Fischer indole synthesis Claisen

Benzilic acid rearrangement Benzoin reaction (condensation) Blanc chloromethylation reaction Bouveault-Blanc reduction Bucherer hydantoin synthesis Bucherer reaction Cannizzaro reaction Claisen aldoi condensation Claisen condensation Claisen-Schmidt reaction. Clemmensen reduction Darzens glycidic ester condensation Diazoamino-aminoazo rearrangement Dieckmann reaction Diels-Alder reaction Doebner reaction Erlenmeyer azlactone synthesis Fischer indole synthesis Fischer-Speior esterification Friedel-Crafts reaction... 

Fermentation, 22, 53 Ferric nitrate, 23, 20 Fieser s solution, 21, 110 Filter fabric, Pyrex glass, 22, 33, 65 Vinyon, 22, 33, 67 Filter paper, hardened, 22, 45 Fischer indole synthesis, 22, 98 Flash distillation, 21, 85 Flask, modified Claisen, 22, 11 Fluorescence of 9-aminoacridine hydrochloride, 22, 7 Formaldehyde, 20, 60 Formalin, 22, 66 Formic acid, 20, 66, 102 23, 43 Formic acid, chloro-, benzyl ester, 23, 13... 

The Fischer indole synthesis. The Fischer acid-catalyzed conversion of an 7V-arylhydrazone 42 into an indole is one of the most powerful and versatile methods for the preparation of indoles . The mechanism involves a [3,3] sigmatropic Claisen-type rearrangement of a protonated enehydrazine tautomer 43 to give intermediate 44, which spontaneously cyclizes by loss of ammonia, probably via indoline 45, to an indole 46 (Scheme 27). For unsymmetrical ketones, two isomeric indoles are possible and the general result is that the indole derived from the more stable (usually the more highly substituted) enehydrazine is formed. 

Filter paper, hardened, 22, 45 Shark skin, 25, 97 Fischer indole synthesis, 22, 98 Flash distillation, 21, 85 Flask, modified Claisen, 22,11 Fluorescence of 9-aminoacridine hydrochloride, 22, 7... 

The N-analogs1 8 of the Cope and Claisen rearrangement have been widely used for syntheses of amines and /V-heterocyclcs, for example, the l,l -diaza-Cope rearrangement is the key step in the Fischer indole synthesis. 

That s the Fischer indole synthesis. The Reissert synthesis in some respects is more straightforward. The first step is a distant relative of a Claisen condensation, but a (nitro-group stabilized) benzylic anion takes the place of an enolate anion to add to the carbonyl group of the ester as shown ... 

An important type of aromatic Claisen rearrangement occurs in the Fischer indole synthesis. " The Fischer indole synthesis involves the condensation of an arylhydrazine with an aldehyde or ketone to give an arylhydrazone, which, in the presence of a catalyst undergoes rearrangement and elimination of ammonia to give the indole ring. One of many different protic or Lewis acid catalysts can be used. For example, Woodward s synthesis of strychnine commenced with the condensation of the ketone 303 and phenylhydrazine in the presence of polyphosphoric acid to give the indole 304 (3.194). 

The first step is a typical Claisen ester condensation and the second is an acid-catalysed thermodynamically controlled transesterification (the lactone and ethyl ester exchange alcohol partners) to give the more stable six-membered lactone, followed by decarboxylation. Now the Fischer indole synthesis works well and work-up with dry HCl in methanol gave the alkyl... 

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