No abstract

We describe the synthesis of characterizable diazaheptacene derivatives. Diazaheptacenes need four silylethynyl protecting groups to be isolable. TIPS-ethynyl groups are not bulky enough to allow stabilization. Four Si(sec-Bu)3-ethynyl groups symmetrically attached to the acene core sufficiently protect the formed diazaheptacene from dimerization through Diels-Alder reaction. It was characterized by NMR and UV-vis spectroscopies and cyclic voltammetry.

Organic electronics on demand? The palladium‐catalyzed coupling of aromatic ortho‐diamines with substituted dichloroquinoxalines furnishes N,N‐dihydrotetraazaacenes, which were oxidized by MnO2 into the corresponding tetraazapentacenes (see structures; N blue, Cl green, Si yellow). The modular synthesis of these acenes allows the introduction of any substituent by choice of the proper quinoxaline derivative.

Accessible azaacenes: Pd‐catalyzed coupling reactions between aromatic diamines and unactivated aromatic dibromides furnish N,N′‐dihydrodiazapentacenes, ‐hexacenes, and ‐heptacenes (see scheme; TIPS=triisopropylsilyl). Oxidation of these products led to diazapentacenes and a diazahexacene. The existence of a diazaheptacene intermediate was proven by solving the single‐crystal structure of its (4+4) dimerization product.

Asymmetric allylic substitutions have been studied with great success over the last few years.[1] With monosubstituted allylic derivatives as substrates (Scheme 1), iridium complexes of electron-poor ligands seem to be the catalysts of choice for asymmetric allylic alkylations, [2] aminations, [3] and etherifications.[4] Using ligands L1 and L2, [5] regioselectivities of > 95:5 in favor of the branched products and enantioselectivities of up to 99 % ee have been obtained.The method appears particularly suited for the synthesis of N-heterocycles. Examples are 2-vinyl-azacycloalkanes, Scheme 1. Iridium-catalyzed allylic substitutions.

Novel phenazinothiadiazoles were prepared by condensation of ortho-quinones and an alkynylated 5,6-diamino-2,1,3-4 benzothiadiazole and evaluated as transport materials in thin film transistors.

A series of functionalized diaza- and tetraazatetracenes was synthesized, either by condensation of an aromatic diamine with an ortho-quinone/diethyloxalate followed by chlorination with POCl(3) to give diazatetracenes or by palladium-catalyzed coupling of a phenylenediamine with various 2,3-dichloroquinoxalines to give tetraazatetracenes (after oxidation with MnO(2)). Representative examples included halogenated and nitrated derivatives. The optical properties of these azatetracenes were discussed with respect to their molecular structures and substitution patterns. The diazatetracenes and tetraazatetracenes formed two different groups that had significantly different electronic structures and properties. Furthermore, 1,2,3,4-tetrafluoro-6,11-bis((triisopropylsilyl)ethynyl)benzo[b]phenazine was synthesized, which is the first reported fluorinated diazatetracene. Single-crystal X-ray analysis of this compound is reported.

A cyclocondensation of TIPS-ethynyl-substituted diaminoarenes with in situ obtained 4,5-dibromocyclohexa-3,5-diene-1,2-dione has led to the synthesis of tetrabromotetraazapentacene (BrTAP). BrTAP is easily reduced to its air-stable radical anion and electron mobilities >0.56 cm V s can be achieved in thin-film transistors.