Diaminopyridazine aus diaminocyclopropenyliumsalzen und (diazomethyl)‐ verbindungen

Abstract

Diaminocyclopropenyliumsalze (14a,b) reagieren in Dichloromethan mit den phosphorylierten Diazomethanen 15a‐e in Gegenwart von Ethyl‐diisopropylamin bzw. 1,5‐Diazabicyclo[4.3.0]non‐5‐en spezifisch zu den 4,5‐Diaminopyridazinen 16a‐f. Aus dem Salz 14c und den Diazomethylverbindungen 15a,c,d sowie f‐k in Dichlormethan im Beisein der bicyclischen Base bilden sich dagegen die 3,4‐Diaminopyridazine 17a‐i. In mechanistischer Hinsicht ist die Bildung intermediär auftretender (Diazomethyl)cyclopropene (14a,b + 15 → 18) bzw. (14c + 15 → 19) im Sinne der elektrophilen Diazoalkansubstitution zu interpretieren; weder 18, noch 19 lassen sich isolieren, sondern gehen eine rasche [1,5]‐Cyclisierung zu den Betainen 20 bzw. 21 ein, die abschließend durch Öffnung der Brückenbindung zu den Pyridazinen 16 bzw. 17 isomerisieren.

Synthesis of Phosphorus(V)-Substituted Six-Membered N-Heterocycles: Recent Progress and Challenges

“…Regitz and co-workers [ 104 , 105 , 106 , 107 ] reported the only method for synthesis of POR 2 -containing pyridazines, the general character of which was demonstrated in relation to a representative series of compounds. The authors showed that (diazomethyl)cyclopropenes 89 , derived from cyclopropenylium salts 87 and phosphorus-containing diazomethanes 88 , undergo intramolecular isomerization to 3-P(O)R 2 -substituted pyridazines 90 ( Scheme 22 ).…”

“…The authors showed that (diazomethyl)cyclopropenes 89 , derived from cyclopropenylium salts 87 and phosphorus-containing diazomethanes 88 , undergo intramolecular isomerization to 3-P(O)R 2 -substituted pyridazines 90 ( Scheme 22 ). When using secondary amino-substituted cyclopropenylium salts as substrates, the reaction can be performed in a one-pot fashion [ 107 ]. The method tolerates substrates containing phosphine oxide moieties and can be used to synthesize POR 2 -containg 4,5-diamino-substituted pyridazines in 16–68% yields.…”

A Novel Synthesis of Ferrocenylpyridazines

“…[7] (3) Coupling of α,β-unsaturated 1,4-diketones with hydrazine. [8] (4) Intramolecular transformation of cyclopropenyldiazomethanes [9] (Scheme 1). Aromatic ferrocenyl-substituted pyridazines have not hitherto been studied and their synthesis has not been documented.…”