C–C Bond-Forming and Bond-Breaking Processes from the Reaction of Diesters with Me₃SnLi. Synthesis of Complex Bridged Polycycles and Dialkyl Aromatic Compounds

1,2-Aromatic diesters can be transformed into strained bridged polycyclic structures by a two-step procedure consisting of an initial reductive alkylation promoted by alkaline metals, followed by a reaction of the resulting unsaturated diesters with Me₃SnLi. We propose that a stanna-Brook rearrangement plays a fundamental role in the formation of the polycyclic organotin acetals obtained. These unusual compounds could be further functionalized by tin–lithium exchange followed by alkylation of the newly formed tertiary carbanion. Alternatively, dialkylated aromatic hydrocarbons have been prepared via a decarbonilation reaction promoted by Me₃SnLi. 1,4-Aromatic diesters were reductively dialkylated and then transformed into norbornadienone derivatives by reaction with Me₃SnLi. Several stable dibenzonorbornadienones 41 have been prepared in just two steps starting from anthracene 38. The corresponding naphthalene analogues gave 1,4-dialkylnaphthalenes. The synthetic protocols described provide access to structures that are not easily obtained through existing synthetic methodologies.