Reatividade de 2H-azirinas com compostos do grupo do niquel, em solventes aproticos e proticos

AUTOR(ES)
DATA DE PUBLICAÇÃO

1981

RESUMO

The 3-phenyl-2H-azirines 6j-m and the 2-phenyl-3-styryl-2H-azirine, 16z, alI with functional groups bonded to the three-membered ring, were synthesized by the thermolysis of the corresponding vinylazides. We also synthesized the 3,3 -p -phenylene-bis(2H-azirine), 36, which is not described in the literature. A new method to synthesize pyrroles from 2H-azirines and activated ketones in the presence af nickel(II) or palladium (II) compounds was developed. We obtained the pyrroles 171a-t at room temperature in exccllent yields. Based on the experimental data we have proposed a mechanism for this reaction. The trans-dichlorobis (2H-azirine) palladium (II) complexes 243o-v were prepared. The complex 243s is stable as a solid but suffers opening of the 2H-azirine ring at the carbon-nitrogen single bond in chloroform or benzene solution, at room temperature. In three hours it is completely converted into the 1,5-diazapentadienyl complex 249. The complexes 243o and 243t, which are stable in the solid state at room temperature, also open at the carbon-nitrogen single bond while being stirred in an aprotic solvent at room temperature for several days. The complexes 251 and 252, respectively, are formed. These are the first examples where 2H-azirines, coordenated to a transition metal compound, suffer ring-opening and the organic ligand stays attached to the metal. The formation of 2,5-diphenylpyrazine, 188a, from 3-phenyl-2H-azirine, 6a, was studied in methanol and methanol-d4 dihydropyrazines 189a and 191a and captured the third isomer 280 with dimethyl acetylenedicarboxylate in the presence of a cobalt (II) compound. The diazabicyclooctadiene 281 is formed in this reaction. We also studied the ring-opening of the same azirine, complexed to palladium dichloride, in methanol and methanol-d4. We isolated the diamine complex 283, whose X-ray structure was deterrmined. On reaction of this complex with triphenylphosphine we obtained 1,1-dimethoxy-1-phenyl-2-aminoethane, 277. In the same way we obtained the first polyrmeric pyrazine 284 and the polymeric diamine complex 285 from 3,3 -p-phenylene-bis(2H -azirine), 36. We also studied the ring-opening of the 2H-azirine 6g in methanol, as well as its palladium dichloride complex 243g. The diamine complex 286, as well as the 1,1,3,3-tetramethoxy-2 -aminopropane, 287, was isolated.

ASSUNTO(S)

reatividade (quimica) solventes compostos de niquel - reatividade (quimica)

ACESSO AO ARTIGO

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