Cyclodienyl 1,3-Dianionic Synthons: A Novel Synthesis of 5,5-Dimethyl- 1,3-Bis-(trimethylsilyl)cyclohexa-1,3-diene and its Diels-Alder [π4s+π2s] Cycloadditions with Six Dienophiles

The synthesis of 5,5-dimethyl-1,3-bis(trimethylsilyl)cyclohexa-1,3-diene: a novel cyclic 1,3-dianionic synthon is reported by the Wurtz-Fittig coupling reaction of 1,3-dichloro-5,5-dimethylcyclohexa-1,3-diene with metallic sodium and chlorotrimethylsilane in anhydrous ether solvent. The compound on further Diels-Alder [π4s+π2s] cycloaddition with five N-substituted maleimides gave five novel cycloadducts: the N-substituted 11,11-dimethyl-1,8-bis(trimethylsilyl)-4- azatricyclo[5.2.2.02,6]undec-8-ene-3,5-diones; and reaction with maleic anhydride yielded the novel 11,11-dimethyl-1,8- bis(trimethylsilyl)-4-oxotricyclo[5.2.2.02,6]undec-8-ene-3,5-dione in 94-97% overall yields.