Synthesis of indenofurans, benzofurans and spiro-lactones via Hauser–Kraus annulation involving 1,6-addition of phthalide to quinone methides

2020 ◽  
Vol 18 (29) ◽  
pp. 5677-5687
Author(s):  
Pallabita Basu ◽  
Nishikant Satam ◽  
Irishi N. N. Namboothiri
Keyword(s):  
Ring Opening ◽  
Ring Closure ◽  
Quinone Methide ◽  
Quinone Methides ◽  
Oxygen Heterocycles ◽  
Multiple Ring

Base mediated 1,6-addition–Dieckmann cyclization of phthalide with quinone methide leads to oxygen heterocycles such as indenofurans, spiro-lactones and benzofurans through a cascade of rearrangements involving multiple ring opening and ring closure.

Solvolysis and ring closure of quinone methides photogenerated from biaryl systems

2005 ◽  
Vol 83 (9) ◽  
pp. 1306-1323 ◽  
Author(s):  
Yijian Shi ◽  
Peter Wan
Keyword(s):  
Ring Closure ◽  
Quinone Methide ◽  
High Yield ◽  
Nanosecond Laser ◽  
Quinone Methides ◽  
Molecular Mechanics Calculations ◽  
Fluorescence Studies ◽  
Long Wavelength ◽  
Thermal Chemistry ◽  
Nanosecond Laser Photolysis

A variety of biaryl quinone methides have been photogenerated with a range of efficiencies from biaryl precursors 4–6 and 8, 10, and 11, all having hydroxyl and hydroxymethyl substituents on alternate rings. These novel biaryl quinone methides, which cannot be readily generated via thermal chemistry, are trapped by added nucleophiles such as MeOH and ethanolamine; two that cannot undergo electrocyclic ring closure (from 8 and 11) are readily observable by nanosecond laser photolysis, with long wavelength maxima (λmax) of 600 and 520 nm, respectively. Photogenerated o,o′-biaryl quinone methides undergo electrocyclic ring closure to give the corresponding chromene (pyran) products in high yield. Since the precursor biaryl alcohols have highly twisted structures in the ground state (dihedral angle of up to 90° by molecular mechanics calculations), a significant twisting motion to planarity is required to achieve reaction. Using steady-state fluorescence studies, we present evidence to suggest that the mechanism of quinone methide formation may occur via one of the following mechanisms: (i) dissociation of the proton from ArOH that precedes twisting; or (ii) ArOH dissociation and twisting taking place either simultaneously or in quick succession.Key words: biaryl quinone methide, photosolvolysis, photodeprotonation, photocyclization.

First Total Synthesis of a Fluorinated Calystegin

2010 ◽  
Vol 65 (4) ◽  
pp. 445-451 ◽  
Author(s):  
René Csuk ◽  
Erik Prell ◽  
Stefan Reißmann ◽  
Claudia Korb
Keyword(s):  
Total Synthesis ◽  
Ring Opening ◽  
Competitive Inhibitor ◽  
Ring Closure ◽  
Target Compound ◽  
Metathesis Reaction ◽  
Grubbs Catalyst ◽  
Ring Opening Reaction ◽  
Ultrasound Assisted ◽  
Key Steps

A straightforward chiral pool synthesis for the first fluorinated calystegin is described. Key steps of this synthesis include an ultrasound-assisted Zn-mediated tandem ring opening reaction followed by a Grubbs’ catalyst-mediated ring closure metathesis reaction. The target compound is a selective and competitive inhibitor for a β -glycosidase.

ChemInform Abstract: Synthesis of Functionalized Cyclophanes by Ring-Opening/Ring-Closure Cascade Reactions of Siloxycyclopropanes.

ChemInform ◽  
2010 ◽  
Vol 30 (21) ◽  
pp. no-no
Author(s):  
Astrid Ullmann ◽  
Margit Gruner ◽  
Hans-Ulrich Reissig
Keyword(s):  
Ring Opening ◽  
Cascade Reactions ◽  
Ring Closure

ChemInform Abstract: Ring Opening Ring Closure Reactions with 3-Substituted Chromones under Nucleophilic Conditions

ChemInform ◽  
2015 ◽  
Vol 46 (50) ◽  
pp. no-no
Author(s):  
Magdy A. Ibrahim ◽  
Nasser M. El-Gohary ◽  
Sara Said
Keyword(s):  
Ring Opening ◽  
Ring Closure

A new dehydrogenative [4 + 1] annulation between para-quinone methides (p-QMs) and iodonium ylides for the synthesis of 2,3-dihydrobenzofurans

2018 ◽  
Vol 5 (23) ◽  
pp. 3483-3487 ◽  
Author(s):  
Yan-Jie Xiong ◽  
Shao-Qing Shi ◽  
Wen-Juan Hao ◽  
Shu-Jiang Tu ◽  
Bo Jiang
Keyword(s):  
Quinone Methide ◽  
Quinone Methides ◽  
Iodonium Ylides

A new dehydrogenative [4 + 1] annulation of para-quinone methides (p-QMs) with acyclic and cyclic iodonium ylides has been established, delivering a variety of functionalized 2,3-dihydrobenzofurans with the retention of the quinone methide unit in generally good yields.

Furan Ring Opening—Isochromene Ring Closure: A New Approach to Isochromene Ring Synthesis.

ChemInform ◽  
2006 ◽  
Vol 37 (11) ◽  
Author(s):  
Alexander V. Butin ◽  
Valdimir T. Abaev ◽  
Vladimir V. Mel'chin ◽  
Artem S. Dmitriev
Keyword(s):  
Ring Opening ◽  
Furan Ring ◽  
Ring Closure ◽  
New Approach ◽  
Ring Synthesis

An unexpected thermal-ring-rearrangement of benzochromenes to inden-3-yl-naphthols with pTsOH

2018 ◽  
Vol 16 (42) ◽  
pp. 7920-7925 ◽  
Author(s):  
Srinivasarao Yaragorla ◽  
Tabassum Khan
Keyword(s):  
Ring Opening ◽  
Ring Closure ◽  
Acid Catalysts ◽  
First Report

Described here is the first report of an unexpected thermal-ring rearrangement (TRR) of benzochromenes to indene derivatives promoted by pTsOH, which proceeds through the protonation of benzochromenes by an acid catalysts followed by ring-opening and ring-closure by an intramolecular Friedel–Crafts cyclization.

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