A convenient synthesis of symmetric 1,2-diarylethenes from arylmethyl phosphonium salts.

Symmetric ethenyldithiophenes are important intermediates for synthesis of photochromic materials and organic conductors. When acetonitrile is used as a solvent, 3-methylthiophenylphosphonium salts form symmetric ethenyldithiophenes in the presence of a strong base (e.g., NaH, (t)BuOK) in moderate to high yields. This homocoupling reaction is faster than a Wittig reaction with aromatic ketones in acetonitrile. Our study shows that the presence of polar aprotic solvents promotes the homocoupling reaction.

1-[2-(2-hydroxyalkyl)phenyl]ethanone: a new photoremovable protecting group for carboxylic acids.

[reaction: see text] A new photoremovable protecting group for carboxylic acids is introduced. The protecting group 1-[2-(2-hydroxyalkyl)phenyl]ethanone, HAPE, is used to protect various carboxylic acids. When photolyzed, the protected compound releases the acid in 70-85% isolated yields. The synthesis and the results of photorelease of the protected acids are presented here.