Tandem Cyclization/Hydrosilylation of Functionalized 1,6-Dienes Catalyzed by a Cationic Palladium Complex

Full text of DOI:10.1021/ja980242n

J. Am. Chem. Soc. 1998, 120, 3805-3806
3805
Tandem Cyclization/Hydrosilylation of
Scheme 1
Functionalized 1,6-Dienes Catalyzed by a Cationic
Palladium Complex
Ross A. Widenhoefer* and Michael A. DeCarli
P. M. Gross Chemical Laboratory, Duke UniVersity
Durham, North Carolina 27708-0346
ReceiVed January 22, 1998
1
The Pd(0)- or Rh(I)-catalyzed cyclization/addition of diynes,
enynes, and tetraenes employing H-X or X-X′ [X, X′ ) SiR
olefin â-migratory insertion.11,12 Organosilanes were initially
employed as the stoichiometric reductant due to their availability,
2
3
3
,
SnR , BR ] as the stoichiometric reductant is a synthetically useful
transformation which forms both a C-C bond and one or more
C-X bond (eq 1). In contrast, Pd- or Rh-catalyzed cyclization/
3
2
13
their low inherent reactivity toward olefins, and the ease of C-Si
14
oxidation. Although hydrosilylation of functionalized olefins
employing 1 as a catalyst had not previously been demonstrated,
we found that 115 catalyzed the addition of triethylsilane to
dimethyl allylmalonate at 0 °C to form the terminal alkyl silane
2 in 85% isolated yield (Scheme 1).
(1)
With both the migratory insertion and hydrosilylation reactivity
of 1 established, we explored cyclization/hydrosilylation of
functionalized dienes catalyzed by 1. When trimethylsilane was
bubbled through a solution of dimethyl diallylmalonate (3) (0.05
M) and 1 (5 mol %) at 0 °C for 5 min, the pale yellow solution
turned dark with complete consumption of the starting material
as determined by GC analysis. Evaporation of the solvent and
flash chromatography of the residue gave the trans-silylated
cyclopentane 4 in 80% yield (eq 3, Table 1).16 In addition to 4,
GC-MS analysis of the crude reaction mixture revealed the
addition of dienes has not been demonstrated and instead requires
a group 3, 4, or lanthanide catalyst (eq 2). The high activity
4
5
6
(2)
0
of these d -early-transition-metal complexes relative to the Pd
and Rh catalysts stems from the electropositivity of the metal
and the presence of an open coordination site. These features
facilitate both olefin â-migratory insertion and σ-bond metathesis,
the latter in preference to oxidative addition/reductive elimination
processes. Unfortunately, the synthetic utility of these protocols
is restricted by the extreme air- and moisture-sensitivity and
oxophilicity of the catalyst. Therefore, we began a program
directed toward the development of a facile and selective catalyst
for the cyclization/addition of functionalized dienes.
presence of a small quantity of an isomeric silylated cyclopentane
18
4
a (4:4a ) 54:1)17 and traces (∼5%) of hexamethyldisiloxane.
(3)
A range of tertiary silanes possessing both alkyl and aryl groups
A growing body of evidence suggests that a cationic, electro-
philic group 9 or 10 transition-metal complex employed in
conjunction with a noncoordinating counterion can display
reacted with 3 to give carbocycles 5-8 in good yield and with
excellent diastereoselectivity (>25:1) (Table 1).19 The dimeth-
ylphenylsilyl derivative 6 was converted to the corresponding
alcohol 9 in 74% yield by treatment with mercuric acetate and
peracetic acid (eq 4).20 The cyclization/hydrosilylation procedure
0
reactivity analogous to a d -metallocene complex (olefin insertion,
σ-bond metathesis) while maintaining good functional group
compatibility.7
-10
Specifically, we targeted the cationic palladium
+
-
methyl complex (phen)Pd(Me)(OEt
2
)
BAr
] (1) as a potential cycliza-
tion/addition catalyst due to its high reactivity with respect to
4
[phen ) 1,1-
(4)
6 3 3 2
phenanthroline, Ar ) 3,5-C H (CF )
(
1) (a) Lautens, M.; Smith, N. D.; Ostrovsky, D. J. Org. Chem. 1997, 62,
8
6
970. (b) Tamao, K.; Kobayashi, K.; Ito, Y. J. Am. Chem. Soc. 1989, 111,
478.
also tolerated both allylic and terminal olefinic substitution. For
(
2) Onozawa, S.; Hatanaka, Y.; Choi, N.; Tanaka, M. Organometallics 1997,
1
1
6, 5389. (b) Ojima, I.; Donovan, R. J.; Shay, W. R. J. Am. Chem. Soc. 1992,
14, 6580.
(11) Rix, F. C.; Brookhart, M.; White, P. S. J. Am. Chem. Soc. 1996, 118,
2436.
(3) (a) Obora, Y.; Tsuji, Y.; Kakehi, Kobayashi, M.; Shinkai, Y.; Ebihara,
(12) (a) Rix, F. C.; Brookhart, M. J. Am. Chem. Soc. 1995, 117, 1137. (b)
Rix, F. C.; Brookhart, M.; White, P. S. J. Am. Chem. Soc. 1996, 118, 4746.
(13) Kraus, G. A.; Liras, S. Tetrahedron. Lett. 1990, 31, 5265.
(14) Jones, G. R.; Landais, Y. Tetrahedron 1996, 52, 7599.
M.; Kawamura, T. J. Chem. Soc., Perkin Trans. 1 1995, 599. (b) Takacs, J.
M.; Chandramouli, S. Organometallics 1990, 9, 2877. (c) Takacs, J. M.; Zhu,
J.; Chandramouli, S. J. Am. Chem. Soc. 1992, 114, 773.
(
4) (a) Negishi, E-i.; Jensen, M. D.; Kondakov, D. Y.; Wang, S. J. Am.
(15) Complex 1 was generated in situ at 0 °C from a 1:1 mixture of HBAr
(OEt and (phen)Pd(Me) ; control experiments revealed that both components
were required for catalysis.
4
‚-
Chem. Soc. 1994, 116, 8404. (b) Shaughnessy, K. H.; Waymouth, R. M. J.
Am. Chem. Soc. 1995, 117, 5873.
)
2 2
2
1
(
5) Molander, G. A.; Michols, P. J. J. Am. Chem. Soc. 1995, 117, 4415.
6) Onozawa, S.; Sakakura, T.; Tanaka, M. Tetrahedron Lett. 1994, 35,
(16) The H and 13C NMR spectra of 4 were identical to published NMR
data: Miura, K.; Oshima, K.; Utimoto, K. Bull. Chem. Soc. Jpn. 1993, 66,
2348. The trans stereochemistry of the remaining compounds was inferred
by analogy to 4.
(
8
177.
(
(
(
(
7) Arndtsen, B. A.; Bergman, R. G. Science 1995, 270, 1970.
8) Burger, P.; Bergman, R. G. J. Am. Chem. Soc. 1993, 115, 10462.
9) Yamamoto, A. J. Organomet. Chem. 1995, 500, 337.
(17) The minor isomer may correspond to either a diastereomer or a
regioisomer of 4.
10) (a) Johnson, L. K.; Mecking, S.; Brookhart, M. J. Am. Chem. Soc.
(18) Confirmed by GC-MS analysis and comparison to authentic sample.
(19) Limitations include primary and secondary silanes, dienes which
possessed internal or diterminal olefinic substitution, 1,6-enynes, and 1,6-
diynes.
1
996, 118, 267. (b) DiRenzo, G. M.; White, P. S.; Brookhart, M. J. Am. Chem.
Soc. 1996, 118, 6225. (c) Hauptman, E.; Sabo-Etienne, S.; White, P. S.;
Brookhart, M.; Garner, J. M.; Fagan, P. J.; Calabrese, J. C. J. Am. Chem.
Soc. 1994, 116, 8038.
(20) Fleming, I.; Sanderson, P. E. J. Tetrahedron Lett. 1987, 28, 4229.
S0002-7863(98)00242-X CCC: $15.00 © 1998 American Chemical Society
Published on Web 04/04/1998

3806 J. Am. Chem. Soc., Vol. 120, No. 15, 1998
Communications to the Editor
Table 1. Cyclization/Hydrosilylation of Functionalized Dienes
Catalyzed by 1
Scheme 2
the corresponding carbocycles 24-27 in good yield as mixtures
of diastereomers. Likewise, 1,3-diketone 28 cyclized to form 29
in 64% yield while N,N-diallyltrifluroroacetamide (30) reacted
with triethylsilane to form pyrrolidine 31 in 43% yield (Table
19
1).
We propose a plausible mechanism for diene cyclization/
hydrosilylation initiated by reaction of 1 with silane to generate
the palladium-silyl intermediate I (Scheme 2). â-Migratory
insertion of an olefin into the Pd-Si bond of I followed by
â-migratory insertion of the pendant olefin into the resulting
Pd-C bond of II would generate palladium alkyl intermediate
III. Reaction of III with silane could then release the carbocycle
and regenerate the palladium silyl complex I. Reaction of a late-
transition-metal alkyl complex with a silane is known to generate
a metal-silyl complex,8 and ample precedence exists for
,22
2
2
â-migratory insertion of an olefin into a M-Si bond.
In
addition, the resistance of palladium(II) toward oxidative addition
strongly suggests that Si-H bond cleavage occurs via a σ-bond
metathesis pathway. σ-Bond metathesis has been invoked in a
range of transformations involving late-transition-metal alkyl
complexes with H-X bonds [X ) C, Si, B].7
,23
In summary, the electrophilic palladium complex 1 served as
an effective catalyst for the cyclization/hydrosilylation of suitably
functionalized 1,6-dienes. Despite a limited substrate scope, the
protocol displayed impressive reaction rates and high regio- and
diastereoselectivity and was tolerant to a range of functionality
and terminal olefin substitution. This combination of reactivity
and selectivity establishes the potential of cationic late-transition-
metal complexes as catalysts for use in organic synthesis.
a
Yields refer to isolated material which was >95% pure as
1
b
determined by H NMR, GC, and/or elemental analysis. Determined
by capillary GC analysis of the crude reaction mixture. GC not
obtained, a single isomer detected by H NMR spectroscopy. 3:1
mixture of trans:cis isomers.
c
Acknowledgment. R.W. thanks the Camille and Henry Dreyfus
Foundation for a New Faculty Award and Johnson Matthey (Alfa Aesar)
for a generous loan of palladium chloride.
1
d
example, reaction of triethylsilane with dienes possessing a methyl
Supporting Information Available: Experimental procedures, spec-
troscopic and analytical data for relevant compounds (11 pages, print/
PDF). See any current masthead page for ordering information and Web
access instructions.
(
10), phenyl (11), or methylphenoxy (12) group at a terminal
olefinic carbon atom gave the corresponding carbocycles (13-
5) in >70% yield with good regio- and diastereoselectivity
Table 1). The disubstituted diene 16 and cyclohexenyl derivative
7 also underwent facile cyclization/hydrosilylation to form
1
(
1
Note Added in Proof. The hydrosilylation of unfunctionalized
olefins catalyzed by 1 has been reported: LaPoint, A. M.; Rix,
F. C.; Brookhart, M. J. Am. Chem. Soc. 1997, 119, 906.
carbocycles 18 and 19, respectively, in >70% yield as mixtures
of diastereomers.
The protocol required gem-bis(carbomethoxy) or related groups
at the 4,4′-position of the diene for greatest efficiency.21 For
example, dienes which possessed both a carbomethoxy and an
acetyl (20), acetamide (21), sulfonyl (22), or cyano (23) group at
the 4,4′-position underwent cyclization/hydrosilylation to form
JA980242N
(
22) (a) Brookhart, M.; Grant, B. E. J. Am. Chem. Soc. 1993, 115, 2151
and references therein. (b) Marciniec, B.; Pietraszuk, C. Organometallics 1997,
1
6, 4320.
(23) (a) Hartwig, J. F.; Bergman, R. G.; Andersen, R. A. J. Am. Chem.
Soc. 1991, 113, 3404. (b) Hartwig, J. F.; Bhandari, S.; Rablen, P. R. J. Am.
Chem. Soc. 1994, 116, 1839. (c) Bryndza, H. E.; Fong, L. K.; Paciello, R. A.;
Tam, W.; Bercaw, J. E. J. Am. Chem. Soc. 1987, 109, 1444. (d) Reference 8
and references therein.
(21) For an example of analogous substrate dependence, see: Grigg, R.;
Malone, J. F.; Mitchell, T. R. B.; Ramasubbu, A.; Scott, R. M. J. Chem. Soc.,
Perkin Trans. 1 1984, 1745.