Metal-catalyzed synthesis of five-membered ring N-heterocycles. A recent update

Intermolecular Aminocarbonylation of Alkenes using Concerted Cycloadditions of Iminoisocyanates

“…The azomethine imines provided by aminocarbonylation reactions of enol ethers ( 3 ) are closely related to pyrazolones ( 15 ): aromatic heterocycles with applications in medicinal chemistry and agrochemistry . Pyrazolones are typically synthesized from hydrazines and unsaturated carbonyl compounds or through variations relying on the same retrosynthetic disconnection . In contrast, we envisioned access to pyrazolones from our azomethine imines by a one-pot reduction/aromatization sequence to provide a new approach starting from simple alkenes.…”

Medicinal Attributes of Thienopyrimidine Based Scaffold Targeting Tyrosine Kinases and Their Potential Anticancer Activities

“…Tsantrizos et al achieved the synthesis of the final compound (A) by refluxing substituted 5-amino-4cyanothiophene derivatives with formic acid in presence of sulfuric acid (route c) [32]. Varvounis et al reported the synthesis of the final compound (A) by different routes; from carboxamide by heating in formic acid or triethylorthoformate (route g) or from 4-amino 6-chloropyrimidine-5-carbaldehydes in methanol containing methyl 2-mercaptoacetate and triethylamine (route f) and by heating 4-chloropyrimidine-5-carbonitriles and alkyl 2-mercaptoacetate in ethanol containing base (route e) [33]. Aminothiophenes react with 5,5 0 -dimethyl N-cyanoiminocarbodithioate to give isothioureas followed by cyclization in the presence of amine if its ester substituent or by heating with a base if its amino substituted (route h) to yield A [33,34].…”

“…Varvounis et al reported the synthesis of the final compound (A) by different routes; from carboxamide by heating in formic acid or triethylorthoformate (route g) or from 4-amino 6-chloropyrimidine-5-carbaldehydes in methanol containing methyl 2-mercaptoacetate and triethylamine (route f) and by heating 4-chloropyrimidine-5-carbonitriles and alkyl 2-mercaptoacetate in ethanol containing base (route e) [33]. Aminothiophenes react with 5,5 0 -dimethyl N-cyanoiminocarbodithioate to give isothioureas followed by cyclization in the presence of amine if its ester substituent or by heating with a base if its amino substituted (route h) to yield A [33,34]. Thienylthioureas (route i) are prepared by reactions of vic-amino-(ethoxycarbonyl)-thiophenes with isothiocyanates followed by pyrimidine ring closure upon treatment with an ethanoholic solution of HCl or ethanolic alkali followed by acidification of the mixture with hydrochloric acid [35][36][37][38].…”

Regiocontrolled Coupling of Alkynes and Dipolar Reagents: Iron-Mediated [3 + 2] Cycloadditions Revisited

“…Although classical strategies for the preparation of these compounds often suffice, these approaches sometimes result in the formation of regioisomeric mixtures. Thus, the development of regioselective routes to substituted five-membered heterocycles has received particular attention . Generally, the regiochemistry can be controlled by utilizing prefunctionalized substrates, , by multicomponent processes, or through various transition-metal-catalyzed reactions .…”