Ring Opening of Glycal-Derived 1,2-Cyclopropane

The ring-opening reaction of functionalized 1,2-cyclopropyl carbohydrates is also known, apart from that of unfiinctionalized derivatives. Yu and Pagenkopf demonstrated the formation of oxepine 51 through Ferrier rearrangement-based ring opening 

SCHEME 13.13 Ring-opening reaction of glycal derived 1,2-cyclopropane to prepare oxepine 44 and 46 [26]. 

SCHEME 13.14 Cyclization of an acyclic thio-derivative 48 to septanoside containing disaccharide 49 [27]. 

SCHEME 13.15 Ring-opening of an ester functionalized 1,2-cyclopropane derivative 50 to oxepine 51 [28], 

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 

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