18667-21-5Relevant academic research and scientific papers
Process for the preparation of pyridinium intermediates
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, (2008/06/13)
A process for the preparation of halobenzoic acids, comprising the step of reacting a halonitrobenzene with a pyridinium salt to form an intermediate of the formula STR1 wherein R is selected from the group consisting of hydrogen, alkyl, aryl, alkenyl, alkynyl, --CN, --COOR' and --COR' where R' is alkyl or aryl; X is chloro or fluoro; Y is hydrogen, chloro or fluoro; and Z is chloro, bromo or iodo.
Stereoselective Cycloaddition of Pyridinium or Isoquinolinium Methylides with Olefinic Dipolarophiles and Subsequent Cycloadditions of the Cycloadducts with Nitrile Oxides
Tsuge, Otohiko,Kanemasa, Shuji,Takenaka, Shigeori
, p. 3631 - 3636 (2007/10/02)
Pyridinium or isoquinolinium methylides undergo highly stereo- and regioselective cycloadditions with olefinic dipolarophiles to form unstable tetrahydroindolizine derivatives.One of the two double bonds existing in the dihydro heteroaromatic ring of the cycloadducts reacts with nitrile oxides, in the same flask, in stereo-, regio-, and periselective fashions to lead to stable isoxazole-fused tetrahydroindolizines in good yields.
SYNTHESIS AND STRUCTURAL STUDY ON Α-SUBSTITUED-1-STYRYLPYRIDINIUM SALTS. REINVESTIGATION OF KROHNKE CONDENSATION
Alvarez-Builla, J.,Novella, J. L.,Galvez, E.,Smith, P.,Florencio, F.,et al.
, p. 699 - 708 (2007/10/02)
Kroehnke condensation of several cycloimmonium salts with p-dimethylaminobenzaldehyde has been studied.X-Ray diffraction, IR and Raman spectra, 1H- and 13C-NMR and UV spectra of the products are discussed, being compared, when necessary, with the starting pyridinium salts.All compounds showed the Z configuration, corresponding to the more stable structure, except one, in which steric factors were predominant.
Fragmentative Ring Contractions of the 1 : 2-Adduct of Pyridine and Dimethyl Acetylenedicarboxylate
Kaupp, Gerd,Hunkler, Dieter,Zimmermann, Inge
, p. 2467 - 2477 (2007/10/02)
The structure 1a is secured for the 1 : 2-adduct of pyridine and dimethyl acetylenedicarboxylate.Its UV/VIS and 1H NMR spectra are temperature-dependent.Dichromate oxidation of 1a produces not only the indolizine 3, but also the quinolizinone 4.The indolizines 8, 3, 9, and 10 are formed in the ratio 10 : 5 : 5 : 1 upon thermolysis of 1a at 220 deg C, whereas 4 is stable under these conditions.The complex ring contractions with fragmentations and in part rearrangements are classified and interpreted mechanistically (high energy valence tautomers; cyclpropane-, ylide-, zwitterion/diradical-intermediates).The gaseous and liquid further products of the thermolysis are compatible with the intermediacy of carbene and radical fragments.Analytical and spectroscopic data (UV, fluorescence, IR, 13C NMR, MS) as well as independent syntheses (3, 10) and the synthesis of the reference compound 12 secure the constitutions of the compounds.
Preparation of Tetrahydroindolizines from Pyridinuim and Isoquinolinium Ylides
Katritzky, Alan R.,Grzeskowiak, Nicholas E.,Alvarez-Builla, Julio
, p. 1180 - 1185 (2007/10/02)
Carbonyl- and nitrile-stabilised pyridinium and cyclic azonium methylides condense with chalcones to form tetrahydroindolizines and analogous fused pyrrolidines.The stereochemistry is illuminated by 13C and 1H n.m.r. spectroscopy.Several incorrect literature structures are rectified.
