We employ transient absorption from the deep-UV to the visible region and fluorescence upconversion to investigate the photoinduced excited-state intramolecular proton-transfer dynamics in a biologically relevant drug molecule, 2-acetylindan-1,3-dione. The molecule is a ß-diketone which in the electronic ground state exists as exocyclic enol with an intramolecular H-bond. Upon electronic excita...

The photochemical decarbonylation of several crystalline 1,3-acetonedicarboxylates has been analyzed in solution and in the solid state. It is shown that the efficiency of the solid-state reaction depends on the stability of the intermediate acyl-alkyl and alkyl-alkyl radical pairs. Reactions proceeding through tertiary enol radicals are more efficient than reactions proceeding through secondar...

Flash photolysis of 10-diazo-9(10H)-phenanthrenone in aqueous solution was found to give two successively formed transient species and to produce fluorene-9-carboxylic acid as the major reaction product. These transients were identified, through solvent isotope effects and the form of acid-base catalysis, as fluorenylideneketene, formed by photo-Wolff reaction of the diazophenanthrenone, and fl...

The enol tautomers of the aromatic oc-keto acids combine instantaneously and reversibly with borate to form complexes of a mixed ester-anhydride structure, thereby displacing the apparent keto-enol equilibrium in favor of the enol tautomer. The enol tautomer and its borate complex have strong absorption in the 300 ml* region (1). This strong absorption is the basis of the spectrophotometric met...

Molecular structure, isomerism, conformational stability and intramolecular hydrogen bonding (IHB) of cis-enol forms of 1-(n-pyridyl)butane-1,3-diones (nPBD) (n = 2, 3, or 4) have been investigated by means of density functional theory (DFT) calculations. Energy differences for all possible nPBD cis-enol forms of isomers with respect to the most stable form of the correspondin...

Mukaiyama Michael addition of silyl enol ethers 13 to the 1,2-quinone-4-carboxylate 6 (formed in situ by oxidation of the catechol ester 8) afforded the 2-subsituted 7-hydroxybenzofuran-4-carboxylates 14 in fair to good yields. Alkyl and aryl systems work well, but highly electron-rich silyl enol ethers could not be used because of competing oxidation.

An efficient method for the synthesis of enol ethers and enecarbamates has been developed based on catalytic hydrosilane reduction of alpha-phosphonoxy enol ethers and alpha-phosphonoxy enecarbamates. This method has been applied to the total syntheses of two isoindolobenzazepine alkaloids, lennoxamine and chilenine.

Pro-Val pseudo dipeptides incorporating protio and halo enol lactones were tested for inhibitory activity against the serine proteases human leukocyte elastase (HLE), porcine pancreatic elastase, alpha-chymotrypsin, trypsin, thrombin, and urokinase. The protio enol lactones 1a-c were found to be HLE substrates but were poor alternate substrate inhibitors. The bromo enol lactone trans isomer 2a ...

Photoexcitation with blue light of the flavin chromophore in BLUF photoreceptors induces a switch into a metastable signaling state that is characterized by a red-shifted absorption maximum. The red shift is due to a rearrangement in the hydrogen bond pattern around Gln63 located in the immediate proximity of the isoalloxazine ring system of the chromophore. There is a long-lasting controversy ...

Stereoselective formation of substituted 1,3-dioxolanes was achieved through an assembly of three components: alkene, carboxylic acid and silyl enol ether. The reaction proceeded via stereospecific generation of a 1,3-dioxolan-2-yl cation intermediate during oxidation of alkene substrates with hypervalent iodine. The stereoselective trapping of the cation intermediate with silyl enol ether comp...