“…Dienophiles 1 to 6 contain as a group four different types of unsaturation-namely, a, /3-conjugated (1, 2), strained ring (3,5), cycloalkenyl (4), and acyclic terminal (6). The nine dienes are representative of seven different types-namely, cyclic (7), polyhalogenated cyclic (8,9), monosubstituted acyclic (10,11), aromatic (12), unsubstituted acyclic (13), 2,3-disubstituted acyclic (14), and 1,4-disubstituted acyclic (15). With the exception of those specific cases wherein maximum adduct recovery either was not sought or was especially difficult because of the exceptionally high boiling points of the adducts, surprisingly high yields were obtained in these reactions.…”