Indium (low valent)
Low-valent metal compounds are commonly used as reducing agents. With its most stable oxidation state as 3+, indium is used in the 2+ oxidation state as an one-electron reducing agent. Indium hydrides such as InCl2H, generated from readily available Et3SiH or NaBH4 and InCl3, offer mild conditions and low toxicity, and are therefore promising alternatives to Bu3SnH.
Recent Literature
An Et3SiH-promoted diastereoselective reductive aldol
reaction has been developed using InBr3 as a catalyst. This
three-component reaction afforded only silyl aldolates as products
without any side reactions.
I. Shibata, H. Kato, T. Ishida, M. Yasuda, A. Baba, Angew. Chem.,
2004, 116, 729-732.
The In(OAc)3-catalyzed reaction of bromo- and iodoalkanes with PhSiH3
in THF at 70 C gave dehalogenated alkanes in good to high yields in the presence
of Et3B and air. 2,6-lutidine as additive enabled an efficient
reduction of simple and functionalized iodoalkanes in EtOH. GaCl3 was
found to be an effective catalyst for the reduction of haloalkanes with
poly(methylhydrosiloxane).
K. Miura, M. Tomita, Y. Yamada, A. Hosomi, J. Org. Chem., 2007,
72, 787-792.
A direct reduction of alcohols to the corresponding alkanes using
chlorodiphenylsilane as hydride source in the presence of a catalytic amount
of InCl3 showed high chemoselectivity for benzylic alcohols,
secondary alcohols and tertiary alcohols while not reducing primary alcohols and
functional groups that are readily reduced by standard methods such as esters, chloro, bromo,
and nitro groups.
M. Yasuda, Y. Onishi, M. Ueba, T. Miyai, A. Baba, J. Org. Chem.,
2001, 7741-7744.
The generation of indium hydride (Cl2InH) by transmetalation of
InCl3 with Et3SiH has been reported.
N. Hayashi, I. Shibata, A. Baba, Org. Lett., 2004, 6, 4981-4983.
N. Hayashi, I. Shibata, A. Baba, Org. Lett., 2004, 6, 4981-4983.
N. Hayashi, I. Shibata, A. Baba, Org. Lett., 2004, 6, 4981-4983.
Dichloroindium hydride (Cl2InH) generated in situ from the
combination of a catalytic amount of indium(III) chloride and sodium borohydride
in acetonitrile reduces activated vic-dibromides to the corresponding (E)-alkenes
in excellent yields.
B. C. Ranu, A. Das, A. Hajira, Synthesis, 2003, 1012-1014.
B. C. Ranu, A. Das, A. Hajira, Synthesis, 2003, 1012-1014.
A novel, convenient and stereoselective synthesis of trisubstituted E-alkenones
has been achieved by InCl3-mediated chemoselective reduction of Baylis-Hillman
adducts with NaBH4 as reductant.
B. Das, J. Banerjee, N. Chowdhury, A. Majhi, H. Holla, Synlett, 2006,
1879-1882.
The use of Et3SiH leads to fewer side reactions in the
intramolecular cyclization of enynes when compared to the NaBH4-InCl3
system reported previously.
N. Hayashi, I. Shibata, A. Baba, Org. Lett., 2004,
6, 4981-4983.
An indium(III) hydroxide-catalyzed reaction of carbonyls and
chlorodimethylsilane afforded the corresponding deoxygenative chlorination
products. Ester, nitro, cyano, or halogen groups were not affected during
the reaction course. Typical Lewis acids such as TiCl4, AlCl3,
and BF3ˇOEt2 showed no catalytic activity. The
reaction mechanism is discussed.
Y. Onishi, D. Ogawa, M. Yasuda, A. Baba, J. Am. Chem. Soc., 2002,
124, 13690-13691.
Organic azides are easily and chemoselectively reduced to the corresponding amines by reaction
with dichloroindium hydride under very mild conditions. γ-Azidonitriles
give pyrrolidin-2-imines in an outstanding
cyclization.
L. Benati, G. Bencivenni, R. Leardini, D. Nanni, M. Minozzi, P. Spagnolo, R.
Scialpi, G. Zanardi, Org. Lett., 2006,8, 2499-2502.
L. Benati, G. Bencivenni, R. Leardini, D. Nanni, M. Minozzi, P. Spagnolo, R.
Scialpi, G. Zanardi, Org. Lett.,
2006, 8, 2499-2502.
Sulfoxides and aza-aromatic N-oxides were deoxygenated using a system
of indium and pivaloyl chloride at room temperature to give the
corresponding sulfides and aza-aromatics in high yields.
E. S. Park, S. Hwan, Lee, J. H. Lee, H. J. Rhee, C. M. Yoon, Synthesis, 2005, 3499-3501.
E. S. Park, S. Hwan, Lee, J. H. Lee, H. J. Rhee, C. M. Yoon,
Synthesis, 2005, 3499-3501.
