Impurity: Pharma Market and Importance

β‐Enaminone Synthesis from 1,3‐Dicarbonyl Compounds and Aliphatic and Aromatic Amines Catalyzed by Iron Complexes of Fused Bicyclic Imidazo[1,5‐a]pyridine Derived N‐Heterocyclic Carbenes

“…2 mL) and the resultant solution was irradiated under mercury vapor light at 70°C for 12 hours [Except for entries 1-4, Table 4, entries 1-3, Table 5, for which the catalysis reaction was performed at 27°C for 6 hours under UV light irradiation (λ = 294 nm)]. The volatiles were then removed in vacuo and the crude product was purified by column chromatography using silica gel as stationary phase and eluting with a mixed medium of petroleum ether/EtOAc (v/v 60:40-97:3) to give the -enaminone products (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36).…”

“…Selected bond lengths (Å) and angles (°): Fe(1)-C(1) 1.977 (7), Fe(1)-C(8) 1.789(8), Fe(1)-C(9) 1.774(8), C(1)-N(1) 1.349(10), C(1)-N(2) 1.363(10), B(1)-F(1) 1.340(10), Fe(1)-C(1)-N(1) 130.6(6), Fe(1)-C(1)-N(2) 126.2(6), C(8)-Fe(1)-C(9) 88.7(4), O(1)-C(8)-Fe(1) 175.9(6), O(2)-C(9)-Fe(1) 178.2 (7). Significantly enough, the Fe-NHC complexes (1-2)c successfully performed the desired condensation reaction between a variety of acyclic and cyclic 1,3-dicarbonyl compounds (Scheme 2, Scheme 3 and Scheme 4) and aliphatic and aromatic amines yielding -enamino ketones (3-10) ( Table 2) and (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27) (Table 4) and -enamino esters (11)(12)(13)(14)(15)(16) (Table 3) and (28-36) ( Table 5) in the presence of light irradiation. More importantly, substantial enhancement of the -enaminone product yields of ca.…”

“…One conventional approach for the synthesis of the -enaminone involves the condensation of 1,3-dicarbonyl compounds with amines. The reaction has been extensively studied with simple transition metal salts, [14][15][16] an s-block metal salt, [17] the p-block metal salts, [18,19] and even the f-block metal salts. [20,21] Apart from these, the usage of simple acids, [22] organocatalysts [23] and the heterogeneous catalysts [24][25][26] have been reported for the synthesis of -enamino compounds.…”

“…68-95 %) under ambient condition in the presence of UV light irradiation (λ = 294 nm) at 27°C ( Table 2). The Fe-NHC (1-2)c complexes also effectively carried out the condensation reaction between pentane-2,4-dione and a wide variety of aromatic amines namely, the benzylic ones, phenylmethanamine, 1-phenylethan-1-amine, heterocyclic ones, pyridin-2-ylmethanamine, furan-2-ylmethanamine, aryl amines like, aniline, 2,6dimethylaniline, 2,4,6-trimethylaniline, 2,6-diisopropylaniline, 2-iodoaniline, 2-methoxyaniline and 2-phenoxyaniline yielding aromatic -enamino ketones (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27) in good to excellent yields (ca. 71-96 %) in the presence of light irradiation (Table 4).…”

“…71-96 %) in the presence of light irradiation (Table 4). Notably the -enamino ketones (17)(18)(19)(20) obtained from benzylic amines, the catalysis reaction was performed at 27°C in the presence of UV light irradiation (λ = 294 nm) (Entries 1-4, Table 4) while for the -enamino ketones (21-27) obtained from the aryl amines were performed at 70°C in the presence of mercury light irradiation (Entries 5-11, Table 4).…”