Tosylhydrazones, anodic oxidation

Electrochemical properties of tosylhydrazones of acylsilanes were also investigated. A decrease in the oxidation potential of tosylhydrazones caused by silylation is much smaller than that for carbonyl compounds (see Tables 7 and Section n.E., Table 9). Anodic oxidation of tosylhydrazones of acylsilanes provides the corresponding nitriles with consumption of a catalytic amount of electricity (equation 29)34. 

The acylsilane toxylhydrazones exhibit slightly less positive oxidation potentials than the corresponding tosylhydrazones of aldehydes [137]. The preparative anodic oxidation of acylsilane tosylhydrazones in a divided cell gave the corresponding nitriles. This reaction seems to be promoted by the electrogenerated acid. 

A new synthesis of nojigiku alcohol (773) (Vol. 4, p. 554) starts from tricyclene (774) and we should perhaps recall the preparation of the latter from camphor (40) tosylhydrazone and sodium methoxide in decalin. [Tricyclene is also produced in other reactions leading to camphene (775), such as the reaction of 3-bromocamphor with methylaniline. ] TTie new synthesis consists in anodic oxidation with triethylamine in acetic acid, and yields 76% of 773, with 8% of the endo-isomer and 11% of diols. Oxidation of tricyclene (774) with lead tetraacetate also gives nojigiku alcohol (773), but as a minor (16%) product, the main product being camphor (40). Tricyclene having a plane of symmetry, these methods all lead to racemic 773. 

Oxidation of silyl tosylhydrazones (35) in an aprotic medium (dichloromethane) also results in the formation of nitriles, but in this case the conversion is apparently a true anodic process41 in which the key difference from the anodic behavior of oximes is the presence of the p-toluensulfonyl group, which facilitates cleavage of the N—N single bond (equation 20). 

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