Palladium-catalyzed cross-coupling reactions between 1-alkynylstibines and acyl chlorides

Article abstract of DOI:10.1016/S0040-4039(00)00554-2

1-Alkynyldiphenylstibines react with acyl chlorides in dichloroethane in the presence of a palladium(0) or (II) catalyst to afford alkynyl ketones by cross-coupling reaction in good to moderate yields. These reactions are highly substituent-selective in that only the alkynyl group could be transferred from the antimony compounds, even in the presence of a large excess of acyl chlorides. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4039(00)00554-2

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 41 (2000) 4143–4146
Palladium-catalyzed cross-coupling reactions between
1-alkynylstibines and acyl chlorides
Naoki Kakusawa, Kouichiro Yamaguchi, Jyoji Kurita ∗ and Takashi Tsuchiya
Faculty of Pharmaceutical Sciences, Hokuriku University, Kanazawa 920-1181, Japan
Received 17 February 2000; accepted 31 March 2000
Abstract
1-Alkynyldiphenylstibines react with acyl chlorides in dichloroethane in the presence of a palladium(0) or (II)
catalyst to afford alkynyl ketones by cross-coupling reaction in good to moderate yields. These reactions are highly
substituent-selective in that only the alkynyl group could be transferred from the antimony compounds, even in the
presence of a large excess of acyl chlorides. © 2000 Elsevier Science Ltd. All rights reserved.
Keywords: antimony and compounds; alkynes; acylation; coupling reactions; palladium catalyst.
The chemistry of organoantimony compounds has been extensively developed and applications of
such compounds to organic synthesis are of current interest.1 With regard to the carbon–carbon bond-
formation by use of organoantimony compounds, a variety of reactions such as self-coupling reactions,2
cross-coupling reactions,3–7 carbonylations,8 and photoreactions2a,9 have been reported. However, des-
pite the potential of these organoantimony compounds for synthetic reagents, most practical studies have
been limited to the use of peraryl antimony derivatives such as triarylstibines and pentaarylstiboranes,
mainly because of their high stability and easy availability. In the course of our continuing studies on
the synthesis and reactions of organoantimony compounds,9,10 we were interested in the preparation and
synthetic application of trivalent organoantimony compounds bearing alkynyl groups. Here we disclose
that treatment of 1-alkynylstibines 1 with acyl chlorides in the presence of a palladium (0) or (II) catalyst
resulted in cross-coupling reaction to afford alkynyl ketones 3 in good to moderate yields. These results
are the first example of the coupling reaction between trivalent organoantimony compounds and acid
halides.
Initially, we examined the reaction between diphenyl(phenylethynyl)stibine 1a,11 prepared by the
action of phenylethynyllithium on bromodiphenylstibine, and benzoyl chloride in the presence of a
variety of Pd(II) or Pd(0) catalysts in various solvents to optimize the reaction conditions. The results
are summarized in Table 1. Entry 1 in Table 1 shows that alkynyl ketone 3a (R=Ph) was produced even
in the absence of a palladium catalyst, but the yield was very low. The reaction rates were considerably
∗
Corresponding author. Tel: +00 81 76 229 1165; fax: +00 81 76 229 2781; e-mail: j-kurita@hokuriku-u.ac.jp (J. Kurita)
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PII: S0040-4039(00)00554-2
tetl 16833

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increased in a polar solvent such as acetonitrile and HMPA, but the yields of the product 3a were not im-
proved (entries 5 and 6). A comparison of the effectivenesses of catalysts showed that PhCH2PdCl(PPh3)2
and Pd(PPh3)4 were effective (entries 2, 7, and 11), whereas PdCl2(PhCN)2, Pd(OAc)2, and PdCl2 were
less active (entries 8–10). In most cases with Pd(II) catalysts, a catalytic amount of 1,4-diphenyl-1,3-
butadiyne was formed in addition to 3a. Consequently, the best result was obtained when the reaction
was carried out in dichloroethane with PdCl2(PPh3)2 as a catalyst (entry 2). These reactions were highly
substituent-selective in that only the alkynyl group was transferred from the antimony reagent 1a and no
coupling reaction between the phenyl and acyl groups occurred, even in the presence of a large excess
of acyl chlorides (5 equiv.). We have also found that triphenyl-, methyldiphenyl-, and diphenyl[(Z)-α-
styryl]-stibines12 gave no coupling products under the same reaction condition, although pentavalent
organoantimony compounds have been reported to afford coupling products by treatment with acyl
halides without a palladium catalyst.6b,c These present results are largely different from those of organotin
compounds in that a variety of substituents, e.g. alkynyl, vinyl, aryl, and alkyl groups on the tin atom can
be coupled with acyl halides in similar reaction.13
Table 1
Palladium-catalyzed cross-coupling reaction of diphenyl(phenylethynyl)stibine 1a with acyl
chlorides 2a
This alkynylation procedure could be expanded to a variety of aryl and alkyl acid halides. Aromatic

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acid chlorides afforded the corresponding alkynyl ketones 3 in good yield (entries 12–16), whereas alkyl
acid chlorides gave the products in relatively low yields (entries 17–20). In the latter cases, moderate
improvement of the yields of 3 was observed when the reaction was carried out with Pd(PPh3)4 instead
of PdCl2(PPh3)2 as a catalyst.
Also proved was that a variety of 1-alkynylstibines 1b–g11 could be coupled with benzoyl chloride to
produce the corresponding alkynyl ketones 3b–g (Scheme 1).
Scheme 1. (a) R0=Ph, 87%; (b) R0=p-methoxyphenyl, 66%; (c) R0=p-fluorophenyl, 71%; (d) R0=TMS, 65%; (e) R0=n-butyl,
68%; (f) R0=n-hexyl, 65%; (g) R0=benzyloxymethyl, 55%
From the fact that a catalytic amount of 1,3-diyne was formed with Pd(II) catalysts, the initial step
of the catalytic cycle in the present reaction would be the generation of Pd(0) species B by reductive
elimination of 1,3-diyne from the dialkynyl palladium complex A, produced by transmetallation between
Pd(II) catalysts and 2 equiv. of the 1-alkynylstibines 1. After oxidative addition of the acyl chlorides to
B giving rise to the Pd(II) complex C, ligand exchange between chloride and the alkynyl group on 1
may occur to afford the intermediate D, which presumably undergoes reductive-elimination to give rise
to the alkynyl ketone 3. This elimination also regenerates the active Pd(0) species B (Scheme 2). A
similar proposal has been offered for the palladium-catalyzed cross-coupling reaction between organotin
compounds and acyl halides. 13b
Scheme 2. Catalytic cycle for Pd-catalyzed coupling reaction of 1-alkynylstibines with acyl chlorides
In summary, we have found that 1-alkynyldiphenylstibines, easily prepared from the reaction of
bromodiphenylstibine with alkynyllithium, react with acyl chlorides in the presence of a palladium
catalyst to afford the corresponding alkynyl ketones in good to moderate yields. This is the first example
of coupling reaction between trivalent organoantimony compounds and acid halides. Further details of
the present reactions and the reactions of 1-alkynylstibines with other halogen compounds, e.g. aryl,
vinyl, and allyl halides, are currently under study.

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Acknowledgements
This work was supported in part by a Grant-in-Aid for Scientific Research (No 09672172) from the
Ministry of Education, Science, Sports and Culture of Japan.
References
1. For recent reviews on organoantimony compounds, see: (a) Huang, Y.-Z. Acc. Chem. Res. 1992, 25, 182–187; (b) Patai, S.
The Chemistry of Organic Arsenic, Antimony and Bismuth Compounds; John Wiley: Chichester, 1994; (c) Freedman, L.
D.; Doak, G. O. J. Organomet. Chem. 1994, 477, 1–29; (d) Freedman, L. D.; Doak G. O. J. Organomet. Chem. 1995, 496,
137–152; (e) Norman, N. C. Chemistry of Arsenic, Antimony and Bismuth; Blackie Academic & Professional: London,
1998.
2. (a) Shen, K.; McEwen, W. E.; Wolf, A. P. J. Am. Chem. Soc. 1969, 91, 1283–1288; (b) Akiba, K.-y.; Okinaka, T.; Nakatani,
M.; Yamamoto, Y. Tetrahedron Lett. 1987, 28, 3367–3368; (c); Barton, D. H. R.; Khamsi, J.; Ozbalik, N.; Reibenspies, J.
Tetrahedron 1990, 46, 3111–3122 (d) Akiba, K.-y. Pure Appl. Chem. 1996, 68, 837–842.
3. (a) Asano, R.; Moritani, I.; Fujiwara, Y.; Teranishi, S. Bull. Chem. Soc. Jpn. 1973, 46, 2910–2911; (b) Kawamura, T.;
Kikukawa, K.; Takagi, M.; Matsuda, T. Bull. Chem. Soc. Jpn. 1977, 50, 2021–2024; (c) Ikenaga, K.; Kikukawa, K.;
Matsuda, T. J. Org. Chem. 1987, 52, 1276–1280.
4. Fujiwara, M.; Tanaka, M.; Baba, A.; Ando, H.; Souma, Y. J. Organomet. Chem. 1996, 525, 39–42.
5. (a) Huang, Y.-Z.; Liao, Y. J. Org. Chem. 1991, 56, 1381–1386; (b) Zhang, L.-J.; Huang, Y.-Z. J. Organomet. Chem. 1993,
454, 101–103; (c) Zang, L.-J; Mo, X.-S; Huang, Y.-Z. J. Organomet. Chem. 1994, 471, 77–85; (d) Serre, S. L.; Guillemin,
J.-C.; Karpati, T.; Soos, L.; Nyulászi, L.; Veszprémi, T. J. Org. Chem. 1998, 63, 59–68.
6. (a) Yamamoto, Y; Okinaka, T.; Nakatani, M.; Akiba, K.-y. Nippon kagaku kaishi 1987, 1286–1287; (b) Zhang, L.-J.; Huang,
Y.-Z.; Jiang, H.-X.; Duan-Mu, J.; Liao, Y. J. Org. Chem. 1992, 57, 774–777; (c) Fujiwara, M.; Tanaka, M.; Baba, A.; Ando,
H.; Souma, Y. J. Organomet. Chem. 1996, 508, 49–52.
7. (a) Cho, C. S.; Tanabe, K.; Uemura, S. Tetrahedron Lett. 1994, 35, 1275–1278; (b) Cho, C. S.; Motofusa, S.; Ohe, K.;
Uemura, S. Bull. Chem. Soc. Jpn. 1996, 69, 2341–2348; (c) Matoba, K.; Motofusa, S.; Cho, C. S.; Ohe, K.; Uemura, S. J.
Organomet. Chem. 1999, 574, 3–10.
8. (a) Goel, A. B.; Richards, H. J.; Kyung, J. H. Tetrahedron Lett. 1984, 25, 391–392; (b) Cho, C. S.; Tanabe, K.; Itoh, O.;
Uemura, S. J. Org. Chem. 1995, 60, 274–275.
9. Kakusawa, N.; Tsuchiya, T.; Kurita, J. Tetrahedron Lett. 1998, 39, 9743–9746.
10. (a) Yasuike, S.; Shiratori, S.; Kurita, J.; Tsuchiya, T. Chem. Pharm. Bull. 1999, 47, 1108–1114; (b) Kurita, J.; Usuda, F.;
Yasuike, S.; Tsuchiya, T.; Tshuda, Y.; Kiuchi, F.; Hosoi, S. Chem. Commun. 2000, 191–192; (c) Yasuike, S.; Tsukada, S.;
Kurita, J.; Tsuchiya, T.; Tsuda, Y; Kiuchi, F.; Hosoi, S. Heterocycles 2000, 53, 525–528.
11. Satisfactory elemental analyses and spectroscopic (1H NMR and mass) data were obtained for all new compounds. 1a:
61%, colorless needles, mp 53–55°C (lit.14 84–86°C), 1b: 67%, colorless needles, mp 62–63°C, 1c: 64%, colorless prisms,
mp 42–43°C, 1d: 75%, colorless oil, 1e: 69%, colorless oil, 1f: 71%, colorless oil, 1g: 40%, colorless oil.
12. When the reaction between benzoyl chloride and diphenyl[(Z)-α-styryl]stibine (mp 54–55°C), prepared by LiAlH4
reduction of 1a, was carried out under harder reaction condition [PhCOCl: 1.5 equiv., PdCl2(PPh3)2: 5 mol%, 95°C, 6
h, in HMPA], the formation of trans-chalcone (8%) and benzophenone (12%) was observed.
13. (a) Logue, M. W.; Teng, K. J. Org. Chem. 1982, 47, 2549–2553, (b) Labadie, J. W.; Stille, J. K. J. Am. Chem. Soc. 1983,
105, 6129–6137.
14. Arzerbaev, I. I.; Yusupov, A.; Poplavskaya, I. A. Izv. Akad. Nauk Kaz. SSR, Ser. Khim. 1971, 21, 84–87.