Oxime tosylates, cyclic

Potassium tert-butoxide Ethylenenitriles from cyclic oxime tosylates... 

Azirines (three-membered cyclic imines) are related to aziridines by a single redox step, and these reagents can therefore function as precursors to aziridines by way of addition reactions. The addition of carbon nucleophiles has been known for some time [52], but has recently undergone a renaissance, attracting the interest of several research groups. The cyclization of 2-(0-tosyl)oximino carbonyl compounds - the Neber reaction [53] - is the oldest known azirine synthesis, and asymmetric variants have been reported. Zwanenburg et ah, for example, prepared nonracemic chiral azirines from oximes of 3-ketoesters, using cinchona alkaloids as catalysts (Scheme 4.37) [54]. 

Benzoxazoles have been prepared by intramolecular reaction of a phenolic —OH groiq) with a Beckmann intermediate (equation 30). A cyclic imidate was isolated in high yield from tosylation and in situ Beckmann reaction of the erythromycin-derived oxime (4[Pg.698]

Spontaneous Beckmann rearrangement has been observed upon 0-tosylation of oximes. Lactams can therefore be conveniently prepared from cyclic oximes, as shown in eq 23. The rearrangement has long been known to proceed with retention of configuration of the migrating group.This is complementary to the reaction of oximes with Sulfuric Acid (eq 24). ... 

A Beckmann fragmentation of oximes using tosyl chloride in a basic ethanol-water system has also been observed. Formation of the cyclic product shown in eq 25 was consistent with a base-induced opening of an intermediate lactone followed by rearrangement and incipient extrusion of benzoic acid. 

Tosyl arenecarboxaldoximes, ArCH=NOTs, undergo unimolecular pyrolysis at 500 °C via a cyclic six-membered transition state to yield toluenesulfonic acid and the corresponding nitrile the oximes are ca 10" -fold more reactive than hydrazone counterparts which undergo an analogous thermal elimination. ... 

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