Nucleophilic Substitution of Hydrogen Atom in Initially Inactivated Pyrrole Ring

Abstract

It has been found that 1-dialkylamino-8-(pyrrolyl-1)­naphthalenes 1 and 6, upon treatment with an equimolar amount of HBF4 under ambient conditions, produce 1-dialkylammonium salts which are transformed into 7,7-dialkyl-7H-pyrrolo­[1,2-a]­perimidine-7-ium tetrafluoroborates 5 and 7, respectively. The reaction proceeds in a highly selective manner and represents the first case of nucleophilic substitution of hydrogen in the initially inactivated pyrrole ring. The scope and limitations of the transformation, apparently operating due to the joint action of the “proximity effect” and proton catalysis, are outlined.

Modeling Biologically Important NH···π Interactions Using peri-Disubstituted Naphthalenes

“… a This work. b Reference . c Reference . d Spectral database of organic compounds (SDBS no 1171); Internet resource: (). e Referene . …”

“…Correlation of the Δδ­(NH) values versus the XRD NH···M distances for the tetrafluoroborates 1 – 5 and 37 . Because for pyrrole derivative 37 diffraction measurements could not be performed (ref ), the DFT gas-phase distance was used in this case.…”

“…The choice of these proton donors is explained by a wide range of their NH-acidity (p K a ≈ 5–27), as well as their abundance in living tissues. It should be noted that the results of the study of salt 1 and its analogue with the unsubstituted pyrrolyl group instead of the phenyl one were reported by us in a slightly different context in recent articles. , …”

“…Potassium hydroxide (112 mg, 2 mmol) was stirred in dimethyl sulfoxide (3 mL) until dissolution, then N -(8-phenylnaphthalen-1-yl)­acetamide ( 8 ) (464 mg, 1,8 mmol) and methyl iodide (0.4 mL, 6.4 mmol) were added and the reaction mixture was stirred at room temperature for 24 h. The resulting product was separated on addition of water (50 mL), filtered off, and purified by column chromatography (Al 2 O 3 /CH 2 Cl 2 ) to give colorless crystals of 19 (170 mg, 35%), mp 170–170.2 °C. 1 H NMR (250 MHz, CDCl 3 ): δ 1.50 (s, 0.5H, CH 3 ), 1.70 (s, 3H, CH 3 ), 2.63 (s, 3H, CH 3 ), 2.78 (s, 0.5H, CH 3 ), 7.18–7.20 (m, 1.7H), 7.26–7.29 (m, 1.2H), 7.33–7.38 (m, 5H), 7.45–7.55 (m, 2.6H), 7.85–7.94 (m, 2.3H).…”

Interaction, bond formation or reaction between a dimethylamino group and an adjacent alkene or aldehyde group in aromatic systems controlled by remote molecular constraints

“…in 9 and 10. The constraint applied by the peri-naphthalene system has been used for studying other interaction such as unusual hydrogen bonding situations 11 and through space magnetic coupling between specific elements. 12 The 2,2'-disubstituted biphenyl system has also been employed, with the 1,5 interactions in naphthalenes replaced by 1,6 interactions with greater freedom of movement between the groups due to the possibility of rotation about the inter-ring bond.…”