Organic Communications Articles

This review presents a systematic and comprehensive survey of the chemical reactivity of 3-acyl(aroyl) coumarins. The target compounds are important intermediates for the synthesis of a variety of synthetically useful and novel heterocyclic systems with different ring sizes such as isoxazole, pyrazole, 3H-triazolium salts, pyrimidine, pyridine, quinolone, benzoxocin, benzoxonin and benzoxepin.

In this study, ionic liquids (ILs) were first used as solvents for conversion of hesperidin into diosmin. The diosmin was successfully synthesized by using iodine oxidation in ionic liquids including [BMIM]Br, [BMIM]BF4, [BMIM]OTf, [BPY]Br, [BPY]BF4 and [BPY]OTf.  The results showed the reaction achieved in good yields (57- 76%). Among them, [BPY]Br and [BPY]BF4 exhibited as excellent solvents for the oxidation of hesperidin. In particular, water content in recovered ionic liquids (ILs), which affected strongly recyclable performance in the oxidation of hesperidin, has been investigated. It found that water content in [BPY]Br  from 1 % to 5% (v/v) induced a significant increase of the synthetic yield.

A green and efficient procedure was established to synthesize 1,4-dihydropyridines via one-pot Hantzsch reactions in buffering conditions without the use of organic solvent. In this method, a buffer solution was used as solvent and catalyst reaction; therefore, using this method has several benefits including high yields, an environmentally friendly procedure, short reaction times, and a simple work-up procedure. All the compounds were characterized by TLC, FT-IR, 1H NMR and elemental studies. 

Density functional theory calculations were employed to explore the ring–opening reaction mechanisms of mono germanium analogues of cyclopropylidenoids via Doering–Moore–Skattebøl method. The theoretical findings revealed that the stepwise fashion with the intermediacy of a free germacyclopropylidene is operative for the structure with germanium atom on the carbenic position (1). Moreover, the cyclopropylidene analogue (4) of the title structures proceeds via concerted manner for the corresponding ring-opening reaction. The calculated overall energy barrier to trigger the stepwise ring-opening reaction for 1 is strongly higher than the concerted fashion for 4. Additionally, the effect of halogens (X = F, Cl, Br) on the reaction mechanism were also investigated. The energy barriers for chlorine substituted precursors are found to be lower than the fluorine and bromine substituted forms.