Nanocomposites and nanomaterials

Creation of selective catalysts for "sensitive" heterocyclic compounds hydrogenation on the basis of nanostructured Re2S7 
Kolotilov S. V.,1,2 Subbotin V. V.,3 Lytvynenko A. S.,1 Ryabukhin S. V.,2,3 Volochnyuk D. M. 2,3,4
1 L.V. Pisarzhevskii Institute of Physical Chemistry of the NAS of Ukraine. Prospect Nauki, 31, Kyiv, 03028, Ukraine. 
E-mail: s.v.kolotilov@gmail.com
2 National Taras Shevchenko University of Kyiv, 60 Volodymyrska str., Kyiv, 01033, Ukraine
3 Enamine Ltd, 78 Chervonotkatska str., Kyiv 02660, Ukraine
4 Institute of Organic Chemistry of the National Academy of Sciences of Ukraine, Murmanska str., 5, Kyiv, 02000, Ukraine

Selective hydrogenation of heterocyclic compounds, containing C-I and C-Br bonds, or "sensitive" molecules like thiophenes, is extremely attractive task of fine organic chemistry, in view of wide use of the saturated heterocyclic compounds in MedChem applications. In this study the Re2S7/C composites were prepared (5, 10 and 30 % of Re2S7) and their catalytic activity in hydrogenation of quinoline, iodo- and bromoquinolines, a series of substituted thiophenes was studied. The composites were characterized by SEM, TEM, powder XRD and low temperature N2 adsorption. It was found that Re2S7 formed amorphous plate-like particles on the surface of carbon. 
The composites were active in the processes of quinoline hydrogenation and could be considered as an alternative to Pd- and Pt-containing catalysts. Degradation of the composite at presence of water in the reaction mixture was observed. Complete hydrogenation of quinoline was achieved at 50 °C and 30 atm of H2 at n(Re):n(quinoline) = 0.047 ratio in methanol. Hydrogenation of Br and I-containing quinolines could be performed without C-Hal bond cleavage, in particular hydrogenation of 5-ionoquinoline at Re2S7/C composite led to 5-iodo-1,2,3,4-tetrahydroquinoline with ca. 30 % preparative yield (1 g scale). The reaction pathway was evaluated by DFT calculations.
Hydrogenation of 2-phenylthiophene at presence of Re2S7/C composite gave 95 % yield of 2-phenyltetrahydrothiophene, while introduction of the substituents led to significant reduction of the yield.