Iridium–chiral diphosphine complex catalyzes an enantioselective intramolecular Pauson–Khand-typereaction to give various chiral bicyclic cyclopentenones. The enantioselectivereaction proceeds more smoothly and enantioselectively under a lower partial pressure of carbon monoxide. Moreover, aldehyde can be used as a CO source in the enantioselective carbonylative coupling.
PtCl2-catalyzed cycloisomerization of 1,6-enynes containing a heteroatom substituent at the propargylic position is described. The reactions led to the formation of 1-alkenylbicyclo[3.1.0]hexanes in good to excellent yields or 2-(bicyclo[3.1.0]hex-1-yl)acetaldehydes in moderate yields.
The reaction of 1,6-enynes with formaldehyde in the presence of a cationic Rh(I) catalyst, such as [Rh(cod)2]+OTf−, and a chiral biaryl diphosphine led to asymmetric cyclohydroformylation to produce aldehydes with higher-order structures highly enantioselectively.