Experimental survey of the kinetics of acene Diels-Alder reactions

Second-order rate constants were gathered for solution Diels-Alder reactions of substituted and unsubstituted acenes, with the intention of ascertaining ideal diene-dienophile combinations. Particular focus was placed on the larger ring systems namely tetracene, pentacene, and rubrene. The rate constants between the acenes ranged roughly six orders of magnitude, from the slowest reacting diene, rubrene, to the fastest diene, pentacene. The utilized dienophiles covered a large range of reactivity from 2,3-dichloromaleic anhydride to tetracyanoethylene. To aid in the interpretation of acene reactivity, constants were compared to the extensive body of Diels-Alder literature with well-studied dienes such as anthracene and trans-1-methoxy-1,3-butadiene serving as points of reference. Complex reaction kinetics for the addition of MeTAD and rubrene was found: initial fast consumption generated an intermediate, followed by dramatically slower product formation. The kinetic data creates a foundation for the analysis of prior and future reactions between organic semiconductor acene materials with volatized dienophiles, a surface functionalization technique for enhancing these electronic materials. Copyright (C) 2015 John Wiley & Sons, Ltd.