Palladium-complex-catalyzed cyanation of allylic carbonates and acetates using trimethylsilyl cyanide

Article abstract of DOI:10.1021/om980511i

Allylic carbonates are cyanated in high yields to β,γ-unsaturated carbonitriles using trimethylsilyl cyanide in the presence of a catalytic amount (5 mol %) of Pd(PPh₃)₄ in THF under reflux. In the reaction, cinnnamyl methyl carbonate affords cinnamyl cyanide in 98% yield. Allylic acetates also provide the corresponding carbonitriles, but often in lower yields. The cyanations of several cis- and trans-alicyclic substrates proceed cleanly (stereoselectivity > 99%) with overall retention. Characterization and reaction of palladium complexes relevant to the present catalysis indicate that transmetalation of an η³-allyl palladium complex with trimethylsilyl cyanide is facile, while the resulting cyano(η³-allyl)palladium complexes afford the corresponding allylic cyanides only when excess trimethylsilyl cyanide is present. Stereochemistry of the product indicates that the CN attacks the η³-allyl moieties from the palladium side.

Full text of DOI:10.1021/om980511i

Organometallics 1998, 17, 4835-4841
4835
P a lla d iu m -Com p lex-Ca ta lyzed Cya n a tion of Allylic
Ca r bon a tes a n d Aceta tes Usin g Tr im eth ylsilyl Cya n id e
Yasushi Tsuji,* Tomohito Kusui, Takaharu Kojima, Yoshihiko Sugiura,
Naoaki Yamada, Shinsuke Tanaka, Masahiro Ebihara, and Takashi Kawamura
Department of Chemistry, Faculty of Engineering, Gifu University, Gifu 501-1193, J apan, and
Coordination Chemistry Laboratories, Institute for Molecular Science, Myodaiji,
Okazaki 444-8585, J apan
Received J une 22, 1998
Allylic carbonates are cyanated in high yields to â,γ-unsaturated carbonitriles using
trimethylsilyl cyanide in the presence of a catalytic amount (5 mol %) of Pd(PPh3)4 in THF
under reflux. In the reaction, cinnnamyl methyl carbonate affords cinnamyl cyanide in 98%
yield. Allylic acetates also provide the corresponding carbonitriles, but often in lower yields.
The cyanations of several cis- and trans-alicyclic substrates proceed cleanly (stereoselectivity
> 99%) with overall retention. Characterization and reaction of palladium complexes
relevant to the present catalysis indicate that transmetalation of an η3-allyl palladium
complex with trimethylsilyl cyanide is facile, while the resulting cyano(η3-allyl)palladium
complexes afford the corresponding allylic cyanides only when excess trimethylsilyl cyanide
is present. Stereochemistry of the product indicates that the CN attacks the η3-allyl moieties
from the palladium side.
In tr od u ction
We have been developing catalytic silylation and/or
stannylation reactions using group 14 compounds7 and
found palladium-catalyzed functionalizations of allylic
esters by utilizing silicon compounds. That is, we
recently explored general silylation reaction of allylic
esters using organodisilanes as a silylating reagent,
which is catalyzed by a palladium complex and involves
a cleavage of the Si-Si σ-bond (eq 1).8 The strong
One of the most important aspects of η3-allylpalla-
dium chemistry might be its intermediacy in palladium-
catalyzed reactions of allylic compounds with nucleo-
philes.1,2 Formation of the η3-allylpalladium species by
oxidative addition of the allylic compounds to Pd(0) and
subsequent reaction with nucleophiles are imperative
in the catalysis. As the nucleophiles, stabilized carban-
ions,3 enolates,4 organotin reagents,5 and nitrogen nu-
cleophiles6 can be successfully employed in the presence
of strongly coordinating ligands such as phosphines.
However, the reaction will be more promising if untried
functionalities can be introduced to the allylic system.
oxophilicity of silicon would facilitate the silylation
reaction.
In addition, we found the first example of cyanation
of allylic esters catalyzed by a palladium complex and
reported the preliminary results (eq 2).9 In the reaction,
* Corresponding author, at Institute for Molecular Science. E-
mail: tsuji@ims.ac.jp. Fax: +81-564-55-5245.
(1) (a) Tsuji, J . Organic Synthesis with Palladium Compounds;
Springer: Heidelberg, 1980. (b) Trost, B. M. Acc. Chem. Res. 1996,
29, 355; 1980, 13, 385. (c) Tsuji, J . Pure Appl. Chem. 1982, 54, 197;
1986, 58, 869. (d) Tsuji, J . Tetrahedron 1986, 42, 4361. (e) Tsuji, J .;
Minami, I. Acc. Chem. Res. 1987, 20, 140.
(2) (a) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G.
Principles and Applications of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987; Chapter 19. (b)
Godleski, S. A. In Comprehensive Organic Synthesis; Trost, B. M.,
Fleming, I., Semmelhack, M. F., Eds.; Pergamon Press: Oxford, 1991;
Vol. 4, Chapter 3.3. (c) Harrington, P. J . Transition Metals in Total
Synthesis; J ohn Wiley & Sons: New York, 1990; Chapter 3.
(3) (a) Tsuji, J .; Takahashi, H.; Morikawa, M. Tetrahedron Lett.
1965, 4387. (b) Trost, B. M.; Verhoeven, T. R. J . Am. Chem. Soc. 1980,
102, 4730. (c) Trost, B. M.; Verhoeven, T. R. In Comprehensive
Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W.,
Eds.; Pergamon: Oxford, 1982; Vol. 8, Chapter 57, p 799.
(4) (a) Negishi, E.; Matsushita, H.; Chatterjee, S.; J ohn, R. A. J .
Org. Chem. 1982, 47, 3188. (b) Trost, B. M.; Self, C. R. J . Org. Chem.
1984, 49, 468.
(5) (a) Trost, B. M.; Keinan, E. Tetrahedron Lett. 1980, 21, 2595.
(b) Godschalx, J . P.; Stille, J . K. Tetrahedron Lett. 1980, 21, 2599. (c)
Gollaszewski, A.; Schwartz, J . Organometallics 1985, 4, 417.
(6) (a) Trost, B. M.; Genet, J . P. J . Am. Chem. Soc. 1976, 98, 8516.
(b) Trost, B. M.; Keinan, E. J . Org. Chem. 1979, 44, 3451. (c) Inoue,
Y.; Taguchi, M.; Hashimoto, H. Bull. Chem. Soc. J pn. 1985, 58, 2721.
trimethylsilyl cyanide (Me3SiCN) is very efficient as a
cyanide source and afforded â,γ-unsaturated carboni-
triles.10,11 Here, we describe details of the cyanation,
(7) (a) Obora, Y.; Tsuji, Y.; Kawamura, T. J . Am. Chem. Soc. 1995,
117, 9814. (b) Obora, Y.; Tsuji, Y.; Asayama, M.; Kawamura, T.
Organometallics 1993, 12, 4697. (c) Obora, Y.; Tsuji, Y.; Kawamura,
T. Organometallics 1993, 12, 2853, and references cited there in.
(8) (a) Tsuji, Y.; Funato, M.; Ozawa, M.; Ogiyama, H.; Kajita, S.;
Kawamura, T. J . Org. Chem. 1996, 61, 5779. (b) Tsuji, Y.; Kajita, S.;
Isobe, S.; Funato, M. J . Org. Chem. 1993, 58, 3607.
(9) Tsuji, Y.; Yamada, N.; Tanaka, S. J . Org. Chem. 1993, 58, 16.
(10) (a) Tsuji, J .; Ueno, H.; Kobayashi, Y.; Okumoto, H. Tetrahedron
Lett. 1981, 22, 2573. (b) Tsuji, J .; Yamada, T.; Minami, I.; Yuhara, M.;
Nisar, M.; Shimizu, I. J . Org. Chem. 1987, 52, 2988. (c) Araki, S.;
Minami, K.; Butsugan, Y. Bull. Chem. Soc. J pn. 1981, 54, 629.
10.1021/om980511i CCC: $15.00 © 1998 American Chemical Society
Publication on Web 10/08/1998

4836 Organometallics, Vol. 17, No. 22, 1998
Ta ble 1. Cya n a tion of Allylic Aceta tes (1) or Ca r bon a tes (2)a
Tsuji et al.
a
Conditions: 1 (1.5 mmol), Me3SiCN (3.0 mmol), Pd(PPh3)4 (0.075 mmol), THF (6.0 mL), under reflux for 18 h. b Isolated yields. Numbers
in parentheses show GLC yields determined by the internal standard method. c For 5 h. E/Z ) 80:20. e E/Z ) 71:29. f E/Z ) 70:30.
(3E,5E)/(3Z/5E)/(3E/5Z)/(3Z/5Z) ) 70:14:14:2. In benzene (6.0 mL) under reflux. In toluene (6.0 mL) under reflux.
d
g
h
i
including stereochemistry of the reaction, characteriza-
tion of palladium complexes relevant to the catalysis,
and results of enantioselective cyanation.
allylic carbonates 2, the corresponding aliphatic acetates
such as (E)-2-hexenyl, geranyl, and neryl acetates
showed only lower conversions (10%-50%), whereas
tertiary acetates such as 1e reacted somewhat faster
to afford better yields (entry 13). Accordingly, for the
present cyanation reaction, allylic carbonates 2 are more
suitable substrates than the corresponding acetates 1.
Alicyclic allylic carbonates also afforded the correspond-
ing carbonitriles in high yields (entries 14-17). Al-
though almost no 2k was consumed under the standard
conditions (reflux in THF), the cyanation readily pro-
ceeded at higher reaction temperature, under reflux in
toluene (entry 16) or 110 °C in diglyme. As the catalyst
precursors, Pd(PPh3)4 and Pd(CO)(PPh3)3 show high
catalytic activity. However, other representative cata-
lyst precursors were not effective; yields of 3a from 2a
under otherwise the same reaction conditions as entry
5 were as follows: Pd(OAc)2 4%, PdCl2(PPh3)2 trace, Pd-
Resu lts a n d Discu ssion
Cinnamyl acetate (1a ) reacts with 2 equiv of Me3SiCN
in the presence of 5 mol % Pd(PPh3)4 to afford cinnnamyl
cyanide (3a ) regio- and stereoselectively (entry 1, Table
1). The same product 3a was obtained from 1b, sug-
gesting a η3-allyl palladium intermediacy (entry 2).
Similarly, 1c and 1d afforded the corresponding cyan-
ated product 3b in high yields (entries 3 and 4). The
corresponding allylic carbonates were also smoothly
cyanated with Me3SiCN: 3a was obtained from 2a or
2b (entries 5 and 6), and 3b from 2c or 2d in high yields
(entries 7 and 8). Aliphatic allylic carbonates 2e-2h
readily gave the corresponding â,γ-unsaturated carbo-
nitriles regioselectively in high yields, but with modest
stereoselectivity (entries 9-12). The E/Z ratio did not
depend on conversion of 2, indicating E/Z isomerizations
during the reaction were unlikely. Compared with the
(DBA)2 (DBA ) dibenzylideneacetone) 5%, PdCl2-
12a,b
(PhCN)2 5%, Pt(PPh3)4 0%, Ru3(CO)12
(CO)6 3%.
4%, Mo-
12c
(11) For transition metal-catalyzed cyanation of allylic acetals using
Me3SiCN, see: (a) Mukaiyama, T.; Soga, T.; Takenoshita, H. Chem.
Lett. 1989, 997. (b) Mukaiyama, T.; Takenoshita, H.; Yamada, M.; Soga,
T. Chem. Lett. 1990, 229.
(12) (a) Tsuji, Y.; Mukai, T.; Kondo, T.; Watanabe, Y. J . Organomet.
Chem. 1989, 369, C51. (b) Kondo, T.; Mukai, T.; Watanabe, Y. J . Org.
Chem. 1991, 56, 487. (c) Trost, B. M.; Lautens, M. J . Am. Chem. Soc.
1982, 104, 5543

Cyanation of Allylic Carbonates and Acetates
Organometallics, Vol. 17, No. 22, 1998 4837
Trimethylsilyl cyanide is a potent cyanation reagent13
and was used so far in cyanations of aryl halides14a and
alkynes14b catalyzed by a palladium complex. On the
other hand, KCN and NaCN could be used for cyanation
of iodobenzene in the presence of a palladium complex.15
Therefore, efficiency of KCN and NaCN as cyanation
reagents for the allylic carbonates (2) and acetates (1)
was investigated. When KCN was employed in place
of Me3SiCN with 1a under the standard reaction condi-
tions (entry 1), the acetate 1a did not convert at all. If
Me3SiCN was replaced with KCN in entry 5, the
carbonate 2a was consumed completely, but only af-
forded cinnamyl methyl ether in 40% yield by pal-
ladium-catalyzed decarboxylation.16 Employment of
NaCN rather than Me3SiCN in entry 5 lowered conver-
sion of 2a (<20%). In all the cases with KCN or NaCN
as the cyanide source, no cyanated product 3a was
obtained.
29Si NMR spectra of resulting reaction mixtures were
measured to elucidate the fate of the trimethylsilyl
moiety of Me3SiCN. After the reaction with allylic
acetates (1) (entry 1), the comparable amount of Me3-
SiOAc (4a ) (22.06 ppm; lit.17a 22.0 ppm) was found in
the reaction mixture along with excess Me3SiCN (-12.30
ppm; lit.17b -12.12 ppm). In the reaction with allylic
carbonates (2) (entry 5), comparable formation of Me3-
SiOMe (4b) (17.66 ppm; lit.17c 17.75 ppm) was confirmed
similarly. The strong oxophilicity of the trimethylsilyl
functionality (bond dissociation energy:18 Si-O 430-
530 kJ mol-1) may favor the reaction via effective
trapping of the oxygen-containing leaving group.
In an effort to determine the stereochemistry of the
present cyanation reaction, the reactions with several
cis- and trans-alicyclic substrates were examined. The
cyanation of a racemic mixture of cis-(1R*,5R*)-2m 19
under the standard reaction condition afforded trans-
(1R*,5S*)-3j (trans > 99%) stereoselectively in 94% yield
(eq 3). The trans-stereochemistry of the product could
Sch em e 1
cyanation from a cis-substrate to a trans-product was
observed with optically pure cis-(1R,5R)-2n , which
provides trans-(1R*,5S*)-3k (trans > 99%) in 73% yield
(eq 4). A chiral gas chromatograph analysis (on CP-
Chirasil Dex CB, CHROMPACK) showed the trans-
product 3k was a 1:1 mixture of the two enatiomers,
even if the optically pure cis-2n was employed. The
corresponding acetate, cis-(1R,5R)-1f, also gave trans-
(1R*,5S*)-3k (trans > 99%) stereoselectively, but con-
version of the reaction and the yield (12%) were very
low. Again, the acetate was less reactive in the present
cyanation. Furthermore, starting from a trans-sub-
strate, the similar overall inversion cyanation was
observed: optically pure trans-(1S,5R)-2o afforded a 1:1
racemic mixture of cis-(1R*,5R*)-3l (cis > 99%) in 86%
yield (eq 5). In this manner, the cyanation with the
be readily confirmed on the basis of their vicinal
couplings (axial-axial and axial-equatorial) for the
axial H6 proton19,20 at δ 2.02. Similar overall inversion
clean overall inversion proceeded from both cis- and
trans-substrates.
While the present cyanation is highly stereoselective
(overall inversion), optically active substrates such as
cis-(1R,5R)-2n , cis-(1R,5R)-1f, and trans-(1S,5R)-2o af-
forded only racemic mixtures (eqs 4 and 5). Apparently,
regiochemistry of the CN attack (a or b) cannot be
regulated without a chiral auxiliary (Scheme 1). To
realize enantioselective cyanation, the reaction should
be carried out in the presence of a chiral phosphine
ligand. As a catalyst precursor for the enantioselective
cyanation, [(C3H5)PdCl]2 (5 mol % as Pd atom) combined
with (S)-(-)-2-(diphenylphosphino)-2′-methoxy-1,1′-bi-
naphthyl ((S)-MeO-MOP)21 was employed. When the
cyanation of trans-(1S,5R)-2o was carried out with the
(13) (a) Weber, W. P. Silicon Reagents for Organic Synthesis;
Springer-Verlag: Berlin, 1983; pp 6-20. (b) Colvin, E. W. Silicon in
Organic Synthesis; Butterworth: London, 1981; pp 296-298.
(14) (a) Chatani, N.; Hanafusa, T. J . Org. Chem. 1986, 51, 4714. (b)
Chatani, N.; Takeyasu, T.; Horiuchi, N.; Hanafusa, T. J . Org. Chem.
1988, 53, 3539.
(15) (a) Sekiya, A.; Ishikawa, N. Chem. Lett. 1975, 277. (b) Takagi,
K.; Okamoto, T.; Sakakibara, Y.; Ohno, A.; Oka, S.; Hayama, N. Bull.
Chem. Soc. J pn. 1975, 48, 3298. (c) Dalton, J . R.; Regen, S. L. J . Org.
Chem. 1979, 44, 4443.
(16) Tsuji, J .; Yamada, T.; Minami, I.; Yuhara, M.; Nisar, M.;
Shimizu, I. J . Org. Chem. 1987, 52, 2998.
(17) (a) Bassingdale, A. R.; Posnan, T. B. J . Organomet. Chem. 1975,
175, 273. (b) Marsmann, H. C. Chem.-Ztg. 1972, 96, 286. (c) Van den
Berghe, E. V.; Van der Kelen, G. P. J . Organomet. Chem. 1973, 59,
175.
(18) Armitage, D. A. In Comprehensive Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford,
1982; Vol. 2, p 6.
(19) (a) Trost, B. M.; Verhoeven, T. R. J . Am. Chem. Soc. 1980, 102,
4730. (b) Ba¨ckvall, J .-E.; Granberg, K. L.; Heumann, A. Isr. J . Chem.
1991, 31, 17.
(20) Sheffy, F. K.; Godschalx, J . P.; Stille, J . K. J . Am. Chem. Soc.
1984, 106, 4833.
(21) (a) Uozumi, Y.; Tanahashi, A.; Lee, S.-Y.; Hayashi, T. J . Org.
Chem. 1993, 58, 1945. (b) Uozumi, Y.; Hayashi, T. J . Am. Chem. Soc.
1991, 113, 9887.

4838 Organometallics, Vol. 17, No. 22, 1998
Tsuji et al.
Sch em e 2
selective and afford 6a as a single isomer regio- and
stereoselectively. The product 6a was fully character-
ized with 1H and 13C NMR, DEPT, and C-H COSY
spectra. As for the π-allyl system of 6a , only H3 and C3
resonances have spin-spin couplings to the phosphorus
2
(3J H3-P ) 8.4 Hz and J C3-P ) 24.7 Hz), indicating trans
disposition of the PPh3 to the C3 carbon. Syn η3-allyl
3
structure of 6a is evident by J H3-H2 vicinal coupling
(12.8 Hz). As a model reaction for the transmetalation,
6a was allowed to react with 1.5 equiv of Me3SiCN in
CDCl3 at 0 °C for 1 h (eq 7). Instantaneous color change
from clear orange to yellow showed the reaction is fast.
1H and 13C NMR spectra of the resulting solution
indicated that all the 6a was consumed and the known
cyano complex 7a 28 formed quantitatively, which was
isolated in 74% yield from the reaction mixture. In
addition, the 29Si NMR spectrum of the same reaction
mixture showed a comparable formation of Me3SiOAc
(4a ) (22.47 ppm, lit.17a 22.0 ppm). These results clearly
indicate that the transmetalation between 6a and Me3-
SiCN occurs readily and regioselectively, affording 7a
and 4a . For the cyanation, the complex 7a itself showed
high catalytic activity. When 5 mol % of 7a was used
as a catalyst precursor in place of Pd(PPh3)4 in entry 5,
3a was obtained in 98% yield, indicating 7a could be
involved in the catalytic cycle and is not an inactive
species extruded from the catalysis.
Next, thermolysis of 7a was carried out under various
reaction conditions as a model reaction for step C.
Simply heating 7a in refluxing THF did not afford
expected (E)-2-butenyl cyanide 3m at all. In sharp
contrast, in the presence of 2 equiv of Me3SiCN under
otherwise identical conditions, 7a provided 3m smoothly
in 68% yield (eq 8). Although various reaction condi-
chiral catalyst system in benzene at 60 °C, cis-3l was
obtained in 63% ee and 89% yield; trans-3l was also
obtained in 3% yield. A racemic mixture of trans-2o
also gave the identical result under the same reaction
conditions. Using the same catalyst system in benzene
at 35 °C, 2l provided 3i in 19% ee and 99% yield. As
for other chiral auxiliaries, (R)-BINAP22 and (S)-(R)-
PPFA23 only afforded intractable mixtures in benzene,
while (+)-NMDPP24 did not show any enantioselectivity
in the cyanation.
A possible catalyst cycle for the present cyanation is
shown in Scheme 2. The catalyst cycle would consist
of three representative steps: oxidative addition of the
allylic esters to palladium(0) catalyst species (step A),
transmetalation of allylpalladium species (6) with Me3-
SiCN (step B), and reductive elimination to afford the
products (step C). The oxidative addition of allylic
esters to palladium(0) complexes has been well-stud-
ied.25 However, the transmetalation with Me3SiCN
(step B) and reductive elimination of the cyano(η3-allyl)-
palladium species 7 (step C) are totally unprecedented.26
Therefore, these two steps were explored using model
complexes.
As a model complex for the step B, η3-crotylpalladium
complex (6a : R ) Me, Z ) Ac, L ) PPh3) was prepared
from the corresponding known acetate dimer 5a 27 and
PPh3 in acetone at 0 °C (eq 6). The reaction is highly
tions were examined, 3m was afforded from 7a only
when Me3SiCN was present with 7a : addition of 4 equiv
of maleic anhydride, PPh3, tert-butyl isocyanide, or CO
(40 kg/cm2), which are all known to accelerate the
reductive elimination,29 was not effective to afford 3m .
To gain more information on a role of the Me3SiCN, 13C-
labeled Me3SiCN (Me3Si13CN) was prepared30 and
employed in the reaction. Using 2 equiv of Me3Si13CN
under the same reaction conditions as eq 8, 3m and 3m *
(3m containing 13CN moiety) were provided in 6:4 ratio
(total yield: 66%), while with 4 equiv of Me3Si13CN the
(22) Miyashita, A.; Yasuda, A.; Takaya, H.; Toriumi, K.; Ito, T.;
Souchi, T.; Noyori, R. J . Am. Chem. Soc. 1980, 102, 7932.
(23) Hayashi, T.; Konishi, M.; Fukushima, M.; Mise, T.; Kagotani,
M.; Tajika, M.; Kumada, M. J . Am. Chem. Soc. 1982, 104, 180.
(24) Morrison, J . D.; Masler, W. F.; Neuberg, M. K. Adv. Catal. 1976,
25, 81, and references therein.
(25) (a) Trost, B. M.; Verhoeven, T. R. J . Am. Chem. Soc. 1980, 102,
4730. (b) Hayashi, T.; Hagihara, T.; Konishi, M.; Kumada, M. J . Am.
Chem. Soc. 1983, 105, 7767, and references therein.
(26) (a) Reductive elimination of allylnickel cyanide was concluded
to proceed with retention from stereochemical studies on nickel-
catalyzed deuteriocyanation of 1,3-cyclohexadiene.26b,c (b) Ba¨ckvall, J .-
E.; Andell, O. S. J . Chem. Soc., Chem. Commun. 1984, 260. (c) Ba¨ckvall,
J .-E.; Andell, O. S. Organometallics 1986, 5, 2350.
(28) A° kermark, B.; Krakenberger, B.; Hansson, S.; Vitagliano, A.
Organometallics 1987, 6, 620.
(27) (a) Robinson, S. D.; Shaw, B. L. J . Organomet. Chem. 1965, 3,
367. (b) Takahashi, Y.; Tsukiyama, K.; Sakai, S.; Ishii, Y. Tetrahedron
Lett. 1970, 1913.
(29) Yamamoto, A. Organotransition Metal Chemistry; J ohn Wiley
& Sons: New York, 1986; pp 240-245.
(30) Reetz, M. T.; Chatziiosifidis, I. Synthesis 1982, 330.

Cyanation of Allylic Carbonates and Acetates
Organometallics, Vol. 17, No. 22, 1998 4839
two products were obtained in 4:6 ratio (total yield:
71%) (eq 9). Even though excess Me3Si13CN was used,
a substantial amount of 3m was formed together with
3m *. Hence, direct attack of the 13CN onto the π-allyl
moiety from outside of the coordination sphere might
be unlikely. In any event, involvement of Me3SiCN was
essential for the formation of 3m from 7a . Then, 7a
was treated with 1 equiv of Me3Si13CN in a NMR tube
for 1 h at room temperature, and the 13C NMR spectrum
was measured. In the reaction mixture, no reductive
elimination products (3m or 3m *) were formed due to
the lower reaction temperature. The spectrum of the
resulting solution showed a large broad resonance (the
width at half-height ν1/2 ) 180 Hz) at 142.1 ppm, which
is close to the CN resonance of 7a (141.3 ppm, lit.28 141.0
ppm), while the CN resonance of Me3Si13CN at 126.9
ppm (1J C-Si ) 52 Hz) decreased considerably. Appar-
ently, Me3SiCN interacts with 7a substantially via
exchange of the CN ligand.
F igu r e 1. Perspective ORTEP drawing of the molecular
structure of complex 7b. All non-hydrogen atoms are
represented by thermal ellipsoids drawn to encompass 50%
probability, and hydrogen atoms are deleted for ease of
viewing.
Ta ble 2. Selected Bon d Dista n ces a n d An gles
for 7b
Since the reductive elimination of 7a was rather
complicated due to the involvement of Me3SiCN as
mentioned above, another model complex, 7b, was
prepared from the known complex 5c31 by applying the
reported procedure28 (eq 10). The trans-structure of 7b
Distances (Å)
Pd(1)-P(1)
Pd(1)-C(4)
Pd(1)-C(27)
C(4)-C(5)
C(5)-C(6)
C(1)-C(6)
2.323(3)
2.12(1)
2.02(1)
1.43(2)
1.49(2)
1.52(2)
Pd(1)-C(3)
Pd(1)-C(5)
C(3)-C(4)
N(1)-C(27)
C(2)-C(3)
C(1)-C(2)
2.20(1)
2.25(1)
1.40(2)
1.14(1)
1.52(2)
1.53(2)
Angles (deg)
P(1)-Pd(1)-C(3)
P(1)-Pd(1)-C(5)
C(3)-Pd(1)-C(5)
C(2)-C(3)-C(4)
C(4)-C(5)-C(6)
C(1)-C(6)-C(5)
C(6)-C(1)-C(7)
95.8(3)
160.8(3)
65.5(5)
120(1)
120(1)
114(1)
111(1)
P(1)-Pd(1)-C(4)
P(1)-Pd(1)-C(27)
C(5)-Pd(1)-C(27)
C(3)-C(4)-C(5)
C(1)-C(2)-C(3)
C(2)-C(1)-C(7)
Pd(1)-C(27)-N(1)
127.5(4)
102.1(4)
96.7(5)
117(1)
113(1)
111(1)
177(1)
was confirmed by X-ray crystallographic analysis (Fig-
ure 1),32 and Table 2 lists selected bond distances and
angles for 7b. The reductive elimination (thermolysis)
of 7b was carried out, but its behavior was very
reminiscent of 7a : 7b would not afford 3j by simply
heating it in refluxing THF or even in refluxing toluene.
Only heating 7b with Me3SiCN (2 equiv) provided 3j in
92% yield (eq 11). Noteworthy is that 7b afforded trans-
dium side. Despite the function of Me3SiCN, the
reductive elimination process was stereoselective reten-
tion.26 Accordingly, the stereochemical path of the
catalysis will be as shown in eq 12. Reactions with some
(1R*,5S*)-3j stereoselectively (trans/cis ) 92:8), indicat-
ing the CN attacks the η3-allyl moiety from the palla-
stabilized anions are likely to occur by external attack
from the face opposite the metal and afforded overall
retention products.1 On the other hand, several nu-
cleophiles afford the overall inversion products33 via
initial attack on the metal followed by stereoselective
reductive elimination. In the present cyanation, two
factors might be responsible for the clean overall inver-
(31) Kurosawa, H.; Kajimaru, H.; Ogoshi, S.; Yoneda, H.; Miki, K.;
Kasai, N.; Murai, S.; Ikeda, I. J . Am. Chem. Soc. 1992, 114, 8417.
(32) Crystal data of 7b: monoclinic, space group P21/n, colorless, a
) 12.717(2) Å, b ) 9.881(2) Å, c ) 19.846 Å, â ) 104.01(1)°, V ) 2419.7-
(7) Å3, Z ) 4, T ) 23.0 °C, dcalcd ) 1.465 g/cm3, µ(Mo KR) ) 8.57 cm-1
R ) 0.069, Rw ) 0.065, GOF ) 1.56.
,

4840 Organometallics, Vol. 17, No. 22, 1998
Tsuji et al.
3e: Isolated as a mixture of (3E,5E), (3Z,5E), (3E,5Z), and
(3Z,5Z) isomers. (3E,5E): 1H NMR δ 0.91 (t, J ) 7 Hz, 3H),
1.43 (sext, J ) 7 Hz, 2H), 2.07 (q, J ) 7 Hz, 2H), 3.14 (d, J )
6 Hz, 2H), 5.41 (dt, J ) 15 Hz, 6 Hz, 1H), 5.76 (dt, J ) 15 Hz,
7 Hz, 1H), 6.02 (dd, J ) 15 Hz, 10 Hz, 1H), 6.33 (dd, J ) 15
Hz, 10 Hz, 1H); 13C NMR δ 13.67, 20.37, 22.26, 34.65, 117.1,
117.5, 128.5, 135.1, 136.8. (3Z,5E): 13C NMR δ 13.67, 20.58,
22.23, 29.82. (3E,5Z): 13C NMR δ 13.70, 15.93, 22.70, 34.97.
(3Z,5Z): 13C NMR δ 13.70, 15.84, 22.56, 29.72. Anal. Calcd
for C9H13N: C, 79.95; H, 9.69. Found: C, 79.84; H, 9.91.
3f: 1H NMR δ 1.52-1.59 (m, 6H), 2.09-2.15 (m, 4H), 3.05
(d, J ) 7 Hz, 2H), 5.10 (t, J ) 7 Hz, 1H); 13C NMR δ 15.5,
26.4, 27.3, 28.1, 28.8, 36.6, 108.4, 118.8, 146.4. Anal. Calcd
for C9H13N: C, 79.95; H, 9.69. Found: C, 79.81; H, 9.89.
3g: 1H NMR δ 1.46-1.59 (m, 1H), 1.74 (s, 3H), 1.82-1.90
(m, 1H), 1.91-2.22 (m, 5H), 3.01 (s, 2H), 4.71-4.72 (m, 1H),
4.73-4.75 (m, 1H), 5.78-5.84 (m, 1H); 13C NMR δ 20.8, 25.4,
27.3, 28.5, 30.5, 40.4, 109.1, 117.7, 125.8, 126.8, 149.0. Anal.
Calcd for C11H15N: C, 81.94; H, 9.38. Found: C, 81.85; H,
9.57.
trans-(1R*,5S*)-3j: 1H NMR δ 2.02 (ddd, J ) 13.6 Hz, 10.8
Hz, 5.7 Hz, 1H), 2.26-2.34 (m, 2H), 2.39-2.43 (m, 1H), 2.83-
2.92 (m, 1H), 3.35-3.42 (m, 1H), 3.73 (s, 3H), 5.64-5.70 (m,
1H), 5.92-5.99 (m, 1H); 13C NMR δ 25.6, 26.9, 27.8, 36.0, 52.1,
120.4, 130.3, 174.4. IR 2238 cm-1 (νCN); MS m/e 165 (M+).
Anal. Calcd for C9H11NO2: C, 65.44; H, 6.71. Found: C, 65.35;
H, 6.93.
sion reaction: (i) facile Pd-CN bond formation via the
fast transmetalation (step B) and (ii) attack of the CN
ligand from the palladium side by the stereoselective
reductive elimination prompted by Me3SiCN (step C).
In conclusion, Me3SiCN is an efficient cyanation
reagent for allylic carbonates in the presence of a
catalytic amount (5 mol %) of Pd(PPh3)4. The cyanation
proceeds with overall inversion in high yields. Char-
acterizations and reactions of some palladium complexes
relevant to the catalysis revealed that transmetalation
of η3-allylpalladium with Me3SiCN is facile to afford
cyano(η3-allyl)palladium, and Me3SiCN is indispensable
for formal reductive elimination.
Exp er im en ta l Section
Gen er a l P r oced u r e a n d Ma ter ia ls. All manipulations
were performed under an argon atmosphere in conventional
Schlenk-type glassware on a dual-manifold Schlenk line or in
a nitrogen-filled glovebox (UNICO, UN-650F). NMR spectra
were recorded in CDCl3 on a J EOL-R 400 and a Varian Inova-
400 (1H, 400 MHz; 13C, 100 MHz). The 29Si NMR (79.3 MHz)
measurements was carried out with an INEPT pulse sequence,
and chemical shifts were referred to external Me4Si. Elemen-
tal analysis was performed at the Microanalytical Center of
Kyoto University.
Trimethylsilyl cyanide was purchased from Tokyo Kasei.
The reagents and the solvents were dried and purified before
use by usual methods.34 The following compounds were
prepared by the published methods: cis-2m ,19 5a ,27 5c,31 7a ,28
Pd(PPh3)4,35a Pd(CO)(PPh3)3,35b PdCl2(PPh3)2,35c Pd(DBA)2,35d,e
PdCl2(PhCN)2,35f and Pt(PPh3)4.35g For preparation of 2i, the
corresponding alcohols was first converted to their lithium salt
using n-BuLi and then reacted with methyl chloroformate.
Allylic esters 2n , 1f, and 2o were obtained from the corre-
sponding carveols.36
cis-(1R*,5R*)-3j: 1H NMR δ 1.96 (ddd, J ) 13.3 Hz, 12.4
Hz, 11.2 Hz, 1H), 2.54-2.62 (m, 1H), 3.73 (s, 3H); 13C NMR δ
26.6, 27.0, 28.3, 37.9, 52.1, 120.8, 129.5, 173.9.
trans-(1R*,5S*)-3k : 1H NMR δ 1.74 (ddd, J ) 13.2 Hz, 12.6
Hz, 6.0 Hz, 1H), 1.76 (m, 3H), 1.83 (m, 3H), 1.85-1.98 (m, 1H),
2.11 (dm, J ) 13 Hz, 1H), 2.17-2.78 (m, 1H), 2.36-2.46 (m,
1H), 3.13 (m, 1H), 4.74 (m, 1H), 4.80 (m, 1H), 5.66 (m, 1H);
13C NMR δ 20.7, 21.8, 30.1, 30.8, 31.6, 37.1, 109.7, 120.9, 126.2,
126.9, 147.5; IR 2234 cm-1 (νCN). Anal. Calcd for C11H15N:
C, 81.94; H, 9.38. Found: C, 81.79; H, 9.69.
cis-(1R*,5R*)-3l: 1H NMR δ 1.74 (s, 3H), 1.81 (q, J ) 12.0
Hz, 1H), 1.87 (m, 3H), 1.95-2.04 (m, 1H), 2.08-2.18 (m, 2H),
2.25 (ddd, J ) 12.0 Hz, 5.6 Hz, 2.4 Hz, 1H), 3.26-3.36 (m,
1H), 4.74 (m, 1H), 4.78 (m, 1H), 5.65 (m, 1H); 13C NMR δ 20.5,
21.4, 30.1, 32.1, 32.7, 39.9, 110.0, 120.7, 125.7, 126.2, 147.5;
IR 2234 cm-1 (νCN). Anal. Calcd for C11H15N: C, 81.94; H,
9.38. Found: C, 81.82; H, 9.57.
P r ep a r a tion of 6a (Eq 6). A 30 mL flask was charged
with 5a (121 mg, 0.27 mmol) in acetone (5.0 mL). At 0 °C,
PPh3 (142 mg, 0.54 mmol) in acetone (1.5 mL) was added to
the 5a in acetone over 10 min, and the resulting solution was
stirred for 4 h at 0 °C. Then, the solvent was evaporated off
in vacuo to give 6a quantitatively.
6a : 1H NMR δ 1.63 (dd, J ) 8.4 Hz, 6.4 Hz, 3H), 1.78 (s,
3H), 2.60 (br, 2H), 4.83 (ddq, J ) 12.8 Hz, 8.4 Hz, 6.4 Hz, 1H),
5.37 (dt, J ) 12.8 Hz, 9.2 Hz, 1H), 7.1-7.8 (m, 15H); 13C NMR
δ 17.6, 24.0, 48.6, 97.8 (d, J ) 24.7 Hz), 116.2, 128.5 (d, J )
9.8 Hz), 130.2, 132.4 (d, J ) 41.1 Hz), 133.8 (d, J ) 41.1 Hz),
133.8 (d, J ) 14.8 Hz).
Cya n a tion P r oced u r e. A typical procedure is as follows:
A 20 mL flask was charged with Pd(PPh3)4 (87 mg, 0.075
mmol; 5.0 mol %), THF (6.0 mL), cinnamyl methyl carbonate
(2a ; 288 mg, 1.5 mmol), and Me3SiCN (298 mg, 3.0 mmol)
under an argon flow. The reaction was carried out under
reflux for 18 h. After the reaction, the whole mixture was
passed through a short Florisil column (8 mm i.d. × 70 mm)
to give a clear yellow solution. GLC analysis (OV-17 or PEG-
HT) with naphthalene as an internal standard showed cin-
namyl cyanide (3a ) was formed in 98% yield. The product was
isolated by Kugelrohr distillation in 92% yield (198 mg).
The products 3a , 3c, 3d , 3h , and 3i were identified as
reported.9
3b: 1H NMR δ 2.33 (s, 3H), 3.22 (d, J ) 6 Hz, 2H), 5.96 (dt,
J ) 16 Hz, 6 Hz, 1H), 6.66 (d, J ) 16 Hz, 1H), 7.11-7.28 (m,
4H); 13C NMR δ 20.6, 21.1, 115.6, 117.3, 126.2, 129.3, 132.8,
134.3, 138.1. Anal. Calcd for C11H11N: C, 84.04; H, 7.05.
Found: C, 84.15; H, 6.87.
Rea ction of 6a w ith Me3SiCN (Eq 7). At 0 °C, Me3SiCN
(95 mg, 0.96 mmol) was added to 6a (309 mg, 0.64 mmol) in
degassed CDCl3 (3.6 mL). Instantaneous color change from
clear orange to yellow occurred. 1H and 13C NMR measure-
ments showed that the known cyano complex 7a formed
quantitatively. Addition of ether (40 mL) to the solution
precipitated 7a as yellow powder in 74% yield (213 mg).
Th er m olysis of 7a (Eq 8) or 7b (Eq 11). Under an argon
atmosphere, 7a (90 mg, 0.20 mmol) and naphthalene (13 mg,
0.10 mmol, as an internal standard for GC analysis) were
dissolved in THF (8.0 mL). Me3SiCN (40 mg, 0.40 mmol) was
added to the 7a , and the solution was stirred under reflux for
16 h. GC analysis showed 3m was formed in 68% yield (0.14
mmol). Similar reaction of 7b afforded 3j in 92% yield (eq 11).
(33) (a) Temple, J . S.; Riediker, M.; Schwartz, J . J . Am. Chem. Soc.
1982, 104, 1310. (b) Matsushita, H.; Negishi, E.-I. J . Chem. Soc., Chem.
Commun. 1982, 160. (c) Hayashi, T.; Yamamoto, A.; Hagihara, T. J .
Org. Chem. 1986, 51, 723. (d) Sheffy, F. K.; Godschalx, J . P.; Stille, J .
K. J . Am. Chem. Soc. 1984, 106, 4833.
(34) Armarego, W. L. F.; Perrin, D. D. Purification of Laboratory
Chemicals, 4th ed.; Butterworth-Heinemann: Oxford, 1997.
(35) (a) Coulson, D. R. Inorg. Synth. 1972, 13, 121. (b) Kudo, K.;
Hidai, M.; Uchida, Y. J . Organomet. Chem. 1971, 33, 393. (c) Hertley,
F. R. The Chemistry of Platinum and Palladium; Applied Science:
London, 1973; p 458. (d) Takahashi, Y.; Ito, T.; Sakai, S.; Ishii, Y. J .
Chem. Soc., Chem. Commun. 1970, 1065. (e) Rettig, M. F.; Maitlis, P.
M. Inorg. Synth. 1977, 17, 134. (f) Hertley, F. R. The Chemistry of
Platinum and Palladium; Applied Science: London, 1973; p 462. (g)
Ugo, R.; Cariati, F.; La Monica, G. Inorg. Synth. 1968, 11, 105.
(36) (a) Grandi, R.; Pagnoni, U. M.; Trave, R. Tetrahedron 1974,
30, 4037. (b) Gemal, A. L.; Luche, J .-L. J . Org. Chem. 1979, 44, 4187.

Cyanation of Allylic Carbonates and Acetates
Organometallics, Vol. 17, No. 22, 1998 4841
P r ep a r a tion of 7b (Eq 10) a n d X-r a y Str u ctu r e Deter -
m in a tion . Cyanation of known complex 5c31 (300 mg, 0.55
mmol) by the reported procedure28 afforded 7b in 81% yield
(238 mg). Slow diffusion of hexane into a toluene solution of
7b afforded single crystals suitable for X-ray analysis. The
cell dimensions were determined by least-squares refinement
of diffractometer angles for 25 automatically centered reflec-
tions. Structure was solved and refined using the teXsan
crystallographic software package. Scattering factors for
neutral atoms were from Cromer and Waber,37 and anomalous
dispersion38 was used. The structure was solved by direct
methods (SHELXS8639) and expanded by DIRDIF.40 The
fixed positions with isotropic thermal parameters that were
1.2 times the connected atoms.
7b: 1H NMR δ 1.24-1.37 (m, 1H), 1.71-1.79 (m, 1H), 2.06-
2.16 (m, 1H), 2.31-2.40 (m, 1H), 2.79 (ddd, J ) 14.8 Hz, 8.6
Hz, 6.8 Hz, 1H), 3.52 (s, 3H), 4.32 (br, 1H), 5.22-5.27 (m, 1H),
5.72 (br, 1H), 7.36-7.52 (m, 15H); 13C NMR δ 28.7, 29.8, 36.9,
51.8, 81.7, 82.0 (d, J ) 29.6 Hz), 109.8, 128.8 (d, J ) 10.7 Hz),
130.6, 132.4 (d, J ) 40.5 Hz), 133.6 (d, J ) 13.3 Hz), 137.4 (d,
J ) 19.7 Hz), 173.8. IR 2120 cm-1 (νCN). Anal. Calcd for
C
27H26NO2PPd: C, 60.74; H, 4.91. Found: C, 60.92; H, 4.85.
2
Ack n ow led gm en t. This work was supported by a
weighting scheme was w ) [σ2(Fo) + 0.0001Fo -1. The final
]
Grant-in-Aid for Scientific Research on Priority Areas
“The Chemistry of Inter-element Linkage” (No. 09239104)
from Ministry of Education, Science, Sports and Cul-
ture, J apan.
full-matrix least-squares cycle included non-hydrogen atoms
with anisotropic thermal parameters and hydrogen atoms at
(37) Cromer, D. T.; Waber, J . T. In International Tables for X-ray
Crystallography; Hahn, T., Ed.; Kynoch Press: Birmingham, 1974; Vol.
IV.; Table 2.2A.
(38) Creagh, D. C.; McAuley, W. J . In International Tables for X-ray
Crystallography; Wilson, A. J . C., Ed.; Kluwer Academic Publishers:
Boston, 1992; Vol. C; Table 4.2.6.8, pp 219-222.
(39) Sheldrick, G. M. In Crystallographic Computing 3; Sheldrick,
G. M., Kruger, C., Goddard, R., Eds.; Oxford University Press: New
York, 1985; pp 175-189.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and refinement details, atomic coordinates, thermal
parameters, bond distances, bond angles, and torsion angles
of 7b (8 pages). See any current masthead page for ordering
information and Internet access instructions.
(40) Parthasarathi, V.; Beurskens, P. T.; Slot, H. J . B. Acta Crys-
tallogr. 1983, A39, 860.
OM980511I