A quantum chemical approach towards understanding stability and tautomerism of 2-imino-2H-pyran derivatives

Abstract

The ring-chain tautomerism of 2-imino-2H-pyran derivatives annelated with an aromatic or aliphatic ring and their transformation into corresponding 2-pyridons were studied based on the relative stabilities of two series of model isomers calculated by the DFT method.

TWO-STAGE ONE-POT INTERACTION OF ACYCLIC Β-Ketoesters, DMFDMA AND 2-Cyanomethylbenzimidazole

“…The use of piperidine as catalyst in i-PrOH under microwave irradiation at 100 ºC during 5 min [8] resulted in formation of pure expected product 8a, but the isolated yield was again very low (12%, Entry 9). Further experiments with catalytic amounts of piperidine, its stoichiometric quantities and excess at higher temperatures (Entries [10][11][12][13][14] showed that under such conditions increasing amounts of the undesired by-product 10a appeared in the isolated material. The reaction carried out at 160 °С during 20 min under microwave irradiation gave the pure by-product (10a, Entry 15).…”

“…Selected representatives were analyzed by means of IR spectroscopy, mass-spectrometry, LC-MS and elemental analysis, 13 C NMR, APT NMR as well as HSQC and HMBC correlation NMR spectroscopy. NMR spectra were recorded on a Bruker Avance drx 500MHz (126MHz for 13 C NMR; Bruker Spectrospin Ltd., Coventry, United Kingdom), Varian MR 400MHz spectrometer (100MHz for 13 C NMR), and Varian Mercury VX 200MHz (Varian Inc., Palo Alto, CA) using DMSO-d 6 as a solvent and residual solvent signal as the reference (TMS scale). IR spectra were recorded on a Perkin Elmer Spectrum One FTIR spectrometer (PerkinElmer, Inc., Shelton, CT) (in KBr pellets).…”

“…Working in this field we studied previously several variations of a one-pot reaction between α-CH 2 -carbonyl compounds, dimethylformamide dimethylacetal (DMFDMA) and active methylene nitriles giving a great diversity of heterocyclic compounds of different classes [8][9][10][11][12][13]. Selectivity and pathways of such transformations depend on both the reaction conditions and the structure of initial compounds.…”

In Silico and In Vitro Studies of 4-Hydroxycoumarin-Based Heterocyclic Enamines as Potential Anti-Tumor Agents

“…Some commercially available coumarin-based drugs are shown in Figure 1 [17][18][19][20]. Among coumarin derivatives, enamines derived from coumarins are proven to be important compounds that can act as anti-tumor, antibacterial, antiproliferative, and antifungal agents [21,22]. Different strategies can be used to derivatize these heterocyclic compounds, but multistep synthesis routes often affect the yields of the final products.…”