Stereodivergent synthesis of chiral spiropyrazolones through Pd-catalyzed asymmetric sequential hydroalkylation of 1,3-enynes: unusual solvent effects on the enantioselectivity

Abstract

Chiral spiropyrazolones were constructed for the first time through Pd-catalyzed asymmetric sequential hydroalkylation of 1,3-enynes. Through substrate control (by exchanging the position of the double bond and triple bond of 1,3-enyne substrates) and chiral ligand control, four stereoisomers could be obtained with high enantioselectivities. In addition, an interesting solvent effect was observed. The utility of this methodology has been demonstrated by synthesizing a novel type of chiral spiro ligand for enantiodivergent allylation reactions.