Search CORE

6 research outputs found

Synthesis of Medium Ring Azaheterocycles and Analogues from Carbohydrate Derivatives

Author: Das Adhikary Nirmal
Publication venue
Publication date: 01/08/2011
Field of study

The remarkable flowering of organometallic chemistry, notably of the transition metals, during the second half of the 20th century, has enriched and transformed chemical science to a degree and in ways that have few parallels in the history of the discipline. Of all organometallic chemistry known, palladium catalysis has achieved the status of an indispensable tool for both common and state-of-the-art organic synthesis. Palladiumcatalysed cross-coupling to form C–C bonds is one of the most frequently used catalytic processes for synthesizing medicinally active compounds. Examples of products prepared by this method are the antihypertensive drugs known as sartans1, the anti-asthma drug Singulair (montelukast sodium), products such as sunscreen2 and the polymers used for light-emitting diodes and for sensing the explosive trinitrotoluene (TNT)3–6. The intermediates that form the new C–C bond in the final product are classic organometallic species

EPrints@IICB Welcomes! - EPrints@IICB

Design and Synthesis of 1,2,3-Triazole-Fused Chiral Medium-Ring Benzo-Heterocycles, Scaffolds Mimicking Benzolactams

Author: Nirmal Das Adhikary (2073280)
Partha Chattopadhyay (1789183)
Publication venue
Publication date
Field of study

Based on “amide-triazole bioequivalence” principle, 1,2,3-triazole-fused chiral medium ring benzo-heterocycles capable of mimicking benzolactams were designed. Their syntheses were accomplished by cycloaddition of different sugar-derived azidoalkynes. While triazole-fused eight-membered benzo-heterocycles were formed by exclusive intramolecuclar [3 + 2] cycloaddition, attempted preparation of seven-membered analogues led to some intermolecular cycloaddition resulting in a dimeric macrocyclic product, in addition to intramolecular cycloaddition furnishing the expected heterocycle

FigShare

o-Iminobenzosemiquinonate and o-Imino-p-methylbenzosemiquinonate Anion Radicals Coupled VO2þ Stabilization

Author: Das Adhikary Nirmal
Ghosh Prasanta
Saha Roy Amit
Saha Pinaki
Publication venue: 'American Chemical Society (ACS)'
Publication date: 01/01/2011
Field of study

The diamagnetic VO2þ-iminobenzosemiquinonate anion radical (LR IS •-, R = H, Me) complexes, (L-)(VO2þ)(LR IS •-): (L1 -)(VO2þ)(LH IS •-)•3/2MeOH (1•3/2MeOH), (L2 -)(VO2þ)(LH IS •-) (2), and (L2 -)(VO2þ)(LMe IS •-)•1/2 LMe AP (3•1/2 LMe AP), incorporating tridentate monoanionic NNO-donor ligands {L = L1 - or L2 -, L1H = (2-[(phenylpyridin-2-yl-methylene) amino]phenol; L2H = 1-(2-pyridylazo)-2-naphthol; LH IS •- = o-iminobenzosemiquinonate anion radical; LMe IS •- = o-imino-p-methylbenzosemiquinonate anion radical; and LMe AP = o-amino-p-methylphenol} have been isolated and characterized by elemental analyses, IR, mass,NMR, and UV-vis spectra, including the single-crystal X-ray structure determinations of 1•3/2MeOH and 3•1/2 LMe AP. Complexes 1•3/2MeOH, 2, and 3•1/2 LMe AP absorb strongly in the visible region because of intraligand (IL) and ligand-to-metal charge transfers (LMCT). 1•3/2MeOH is luminescent (λext, 333 nm; λem, 522, 553 nm) in frozen dichloromethane- toluene glass at 77 K due to πdiimine f πdiimine* transition. The V-Ophenolato (cis to the VdO) lengths, 1.940(2) and 1.984(2) Å, respectively, in 1•3/2MeOH and 3•1/2 LMe AP are consistent with the VO2þ description. The V-Oiminosemiquinonate (trans to the VdO) lengths, 2.1324(19) in 1•3/2MeOH and 2.083(2) Å in 3•1/2 LMe AP, are expectedly ∼0.20 Å longer due to the trans influence of the VdO bond. Because of the stronger affinity of the paramagnetic VO2þ ion to the LH IS •- or LMe IS •-, the VNiminosemiquinonate lengths, 1.908(2) and 1.921(2) Å, respectively, in 1•3/2MeOH and 3•1/2 LMe AP, are unexpectedly shorter. Density functional theory (DFT) calculations using B3LYP, B3PW91, and PBE1PBE functionals on 1 and 2 have established that the closed shell singlet (CSS) solutions (VO3þ-amidophenolato (LR AP 2-) coordination) of these complexes are unstable with respect to triplet perturbations. But BS (1,1)Ms = 0 (VO2þ-iminobenzosemiquinonate anion radical (LR IS •-) coordination) solutions of these species are stable and reproduce the experimental bond parameters well. Spin density distributions of one electron oxidized cations are consistent with the [(L-)(VO2þ)(LR IQ)]þ descriptions [VO2þ-o-iminobenzoquinone (LR IQ) coordination], and one electron reduced anions are consistent with the [(L•2-)(VO3þ)(LR AP 2-)]- descriptions [VO3þ-amidophenolato (LR AP 2-) coordination], incorporating the diimine anion radical (L1 •2-) or azo anion radical (L2 3-). Although, cations and anions are not isolable, but electro-and spectro-electrochemical experiments have shown that 3þ and 3- ions are more stable than 1þ, 2þ and 1-, 2- ions. In all cases, the reductions occur with simultaneous two electron transfer, may be due to formation of coupled diimine/azo anion radical- VO2þ species as in [(L•2-)(VO2þ)(LR AP 2-)]2

EPrints@IICB Welcomes! - EPrints@IICB

One-Pot Conversion of Carbohydrates into Pyrrole-2-carbaldehydes as Sustainable Platform Chemicals

Author: Nirmal Das Adhikary (1554928)
Sangho Koo (1554925)
Sunjeong Kwon (1554931)
Wook-Jin Chung (500459)
Publication venue
Publication date
Field of study

A practical conversion method of carbohydrates into N-substituted 5-(hydroxymethyl)pyrrole-2-carbaldehydes (pyrralines) was developed by the reaction with primary amines and oxalic acid in DMSO at 90 °C. Further cyclization of the highly functionalized pyrralines afforded the pyrrole-fused poly-heterocyclic compounds as potential intermediates for drugs, food flavors, and functional materials. The mild Maillard variant of carbohydrates and amino esters in heated DMSO with oxalic acid expeditiously produced the pyrrole-2-carbaldehyde skeleton, which can be concisely transformed into the pyrrole alkaloid natural products, 2-benzyl- and 2-methylpyrrolo[1,4]oxazin-3-ones 8 and 9, lobechine 10, and (−)-hanishin 11 in 23–32% overall yields from each carbohydrate

FigShare

Electronic Structures of Ruthenium and Osmium Complexes of 9,10-Phenanthrenequinone

Author: Amarendra Nath Maity (2073283)
Manas Kumar Biswas (2073277)
Nirmal Das Adhikary (2073280)
Prasanta Ghosh (1655155)
Sarat Chandra Patra (1839820)
Shyue-Chu Ke (530067)
Publication venue
Publication date
Field of study

The reaction of 9,10-phenanthrenequinone (PQ) with [MII(H)(CO)(X)(PPh3)3] in boiling toluene leads to the homolytic cleavage of the MII–H bond, affording the paramagnetic trans-[M(PQ)(PPh3)2(CO)X] (M = Ru, X = Cl, 1; M = Os, X = Br, 3) and cis-[M(PQ)(PPh3)2(CO)X] (M = Ru, X = Cl, 2; M = Os, X = Br, 4) complexes. Single-crystal X-ray structure determinations of 1, 2·toluene, and 4·CH2Cl2, EPR spectra, and density functional theory (DFT) calculations have substantiated that 1–4 are 9,10-phenanthrenesemiquinone radical (PQ•–) complexes of ruthenium(II) and osmium(II) and are defined as trans-[RuII(PQ•–)(PPh3)2(CO)Cl] (1), cis-[RuII(PQ•–)(PPh3)2(CO)Cl] (2), trans-[OsII(PQ•–)(PPh3)2(CO) Br] (3), and cis-[OsII(PQ•–)(PPh3)2(CO)Br] (4). Two comparatively longer C–O [average lengths: 1, 1.291(3) Å; 2·toluene, 1.281(5) Å; 4·CH2Cl2, 1.300(8) Å] and shorter C–C lengths [1, 1.418(5) Å; 2·toluene, 1.439(6) Å; 4·CH2Cl2, 1.434(9) Å] of the OO chelates are consistent with the presence of a reduced PQ•– ligand in 1–4. A minor contribution of the alternate resonance form, trans- or cis-[MI(PQ)(PPh3)2(CO)X], of 1–4 has been predicted by the anisotropic X- and Q-band electron paramagnetic resonance spectra of the frozen glasses of the complexes at 25 K and unrestricted DFT calculations on 1, trans-[Ru(PQ)(PMe3)2(CO)Cl] (5), cis-[Ru(PQ)(PMe3)2(CO)Cl] (6), and cis-[Os(PQ)(PMe3)2(CO)Br] (7). However, no thermodynamic equilibria between [MII(PQ•–)(PPh3)2(CO)X] and [MI(PQ)(PPh3)2(CO)X] tautomers have been detected. 1–4 undergo one-electron oxidation at −0.06, −0.05, 0.03, and −0.03 V versus a ferrocenium/ferrocene, Fc+/Fc, couple because of the formation of PQ complexes as trans-[RuII(PQ)(PPh3)2(CO)Cl]+ (1+), cis-[RuII(PQ)(PPh3)2(CO)Cl]+ (2+), trans-[OsII(PQ)(PPh3)2(CO)Br]+ (3+), and cis-[OsII(PQ)(PPh3)2(CO)Br]+ (4+). The trans isomers 1 and 3 also undergo one-electron reduction at −1.11 and −0.96 V, forming PQ2– complexes trans-[RuII(PQ2–)(PPh3)2(CO)Cl]− (1–) and trans-[OsII(PQ2–)(PPh3)2(CO)Br]− (3–). Oxidation of 1 by I2 affords diamagnetic 1+I3– in low yields. Bond parameters of 1+I3– [C–O, 1.256(3) and 1.258(3) Å; C–C, 1.482(3) Å] are consistent with ligand oxidation, yielding a coordinated PQ ligand. Origins of UV–vis/near-IR absorption features of 1–4 and the electrogenerated species have been investigated by spectroelectrochemical measurements and time-dependent DFT calculations on 5, 6, 5+, and 5–

FigShare

Electronic Structures of Ruthenium and Osmium Complexes of 9,10-Phenanthrenequinone

Author: Amarendra Nath Maity (2073283)
Manas Kumar Biswas (2073277)
Nirmal Das Adhikary (2073280)
Prasanta Ghosh (1655155)
Sarat Chandra Patra (1839820)
Shyue-Chu Ke (530067)
Publication venue
Publication date
Field of study

FigShare