1,2‐Diaza‐1,3‐diene‐Based Multicomponent Reactions in Sequential Protocols to Synthesize Arylamino‐5‐hydrazonothiophene‐3‐carboxylates

Abstract

Two unprecedented approaches to amply functionalized 2‐arylamino‐5‐hydrazonothiophene‐3‐carboxylates were reported. The first one is a useful metal‐free sequential multicomponent synthesis of readily available β‐keto esters, isothiocyanates and in situ generated 4‐unsubstituted diazadienes. The second one is the basic treatment of 2,5‐dihydrothiophenes previously prepared by means of an analogous sequential multicomponent synthesis where 4‐substituted diazadienes were employed.

Metal‐free ring opening of 5‐amino‐1,4‐diaryl‐1H‐pyrazoles: A facile access to 2‐aryl‐3‐arylazoacrylonitriles

“…2, 149.6, 132.5, 130.6, 129.4, 129.1, 126.7, 124.9, 124.5, 117.2, 12.8 148.3, 137.1, 133.4, 132.7, 130.9, 130.2, 129.4, 129.0, 127.7, 124.5, 118.1, 117.6, 13. 4, 138.8, 132.8, 132.5, 130.7, 129.9, 129.4, 128.8, 126.5, 123.9, 123.5, 117.8, 21.5, 12.8 Reaction time: 15 min; yield: 99% (0.135 g); red color solid; R f = 0.62 in 20% EtOAc in hexane; m.p = 178 C; IR (KBr, ν cm À1 ): 3446,2201,1635,1482,1436,1372,1335,1261,1169,1128,1075,903,805; 1 H NMR (400 MHz, CDCl 3 ) δ 8.02-8.02 (m, 2H), 7.86 (s, 1H), 7.80 (d, J = 7.6 Hz, 1H), 7.73 (d, J = 8.0 Hz, 1H), 7.65 (t, J = 7.6 Hz, 1H), 7.54-7.53 (m, 3H), 2.26 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 164.0, 152. 3,133.7,133.0,132.6,131.5 (q,J = 32.6 Hz),129.7,129.4,126.6 (q, J = 4 Hz), 126.1 (q, J = 4 Hz),124.1, 123.7 (q, J = 271 Hz) 121. 4, 117.1, 12.7; 19 3427,2189,1634,1470,1457,1372,1053,1027,990,762,737,602; 1 H NMR (400 MHz, CDCl 3 ) δ 7.…”

“…Azoalkenes are essential building blocks in constructing new heterocyclic frameworks through cycloaddition, multicomponent, and tandem reactions [1–4]. For example, the bicyclo[4.1.0]tetrahydropyridazines are synthesized via a sequential [4 + 2] and [1 + 2] annulation reaction of azoalkenes and crotonate‐derived sulfur ylides [5].…”

Synthesis and Phase Behavior of a Platform of CO2-Soluble Functional Gradient Copolymers Bearing Metal-Complexing Units

“…The ratio between them changes depending on the different amines used to perform the aminolysis. This change is most probably due to the formation of enamine between butylamine and the acetoacetate group of AAEM [82,83]. Thus, for the sake of comparison, all the aminolyzed polymers reported in this work were obtained by using piperidine (secondary amine) as nucleophile.…”

Diaza-1,3-butadienes as Useful Intermediate in Heterocycles Synthesis

“…Under the acid conditions, the ketone is released by the hydrolysis of the hydrazone moiety followed by a retro-Claisen reaction to form the thiophene ring. However, basic treatment using NaOH in THF/H 2 O affords the unexpected 2-arylamino-5-hydrazono thiophene-3 carboxylates 17 in good yields [ 31 ]. In this case, the basic medium favors the hydrolysis of the ester in position 2 of 15 followed by a decarboxylation that promotes the aromatization of the ring.…”

“…Thus, amine 10 and a slight excess of β-ketoesters 11 react in solvent-free conditions at room temperature. Then, arylisothiocyanates 12 in CH 2 Cl 2 were added, generating 9 , which finally, reacts with 1,2-diaza-1,3-butadienes 19 generated from α-halohydrazones and potassium carbonate ( Scheme 3 ) [ 31 ]. DCM was used instead of MeOH to avoid their reaction with α-halohydrazones.…”