Module I Oxidation Reactions - NPTel
Module I Oxidation Reactions - NPTel
Module I Oxidation Reactions - NPTel
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NPTEL – Chemistry – Reagents and Organic reactions<br />
Lecture 4<br />
1.4 Selenium and Aluminium Oxidants<br />
1.4.1 Selenium Dioxide<br />
Selenium dioxide (SeO2) is a colorless crystalline solid. It is soluble in solvents<br />
like dioxane, ethanol, acetic acid and acetic anhydride. It is extremely poisonous<br />
and should be carefully handled while working with it. However, it is very<br />
selective oxidant.<br />
William J. Hoekstra, Encyclopedia of Reagents for Organic Synthesis, John<br />
Wiely and Sons Inc., L. A. Paquette, Ed., New York, 1995, 6, 4437.<br />
1.4.1.1 Allylic <strong>Oxidation</strong><br />
Allylic oxidation is an important organic transformation because it provides a<br />
direct access to the allylic alcohols from the readily available alkenes (Scheme<br />
1). SeO2 is found to be an effective reagent for this transformation. The<br />
stoichiometric as well as catalytic amount of SeO2 can be used but the later<br />
requires an oxidant such as t-BuOOH to reoxidize the reduced selenium(II) to<br />
SeO2. The reactivity order in ethanol solvent is as follows CH2 > CH3 > CH but the<br />
order may change depending on the reaction conditions.<br />
Me<br />
Me<br />
Me<br />
CO 2Me<br />
SeO 2<br />
EtOH<br />
Joint initiative of IITs and IISc – Funded by MHRD Page 36 of 122<br />
Me<br />
Me<br />
OH<br />
CO 2Me