Selective hydrogenation of heterocyclic compounds containing C-I and C-Br bonds without halogen atom elimination is an extremely attractive task of fine organic chemistry because saturated heterocyclic molecules with halogen atoms are promising building blocks for 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 bromoquinoline was studied. The composites were characterized by SEM, TEM, powder XRD and low temperature N2 adsorption. It was found that Re2S7 formed as amorphous plate-like particles on the surface of carbon. All composites were active in the processes of hydrogenation of quinoline and Br, I-containing quinolines, the latter compounds could be hydrogenated without C-Hal bond cleavage. Degradation of the catalyst at the 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 6-, 7- and 8-bromoquinolines in the same conditions led to respective bromo-1,2,3,4-tetrahydroquinolines with ca. 50 % yields. 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).

Re sulfide catalysts for selective hydrogenation of iodo- and bromoquinoline

ACS Spring Meeting 2021

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