Base promoted one-pot annulative coupling of 1,2,3,4tetrahydroisoquinolines (THIQs) with hypervalent iodine(III) species aryliodonio diazo compounds has been devised for the direct construction of 1,2,4-triazolo[3,4-a]isoquinoline derivatives at room temperature in open air for the first time. This approach involves [2 + 3] cascade annulation of nucleophilic THIQ with an electrophilic aryliodonio diazo compound via N−H and α-C1(sp 3 )−H difunctionalization of THIQ.

A chemoselective route to thiazolines and thiazines has been devised by heterocyclization of viable α-N-hydroxyimino-β-oxodithioesters with 2-chloroethylamine hydrochloride/3-chloropropylamine hydrochloride, which does not require metals or additives and proceeds at 0-60 °C. The overall transformation involves base mediated intramolecular cyclization of α-N-hydroxyimino-β-oxodithioesters to 4-membered oxazete-4-thione intermediates followed by coupling with chloroalkyl amines via tandem ring cleavage and CÀ N/CÀ S bonds formation enabling the construction of thiazolines/thiazines in one-pot. This strategy allows broadening the arsenal of synthetic methods to obtain N,S-heterocycles utilizing substrates prepared according to reported procedures.

A metal-free radical cascade cyclization of β-ketothioamides and alkyl/aryl nitriles has been developed for the synthesis of 1,2,4-thiadiazoles bearing a stable nitroso group at exocyclic double bond in a one-pot system. The reaction proceeds via the in situ generated ketoxime intermediate of β-ketothioamide, which further assists the formation of 1,2,4-thiadiazole through the reaction with nitrile under TBN (tert-butyl nitrite) mediation. The basic utility of this reaction is the formation of 3 new bonds (two C-N and one S-N) in one stretch under mild conditions. Moreover, this protocol features excellent functional group tolerance, operational simplicity, and easy scalability. The radical process is supported by the BHT-adduct of α-ketoxime intermediate. Noteworthy, the products possess Z-stereochemistry with regard to the exocyclic C=C double bond at the 5-position.

Herein, we report a one‐pot viable protocol to synthesize tetrasubstituted 2‐aminothiophenes engaging readily accessible α‐enolic dithioesters and abundant fumaronitrile under transition metal‐free conditions at room temperature in open air. The reaction proceeds via successive Michael‐type addition/intramolecular cyclization/isomerization cascades. The added features are benign conditions, exclusive regio‐ and chemoselectivity, excellent atom‐/step‐economy, easy purification, and tolerance of wide range of functional groups of a diverse electronic and steric nature. This protocol not only provided a robust and modular approach to various 2‐aminothiophenes in moderate to excellent yields, but also demonstrated the potential of dithioesters and fumaronitrile in the challenging intermolecular cross‐coupling reactions widening the arsenal of synthetic methods.

A facile and efficient one-pot synthesis of bench-stable quinoxaline N-oxides has been realized using α-oxoketene N,S-acetals and tert-butyl nitrite (TBN) in open air via cascade annulation. The double functionalization of N,S-acetals proceeds through an unanticipated (Csp2)-H nitrosation by NO radical (generated in situ by TBN) and subsequent intramolecular N-arylation leading to quinoxaline, which undergoes oxidation to quinoxaline N-oxides harboring three variegated substituents on their framework. Notably, two new CN bonds are formed with the same N-oxide nitrogen. This protocol features short reaction time, good functional group tolerance and mild conditions without the use of catalyst and external additive.