May 2006
701
ethynylstibane (1).22) Insertion of CO to the complex (A) af-
forded acyl palladium complex (B) which was transformed
to the intermediate (C) by the transmetallation of ethynyl
group on the stibane. Following reductive elimination fur-
nished 3 (Route I-1). The direct cross-coupling product (4)
was produced from Ar-Pd(II)-E complex (D) which may be
originated from the intermediate (A) (Route I-2). When aryl
iodides with an electron-donating substituent (MeO, Me)
were employed as a coupling partner, a considerable amount
of homo-coupled 1,3-diynes (5) was formed (30% and 14%,
respectively). Slow oxidative addition of aryl iodides to the
Pd(0) species will facilitate the formation of Sb-Pd(II)-E in-
termediate (E) (Route II). These Routes I and II should be a
competitive process relying upon the reactivity toward oxida-
ether layer was washed with brine. The organic layer was dried over anhy-
drous magnesium sulfate and concentrated in vacuo. The residue was sepa-
rated on silica gel column chromatography using hexane as an eluent to give
ethynylketones (3a—i), diarylacetylenes (4a—i), and 1,4-diphenyl-1,3-bu-
tadiyne (5). The yields of the products (3, 4, 5) were determined by GLC
analysis (SE-30, 5%, 1.6 M, 210 °C) using octadecane as an internal standard
when they could not be separated by the chromatography, and the results are
collected in Tables 1 and 2. All products except for p-acetylphenyl-
(phenylethynyl)ketone (3d) are known compounds and the structure of them
was determined by comparing their melting points and spectral data (MS,
NMR, and/or IR) with those of the corresponding authentic samples. 3d:
colorless prisms (mp 103—105 °C, from hexane–benzene). EI-MS m/z: 248
(Mꢀ, 78%), 220 (100%), 129 (67%). IR (KBr) cmꢁ1: 2199 (CꢀC), 1686
1
(CꢂO). H-NMR (CDCl3) d: 2.54 (3H, s), 7.41—7.55 (3H, m), 7.70—7.73
(2H, m), 8.03 (2H, d, Jꢂ8.71 Hz), 8.26 (2H, d, Jꢂ8.71 Hz).
Reaction of Ethynylstibane (1) with Iodobenzene (2a) under 20 atm of
CO: Condition B General Procedure: A mixture of 1 (1.00 mmol), 2a—i
tive addition of the aryl halides (2) and the stibane (1) to (1.50 mmol), PdCl2(PPh3)2 (0.05 mmol) in DMA (20 ml) was heated at 80 °C
Pd(0) species.26) It has been well established that the reactiv-
ity of aryl halides to Pd(0) depends upon the electronic na-
ture of the substituents on the aryl group and the halides
for 1 h in a stainless steel cylinder (Nippon Taiatsu Kogyo Co. Ltd., 50 ml)
under 20 atm of CO. The reaction mixture was dissolved with ether and the
ether layer was washed with brine. The organic layer was dried over anhy-
drous magnesium sulfate and concentrated in vacuo. The residue was sepa-
bearing an electron-withdrawing substituent are more reac-
tive than those having an electron-donating group.29,30) Suc-
cessive transmetallation of the intermediates (E) with an-
other ethynylstibane led to the formation of diethynyl-Pd(II)
complex (F) and the following reductive elimination afforded
1,3-diynes (5) (Route II-2). Formation of the direct cross-
coupling products (4) would be also possible via the interme-
diate (D) caused from reaction of the intermediate (E) with
aryl iodide (Route II-1).
Under 20 atm of CO, carbonylation took place effectively
and no direct coupled products (4) were found from all the
reaction mixtures investigated, because insertion of CO to
Ar-Pd(II)-I (A) was facilitated to form acyl palladium com-
plex ArCO-Pd(II)-I (B). Accordingly, competitive Route I-2
was suppressed under high CO pressure environment, which
brought about predominant formation of 3. No decrease of
homo-coupled 1,3-diynes (5) under the high-pressure condi-
tions indicates that oxidative addition of the antimony
reagent (1) with the Pd(0) was not influenced by CO pressure
and that insertion of CO to Sb-Pd(II)-E intermediates (E)
with Route II-1 seemed to be unlikely. Consequently, these
results show that the present Sb-mediated carbonylation pro-
vides good yield of the unsymmetrical aryl ethynyl ketones
(3) even with electron-deficient aryl iodides which usually
result in inferior yields due to their tendency to undergo de-
carbonylation.31—33)
rated on silica gel column chromatography using hexane as an eluent to give
3 and 5. The yields of the products for 3 and 5 are collected in Table 2.
Acknowledgements Partial financial support for this work was provided
by a Grant-in Aid for Scientific Research (C) (no. 17590022) from Japan
Society for the Promotion of Science (JSPS), and by the Specific Research
Found from Hokuriku University, which is gratefully acknowledged.
References and Notes
1) Trost B. M., Fleming I., “Comprehensive Organic Synthesis,” Vol. 3,
Pergamon Press, Oxford, 1991, pp. 413—561.
2) Diederich F., Stang P. J., “Metal-Catalyzed Cross-Coupling Reactions,”
Wiley-VCH, New York, 1998.
3) Fausett B. W., Liebeskind L. S., J. Org. Chem., 70, 4851—4853
(2005).
4) Pena M. A., Sestelo J. P., Sarandeses L. A., Synthesis, 2005, 485—492
(2005).
5) Rendler S., Oestreich M., Synthesis, 2005, 1727—1747 (2005).
6) Denmark S. E., Sweis R. F., Chem. Pharm. Bull., 50, 1531—1541
(2002).
7) Nakao Y., Imanaka, H., Sahoo A. K., Yada A., Hiyama T., J. Am.
Chem. Soc., 127, 6952—6953 (2005).
8) Suzuki H., Ikegami T., Matano Y., Synthesis, 1997, 249—267 (1997).
9) Yamazaki O., Tanaka T., Shimada S., Suzuki Y., Tanaka M., Synlett,
2004, 1921—1924 (2004).
10) Faller J. W., Kultyshev R. G., Organometallics, 21, 5911—5918
(2002).
11) Nakamura T., Kinoshita H., Shinokubo H., Oshima K., Org. Lett., 4,
3165—3167 (2002).
12) Yamamoto H., Oshima K., “Main Group Metals in Organic Synthesis,”
Wiley-VCH, Weinheim, 2004.
13) Akiba K.-y., “Chemistry of Hypervalent Compounds,” Wiley-VCH,
New York, 1999.
Experimental
14) Lee S. W., Lee K., Seomoon D., Kim S., Kim H., Kim H., Shim E.,
Lee M., Lee S., Kim M., Lee P. H., J. Org. Chem., 69, 4852—4855
(2004).
15) Maerten E., Hassouna F., Couve-Bonnaire S., Mortreux A., Carpentier
J.-F., Castanet Y., Synlett, 2003, 1874—1876 (2003).
16) Pena M. A., Sestelo J. P., Sarandeses L. A., Synthesis, 2003, 780—784
(2003).
General Melting points were taken on a Yanagimoto micro melting
point hot-stage apparatus (MP-S3) and are uncorrected. 1H-NMR spectra
were recorded on a JEOL JNM-ECP-500 (500 MHz) spectrometer in CDCl3
using tetramethylsilane as internal standard (d 0 ppm) unless otherwise
stated. Mass spectra (MS) were obtained on a JEOL JMS-SX-102 instru-
ment by electronic impact at 70 eV. IR spectra were recorded on a HORIBA
FT-720 instrument in KBr disk. Chromatographic separations were accom- 17) Hanamoto T., Hanada K., Mido T., Bull. Chem. Soc. Jpn., 75, 2497—
plished with Silica Gel 60N (Kanto Chemical Co., Inc.). Thin-layer chro-
2502 (2002).
matography (TLC) was performed with Macherey-Nagel pre-coated TLC 18) Gotov B., Kaufmann J., Schumann H., Schumalz H.-G., Synlett, 2002,
plates Sil G25 UV254. High CO pressure reactions were performed in a stain-
1161—1163 (2002).
less steel reactor (100 ml) provided from Taiatsu Techno Corp., Japan. N,N- 19) Kang S.-K., Ryu H.-C., Hong Y. T., J. Chem. Soc., Perkin Trans. 1,
Dimethylacetamide (DMA) was purchased from Wako Pure Chemical Ind.
Ltd. Japan, and used without further purification.
2001, 736—739 (2001).
20) Kang S.-K., Ryu H.-C., Lee S.-W., J. Organomet. Chem., 610, 38—41
Reaction of Ethynylstibane (1) with Iodobenzene (2a) under 1 atm of
(2000).
CO: Condition A General Procedure: A mixture of ethynylstibane (1: 21) Ishiyama T., Kizaki H., Hayashi T., Suzuki A., Miyaura N., J. Org.
1.00 mmol), iodobenzene derivatives (2a—i: 1.50 mmol), Pd(OAc)2
(0.05 mmol), PPh3 (0.20 mmol) in DMA (20 ml) was heated at 80 °C for 1 h
under stream of CO. The reaction mixture was dissolved with ether and the
Chem., 63, 4726—4731 (1998).
22) Kakusawa N., Yamaguchi K., Kurita J., Tsuchiya T., Tetrahedron Lett.,
41, 4143—4146 (2000).