Structure and photochemistry of four adamantylacetophenones

The photochemistry and crystal structures of four alpha-adamantylacetophenones have been studied, namely, 1-(4-fluorophenyl)-2-(tricyclo[3.3.1.1(3,7)]dec-1-yl)ethanone [(1a), C18H21FO], 1-(4-cyanophenyl)-2-(tricyclo[3.3.1.1(3,7)]dec-1-yl)ethanone [(1b), C19H21NO], 1-(4-cyanophenyl)-2-(3-methyltricyclo[3.3.1.1(3,7)]dec-1-yl)ethanone [(1c), C20H23NO] and 1-(4-carboxyphenyl)2-(3-methyltricyclo[3.3.1.1(3,7)] dec-1-yl)ethanone [(1d), C20H24O3]. All four molecules adopt fairly similar conformations, with short gamma H...O contacts permitting hydrogen abstraction in the photochemical reactions. However, three of the compounds, (1a), (1b) and (1d), are photostable in the solid state and possible reasons for this unreactivity are considered.