Halogenation phenylhydrazones

Reductions with aluminum are carried out almost exclusively with aluminum amalgam. This is prepared by immersing strips of a thin aluminum foil in a 2% aqueous solution of mercuric chloride for 15-60 seconds, decanting the solution, rinsing the strips with absolute ethanol, then with ether, and cutting them with scissors into pieces of approximately 1 cm [141,142]. In aqueous and non-polar solvents aluminum amalgam reduces cumulative double bonds [143], ketones to pinacols [144], halogen compounds [145], nitro compounds [146, 147], azo compounds [148], azides [149], oximes [150] and quinones [151], and cleaves sulfones [141, 152, 153] and phenylhydrazones [154] (Procedure 30, p. 212). 

Treatment of benzaldehyde l-allyl-[4-(methylsulfonyl)phenyl]hydrazone 251 with 45% sulfuric acid gave 252 rather than the expected l-allyl-l-[4-(methylsulfonyl)phenyl]hydrazine (Equation 63). Halogen-substituted hydra-zones gave similar results. Unsubstituted benzaldehyde phenylhydrazone gave normal hydrolysis <1996JHC213>. 

In addition to the acid-catalysed hydrolysis of oximes, a kinetic study has also been made of the addition of bromine to a number of substituted benzal-dehyde phenylhydrazones . The measurements were made in 70% acetic acid v/v, in the presence of 0.1 M potassium bromide. The attacking species was shown to be predominantly molecular halogen, and not the tribromide ion, since a graph of 2(1 -t- X[Br ]) against [Br ] was linear, and of zero intercept, k-2 being defined by the equation... 

The halogenation of the arylhydrazones of arylaldehydes is an excellent method of synthesis of hydrazidoyl halides. However, halogenation of the ring attached to nitrogen can not be avoided. For example, reaction of benzaldehyde phenylhydrazone (XI) with bromine in glacial acetic acid... 

Arsenic, Halogen, Phosphorus, Sulfur, Selenium and Nitrogen Containing Compounds - The (acyclic) phenylhydrazone of D-mannose, methyl 3,4-6-tri-... 

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