Halogen-mediated synthesis

Halogen-mediated synthesis of cyclic peroxides through free radical... 

Halogen-mediated syntheses of oxazoles were also described for instance, the iterative bromination/debromination of 126 with NBS allowed a wide-scope, metal- and catalyst-free synthesis of oxazoles 127 (13EJ04554). 

Cyclization of N-allylic a-chloro-a-thioacetamides, catalyzed by Ru complexes, gives rise to five-membered lactams (equation 167). This reaction has been used as a key step in the synthesis of several natural products597. Other similar Ru-catalyzed cyclizations have been used to prepare 2-pyrrolidinones598,599. This methodology is preferable over the equivalent BusSnH-mediated radical cyclization600,601 when a halogen atom is required in the target molecule. 

The intent of this review is not to cover all aspects of the use of halides in synthesis but rather to cover recent developments that are hopefully of interest to the synthetic community at large. Other chapters in the present volume cover some of the reactions of organic halides that are mediated by transition metal compounds (by J. Green) and the use of hypervalent halogen compounds (by G. Koser). The reader is referred to these chapters for further detail. 

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