Babulal Das

Organocatalyzed One-Pot Synthesis of Substituted 1,5-Benzodiazepine and Benzimidazole Derivatives

An efficient synthesis of some heterocycles is described by condensation between o-phenylenediamine and 1,3-dicarbonyl compounds catalyzed by L-proline. The reaction is carried out either at room temperature or reflux depending on the substrates.

A rigorous variational formulation of an H plane slot-coupled tee junction

A rigorous analysis for the determination of an exact equivalent network for the slot-coupled H-plane tee junction that takes the effect of wall thickness into account is presented. A variational formulation is used for the determination of the parameters of the network. The parameters of the S-matrix as well as coupling are evaluated from the exact equivalent network. Comparisons between theoretical and experimental results are presented. >

An efficient stereo-controlled synthesis of bis-pyrimido-[4,5-d]-pyrimidine derivatives via aza-Diels–Alder methodology and their preliminary bioactivity

The one-pot synthesis of novel fused bis-pyrimido-[4,5-d]pyrimidine derivatives by a three-component reaction of 6-[(dimethylamino)methylene]1,3-dimethylaminouracil, terephthalaldehyde and amino derivatives has been depicted. The structures of the compounds were established by studying various spectroscopic methods and single-crystal X-ray crystallography. The long range W-coupling constant in 1H-NMR spectra is an infrequent example, where our synthesized novel compounds show such a distinctive constant. The synthetic strategy provides an efficient way to synthesise bis-pyrimidine-fused heterocycles that can be explored for further potential pharmaceutical or biological activities.

Coumarin to Isocoumarin: One-Pot Synthesis of 3-Substituted Isocoumarins from 4-Hydroxycoumarins and Benzyne Precursors

A novel transition-metal-free direct synthesis of 3-substituted isocoumarin from 4-hydroxycoumarin and a benzyne precursor is developed. This synthetic strategy proceeds via C-O and C-C bond cleavage as well as C-O and C-C bond formations in a single reaction vessel by simple treatment with CsF in the absence of catalyst. This methodology affords moderate to good yields of 3-substituted isocoumarins and is tolerant of a variety of functional groups including halide.

Stepwise formation of a pentanuclear Ni4Cu heterometallic complex exhibiting a vertex-sharing defective double-cubane core and diphenoxo- and phenoxo/azide bridging groups: a magnetostructural and DFT theoretical study.

Sequential reaction of a N5O3 octadentate tripodal ligand with Ni(2+) and subsequently with Cu(2+) and azide ligand afforded the first example of a heterobridged (phenoxo/μ(1,1)-azido) pentanuclear heterometallic (Ni4Cu) compound, which exhibits a centrosymmetric vertex-sharing defective double-cubane structure. The study of the magnetic properties reveals that the compound shows ferromagnetic interaction interactions, leading to an S = 9/2 spin ground state. Density functional theory calculations on the X-ray structure and model compounds predict ferromagnetic interactions through the magnetic exchange pathways involving each couple of metal ions.

Coordination complex of dipicolinato cobalt(III) complex cation and anion

Two examples of a new class of high oxidation state complexes having complex anion and complex cation of cobalt(III) are presented. The complexes [CoL(py)3][CoL2] · 2H2O (1) and [CoL(im)3][CoL2] · H2O (2) (where L = dipicolinato anion, py = pyridine and im = imidazole) are characterized by determining their crystal structures and studying their properties in solution. The complex anionic and cationic parts form layered structures through hydrogen-bond interactions with water molecule of crystallization. Alternate layers of complex cations and anions hydrogen bond with water molecules of crystallization to make tight packed structures.

Hydroxylation of azomethine carbon: isolation of complexes of η5 and η6-cyclic hydrocarbon platinum group metals with a new Schiff-base ligand

A new Schiff base, (pyridin-2-yl)-N-(3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-yl)methanimine, (L), was synthesized. Reaction of [(η6-arene)Ru(µ-Cl)Cl]2 and [Cp*M(µ-Cl)Cl]2 (M = Rh and Ir) with one equivalent of L in the presence of NH4PF6 in methanol yielded dinuclear complexes, [(η6-arene)2Ru2(L-OH)Cl](PF6)2 {arene = C6H6 (1), p-iPrC6H4Me (p-cymene) (2) and C6Me6 (3)}, and [Cp*2M2(L-OH)Cl](PF6)2 [M = Rh (4) and Ir (5)], respectively, leading to the formation of five new chiral complexes with –OH on the azomethine carbon. L is a pentadentate ligand where one of the metal centers is coordinated to two nitrogen atoms in a bidentate chelating fashion while the other metal is bonded tridentate to three nitrogen atoms. Although the ligand is neutral before coordination, after complexation it is anionic (uni-negative) with negative charge on the azo nitrogen {see the structures: N(5) in 2[PF6]2 and N(3) for 4[PF6]2}. The complexes have been characterized by various spectroscopic methods including infrared and 1H NMR and the molecular structures of the representative complexes are established by single-crystal X-ray diffraction studies.

Isolation and spectral studies of water-soluble η 5-cyclichydrocarbon rhodium and iridium complexes with pyridyl diketone analogues bonded through κ 2-N∩O, κ 4–N∩O, and κ3 -N-C-N modes

The reaction of [ M(µ-Cl)Cl]2 (M = Rh, Ir;  = η 5-C5Me5) with 1-phenyl-3-(2-pyridyl)propane-1,3-dione (pppdH) and 1,3-di(2-pyridyl)propane-1,3-dione (dppdH) in 1 : 2 and 1 : 1 molar ratio, respectively, yielded corresponding monomeric complexes [ M(κ 2-N-O-pppdH)Cl]+ [M = Rh (1), Ir (2)] and dimeric complexes [( )2M2(κ 4-N-O-dppd)Cl2]+ [M = Rh (3), Ir (4)]. The treatment of [ Ir(µ-Cl)Cl]2 with dppdH in 1 : 2 molar ratio yielded the activated monomeric complex [ Ir(κ 3-N-C-N-dppd)]+ (5). The formation of a C(sp3)–H is attributed to softer iridium, whereas Rh precursor yielded only the corresponding dimer 3. The formation of these complexes has been established by IR and NMR spectroscopic data and elemental analysis. Molecular structures of 2, 3, and 5 have been confirmed by single-crystal X-ray diffraction. The enolic “O–C–C–C–O” fragment of the coordinated ligand is neutral (κ 2-N-O-pppdH) in monomeric 1 and 2 and neutral as well as concomitantly uninegative (κ 4-N-O-dppd) in dimeric 3 and 4. In C–H-activated monomeric complex 5, the “O–C–C–C–O” fragment is in ketonic form with (κ 3-N-C-N-dppd) bonding of the ligand.

Organic cations controlling the nuclearity of copper(II) 2,5-pyridinedicarboxylates

Depending on the organo-cation mononuclear or polynuclear copper(II) 2,5-pyridinedicarboxylates (L) are formed. Mononuclear complexes with [ML2(H2O)] anions are formed when the cations are derived from ethylenediamine (en), N,N,N′,N′-tetramethylethylenediamine (tmen), 1,5-diaminopentane (dap) and 1,4-diazabicyclo[2.2.2]octane (dabco). The use of 4-amino-benzylamine (4aba) as the cation source leads to the hexa-coordinated mononuclear complex [CuL2(H4aba)2]·8H2O. The use of 1,8-diaminooctane (dao) results in a trinuclear complex with the [Cu3L6]6− anion. The trinuclear anion has copper ions in a square pyramidal and square planar geometry. The use of diethylenetetramine (deta) led to a coordination polymer which had unique hexa and penta coordinated copper ions. It is comprised of dinuclear copper 2,5-pyridinedicarboxylates bridged by mononuclear [ML2]2− units through side on contacts between the carbonyls on the dinuclear part. The 8-aminoquinolinium cations act as counter ions of the coordination polymer with [CuL2]2− repeat units. In this coordination polymer, the cations are π-stacked in one dimension. The variation in coordination numbers and the types of chains in the coordination polymers are described.

Tris-dipicolinate Cerium Complexes Bearing Dications of Arginine, Histidine, and Ornithine

Five tris-dipicolinate cerium (III and/or IV) complexes having dications of L-arginine (Arg), L-histidine (His) or L- ornithine (Orni), namely (H2Arg)[Ce(dpc)3].7H2O (1), (H2His) [Ce(dpc)3].4H2O (2), (H2Orni)[Ce(dpc)3].7H2O (3), (H2His)(HPy) [Ce(dpc)3]. 4H2O (4), and (H2Orni)(HPy)[Ce(dpc)3].7H2O (5) (dpc = dipicolinate, Py = pyridine) are synthesized and characterized. The cerium (IV) complexes (1, 2, 3) have one dication of the amino acids, whereas the cerium (III) complexes (4, 5) have one dication of amino acid together with one pyridinium cation. The role of the charge on the metal ion in the packing patterns is discussed and compared with bis-dipicolinate complexes of first row transition metal.