Facial Selectivity in Cycloadditions of a Chiral Ketene Acetal under Microwave Irradiation in Solvent-Free Conditions. Configurational Assignment of the Cycloadducts by NOESY Experiments and Molecular Mechanics Calculations

Article abstract of DOI:10.1021/jo00118a037

(R)-4-Phenyl-2-methylene-1,3-dioxolane (1) undergoes 1,3-dipolar and Diels-Alder cycloadditions under microwave irradiation within 3 min with excellent yields, a simple purification procedure, and an interesting facial selectivity.The stereochemistry of these cycloadducts has been inferred by NOESY experiments and molecular mechanics calculations.X-ray structure determination was required in one case.Thermal isomerization of the cycloadducts was performed affecting only the spiro-carbon.The Diels-Alder adducts in the presence of a slight amount of acid yield the corresponding open chain esters.