Enaminonitriles in Heterocyclic Synthesis: A Route to 1,3-Diaryl-4-aminopyrazole Derivatives

Abstract

Benzylcyanide and 4-nitrobenzylcyanide condensed with triethyl orthoformate and piperidine or morpholine to yield 2-aryl-2-piperidinyl or 2-morpholinylacrylonitriles. These coupled with aromatic diazonium salts to yield the 2-arylhydrazno-2-arylethane nitriles in good yields. The latter were converted into 4-aminopyrazoles in good yields using the Thorpe-Ziegler cyclization.

Pyrazolopyrimidines in ‘all-natural’ products for erectile dysfunction treatment: the unreliable quality of dietary supplements

“…More likely, they are by-products of the synthesis of a sildenafil analogue. For the synthesis of sildenafil and its analogues many different routes are described (Kim et al 2001(Kim et al , 2013Ley et al 2002;Yu et al 2003;Li et al 2004;Xia et al 2005;Abdel-Jalil, Khanfar, Abu-Safieh et al 2005;Medrasi et al 2013). Based on published procedures a hypothetical reaction scheme towards pyrazolopyrimidines bearing an acetyl bridge, explaining the existence of the compounds found in the present study and earlier by others, is shown in Figure 8.…”

Enamines in Heterocyclic Synthesis: Route to Aminopyrazolopyrimidines and Arylpyrazolopyrimidiens Derivatives

“…A key advantage of modern, scientific microwave apparatus is their ability to control reaction conditions precisely, by monitoring temperature/pressure, reaction times and ease of isolation of the products after easy work-up [11,12]. In conjunction to our interest in the chemistry of enaminonitriles [13][14][15][16][17], we report here results of our work aimed at developing efficient environmentally friendly syntheses for several targeted pyrazolopyrimidines utilizing enamines 2,4 and 6a,b as starting materials. In our chemical reactivity studies described here, we principally employed the intermediate 6b due to their easy preparation and good yield of reactions.…”