Two catalytic processes namely, palladium catalysis and Brønsted acid catalysis, lead to different alkylation products in the addition of alkoxyallenes to pyrazolones. In their Communication on
nie.201610473" rel="references:https://doi.org/10.1002/anie.201610473">page 1077, G. Jiang et al. demonstrate how Pd catalysis provides branched allylic pyrazol-5-ones under mild conditions, whereas a chiral Brønsted acid catalyst gives the linear addition products.