An unexpected Diels-Alder type cycloaddition of cyclic enone ethylene ketals

The ethylene ketal of 2-cyelopentenone and 2-cyelohexenone in acetonitrile in thepresence of a trace of an acid rapidly undergoes the Diels-Alder type dimerization,Theproducts are regiospecific but not stereoselective and are hydrolysed sequentially to affordketo-ketals and diketones whose structures are determined by extensive applications of NMRspectroscopy.

An unexpected Diels-Alder type cycloaddition of cyclic enone ethylene ketals

The ethylene ketal of 2-cyclopentenone and 2-cyclohexenone in acetonitrile in the presence of a trace of an acid rapidly undergoes the Diels-Alder type dimerization. The products are regiospecific but not stereoselective and are hydrolysed sequentially to afford keto-ketals and diketones whose structures are determined by extensive applications of NMB spectroscopy.