scholarly journals Synthesis of spiroannulated and 3-arylated 1,2,4-trioxanes from mesitylol and methyl 4-hydroxytiglate by photooxygenation and peroxyacetalization

2010 ◽  
Vol 6 ◽  
Author(s):  
Axel G Griesbeck ◽  
Lars-Oliver Höinck ◽  
Jörg M Neudörfl
Keyword(s):  
Singlet Oxygen ◽  
Lewis Acid ◽  
Allylic Alcohols ◽  
Ene Reaction ◽  
X Ray ◽  
X Ray Crystallography ◽  
Homoallylic Alcohols ◽  
Acid Catalyzed ◽  
Benzaldehyde Derivatives

Cycloalkanones were utilized in the Lewis acid catalyzed peroxyacetalization of ß-hydroperoxy homoallylic alcohols (prepared by the ene reaction of the allylic alcohols mesitylol and methyl 4-hydroxytiglate, respectively, with singlet oxygen) to give spiroannulated 1,2,4-trioxanes 5a–5e and 9a–9e, respectively. A second series of 3-arylated trioxanes 10a–10h, that are available from the hydroperoxy alcohol 4 and benzaldehyde derivatives, was investigated by X-ray crystallography.

Photooxygenation in polymer matrices: En route to highly active antimalarial peroxides

2005 ◽  
Vol 77 (6) ◽  
pp. 1059-1074 ◽  
Author(s):  
Axel G. Griesbeck ◽  
Tamer T. El-Idreesy ◽  
Anna Bartoschek
Keyword(s):  
Singlet Oxygen ◽  
Protoporphyrin Ix ◽  
Polymer Matrices ◽  
Allylic Alcohols ◽  
Ene Reaction ◽  
Highly Active ◽  
Determining Factors ◽  
Broad Variety ◽  
Covalently Linked

Photooxygenation involving the first excited singlet state of molecular oxygen is a versatile method for the generation of a multitude of oxy-functionalized target molecules often with high regio- and stereoselectivities. The efficiency of singlet-oxygen reactions is largely dependent on the nonradiative deactivation paths, mainly induced by the solvent and the substrate intrinsically. The intrinsic (physical) quenching properties as well as the selectivity-determining factors of the (chemical) quenching can be modified by adjusting the microenvironment of the reactive substrate. Tetraarylporphyrins or protoporphyrin IX were embedded in polystyrene (PS) beads and in polymer films or covalently linked into PS during emulsion polymerization. These polymer matrices are suitable for a broad variety of (solvent-free) photooxygenation reactions. One specific example discussed in detail is the ene reaction of singlet oxygen with chiral allylic alcohols yielding unsaturated β-hydroperoxy alcohols in (threo) diastereoselectivities, which depended on the polarity and hydrogen-bonding capacity of the polymer matrix. These products were applied for the synthesis of mono- and spirobicyclic 1,2,4-trioxanes, molecules that showed moderate to high antimalarial properties. Subsequent structure optimization resulted in in vitro activities that surpassed that of the naturally occurring sesquiterpene-peroxide artemisinin.

ChemInform Abstract: Lewis Acid Catalyzed Intramolecular Direct Ene Reaction of Indoles.

ChemInform ◽  
2011 ◽  
Vol 42 (18) ◽  
pp. no-no
Author(s):  
Bo Han ◽  
You-Cai Xiao ◽  
Yuan Yao ◽  
Ying-Chun Chen
Keyword(s):  
Lewis Acid ◽  
Ene Reaction ◽  
Acid Catalyzed

Lewis Acid Catalyzed Intramolecular Direct Ene Reaction of Indoles

2010 ◽  
Vol 122 (52) ◽  
pp. 10387-10389 ◽  
Author(s):  
Bo Han ◽  
You-Cai Xiao ◽  
Yuan Yao ◽  
Ying-Chun Chen
Keyword(s):  
Lewis Acid ◽  
Ene Reaction ◽  
Acid Catalyzed

The Methylene-bridged Dialuminium Compound R2Al-CH2-AlR2 [R=CH(SiMe3)2] as an Effective Chelating Lewis Acid – Adducts with Halides, Perchlorate and Isopropylamide

2012 ◽  
Vol 67 (10) ◽  
pp. 1081-1090 ◽  
Author(s):  
Werner Uhl ◽  
Christian Rösener ◽  
Christina Stefaniak ◽  
Tim Choy ◽  
Beate Jasper-Peter ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Organic Solvents ◽  
Lewis Acid ◽  
Stoichiometric Ratio ◽  
Acid Base ◽  
X Ray ◽  
X Ray Crystallography ◽  
Coordination Behaviour ◽  
Lewis Acid Adducts ◽  
Oxygen Atoms

The new methylene-bridged dialuminium compound Aryl2Al-CH2-AlAryl2 1b was synthesised from Cl2Al-CH2-AlCl2 and four equivalents of LiAryl [Aryl=C6H2(2,4,6-i-Pr)3]. A 1 : 2 stoichiometric ratio of the starting compounds afforded the dimeric aluminium halide (Aryl2AlCl)2 (2) by dismutation. The coordination behaviour of the related, but more easily available dialuminium compound R2Al-CH2-AlR2 [R=CH(SiMe3)2] 1a was explored. It yields the Lewis acid base adducts [M][R2Al-CH2-AlR2(μ-X)] [3a, M=Li(TMEN)2, X=Cl; 3b, M=Li(TMEN)2, X=Br; 3c, M=K(18-crown-6), X=ClO4; 3d, M=Li(TMEN)2, X=NH(i-Pr)] with X residing in a bridging position between the two Al atoms as evident from NMR spectroscopy and X-ray crystallography (3b, 3c, 3d). Compound 3c is a unique example of a stable, in organic solvents soluble adduct that features a ClO4- anion coordinated by an alkylaluminium compound via two of its oxygen atoms.

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