The Helicenes

“Helicene” is the name introduced by Newman in 1955, to describe the benzologues of phenanthrene in which the extra ortho-condensed rings give rise to a (regular) cylindrical helix. The pioneer work of Newman in this field cannot be overemphasized; his brillant synthesis and resolution of [6]helicene, achieved eighteen years ago, will remain as a landmark, for it opened the way to the study of a fascinating class of synthetic molecules. In the following review, an attempt is made to summarize the present state of our knowledge in this rapidly expanding field.