Isatin

Isatin, also known as tribulin, is an organic compound derived from indole with formula C8H5NO2. The compound was first obtained by Otto Linné Erdman and Auguste Laurent in 1840 as a product from the oxidation of indigo dye by nitric acid and chromic acids. Isatin, also known as tribulin, is an organic compound derived from indole with formula C8H5NO2. The compound was first obtained by Otto Linné Erdman and Auguste Laurent in 1840 as a product from the oxidation of indigo dye by nitric acid and chromic acids. Isatin is a well-known natural product which can be found in plants of Genus Isatis and Couroupita Guianensis, and also in humans, as a metabolic derivative of adrenaline. It looks like an red-orange powder, and it is usually employed as building block for the synthesis of a wide variety of biologically active compounds including antitumorals, antivirals, anti-HIVs, and antituberculars. The isatin core is also responsible for the color of “Maya blue” and “Maya yellow” dyes. The Sandmeyer methodology is the oldest and straightforward way for the synthesis of isatin. The method involves the condensation between chloral hydrate and a primary arylamine (e.g. aniline), in the presence of hydroxylamine hydrochloride, in aqueous sodium sulfate to form an α‐isonitrosoacetanilide. Isolation of this intermediate and subsequent electrophilic cyclization promoted by strong acids (e.g. sulfuric acid) furnishes isatin in >75% yield. The Stolle procedure is considered the best alternative to Sandmeyer methodology for the synthesis of both substituted and unsubstituted isatins. In this case primary or secondary arylamines are condensed with oxalyl chloride to form a chlorooxalylanilide intermediate which can then cyclize in the presence of a Lewis acid (e.g. aluminium trichloride, titanium tetrachloride, boron trifluoride, etc.).