3-Substituted 4-pyranones: a rapid approach using microwave heating

One‐Pot Synthesis of Multi‐Substituted 4‐Pyrones by a Gold‐ Catalyzed Cascade of Wolff Rearrangement/[4+2] Cycloaddition/ Elimination Reactions

“…The methyl carbon peak in 17f appeared at δ =11.6 ppm, whereas that in 17g was seen at δ =18.8 ppm. The spectral data of the synthesized compound 17g were in agreement with those of the previously reported compound 29. Similarly, reaction between 16c and ethyl 1‐propenyl ether in refluxing p ‐xylene for 15 h provided products 17h (30%) and 17i (22%).…”

“…Their structures were assigned by analyzing their spectral data and by comparison with the spectral data of a reported compound (Figure 3). 29 The 1 H NMR spectrum of 17f exhibited a methyl peak at δ =2.06 ppm, two vinylic protons at δ =7.80 (d, J =5.7 Hz) and 6.37 (d, J =5.7 Hz), and aromatic protons at δ =7.56–7.45 as multiplets, whereas that of 17g showed a methyl peak at 2.16 ppm, two vinylic peaks at 7.70 (d, J =5.7 Hz) and 6.40 (d, J =5.7 Hz), and aromatic peaks at 7.40 (2 H, t, J =7.2 Hz), 7.35 (1 H, d, J =7.2 Hz) and 7.23–7.21 (2 H, m). The identifications of 17f and 17g were further confirmed using their 13 C NMR spectral data.…”