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Die Regioselektivitaet der Ringschlussreaktionen zu 1,2,3-Thiadiazolen und 1,2,3-Selenadiazolen
Zimmer, Oswald,Meier, Herbert
, p. 2938 - 2946 (2007/10/02)
Unsymmetrical hydrazones of type 2 exist in a Z/E-equilibrium from which ring closure reactions with SOCl2 or SeO(OH)2 occur.Isomeric 1,2,3-thiadiazoles 3/3' and 1,2,3-selenadiazoles 4/4', respectively, are formed.Regioselectivities are discussed concerning the examples 2a - t.For b, c, d, and o product distributions are rationalized on the basis of the Z/E-equilibrium proportions and the ratio of reactivities.Principally, methylene hydrogens are more reactive than methyl hydrogens, even when the reaction on the methyl side predominates.
