ORGANIC
LETTERS
2013
Vol. 15, No. 7
1728–1731
Indium(III) Halide-Catalyzed UV-Irradiated
Radical Coupling of
Iodomethylphosphorus Compounds with
Various Organostannanes
Itaru Suzuki, Kensuke Kiyokawa, Makoto Yasuda, and Akio Baba*
Department of Applied Chemistry, Graduate School of Engineering, Osaka University,
2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
Received February 25, 2013
ABSTRACT
The first catalytic radical coupling of iodomethylphosphorus compounds was accomplished with allyl-, alkenyl-, and allenylstannanes under UV
irradiation in the presence of an indium(III) halide catalyst, for which a transmetalated allylic indium species was confirmed to be an active radical
species.
Iodomethylphosphorus compounds are good candi-
dates for the introduction of bioactive phosphorus moi-
eties into organic compounds.1 Research groups have paid
attention to their potential for organic synthesis.2 However,
few applications to radical coupling have been reported3
because of a radical reactivity that is less than that of iodo-
methylcarbonyl compounds, as discussed by Bazczewski et al.4
In order to address this problem, active radical partners
should be employed for smooth coupling with methyl
phosphonyl radicals. Organostannanes are generally used
as good radical precusors.5 In addition, the application of
organoindiums into radical reactions has recently at-
tracted much attention due to their unique reactivity.6
We have previously developed an equimolar radical
coupling between iodomethylphosphorus compounds and
butenylindium species generated from cyclopropylmethyl-
stannanes and InBr3.7 Herein, we expand the results to the
indium(III) halide-catalyzed reaction of allylic stannanes
with iodomethylphosphorus, in which allylic indiums were
found to be superior radical partners under UV irradiation
by comparison with the corresponding allylstannanes. The
catalytic protocol was also applicable to the introduction of
alkynyl or propargyl moieties into phosphonyl compounds
using either an alkynylstannane or an allenylstannane,
respectively.
(1) Biazas, T.; Szadowiak, A.; Bazczewski, P. Heteroatom. Chem.
2004, 15, 127.
(2) (a) Orsini, F.; Caselli, A. Tetrahedron Lett. 2002, 43, 7255. (b)
Orsini, F.; Lucchi, E. M. Tetrahedron Lett. 2005, 46, 1909. (c) Takahashi,
H.; Inagaki, S.; Yoshii, N.; Gao, F.; Nishihara, Y.; Takagi, K. J. Org.
Chem. 2009, 74, 2794. (d) Wunderlich, S. H.; Knochel, P. Angew. Chem.,
Int. Ed. 2009, 48, 9717.
(3) (a) Bazczewski, P.; Mikozajczyk, M. Synthesis 1995, 392. (b)
Bazczewski, P.; Pietrzykowski, W. M. Tetrahedron 1997, 53, 7291. (c)
Bazczewski, P.; Biazas, T.; Mikozajczyk, M. Tetrahedron Lett. 2000, 41,
3687.
(4) Bazczewski, P.; Biazas, T.; Szadowiak, A. Heteroatom. Chem.
2003, 14, 186.
(5) (a) Grignon, J.; Pereyre, M. J. Organomet. Chem. 1973, 61, C33.
(b) Grignon, J.; Servens, C.; Pereyre, M. J. Organomet. Chem. 1975, 96,
225. (c) Kosugi, M.; Kurino, K.; Takayama, K.; Migita, T. J. Organo-
met. Chem. 1973, 56, C11. (d) Keck, G. E.; Enholm, E. J.; Yates, J. B.;
Wiley, M. R. Tetrahedron 1985, 41, 4079. (e) Danishefsky, S. J.; Panek,
J. S. J. Am. Chem. Soc. 1987, 109, 917. (f) Hanessian, S.; Alpegiani, M.
Tetrahedron Lett. 1986, 27, 4857. (g) Maruyama, K.; Imahori, H.;
Osuka, A.; Takuwa, A.; Tagawa, H. Chem. Lett. 1986, 1719.
(6) (a) Usugi, S.-i.; Tsuritani, T.; Yorimitsu, H.; Shinokubo, H.;
Oshima, K. Bull. Chem. Soc. Jpn. 2002, 75, 841. (b) Takami, K.;
Yorimitsu, H.; Oshima, K. Org. Lett. 2004, 6, 4555. (c) Takami, K.;
Usugi, S. ꢀi.; Yorimitsu, H.; Oshima, K. Synthesis 2005, 824. (d)
Hirashita, T.; Tanaka, J.; Hayashi, A.; Araki, S. Tetrahedron 2005, 46,
289. (e) Hirashita, T.; Hayashi, A.; Tsuji, M.; Tanaka, J.; Araki, S.
Tetrahedron 2008, 64, 2642. (f) Inoue, K.; Sawada, A.; Shibata, I.; Baba,
A. J. Am. Chem. Soc. 2002, 124, 906. (g) Hayashi, N.; Shibata, I.; Baba,
A. Org. Lett. 2005, 7, 3093.
(7) Kiyokawa, K.; Suzuki, I.; Yasuda, M.; Baba, A. Eur. J. Org.
Chem. 2011, 2163.
r
10.1021/ol4005257
Published on Web 03/21/2013
2013 American Chemical Society