Jay Bahadur Singh

Ligand-free palladium-catalyzed facile construction of tetra cyclic dibenzo[b,h][1,6]naphthyridine derivatives: domino sequence of intramolecular C–H bond arylation and oxidation reactions

A ligand-free Pd-catalyzed approach has been developed for the synthesis of dibenzo-fused naphthyridines. The reaction involves a one-pot domino sequence of reactions involving C–H functionalisation and oxidation. The reaction was applicable to a wide range of substrates, giving the required product. Further fluorescence studies were performed where the Stokes shift was found to be dependent on the polarity of the solvent.

TBAB-catalyzed cascade reactions: facile synthesis of 1-trifluoromethyl-3-alkylidene-1,3-dihydrofuro[3,4-b]quinolines via 5-exo-dig cyclization of o-arylalkynylquinoline aldehydes

A convenient method for the facile synthesis of 1-trifluoromethyl-3-alkylidene-1,3-dihydrofuro[3,4-b]quinolines was developed from the TBAB-catalyzed nucleophilic addition/cyclization reaction of o-arylalkynylquinoline aldehydes with trimethyl trifluoromethyl silane, cesium fluoride, and water; the product was obtained in good to excellent yields. The reaction proceeded smoothly via 5-exo-dig selectivity and anti co-planarity addition, affording Z-selective products in an aerobic atmosphere at room temperature. The dihydrofuroquinoline derivatives formed are structurally related to the well-known furoquinoline alkaloids of the rutaceae family.

Ag(I)-Catalyzed one-pot synthesis of 4-fluorobenzo[b][1,6] naphthyridines and 4-fluoroisoquinolines via iminofluorination of alkynes with Selectfluor

Ag(I)-Catalyzed one-pot synthesis of 4-fluorobenzo[b][1,6]naphthyridines is described from o-alkynylquinolinyl aldehydes through imines in good to excellent yields. Selectfluor is used as a fluorinating reagent and the reaction proceeded at room temperature in an open atmosphere. Reactions employed in this synthesis method are also applied for the synthesis of 8-fluoro-1,6-naphthyridine, 7-fluoro-pyrazolo[4,3-c]pyridine and 4-fluoroisoquinoline derivatives. Standardized conditions were also applied on a gram scale reaction and gave a good yield of the product.

Active methylene compounds (AMCs) controlled facile synthesis of acridine and phenanthridine from morita Baylis–Hillman acetate

We carried out simple and facile syntheses of acridines and phenanthridines from MBH acetates of 2-chloro-quinoline-3-carbaldehydes with active methylene compounds (AMCs). Formation of products was found to be dependent on the functional group of the AMC. For example, ethylcyanoacetate and malononitrile favoured the formation of acridines and cyanoacetamide, and ethyl nitroacetate and malonic esters favoured formation of angularly-fused phenanthridines. The reactions leading to the formation of phenanthridines proceeded through single bond rotation of SN2′ intermediate which was attributed to electronic/steric repulsion between the functional groups of AMCs and the nitrogen of quinoline.

Copper-catalyzed cascade reaction: synthesis of pyrimido[4,5-b]quinolinones from 2-chloroquinoline-3-carbonitriles with (aryl)methanamines

Cu-catalyzed cascade reaction of 2-chloroquinoline-3-carbonitriles with benzyl amines and sodium hydroxide in aerobic atmosphere has been developed for the synthesis of pyrimido[4,5-b]quinoline-4-ones. The reaction proceeds sequentially via Ullmann-coupling and conversion of nitrile to amide followed by nucleophilic addition of amide nitrogen onto iminium carbon and air oxidation. Reagents and substrates are cheap and easily available/accessible. Plausible mechanism of reaction is also discussed.