Cage compounds. A ready synthesis of a highly substituted basketane

Abstract

The Diels–Alder adduct, endo-2,3-dichloro-4a,8a-dicyano-4a,5,8,8a-tetrahydro-5,7-dimethyl-5,8-(2,2-dimethylethano)-1,4-naphthoquinone (1) undergoes ready intramolecular photocycloaddition to afford 2,7-dichloro-4,5-dicyano-1,9,11,11-tetramethylpentacyclo[6.4.0.0^2,7.0^4,12.O^5,9]dodecane-3,6-dione (2) in 72% yield. Upon treatment with excess of sodium methoxide in refluxing methanol, (2) undergoes a complex sequence of reactions to afford dimethyl 7,8-dicyano-1,5,10,10-tetramethyltricyclo[4.2.2.0^2,5]deca-3,7-dine-3,4-dicarboxylate (3) in 85% yield. Intramolecular photocycloaddition of (3), affords the basketane, dimethyl 6,7-dicyano-1,3,9,9-tetramethylpentacyclo[4.4.0.0^2,5.O^3,8.O^4,7]decane-4,5-dicarboxylate (4), in 84% yield, thus providing a ready synthesis of a uniquely substituted member of this series.