Arbeiten über Phosphorsäure‐ und Thiophosphorsäureester mit einem heterocyclischen Substituenten. 8. Mitteilung. Das Stäubli‐Verfahren, eine Eintopf‐Kondensation von Thiophosphorverbindungen (, XO,S), Aldehyden und Heterocyclen (mit saurer NH‐Gruppe)

Abstract

AbstractThe condensation reaction of thiophosphoric compounds 1, aldehydes and heterocycles 3 with an acidic NH‐group in strong mineral acid of specific concentration to asymmetrical compounds 4, called Stäubli procedure, differs from the Mannich‐type reaction catalyzed by weak or dilute acid (aminoalkylation of Hellmann & Opitz) and from the Tscherniac‐Einhorn‐type condensation in concentrated sulfuric acid (amidomethylation of Hellmann). Its main feature is the acidity of the two condensation participants 1 and 3; therefore an attuned concentration of mineral acid is required to activate them each to its individual optimum extent. Their pK difference, however, is sufficient to differentiate their nucleophility and reactivity and to prevent a simultaneous reaction of both of them with the aldehyde provocating side reactions to symmetrical by‐products such as 13, 14 and 15.