Synthesis of Polynuclear Heteroaromatics Mainly Based on Pyridine and Quinoline

The thesis embodies the results of studies on the “Synthesis of polynuclear heteroaromatics mainly based on pyridine and quinoline”. Quinoline and pyridine derivatives are a class of synthetic antibiotics with broad spectrum of antibacterial as well as anti-malarial activities. The fused pyridine and quinoline derivatives are also known to be effective in the treatment of autoimmune conditions (such as rhenumatoid arthritis) with their anti inflammatory effects. Among the numerous structurally diverse derivatives of pyridine and quinolines many show significant biological activity such as quinine, morphine, and multifloramine. Hence, it is not surprising that this structural motif is also an important component in many of today’s pharmaceuticals. Nevertheless, the diversity of pyridine and quinoline as well as their biological and pharmaceutical relevance is still motivating academic and industrial researchers to look for new and improved syntheses for quinoline derivatives. Clearly, a number of practical methods have been developed for the synthesis of pyridine and quinolines in the past century. More recently, especially transition metal catalysis has become a powerful tool for synthetic methodology but chemical and biological research has now presented a great challenge to synthesize and optimise highly efficient and cost-effective synthetic routes to some unique and novel biologically active substances

Cobalt-catalyzed ortho-C-H alkylation of 2-arylpyridines via ring-opening of aziridines

A cobalt–N-heterocyclic carbene catalyst, in combination with neopentylmagnesium bromide, was found to promote ortho-C[BOND]H functionalization of 2-arylpyridines with 1,2-diarylaziridines through ring-opening alkylation. The reaction affords 1,1-diarylethanes bearing 2-amino functional groups in moderate to good yields under mild room-temperature conditions

Ortho-C–H Benzylation of Aryl Imines with Benzyl Phosphates under Cobalt–Pyphos Catalysis

Ortho-C–H benzylation of aryl ketimines with benzyl phosphates is achieved with the aid of a catalytic system consisting of a cobalt­(II) salt, a phosphine/pyridine bidentate ligand, and a Grignard reagent under room-temperature conditions, affording a variety of diarylmethanes bearing <i>o</i>-acetyl or -acyl groups in moderate to good yields. Owing to the versatility of the <i>o</i>-acetyl group, the reaction opens useful synthetic routes to polycyclic compounds such as unsymmetrical anthracene, anthracenone, and anthraquinone derivatives

Basic alumina-supported highly effective Suzuki–Miyaura cross-coupling reaction under microwave irradiation: application to fused tricyclic oxa-aza-quinolones

Basic alumina used in lieu of traditional mineral bases efficiently promotes a solvent free, Pd(PPh3)4 catalyzed Suzuki–Miyaura cross-coupling reaction under microwave irradiation

Naphtho- and Benzo[g]quinoxalino-Fused Oxazocinoquinolinones and Their Diaryl and Alkynyl Analogues from Quinolin-8-ols: A Library of Novel Polynuclear Heteroaromatics

The efficient syntheses of 6,6,8,6,6-pentacyclic naphthofused oxazocinoquinolinones and 6,6,8,6,6,6-hexacyclic benzo[ g]quinoxalino-fused oxazocinoquinolinones were achieved in one-pot sequences. The generation of libraries of their diaryl- and alkynyl-substituted analogues via Suzuki–Miyaura and Sonogashira cross-coupling reactions, respectively, were also achieved

Synthesis and Characterization of Furo[3,2-h]Quinoliniums as Potent Non-Detergent Spermicides

7-Aryl substituted furo[3,2-h]quinoliniums have been synthesised in two steps from 5-chloro-8-hydroxy-7- iodo-quinoline through a tandem Sonogashira alkynylation-cyclization pathway using aryl acetylenes followed by quaternisation reaction with alkyl halides under microwave irradiation. The compounds have been characterized spectroscopically and assessed for their sperm-immobilizing efficacy in vitro by modified Sander–Cramer test. Most of the derivatives showed potent spermicidal effect with minimum effective concentration (MEC) ranging from 125�g/ml – 1mg/ml. The results were further confirmed by double fluoroprobe staining with syber14/PI (Propidium Iodide). The mode of spermicidal action was assessed by (a) Hypo-osmotic swelling tests and (b) Scanning electron microscopy. The compounds have been found to be nontoxic to lactobacillus in 36 hours of culture whereas mild to moderately effective on common vaginal pathogens. Taken together it can be inferred that the water-soluble salts prepared from facile technique are potential candidates for spermicides and could further be utilized for the preparation of vaginal contraceptives

Amberlite IRA 402(OH): An Efficient Mediator for the Exclusive Synthesis of Fused Tricyclic Oxaza Quinolinium Salts

A high yielding green protocol for the synthesis of tricyclic oxaza quinolinium salts has been developed using Amberlite IRA 402(OH) in water. This method is more effective compared to previously reported phase-transfer catalytic (PTC) condition in terms of yield of the product, reaction time and ease of separation

Facile Synthesis of 6,6,8,6,6-Ring Fused Pentacyclic Heterocycles: Annelation of Quinolines to Quinoxalines Under PTC Condition

An efficient and simple synthesis of pentacyclic quinolonoquinoxalinooxazocines in a one-pot sequence has been performed by unique application of phase transfer catalysis. Preparative simplicity and conceptual novelty of the methodology offer an attractive general application for the synthesis of novel quinoline antibiotics

Synthesis of Biaryl Pentacyclic Quinolonoquinoxalino-Oxazocines in Aqueous Medium Using Amberlite IRA 402(OH)

Amberlite IRA 402(OH) effectively mediates biarylation via Suzuki–Miyaura cross-coupling reaction on complex systems such as dihalo quinolonoquinoxalino-oxazocine

Efficient Synthesis of 3,3-diheteroaromatic Oxindole Analogues And Their in Vitro Evaluation For Spermicidal Potential

Syntheses of 3,3-diheteroaromatic oxindole derivatives has been achieved by coupling indole-2,3-dione (isatin) with differently substituted indoles and pyrrole in presence of I2 in i-PrOH. The in vitro spermicidal potentials and the mode of spermicidal action of the synthesized analogues were evaluated and the derivative, 3,3-bis (5-methoxy-1H-indol-3-yl) indolin-2-one (3d) exhibited most significant activity