trimethylenecyclopropane wherein all six hydrogen atoms are symmetrically substituted with cyano , alkoxycarbonyl or carbacyl groups and which are salt - forming can be made by reacting tetrachlorocyclopropene with the appropriate active methylene compound such as malononitrile , acetyl acetone or ethyl cyanoacetate . using limited amounts of malononitrile and a tertiary amine , a tetracyanodimethylenecyclopropene substituted with a quaternary ammonium group is obtained , which reacts with other active methylene compounds including the above , nitroalkanes , benzoylacetonitrile , benzenesulfonylacetonitrile , and dialkyl sulfones to form unsymmetrical substituted trimethylenecyclopropane . the neutral compounds are useful as organic oxidants . their radical anion salts are useful as organic conductors and as dyes , and the dianion salts are useful as image formers on transparent films or on opaque substrates .