109746-12-5Relevant academic research and scientific papers
Azo Bridges from Azines, VII. - Diels-Alder Reactions with Inverse Electron Demand between Isopyrazoles and Cycloalkenes or Cycloalkadienes. - A Comparison of Acid Catalysis and Acceleration by Pressure
Beck, Karin,Huenig, Siegfried,Klaerner, Frank-Gerrit,Kraft, Petra,Artschwager-Perl, Uwe
, p. 2041 - 2052 (2007/10/02)
The acid-catalysed reaction of the isopyrazoles 1 and 2 with the cycloalkenes 3 - 8, norbornene (9), 1,4-cyclohexadiene (18), 1,5-cyclooctadiene (9), norbornadiene (20), and benzonorbornadiene (21) yields the expected azo-bridged ycyloadducts 10 - 17 nad 22 - 27.From 19 are also obtained the bisadducts 24a and 24b.At higher pressure (7 kbar) the non-acid -catalysed reaction of 2 and the previously mentioned olefines produces the respective cycloadducts usually in higher yields.In the case of 20 the additional bisadducts exo,exo-26b and endo,exo-26b are formed.Reaction rates for the (pressure-controlled) cycloadditions correlate with the reaction enthalpies of the cycloaddition between cycloalkenes and 1,3-cyclopentadiene.The exo/endo ratio of cycloadducts 25b, formed from 2 and 20 proves to be independent of temperature and pressure.
