9-(1H-indol-3-yl)-5-methoxy-3,3- dimethyl-2,3,4,9-tetrahydro-1H-xanthen-1-one

• 

  
  Green Chem., 2016, Advance Article
  DOI: 10.1039/C6GC00137H, Paper

  Someshwar D. Dindulkar, Daham Jeong, Eunae Cho, Dongjin Kim, Seunho Jung
  A novel biosourced saccharide catalyst, microbial cyclosophoraose, a cyclic [small beta]-(1,2) glucan, was used for the synthesis of indolyl 4H-chromenes via a one pot three-component Knoevenagel-Michael addition-cyclization reaction in water under neutral conditions.

Microbial cyclosophoraose as a catalyst for the synthesis of diversified indolyl 4H-chromenes via one-pot three component reactions in water

 http://pubs.rsc.org/en/Content/ArticleLanding/2016/GC/C6GC00137H?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FGC+%28RSC+-+Green+Chem.+latest+articles%29#!divAbstract

Microbial cyclosophoraose as a catalyst for the synthesis of diversified indolyl 4H-chromenes via one-pot three component reactions in water

Someshwar D. Dindulkar,^a   Daham Jeong,^a   Eunae Cho,^a  Dongjin Kim^b and   Seunho Jung*^ac  

*

Corresponding authors

^a

Institute for Ubiquitous Information Technology and Applications (UBITA) & Center for Biotechnology Research in UBITA (CBRU), Konkuk University, Seoul 143-701, South Korea 
E-mail: shjung@konkuk.ac.kr

^b

Nelson Mandela African Institution of Science and Technology, PO box 447, Arusha, Tanzania

^c

Department of Bioscience and Biotechnology, Microbial Carbohydrate Resource Bank (MCRB), Konkuk University, Seoul 143-701, South Korea

Green Chem., 2016, Advance Article

DOI: 10.1039/C6GC00137H

 As a novel biosourced saccharide catalyst, microbial cyclosophoraose, a cyclic β-(1,2) glucan, was used for the synthesis of therapeutically important versatile indolyl 4H-chromenes via a one pot three-component Knoevenagel–Michael addition–cyclization reaction of salicylaldehyde, 1,3-cyclohexanedione/dimedone, and indoles in water under neutral conditions. A possible reaction mechanism through molecular complexation is suggested based on 2D ROESY NMR spectroscopic analysis. Moreover, green chemistry metric calculations were carried out for a model reaction, indicating the satisfactory greener approach of this method, with a low E-factor (0.18) and high atom economy (AE = 91.20%). The key features of this protocol are based on two critical factors where the first is to use a novel eco-friendly supramolecular carbohydrate catalyst and the second is its fine green properties such as compatibility with various substituted reactants, recyclability of the catalyst, chromatography-free purification, high product selectivity, and clean conversion with moderate to excellent yields in an aqueous medium.

 9-(1H-indol-3-yl)-5-methoxy-3,3- dimethyl-2,3,4,9-tetrahydro-1H-xanthen-1-one (4a):

 (2-hydroxy-3-methoxybenzaldehyde 1, Dimedone 2

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Novel 1,2,4-triazolo[3,4-b][1,3,4]thiadiazine bearing substituted phenylquinolin-2-one moiety

Figure 1.

General structure of final synthesized derivatives.

Scheme 1. 

Synthetic Scheme for 1,2,4-triazolo[3,4-b][1,3,4]thiadiazine bearing substituted phenylquinolin-2-one (4a–4t). Where R = H, 2-Br, 3-Br, 4-Br, 2-Cl, 3-Cl, 4-Cl, 2-F, 3-F, 4-F, 2-NO₂, 3-NO₂, 4-NO₂, 2-CH₃, 3-CH₃, 4-CH₃, 2-OCH₃, 3-OCH₃, 4-OCH₃, 3,4,5-t-OCH₃. Reagents and conditions: (a) C₂H₅OH, Nitrobenzene, Con. H₂SO₄, reflux, 80 °C, 4 h; (b) chloroacetic acid, NaHCO₃, water, CuO, reflux, 80 °C, 5 h; (c) thiocarbohydrazide, Δ, 2 h; (d) phenacyl bromide, anhydrous ethanol, NH₄OH, 50 °C, 6 h.

 In the present work twenty derivatives of phenylquinoline-1,2,4-triazolothiadiazines were synthesized. The structures of the synthesized compounds were established by spectral data. According to IR spectroscopic data compounds (4a–4t) showed peaks at 1306–1330 cm⁻¹, 650–682 cm⁻¹ due to -NC and CSC stretching vibrations respectively and no absorption peaks at 3140–3280 cm⁻¹, 3050–3090 cm⁻¹ due to -NH₂ and -SH groups respectively indicated smooth cyclization of triazoles leading to the formation of thiadiazine ring. Further, ¹H NMR spectra of the synthesized compounds were confirmed by the appearance of SCH₂ proton of 1,3,4-thiadiazine ring at 4.40–4.54 ppm and CH₂ proton at 5.97–6.20 ppm as broad singlet. All other aromatic protons were observed at expected region. Mass spectra (ESI-MS) of all the synthesized compounds showed molecular ion [M + H]⁺ peak in agreement with their molecular formula. Physical and elemental analyses are listed in Table 1.

2.6.20. 6,7,8-Trimethoxy-4-phenyl-1-({6-phenyl-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazin-3-yl}methyl)-1,2-dihydroquinolin-2-one (4t)

White needle Crystal; IR (KBr, cm⁻¹): 3023 (Ar CH str), 2901 (Aliphatic CH str),1706 (CO str), 1620 (CN str), 1564 (CC str), 1330 (Ar CN str), 683 (CSC); ¹H NMR (CDCl₃, 300 MHz): δ (ppm): 3.84 (s, 9H, 3xOCH₃), 4.51 (s, 2H, SCH₂), 5.98 (s, 2H, CH₂), 6.85 (s, 1H, CH), 7.45(d, 2H, J = 8.5 Hz, ArH), 7.48(m,5H, ArH), 7.74 (q, 4H, ArH). ESI-MS (m/z) calcd. is 539.6, found 540.7 [M + H]⁺; anal. calcd. for C₂₉H₂₅N₅O₄S (539.60): C 64.55, H 4.67, N 12.98; found: C 64.54, H 4.63, N 12.95.

 Arabian Journal of Chemistry
 

Available online 11 July 2015

In Press, Corrected Proof — Note to users

ORIGINAL ARTICLE

Synthesis, characterization and antimicrobial evaluation of some novel 1,2,4-triazolo[3,4-b][1,3,4]thiadiazine bearing substituted phenylquinolin-2-one moiety

• Swagatika Ghosh^a, ,
• Amita Verma^{a, ,} ,
• Alok Mukerjee^b,
• Milan Kumar Mandal^a

• ^a Department of Pharmaceutical Sciences, Faculty of Health Sciences, Allahabad, Uttar Pradesh 211007, India
• ^b Department of Pharmaceutical Chemistry, United Institute of Pharmacy, UPSIDC, Naini, Allahabad, Uttar Pradesh 211010, India

Received 3 April 2014, Accepted 7 July 2015, Available online 11 July 2015

Open Access funded by King Saud University

Under a Creative Commons license

http://www.sciencedirect.com/science/article/pii/S187853521500218X

doi:10.1016/j.arabjc.2015.07.003

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CLAISEN R.......REACTION AND MECHANISM

A sigmatropic reaction in organic chemistry is a pericyclic reaction wherein the net result is one σ-bond is changed to another σ-bond in an uncatalyzed intramolecularprocess.^[1] The name sigmatropic is the result of a compounding of the long-established sigma designation from single carbon–carbon bonds and the Greek word tropos, meaning turn. In this type of rearrangement reaction, a substituent moves from one part of a π-bonded system to another part in an intramolecular reaction with simultaneous rearrangement of the π system. True sigmatropic reactions are usually uncatalyzed, although Lewis acid catalysis is possible. Sigmatropic reactions often have transition-metal catalysts that form intermediates in analogous reactions. The most well-known of the sigmatropic rearrangements are the [3,3] Cope rearrangement, Claisen rearrangement,Carroll rearrangement and the Fischer indole synthesis.









 3,3-sigmatropic reaarangment after that decarboxylation




The mecahnism involves the abstraction of proton from the active methylene group of the keto-ester followed by intramolecular Michael addition and decarboxylation to yield the unsaturated ketone compound

Firstly the ketoester tautomerize to give a enol ester and then a [3,3]-sigmatropic rearrangement occur (or simply called Claisen Rearrangement). After that, the substrate become a keto-acid and it undergoes decarboxylation under heat.

Claisen rearrangement

Main article: Claisen rearrangement

Discovered in 1912 by Rainer Ludwig Claisen, the Claisen rearrangement is the first recorded example of a [3,3]-sigmatropic rearrangement.^[10][11][12] This rearrangement is a useful carbon-carbon bond-forming reaction. An example of Claisen rearrangement is the [3,3] rearrangement of an allyl vinyl ether, which upon heating yields a γ,δ-unsaturated carbonyl. The formation of a carbonyl group makes this reaction, unlike other sigmatropic rearrangements, inherently irreversible.

Aromatic Claisen rearrangement

The ortho-Claisen rearrangement involves the [3,3] shift of an allyl phenyl ether to an intermediate which quickly tautomerizes to an ortho-substituted phenol.

When both the ortho positions on the benzene ring are blocked, a second ortho-Claisen rearrangement will occur. This para-Claisen rearrangement ends with the tautomerization to a tri-substituted phenol.

Cope rearrangement

Main article: Cope rearrangement

The Cope rearrangement is an extensively studied organic reaction involving the [3,3] sigmatropic rearrangement of 1,5-dienes.^[13][14][15] It was developed by Arthur C. Cope. For example 3,4-dimethyl-1,5-hexadiene heated to 300 °C yields 2,6-octadiene.

Oxy-Cope rearrangement

In the Oxy-Cope rearrangement, a hydroxyl group is added at C3 forming an enal or enone after Keto-enol tautomerism of the intermediate enol:^[16]

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