Asymmetric Allylation of Acylhydrazones

Significance

A urea-catalyzed enantioselective allylation of acylhydrazones 2 using organometallic reagents is described. The corresponding homoallylic amines 3 are formed in very good enantio­selectivities. However, the diastereomeric ratios are low if 1-bromobut-2-ene (1, R = Me) based organometallic reagents are used. The bifunctional nature of the catalyst and the close proximity of the two functionalities turned out to be crucial for the realization of high enantiomeric ratios. The urea motif is assumed to activate the hydrazone 2 via hydrogen bond formation, whereas the Lewis basic sulfinamide activates the organometallic nucleophile.