Batcho indole synthesis

The Batcho indole synthesis involves the conversion of an o-nitrotolnene to a fi-dialkyl-amino-o-nitrostyrene v/ith dimethylformairude acetM, followed by redncdve cychzadon to indoles. This provides a nsefid strategy for synthesis of snbsdtuted indoles fEq. 10.49. ... 

Batcho indole synthesis is a useful tool for synthesis of naniral products. As oudined in Scheme 10.6, the Batcho indole synthesis is used for total synthesis of the slime mold alkaloid arcyriacyanin. Such indolocarbazole alkaloids represent a growing number of naniral products isolated from soil organism, slime molds, and marine sources. They are important as andnimor compounds and protein kinase C and topoisomerase inhibitors. 

Carrera and Sheppard improved upon a Leimgruber-Batcho indole synthesis [24] to prepare 6-bromoindole (20) in excellent overall yield from 4-bromo-2-nitrotoluene [29a], and Rapoport utilized this method to synthesize 4-, 5-, 6-, and 7-bromoindole [29b]. 

A procedure for obtaining indole-3-carboxylate ester from the f-pyrrolidino-o-nitrostyrene intermediates in the Leimgruber-Batcho indole synthesis was demonstrated. Although ethyl chloroformate is evidently not reactive enough, phosgene followed by methanolysis effects f) -carbomethoxylation. Reductive cyclization then gives the indole esters. <95SC95>... 

Leimgruber-Batcho indole synthesis (from o-nitrotoluene and dimethylformamide dimethyl acetal) 84H(22)195. 

The Leimgruber-Batcho indole synthesis was quickly adopted by several groups for the synthesis of 2,3-unsubsti-tuted indoles. A tabulation of indoles prepared in this... 

Scheme 2 Proposed Mechanism for the Leimgruber-Batcho Indole Synthesis...

As for many reductions of the nitro group, the reaction often stops at an intermediate stage (NO, NHOH). Somei was the first to observe this in the Leimgruber-Batcho indole synthesis [60-62]. Although 1-hydroxyindole itself is very unstable, Somei and his coworkers were able to isolate 1-hydroxyindoles bearing an electron-withdrawing... 

An obvious extension of the Leimgruber-Batcho indole synthesis is to modify the intermediate (nucleophilic)... 

The myriad chemistry shown in this chapter clearly demonstrates the tremendous importance and enormous utility of the Leimgruber-Batcho indole synthesis. 

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