Chiral Auxiliary Approach for Gold(I)-Catalyzed Cyclizations
Andrea Cataffo1,2, Miguel Peña-López1,2, Riccardo Pedrazzani1,2
1Institute of Chemical Research of Catalonia (ICIQ), CERCA, Barcelona Institute of Science and Technology, Av. Països Catalans 16, 43007, Tarragona, Spain.
Abstract:
Two different classes of stereoselective cyclizations have been developed using a chiral auxiliary approach with commercially available [JohnPhosAu(MeCN)SbF6 ] as catalyst. First, a stereoselective cascade cyclization of 1,5-enynes was achieved using the Oppolzer camphorsultam as chiral auxiliary. In this case, a one-pot cyclization-hydrolysis sequence was developed to directly afford enantioenriched spirocyclic ketones. Then, the stereoselective alkoxycyclization of 1,6-enynes was mediated by an Evans-type oxazolidinone. A reduction-hydrolysis sequence was selected to remove the auxiliary to give enantioenriched β-tetralones. DFT studies confirmed that the steric clash between the chiral auxiliary and alkene accounts for the experimentally observed diastereoselective cyclization through the Si face.
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