The Hydrogenolysis of Organic Halides

The hydrogenolysis (dehalogenation, reductive dehalogenation) of organic halides is an important, well-established reaction which is frequently used in organic synthesis. Recently, new reducing agents have become available and many of these reagents have been applied to the hydrogenolysis of the carbon-halogen bond with notable success. In this review the entire field is surveyed and typical examples are described. The subject matter is treated from the viewpoints of the nature of the halogen atom, its structural environment in the molecule, and the reducing conditions capable of effecting hydrogenolysis. Numerous examples are described - some with experimental details - to enable the reader to select the most advantageous conditions pertinent to a desired dehalogenation reaction. 1 . Introduction 2. Scope of the Review 3. General Observations 4. Hydrogenolysis of Structural Types 4.1. Unactivated Alkyl and Cycloalkyl Halides 4.2. Activated Alkyl and Cycloalkyl Halides 4.3. Allylic and Benzylic Halides 4.4. Vinyl and Aryl Halides 4.5. Cyclopropyl Halides 5. Addenda 6. Conclusions