Styrenes partial reduction

Phenoxy acetophenone, 46, 94 Phenylacetyleue, oxidative coupling to diphenyldiacetylene, 46, 39 partial reduction to styrene using palladium catalyst, 46, 90 reaction with sodium hypobromite to yield phenylbromoethyne, 46,86... 

Partial Reduction of Enones, Styrenes and Related Systems... 

The hydrogenation of alkenes conjugated to aromatic systems is usually much less difficult than partial reduction of polyenes, as the aromatic ring is less susceptible to reduction. Many catalysts of Group 10 metals have been used for this transformation, including Raney nickel, Pd adsorbed on carbon, Pd adsorbed on calcium carbonate, Pd on barium sulfate, metallic palladium, PtOa, chloroplatinic acid or platinum metal. Normally, the stereochemistry of the reduced product arises from syn addition of a hydrogen molecule to the less-hindered face of the double bond, as exemplified in the catalytic hydrogenation of a steroidal styrene over metallic palladium (Scheme 93). ... 

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