Asymmetric synthesis of enantiomerically highly enriched compounds ideally with a chiral catalyst is fundamental to providing pharmaceutically active compounds for medicinal applications. In this lecture our recent work will be outlined on asymmetric, phosphoric acid-catalyzed reactions of various resonance-stabilized benzyl cations to access a plethora of benzannulated oxygen and nitrogen heterocycles with remarkable efficiency and selectivity.[1] Scope and limitations of this strategy as well as mechanistic aspects will be discussed in detail. In the second part of the lecture an unprecedented Umpolung strategy with resonancestabilized 1-azallyl cations will be presented which furnishes 1,4-(hetero)dicarbonyl compounds. With the use of sterically confined, chiral silylium ion catalysts at very low catalyst loadings highly valuable products carrying up to two new stereogenic centers have been obtained with excellent yields and diastereoselectivity and up to 99:1 e.r. Detailed kinetic, spectroscopic and theoretical studies reveal mechanistic details of this process. In addition, they have been shown to be ideal precursors to medicinally active compounds.[2]