108153-98-6Relevant articles and documents
Syntheses with cyclobutadienes 11 (1). Isomerisation reactions in the dewar pyridine/pyridine system
Fink, Juergen,Regitz, Manfred
, p. 239 - 244 (2007/10/02)
Cyclobutadiene 9 undergoes smooth cycloaddition reactions with the activated nitriles 6a-c at 20 deg C to give the Dewar pyridines 10a-c.In the case of 6d, the reaction with 9 leads directly to the formation of the pyridine 11d.The Dewar pyridines 10a and b can be thermally isomerised to pyridines of the same type (11a, b).On irradiation, compounds 10a and b undergo a rearrangement to give the constitutionally isomeric Dewar pyridines 12a and b.Compounds of the type 12 are also obtained by irradiation of pyridines (11a, b, d -> 12a, b, d).The reverse reaction (12 -> 11) can be realiosed thermally.Nitriles containing active methylene groups (15a, b) do not undergo cycloaddition reactions with 9; instead 1,4-addition at the terminals of the cyclic 1,3-diene system occurs to form the products 16a and b.
