The attempted Baylis–Hillman reactions of N-tosyl aldimines and aryl aldehydes with 3-methylpenta-3,4-dien-2-one gave the corresponding Baylis–Hillman adducts 3 and 6 in moderate to good yields in the presence of DMAP in DMSO, respectively. In the case of the aza-Baylis–Hillman reactions of N-tosyl aldimines with 3-methylpenta-3,4-dien-2-one catalyzed by PBu₃, the corresponding aza-Baylis–Hillman derivatives 4 and 5 were formed at the same time.