The Cyclobutadiene Problem

Cyclobutadiene has recently become the center of reawakened interest. By use of the matrix isolation technique, cyclobutadienes can now be prepared as monomers frozen in matrices. Thus both the unsubstituted parent compound and its alkyl-substituted derivatives are amenable to study. The present progress report surveys the entire field; however, particular emphasis is placed on the author's own results from investigations concerning this classical problem of organic chemistry.