Interactions between alkynes and methoxy or dimethylamino groups in peri-naphthalene systems

Abstract

X-Ray studies of a series of 1-ethynyl-8-methoxynaphthalenes with varying functional groups at the alkyne terminus show only small changes in the 1,5 MeO⋯spC contact distances (2.593–2.663 Å) despite the different through-bond electron-attracting powers of the terminal substituents. Replacement of methoxy with dimethylamino led to a chemical reaction when the alkyne's activating group was a carboxylic ester. The 1,5 N⋯spC interaction between a dimethylamino group and a triphenylsilylethyne group has a 1,5 Me₂N⋯spC contact distance ca. 0.12 Å longer than for the corresponding methoxy case, indicative of a primarily steric interaction.