Mechanism of light-induced reductive acetylation of 1,2-naphthoquinone with acetaldehyde

The detailed mechanism of the photochemical reaction of 1,2-naphthoquinone with acetaldehyde has been investigated. From a study of the reaction using the 1H CIDNP technique and change of the product distribution with temperature, it was deduced that the almost all parts of the reaction proceed via an ‘in-cage’ mechanism at a low temperature, but at 20 °C at least 6.7% of the reaction proceeds via an ‘out-of-cage’ mechanism. For comparison, the addition of thermally generated acetyl radical to 1,2-naphthoquinone has also been examined.