Rearrangement benzohydroxamic acids

The neutral alkali metal salts of benzohydroxamic acids have been found to undergo an unprecedented rearrangement to A(,A( -diarylureas. 2 side reaction, producing /9-alanine derivatives by way of a Lossen rearrangement, has been observed to accompany the hydrolysis of alkyl succinimidyl carbonates in basic aqueous buffers (see Scheme 97). The development of a modified Lossen rearrangement, whereby... 

Rearrangements. Hurd and Bauer" added tosyl chloride in chloroform to a suspension of the sodium salt of benzohydroxamic acid (1) in the same solvent, noted a vigorous reaction, and characterized the product as benzo-(phenylcarbonyl-hydroxamic) acid (6). They postulate that the initial product is the tosylate (3), that this is a much stronger acid than (1) and so abstracts sodium from the salt (2) to give the salt (4), which undergoes concerted cleavage and Lessen rearrangement to phenylisocyanate (5) and sodium tosylate. The phenylisocyanate is then captured by (1) to yield the final product (6). 

The role played by benzeneseleninic acid or by phenylseleninyl chloride in promoting the rearrangement of A-aryl-benzohydroxamic acids PhOONArOH to p-hydroxy-benzanilides relies on the formation of seleninate or selenenate esters, respectively, followed by Claisen-type shifts to ortho- and then para-positions. ... 

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