Regio- and Chemoselective Synthesis of Halohydrins by Cleavage of Oxiranes with Metal Halides

Recent developments in the regio-, chemo- and stereoselective oxirane cleavage by new halogenating reagents allow obtention of various vicinal halohydrins. Also, epoxy alcohols and other functionalized oxiranes can be conveniently converted into the corresponding halohydrins. Some of the new methodologies have been successfully applied to the preparation of optically active fragments toward the synthesis to more complex molecules and natural products. 1. Introduction 2. Cleavage of Monosubstituted Oxiranes with Metal Halides 2.1 Lithium Halides 2.1.1 Proton Catalysis 2.1.2 Metal Catalysis (Ni, Cu, Ti) 2.2 Sn, Co, Na, Mg, Al Halides 2.3 Boron Halides 3. Synthesis of Fluorohydrins 4. Cleavage of Oxiranes Bearing Proximate Functional Groups 4.1 Epoxy Alcohols 4.1.1 Titanium (IV)-Mediated Cleavage 4.1.2 Al, Li, Mg, B-Mediated Cleavage 4.2 C-1 Reactivity of 2,3-Epoxy Alcohols with LiI 4.3 Cleavage of oxiranes Bearing Carbonyl or Carboxyl Groups 5. Synthetic Applications 5.1 "In Situ" Reductive Opening of Oxiranes to Alcohols and Vicinal Diols 5.2 Synthesis of Halogenated Marine Natural Products 6. Conclusion