Aromatic ethers, acylation nucleophiles

If the anodic oxidation of N-alkylanilines is performed in the presence of nucleophiles like enol ethers, nucleophilic substitution in the of-position to nitrogen by the enol ether can be observed in low yields. The electrophilic intermediate is the N-aryl iminium ion or the N-aryl imine after loss of two electrons and one or two protons. These intermediates add to the enol ether to give acetals (up to 26%) as addition products, or the first addition step is followed by an electrophilic aromatic substitution to form tetrahydroqui-nolines (13-39%) [47]. It should be noted at this point that better results for the nucleophilic a-substitution to nitrogen can be obtained with N,N-dialkylanilines (see next subsection). Optimum results, however, are obtained with N-acylated compounds via the intermediate N-acyl iminium ions (see Ref. 8). 

The synthesis of hb-PAEKs via the A2 + B3 approach has been reported by many research groups [67, 68]. Choi et al. [69] reported a self-controlled synthesis of hb-PAEKs from diphenyl ether (or 1,4-diphenoxybenene, B2) and trimesic acid (A3) via the Friedel-Crafts reaction. Baek and coworkers developed optimized conditions for Friedel-Crafts acylation in poly(phosphoric acid)/phosphorus pent-oxide (PPA/P2O5) medium for the preparation of hb-PAEKs [70,71]. Martinez and Hay [72, 73] proposed the efficient synthesis and characterization of hb poly(aryl ether sulfone)s with a K2C03/Mg(0H)2 catalyst system for nucleophilic aromatic substitution. Kim et al. [74] reported the controlled nucleophilic aromatic... 

Tricarbonylchromium stabilized benzylic carbocations can be captured by a large variety of nucleophiles, such as alcohols, amines, thiols, nitriles, trimethylsilyl enol ethers, allylsilanes, electron-rich aromatics, dialkylzincs, and tri-alkylaluminums (eq 19). The relative stereochemistry formed during these reactions via carbocations in acyclic systems proceeds with net retention. Friedel-Crafts acylation of (styrene)chromium complexes has been explored via the benzylic cations (eq 20). Tricarbonylchromium-stabilized oxonium ions are also utilized for steroselective carbon-carbon bond forming reactions (eq 21). ... 

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