Umasish Jana

Iron(III)-Catalyzed Four-Component Coupling Reaction of 1,3-Dicarbonyl Compounds, Amines, Aldehydes, and Nitroalkanes: A Simple and Direct Synthesis of Functionalized Pyrroles

A simple, convenient, and multicomponent coupling strategy for the synthesis of highly functionalized pyrroles catalyzed by iron(III) salts has been developed. This strategy demonstrated four-component coupling reactions of 1,3-dicarbonyl compounds, amines, aromatic aldehydes, and nitroalkanes without an inert atmosphere. This methodology provides an alternative approach for easy access of highly substituted pyrroles in moderate to very good yields using four simple and readily available building blocks via one-pot tandem reaction. Notably, this method is very cheap, straightforward, and environmentally friendly compared to the existing methods.

Iron-Catalyzed Synthesis of Functionalized 2H-Chromenes via Intramolecular Alkyne−Carbonyl Metathesis

An iron-catalyzed intramolecular alkyne-aldehyde metathesis strategy of the alkynyl ether of salicylaldehyde derivatives has been developed which works under mild reaction conditions to produce the functionalized 2H-chromene derivatives. This protocol is compatible toward a wide range of functional groups, such as methoxy, fluoro, chloro, bromo, and phenyl groups. This method provides an atom-economical and environmentally friendly approach for the synthesis of a series of substituted 2H-chromenes.

Design of a Neutral Macrocyclic Ionophore, Synthesis and Binding Properties for Nitrate and Bromide Anions

A macrocyclic neutral ionophore 8 (X = O) capable of binding weakly coordinating anions such as nitrate and bromide in DMSO solution has been designed by a stepwise, deductive approach. The optimum geometrical arrangement of the hydrogen bond donor sites in the target ionophore was determined by DFT calculations. From these data, a suitable macrocyclic molecular framework was constructed. The 24-membered macrocyclic ionophore was synthesized by standard macrocyclization methods. NMR titrations revealed molecular complexes with defined 1:1 stoichiometries in DMSO for 8 (X = O) with nitrate, hydrogensulfate, acetate, cyanide, iodide, and bromide ions, while dihydrogenphosphate, sulfate, and chloride ions yielded aggregates of higher stoichiometry. The nitrate binding constants of 8 (X = O) are substantial for a neutral ionophore with defined binding sites in pure DMSO solution. Bromide ions, which have a similar ion radius, are bound with an even higher affinity. Chloride is obviously too small, and iodine too large, to form 1:1 complexes. The binding motif of 8 (X = O) was compared with related molecules of similar structure, such as 8 (X = S) and 19. As predicted from calculations, the small structural variations give rise to a complete loss of nitrate and bromide ion binding ability in DMSO. This sensitivity to geometrical changes and the affinity of 8 (X = O) to nitrate and bromide ions, which are poor hydrogen bond acceptors, confirm the predicted complementarity of ionophore binding site and anion geometry. According to DFT and MD calculations the higher affinity of 8 (X = O) to bromide than to nitrate is mainly due to the greater flexibility of the bromide complex and thus to its higher entropy. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Fe-catalyzed novel domino isomerization/cyclodehydration of substituted 2-[(indoline-3-ylidene)(methyl)]benzaldehyde derivatives: an efficient approach toward benzo[b]carbazole derivatives.

A new and efficient protocol to synthesize substituted benzo[b]carbazole derivatives has been demonstrated involving iron-catalyzed domino isomerization/cyclodehydration sequences from substituted 2-[(indoline-3-ylidene)(methyl)]benzaldehyde derivatives. The substrates could be easily made via Pd-catalyzed domino Heck-Suzuki coupling from 2-bromo-N-propargylanilide derivatives in high yields. Notably, the generality and efficiency of this two-stage domino strategy was further exemplified by the synthesis of a polycyclic benzofuran derivative.

Inexpensive and Efficient Synthesis of Propargylic Substituted Active Methylene Compounds Catalyzed by FeCl3

A highly efficient and practical method for the synthesis of propargylic substituted 1,3-dicarbonyl compounds with direct use of propargylic alcohols in the presence of inexpensive and environmentally benign FeCl3 (5 mol%) has been presented. The reaction works with varieties of substrates at room temperature without an inert atmosphere with an excellent yield. The present method can also be employed for the large-scale synthesis of propargylic substituted active methylene compounds.

Three-Component Coupling Synthesis of Diversely Substituted N-Aryl Pyrroles Catalyzed by Iron(III) Chloride

Abstract An efficient and operationally simple three-component coupling synthesis of varieties of N-aryl substituted pyrroles is described in the presence of sustainable and environmentally benign metal catalyst, FeCl3. This method provides a straightforward approach for the synthesis of N-aryl substituted pyrroles in good yields from easily accessible starting materials such as nitroalkenes, 1,3-dicarbonyl compounds, and primary aromatic amines. The reaction proceeds through a catalytic sequence of Fe(III)-catalyzed amination/Michael/cycloisomerization reactions. Supplemental materials are available for this article. Go to the publishers online edition of Synthetic Communications® to view the free supplemental file. GRAPHICAL ABSTRACT

Synthesis of Fused Dibenzofuran Derivatives via Palladium-Catalyzed Domino C–C Bond Formation and Iron-Catalyzed Cycloisomerization/Aromatization

A range of tetracyclic dibenzofuran derivatives bearing a variety of functional groups was readily synthesized via a two-stage domino strategy starting from propargyl ethers of 2-halo phenol derivatives. The first stage in the strategy involves Pd(0)-catalyzed domino intramolecular carbopalladation/Suzuki coupling via 5-exo-dig cyclization onto the alkyne, leading to 3-methylene-2,3-dihydrobenzofuran derivatives. In the second stage of the domino strategy, an iron(III)-catalyzed cycloisomerization and aromatization reaction produces tetracyclic benzofuran derivatives. This two-step sequence provides efficient access to diversely substituted polycyclic dibenzofuran derivatives in high yields and in an atom-efficient and environmentally friendly manner. Moreover, this strategy was also successfully used for the synthesis of a naturally occurring tetracyclic dibenzofuran, β-brazan.

Synthesis and Structure of Bis-Urea Phenazines

Substituted phenazines 7 and 15 with two urea units have been prepared and characterized. X-ray structure analyses are reported for intermediates 5, 9, 11b and 12. According to theoretical calculations the geometry of the two urea moieties in phenazines 7 and 15 should be well suited for the binding of trigonal planar anions, such as nitrate. NMR titration revealed that compound 15 indeed shows a weak interaction with nitrate ions in DMSO.

Metal-catalyzed Domino Synthesis of Benzophenanthridines and 6H-Naphtho[2,3-c]-chromenes

A new and efficient synthesis of tetracyclic phenanthridines and benzo[ c]chromenes has been described involving a metal-mediated two-step domino strategy. The first step involved efficient palladium-catalyzed domino carbopalladation/cross coupling, and the second step involved iron-catalyzed domino isomerization/cyclodehydration. The important features of this strategy include high yields, generality, wide substrate scope, and broad functional group tolerance. A plausible mechanism has been proposed to explain the formation of the product.