trisler, J. C. J. Am. Chem. Soc. 1960, 82, 4054.
10.1021/ol071320r CCC: $37.00
© 2007 American Chemical Society
Published on Web 07/07/2007

including the Sandmeyer reaction. Benniston and co-workers
investigated the synthesis of 4,4′-diamino-biphenyl 5 tethered
with alkyl or alkoxy linkers from bis(m-nitrophenyl) ether 3
via a reaction sequence consisting of a Zn-mediated partial
reduction and in situ acid-catalyzed benzidine rearrange-
ment.9 Unfortunately, the reaction did not proceed to give
the desired benzidine rearrangement product 5, but instead
4, resulting from the [3,3]-sigmatropic rearrangement in an
overall yield of 16% (Scheme 1). Evidently, the rearrange-
Scheme 2. Synthesis of Polyether Tethered Cyclic Benzidines
Scheme 1
chromatography was unsuccessful, because of the interfer-
ence of unidentified decomposed byproducts. Full charac-
terizations were made upon acetylation to the acetamides
12a-c, which were separated in analytically pure form in
all cases. The structural integrity of 11a-c was further
corroborated by the conversion of 11a to the known diiodide
13a10 via the standard Sandmeyer protocol.
In summary, we have demonstrated that N,N′-diaryl
hydrazides strapped with a polyether chain can undergo the
benzidine rearrangement reaction to give the corresponding
4,4′-diamino-2,2′-biphenyls with a polyether unit at the 3,3′-
positions.
ment reaction took place at the sites B, rather than A, of the
putative hydrazobenzene intermediate 7.
The potential importance as synthetic intermediates to a
diverse array of polyether cyclophanes together with this
reported failure led us to investigate the benzidine rearrange-
ment reactions of cyclic N,N′-diaryl hydrazides strapped with
a polyether chain. Scheme 2 shows our synthesis which
commenced with the preparation of 8 from m-bromophenol
and polyether bistosylates. The Cu(I)-catalyzed coupling
reactions of bis(m-bromophenyl) ethers 8a-c provided
monohydrazides 9a-c in 53-57% yields (82-85% based
on recovered starting bromide 8a-c). Their cyclization
reactions under Pd catalysis furnished diaryl hydrazides
10a-c in 46-50% yields, setting the stage for the ensuing
benzidine rearrangement reactions. When heated in EtOH
with a catalytic amount of aq. HCl, hydrazides 10a-c were
found to undergo rearrangement reactions to the correspond-
Acknowledgment. Financial support was provided by a
grant of the Korean Science and Technology Foundation
(KOSEF, R01-2006-000-11283-0). K.H.Y., L.W.J., and
K.H.M. thank the BK21 fellowship.
Supporting Information Available: Experimental pro-
cedures and compound characterizations for benzidine ac-
etamides 12a-c. This material is available free of charge
via the Internet at http://pubs.acs.org.
1
ing benzidines 11a-c as indicated by their crude H NMR
OL071320R
spectra. However, their purification by silica-gel column
(10) (a) Benniston, A. C.; Harriman, A.; Li, P.; Patel, P. V.; Sams, C.
A. J. Org. Chem. 2006, 71, 3481. (b) Benniston, A. C.; Li, P.; Sams, C.
Tetrahedron Lett. 2003, 44, 3947.
(9) Benniston, A. C.; Clegg, W.; Harriman, A.; Harrington, R. W.; Li,
P.; Sams, C. Tetrahedron Lett. 2003, 44, 2665.
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Org. Lett., Vol. 9, No. 16, 2007