Nitrones as intermediates

This procedure has been used by Grigg as well as by other authors to synthesize nitrones as intermediates in the preparation of more complex molecules. An example is reported in Scheme 29. The oxime 192 was treated with PhSeBr and... 

It is interesting to note that the rate of isomerization of 50 exceeds that of 2-methyl-3,3-diphenyloxaziridine by a factor of 8000 at 100°C. Inversion of the chiral nitrogen in some oxaziridines has been effected by photolysis in most of the examined cases the isomerization is accompanied by racemization and proceeds via nitrones as intermediates. ... 

Intramolecular cycloadditions via nitrones as intermediates are generally highly stereoselective processes that are used to generate a number of stereocenters in a complex molecule3-5-6-8- 8. The intrinsic rigidity of the transition structures enhances the stereocontrol exerted by steric and stereoelectronic factors (see Section A.2.3.5.). Tor more recent examples of intramolecular cycloadditions via nitrones, see references 337-354. 

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