This study deals with a new and efficient metal-free regioselective synthesis of pyrimido-fused indazoles with nitrogen ring junction motifs. We have developed a metal-free domino type reaction between 3-aminoindazole, aryl aldehydes and aceotophenones in the presence of KOH/DMF that leads to pyrimido[1,2-b]indazole analogues. Response Surface Methodology (RSM) coupled with a Box-Behnken design (BBD) were utilized for exploring the effect of base used (A), temperature of reaction (B) and (C), reaction time. This approach can allow access to a variety of pyrimidoindazole fluorophores and related compounds. The compound N,N-dimethyl-4-(2-phenylpyrimido[1,2-b]indazol-4-yl)aniline (4e) displays the maximum fluorescence intensity at 518 nm and shows a fluorescence quantum yield of 0.068. The synthesized pyramido-fused indazoles have been evaluated for their free radical scavenging activity and compound 4f showed good antioxidant activity. © 2016 by the authors; licensee MDPI.

Mohana Roopan S

Department of Chemistry

School of Advanced Sciences

Vellore Campus

Mokeshrayalu G

Department of Mathematics

Palaniraja J

Al-Dhabi N.A

Arasu M.V.

Fulltext

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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Molecules

A series of imidazo-pyrimido fused acridines were synthesized and identified using conventional spectroscopic techniques. All the synthesized title compounds were subjected to in vitro antibacterial and insecticidal screenings. For insecticidal activity, the synthesized fused compounds are testing against two pests namely, Sitophilus oryzae (S. oryzae) and Callosobruchus maculatus (C. maculatus). For antibacterial screening, the compounds are testing against four bacteria, Bacillus subtilis (B. subtilis), Proteus mirabilis (P. mirabilis), Staphylococcus aureus (S. aureus) and Vibrio parahaemolyticus (V. parahaemolyticus). Notably, compound 8-(4-isopropylphenyl)-16-phenyl-6,7-dihydrobenzo[4′,5′]imidazo[1′,2′:1,2]pyrimido[4,5-a]acridine and 8-(2,4-dimethoxyphenyl)-16-phenyl-6,7-dihydrobenzo[4′,5′]imidazo[1′,2′:1,2]pyrimido[4,5-a]acridine were identified as the most promising applicant for further studies. © 2017 Elsevier B.V.

Journal of Molecular Liquids

Conventional spectroscopic identification of biologically active imidazo-pyrimido fused acridines: In vitro anti-bacterial and anti-feedant activity

An efficient synthesis of nitrogen ring junction pyrimido-indazoles has been developed.

RSC Advances

One-pot synthesis of highly functionalized pyrimido[1,2-b]indazoles via 6-endo-dig cyclization

In general, aryl-aryl transformations were investigated via transition metal-catalysed reactions. However, transition metal-mediated organic synthesis provided higher yields but has some flaws such as high cost, and the need for careful exclusion of air and moisture during the reactions. Possibly, there may be contamination of the product from traces of heavy metals present. To overcome these kinds of disadvantages, continuous efforts have been focused on the recent development of aryl-aryl formation through transition metal-free (TMF) reactions. However, most of these cross-couplings reaction were limited to hetero and electron-rich arenes which require strong inorganic bases. Our critical review includes a synthetic pathway to prepared X-aryl (X = C, N, O and S) motif by a transition metal-free scenario. Formerly, TMF reactions were carried out by various sources like strong bases, diazodium salt, aryliodonium salt, organo-catalysts and versatile energy sources like microwave heating, visible light and photochemical reactor. In this review, we have focused on the transition metal-free arylations. © 2014 Springer Science+Business Media Dordrecht.

Research on Chemical Intermediates

Synthetic journey towards transition metal-free arylations

The photochemical synthesis of a series of 2,3-dihydroquinazolin-4(1H)-ones were evaluated under the irradiation of visible light ({\textgreater}390 nm). The effect of the visible light mediated synthesis was carried out in the presence/absence of solvent. The effect of solvent plays a key role in the synthesis was evidenced through the formation of product in short duration. The solvatochromic effects of the fluorescent compounds (3a-k) were studied with respect to the solvents of increasing polarity (DCM {\textless} methanol {\textless} DMF {\textless} DMSO). The determination of in vitro anti-inflammatory activity of the compounds (3a-k) by the inhibition of bovine serum albumin (BSA) denaturation and 2,2-di(4-t-octylphenyl)-1-picrylhydrazyl (DOPPH•) radical scavenging consequence of the compounds (3a-k) were determined by spectroscopic technique. The compound 3j in DMSO exhibited extreme high quantum yield. The compound 3i was found to be superior both in the efficiency of the anti-inflammatory activity and radical scavenging ability.

Journal of Photochemistry and Photobiology B: Biology

2,3-Dihydroquinazolin-4(1H)-ones: Visible light mediated synthesis, solvatochromism and biological activity

We report an expeditious synthesis of selected indazolo-quinazolinone derivatives via an iodine-mediated multi-component reaction (MCR).

Iodine-mediated synthesis of indazolo-quinazolinones via a multi-component reaction

An expedient method for the synthesis of 5,6-dihydrobenzo[h][1,2,4]triazolo[5,1-b]quinazolines by UV light has been developed.

UV-light induced domino type reactions: synthesis and photophysical properties of unreported nitrogen ring junction quinazolines

A Metal-Free Regioselective Multicomponent Approach for the Synthesis of Free Radical Scavenging Pyrimido-Fused Indazoles and Their Fluorescence Studies

Journal	Molecules
Publisher	MDPI AG
ISSN	14203049
Open Access	Yes