Palladium catalyst for partial reduction OF ACETYLENES

Palladium catalyst for partial reduction OF ACETYLENES, 46, 89 Palladium on charcoal, catalyst for reductive methylation of ethyl p-. nitrophenylacetate, 47, 69 in reduction of /-butyl azidoacetate to glycine /-butyl ester, 46, 47 Palladium oxide as catalyst for reduction of sodium 2-nltrobenzene-sulfinate, 47, 5... 

Lindlar, H. Dubuis, R. Palladium catalyst for partial reduction of acetylenes. Org. Synth. 1973, J, 880-882. 

Epoxides are normally hydrogenated in preference to saturated ketones but double bonds are usually reduced under these conditions. It is possible in some cases to selectively cleave an epoxide without saturating double bonds by the use of the deactivated catalysts recommended for the partial reduction of acetylenes (see section IV) or by the addition of silver nitrate to the palladium-catalyzed reaction mixture. " ... 

Palladium catalysts are more often modified for special selectivities than platinum catalysts. Palladium prepared by reduction of palladium chloride with sodium borohydride Procedure 4, p. 205) is suitable for the reduction of unsaturated aldehydes to saturated aldehydes [i7]. Palladimn on barium sulfate deactivated with sulfur compounds, most frequently the so-called quinoline-5 obtained by boiling quinoline with sulfur [34], is suitable for the Rosenmund reduction [i5] (p. 144). Palladium on calcium carbonate deactivated by lead acetate Lindlar s catalyst) is used for partial hydrogenation of acetylenes to cw-alkenes [36] (p. 44). 

The preparation of Lindlar s catalyst (palladium on calcium carbonate moderated by treating with lead acetate and quinoline)31 has been described in detail it is used for effecting the partial reduction of an acetylenic bond to an olefin. 

An acetylene may be reduced to an olefin by sodium in liquid ammonia, ° by electrolytic reduction at a spongy nickel cathode, or by partial hydrogenation over metal catalysts. Catalysts for the hydrogenation include nickel, ° iron, colloidal palladium, and palladium on barium sulfate or calcium carbonate. Pure trans olefins are obtained from dialkylacetylenes by reduction with sodium in liquid ammonia. The yields ate better than 90%. Catalytic hydrogenation leads to mixtures of cis and trans olefins in which the cis isomers predominate. ° Mono- and di-arylacetylenes have also been reduced. ... 

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