DOI: 10.1002/adsc.201000191 Highly Chemo- and Regioselective Reduction of Aromatic Nitro Compounds Catalyzed by Recyclable Copper(II) as well as Cobalt(II) Phthalocyanines Upendra Sharma, a Praveen Kumar, a Neeraj Kumar, a, * Vishal Kumar, a and Bikram Singh a, * a Institute of Himalayan Bioresource Technology (Council of Scientific & Industrial Research), Palampur, Himachal Pradesh 176 061, India Fax: (+ 91)-1894-230-433; e-mail: bikram_npp@rediffmail.com or neerajnpp@rediffmail.com Received: March 11, 2010; Revised: June 20, 2010; Published online: August 16, 2010 IHBT Communication No. 1077 Supporting information for this article is available on the WWW under http ://dx.doi.org/10.1002/adsc.201000191. Abstract: Copper/cobalt phthalocyanines were es- tablished for the first time as catalysts for the very efficient chemo- and regioselective reduction of ar- omatic nitro compounds to generate the corre- sponding amines. The selective reduction of nitro compounds was observed in the presence of a large range of functional groups such as aldehyde, keto, acid, amide, ester, halogen, lactone, nitrile and het- erocyclic functional groups. Furthermore, the pres- ent method was found to be highly regioselective towards the reduction of aromatic dinitro com- pounds in a short time with high yields. In most of the cases the conversion and selectivity were > 99% as monitored by GC-MS. The reduction mechanism was elucidated by UV-vis and electrospray ioniza- tion quadrupole time-of-flight tandem mass spec- trometry. Keywords: chemoselectivity; cobalt/copper phthalo- cyanines; hydrazine hydrate; nitro reduction; regio- selectivity Reduction of aromatic nitro compounds to the corre- sponding amines is an important chemical transforma- tion in organic chemistry, mainly due to the fact that amines are important intermediates in the prepara- tion of dyes, herbicides, pesticides, and pharmaceuti- cals. [1] Numerous methods have been developed to ac- complish this transformation including catalytic hy- drogenation, [2] sodium borohydride/catalyst, [3] hydra- zine/catalyst, [4] and metals such as iron, tin, or zinc. [5] Over the last years, a variety of other catalytic sys- tems such as Mo(CO) 6 /DBU, [6] PdACHTUNGTRENNUNG(OAc) 2 /PMHS, [7] Sm/I 2 , [8] Sm/1,1’-dioctyl-4,4’-bipyridinium dibromide, [9] Sm/NH 4 Cl, [10] Cu nanoparticles/HCOONH 4 , [11] S 8 / NaHCO 3 , [12] HI [13] and silane/oxorhenium complexe- s [14a] have been reported. However, most of the syn- thetic methods lack the desired chemoselectivity over other functional groups that are often present in the substrates such as acid, aldehyde, ester, alkene, halide, benzyl, nitrile and, also, the desired regioselec- tivity in the reduction of dinitro compounds. In addi- tion, the reduction of aromatic nitro compounds often stops at an intermediate stage, yielding hydroxyl- ACHTUNGTRENNUNGamines, hydrazines, and azoarenes. Due to the high importance of the selective reduction of aromatic nitro compounds, the search for alternative, efficient and highly chemo- and regioselective methods always remains an important task in organic synthesis. Metal phthalocyanines (MPcs) (Figure 1) are tradi- tionally used as dyes and pigments. [15] Their use has Figure 1. Structure of the metal phthalocyanines. 1834  2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Adv. Synth. Catal. 2010, 352, 1834 – 1840 COMMUNICATIONS