ChemInform Abstract: Catalytic Use of Chiral Phosphine Ligands in Asymmetric Pauson—Khand Reactions.
Abstract
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ChemInform Abstract
The first example of catalytic asymmetric syntheses of 2-cyclopentenone systems by intramolecular Pauson—Khand reaction of 1,6-enynes using catalytic amounts of Co2(CO)8 and chiral phosphine ligand are reported. From several tested ligands, (S)-BINAP is found to be the most effective. The presence of a methyl group in the alkynyl or alkenyl part results in a remarkable decrease of the enantiocontrol of the reaction, whereas 1,6-enynes (Ia) and (IVa) without methyl groups provide excellent enantioselectivities. The enantioselectivities obtained in the reaction of ketal (VIII) or in the intermolecular reaction of norbornene with phenylacetylene are only low (<10%).
