Batcho-Leimgruber synthesis

The Leimgruber-Batcho synthesis is a two-step method which provides indoles that arc substituted only in the benzene ring. The method was initially disclosed in a patent[l] and a representative procedure is available in Organic Syntheses[2]. A review of the reaction is available[3]. The reaction involves... 

One route to o-nitrobenzyl ketones is by acylation of carbon nucleophiles by o-nitrophenylacetyl chloride. This reaction has been applied to such nucleophiles as diethyl malonatc[l], methyl acetoacetate[2], Meldrum s acid[3] and enamines[4]. The procedure given below for ethyl indole-2-acetate is a good example of this methodology. Acylation of u-nitrobenzyl anions, as illustrated by the reaction with diethyl oxalate in the classic Reissert procedure for preparing indolc-2-carboxylate esters[5], is another route to o-nitrobenzyl ketones. The o-nitrophenyl enamines generated in the first step of the Leimgruber-Batcho synthesis (see Section 2.1) are also potential substrates for C-acylation[6,7], Deformylation and reduction leads to 2-sub-stituted indoles. 

When indoles unsubstituted in the heterocyclic ring are required, the Leimgruber-Batcho synthesis can be used. In its original form the... 

Indoles from p-dialkylamino-o-nitrostyrenes. The Leimgruber Batcho synthesis 7... 

Another intramolecular cyclization of amine 58 is the last step in the pyrrolo[3,2-fiflpyrimidine analogue 59 synthesis. Intermediate 58 formed in situ from nitro precursor 57 by reduction with tin(II) chloride is a key step of this version of Leimgruber-Batcho synthesis leading to formation of 59 finally. This simple three-step route to 59 started from the coupling of electron-poor dichloronitropyrimidine 54 with p-fluoroenamine 55 to form alkene 56. Regioselective nucleophilic... 

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