Bromonium dicollidine perchlorate

The raws-3,4-disubstituted cyclohexene 84 affords the corresponding 2-oxazolidinone 9 by treatment with bromonium dicollidine perchlorate. 

The stereo- and regioselective cyclizations of the allylic urethanes (199) to oxazolidin-2-ones and/or perhydropyrroIo[l,2-c][l,3]oxazin-l-ones by iodonium and bromonium dicollidine perchlorates in dichloromethane via intermediate 203 have been studied. In this same manner, 204 was generated from 200. In the cyclization of 201 in the presence of bromonium dicollidine perchlorate, the only product recovered was 205, while a similar reaction with isomer 202 resulted in a mixture of 206 and 207(1 5 ratio, respectively) (83JA654). 

TV-Bromosuccinirnide (NBS) and NIS are the most widely used electrophiles to activate -pentenyl glycosides. Catalytic amounts of acids such as TfOH or trieth-ylsilyl triflate (TESOTf) are introduced to speed up the generation of bromonium or iodonium ions [43], The stereochemical outcome depends, as usual, on whether a participating group exists at C2. An alternative promoter is iodonium dicollidine perchlorate (IDCP), whose lower reactivity allows it to selectively activate certain disarmed n-pentenyl glycosides [44],... 

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