The asymmetric hydrogenation of furans and benzofurans is challenging.  
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Asymmetric hydrogenation of thiophenes and benzothiophenes has been catalyzed by some ruthenium(II) complexes of N-heterocyclic carbenes (NHC). This system appears to possess superb selectivity (ee > 90%) and perfect diastereoselectivity (all cis) if the substrate has a fused (or directly bound) phenyl ring but yields only racemic product in all other tested cases.
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