Iridium-catalyzed cascade decarbonylation/highly enantioselective Pauson–Khand-type cyclization reactions

An easily accessible chiral iridium-BINAP complex can effect the cooperative processes of decarbonylation of an aldehyde and cascaded enantioselective Pauson–Khand-type reaction. A survey of ligands revealed that atropisomeric aryl-diphosphine ligands were superior to chiral alkyl-diphosphines in this dual catalysis. Applying the reaction conditions of [IrCl(COD)]2/(S)-BINAP complex with nonylaldehyde as a CO surrogate at 100 °C in anhydrous dioxane solvent, various 1,6-enynes were transformed to the corresponding optically active bicyclic cyclopentenones with excellent enantioselectivities (up to 98% ee).

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2-(3-Methoxyphenyl)-7-oxabicyclo[3.3.0]oct-1-en-3oneC14H14O3[α]D25=+26.3 (c 0.11, CH2Cl2)

2-(4-Methylphenyl)-7-oxabicyclo[3.3.0]oct-1-en-3oneC14H14O2[α]D25=+60.9 (c 0.10, CH2Cl2)