Silica gel-assisted reductive cyclization of 2-nitro-β-piperidinostyrenes, derived from 2-nitrotoluenes, to indoles was written by Kawase, Masami;Sinhababu, Achintya K.;Borchardt, Ronald T.. And the article was included in Journal of Heterocyclic Chemistry in 1987.Electric Literature of C8H9NO3 This article mentions the following:
Condensation reaction of nitrotoluenes I (R = H, F, OMe, OCH2Ph; R1 = H, MeO, PhCH2O; R2 = H, Cl, PhCH2O) with tripiperidinomethane, followed by reductive intramol. cyclocondensation of the product nitropiperidinostyrenes II with Fe-silica gel gave 62-94% indoles III. In the experiment, the researchers used many compounds, for example, 3-Methyl-4-nitroanisole (cas: 5367-32-8Electric Literature of C8H9NO3).
3-Methyl-4-nitroanisole (cas: 5367-32-8) belongs to ethers. Ether is less polar than esters, alcohols or amines because of the oxygen atom that is unable to participate in hydrogen bonding due to the presence of bulky alkyl groups on both sides of the oxygen atom. But ether is more polar than alkenes. Ethers can form hydrogen bonds with other molecules (alcohols, amines, etc.) that have O―H or N―H bonds. The ability to form hydrogen bonds with other compounds makes ethers particularly good solvents for a wide variety of organic compounds and a surprisingly large number of inorganic compounds.Electric Literature of C8H9NO3
Referemce:
Ether – Wikipedia,
Ether | (C2H5)2O – PubChem