Bartoli indole synthesis

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The Bartoli indole synthesis (also Bartoli reaction ) is a name reaction from the field of organic chemistry.

Overview reaction for the Bartoli indole synthesis

Bartoli-indole synthesis can be used to prepare 7-substituted indoles from ortho -substituted nitrobenzenes . Three equivalents of a vinylic Grignard compound are required for the reaction .

Reaction mechanism

Bartoli made considerations about the mechanism based on experimental data. The mechanism is shown here by the reaction of 2-nitrotoluene and vinyl magnesium bromide:

Mechanism of the Bartoli indole synthesis

In the first reaction step , the Grignard compound attacks the oxygen in o -nitrotoluene 1 . The resulting intermediate 2 is now eliminated to nitrosotoluene 3 , the enolate being lost . The second equivalent of the Grignard compound now attacks the oxygen again. The compound 4 thus obtained first rearranges to give 5 and then cyclizes to give intermediate 6 . The last equivalent of the Grignard compound acts as a base and deprotonates 6 , resulting in 7 rearomatization . Acid work-up ultimately results in the product 7-methylindole ( 8 ).

Individual evidence

  1. ↑ Bartoli, G .; Leardini, R .; Medici, A .; Rosini, G .: Reactions of nitroarenes with Grignard reagents. General method of synthesis of alkyl-nitroso-substituted bicyclic aromatic systems . In: J. Chem. Soc. , Perkin Trans. 1. 1978 , pp. 692-696, doi: 10.1039 / P19780000692 .
  2. ↑ Bartoli, G .; Palmieri, G .; Bosco, M .; Dalpozzo, R .: The reaction of vinyl Grignard reagents with 2-substituted nitroarenes: A new approach to the synthesis of 7-substituted indoles . In: Tetrahedron Letters . 30, No. 16, pp. 2129-2132. doi : 10.1016 / S0040-4039 (01) 93730-X .
  3. ↑ Bosco, M .; Dalpozzo, R .; Bartoli, G .; Palmieri, G .; Petrini, M .: Mechanistic studies on the reaction of nitro- and nitrosoarenes with vinyl Grignard reagents . In: Journal of the Chemical Society, Perkin Transactions 2 . 1991, No. 5, pp. 657-663. doi : 10.1039 / P29910000657 .
  4. ^ Jie Jack Li (Ed.): Name reactions in heterocyclic chemistry . Wiley-Interscience, Hoboken, NJ 2005, ISBN 0-471-30215-5 , pp. 100-103 .

Web links

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