Larock indole synthesis

N-methyl, N-acetyl, and N-tosyl derivatives of ortho-iodoanilines have been shown to be the most successful anilines that can be used to produce good to excellent yields.

[1] Bases other than sodium or potassium carbonate have been used to produce a good overall yield of the annulation reaction.

In particular, alkynes with substituents including alkyls, aryls, alkenyls, hydroxyls, and silyls have been successfully used.

However, researchers from Boehringer-Ingelheim were able to successfully use both o-bromoanilines and o-chloroanilines to form indoles by using N-methyl-2-pyrrolidone (NMP) as the solvent with 1,1'bis(di-tert-butylphosphino)ferrocene as the palladium ligand.

Nishikawa et al. derived iso-tryptophan by using Larock indole synthesis with pre-synthesized α-C-glucosylpropargyl glycine and o-iodo-tosylanilide.

[6] This reaction produced the product which had the reverse regioselectivity of normal Larock indole synthesis.

Optically active tryptophan which adheres to the regioselectivity of the Larock indole synthesis can also be synthesized using o-iodoaniline with propargyl substituted bislactim ethyl ether.

Regioselectivity of the alkyne insertion in Larock indole synthesis ^{[

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Heterannulation of an indole using o -chloroaniline ^{[

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Larock indole synthesis of iso-tryptophan using α- C -glycosylamino acid ^{[

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