The C-C bond activation and skeletal rearrangement of cycloalkanone imine by Rh(I) catalysts [10]

Full text of DOI:10.1021/ja0033537

J. Am. Chem. Soc. 2001, 123, 751-752
751
Table 1. C-C Bond Activation of Ketimine 1 with 2 by 3 and
The C-C Bond Activation and Skeletal
Rearrangement of Cycloalkanone Imine by Rh(I)
Catalysts
Cy3P
ratio of 4:5
overall
entry
reactant 1 (n)
product(s)
(ter:int of 4)a
yield,b %
Chul-Ho Jun,* Hyuk Lee, and Sung-Gon Lim
1
2
3
4
5
6
7
1a (n ) 0)
1b (n ) 1)
1c (n ) 2)
1d (n ) 3)
1e (n ) 5)
1f (n ) 7)
1g (n ) 10)
5
5
0:100
0:100
23:77 (52:48)
39:61 (13:87)
38:62 (15:85)
39:61 (22:78)
37:63 (16:84)
9
5
76
89
83
86
79
Department of Chemistry, Yonsei UniVersity
4c + 5
4d + 5
4e + 5
4f + 5
4g + 5
Seoul 120-749, Korea
ReceiVed September 12, 2000
The activation of the carbon-carbon bond by homogeneous
catalysts is of current interest in organometallic chemistry.1
However, a few examples of the homogeneous catalytic activation
of the C-C bond by transition metal have been reported:2-9 the
decarbonylative cleavage of the C-C bond,3 the â-alkyl elimina-
tion of the homoallyl alcohol,4 the â-decarboxylative ring opening
of cyclic carbonate,5 the ring cleavage of tert-cyclobutanol,6 and
so on. Especially, ring-cleavages of cycloalkanones by transition
metal catalyst have been limited to strained cyclic ketones such
as cyclopropenone,7 cyclobutenone,8 and cyclobutanones9 to take
advantage of the release of the ring strain. On the other hand,
catalytic C-C bond cleavages of large unstrained ring-sized
cycloalkanones are rare. We recently reported on the new catalytic
C-C bond activation of unstrained ketone compounds.10 In this
report, we wish to describe the ring-opening of an unstrained
cycloalkanone imine and its skeletal rearrangement.
a The ratio of terminal olefin and internal olefin of 4 was determined
by GCD. b Yields are determined by GCD.
Alkenyl ketone 4, consisting of terminal and internal olefins,13
can be hydrogenated by 1 atm of H2 on Pd/C to give saturated
alkyl ketone 6. Initially, the C-C bond in ketimine 1 is cleaved
by rhodium(I) in 3 to give an (iminoacyl) rhodium(III) metalla-
cyclic complex 7, followed by â-hydrogen elimination to effect
rhodium(III) hydride 8 (Scheme 1). In the presence of 2, the olefin
Scheme 1
The reaction of cycloalkanoketimine 1, prepared from cycloal-
kanone and 2-amino-3-picoline,11 with 1-hexene (2, 1000 mol %
based on 1) was carried out in the presence of [(C8H14)2RhCl]2
(3, 3 mol % based on 1) and Cy3P (6 mol %) to yield a mixture
of the ring-opened alkenyl ketones 4 and 7-tridecanone (5) after
hydrolysis (eq 1).12
exchange of the ω-alkenyl group of 8 with 2 affords 9. A hydride
insertion in 9 and a reductive elimination of the resulting complex
10 produces 11. Ketimines 11 undergo a further C-C bond
activation to yield the symmetric dialkyl ketimine 12.14 The
hydrolysis of 11 and 12 affords the corresponding ketones 4 and
5.
As the size of the ring from cyclohexanoketimine to cyclo-
heptanoketimine increases, the yields of the C-C bond cleaved
products dramatically increase (Table 1). In case of cyclopen-
tanoketimine 1a and cyclohexanoketimine 1b, small amounts (5-
9% yields) of the C-C bond cleaved products were determined
(Table 1, entries 1-2), while moderate yields (76-89%) of the
C-C bond cleaved products were obtained in the reaction of
cycloalkanoketimine larger than 1b (entries 3-7). The reason
(1) For reviews, see: (a) Rybtchinski, B.; Milstein, D. Angew. Chem., Int.
Ed. 1999, 38, 870. (b) Jennings, P. W.; Johnson, L. L. Chem. ReV. 1994, 94,
2241. (c) Crabtree, R. H. Chem. ReV. 1985, 85, 245. (d) Murakami, M.; Ito,
Y. In ActiVation of UnreactiVe Bonds and Organic Synthesis; Murai, S. Ed.;
Springer: Berlin, 1999; pp 97-129.
(2) (a) Mitsudo, T.-a.; Suzuki, T.; Zhang, S.-W.; Imai, D.; Fujita, K.-i.;
Manabe, T.; Shiotsuki, M.; Watanabe, Y.; Wada, K.; Kondo, T. J. Am. Chem.
Soc. 1999, 121, 1839. (b) Liou, S.-Y.; van der Boom, M. E.; Milstein, D.
Chem. Commun. 1998, 687. (c) Edelbach, B. L.; Lachicotte, R. J.; Jones, W.
D. J. Am. Chem. Soc. 1998, 120, 2843. (d) Lin, M.; Hogan, T.; Sen, A. J.
Am. Chem. Soc. 1997, 119, 6048. (e) Perthuisot, C.; Jones, W. D. J. Am.
Chem. Soc. 1994, 116, 3647. (f) Bunel, E.; Burger, B. J.; Bercaw, J. E. J.
Am. Chem. Soc. 1988, 110, 976. (g) Watson, P. L.; Roe, D. C. J. Am. Chem.
Soc. 1982, 104, 6471. (h) Golden, H. J.; Baker, D. J.; Miller, R. G. J. Am.
Chem. Soc. 1974, 96, 4235.
(3) Chatani, N.; Ie, Y.; Kakiuchi, F.; Murai, S. J. Am. Chem. Soc. 1999,
121, 8645.
(4) Kondo, T.; Kodoi, K.; Nishinaga, E.; Okada, T.; Morisaki, Y.;
Watanabe, Y.; Mitsudo, T. J. Am. Chem. Soc. 1998, 120, 5587.
(5) Harayama, H.; Kuroki, T.; Kimura, M.; Tanaka, S.; Tamaru, Y. Angew.
Chem., Int. Ed. Engl. 1997, 36, 2352.
(6) (a) Nishimura, T.; Uemura, S. J. Am. Chem. Soc. 1999, 121, 11010.
(b) Nishimura, T.; Ohe, K.; Uemura, S. J. Am. Chem. Soc. 1999, 121, 2645.
(7) Baba, A.; Ohshiro, Y.; Agawa, T. J. Organomet. Chem. 1976, 110,
121.
(8) (a) Huffman, M. A.; Liebeskind, L. S. J. Am. Chem. Soc. 1993, 115,
4895. (b) Huffman, M. A.; Liebeskind, L. S. J. Am. Chem. Soc. 1991, 113,
2771.
(9) (a) Murakami, M.; Amii, H.; Ito, Y. Nature 1994, 370, 540. (b)
Murakami, M.; Amii, H.; Shigeto, K.; Ito, Y. J. Am. Chem. Soc. 1996, 118,
8285. (c) Murakami, M.; Takahashi, K.; Amii, H.; Ito, Y. J. Am. Chem. Soc.
1997, 119, 9307. (d) Murakami, M.; Itahashi, T.; Amii, H.; Takahashi, K.;
Ito, Y. J. Am. Chem. Soc. 1998, 120, 9949. (e) Murakami, M.; Tsuruta, T.;
Ito, Y. Angew. Chem., Int. Ed. 2000, 39, 2484.
(10) Jun, C.-H.; Lee, H. J. Am. Chem. Soc. 1999, 121, 880.
(11) Cycloalkanoketimine was prepared by the reaction of cycloalkanone
and N-lithium-2-amino-3-picoline, generated from 2-amino-3-picoline and
n-BuLi in THF. See Supporting Information.
(12) In the C-C bond cleavage of ketimine, the catalyst 3 and Cy3P shows
the best catalytic activity among organotransition metal catalysts. Various
olefins could be applied to this C-C bond activation reaction, and 1-hexene
(2) was selected as a standard olefin.
(13) When the reaction of 1c and 2 was carried out at 150 °C for 1 h
under (PPh3)3RhCl (3 mol %), 4c bearing an exclusive terminal alkenyl group
was obtained in a 13% yield along with 5 (5%). This result implies that the
initial terminal olefin in ketimine is isomerized to internal olefin.
(14) Jun, C.-H.; Lee, H.; Park. J.-B.; Lee, D.-Y. Org. Lett. 1999, 1, 2161.
10.1021/ja0033537 CCC: $20.00 © 2001 American Chemical Society
Published on Web 01/03/2001

752 J. Am. Chem. Soc., Vol. 123, No. 4, 2001
Communications to the Editor
Table 2. Skeletal Rearrangement of Ketimine 1 by 3 and Cy3P
So far, the skeletal rearrangement has appeared to proceed
toward the structures of cyclohexanone and cyclopentanone. This
postulate was examined by performing a skeletal rearrangement
of two bicyclic compounds, 20 and 21, ketimines of norcamphor
and bicyclo[3.2.1]octan-2-one. While ketimine 20, consisting of
cyclopentanone and cyclohexanone structures, does not show any
reactivity for the skeletal rearrangement, the reaction of the
ketimine 21 bearing cycloheptanone structure at 150 °C for 1 h
leads to the bicyclic ketone 23 (25% yield) having two cyclopentyl
structures exclusively after hydrolysis of 22 (Scheme 3). A
ratio of
13:14
overall
entry
reactant 1 (n)
products
13b
13c +14c
13d + 14d
yield,a %
1
2
3
4
5
1a (n ) 0)
1b (n ) 1)
1c (n ) 2)
1d (n ) 3)
1h (n ) 4)
0
21
82
12
0
100:0
76:24
33:67
a Yields and the ratio of 13 and 14 were determined by GCD.
cycloalkanoketimines react differently according to size is not
clear, but one speculation is that the cause may be the formation
of metallacyclic complex 7. To cleave the C-C bond of
cycloalkanoketimine 1, substrate should be flexible enough to
form the unstrained metallacyclic complex 7. Large-sized cy-
cloalkanoketimines such as 1c, 1d, 1e, and so on satisfy this
requirement. However, the formation of 7 seems not to be facile
for small-sized ketimines such as 1a and 1b due to the ring strain.
Contrastingly, when cycloalkanoketimine 1 was heated without
2 under Rh(I) catalyst, the ring-contracted products 13 and 14
were obtained (eq 2). For example, the reaction of cyclohep-
Scheme 3
significant observation is that the C-C bond cleavage occurs at
a rather than at b even though a is a sterically more congested
C-C bond than b.17 If b were cleaved, 25 should have been
formed after hydrolysis of 24, but 25 was not determined.
tanoketimine 1c at 150 °C for 1 h in the presence of 3 (10 mol
% based on 1c) and Cy3P (20 mol %) affords a mixture of
2-methylcyclohexanone (13c) and 2-ethylcyclopentanone (14c)
in an 82% yield in a 76:24 ratio after hydrolysis (Table 2, entry
3).15 In a rearrangement of cyclohexanoketimine 1b, only 2-meth-
ylcyclopentanone (13b) was determined in a 21% yield (entry
2): its not forming 2-ethylcyclobutanone (14b) was probably due
to the instability of the strained cyclobutanone structure. With
cyclooctanoketimine 1d, a mixture of 13d and 14d was obtained
in a 33:67 ratio in a 12% yield (entry 4). 1a and 1h did not show
any skeletal rearrangement.16
In this communication, we present C-C bond activations of
various cycloalkanoketimines with and without 1-alkene by Rh-
(I) catalysts. Through the C-C bond activation by an Rh(I)
catalysts, ring-opened alkenones are obtained with the addition
of olefins, and skeletal-rearranged cycloalkanone derivatives are
isolated without olefins.
Without additional olefins, a hydride inserts itself into the
terminal olefin in 8 by Markovnikov’s rule to generate 15, which
further undergoes â-hydrogen elimination and a hydride insertion
in 16 to give 17 (Scheme 2). Reductive eliminations of 15 and
17 produce 18 and 19, followed by hydrolysis to give 13 and 14.
Scheme 2
Acknowledgment. This work was supported by the National Research
Laboratory (2000-N-NL-01-C-271) Program administered by the Ministry
of Science and Technology. Authors acknowledge the Brain Korea 21
project.
Supporting Information Available: Experimental procedures for
preparation of cyclohexanoketimine 1b and the catalytic C-C bond
activation of 1c with 2 and the skeletal rearrangement of 1c by Rh(I)
catalyst, including the characterization data for 1a, 1b, 1c, 1d, 1e, 1f,
1g, 1h, 4d, 4e, 4f, 4g, 6g, 20, and 21 (PDF). This material is available
free of charge via the Internet at http://pubs.acs.org.
JA0033537
(17) If â-hydrogen elimination proceeds at the other side of a bridgehead
as below, the starting intermediate 26 is regenerated through 27. See: Olah,
G. A. Acc. Chem. Res. 1976, 9, 41.
The product distribution seems to follow the thermodynamic
stabilities of the rearranged products (18 and 19) compared with
those of the starting cycloalkanoketimine 1.
(15) The heating of cycloheptanone under (PPh3)3RhCl (10 mol %) and
2-amino-3-picoline (100 mol %) at 150 °C for 48 h resulted in a mixture of
13c and 14c in a 27% yield (the ratio of 13c and 14c is 67:33).
(16) Ketimines of cycloalkanone larger than cyclononanone did not show
any skeletal rearrangement either.