π-Electron conjugation effects in antiaromatic dehydro[12]- and aromatic dehydro[18]-annulenes

Abstract

N,N-Dimethylanilino-substituted perethynylated dehydro[12]- and dehydro[18]-annulenes were prepared by oxidative acetylenic coupling of cis-bisdeprotected tetraethynylethene derivatives obtained by a new photochemical route; they display strongly bathochromically shifted longest-wavelength absorption bands compared to their silyl-substituted counterparts resulting from efficient intramolecular charge-transfer between the peripheral π-electron donors and the electron-accepting central acetylenic core.