[4 + 2] Dimerization and Cycloaddition Reactions of alpha,beta-Unsaturated Selenoaldehydes and Selenoketones. Academic Article uri icon


  • The reactions of alpha,beta-unsaturated aldehydes and ketones with bis(dimethylaluminum) selenide, (Me(2)Al)(2)Se, yield the corresponding alpha,beta-unsaturated selenoaldehydes and selenoketones. They are too unstable to be isolated in the monomeric form, but they undergo regioselective [4 + 2] dimerization via a "head-to-head" oriented transition state to afford diselenin derivatives (trans and cis isomers). Theoretical calculations at the density functional theory level show that this selectivity occurs because the "head-to-head" dimerization is thermodynamically favored over the "head-to-tail" by about 14 kcal/mol. Both dimerization reactions have low energy barriers: 1.5 and 2.8 kcal/mol for the former and 0.9 and 1.3 kcal/mol for the latter. In the presence of norbornadiene, these compounds function as 4pi heterodienes (C=C-C=Se) to give the respective cycloadduct products. On the other hand, they act as 2pi dienophiles (C=Se) in the reactions with cyclopentadiene except for selenoacrolein which serves as a 4pi diene and only one C=C bond (2pi) in cyclopentadiene is involved in the reaction. Theoretical calculations have been carried out in order to better understand these observations.

published proceedings

  • J Org Chem

author list (cited authors)

  • Li, G. M., Niu, S., Segi, M., Zingaro, R. A., Yamamoto, H., Watanabe, K., Nakajima, T., & Hall, M. B.

citation count

  • 33

complete list of authors

  • Li, Guang Ming||Niu, Shuqiang||Segi, Masahito||Zingaro, Ralph A||Yamamoto, Hiroaki||Watanabe, Kentaro||Nakajima, Tadashi||Hall, Michael B

publication date

  • March 1999