Electronic effects on the substitution reactions of benzhydrols and fluorenyl alcohols. Determination of mechanism and effects of antiaromaticity

Abstract

A range of substituted benzhydrols and fluorenols were prepared and subjected to acid catalysed methanolysis. Analysis of the rates of each of these processes showed correlation with Hammett σ(+) parameters as is consistent with the significant build-up of positive charge adjacent to the ring. In combination with the similarity of the electronic susceptibility of the processes, these data suggest that both reactions proceed through a unimolecular rate-determining step. This shows that the effect of fusion of the phenyl systems (and hence potentially introducing an antiaromatic carbocation intermediate) is only to slow the rate of reaction rather than change the mechanism of the process.

The application of aromaticity and antiaromaticity to reaction mechanisms

“…Further studies show that the NICS(0) values for the unsubstituted 4 H -pyrazole and the fluorinated one were 0.5 ppm and 6.2 ppm, respectively, whereas that of silylated 4 H -pyrazole was −3.3 ppm, suggesting the hyperconjugative antiaromaticity induced by fluorination of 4 H -pyrazole. In addition, Harper and co-workers found that the antiaromaticity dramatically affects the rate of the acid catalyzed methanolysis of a series of substituted benzhydrols and fluorenols even though they undergo the same reaction mechanism [70] .…”

Fluorenone imidazolium salts as novel de Vries materials

“…As shown in Scheme 3, the synthesis commenced with a sequential Suzuki cross coupling 82 of methyl 6-bromo-3methoxybenzoate 6 with known borolanes 7a-f [83][84][85] to give the biphenyl esters 8a-f. Subsequent saponication 86 provided biphenyl carboxylic acids 9a-f, which were submitted to Friedel-Cras acylation 87 via activation with thionyl chloride and reaction with AlCl 3 to give the uorenones 10a-f. For the selective deprotection of the methyl ether 10a-e two protocols employing thiols were examined.…”

Exploration of Novel Urolithin C Derivatives as Non-Competitive Inhibitors of Liver Pyruvate Kinase

“…The compound was synthetized following the literature procedure [ 33 ]. To a solution of 200 (0.30 g, 0.60 mmol) in MeOH (30.0 mL) was added H 2 SO 4 (0.5 mL).…”