Halolactonization is a very useful organic reaction which has been applied in many syntheses in the past decades. In contrast, its asymmetric variant remains uncommon. Very recently, several organocatalytic halolactonization methodologies were developed which allows us to access a range of chiral halolactones.Halolactonization is an important class of organic transformation. The resulting halolactones are of particular interest to synthetic chemists because of the importance of the lactone moieties that pervades a wide spectrum of molecular structures (e.g., the fundamental unit of many natural products). In addition, the halogen substituents can be readily modified to other useful functional groups (e.g., by nucleophilic substitution). The importance of halolactonization is underscored by the large number of applications to the synthesis of useful building blocks and biologically active molecules. 1 Over the past decades, a number of methods have been used to construct enantiopure lactones. Despite the successful entries in some reports, 2,3 many other cases returned with low enantioselectivities. In addition, the use of a prochiral olefinic acid and an achiral halogen source with a substoichiometric amount of chiral catalyst in the asymmetric halolactonization remains a challenge.The development of asymmetric catalytic halolactonization is far behind the progress of the corresponding nonasymmetric version; this can be attributed to two main reasons: (1) it is difficult to identify a suitable catalytic system which allows the effective transfer of the chiral information; (2) the enantiomerically enriched haloniumolefin intermediate may racemize through a rapid olefinolefin halogen exchange. 4 Herein we discuss several important organocatalytic strategies to surmount the abovementioned problems.A widely accepted mechanism of halolactonization is shown in Scheme 1, which involves the formation of a halonium cationic species A followed by the intramolecular nucleophilic substitution (Scheme 1). 1 Based on this mechanism, two strategies can be used to effect the asymmetric halolactonization: the stereospecific nucleophilic attack of the carboxylate group to one face of the olefin and the enantioselective delivery of the halonium ion.To control the nucleophilic attack of the carboxylate group enantioselectively, a chiral amine or a chiral quaternary ammonium carboxylate ion pair has been employed.Another strategy relies on the enantioselective delivery of the halonium source using N-haloamide. As illustrated in Scheme 2, this can be achieved via a Lewis acid/Brønsted acid (path A) or a Lewis base (path B) activation mode. 5 An example of the Lewis acid activation mode is the use of a salen-Co catalyst in the iodolactonization of a bulky olefinic substrate to offer up to 83% ee. 6 However, as we