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Asymmetric Copper-Catalyzed Hydroamination of Aryl Alkynes
Copper-Catalysed Selective Hydroamination Reactions of Alkynes.
Nature Chem. 2015;
16 February 2015 (online)
A new asymmetric synthesis of alkyl amines from readily available alkynes and electrophilic amine sources proceeds under mild conditions with high levels of regio- and stereocontrol. The regiochemistry of the initial hydrocupration reaction depends on the structure of the alkynes. Aryl alkynes display Markovnikov addition, whereas alkyl alkynes give anti-Markovnikov addition.
When the hydroamination reaction is performed in the absence of a proton source such as i-PrOH or EtOH, enamine intermediates (not shown) are isolated in good yield (5 examples). Catalytic cycles for the enamine formation (direct hydroamination) and the reductive hydroamination reactions are proposed. A synthesis of rivastigmine exemplifies the value of the method.