5415-73-6Relevant academic research and scientific papers
Reactions of carbonyl compounds in basic solutions. Part 32. The Perkin rearrangement
Bowden, Keith,Battah, Sinan
, p. 1603 - 1606 (1998)
The Perkin rearrangement of 3-halocoumarins to benzofuran-2-carboxylic acids, catalysed by base, proceeds in two separate stages. The first stage is a relatively rapid base-catalysed ring fission of the 3-halocoumarins to give (E)-2-halo-3-(2-hydroxyphenyl)acrylic acids. Rate coefficients have been measured for the base-catalysed ring fission of 6-substituted and 4-methyl-3-bromocoumarins and of 3-chlorocoumarin in 70% (v/v) dioxane-water at various temperatures. The second stage is a relatively slow cyclisation process. Rate coefficients have been measured for the cyclisation of the same series of substrates in 70% (v/v) dimethyl sulfoxide-water at various temperatures. The enthalpies and entropies of activation have been evaluated. The Hammett reaction constant for the ring fission at 30.0°C is 2.34 and for the cyclisation at 60.0°C is -3.54. The ring fission appears to occur by rate-determining addition of hydroxide anion to the carbonyl group, followed by a relatively rapid ring opening process; while the cyclisation probably proceeds by rate-determining fission of the carbon-halogen bond, following formation of a relatively unstable carbanion intermediate formed by intramolecular nucleophilic attack on the vinyl group by the phenoxide anion.
Development of new pyrrolocoumarin derivatives with satisfactory fluorescent properties and notably large stokes shifts
Chen, Lei,Hu, Tai-Shan,Yao, Zhu-Jun
supporting information; experimental part, p. 6175 - 6182 (2009/05/27)
Small, organic, fluorescent molecules with large Stokes shifts and long emission wavelengths are ideal dyes for various modern fluorescent imaging technologies such as FRET. In this study, we designed and synthesized a number of new fluorescent molecules
