The author of 《Neutral Pyrrole Nitrogen Atom as a π- and Mixed n,π-Donor in Hydrogen Bonding》 were Pozharskii, Alexander F.; Ozeryanskii, Valery A.; Filatova, Ekaterina A.; Dyablo, Olga V.; Pogosova, Olga G.; Borodkin, Gennady S.; Filarowski, Aleksander; Steglenko, Dmitriy V.. And the article was published in Journal of Organic Chemistry in 2019. Category: tetrahydrofurans The author mentioned the following in the article:
9-Dimethylaminobenzo[g]indoles I [R1, R2 given:H,H (3);4-MeC6H4,Me(4);4-O2NC6H4,Me(5);H, CF3(6)] and 1-dimethylamino-8-(pyrrolyl-1)naphthalene 7 were examined as possible models for establishing the ability of the pyrrole nitrogen atom to participate in [NHN]+ hydrogen bonding as a proton acceptor. Indoles 3-5 (to a lesser extent 6) form rather stable tetrafluoroborates, with the proton mostly located on the NMe2 group but simultaneously engaged in the formation of a charged intramol. [NHN]+ hydrogen bond (IHB) with the pyrrole N atom. The theor. estimated energies of IHB in salts 3H+BF4–6H+BF4- vary between 7.0-10.7 and 6.2-7.0 kcal mol-1 in vapor and MeCN, resp. The pyrrole N atom undergoes a perceptible pyramidalization but still remains involved in the 6π-electron aromatic system, suggesting that the hydrogen bonding in salts 3H+BF4–6H+BF4- represents a previously unknown mixed NH···N(n,π) interaction. Despite the favorable orientation of the N-H bond and the pyrrole ring in salt 7H+BF4-, no signs of NH···N(n) bonding in it were noticed, and the existing interaction was classified as pure NH···N(π). The results obtained may be useful in studies of secondary protein structures, especially those α-helix sections which contain tryptophan residues. The experimental part of the paper was very detailed, including the reaction process of 2,5-Dimethoxytetrahydrofuran(cas: 696-59-3Category: tetrahydrofurans)
2,5-Dimethoxytetrahydrofuran(cas: 696-59-3) is a member of ether. Friedel Crafts reaction, for example, adds an alkyl or acyl group to aromatic ethers when they react with an alkyl or acyl halide in the presence of a Lewis acid as a catalyst.Category: tetrahydrofurans
Referemce:
Tetrahydrofuran – Wikipedia,
Tetrahydrofuran | (CH2)3CH2O – PubChem