Introduction No definite evidence for cross-ring n-type electron interaction was found in a study of 1, 3-dimethylenecyclobutane2 although LCAO calculations suggest that such interaction might lead to a small but significant delocalization energy. Substitution of a more electronegative group isoelectronic with the methylene group for one of the methylene groups of 1, 3-dimethylenecyclobutane would be expected to lead to a larger, and ...
