Adams catalyst stereochemistry

Piperidine-type metacyclophane alkaloids have four chiral carbon atoms C-3, C-5, C-9, and C-ll. With 96 in hand, Fujita et al. hydrogenated its pyridine ring over Adams catalyst and Raney nickel in order to define the relative stereochemistry of C-5 and C-9. They obtained a single crystalline hexahydro derivative in quantitative yield. Catalytic hydrogenation of substituted pyridines generally results in cis products. Therefore, one can assume the cis relationship of C-5 and C-9 hydrogens in the foregoing... 

Most of the studies to date have employed either palladium [222—229] or platinum [220,224,226,228—235], commonly as Adams reduced platinum oxide, although nickel [228,236,237], rhodium [238,239], ruthenium [239], iridium [239], iron [237] and tungsten [237] have also been used. Many of these studies have been concerned with the stereochemistry of the hydrogenation of disubstituted cycloalkenes. Table 32 shows some typical results for the platinum- and palladium-catalysed hydrogenation of disubstituted cyclohexenes. Table 33 shows comparative results for the hydrogenation of 1,4-dialkylcyclohexenes over palladium, platinum and rhodium catalysts. 

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