Upjohn Dihydroxylation Reaction And Mechanism: Green Chemistry

General Introduction:- 

• Cis diols is formed by KMnO4 & OSO4.
• Trans diols using peroxide and metal carbohydrate etc.

Reaction By Using KMnO4:- 

Mechanism :- 

Upjohn Oxidation:- It allow the syn selective preparation 1,2-diols from alkenes by the use of osmium tetraoxide as a catalyst and a stochiometric amount of an oxidant such as NMO (N-methyl morpholine-N-Oxidation)

Reaction:- 

There are two mechanism for upjohn dihydroxylations:-

1. Criege Mechanism
2. Sharpless Mechanism 

Important Points :-

• NMO used as a reoxidant for osmium tetraoxide.
• It will dehydroxylate all the alkene (but only alkenes)
• Electron withdrawing group  on the alkenes slow the reaction but do not stop it.
• Bulk of osmium complex results in dihydroxylation from least hindered face.
• Criege showed that the amine ligands increase rate o0f reaction.
• Presumbly an electron rich complex is formed increasing the reactivity of the oxygen atom.
• A second effect is to make the oxygen atoms better at H- bonding and thus reverse slecturty.
• Green Context:- Use a catalytic amount of toxic and volatile OSO4 due to the presence of NMO as reoxidant.

Next Topics:- Woodward cishydroxylation