Aromatic diimides, also known as bis(dicarboximide)s, are the linchpin of a diversity of organic materials encompassing vivid pigments and dyes, thermally robust polymers, and ntype electronic materials. The electron-withdrawing nature of the cyclic imides lends itself to the creation of n-type semiconducting materials. The annulation of aromatic rings with cyclic imides tends to lead to more significant LUMO-lowering effects than HOMO-lowering effects, thus resulting in red-shifted bandgaps and absorption profiles. Aromatic diimides derived from benzene (PMDI), naphthalene (NDI), and pyrene (PDI) (Figure ) have received significant research attention because of their facile syntheses and amenability to derivatization at both the core and imide N positions. While changes in Nfunctionalization are often exploited for tuning solid-state packing behavior and solubility profiles, core modification through substitution and metal-mediated cross-coupling reactions of halogenated aromatic diimides results in fine control over energy levels and electronic structure. In recent years, researchers have developed new strategies for incorporating cyclic imides onto a growing number of aromatic scaffolds, resulting in interesting redox activity and near-IR absorptions. We recently began exploring the ortho-diimide structural isomer of the well-known pyromellitic diimide, which is known as mellophanic diimide (MDI), and have discovered that it has significant potential as a building block in the construction of compounds with properties of interest to organic materials chemists (Figure ). Core dichlorinated N,N'-dihexyl MDI (Cl2-MDI-Hex), for example, readily undergoes both SNAr and Pd-catalyzed substitutions with aromatic ortho dinucleophiles to lead to a range of highly chromophoric and electron-accepting hetero-and azaacene structures. The development of MDI as a building block is further attractive because it is derived from 1,2,3,4-tetramethylbenzene, which is a byproduct of durene synthesis and a constituent of petroleum extract that has no significant industrial use. With these observations in mind, we set out to establish generalizable synthetic methods for obtaining differently halogenated MDI derivatives. Results and Discussion. Conventionally, aromatic diimides are synthesized by condensation between the relevant aromatic cyclic dianhydride and an amine, a process which proceeds through an amide-carboxylic (amic) acid intermediate. Extending this approach to the synthesis of ortho aromatic diimides such as mellophanic diimide, however, is complicated by the possibility of incorrect cyclizations to yield 3,6-dicarboxyphthalimide byproducts. Two strategies were identified by Fang et. al for overcoming this challenge: 1) room-temperature amic acid formation followed by acetic anhydride-mediated dehydration and 2) high-temperature equilibration of the reaction mixture to reach the MDI thermodynamic product (Fig ). While both of these methods were successful for synthesizing N,N'-diaryl MDI compounds, we found that they could not be reliably extended toward either N,N'-dialkyl-or corechlorinated MDIs because of competing nucleophilic aromatic substitution reactions and significant 3,6-dicarboxyphthalimide formation. Inspired by the mellitic triimide synthesis developed by Rose et. al, we were previously able to obtain N,N'-dihexyl-4,5-dichloro-MDI (Cl2-MDI-Hex) after the 3-day solidstate dehydration of an ammonium carboxylate salt (Fig. ). In further explorations, however, we found that this solid-state method could not be consistently extrapolated to differently halogenated benzene tetracarboxylic acids, and furthermore was not successful with more sterically demanding amines. As a result of further synthetic exploration, here we report our findings that the direct solution-phase reaction between benzene-1,2,3,4tetracarboxylic acids and primary amines is a widely generalizable method for synthesizing MDI derivatives of a variety of N substitutions and core halogenations (Fig. ). Synthesis. The commercially available 1,2,3,4-tetramethylbenzene was chlorinated, 20 brominated, or iodinated following literature procedures to yield intermediates 1-X (X = Cl, Br, or I) which were then subjected to exhaustive oxidation by 10 eq. of KMnO4 in tBuOH/H2O (1/1:v/v) to provide the halogenated benzene-1,2,3,4-tetracarboxylic acids. Although many KMnO4 methylarene oxidation procedures use pyridine as a co-solvent to improve reactant solubility, we have found that the use of tBuOH co-solvent reduces the equivalents of KMnO4 required to achieve full oxidation and furthermore is less prone to exotherm during the addition of KMnO4. Complete removal of reaction solvent prior to acidification of the carboxylate intermediate is important for avoiding the formation of t-butyl ester impurities. Our largest scale oxidation (20.0 g, 98.5 mmol of 1-Cl) proceeded smoothly to provide the tetraacid 2-Cl in 85% isolated yield.