Abstract
[Col 2 (PPh 3 ) n ]-zinc systems (n = 1 or 2) exhibit high catalytic activity for the homo-Diels-Alder [2 + 2 + 2] cycloadditions of norbornadiene with various alkynes including terminal and internal acetylenes and methyl prop-2-ynyl ether to give the corresponding deltacyclenes in good to excellent yields.