Preparative Aspects of Electrophilic Three Component Reactions with Alkenes Additions of the electrophilic species Hal+, NO+, NO2+, SO3H+, RS+, HO+, RCO+ and others in the presence of a third nucleophilic agent like H2O, ROH, ROR, RCOOH, RCN, RSCN and others to an alkene leads to many kinds of unsymmetrical vicinal bifunctionalized compounds of preparative value. In the combination of alkenes with electrophilic halogen and f. e. water the products are 2-halohydrines, with alcohols 2-haloalkylethers, with carboxylic acids or derivatives 2-haloalkylesters and with nitriles N-2-haloalkylamides. The intramolecular combination of double bond and nucleophilic center in this reaction gives a lot of saturated heterocycles with five or six membered rings, for example halolactones, tetrahydrofurans or-pyrans, the corresponding thia analogues, oxazolines, thiazolines, imidazolines and others. Transannular reactions often occurs with medium membered cyclodienes or -oligoenes and results in interesting heterocycles, like f. e. oxa-, thia- or azabicyclo [4.2.1.] or [3.3.1.] alkanes. Scope and limitations of such reactions with alkenes are given with 287 references.