Nitroso ring closure, reductive

The cyclopropyl analogs were made from the aminoalcohol 977, prepared from 976 by reaction with 6-chloroisocytosine followed by nitrosation to give the 5-nitroso derivative, which upon reduction in the presence of formic acid gave 979 as a mixture with its formyl derivative 978. Ring closure of... 

Reaction between the nitroso group and the anion of a P-diketone is often sufficiently rapid to compete with further reduction of the nitroso compound to the hy-droxylamine. This process is illustrated by reduction of 8. The initial ring closure product undergoes further reduction at the catltode and 9 is isolated in good yield... 

The mechanism of the reductive ring closure by formation of a nitrogen-nitrogen bond is often closely related to the mechanism of the formation of azoxy compounds. This has mostly been formulated as an attack of the nucleophilic hydroxylamino group on the positive center in the nitroso group, followed by loss of water. Inasmuch as the system ArNO + 2 e + 2 H + ArNHOH generally is electrochemically reversible, it is not unlikely... 

The C-2 or C-3 amino derivatives of pyrroles can be obtained by reduction of nitro or nitroso pyrroles or by Curtius degradation of pyrrolecarboxylhydrazides. A few ring closures give 2-aminopyrroles directly (see Section 3.06.2.3, for example), but these are rather specialized (B-77MI30608). 

Phenylhydroxylamines may be reoxidized anodically to the nitroso compound this may be used in ring-closure reactions (Chapter 18) [149]. If the reduction of the nitro compound and the reoxidation of the phenylhydroxylamine is done in a cell with two closely spaced porous electrodes, a condensation to azoxybenzene may be avoided [149]. 

Indazoles may be obtained by reduction of o-nitrobenzylamines followed by reoxidation of the hydroxylamine to a nitroso group ring closure occurs by addition of the amino group to the nitroso group followed by elimination of water [114]. 

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