The nickel-catalyzed reaction of aromatic amides that contain an 8-aminoquinoline as a directing group with bicyclic alkenes, such as norbornene and 1,4-dihydro-1,4-epoxynaphthalene, results in the cleavage of both the C−H bond at the ortho-position of the benzene ring and the C(O)−N bond to give methanofluoren-9-one and 1,4-epoxyfluoren-9-one derivatives. Both Ni(OTf) 2 and Ni(cod) 2 show a high catalytic activity. The presence of AgOAc is essential for the reaction to proceed. In the meta-substituted aromatic amides, a less hindered C−H bond is exclusively functionalized.
The deracemization of racemic amines to yield enantioenriched amines using S‐stereoselective amine oxidases (AOx) has recently been attracting attention. However, R‐stereoselective AOx that are suitable for deracemization have not yet been identified. An R‐stereoselective AOx was now evolved from porcine kidney D‐amino acid oxidase (pkDAO) and subsequently use for the deracemization of racemic amines. The engineered pkDAO, which was obtained by directed evolution, displayed a markedly changed substrate specificity towards R amines. The mutant enzyme exhibited a high preference towards the substrate α‐methylbenzylamine and was used to synthesize the S amine through deracemization. The findings of this study indicate that further investigations on the structure–activity relationship of AOx are warranted and also provide a new method for biotransformations in organic synthesis.
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