Divergent Reactions for Racemates: Catalytic, Enantioselective, and Regiodivergent Nitroso Diels–Alder Reactions

Two products out of eight possible isomers are obtained from the [CuPF6(MeCN)4]-catalyzed, highly enantioselective, and regiodivergent nitroso Diels–Alder reactions of 6-substituted 1,3-cyclohexadienes (see scheme; R=phenyl, alkyl; Ar=2-pyridyl). These divergent reactions of racemic cyclohexadienes deliver valuable compounds for the synthesis of biologically interesting carbasugars. In a first application peracetylated 2-epi-validamine was synthesized.