I. Introduction 733 II. Silicon Lewis Acids: Synthesis, Storage, and Solvent Compatibility 734 III. Lewis Acidity of Silicon Derivatives 735 IV. Principles of Action of SLA 737 V. Reactions of Acetals with Nucleophiles 737 A. Reactions with Enol Ethers 738 B. Reactions with Allylic Reagents 740 C. Reactions with Other Nucleophiles 742 VI. Reactions of Acetal-Like Compounds with Nucleophiles 743 VII. Reactions of Carbonyl Compounds with Nucleophiles 747 A. Reactions with π-Nucleophiles 747 B. Reactions with σ-Nucleophiles 751 C. Activation of Carbonyl Compounds by Combinations of Lewis Acids 752 VIII. Three-Component Coupling of a Carbonyl Compound, an Alkoxysilane, and a Nucleophile 753 IX. Activation of the CdN Bond 755 A. Reactions of Unfunctionalized Imines 755 B. Addition to Imines Containing Electron-Withdrawing Groups 755 C. Addition to Nitrones 757 D. Addition to Nitronates 758 X. Cycloaddition Reactions 759 A. Reactions of Acetals of R,β-Unsaturated Carbonyl Compounds 759 B. Activation of R,β-Unsaturated Carbonyl Compounds 760 C. Cycloaddition of Heterodienes and Heterodienophiles 762 XI. Conjugate Addition 763 A. Reactions of Organocopper Compounds 763 B. Other Conjugate Addition Reactions 764 XII. Miscellaneous Reactions 766 XIII. Acknowledgment 768 XIV. References 768 § This paper is dedicated to Professor Herbert Mayr on the occasion of his 55th birthday.