Please use this identifier to cite or link to this item: http://nopr.niscair.res.in/handle/123456789/14357
Title: Facile synthesis of new substituted aryl and heteroarylflavones by thermal and microwave assisted Suzuki-Miyaura coupling reaction
Authors: Joshi, Vidya
Hatim, Jaywant Govind
Keywords: Suzuki-Miyaura coupling
Flavones
Biphenyl derivatives
Boronic acids
4′-bromoflavone
Microwave heating
Issue Date: Jul-2012
Publisher: NISCAIR-CSIR, India
Abstract: Microwave assisted Suzuki-Miyaura coupling of 4'-bromoflavone <b style="mso-bidi-font-weight:normal">5</b> with substituted aryl and heteroarylboronic acids <b style="mso-bidi-font-weight: normal">6a-m</b> gives high yields of aryl and heteroarylflavones <b style="mso-bidi-font-weight:normal">7a-m</b>. Couplings have been carried out by three methods i) conventional heating with Pd(OCOCH<sub>3</sub>)<sub>2</sub> catalyst, in solvent DMF(N,N-dimethylformamide) and base, aqueous Na<sub>2</sub>CO<sub>3 </sub>(2<i style="mso-bidi-font-style:normal">N</i>) for 6-12 hr, at 110°C, yield 30-70%, ii) conventional heating with Pd[(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>P]<sub>4</sub> catalyst, in DMF and base, aq. Na<sub>2</sub>CO<sub>3 </sub>(2<i style="mso-bidi-font-style:normal">N</i>) for 6-12 hr, at 110°C, yield 40-72% and iii) Microwave heating with Pd[(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>P]<sub>4</sub> catalyst, in solvent (DMF+H<sub>2</sub>O, 5:2) and base, aq. Na<sub>2</sub>CO<sub>3</sub> (2<i style="mso-bidi-font-style:normal">N</i>) for 2-9 min, yield 50-87%. The substrate 4′-bromoflavone <b style="mso-bidi-font-weight:normal">5</b> has been synthesized from <i style="mso-bidi-font-style:normal">o</i>-hydroxyacetophenone <b style="mso-bidi-font-weight:normal">1</b> in 3 steps. Esterification of <b style="mso-bidi-font-weight:normal">1</b> with 4-bromobenzoyl chloride <b style="mso-bidi-font-weight:normal">2</b> with montmorillonite-KSF catalyst, DCE (1,2-dichloroethane) and Et<sub>3</sub>N (triethylamine) which gives 2-(4-bromobenzoyloxy)acetophenone <b style="mso-bidi-font-weight:normal">3</b>. Baker-Venkataraman rearrangement of <b style="mso-bidi-font-weight:normal">3</b> with pyridine and KOH further gives 1-(4-bromophenyl)-3-(2-hydroxyphenyl)propane-1,3-dione <b style="mso-bidi-font-weight: normal">4</b>, followed by cyclization of <b style="mso-bidi-font-weight:normal">4</b> with methanolic sulfuric acid (2.5%) which yields 4'-bromoflavone <b style="mso-bidi-font-weight:normal">5</b>, yield 82%.
Description: 1002-1010
URI: http://hdl.handle.net/123456789/14357
ISSN: 0975-0983(Online); 0376-4699(Print)
Appears in Collections:IJC-B Vol.51B(07) [July 2012]

Files in This Item:
File Description SizeFormat 
IJCB 51B(7) 1002-1010.pdf128.14 kBAdobe PDFView/Open


Items in NOPR are protected by copyright, with all rights reserved, unless otherwise indicated.