Recent Advances in Pyridazine Chemistry

Face Selectivity of the Diels‐Alder Additions of Exocyclic Dienes Grafted onto 7‐Oxabicyclo[2.2.1]heptanes

“…Because of the triazolidinedione annelation, the conformation of the cyclohexene of 36 may deviate significantly from that of a half-chair [35], thus explaining the somewhat different 'H-NMR. characteristics observed for this compound when compared with those of 29.30, and 32-34 ( Table 3).…”

Six‐Membered Heterocycles: 1,2‐, 1,3‐, and 1,4‐Diazines and Related Systems

“…A versatile solid-phase approach for the synthesis of a series of pyrimidinone derivatives has been described (Scheme 19.72) [107]. In the key step, a polymer-bound thiouronium salt is condensed with different b-ketoesters by adding an excess of Ca(OH) 2 The use of iminophosphoranes has been emerging as a valuable tool for the construction of nitrogen-containing heterocycles [108]. The aza-Wittig reaction of iminophosphorane 86 with acyclic a,b-unsaturated aldehydes has been reported by Rossi and coworkers as a means to produce 1,6(1,4)-dihydropyrimidines 88 through electrocyclic ring closure of 1,3-diaza-1,3,5-triene intermediate 87 (Scheme 19.73) [109].…”

“…The three diazine isomers are pyridazine (1,2-diazine) [1][2][3] (1), pyrimidine (1,3-diazine) [4] (2), and pyrazine (1,4-diazine) [5] (3). They are stable, colorless compounds that are soluble in water.…”

13C nuclear magnetic resonance spectra of 3,6-disubstituted pyridazines

“…in Table 2; for reviews see refs. [22][23][24]. The proton nmr data obtained using the same solutions as employed for recording the 13C nmr spectra are summarized in Table 2.…”