Lewis base catalyzed reactions with latent nucleophiles and phosphonium intermediates The aim of this thesis was to develop solutions to overcome the common problem related to nucleophile scope in Lewis base catalyzed reactions and develop new synthetic methods and generate new knowledge and deeper understanding of these processes. Relying on the strategies used in previous Lewis base catalyzed allylic substitutions using N H acidic nucleophiles we have expanded the scope to allylation of anilines that have been considered insufficiently N H acidic for applications in such reactions. The concept of latent nucleophiles was the development of enantioselective N allylation of N silyl pyrroles indoles and carbazoles using allylic luorides. They proceed with excellent regioselectivity and expand the scope of Lewis base catalyzed allylic substitutions to otherwise problematic nucleophiles. Further application of the concept of latent nucleophiles in Lewis base catalysis was pursued with C centered nucleophiles for introduction of difluoromethyl phosphonate moiety. In contrast the work presented in this thesis on reactions catalyzed by P centered Lewis bases was focused on the possibility of simultaneous dual activation of small organic molecules with Lewis acids and Lewis bases that do not form stable Lewis adducts and constitute non traditional frustrated Lewis pairs. The work on the development of 1 2 reduction of ynones and trans hydroboration of ynoates highlighted the versatile reactivity of vinyl hosphonium salts and inspired further studies involving these types of intermediates. Interest in reactivity of vinyl phosphonium ions informed the interest in reactivity of aryl phosphonium ions. In this area we have shown that thiazoles and benzothiazoles undergo regioselective C2 H functionalization to form thiazol 2 yltriphenylphosphonium salts which undergo efficient substitution reactions with N O S and Se centered nucleophiles to introduce various heteroatom substituents in the C2 position of thiazoles and benzothiazole.