Photocycloaddition of 4-(Alk-1-ynyl)-Substituted Coumarins and Thiocoumarins to 2,3-Dimethylbuta-1,3-diene
摘要:
AbstractOn irradiation (350 nm) in the presence of 2,3‐dimethylbuta‐1,3‐diene (8), 4‐(alk‐1‐ynyl)coumarins 1 afford mixtures of cyclobuta‐ and cycloocta‐annulated products 9 and 10, respectively. In contrast, the corresponding thiocoumarins 2 react with the same diene chemoselectively to give cyclohexa‐annulated products 11.
intermediates for the synthesis of heterocyclic compounds. For instance, 1-morpholino-3-phenyl-1,3-propanedione, 1-phenyl-3-piperidino-1,3-propanedione, 1-phenyl-3-pyrrolidino-1,3-propanedione, 1-piperidino-1,3-butanedione, 1-morpholino-2-phenyl ethanone were used in these reactions to produce 2-pyrone derivatives. In addition, the preparation of 4-hydroxy-3-phenylthiochromeno[4,3-b]pyran-2,5-dione derivatives