Search results for "ring closure"
showing 2 items of 2 documents
Benzoxetes and Benzothietes ¾ Heterocyclic Analogues of Benzocyclobutene
2012
Benzo-condensed four-ring heterocycles, such as benzoxetes 1 and benzothietes 3 represent multi-purpose starting compounds for the preparation of various higher heterocyclic ring systems. The thermal or photochemical valence isomerizations between the benzenoid forms 1,3 and the higher reactive o-quinoid structures 2,4 provide the basis for the synthetic applications. On the other hand, this valence isomerization impedes in particular the generation and storage of 1 because the thermal equilibrium 1 ⇆ 2 is completely on the side of 2. Thus, the number of erroneous or questionable benzoxete structures published to date is surprisingly high. On the contrary, the thermal equilibrium 3 ⇆ 4 is o…
Synthetic and theoretical studies of novel ring closure and ring opening reactions
2006
Ring closure and ring opening reactions are in many cases useful synthetic procedures in organic chemistry. They allow the preparation of complex molecules with high stereoselectivity and good yields. Mechanistic and theoretical studies have been carried out on the transformation of 2-aminopyrimidines into imidazo[1,2-c]pyrimidines and guanidines, respectively, through ring closure and ring opening reactions, as well as the transamidation reactions through the ring closure and ring opening of guanidine derivatives, which constitute novel synthetic methods. Sepulveda Arques, Jose, Jose.Sepulveda@uv.es