1,5-Bis(trimethylsiloxy)-1,5-dimethoxy-1,4-pentadienes. cyclopropane synthesis via intramolecular coupling.

The title compounds ($\text{1}$a–e) can be prepared in good yield by silylation of the dianions of dimethyl glutarates ($\text{2}$a–e). On treatment with titanium tetrachloride, they cyclise stereoselectively to dimethyl $\text{trans}$-cyclopropane-1,2-dicarboxylates.