Syntheses Using Pyridinium Salts (IV)

Abstract

Cleavage of N-phenylpyridinium or N-vinylpyridinium salts with secondary aliphatic amines leads to aromatic amino compounds or enamines which are often unobtainable by other routes. The other fragment, glutacondialdehyde or its rnonoanil, gives azulenes, as shown by Ziegler and Hafner, as well as Konig; these compounds can also be prepared from alkylpyridinium salts with cyclopentadienylsodium (Hafner). Syntheses of labile aldehydes which are otherwise dijjjcult to obtain and of a-ketocarboxylic acids, starting from pqiridinium salts and proceeding via nitrones or a-cyanoanils, are illustrated by many wcw examples. Benzimidazoles, benzothiazoles, and amidines are accessible from pyridinium salts via nitrones or a-cyanoanils; cyanoanils can be transformed into guinoxalines (including xanthopterine), perimidines, etc. Furthermore, nitrosonaphthols and nitrosonaphthylamines react with pyridinium salts containing an active iizethylene group on the nitrogq leading to new ring syslems. Further syn fhetic possihilities arise from nucleophilic &isplacements of the pyridine in pyriditiium salts by SN2 reactions. Combination of the route via nitrones with the methods of Arndt-Eistert, Ortoleva-King, or with chloromethylation constitutes a significant enlargement of its range of'application. The forniation of a-cyanoanils from diazoketones permits synthesis of a-keto-0-umino acids from a-amino acids, or of phenylglyoxylic acids from benzoic acids by chain extension.

Synthesis, Topoisomerase I and II Inhibitory Activity, Cytotoxicity, and Structure-activity Relationship Study of Rigid Analogues of 2,4,6-Trisubstituted Pyridine Containing 5,6-Dihydrobenzo[h]quinoline Moiety

“…Four pyridinium iodide salts (2a-d) were prepared in 76.8 to 99.2% yield by refluxing four different aryl acetyls (1a-d) with iodine in pyridine. Finally, on the basis of modified Kröhnke synthesis method, 12,13 twentyfour rigid analogues of 2,4,6-trisubstituted pyridine containing 5,6-dihydrobenzo[h]quinoline moiety (6-29) were synthesized by treating six propenone intermediates (4a-f) with four pyridinium iodide salts (2a-d) in 28.8 to 72.0% yield. The effect of the prepared compounds on human DNA topo I was evaluated by the topo I relaxation assays.…”

“…Since all the compounds prepared contain aromatic ring, they were visualized and detected on TLC plates with UV light (short wave, long wave or both). NMR spectra were recorded on a Bruker AMX 250 (250 MHz, FT) for 1 H NMR and 62.5 MHz for 13 C NMR, and chemical shifts were calibrated to TMS (tetramethylsilane). Chemical shifts (δ) were recorded in ppm and coupling constants (J) in hertz (Hz).…”

Modified 2,4-diaryl-5H-indeno[1,2-b]pyridines with hydroxyl and chlorine moiety: Synthesis, anticancer activity, and structure–activity relationship study

“…The conversion of supercoiled plasmid DNA to relaxed DNA by topo I and II was examined in the presence of prepared compounds (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18).…”

“…In the second step, four pyridinium iodide salts V (R 2 =a-d, f) were synthesized by refluxing acetophenones IV (R 2 =a-d, f) with iodine in pyridine. Finally, using modified Kröhnke synthesis [18,19], indanone intermediates III (R 1 =a-e) and pyridinium iodide salts V (R 2 =a-d, f) were reacted in the presence of ammonium acetate in methanol or acetic acid to give final compounds 7-18 in the yields of 24.9-58.2%. Structures, yields (%), and HPLC purities (%) of the prepared compounds are depicted in Figure 3 and Table 1.…”

“…We systematically designed eighteen compounds (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) in six different series introducing hydroxyl and chlorine groups at phenyl, thienyl or furyl ring of 2,4-diaryl-5H-indeno [1,2-b]pyridines (Fig. 2).…”