Incipient Nucleophilic Attack on a Carbonyl Group Adjacent to a Stereogenic Centre in Peri Naphthalene Derivatives

The crystal structures of four peri-naphthalene derivatives model the Felkin-Anh approach of a nucleophilic centre (OH or NMe2) to a carbonyl group attached to a stereogenic centre bearing a large (phenyl), medium (methyl) and a small (hydrogen) group. Thus, the conformation about the (O=)C-C* bond directs the phenyl group approximately perpendicular to the carbonyl group and away from the nucleophile, whose line of approach lies close to the hydrogen atom attached to the stereogenic centre. The nucleophile approaches the carbonyl group at 102.99(11)-112.34(9)degrees (for NMe2) and at 118.56(14)degrees (for OH). The small pyramidalization of the carbonyl carbon towards the nucleophile increases as the nucleophilic centre approaches closer.