Hydrogenation and Hydrogenolysis. XVII. The Selectivities of Platinum Group Metals in Catalytic Hydrogenation of 2-Naphthol and Tetrahydro-2-naphthols

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Abstract
Catalytic hydrogenation of 2-naphthol (NL) with the six platinum metals has been studied in t-BuOH at 80 °C and 4–5 MPa H2 pressure. Selectivities for formation of 1,2,3,- and 5,6,7,8-tetrahydro-2-naphthols (ac- and ar-TLs) have been determined by application of a kinetic equation. ar-TL was formed more predominantly than ac-TL over all the metals. The hydrogenation of ac- and ar-TLs has also been studied under the same conditions for comparison. The hydrogenation of NL and ar-TL was accompanied by extensive hydrogenolysis to give decalins over Os, Ir, and Pt, whereas the hydrogenolysis occurred only slightly over Ru, Rh, and Pd. In general the hydrogenolysis occurred to much lesser extents with ac-TL. The amounts of 2-decalone formed in hydrogenation of ar-TL have been determined by application of the kinetic equation. The 2-decalone was the cis isomer only except with Pd. For formation of the cis products at the ring juncture, hydrogenation of ar-TL was highly stereoselective with Ru, Rh, Os, and Ir, while hydrogenation of ac-TL was the most stereoselective with Os and Ir. The course of hydrogenolysis and the stereochemistry of hydrogenation are discussed from the comparative results on NL, ar-TL, and ac-TL.

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