Download Development of new methodologies involving ZrCl 4 as a Lewis acid

Séminaires & Conférences Chimie École Doctorale 459
Jeudi 02 Octobre 2008, 13h45
Salle de Cours SC-16.01 – Université Montpellier II
Department of Chemistry
Kakatiya University, Warangal-506 009
Development of new methodologies involving ZrCl4 as a Lewis acid catalyst
and Synthesis of (+)-epi-Cytoxazone
Dr. SMITHA GOUNI
IBMM, UMR 5247 -CNRS, UM 1 & UM 2, Faculty of Pharmacy, Montpellier
A friendly Lewis-acid catalyst must posses the following properties: easy availability, low
cost, low toxicity and high stability towards water and oxygen. The ability to work in solvent and
solvent-free conditions, as well as the possibility to recover and reuse the catalyst without loss of
efficiency is also noteworthy features. Zirconium belongs to group IV transition metals and it is
more abundant in the earth’s crust, which makes less costly and easily available. Fortunately, Zr
(IV) compounds generally have low toxicity (LD50 [ZrCl4, oral rat] = 1688 mg Kg-1) and are not
considered particularly poisonous. Additionally, Zr4+ with a high charge-to-size ratio (22.22 e2m10)6 enables reactions with high to excellent yields due to strong coordination of Zr4+. The ease of
handling and high catalytic activity makes the Zr (IV) compounds are potential green catalysts in
synthetic organic chemistry, as evidenced by their increasing commercial use for this purpose. Our
experience in using ZrCl4 as a Lewis-acid catalyst in various organic transformations involves
carbon-carbon bond formation, protection-deprotection chemistry etc. will be discussed (Fig 1).
Apart from this total synthesis of (+)-epi-Cytoxazone, a cytokine modulator, will also be presented
(Fig 2).
Cl
Organic Synthesis
• C-C bond formations
• Reductions
• ProtectionProtection-deprotections
O
HN
O
Cl
Zr
Cl
Figure 1
Cl
Easily available
Low toxic
Mild Lewis acid
Organometallics
• Reagents
• Complexes
OH
MeO
(+)-epi-Cytoxazone
Figure 2