Many other syntheses of indole compounds have been reported. An efficient synthesis of indole (1) and its derivative beginning with lithiation at the methyl group of o-tolylisocyanide (37) follows
Back to the subject.
Scheme 2
(https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000268709-file_g6zy.gif)
Condensation of an o-nitrotoluene with oxalic ester, reduction to the amine, and cyclization to the indole
A. Reissert, Ber. 30, 1030 (1897).
W. O. Kermack et al., J. Chem. Soc. 119, 1602 (1921); P. C. Julian et al., Heterocyclic Compounds 3, 18 (1962); J. G. Cannon et al., J. Med. Chem. 24, 238 (1981).
Scheme3
(https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000268709-file_rdls.gif)
The Reissert indole synthesis is a convenient method for the synthesis of indole and indoles substituted in the benzene ring. In this method, o-nitrophenylpyruvic acid (35) [prepared from o-nitrotoluene (33) and diethyl oxalate (34)] is reductively cyclized to indole-2-carboxylic acid (36), which readily decarboxylates:
If you can't read it here is the link
Synthesis of indoles (http://www.unb.br/iq/labpesq/qo/olv/olv/about.htm)
(http://www.unb.br/iq/labpesq/qo/olv/olv/about.htm)indole-2-carboxylate link (http://www.orgsyn.org/orgsyn/prep.asp?prep=cv5p0567)
(http://www.orgsyn.org/orgsyn/prep.asp?prep=cv5p0567)From Organic Syntheses, CV 3, 479
The authors recommend the method of Reissert,12 which involves condensation of o-nitrotoluene with ethyl oxalate, followed by reduction to indole-2-carboxylic acid and decarboxylation of the latter.
Link (http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0479)
(http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0479)Link (http://www.orgsyn.org/orgsyn/prep.asp?prep=cv8p0493)
(http://www.orgsyn.org/orgsyn/prep.asp?prep=cv8p0493)link (http://www.orgsyn.org/orgsyn/prep.asp?prep=cv1p0261)
(http://www.orgsyn.org/orgsyn/prep.asp?prep=cv1p0261)http://patft.uspto.gov/netahtml/search-bool.html (http://patft.uspto.gov/netahtml/search-bool.html)
and search for "reissert" or a combination of the names of the reactants. There should be a few patents using this reaction...