Rhenium-catalyzed diastereoselective synthesis of aminoindanes via the insertion of allenes into a C-H bond

Article abstract of DOI:10.1021/ol101627x

Figure Presented. Aminoindane derivatives were synthesized diastereoselectively by the treatment of aromatic imines with allenes in the presence of a catalytic amount of a rhenium complex, [HRe(CO)₄] _n. The allenes inserted into the

Full text of DOI:10.1021/ol101627x

ORGANIC
LETTERS
2010
Vol. 12, No. 19
4274-4276
Rhenium-Catalyzed Diastereoselective
Synthesis of Aminoindanes via the
Insertion of Allenes into a C-H Bond
Yoichiro Kuninobu,* Peng Yu, and Kazuhiko Takai*
DiVision of Chemistry and Biochemistry, Okayama UniVersity, Tsushima,
Kita-ku, Okayama 700-8530, Japan
kuninobu@cc.okayama-u.ac.jp; ktakai@cc.okayama-u.ac.jp
Received July 14, 2010
ABSTRACT
Aminoindane derivatives were synthesized diastereoselectively by the treatment of aromatic imines with allenes in the presence of a catalytic
amount of a rhenium complex, [HRe(CO)4]n. The allenes inserted into the aromatic C-H bonds.
There have recently been many reports on transformations via
C-H bond activation because such powerful and efficient
transformations have the potential to replace previous methods.1
Among them, diastereoselective transformation via C-H bond
activation is a much desired reaction.2 For example, the
following research has been reported: chiral substrate-controlled
intramolecular reactions,3 chiral substrate-controlled intermolecu-
lar reactions,4 and chiral rhodium-catalyzed C-H functionalizations
using diazo compounds.5 However, examples of annulations with
high diastereoselectivity are still rare. We report herein a highly
diastereoselective rhenium-catalyzed formal [3 + 2] cycloaddition
between achiral aromatic imines and achiral allenes.
Treatment of aromatic ketimine 1a with aliphatic allene
2a in the presence of a catalytic amount of a rhenium
complex, [HRe(CO)4]n,6-9 without any solvents at 115 °C
for 24 h gave aminoindane derivative 3a in 88% yield as a
(1) There have been several reviews on transition-metal-catalyzed
transformations via C-H bond activation. See: (a) Kakiuchi, F.; Murai, S.
Top. Organomet. Chem. 1999, 3, 47–79. (b) Guari, Y.; Sabo-Etienne, S.;
Chaudret, B. Eur. J. Inorg. Chem. 1999, 1047–1055. (c) Dyker, G. Angew.
Chem., Int. Ed. 1999, 38, 1698–1712. (d) Kakiuchi, F.; Kochi, T. Synthesis
2008, 3013. (e) Colby, D. A.; Bergman, R. G.; Ellman, J. A. Chem. ReV.
2010, 110, 624. (f) Mkhalid, I. A.; Barnard, J. H.; Marder, T. B.; Murphy,
J. M.; Hartwig, J. F. Chem. ReV. 2010, 110, 890. (g) Lyons, T. W.; Sanford,
M. S. Chem. ReV. 2010, 110, 1147.
(5) (a) Davies, H. M. L.; Venkataramani, C.; Hansen, T.; Hopper, D. W.
J. Am. Chem. Soc. 2003, 125, 6462. (b) Davies, H. M. L.; Jin, Q. J. Am.
Chem. Soc. 2004, 126, 10862.
(6) Masciocchi, N.; Sironi, A. J. Am. Chem. Soc. 1990, 112, 9395
.
(7) We have already reported several rhenium-catalyzed transformations
via C-H bond activation. See: (a) Kuninobu, Y.; Tokunaga, Y.; Kawata,
A.; Takai, K. J. Am. Chem. Soc. 2006, 128, 202. (b) Kuninobu, Y.; Nishina,
Y.; Shouho, M.; Takai, K. Angew. Chem., Int. Ed. 2006, 45, 2766. (c)
Kuninobu, Y.; Nishina, Y.; Nakagawa, C.; Takai, K. J. Am. Chem. Soc.
2006, 128, 12376. (d) Kuninobu, Y.; Tokunaga, Y.; Takai, K. Chem. Lett.
2007, 36, 872. (e) Kuninobu, Y.; Nishina, Y.; Matsuki, T.; Takai, K. J. Am.
Chem. Soc. 2008, 130, 14062. (f) Kuninobu, Y.; Nishina, Y.; Okaguchi,
K.; Shouho, M.; Takai, K. Bull. Chem. Soc. Jpn. 2008, 81, 1393. (g)
Kuninobu, Y.; Fujii, Y.; Matsuki, T.; Nishina, Y.; Takai, K. Org. Lett. 2009,
11, 2711. (h) Kuninobu, Y.; Matsuki, T.; Takai, K. J. Am. Chem. Soc. 2009,
(2) For a review, see: Giri, R.; Shi, B.-F.; Engle, K. M.; Maugel, N.;
Yu, J.-Q. Chem. Soc. ReV. 2009, 38, 3242.
(3) (a) Dangel, B. D.; Johnson, J. A.; Sames, D. J. Am. Chem. Soc.
2001, 123, 8149. (b) Wong, M.-K.; Chung, N.-W.; He, L.; Yang, D. J. Am.
Chem. Soc. 2003, 125, 158. (c) Ferreira, E. M.; Stoltz, B. M. J. Am. Chem.
Soc. 2003, 125, 9578. (d) Rech, J. C.; Yato, M.; Duckett, D.; Ember, B.;
LoGrasso, P. V.; Bergman, R. G.; Ellman, J. A. J. Am. Chem. Soc. 2007,
129, 490. (e) Fraunhoffer, K. J.; White, M. C. J. Am. Chem. Soc. 2007,
129, 7274. (f) McQuaid, K. M.; Sames, D. J. Am. Chem. Soc. 2009, 131,
402. (g) Li, Q.; Yu, Z.-X. J. Am. Chem. Soc. 2010, 132, 4542.
(4) (a) Giri, R.; Chen, X.; Yu, J.-Q. Angew. Chem., Int. Ed. 2005, 44,
2112. (b) Pastine, S. J.; Gribkov, D. V.; Sames, D. J. Am. Chem. Soc. 2006,
128, 14220. (c) Heumann, A.; Reglier, M.; Waegell, B. Angew. Chem.,
Int. Ed. Engl. 1982, 21, 366.
131, 9914
.
(8) Rhenium complexes [ReBr(CO)3(thf)]2, ReBr(CO)5, and Re2(CO)10,
previously revealed to have catalytic activities in promoting transformations
via C-H bond activation, did not give any products via the insertion of
allene 2a into the C-H bond of ketimine 1a.
(9) Another group has also reported rhenium-catalyzed transformation
via C-H bond activation. See: Chen, H. Y.; Hartwig, J. F. Angew. Chem.,
Int. Ed. 1999, 38, 3391
.
10.1021/ol101627x  2010 American Chemical Society
Published on Web 08/30/2010

single product (eq 1).10-13 In this reaction, a quaternary
carbon center was constructed, and the two stereochemical
centers of 3a were defined completely.14 In addition, the exo-
methylene moiety of the product was not isomerized under the
reaction conditions. There has been only one report on transi-
tion-metal-catalyzed insertion of an allene into a C-H bond of
aromaticcompounds.15Inthisreaction,theterminalcarbon-carbon
double bond of an allene inserts into an aromatic C-H bond.
However, in our reaction, the insertion occurred at the internal
carbon-carbon double bond of allene 2a.
formed completely diastereoselectively. The aromatic ketimine
with a benzyl group at the nitrogen atom, 1b, provided
aminoindane derivative 3b in 81% yield (entry 1). The
corresponding aminoindane derivative 3c was generated from
the aromatic ketimine bearing an ethyl group at the R2
position, 1c (entry 2). Aromatic aldimine 1d produced
aminoindane 3d quantitatively (entry 3). By using an
aromatic ketimine having a methoxy group at the para
position, 1e, methylene indene 4a was formed in 90% yield
after the elimination of aniline from the corresponding
aminoindane derivative (entry 4). Aromatic ketimines with
a methyl or trifluoromethyl group at the para position, 1f
and 1g, afforded aminoindanes 3e and 3f in 86% and 85%
yields, respectively (entries 5 and 6). The reaction was not
affected by a functional group, such as a bromine atom (entry
7). The corresponding aminoindane derivatives 3h and 3h′ were
obtained as a mixture of two regioisomers using an aromatic
ketimine with a methyl group at the meta position of the imino
group (entry 8). In the case of using an aromatic ketimine
bearing a methyl group at the ortho position, 1j, a mixture of
aminoindane 3i and methyleneindene 4b was formed in 46%
and 24% yields, respectively (entry 9). The allene 2a also
inserted into an olefinic C-H bond, and methylenecyclopen-
tadiene 6 was afforded in 32% yield (entry 10).16
First, we investigated several aromatic and olefinic imines
(Table 1). The corresponding aminoindane derivatives were
Table 1. Reactions between Several Imines 1 and Allene 2aa
A heteroaromatic ketimine 7 also reacted with allene 2a
(eq 2). However, the desired reaction did not occur, and a
bicyclic compound with sulfur and nitrogen atoms on the
cyclic skeleton 8 was generated in 76% yield.17
Next, several allenes were investigated (Table 2). Allenes
with a functional group, such as an ether, silyl ether, or ester,
(10) Aminoindane derivative 3a was not formed using the following
transition-metal complexes: Mn2(CO)10, MnBr(CO)5, Ru3(CO)12, RuH2-
(CO)(PPh3)3, and RhCl(PPh3)3.
(11) Investigation of the amount of [ReH(CO)4]n: 1.0 mol %, 9%; 2.5
mol %, 72%; 10 mol %, 45%.
(12) Investigation of solvents: hexane, 67%; toluene, 55%; CH2ClCH2Cl,
trace; THF, 34%; EtOH, 0%; DMF, 0%; CH3CN, 23%.
(13) Investigation of reaction time: 1 h, 10%; 3 h, 53%; 8 h, 68%; 24 h,
72%.
(14) The stereochemistry of 3a was determined by differential nuclear
Overhauser effect (difNOE) measurements. See the following structure:
(15) During our investigations, one example of iridium-catalyzed
insertion of an allene into an aromatic C-H bond was reported. See: Zhang,
Y. J.; Skucas, E.; Krische, M. J. Org. Lett. 2009, 11, 4248. However, the
reaction point is quite different from our reaction. The reaction occurs at
the terminal position (R-position) of an allene, whereas our reaction
proceeded at the ꢀ-position of the allene.
(16) When 1-methyl-2-phenyl-1H-imidazole or 2-phenylpyridine was
employed as a substrate, allene 2a inserted into a C-H bond at the ortho-
position of the aromatic substrates and alkenylated products was obtained
in low yields (ca. 20%).
a 2a (1.5 equiv). b 135 °C. c [HRe(CO)4]n (Re: 10 mol %).
Org. Lett., Vol. 12, No. 19, 2010
4275

Table 2. Reactions between Ketimine 1a and Allenes 2a
Scheme 1. Proposed Mechanism for the Formation of
Aminoindanes 3 and Aminocyclopentene 5
bond activation of aromatic compounds; (2) insertion of an
allene into the formed Re-C bond; (3) intramolecular
nucleophilic cyclization to give an aminoindane or aminocy-
clopentene derivative.7a,b During the intramolecular cycliza-
tion, steric repulsion between the R2 and R4 groups causes
them to orient trans to each other on the five-membered ring
after the cyclization.
a 2a (1.5 equiv). b 2f (0.50 equiv) was added three times. c The ratios
of E and Z isomers are given in square brackets.
In summary, we have succeeded in rhenium-catalyzed
synthesis of aminoindane derivatives via the insertion of
allenes into a C-H bond of aromatic compounds followed
by successive intramolecular nucleophilic cyclization. Ex-
amples of the insertion of allenes into aromatic and olefinic
C-H bonds are still rare. In addition, the stereochemistry
of the two new carbon centers is defined completely. We
hope that this reaction will become a useful method to
synthesize aminoindane derivatives diastereoselectively.
gave the corresponding aminoindanes without losing the
functional group (entries 1-3). When an allene bearing a
phenyl group, 2e, was employed, the yield of the corre-
sponding aminoindane derivative 3m decreased (entry 4).
The corresponding aminoindane 3n was formed as a mixture
of E and Z isomers using internal allene 2f (entry 5).18
However, an aminoindane derivative was not formed using
a geminal disubstituted allene (6-vinylideneundecane).
The proposed mechanism for the formation of aminoin-
danes is as follows (Scheme 1): (1) rhenium-catalyzed C-H
Acknowledgment. This work was partially supported by
the Ministry of Education, Culture, Sports, Science, and
Technology of Japan.
(17) We assume two possible pathways to explain the mechanism for
the formation of bicyclic compound 8. One possibility is that after the
insertion of allene 2a into a C-H bond of ketimine 7, intramolecular
nucleophilic cyclization did not occur, and instead, reductive elimination
followed by electrocyclic reaction and isomerization of the olefin moieties
proceeded. The other is that intermolecular aza-Diels-Alder reaction
between allene 2a and ketimine 7 and isomerization of the olefin occurred
sequentially.
Supporting Information Available: General experimental
procedure and characterization data for aminoindanes 3,
methyleneindenes 4, methylenecyclopentadiene 6, and bi-
cyclic compound 8. This material is available free of charge
via the Internet at http://pubs.acs.org.
(18) In the case of using an allene with a chlorine, bromine, or iodine
atom (6-halo-1,2-hexadienes), the desired aminoindanes were formed in
trace amounts.
OL101627X
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Org. Lett., Vol. 12, No. 19, 2010