Scheme 30.
Cycloaddition of maleic anhydride to perylene bisimide [187,188,189]. Reagents and conditions: (a) for R = -CH(C9H19)2: p-chloranil, 202 °C, 12 h (at the beginning, a few milliliters of acetone were added, but the high reaction temperature indicated that it was gradually evaporating), Y = 65%; (b) for R = 4-undecyl: excess of melted p-chloranil, rfx, 2 d, Y = not reported; and (c) excess of dienophile, a small amount of acetone, 125 °C (at the beginning), and then rfx, 4 d, Y = 71% (133); Y = 77% (134); and Y = 67% (135).