A General Synthesis of <i>N</i>-Vinyl Nitrones

A general synthesis of a new type of heterodiene, the N-vinyl nitrone, is described. The synthetic sequence
begins with the conjugate addition of benzeneselenol to nitroalkenes (in turn derived from Henry reaction
of an aldehyde and a nitroalkane) to provide 2-selenenylnitroalkenes. These selenonitroalkanes are reduced
to the corresponding hydroxylamines which are combined with aldehydes to form nitrones. The
phenylselenenyl-containing nitrones are then oxidized to selenoxides which undergo syn-selenoxide
elimination to provide N-vinyl nitrones. Three X-ray crystal structures of substituted N-vinyl nitrones
were obtained. In addition, the first [4+2] cycloaddition of an N-vinyl nitrone is reported.