A Practical Regioselective Synthesis of ω-Functionalized, Long-Chain 2,3-Dialkylindoles.-In connection with a research on antithrombotic drugs large-scale laboratory preparations are needed for (I) and (II) starting from inexpensive materials. Several routes, described in the literature, are compared. The method of choice, being versatile and of general applicability for indoles of this type, is shown for the example of ( II). The procedure can be scaled up if iPr2O is used instead of Et2O in conversions of type (V) → (VII) and gives (I) in an amount sufficient for its pharmacological and toxilogical evaluation. -(ARCARI, M.; AVETA, R.; BRANDT, A.; CEC-CHETELLI, L.; CORSI, G. B.; DI RELLA, M.; Gazz. Chim. Ital. 121 (1991) 11, 499-504; Lab. Ric. Ist.
The kinetics of morpholino demethoxylation of 4-methoxy-1 -methyl-2,6-diphenylpyridinium (1) and 4-methoxy-2,6-diphenylpyrylium (2) ions were studied in methanol, in the presence of morpholine/morpholinium buffers, at 25 °C. Both reactions display general base catalysis and can be assumed to proceed through tetrahedral intermediates. By steady-state treatment the rate constant for the adduct formation and the several rate ratios in the base catalysis scheme were evaluated. Attack of the nucleophile to pyrylium occurs 3 x 106 times as fast as that to pyridinium. The detailed mechanism of base catalysis seems to differ in the two reactions. The reaction of cation 1 appears to involve a rate-limiting proton transfer, as generally observed in nucleophilic aromatic substitutions of activated benzene derivatives with amines in protic solvents. In contrast, the more reactive cation 2 seems to prefer the less common specific base-general acid mechanism.
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