Nucleophilic Addition and [3+2] Cycloaddition to Carbonyl Oxides

Carbonyl oxides are generated during the ozonolysis of alkenes. In the presence of nucleophiles suc as alcohols, a-alkoxyhydroperoxides are formed. The use of alkenols in these reactions has yet to be fully investigated. In our work, various cycloalkenes were ozonolyzed in the presence of alkenols to generate the corresponding a-alkoxyhydroperoxides. Allylic, homoallylic, secondary allylic, and secondary homoallylic alkenols were used to generate a variety of terminally differentiated aldehyde-ester-alkenes in good to low yield. A method for determining an optimal time of ozone addition and ideal ozonolysis conditions for our reaction were also determined. Carbonyl oxides can also undergo [3+2] cycloaddition with a suitable 1,3-dipolarophile. The ozonolysis of vinyl ethers can leas to the formation of 3-alkoxy-1,2-dioxolanes via [3+2] cycloaddition. Acid-catalyzed ring-opening of the dioxolane can then form aldol products. In this study, we ozonolyzed ethyl vinyl ether to generate 3-ethoxy-1,2-dioxolane. Careful control of ozone additiongave optimal yields. Both p-TsOH and Amerlyst-15 were used in the acid-catalyzed ring-opening of the dioxolane. We found that p-TsOH gave ethyl-3-hydroxypropanoate in higher yield and simplified the work-up conditions. Optimal oxonolysis conditions and the importance of oxonation time are yet to be determined