Ruthenium-catalyzed hydrogenation allylic alcohols

Liang T, Nguyen KD, Zhang W, Krische MI (2015) Enantioselective ruthenium-catalyzed carbonyl allylation via alkyne-alcohol C-C bond forming transfer hydrogenation aUene hydrometallation vs. oxidative coupling. J Am Chem Soc 137 3161-3164... 

More recently, using the cyclometallated iridium C,(7-benzoate derived from allyl acetate, 4-methoxy-3-nitrobenzoic acid and BIPHEP, catalytic carbonyl crotylation employing 1,3-butadiene from the aldehyde, or alcohol oxidation was achieved under transfer hydrogenation conditions [274]. Carbonyl addition occurs with roughly equal facility from the alcohol or aldehyde oxidation level. However, products are obtained as diastereomeric mixtures. Stereoselective variants of these processes are under development. It should be noted that under the conditions of ruthenium-catalyzed transfer hydrogenation, conjugated dienes, including butadiene, couple to alcohols or aldehydes to provide either products of carbonyl crotylation or p,y-enones (Scheme 16) [275, 276]. 

Asymmetric hydrogenation of allylic alcohols (14, 39-40).1 Mammalian dol-ichols (2) are terminal dihydropolyisoprenols which are involved in glycoprotein synthesis. They contain one terminal chiral primary allylic alcohol group. The polyprenols 3 present in plants correspond to dolichols except that they lack the terminal double bond considered to be (Z). They can be obtained by hydrogenation of 2 catalyzed by (bistrifluoroacetate)ruthenium(II) and (S)-l, which affects only the terminal double bond to provide (S)-3 in >95% ee. 

Ruthenium(binap) complexes effectively catalyze asymmetric hydrogenation of a-amidocinnamic acids [172], allylic alcohols [173] and acrylic acids with almost quantitative enantiomeric excess [174]. For example, one of the largest-selling anti-inflammatory agents, Naproxen should be supplied as the enantiomerically pure 5-isomer, because the R-isomer is expected to be toxic to the liver. Asymmetric hydrogenation of the precursor by RuCL[(5)- binap] produces 5-Naproxen with 96-98 % ee (eq (47)) [175-176]. 

Shibahara F, Bower JF, Krische MJ (2008) Ruthenium-catalyzed C-C bond forming transfer hydrogenation carbonyl allylation from the alcohol or aldehyde oxidation level employing acyclic 1,3-dienes as surrogates to preformed allyl metal reagents. J Am Chem Soc 130 6338-6339... 

The first hydration step was promoted by Bronsted acids containing weakly or noncoordinating anions. In the second step, an intramolecular hydrogen transfer in the secondary alcohol was catalyzed by ruthenium(III) salts with chelating bipyridyl-type ligands. The possible complexation of the latter with the diene did not inhibit its catalytic activity in the allylic rearrangements, under acid-catalyzed hydration conditions. 

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