Novel keto–enol tautomerism in 1,3,5-trihydroxybenzene systems

Abstract

We report a new synthesis of the water-soluble compound 1,3,5-trihydroxy-2,4,6-trimethylsulfonic acid (1), which exists in two tautomeric forms (60:40::enol%:keto%) and can be used as a proton conductor. Quantum chemical calculations...

Photoinduced Irreversible Intramolecular Proton Transfer of Arnebinones B, D, and E: The Case of Photoenolization at the p-Benzoquinone-CH2/CH-π System

“…Keto–enol tautomerism is a typical and thoroughly studied example of intramolecular proton transfer , that is extremely important in biochemistry, materials, and synthetic chemistry. − Photoinduced interconversion between a ketone and an enol is an appealing tool owing to its noninvasive and green properties. The two reported classical photoinduced keto–enol tautomerism reactions are excited-state intramolecular proton transfer − (ESIPT, Scheme A) and photoenolization , (Scheme B).…”

Facile synthesis of O-acylhydroxamates via reaction of oxime chlorides with carboxylic acids

“…Then, this nitrile oxide intermediate A reacts with carboxylic acid 2 to afford intermediate E. Finally, the intermediate E would transform into the desired product 3 via ketoenol tautomerization. 13 In conclusion, we have developed a mild, practical and efficient protocol to prepare a broad range of functionalized Oacylhydroxamates in high yields (up to 85%) from oxime chlorides and carboxylic acids. In addition, the methodology allows the synthesis of O-acylhydroxamates on a gram scale.…”

“…This revealed that DABCO was the most suitable base for this reaction (entries 2-5). To further improve the product yield, a series of different solvents were screened (entries [6][7][8][9][10][11][12][13]. The results showed that product 3a was provided in a moderate yield in Et 2 O, toluene, DCE and CHCl 3 (entries 6, 9, 11 and 13).…”

“…Additionally, the position of the substituent on the phenyl ring of benzoic acid 2 seemed to have a slight effect on the outcome of this reaction. For example, a para-bromo substrate led to a higher yield (3o, 70%) than the corresponding ortho-and meta-bromo substrates (3m, 67%; 3n, 67%, respectively) (entries [13][14][15]. Some heterocyclic carboxylic acids such as thiophene-2-carboxylic acid and 2-naphthoic acid could also afford the desired products in good yields.…”

“…Then, this nitrile oxide intermediate A reacts with carboxylic acid 2 to afford intermediate E. Finally, the intermediate E would transform into the desired product 3 via keto–enol tautomerization. 13 …”