Nitrogen Beckmann rearrangement-addition

Imidates, or even nitrogen compounds produced from imidates by the addition of nucleophiles, may be obtained from oximes by a Beckmann rearrangement-addition process. 

The oxime nitrogen can also participate in cycloamination reactions to give pyrroles. Thus, treatment of oxime esters such as 185 with Pd(Ph3P)4 readily affords 186 [129]. The pentafluorophenyl group is necessary for good results otherwise a Beckmann rearrangement can unfavorably enter the picture. The oxime stereochemistry makes no difference on the outcome of the reaction. In addition to 186, pyrroles 187 and 188 were also prepared in this study (among others) [129]. 

In addition, heating of 89a in pyridine/water gives rise to a Beckmann rearrangement,254 whereas heating in dry pyridine causes rearrangement to 90, possibly through an ion pair mechanism and reentry of the saccharin anion via the nitrogen.43, 254... 

Phosgene reacts with oximes to form 0-(ch oroformyl) oximes 124, which, on addition of antimony pentachloride, undergo smooth Beckmann rearrangement with loss of carbon dioxide to give the nitrilium salts 125 almost quantitatively [66]. With oxygen or nitrogen nucleophiles, O-(chloroformyl) oximes 124 form symmetrical and unsymmetrical oxalyl derivatives. 

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