Synthesis of 5-vinyl-2-norbornene through Diels-Alder reaction of cyclopentadiene with 1,3-butadiene in supercritical carbon dioxide

The Diels-Alder reactions of cyclopentadiene with 1,3-butadiene proceeded smoothly in supercritical carbon dioxide in the absence of any polymerization inhibitor to produce the 5-vinyl-2-norbornene in satisfactory yield (25% yield) with high selectivity (52% selectivity).