The stereospecific preparation of (E)-1-aryl-F-1,3-butadienes

The Pd (PPh3) 4/Cu(I)I catalyzed cross coupling of (Z)-1-tri-n-butylstannyl-1,2,3,4,4-pentafluoro-1,3-butadiene with substituted aryl iodides provides a useful stereospecific route to (E)-1-aryl-1,2,3,4,4-pentafluoro-1,3-butadienes. Substituents, such as 4-nitro, 2-nitro, H, 3-CF3, 3-OCH3, 2-CH3, 1-iPr react stereospecifically with the dienyl stannane synthon. Only with a bulky electron-withdrawing substuent, such as 2-CF3, did significant isomerization occur in isolation of the aryl diene. The bis-coupled product is formed stereospecifically with 1,4-diiodobenzene. The methodology could be extended to stereospecifically prepared the 1-triethylsilyl-1E,3E,-1,2,3,4,5,6,6-heptafluoro-1,3,5-hexatriene synthon.