Dimethyl t-butylsilyl enol ethers of cycloalkanones react with ethyl propynoate in the presence of ZrCl4 to give protected cyclobutenic hydroxy esters. Cyclopropanation by cycloaddition of diazoalkanes followed by sensitized photocleavage, leads to bicyclo [2.1.0] pentan-2-ol derivatives which are then cleaved with acids to 3-cyclopenten-1-ols. This reaction sequence was used for the synthesis of the
Diazoalkanes react with electrophilic cyclobutenes by a 1,3-dipolar cycloaddition to Δ−1 pyrazolines. After photolysis and acidic solvolysis polyfunctionalized diquinanes are obtained.
Synthesis of polyquinanes via bicyclo [2.1.0] pentane intermediates. An easy access to optically pure diquinane alcohols of known absolute configuration.
The resolution of the cyclobutenic ester 1 using chiral lactols is described. After a stereospecific reaction sequence (cyclopropanation followed by an acidic solvolysis), the enantiomerically pure diquinanes 10 are obtained.