Furans asymmetric hydrogenation

In the heterocyclic series several heteroarylalanines have been obtained by asymmetric hydrogenation using chiral homogeneous catalysts. For example, replacement of the phenyl ring by furan, thiophene, selenophene, pyridine, or indole yields fiirylalanines, thienyManines, 2- and 3-selenienyManines,... 

Recent advances in asymmetric hydrogenation of heteroaromatic compounds (quinoxaline, pyridine, and furan derivatives) 05CJO634. 

Previously, only a handftil of reports have demonstrated asymmetric hydrogenation of mono-substituted furans, with limited scope and enantioselectivities. In a new study (14AGE8751), a Ru(II) complex bearing the chiral N-heterocyclic carbene ligand SINpEt was employed to successfully hydrogenate disubstituted furans to chiral tetrahydrofu-rans. In the case of 2,4-disubstituted furans, products were obtained with excellent enantio- and diastereoselectivity.The cis isomer was the major product. 

The application of immobilized heterobimetallic cobalt-rhodium in nanoparticles has also been reported. In the presence of water, CO, and amine, internal acetylenes 119 were converted to 3,4-disubstituted furan-2(5H)-ones 120 and 121 in high yields, in which an amine was necessary for the formation of furanone and a higher CO pressure was required for good yield (Equation (8)). It is important to notice that the catalyst has been easily recovered without loss of activity or formation of hydrogenated side-products. The reaction proceeded in good yield for the symmetric substrates (entries 1 and 2) while it always gave two regioisomers for asymmetric alkyne substrates (entries 3-8). The isomer ratio was dependent on the steric and electronic nature of the substituents. 

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