The Reaction of Acylium Salts with Carbodiimides

Abstract

Acylium salts 10 react with aliphatic carbodiimides 1 in the molecular ratio 1 : 3 to give the s-triazinium salts 13a -v. In boiling methanoVdichloromethane compounds 13 loose the alkyl substituents in 1,3-position affording the triazinium salts 15. At higher temperatures solvolysis of 13 results in loss of the substituents in 2,5-position leading to 16, while with base at room temperature only the carboxamido substituent on C-2 is split off leading to triazines 18 or 19, which are transformed into 16 by treatment with dilute hydrochloric acid. The mechanisms of these transformations are discussed. Preparations of the oxadiazinium salts 6a -c are described. Die Reaktion von Acyliumsalzen mit CarbodiimidenAcyliumsalze 10 reagieren mit aliphatischen Carbodiimiden 1 im molekularen Verhaltnis 1 : 3 zu den s-Triaziniumsalzen 13a -v . Diese Verbindungen verlieren in siedendem MethanoVDichlormethan die Alkylsubstituenten in 1,3-Stellung, wobei sich die Triaziniumsalze 15 bilden. Solvolysiert man bei hoheren Temperaturen, so erhalt man unter Verlust der Substituenten in 2,5-Stellung das Triaziniumsalz 16. Unter basischen Bedingungen wird bei Raumtemperatur nur die Amidogruppe an C-2 abgespalten. Man isoliert die Triazine 18 bzw. 19, die mit verd. Salzsaure in 16 iibergefuhrt werden. Die Mechanismen dieser Reaktionen werden diskutiert. Es werden Synthesen der Oxadiaziniumsalze 6a -c angegeben.The reaction of aliphatic carbodiimides 1 with acyl chlorides 2 to yield N-acyl chloroformamidines 3 has first been described by Srachell) and Hartke2-4). This reaction has found applications for the desulfuration of thioamides, and for the preparation of certain heterocycles5,6).::To our knowledge, reactions of carbodiimides with acylium salts 10 have not been studied till now.Related with carbodiimides are disubstituted cyanamides, 4, which are known to form chloroformamidines 5 with acyl chlorides but oxadiazinium salts 6 with acylium salts'). For the latter reaction three examples, 6 a -c, are described in the experimental part.Recently, we studied the reaction of carbodiimides and cyanamides with the heterobutatrieniurn salts 78). With two equivalents of carbodiimide the triazinium salts 8 were obtained while cyanamides gave oxadiazinium salts, 9. Obviously, compounds 7 behave as acylium salts (7') in these reactions.