Synthesis of Aminopyridazines from Aminocyclopropenylium Salts and Diazomethyl Compounds [1]

Abstract

Abstract. Amino-substituted cyclopropenylium salts (11a,b) react with diazornethyl compounds (I2a·i) in dichloromethane or acetonitrile in the presence of a base (ethyldiisopropylarnine, 1,S-diazabicyclo[ 4.3.0] non-5-ene) to form 4-aminopyridazines (13a-i) specifically. The reaction is interpreted in terms of an initial electrophilic diazoaIkane substitution to give diazornethylcyclopropenes (11 + 12~14) which undergo a [1.5) -cyclisation to form the betaines 16 which, in tum, isomerise with opening of the bridging bond to give the arninopyridazines 13. In a similar manner, the tris[amino j cyclopropenyliurn salts 8a,b and lOa-c are converted to the 3,4,5-tris[ amino j. pyridazines (21a-k) by treatment with diazomethyl compounds (12a, c-f).

Cyclopropenylium Cations, Cyclopropenones, and HeteroanaloguesRecent Advances

“…The aminocyclopropenylium cation 195 reacted with various diazomethane derivatives in dichloromethane or in acetonitrile in the presence of ethyldiisopropylamine or 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) at room temperature to give selectively 4-aminopyridazine derivatives 197 (eq 112) . The reaction was interpreted in terms of an initial electrophilic substitution of the diazoalkane, to give diazomethylcyclopropenes, which undergo [1.5] cyclization to form zwitterion 196 and valence bond isomerization to the pyridazine derivatives.…”

Cycloaddition Reactions of Phosphorylated 1,2‐Diaza‐1,3‐butadienes with Olefins: Regioselective Synthesis of Pyridazine Derivatives

“…Pyridazines constitute an important class of compounds with interest in organic and medicinal chemistry. [17,18] However, only one example of the preparation of pyridazines containing phosphorus substituents has been described [19] by reaction of diazoalkyl-1,3-dipoles and cyclopropenyl derivatives. Therefore, as far as we know, this strategy represents the first synthesis of tetrahydropyridazines containing a phosphinyl or a phosphonyl group as substituent, as well as the first example of an aza-DielsAlder reaction of the phosphorylated 1,2-diaza-1,3-butadienes 2.…”

Diaminopyridazine aus diaminocyclopropenyliumsalzen und (diazomethyl)‐ verbindungen

“…hervorgehoben sei, daB in dessen 'H-NMR-Spektrumebenso wie auch bei 14beine Rotationsbehinderung um die Dreiring-KohlenstoffIAmin-Stickstoff-Bindung a n den breiten, aufgespaltenen Signalen fur die N-Methylwasserstoffe zu erkennen ist [lo]. So fehlt bei 16a-e eine Absorption im Bereich von 6 = 3.44-3.49, die fur einen C-3 gebundenen N-Methylanilinorest typisch ist [9]. Die Phosphorylgruppe a n C-6 von 16a-e laBt sich zum einen am Auftreten der charakteristischen PO-Absorption (1161-1268 cm-') im IR-Spektrum und zum anderen durch die Absorption der a n den Phosphor gebundenen Reste im 'H-NMR-Spektrum erkennen (s. Tabelle 1).…”