Indoles Sandmeyer isatin synthesis

To study the conformational changes of tryptophan synthase by N-NMR, indole enriched in A-15 was required. Phillips used a Sandmeyer isatin synthesis starting with A-15-labeled aniline (45) to prepare 46 in good yield... 

Although isatins having adjacent carbonyls of very different reactivity— amide vs. ketone—undergo a variety of chenucal reactions [86,87], the focus here is on synthetic transformations to indoles. Accordingly, isatins can be reduced directly to indoles (Scheme 11, equations 1-7) [16,89-93]. Given the availability of isatins from aromatic amines (e.g., Sandmeyer synthesis [86], Gassman synthesis [88]), the reduction of isatins to indoles can be an important alternative to other methods. 

Indole-2,3-dione (isatin), red crystals, mp 204°C, is formed inter alia (cf p. 146) by the oxidation of indigo. A generally applicable synthesis of isatins 126 is the Sandmeyer synthesis, in which isonitrosoacetanilides 125 (easily accessible from primary arylamines, chloral hydrate, and hydroxylamine hydrochloride) are cyclized in acidic medium [195] ... 

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