1 Asymmetric Organocatalytic Cyclization and Cycloaddition Reactions Albert Moyano* and Ramon Rios a, * Departament de Química Orgànica, Universitat de Barcelona. Facultat de Química, C. Martí i Franquès 1-11, 08028-Barcelona, Catalonia, Spain. E-mail address: amoyano@ub.edu (A. Moyano), rios.ramon@icrea.cat (R. Rios) RECEIVED DATE TITLE RUNNING HEAD: Organocatalytic Cyclizations and Cycloadditions. a) ICREA Researcher at UB. Catalan Institute for Research and Advanced Studies (ICREA), Pg. Lluís Companys 23, 08018-Barcelona, Catalonia, Spain. ABSTRACT. This review covers asymmetric organocatalytic methods leading to the enantioselective synthesis of carbocyclic and heterocyclic compounds, focusing on synthetically useful protocols, and is organized according to the different types of synthetic procedures affording cyclic frameworks: organocatalytic desymmetrizing cyclizations of prochiral substrates, in which at least one of the newly created stereogenic centers arises as a result of the desymmetrization, are discussed on the first place. Organocatalytic asymmetric ring-closing reactions of acyclic and monocyclic achiral substrates, in which the stereogenic centers are the result of the newly created carbon-carbon or carbon-heteroatom bonds, are next dealt with. Asymmetric organocatalytic reactions corresponding (at least formally) to classical cycloaddition processes are then discussed. Finally, two-component and multi-component