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(PhC≡C)2Zn undergoes coupling withDaOrIy: l10i.o10d3id9e/Cs6rCeCg0a8rd0l3e8sCs
of the method of preparation.
JSPS and Nagase Science and Technology Foundation (E.S.).
9
In ref. 4, PhC≡C–Zn–Et coordinated by PPh3 is shown to
form a cyclic dimer, where the alkyne moiety of a PhC≡C–
Zn–Et coordinates on zinc of the other PhC≡C–Zn–Et. This
type of phosphine-induced interaction possibly is concerned
with the role of the phosphine in the coupling reaction.
Notes and references
1
For reviews, see: Metal-Catalyzed Cross-Coupling Reactions,
ed. A. de Meijere and F. Diederich, Wiley-VCH, Weinheim,
2nd edn, 2004, vol. 1–2; J.-P. Corbet and G. Mignani, Chem.
Rev., 2006, 106, 2651–2710.
10 A. N. Abeywickrema, A. L. J. Beckwith, J. Chem. Soc.,
Chem. Commun., 1986, 464–465; H. Yasuda, Y. Uenoyama,
O. Nobuta, S. Kobayashi, I. Ryu, Tetrahedron Lett., 2008, 49,
367–370. See also ref. 2b.
2
For the coupling of aryl Grignard reagents with aryl or
alkenyl halides, see: (a) E. Shirakawa, Y. Hayashi, K. Itoh, R.
Watabe, N. Uchiyama, W. Konagaya, S. Masui and T.
Hayashi, Angew. Chem., Int. Ed., 2012, 51, 218–221; (b) N.
Uchiyama, E. Shirakawa and T. Hayashi, Chem. Commun.,
2013, 49, 364–366; (c) E. Shirakawa, R. Watabe, T.
Murakami and T. Hayashi, Chem. Commun., 2013, 49, 5219–
5221; (d) E. Shirakawa, K. Okura, N. Uchiyama, T.
Murakami and T. Hayashi, Chem. Lett., 2014, 43, 922–924.
For the coupling of arylzinc reagents with aryl or alkenyl
halides, see: (e) E. Shirakawa, F. Tamakuni, E. Kusano, N.
Uchiyama, W. Konagaya, R. Watabe and T. Hayashi, Angew.
Chem., Int. Ed., 2014, 53, 521–525. For the coupling of
alkylzinc reagents with aryl or alkenyl iodides, see: (f) K.
Okura and E. Shirakawa, Eur. J. Org. Chem., 2016, 3043–
3046.
3
Uchiyama and coworkers have reported the transition metal-
free coupling of arylmetals with aryl halides. For the coupling
of diarylzinc reagents, see: H. Minami, X. Wang, C. Wang
and M. Uchiyama, Eur. J. Org. Chem., 2013, 7891–7894. For
the coupling of arylalminum reagents, see: H. Minami, T.
Saito, C. Wang and M. Uchiyama, Angew. Chem., Int. Ed.,
2015, 54, 4665–4668. Very recently, Zhang, Wnuk and
coworkers have reported the transition metal-free coupling of
tetraarylstannanes with aryl halides, see: Q. He, L. Wang, Y.
Liang, Z. Zhang and S. F. Wnuk, J. Org. Chem., 2016, 81,
9422–9427.
4
Triarylphosphines are used as indispensable additives to
obtain α-arylpropargyl alcohols through iodine–zinc
exchange between an alkynyl iodide and diethylzinc followed
by addition of the resulting alkynylzinc species to an aromatic
aldehyde. Phosphines are considered to have acceleration
effects both on the former iodine–zinc exchange step and the
latter addition step, though how they work is not clarified. E.
E. Wilson, A. G. Oliver, R. P. Hughes and B. L. Ashfeld,
Organometallics, 2011, 30, 5214–5221.
5
For preparation of bisalkynylzincs by treatment of terminal
alkynes with diethylzinc, see: O. Yu. Okhlobystin and L. I.
Zakharkin, J. Organomet. Chem., 1965, 3, 257–258. This
method to prepare bisalkynylzincs is often used for the
asymmetric addition of alkynylzinc reagents to aldehydes.
For an early example, see: S. Niwa and K. Soai, J. Chem.
Soc., Perkin Trans. 1, 1990, 937–943.
6
7
The complete retention of the stereochemistries has been
observed also in the previous SET-induced coupling reactions
of alkenyl halides, supporting no involvement of alkenyl
radical intermediates, see refs. 2c–f.
From the result shown in Scheme 2, treatment of
phenylacetylene (1a) with Et2Zn for 10 h at 110 °C is
considered to be sufficient to convert its acetylenic proton to
zinc to give B and C in entries 2 and 3 of Table 3,
respectively.
8
The reaction using 1a (1.6 equiv), BuLi (1.5 equiv), ZnCl2
(1.5 equiv) and 2a (1 equiv) in the absence of phosphine L
did not proceed at all, showing that acceleration of the
transformation of Et–Zn moieties to RC≡C–Zn is not, at least,
the main role of L in the standard procedure. On the other
hand, the reaction using 1a (1.6 equiv), BuLi (1.5 equiv),
ZnCl2 (0.75 equiv) and 2a (1 equiv) in the presence of
4 | J. Name., 2012, 00, 1-3
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