pubs.acs.org/joc
Highly Chemo- and Regioselective Reduction of Aromatic Nitro
Compounds Using the System Silane/Oxo-Rhenium Complexes
†
Rita G. de Noronha, Carlos C. Romao, and Ana C. Fernandes*
†
,‡
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†
´
Instituto de Tecnologia Quımica e Biologica, Universidade Nova de Lisboa, Av. da Repuꢀblica - EAN, 2781-
157 Oeiras, Portugal, and Centro de Quımica Estrutural, Complexo I, Instituto Superior Tecnico, Av.
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‡
´
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Rovisco Pais, 1049-001 Lisboa, Portugal
Received May 8, 2009
The reduction of aromatic nitro compounds to the corresponding amines with silanes catalyzed by
high valent oxo-rhenium complexes is reported. The catalytic systems PhMe2SiH/ReIO2(PPh3)2
(5 mol %) and PhMe2SiH/ReOCl3(PPh3)2 (5 mol %) reduced efficiently a series of aromatic nitro
compounds in the presence of a wide range of functional groups such as ester, halo, amide, sulfone,
lactone, and benzyl. This methodology also allowed the regioselective reduction of dinitrobenzenes
to the corresponding nitroanilines and the reduction of an aromatic nitro group in presence of an
aliphatic nitro group.
Introduction
sodium borohydride/catalyst,2 hydrazine/catalyst,3 and
metals such as iron, tin, or zinc.4 Over the last years, a
variety of other chemical systems such as Mo(CO)6/DBU,5
Pd(OAc)2/PMHS,6 Sm/I2,7 Sm/1,10-dioctyl-4,40-bipyridi-
nium dibromide,8 Sm/NH4Cl,9 Cu nanoparticles/
HCOONH4,10 S8/NaHCO3,11 and HI12 have been reported.
Enzymatic reduction of aromatic nitro compounds with
molybdoenzymes is believed to proceed by oxygen atom
transfer from the nitrogen center to the MoIVO center of
the enzyme. The MoVIO2 center thus formed is then regen-
erated by one of a variety of physiological reducing agents
via coupled electron-proton transfers.13
The selective reduction of aromatic nitro compounds is a
useful reaction for the synthesis of amines, important inter-
mediates in the production of many pharmaceuticals, agro-
chemicals, dyes, polymers, photographic and rubber
materials, and chelating agents.
Numerous methods have been developed to accomplish
this transformation including catalytic hydrogenation,1
*To whom correspondence should be addressed. Tel: 351 218419388. Fax:
351 218464457.
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Published on Web 08/17/2009
DOI: 10.1021/jo9008657
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2009 American Chemical Society