In a combined study on the photophysics of 2-(2'-hydroxyphenyl)-benzothiazole (HBT) in polar acetonitrile utilizing ultrafast infrared spectroscopy and quantum chemical calculations, we show that a branching of reaction pathways occurs on femtosecond time scales. Apart from the excited-state intramolecular hydrogen transfer (ESIHT) converting electronically excited enol tautomer into the keto t...

The idea of the enol form of nucleotides being responsible for the formation of some noncanonical pairs was put forward by Watson and Crick in their first paper on DNA structure [1]. In the context of this hypothesis, the GU pair may contain either the enol form of uracil and the keto form of guanine or the enol form of guanine and the keto form of uracil. Later, in 1966, Francis Crick proposed...

Photodecarboxylation of p-benzoylphenylacetic acid in aqueous solution produces the elongated enol 5, whose strength as an oxygen acid (pQ(E/a)= 7.67) makes it more acidic than simple enol analogs by several orders of magnitude.

Key words palladium catalysis - silyl enol ethers α,β-unsaturated carbonyls

The titular compound was characterized for the first time using a full range of spectroscopic methods, including UV, IR, 1H, and 13C NMR spectra. In solution, all methods showed keto–enol equilibrium strongly shifted to enol form. X-ray structures determined simple 2-oxosuccinates only form packed as hydrogen-bonded dimer stacks.

SYNLETT 2010, No. 11, pp 1712–1716xx.xx.2010 Advanced online publication: 14.06.2010 DOI: 10.1055/s-0030-1258094; Art ID: Y00510ST © Georg Thieme Verlag Stuttgart · New York Abstract: The use of high-throughput screening allowed for the optimization of reaction conditions for the palladium-catalyzed asymmetric decarboxylative alkylation reaction of enolate-stabilized enol carbonates. Changing t...

The inversion of the keto-enol stability order of dialuric acid on ionization was calculated and verified experimentally. The radical cations in both forms were characterized. The spectrum of the keto form was observed upon direct ionization of dialuric acid under matrix conditions, whereas the enol form was formed upon a sequential electron-proton-proton attachment to alloxan under acidic aque...

We observed that the unstable 13, 17-cyclopheophorbide a enol is one of the most abundant pigments in recent sediments (Black Sea, Mediterranean Sea, Peru margin) and here we report its isolation and structure determination (high-performance liquid chromatography, ultraviolet-visible spectrometry, mass spectrometry, and nuclear magnetic resonance). This enol has been considered as the precusor ...

The DFT calculations at the B3LYP level with 6-311G** basis set were carried out in order to reveal whether tautomerization or decarboxylation is responsible for the instability of 2,2-di(pyridin-2-yl)acetic (DPA) and 1,8-diazafluorene-9-carboxylic (DAF) acids. The carboxyl protons in both compounds are involved in the intramolecular hydrogen bonds (the pyridine nitrogen atoms are the hydrogen ...

The use of high-throughput screening allowed for the optimization of reaction conditions for the palladium-catalyzed asymmetric decarboxylative alkylation reaction of enolate-stabilized enol carbonates. Changing to a non-polar reaction solvent and to an electron-deficient PHOX derivative as ligand from our standard reaction conditions improved the enantioselectivity for the alkylation of a keta...