Hydrazides reductive cleavage

Reductive cleavage 0/olefins. In refluxing ether under nitrogen, sodium hydrazide reductively cleaves olefins of the type (1). Yields of the nitrogen-free products (3) are as a rule over 80%. An isolated double bond is not attacked. 

Benzenesulfonamide, Ar,AT-dibromo-4-methyl-(TsNBr2) bromohydrination with, 287 Benzenesulfonamides reductive cleavage, 247 synthesis of drugs, 301, 307-308 Benzenesulfonic acids. See Sulfonic acids Benzenesulfonic acid, 4-methyl-, esters (tosylates) alkyl a-synthons, 16, 24, 47, 93 fragmentation of, 89 rearrangement of, 32 reductive cleavage of, 114, 202-203 —, 4-methyl-, hydrazide (tosylhydrazine) hydrazones of fragmentation, 89 reduction, 109... 

Some pyridazines were investigated by cyclic voltametry and/or preparative scale electrolysis to give mixtures of reduced compounds [77NKK990 81 ACS(B)185]. The half-wave potentials of some 3(27/)-py-ridazinones were determined at different pH and correlated with Hammett o--constants (77KGS668). Maleic hydrazide is stable, but reduced pyrida-zines undergo reductive N—N bond cleavage upon electroreduction (78-LA 1505). 

The reduction of acyl hydrazines has been investigated very little. Polarography of 4-pyridine carboxylic acid hydrazide in acid and neutral solution shows that it is reduced in two, two-electrons steps [141]. The result of controlled potential electrolysis is cleavage of the N-N bond to form 4-pyridine-carboxamide, which then undergoes reduction to the aldehyde in the second step. Other hydrazides of heterocyclic carboxylic acids behave analogously. 

Along with velbanamine (173) the reductive acid cleavage of vinblastine and vincristine gives some cleavamine (176). This latter is presumably formed by acid-catalysed elimination of water from (173). It therefore follows that in velbanamine (173) and cleavamine (176) centre 2 has the same chirality. The absolute configuration of centre 4 was determined from the previously mentioned X-ray analysis of vincristine methiodide, as well as by the reductive acid cleavage of the hydrazide (177) to velbanamine (see later). 

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