This critical review discusses recent developments in the field of cyclopropene chemistry. Although several excellent reviews that mainly focused on the thermolysis and pyrolysis as well as metal-mediated reactions of cyclopropenes have been published, significant new developments have also been achieved in recent years. This brand new review provides an overview of the progress from 2007 to 2011 on the syntheses and transformations of cyclopropenes as well as their related mechanistic studies (238 references).

Asymmetric annulation of allenes with electron-deficient olefins and imines is one of the most important reactions for the synthesis of optically active carbo- and heterocycles, which are useful building blocks for the synthesis of natural products and medicinally important substances. The use of chiral phosphines as enantioselective catalysts can be envisaged for such cyclizations. This article focuses on the important developments concerning asymmetric annulations of allenes with unsaturated partners in the recent decades and on the perspectives that these new developments offer.