4491-43-4Relevant academic research and scientific papers
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.
