Keto-cis-trans-enol-equilibrium of 3-alkylacetylacetones

Modulation of Tautomeric Equilibria by Ionic Clusters. Acetylacetone in Solutions of Lithium Perchlorate−Diethyl Ether

“…Kinetic runs were initiated by injecting 10.0 μL of a 1.2 × 10 -2 M acetylacetone−ether solution into 3.0 mL of LPDE solution and monitoring the decrease in absorbance over time at 275 nm. Since 3,3-dimethyl-2,4-pentanedione exists exclusively as the diketone, with a λ max = 310 nm and an ε 310nm = 170 M -1 cm -1 in ether and ethanol, the absorbance observed for acetylacetone at 275 nm is due solely to its enol form . The decrease in absorbance over time is the result of a decrease in enol concentration as the equilibrium shifts to accommodate a medium of greater polarity, Scheme .…”

1-Bromo-2-trifluoroacetylcyclobutenes as novel building blocks for the construction of trifluoromethyl substituted heterocycles. Part 3: Synthesis of trifluoromethylsubstituted pyridines, condensed with cyclobutene moieties

“…While analyzing alternative approaches for pyridine construction, we have paid attention on diethyl ethoxymethylencyanophosphonate 3d, which potentially should be a useful reagent in different cyclizations. To our surprise there are only two papers of the same authors describing the synthesis of 3d in very low yield and subsequent reaction with alkali [18,19]. Our attempts to improve the described procedure and to prepare the phosphonate 3d by interaction of triethyl ortoformate with diethyl cyanomethylphosphonate in acetic anhydride gave approximately the same low yields as in original work.…”