Platinum(II) Catalyzed Enantioselective Cycloisomerizations of 3-Hydroxylated 1,5-Enynes

摘要

The enantioselective cycloisomerization of 3-hydroxylated 1,5-enynes into bicyclo[3.1.0]hexanones was investigated by using cyclometalated NHC-platinum phosphoramidite complexes as pre-catalysts. Several new complexes were prepared. They generate cationic, electrophilic PtII species that efficiently promote the cycloisomerization process. Enantiomeric excesses up to 81% were obtained in the reactions of enynes with aryl-substituted alkyne functions (8 examples, 70-81% ee).