Anilines Sandmeyer isatin synthesis

SANDMEYER Isatin Synthesis Isatin synthesis from anilines (see 1st edition). 

Although many of the anilines used in the Sandmeyer isatin synthesis have minimal functionality, examples exist where potentially sensitive motifs can survive the harsh reaction conditions. The 6-azauracil substituted aniline 39 could be converted to isatin 40 en route to the polyheterocyclic compound 41. A trifluoroacetyl protected amine could also be carried through the two-step Sandmeyer sequence to yield the isatin of interest. ... 

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... 

Sandmeyer s valuable isatin synthesis involves the removal of sulphur from diphenylthiourea (I) (p. 169) with basic lead carbonate. Hydrogen cyanide is combined with the reactive diphenylcarbodiimide (II) so obtained, and the nitrile (III) produced is converted by means of hydrogen sulphide into tbe thioamide (IV). Concentrated sulphuric acid brings about ring closure and the product is the a-anil of isatin (V). Then, by hydrolysis with dilute sulphuric acid, aniline is removed ... 

Sandmeyer isonitrosoacetanilide isatin synthesis. Formation of isonitrosoacetodi-phenylamidine by condensation of chloral hydrate, hydroxylamine, and aniline cyclization with concentrated sulfuric acid and quantitative hydrolysis to isatin on dilution. 

The most frequently used synthesis of isatins is the Sandmeyer procedure, which involves the formation of an isonitrosoacetanilide (3) from an aniline (2), chloral hydrate, and hydroxylamine. The isonitroso-... 

The method developed by Sandmeyer is the oldest and the most frequently used for the synthesis of isatin. It consists in the reaction of aniline with chloral hydrate and hydroxylamine hydrochloride in aqueous sodium sulfate to form an isonitrosoacetanilide, which after isolation, when treated with concentrated sulfuric acid, furnishes isatin in >75% overall yield17. The method applies well to anilines with electron-withdrawing substituents, such as 2-fluoroaniline18, and to some heterocyclic amines, such as 2-aminophenoxathine19 (Scheme 1). 

Synthesis of isatin. This synthesis originated with Sandmeyer and was further improved by Marvel and Hiers. " The first step, in which aniline is condensed with chloral hydrate and hydroxylamine hydrochloride to form isonitrosoacetanilide (I) is represented schematically as follows ... 

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