Enantioselective Hydrogenation of Unsaturated Acid and Ester Derivatives

Enantioselective Hydrogenation of Unsaturated Acid and Ester Derivatives 

The enantioselective hydrogenation of a,fj- or / ,y-unsaturated acid derivatives and ester substrates including itaconic acids, acrylic acid derivatives, buteno-lides, and dehydrojasmonates, is a practical and efficient methodology for accessing, amongst others, chiral acids, chiral a-hydroxy acids, chiral lactones and chiral amides. These are of particular importance across the pharmaceutical and the flavors and fragrances industries. 

Substrate Ligand SCR Reaction conditions a) TON TOF [h-1] % ee (config.) Refer- ence(s) 

One method of accessing chiral alcohols is through the enantioselective hydrogenation of the corresponding enol acetates. Despite this substrate class having similar structures to enamides, far fewer successful examples of this reaction 

Catalyst performance was far superior to the corresponding BINAP or Me-Du-Phos systems, with both conversions and selectivities being higher. The hydrogenation of enol ethers using Rh-PennPhos catalysts has been reported in a patent by Zhang [67d]. Under mild conditions, high enantioselectivities were obtained (73-94% ee) for 1-aryl-l-methoxy-ethene derivatives 121, compared to Me-DuPhos (40-73% ee) and BINAP (46-48% ee). 

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