Synthesis of tetraketones in water and under catalyst-free conditions

One-pot synthesis of pyrano[3,2-c]quinoline-2,5-dione derivatives by Fe3O4@SiO2-SO3H as an efficient and reusable solid acid catalyst

“…The second weight loss between 150 and 500°C can be attributed to the loss of SO 3 H groups. The occurrence of further weight losses at the temperature higher than 600°C was likely a consequence of the decomposition of silica shell [32]. These results demonstrate that the catalyst is stable up to approximately 250°C, supporting that it could be safely applied in organic reactions at the temperatures range 70-150°C.…”

A Green and Highly Efficient Protocol for Catalyst‐free Knoevenagel Condensation and Michael Addition of Aromatic Aldehydes with 1,3‐Cyclic Diketones in PEG‐400

“…After the Knoevenagel condensation, the intermediate is transformed to the product (Scheme 2). 16 To check the versatility of this method we had also We have also successfully applied this new methodology on a larger scale. For example up to 20 mmol benzaldehyde could produce 5,5-dimethyl-2-((4,4-dimethyl-2-oxocyclohexyl)(phenyl)methyl)cyclohexanone with yield up to 80%.…”

“…15 Very recently, the synthesis of tetraketones in water was reported, which produced 2,2'-(arylmethylene) dicyclohexane-1,3-diones in 64%-99% yields at room temperature for 0.5-4 h. 16 The protocol provides several features including use of water without any catalyst. Compared with the related procedure in water, PEG could reduce the time of the reaction.…”

Sulfamic acid-catalyzed, environmentally benign synthesis of bis-tetronic acids at ambient temperature

“…1A) results from the reaction between salicylaldehydes with two equivalents of cyclic-1,3-diones [14][15][16][17][18][19][20], while tetraketones ( Fig. 1B) result from the reaction between the same diketones with aromatic aldehydes, devoid of the ortho-hydroxyl group [21][22][23][24]. Among these, 1-oxo-hexahydroxanthenes are known for their important pharmacological properties, such as anti-estrogenic, antimicrobial, hypoglycaemic, antibacterial and thrombin inhibitory activities and serve as neuropeptide YY5 receptor antagonists [25][26][27][28], while tetraketones are known to possess antitumor activity [29][30][31][32].…”