Synthesis of nitrogen heterocycles using isocyanates was achieved by organotin reagents and catalysts. The reactions proceeded via intramolecular alkylation through terminally functionalized tin species. Thus terminally halogenated, enone-substituted and carbonyl substituted tin alkoxides have been provided as key intermediates. Such tin species could be generated by tin-mediated selective reactions, the ring cleavage of halo lactones and the addition to functionalized carbonyl compounds. These equimolar reactions induced to tin alkoxide-catalyzed reactions, that is, catalytic annulation of isocyanates with α-hydroxyl carbonyls, glycolide, lactide. In particular, optically pure nitrogen heterocycles were obtained directly from easily available plant-derived chiral sources, lactides. Further, tin halide-catalyzed reactions could be developed, that is, catalytic annulation of isocyanates with epoxides, 2-methyleneaziridines and cyclopropanes. This article includes author’s development of tin promoted synthesis of nitrogen heterocycles using isocyanates.