103708-90-3Relevant academic research and scientific papers
Synthesis and Structures of 1-Oxa-3,5-diaza-1,3,5-hexatrienes. The 1-Oxa-3,5-diaza-1,3,5-hexatriene/2H-1,3,5-Oxadiazine Tautomerism
Buhmann, Martin,Moeller, Manfred H.,Wuerthwein, Ernst-Ulrich
, p. 957 - 968 (2007/10/02)
Reaction of N-lithio- or N-trimethylsilyl-substituted imines 1 with N-acylimidic acid derivatives 2 provides 1-oxa-3,5-diaza-1,3,5-hexatrienes 3 in fair to good yields.Depending on the substitution pattern, the acyclic compounds 3 form an equilibrium with their cyclic tautomers, e.g. 2H-1,3,5-oxadiazines 4.Aromatic substituents at C-6 favor the acyclic form 3, whereas aliphatic groups (e.g. tert-butyl) lead to the exclusive formation of the ring tautomer 4.For a typical example (3d/4d) the free enthalpy of activation for the ring/chain tautomerism was determined to be ca. 12.5 kcal/mol.Detailed spectroscopic data (1H-, 13C-NMR, IR, UV) for both tautomers are given.The X-Ray analysis of the acyclic compound 3a shows a central C=N bond with Z configuration and with s-gauche conformations of the adjacent C=O and C=N systems.According to quantum mechanical ab initio calculations (MP2/6-31G*//6-31G*) for the C3H4N2O model compounds, the ring tautomer 6 is by ca. 6 kcal/mol lower in energy than the acyclic forms 7.Within the series of open-chain tautomers 7, gauche forms ar lower in energy than s-trans conformers, indicating that amide resonance is more important for these systems than polyene delocalization. s-cis Forms were found to be transition states.The acyclic conformers 7 are rather flexible, barriers of rotation for both C-N bonds are calculated to 4-5 kcal/mol only (RHF/3-21G//3-21G).Key Words: 1-Oxa-3,5-diaza-1,3,5-hexatrienes / 2H-1,3,5-Oxadiazines / 1-Oxa-3,5-diaza-1,3,5-hexatriene - 2H-1,3,5-Oxadiazine tautomerism / Ring-chain tautomerism / Calculations, ab initio
Synthesis and Properties of Substituted 1-Alkoxy-2-azaallenium Salts
Kupfer, Rainer,Wuerthwein, Ernst-Ulrich
, p. 857 - 871 (2007/10/02)
12 novel substituted 1-alkoxy-2-azaallenium salts 1 have been prepared by reaction of the N-methyleneamides 3 with trialkyloxonium salts 4.During the alkylation reaction of the N-benzylideneamides 3m, n a formal disproportionation takes place to yield hig
