Fries rearrangement of methoxyphenyl 3‐methylbut‐2‐enoates

Abstract

Fries rearrangement of 2‐, 3‐ and 4‐methoxyphenyl 3‐methylbut‐2‐enoates 3‐5 in methanesulfonic acid, polyphosphoric acid, aluminum chloride and under photochemical conditions have been studied. The outcome of the reactions was determined by the substitution pattern in the starting products and the reaction conditions used. Under Lewis acid catalysis, acylation accounted for the major components of the reaction mixtures, leading to the formation of indanones and 2,3‐dihydro‐4H‐1‐benzopyran‐4‐ones respectively in the case of o‐ and m‐esters 3 and 5, whereas alkylation to afford dihydrocoumarins was the favored path for p‐ester 5. On the other hand, o‐acylation was in all cases the major reaction course in the photochemical rearrangement.

Trifluoroacetic Acid-Mediated Hydroarylation: Synthesis of Dihydrocoumarins and Dihydroquinolones

“…In these cases, hydroarylation generally occurs within 24−40 h at 24 °C and provides high yields of dihydroquinolones. Prior to this work, the acid-catalyzed cyclization of aryl cinnamates was largely limited to catalysis by polyphosphoric acid (PPA), which generally proceeds in moderate yield (22−90%; 51% average); dihydrocoumarin byproducts have also been observed in Fries rearrangements of aryl 3-methylbut-2-enoates catalyzed by methane sulfonic acid . Similarly, the thermal (120−190 °C) cyclizations of cinnamanilides have been reported in the presence of PPA .…”

Syntheses and Biological Activities of Chroman-2-ones. A Review

“…have been employed. [111][112][113][114][115][116][117][118] Synthetic methods for the preparation of dihydrocoumarins from phenols and various Michael acceptors via route C are summarized in Table 2. The condensation of phenols with cinnamic acid to give 4-aryl-3,4-dihydrocoumarins using sulfuric acid in acetic acid was first demonstrated by Liebermann and Hartmann.…”

Lewis Acid-Catalyzed Diastereoselective Hydroarylation of Benzylidene Malonic Esters

“…Hydroarylation of cinnamic acid derivatives is a powerful method for the formation of synthetically versatile dihydrocoumarin derivatives. − However, such hydroarylations are commonly carried out in highly acidic media and the substrate scope can be limited . For example, the CF 3 CO 2 H-catalyzed hydroarylation of cinnamic acids is limited to electron-rich cinnamic acids .…”