Ni-Catalyzed Borylative Diene−Aldehyde Coupling: The Remarkable Effect of P(SiMe3)3
摘要:
The nickel-catalyzed reaction of carbonyls and dienes was accomplished in a regio- and stereoselective fashion employing a stoichiometric amount of bis(pinacolato)diboron. In the presence of P(SiMe3)(3), this reductive coupling furnishes allyl boronic esters which are regioisomeric to those obtained with PCy3 as the ligand. The coupling product may be subject to oxidation, which furnishes the derived 1,3-diol, or allytation with an additional aldehyde, which furnishes the derived 1,6-diol in a stereoselective fashion.
dialkoxyboranes derived from thioesters were found to be stereoconvergent: both Z and E enolates give syn aldol condensation products. The thioester additions to chiral aldehydes were studied. Internal selectivity (syn) was usually very high, while the relative stereoselectivity ranged from poor to good, depending on the specific aldehyde used. The aldol products were transformed to known compounds for correlation