TETRACYANOETHYLENE OXIDE .4. NUCLEOPHILIC RING OPENING

Most reactions of nucleophiles with tetracyanoethylene oxide (TCNEO) involve fragmentation of the ring. Examples are given of reactions with amines, thiocarbonyl compounds, benzylideneaniline, and benzophenone azine. The amine reaction gives the same products as the reaction of the amines with carbonyl cyanide. The products from TCNEO and thiocarbonyl compounds depend on the substituents attached to the thiocarbonyl group. Thus, thiourea gives a stable thiouronium ylide whereas with thiobenzophenone, sulfur is eliminated with the formation of a dicyanoethylene. The reaction of TCNEO with benzylideneaniline takes two pathways. One gives an addition product with loss of hydrogen cyanide. The second involves ring scission to form a 1,3 dipole that adds a second molecule of benzylideneaniline. The benzophenone azine reaction, however, takes a different course and gives nitrogen, 1,1-dicyano-2,2-diphenylethylene, and the epoxide of this olefin. Acetic anhydride and acetyl chloride add to TCNEO to give ring-opened products without fragmentation. Benzaldehyde and TCNEO form a 1:1 addition product believed to be a cyclic acetal. © 1969, American Chemical Society. All rights reserved.