Substituted 2,4,4,6-tetraphenyl-4H-selenopyrans: preparation, photocolouration and 4H-selenopyran ring geometry; an X-ray and DFT calculation study†
Abstract
1,5-Diaryl-3,3-diphenylpentane-1,5-diones 3a–d react with Al2Se3–HCl–AcOH reagent to give the 2,6-diaryl-4,4-diphenyl-4H-selenopyrans 4a–d in satisfactory yields while the same procedure starting from 1,5-diketone 5 affords small amounts of spiroheterocycle 6. 2,4,4,6-Tetraphenyl-4H-selenopyran 4a can be brominated or nitrated at positions 3 and 5 to give substituted derivatives 7–9. Dibromo derivatives 4c and 7 were converted with