Nitrile-promoted Rh-catalyzed intermolecular hydroacylation of olefins with salicylaldehyde

Article abstract of DOI:10.1021/jo062501u

Rh-catalyzed intermolecular hydroacylation between salicylaldehyde and alkenylnitriles proceeded at room temperature to preferentially give normal-hydroacylated products. Addition of CH₃CN and NaOAc accelerated the Rh-catalyzed hydroacylation of monoolefins to exclusively produce the normal-hydroacylated products under mild reaction conditions. Plausible mechanisms for the regioselections are also described.

Full text of DOI:10.1021/jo062501u

Nitrile-Promoted Rh-Catalyzed Intermolecular Hydroacylation of
Olefins with Salicylaldehyde
Masanori Imai,† Masakazu Tanaka,*,‡ Shinji Nagumo,†,§ Norio Kawahara,† and
Hiroshi Suemune*,‡
Hokkaido College of Pharmacy, Hokkaido 047-0264, Japan, and Graduate School of Pharmaceutical
Sciences, Kyushu UniVersity, Fukuoka 812-8582, Japan
mtanaka@phar.kyushu-u.ac.jp; suemune@phar.kyushu-u.ac.jp
ReceiVed December 6, 2006
Rh-catalyzed intermolecular hydroacylation between salicylaldehyde and alkenylnitriles proceeded at room
temperature to preferentially give normal-hydroacylated products. Addition of CH3CN and NaOAc
accelerated the Rh-catalyzed hydroacylation of monoolefins to exclusively produce the normal-
hydroacylated products under mild reaction conditions. Plausible mechanisms for the regioselections are
also described.
SCHEME 1
Introduction
Rhodium-catalyzed intermolecular hydroacylations have in-
dependently been reported by the Jun1 and the Miura groups.2
They reported that chelation of aldehyde-imine, or that of
salicylaldehyde to the Rh-metal, suppressed the decarbonylation
and promoted the intermolecular hydroacylation. However, their
Rh-catalyzed hydroacylation reactions required rigorous reaction
conditions of refluxing in toluene. Recently, we have discovered
that Rh-catalyzed intermolecular hydroacylation between sali-
cylaldehyde 1 and 1,4-penta- or 1,5-hexadienes proceeded under
very mild conditions based on a “double-chelation” concept.3
However, the Rh-catalyzed intermolecular hydroacylation was
restricted to the 1,4-penta- or 1,5-hexadiene as an olefin (Scheme
1). Unfortunately, the intermolecular hydroacylation of mo-
noolefins such as 1-hexene and 1-octene did not proceed well,
except for the case of norbornenes.3c Also, the Willis group
reported Rh-catalyzed intermolecular hydroacylation between
â-sulfido aldehyde and R,â-unsaturated esters under mild
reaction conditions (55 °C), but in general the olefin substrates
were limited to R,â-unsaturated esters.4,5 Herein, we report the
Rh-catalyzed intermolecular hydroacylation of alkenylnitriles6
* To whom correspondence should be addressed. Tel.: +81-92-642-6604.
Fax: +81-92-642-6545.
† Hokkaido College of Pharmacy.
‡ Kyushu University.
§ Present address: Kogakuin University, Tokyo 163-8677.
(1) (a) Jun, C.-H.; Hong, J.-B.; Lee, D.-Y. Synlett 1999, 1-12. (b) Jun,
C.-H.; Chung, J.-H.; Lee, D.-Y.; Loupy, A.; Chatti, S. Tetrahedron Lett.
2001, 42, 4803-4805. (c) Jun, C.-H.; Moon, C. W.; Lee, D.-Y. Chem.-
Eur. J. 2002, 8, 2422-2428 and references cited therein.
(2) (a) Kokubo, K.; Matsumasa, K.; Nishinaka, Y.; Miura, M.; Nomura,
M. Bull. Chem. Soc. Jpn. 1999, 72, 303-311. (b) Miura, M.; Nomura, M.
J. Synth. Org. Chem. Jpn. 2000, 58, 578-586.
(3) (a) Tanaka, M.; Imai, M.; Yamamoto, Y.; Tanaka, K.; Shimowatari,
M.; Nagumo, S.; Kawahara, N.; Suemune, H. Org. Lett. 2003, 5, 1365-
1367. (b) Imai, M.; Tanaka, M.; Tanaka, K.; Yamamoto, Y.; Imai, N.;
Shimowatari, M.; Nagumo, S.; Kawahara, N.; Suemune, H. J. Org. Chem.
2004, 69, 1144-1150. (c) Tanaka, K.; Tanaka, M.; Suemune, H. Tetrahe-
dron Lett. 2005, 46, 6053-6056.
(4) (a) Willis, M. C.; McNally, S. J.; Beswick, P. J. Angew. Chem., Int.
Ed. 2004, 43, 340-343. (b) Willis, M. C.; Randell-Sly, H. E.; Woodward,
R. L.; Currie, G. S. Org. Lett. 2005, 7, 2249-2251. (c) Willis, M. C.;
Randell-Sly, H. E.; Woodard, R. L.; McNally, S. J.; Currie, G. S. J. Org.
Chem. 2006, 71, 5291-5297.
(5) Recently, Willis and coworkers reported Rh-catalyzed intermolecular
hydroacylation of monoolefins with â-sulfido aldehyde by using cationic
Rh-complex having a P-O-P diphosphine ligand. See: Moxham, G. L.;
Randell-Sly, H. E.; Brayshaw, S. K.; Woodward, R. L.; Weller, A. S.; Willis,
M. C. Angew. Chem., Int. Ed. 2006, 45, 7618-7622.
(6) Rh-catalyzed hydroformylation of alkenylnitriles. See: Lambers-
Verstappen, M. M. H.; de Vries, J. G. AdV. Synth. Catal. 2003, 345, 478-
482.
10.1021/jo062501u CCC: $37.00 © 2007 American Chemical Society
Published on Web 02/28/2007
J. Org. Chem. 2007, 72, 2543-2546
2543

Imai et al.
TABLE 1. Rh-Catalyzed Hydroacylation between Salicylaldehyde
and Alkenylnitriles
TABLE 2. Rh-Catalyzed Hydroacylation between Salicylaldehyde
and 1,5-Hexadiene in the Presence of MeCNa
3: yield %
entry
additive
solvent
time (h)
(ratio: n:i)
1b
2
MeCN
MeCN
CH2Cl2
CH2Cl2
CH2Cl2
72
72
4
72
2
39 (1:3)
59 (1:3)
>99 (1:5)
27 (1:9)
NaOAc (0.2 equiv)
NaOAc (0.2 equiv)
MeCN (6 equiv)
3b
4
5
MeCN (6 equiv),
>99 (1:5)
NaOAc (0.2 equiv)
adiponitrile (6 equiv),
NaOAc (0.2 equiv)
6
CH2Cl2
2
>99 (1:5)
RhCl(PPh3)3
(equiv)
products: yield %
entry
alkenylnitrile
(ratio: n:i)
a The reaction was carried out at room temperature using RhCl(PPh3)3
(0.2 equiv) in CH2Cl2 (1.5 mL). b These reaction conditions have already
been reported by us.
1
2
3
4
5
6
7
8
9
0.20
0.40
0.20
0.40
0.40
0.20
0.40
0.40
0.40
0.40
4: n ) 1
4: n ) 1
5: n ) 2
5: n ) 2
5: n ) 2b
6: n ) 3
6: n ) 3
7: n ) 4
8: n ) 8
9: n ) 9
10: 51 (5:1)
10: 98 (5:1)
11: 50 (>20:1)
11: 94 (>20:1)
11: 63 (>20:1)
12: 40 (>20:1)
12: 93 (>20:1)
13: 99 (>20:1)
14: 70 (>20:1)
15: 80 (>20:1)
that the normal-product 11a was obtained in preference to iso-
11b because in the case of the corresponding hydroacylation
of 1,5-hexadiene the iso-product was preferred.3a,b Even by the
use of 1.5 equiv of 4-pentenenitrile 5, the hydroacylation
proceeded to give the product 11a in 63% yield (entry 5). The
hydroacylation of 5-hexenenitrile 6 gave the hydroacylated
product 12a in 93% yield, whereas that of 1,6-heptadiene could
not proceed because of the long distance between the two
olefins.3a,b However, when benzaldehyde or 2-cyanobenzalde-
hyde was used instead of 1, the hydroacylation did not proceed
at all. Furthermore, the hydroacylation of alkenylnitriles 7-9
bearing a longer distance between an olefin and a nitrile function
proceeded smoothly to afford the products 13-15 in 70-99%
yields.
10
a The same equivalents of NaOAc as that of Rh-complex was added,
and the reaction was quenched in 5 h. b 1.5 equiv of 4-pentenenitrile 5 was
used.
and also the effect of nitrile compounds on the Rh-catalyzed
intermolecular hydroacylation of olefins.7
Results and Discussion
We reasoned that the alkenylnitriles may not chelate to the
Rh-metal, but the nitrile group coordinates to the Rh-metal to
effect the hydroacylation. That is to say, one nitrile coordinates
to the Rh metal to change the property of the Rh-complex, and
the newly formed Rh-complex catalyzes the hydroacylation of
the other alkenylnitrile molecule with salicylaldehyde. This
presumption arises from the fact that the normal-hydroacylated
products 10-15 were obtained as a major product, whereas the
iso-products were obtained in the case of the double-chelation-
promoted hydroacylation of 1,5-hexadienes.3a,b Furthermore, the
hydroacylation of 8 and 9 having a long distance between two
functional groups proceeded smoothly. The chelation of 8 or 9
to the Rh-metal forms a large ring metallocycle, and this large
ring might thermodynamically not be preferred.
Effect of Nitrile on the Rh-Catalyzed Hydroacylation of
1,5-Hexadiene. Next, we examined the additional effect of
nitriles on the hydroacylation between salicylaldehyde 1 and
1,5-hexadiene 2. The results are summarized in Table 2. The
hydroacylation of 2 in MeCN as a solvent was sluggish and
did not proceed efficiently even with the addition of NaOAc
(entries 1 and 2).3b,9 This drawback might be due to the low
solubility of a mixture in MeCN solution. Interestingly, when
MeCN (6.0 equiv) and NaOAc (0.20 equiv) were added to the
CH2Cl2 solution, the hydroacylation of 1,5-hexadienes 2 was
accelerated, completed within 2 h (entry 5), and the hydroacy-
lated products were obtained in quantitative yield (entry 5). The
addition of MeCN without a base was not advantageous (entry
4). Addition of adiponitrile instead of MeCN also worked well
(entry 6). The ratio of iso- and normal-hydroacylated products
was almost the same as that without nitriles; that is, the iso-
hydroacylated product was preferentially formed.3a,b
Rh-Catalyzed Hydroacylation between Salicylaldehyde
and Alkenylnitriles. We envisaged that a nitrile functional
group may coordinate to the Rh-complex because MeCN is
capable of coordinating to the Rh-complex.8 Thus, if alkenylni-
triles that have an olefin and a nitrile functional group are used
instead of 1,5-hexadiene, the Rh-catalyzed hydroacylation with
salicylaldehyde may proceed via chelation of both alkenylnitrile
and salicylaldehyde to the Rh-complex. We examined the
hydroacylation between salicylaldehyde 1 (1.0 equiv) and
various alkenylnitriles (6.0 equiv) at room temperature (20-
30 °C) in the presence of RhCl(PPh3)3 and NaOAc. The results
are summarized in Table 1.
The hydroacylation of allyl cyanide 4 with 1 proceeded to
afford a hydroacylated product 10. The isolated yield of 10 was
51% by use of 0.20 equiv of RhCl(PPh3)3 and NaOAc, and the
yield increased to 98% by use of 0.40 equiv of the Rh-complex
and NaOAc. The 1H NMR spectrum of 10 showed the
methylene proton signals at δ 3.22 (t, J ) 7.0 Hz, 1.67H), as
well as the methine proton signal at δ 3.86 (sestet, J ) 7.3 Hz,
0.17H) and the methyl proton signal at δ 1.47 (d, J ) 7.3 Hz,
0.5H), suggesting the product 10 was a mixture of normal-10a
and iso-10b in a ratio of 5 to 1. The hydroacylation of
4-pentenenitrile 5 by use of 0.4 equiv of the Rh-complex also
afforded the products 11a,b in 94% yield; preferentially normal-
11a was obtained as a major product (entry 4). It is noteworthy
(7) Ru- and Co-catalyzed intermolecular hydroacylations. (a) Lenges,
C. P.; White, P. S.; Brookhart, M. J. Am. Chem. Soc. 1998, 120, 6955-
6979. (b) Kondo, T.; Hiraishi, N.; Morisaki, Y.; Wada, K.; Watanabe, Y.;
Mitsudo, T. Organometallics 1998, 17, 2131-2134 and references therein.
(8) (a) Gillard, R. D.; Heaton, B. T.; Shaw, H. Inorg. Chim. Acta 1973,
7, 102-104. (b) Ohtani, Y.; Yamagishi, A.; Fujimoto, M. Bull. Chem. Soc.
Jpn. 1979, 52, 1537-1538. (c) Chin, C. S.; Choi, S.-N.; Kim, K.-D. Inorg.
Chem. 1990, 29, 145-146. (d) Bosnich, B. Acc. Chem. Res. 1998, 31, 667-
674.
(9) Addition of NaOAc may deprotonate the phenolic hydroxyl group
and accelerate the reaction.
2544 J. Org. Chem., Vol. 72, No. 7, 2007

Hydroacylation of Olefins with Salicylaldehyde
TABLE 3. Rh-Catalyzed Hydroacylation between Salicylaldehyde
and Various Olefins 16-24 in the Presence of MeCN
between salicylaldehyde 1 and monoolefins such as 1-hexene
and 1-octene smoothly proceeded to give the normal- and iso-
hydroacylated products 29 and 30 in a ratio of >20 to 1, in
86% and 82% yields, respectively. The ratio of normal- and
iso-products (>20:1) was almost the same as that of alkenylni-
triles (entries 3-10 in Table 1) and that of 1,7-octadiene (entry
3 in Table 3). Therefore, these reactions might proceed via the
same reaction pathway. The hydroacylation of 3,3-dimethylbut-
1-ene 22, which is a tert-butyl ethylene, also proceeded at room
temperature, and the normal-hydroacylated product 31 was
exclusively obtained in 82% yield (entry 7). Unfortunately, the
hydroacylation of disubstituted olefins or internal olefins did
not proceed, or proceeded just in trace amount. It should be
noted that the reaction was tolerant of protected amine, and thus
the hydroacylation of allyl amine 23 proceeded to give normal-
hydroacylated product 32 in 53% yield (entry 8). Under the
same reaction conditions, the hydroacylation of 1-hexyne 24
was completed within 1 h at room temperature, while the
reported reaction conditions require 2 h and the rigorous
condition of refluxing in toluene.2
Mechanistic Consideration of the Nitrile-Promoted Rh-
Catalyzed Hydroacylation. The detailed reaction mechanism
for the influence of nitriles is not clear. It has already been
reported that nitrile could be exchanged for the phosphine ligand
in the Rh-complex, or additionally coordinate to the transition
metal-complex.8 We measured a liquid-phase IR spectrum of
RhCl(PPh3)3 (1.0 equiv), MeCN (1.0 equiv), and salicylaldehyde
(1.0 equiv) in CH2Cl2 solution. The IR spectrum indicated an
increase of the CN stretching frequency; that is, the absorption
observed at 2256 cm-1 (νCN) in the free MeCN was shifted to
absorption at 2356 cm-1 (νCN).10 These results suggested that
the use of MeCN as an outer ligand would change the property
of the Rh-complex by coordination and might promote the
hydroacylation reaction.
The regio-selectivity, that is, iso- and normal-selectivity of
the products, could be explained on the basis of Rh-aldehyde-
olefin intermediates, albeit the real intermediates might consist
of nitrile, and the existence of the dinuclear Rh-complex may
play some important roles.11 The coordination of monoolefin
and salicylaldehyde would afford two plausible intermediates
(a) and (b), as shown in Figure 1. Transfer of the hydrogen
from the Rh-complex to the coordinated olefin might produce
alkylated Rh-intermediates (c) and (d). These intermediates (a-
d) may be interchangeable. Reductive elimination from inter-
mediate (c) affords the normal-hydroacylated product, whereas
that from intermediate (d) gives the iso-hydroacylated product.
Taking the thermodynamic stability of the intermediates into
consideration, intermediates (a) and (c) seem to be more
favorable than intermediates (b) and (d) because steric repulsion
exists in intermediates (b) and (d). Thus, the Rh-catalyzed
hydroacylation of monoolefins would preferentially afford the
normal-hydroacylated products. On the other hand, the hydro-
acylation of 1,5-hexadiene afforded the iso-hydroacylated
product as a major product. This may be attributed to the fact
that the 1,5-hexadiene-chelated Rh-intermediates (e) and (f),
which have only a minimal steric repulsion, may become
thermodynamically
a The reaction was carried out at room temperature using RhCl(PPh3)3
(0.4 equiv), NaOAc (0.4 equiv), and MeCN (6 equiv) in CH2Cl2 solution.
b 0.2 equiv of RhCl(PPh3)3 was used. c Isomer, which was acylated at the
C5-position of diene, was also formed. d The ratio was >20 (n):1 (i). e The
iso-hydroacylated product was not detected.
Effect of Nitrile on the Rh-Catalyzed Hydroacylation of
Various Olefins. Next, we checked the hydroacylation of
various olefins 16-23 with 1 using RhCl(PPh3)3 (0.20 or 0.40
equiv) in the presence of NaOAc (0.40 equiv) and MeCN (6.0
equiv) in CH2Cl2 solution. Table 3 summarizes the results. The
hydroacylation of 1,5-hexadienes 16 and 17 having a substituent
proceeded in 3-7 h at room temperature to produce the
hydroacylated products 25 and 26 in good yields (entries 1 and
2). The hydroacylation of 16 preferentially afforded the iso-
hydroacylated product 25b similarly to that in the absence of
MeCN,3a,b but that of 17 dominantly gave the normal-hydro-
acylated product 26a. The hydroacylation of 18 without MeCN
gave the product in merely 10-15% yield. In contrast, that under
the conditions of RhCl(PPh3)3 (0.40 equiv), NaOAc (0.40 equiv),
and MeCN (6.0 equiv) in CH2Cl2 solution afforded the normal-
and iso-hydroacylated products in a ratio of >20 to 1 in 73%
yield (entry 3). The reaction was tolerant of an ester functional
group. The hydroacylation of 1,6-diene 19 bearing a diester
smoothly proceeded to give normal-products 28 in 80% yield.
The iso-product was not detected at all (entry 4). The hydroa-
cylation of 19 could not proceed by use of RhCl(PPh3)3 only;
therefore, the addition of MeCN and NaOAc would enhance
the reactivity. These results suggested that the hydroacylation
of some 1,5- and 1,6-dienes in the presence of NaOAc and
MeCN may proceed via the diene-mono-coordinated intermedi-
ate, but not via the diene-chelated intermediate.
(10) Uson, R.; Oro, L. A.; Artigas, J.; Sariego, R. J. Organomet. Chem.
1979, 179, 65-72.
(11) (a) Colebrooke, S. A.; Duckett, S. B.; Lohman, J. A. B. Chem.
Commun. 2000, 685-686. (b) Gridnev, I. D.; Higashi, N.; Asakura, K.;
Imamoto, T. J. Am. Chem. Soc. 2000, 122, 7183-7194. (c) Aubry, D. A.;
Bridges, N. N.; Ezell, K.; Stanley, G. G. J. Am. Chem. Soc. 2003, 125,
11180-11181.
Thus, we tested the hydroacylation of various monoolefins,
which were not appropriate as the Rh-catalyzed-hydroacylation
substrate before. As expected, the Rh-catalyzed hydroacylation
J. Org. Chem, Vol. 72, No. 7, 2007 2545

Imai et al.
what large loading of the Rh-catalyst. The effect of RCN in
CH2Cl2 solution and its application to other metal-catalyzed
reactions are under study in our group.
Experimental Section
General Procedure for RhCl(PPh3)3-Catalyzed Hydroacyla-
tion between Salicylaldehydes and Alkenylnitriles. A solution
of salicylaldehyde (0.50 mmol), alkenylnitrile (3.00 mmol), RhCl-
(PPh3)3 (184 mg, 0.20 mmol), and NaOAc (16 mg, 0.20 mmol) in
CH2Cl2 (2.5 mL) was stirred at room temperature under an Ar
atmosphere. After being stirred for 5-72 h, the solution was
evaporated and diluted with ether. The precipitated Rh-complex
was filtered off, and the filtrate was concentrated in vacuo to leave
a residue. Purification by column chromatography on silica gel
(EtOAc in hexane) gave the hydroacylated products as a mixture
of iso- and normal-isomers.
General Procedure for RhCl(PPh3)3-Catalyzed Hydroacyla-
tion between Salicylaldehydes and Monoolefins in the Presence
of MeCN and NaOAc. A solution of salicylaldehyde (0.50 mmol),
monoolefin (3.00 mmol), RhCl(PPh3)3 (184 mg, 0.20 mmol), MeCN
(0.16 mL, 3.00 mmol), and NaOAc (16 mg, 0.20 mmol) in CH2-
Cl2 (2 mL) was stirred at room temperature under an Ar atmosphere.
After being stirred for 1-8 h, the solution was evaporated, and
diluted with ether, and then the precipitated Rh-complex was filtered
off. The filtrate was concentrated in vacuo, and the residue was
purified by column chromatography on silica gel (EtOAc in hexane)
to give the hydroacylated product.
FIGURE 1. Plausible intermediates for the Rh-catalyzed hydroacy-
lation.
stable, and the reductive elimination from the intermediate (f)
would occur. Thus, the hydroacylation of 1,5-hexadienes 2 and
16 predominantly afforded the iso-hydroacylated products.
However, the hydroacylation of 1,5-hexadiene 17 having a
terminal substituent dominantly gave the normal-hydroacylated
products 26a; this result may be attributed to the fact that the
terminal methyl group of 1,5-hexadiene would restrict the
chelation of diene to the Rh-metal, and thus the reaction would
proceed via a nonchelated mono-coordinated intermediate (c).
1-(2-Hydroxyphenyl)nonan-1-one (30). A solution of salicyl-
aldehyde (61 mg, 0.50 mmol), 1-octene (335 mg, 3.00 mmol),
RhCl(PPh3)3 (184 mg, 0.20 mmol), MeCN (0.16 mL, 3.00 mmol),
and NaOAc (16 mg, 0.20 mmol) in CH2Cl2 (2 mL) was stirred at
room temperature under an Ar atmosphere. After being stirred for
8 h, the solution was evaporated, and diluted with ether. Next, the
precipitated Rh-complex was filtered off, and the filtrate was
concentrated in vacuo to leave a residue, which was purified by
column chromatography on silica gel to give 30 (96 mg, 82%) as
Conclusion
a colorless oil. IR (neat): 2930, 2860, 1642 cm-1 1H NMR
.
We have developed Rh-catalyzed intermolecular hydroacy-
lation between salicylaldehyde and alkenylnitriles and, further-
more, disclosed that the addition of MeCN and NaOAc to the
CH2Cl2 solution enhanced the Rh-catalyzed intermolecular
hydroacylation. To the best of our knowledge, no additional
effect of the CN ligand on transition metal-catalyzed reactions
has been reported.12 Under these conditions, the hydroacylation
of monoolefins having a bulky substituent or a functional group
smoothly proceeded at room temperature to give the normal-
hydroacylated products,13 albeit the reaction required a some-
(CDCl3): δ 12.40 (s, 1H), 7.77 (br d, J ) 8 Hz, 1H), 7.46 (br t, J
) 8 Hz, 1H), 6.98 (br d, J ) 8 Hz, 1H), 6.89 (br t, J ) 8 Hz, 1H),
2.98 (t, J ) 7.6 Hz, 2H), 1.74 (quintet, J ) 7.6 Hz, 2H), 1.28-
1.41 (m, 10H), 0.88 (t, J ) 6.6 Hz, 3H). EI-HRMS calcd for
C15H22O2 (M+) 234.1620, found 234.1616.
Acknowledgment. This work was partly supported by a
Grant-in-Aid for Scientific Research (C) from the Japan Society
for the Promotion of Science, by a Grant-in-Aid for Young
Scientists (B) from the Ministry of Education, Culture, Sports,
Science, and Technology, and was also supported by a grant
from the Akiyama Foundation.
(12) Willis and coworkers reported that the Rh-catalyzed hydroacylation
of 4-cyanostyrene with â-sulfido aldehyde was superior to that of styrene
(ref 4). There may be two possibilities: one reason is the reactivity of
4-cyanostyrene by an electron-withdrawing group as reported, and the other
reason may be coordination of the CN group to the Rh-metal to change the
activity of the Rh-complex.
(13) Rh-catalyzed branch-selective hydroacylation of styrene. See: Hong,
Y.-T.; Barchuk, A.; Krische, M. J. Angew. Chem., Int. Ed. 2006, 45, 6885-
6888 and references therein.
Supporting Information Available: Preparation of alkenylni-
1
triles 8 and 9, spectroscopic data, and copies of H NMR or 13C
NMR spectra of all new compounds. This material is available free
of charge via the Internet at http://pubs.acs.org.
JO062501U
2546 J. Org. Chem., Vol. 72, No. 7, 2007