Experimental study demonstrates asymmetric amplification in an oxypalladation cascade via heterochiral assembly, indicating high enantioselectivity from low-purity chiral catalysts.
An enantioselective oxypalladation/malononitrile addition cascade reaction of alkyne-tethered malononitriles was reported to synthesize enaminones bearing an all-carbon quaternary center. Using Pd(TFA) 2 /Pyox as a precatalyst, an array of enaminone products were obtained in moderate overall yields, with excellent er (93.5:6.5–99.5:0.5) in solution phase and nearly racemic in solid phase. The usage of 3,5-dinitrobenzoic acid as the nucleophile was proven to be crucial to this significant chiral amplification due to a heterochiral self-assembly of the products through an intermolecular multiple π–π stacking interaction. A strong positive nonlinear effect (NLE) was observed in solution phase, which was further highlighted by the access to an enantiopure enaminone (99.5:0.5 er) even using a partially enantiopure catalyst (54:46 er).
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Zhang et al. (2025) studied this question.
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