C O M M U N I C A T I O N S
Scheme 3. Plausible Mechanism
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600–602. (b) Hatakeyama, T.; Kondo, Y.; Fujiwara, Y.; Takaya, H.; Ito,
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in press; DOI: 10.1039/c0cc01216e.
In summary, we have developed an iron-catalyzed Suzuki-
Miyaura coupling of nonactivated alkyl halides with arylboron
compounds. The unique combination of the novel sterically
demanding phosphine ligands and a magnesium cocatalyst enables
the selective coupling reaction in high yield. The relationship
between the spin state of the iron catalyst and its reactivity is being
actively investigated in our group.
Acknowledgment. We thank JSPS and MEXT for financial
support through Grants-in-Aid for Scientific Research on Priority
Areas “Synergistic Effects for Creation of Functional Molecules”
(M. Nakamura, 18064006) and “Chemistry of Concerto Catalysis”
(T. Hatakeyama, 20037033) and Grants-in-Aid for Young Scientists
S, (M. Nakamura, 2075003); B, (T. Hatakeyama, 2175098). T.
Hashimoto is a Research Fellow of the Japan Society for the
Promotion of Science (213169). Financial support from Tosoh
Finechem and Tosoh Corporations as well as the Noguchi Institute
is gratefully acknowledged. We also thank Prof. H. Nagashima
(Kyushu University) and Dr. J. Hong for valuable comments. We
truly appreciate the insightful suggestions provided by the reviewers
during the reviewing process.
(8) FeIIAr2(TMEDA) is supposed to be an active species: Noda, D.; Sunada,
Y.; Hatakeyama, T.; Nakamura, M.; Nagashima, H. J. Am. Chem. Soc.
2009, 131, 6078–6079.
(9) (a) Evans, D. F. J. Chem. Soc. 1959, 2003–2005. (b) Evans, D. F.;
Fazakerley, G. V.; Phillips, P. R. F. J. Chem. Soc. A 1971, 1931–1934. (c)
Crawford, T. H.; Swanson, J. J. Chem. Educ. 1971, 48, 382–386. (d) Grant,
D. H. J. Chem. Educ. 1995, 72, 39–40. (e) Britovsek, G. J. P.; Gibson,
V. C.; Spitzmesser, S. K.; Tellmann, K. P.; White, A. J. P.; Williams, D. J.
J. Chem. Soc., Dalton Trans. 2002, 1159–1171.
(10) See the Supporting Information for details.
(11) Fluoride ion showed a unique modulation effect on the selectivity of iron-
group-metal-catalyzed biaryl cross-coupling reactions (see refs 6o and 6w).
(12) Nickel-catalyzed Suzuki-Miyaura coupling with lithium organoborate: (a)
Kobayashi, Y.; William, A. D.; Mizojiri, R. J. Organomet. Chem. 2002,
653, 91–97. (b) Kobayashi, Y.; William, A. D. Org. Lett. 2002, 4, 4241–
4244.
(13) The reaction of phenylboronic acid pinacol ester with butyl- or tert-
butyllithium proceeded at-40 °C to give the corresponding lithium borate
quantitatively. The lithium borates are tolerant of air but not moisture. See
the Supporting Information for details.
(14) In the presence of the diphoshine ligand, FeCl2, FeCl3, FeF2, and Fe(OEt)2
gave 88, 51, 1, and 0% yield, respectively. The fluoride and alkoxide ions
may interfere with the coupling reaction. See the Supporting Information
for details.
Supporting Information Available: Details of the experimental
procedure, characterization data, and crystallographic data (CIF). This
(15) A similar effect of magnesium salts has been reported in organozinc
coupling: (a) Terao, J.; Todo, H.; Watanabe, H.; Ikumi, A.; Kambe, N.
Angew. Chem., Int. Ed. 2004, 43, 6180–6182. (b) Nakamura, M.; Ito, S.;
Matsuo, K.; Nakamura, E. Synlett 2005, 1794–1798. (c) Ito, S.; Fujiwara,
Y.; Nakamura, E.; Nakamura, M. Org. Lett. 2009, 11, 4306–4309.
(16) Addition of MgBr2 did not affect the NMR spectra of 3a. MgCl2 showed
a comparable acceleration effect (80% yield), while LiBr and ZnBr2 were
not effective at all. See the Supporting Information for details. Magnesium
salts could activate the Fe(II)-X bond of intermediate C (Scheme 3) to
accelerate the transmetalation step (C to A).
(17) Review: (a) Kamigaito, M.; Ando, T.; Sawamoto, M. Chem. ReV. 2001,
101, 3689–3746. Recent papers: (b) Uchiike, C.; Terashima, T.; Ouchi,
M.; Ando, T.; Kamigaito, M.; Sawamoto, M. Macromolecules 2007, 40,
8658–8662. (c) Kawamura, M.; Sunada, Y.; Kai, H.; Koike, N.; Hamada,
A.; Hayakawa, H.; Jin, R.-H.; Nagashima, H. AdV. Synth. Catal. 2009, 351,
2086–2090.
(18) Recombination of B with the alkyl radical (R · ) followed by reductive
elimination of Ar-R from the resulting arylironIV species can be proposed
as an alternative pathway.
(19) Monophosphine of peripheral steric demand: (a) Ohzu, Y.; Goto, K.;
Kawashima, T. Angew. Chem., Int. Ed. 2003, 42, 5714–5717. (b) Ohta,
H.; Tokunaga, M.; Obora, Y.; Iwai, T.; Iwasawa, T.; Fujihara, T.; Tsuji,
Y. Org. Lett. 2007, 9, 89–92.
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(see refs 6h, 6j, 6m, and 6n).
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