Halo-oxepines

On the contrary, Harvey and coworkers also demonstrated that the reactivity of such gm-dihalocyclopropanated glycals could be switched to an A—B bond cleavage when the reaction was conducted under Lewis acid conditions [30b]. Thus, the ring opening of 58 using AgOAc or AgNOg furnished the halo-oxepine product. The intermediate... 

SCHEME 13.18 (a) Acid-catalyzed ring-opening of glycal derived gem-dibromo-cyclopropane derivative 58 and (b) rearrangement of halo-oxepines to C-furanosides 61 and 62 [30],... 

The ring expansion of oxyglycal-derived gm-dihalo 1,2-cyclopropanate oxyglycals provides stable seven-membered halo-oxepines, that are thus suitable precursors for further functionalizations. In a study, vinyl bromide of the bromo-oxepine was used for the metal-catalyzed cross-coupling reactions, namely, Heck, Suzuki, and Sonogashira reactions, so as to generate 2-deoxy-2-C-alkyl/ary/alkynyl septanosides [33]. 

Apart from metal-catalyzed cross-coupling reactions, hydrogenolysis of halo-oxepine was used as a key step for the synthesis of 2-chloro-2-deoxy septanoside... 

The chiral enamide 59 was reported to undergo halo-etherification to yield the brominated oxepine 60 with 20 1 diastereomeric ratio <07OL4459>. The same methodology was also extended to 1,4-dioxazepines. 

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