Acylwanderungen am 3(5)-Amino-pyrazol

Abstract

Acyl Migrations on 3(5)‐Amino‐pyrazole 3(5)‐Amino‐pyrazole 1 form 3 isomeric monoacylation products, 4 diacylation products and 3 triacylation products by reaction with electrophiles like cyanates, isocyanates or carboxylic and chlorides, respectively. Acyl migrations are observed depending on the reaction temperature and the structure of the acyl residue. The structures of the acyl derivatives of 3(5)‐amino‐pyrazole were characterized by nmr‐spectroscopy.

Anion-tuning of supramolecular gel properties

“…7,48,[53][54][55] The reaction of isocyanates with 3-amino-5-methylpyrazole resulted in the formation of carboxamides, compounds 3.1 and 3.2, for example. 7,47,48 This problem was circumvented by BOC-protection of the pyrazole ring allowing for the urea functionalisation of the amine group to yield the desired urea functionalised pyrazole compounds. The propensity of the thiourea and urea groups to form an intra-molecular hydrogen bond to the pyrazole moiety, and therefore, be in an anti conformation was revealed in the determination of the crystal structures of these compounds.…”

“…7,47,49 However, as shown by Graubaum and others, temperature plays an important role in determining which of the three possible products is obtained. 47,50 Indeed even heating the products can lead to the conversion from one isomer to another, with the urea often being the most stable product. isothiocyanates reported in the literature all appear to produce a thiourea except in one case.…”

“…These products involve either reaction at the primary amino group to form a urea, or the reaction on either of the ring nitrogen positions to give a carboxamide (or carboxylic acid amide) (Scheme 3.1). 7,47,48 The large majority of the literature on this type of reaction between an amino-pyrazole and an isocyanate suggests that the carboxamide derivatives are the most common products. 7,47,49 However, as shown by Graubaum and others, temperature plays an important role in determining which of the three possible products is obtained.…”

“…7,47,48 The large majority of the literature on this type of reaction between an amino-pyrazole and an isocyanate suggests that the carboxamide derivatives are the most common products. 7,47,49 However, as shown by Graubaum and others, temperature plays an important role in determining which of the three possible products is obtained. 47,50 Indeed even heating the products can lead to the conversion from one isomer to another, with the urea often being the most stable product.…”

Cyanoacetophenone as a Synthon for 1,4,5-Substituted Pyrazoles

“…ethoxymethylene-malononitrile [1±4] or 2-cyano-3-dimethylaminopropenal [5]. In some cases, also rearrangements of substituents have been observed [6]. In this paper we report on a two step procedure for the synthesis of substituted pyrazoles from easily accessible starting materials.…”