Regular Acyclic and Macrocyclic [AB] Oligomers by Formation of Push-Pull Chromophores in the Chain-Growth Step

The substrate scope of the [2+2] cycloaddn.-cycloreversion (CA-CR) reaction between electron-deficient (2,2-dicyanovinyl)benzene (DCVB) or (1,2,2-tricyanovinyl)benzene (TCVB) derivs. and N,N-dimethylanilino (DMA)-substituted acetylenes was studied. The structural features of the cyanobutadiene products of these transformations were examd. and the rates of selected CA-CR reactions were measured. Rate consts. for reactions using pentafluorinated TCVB and DCVB are one to two orders of magnitude larger than those for the unsubstituted analogs. Multiple, consecutive CA-CR reactions were performed with substrates incorporating two reactive 2,2-cyanovinyl or 4-ethynylanilino sites. 1,4-Bis(2,2-dicyanovinyl)-2,3,5,6-tetrafluorobenzene and 1,4-bis[(4'-dihexylamino)phenylethynyl]benzene were selected as suitably reactive monomers for the synthesis of regular [AB] oligomers wherein the push-pull chromophores were formed in the chain-growth step. Oligomers of two types were isolated: macrocyclic [AB]n and open-chain B[AB]n oligomers, with n ≤ 4.