Phosphorus-based catalysts sulfidation

Fusion of the base 306 with l,2,3,5-tetra-0-acetyl-/3-D-ribofuranose (307) in the presence of I2 catalyst gave a mixture of nucleosides (308-311) in low yields. Better yields were obtained by thionation with phosphorus penta-sulfide of the oxo derivatives, 4-(2, 3, 5 -tri-0-acetyl-/3-D-ribouranosyl)-... 

Theories and principles of the characterization techniques are not described here. For consistenc), all the catatysts described in this review are referred to with the same nomenclature, although a different nomenclature is sometimes used in the cited publications. Each catalyst component (element) separated by the symbol indicates the sequence of its introduction into the catalyst formulation from right to left. Those separated by the symbol 7 between right and left belong to the support material and the elements on the support, respectively. For example, NiMo-P/Al refers to a catalyst prepared such that the phosphorus-containing precursor is loaded on the alumina support first, followed by nickel and molybdenum, which are introduced simultaneously. CoMo/Al — P refers to a catalyst in which cobalt and molybdenum are introduced simultaneously onto an alumina support doped with phosphorus-containing species. Each element may represent its oxide or sulfide forms. In all cases, A1 refers to the alumina-based support or to its hydroxide precursor. 

This catalyst is a very attractive industrial catalyst because of its low cost compared to platinum. However it is also well known to cause extensive dehalogenation during the hydrogenation of halonitroaromatics (ref. 14). Numerous methods have been employed to overcome this problem including modification of the nickel catalyst by adding base (ref. 15) phosphorus (ref. 16), amines (refs. 17, 18) and various sulfided additives (refs. 19, 20). 

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