Being selective: The catalyticallylation of α,β‐unsaturated aldehydes with allyltrichlorosilane in the presence of chiral 3,3′‐unsymmetrically substituted bis(tetrahydroisoquinoline) N,N‐dioxides was explored. The allylation of various aldehydes proceeded under mild reaction conditions (−78 °C) with high yields and enantioselectivity (see scheme). This allylation was applied in the synthesis of (