please explain this multistep synth

[wall1two]

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i dont understand, the pcc turn the OH into an aldehyde.

then the methanol in acid turns the aldehyde into an a geminol diol.

then wouldn't the KMnO4 cleaves the double bond and leaves the adjacent carbon as an acid and the distal carbon as CO2?

 

[rodneymoss]

i dont understand, the pcc turn the OH into an aldehyde.

then the methanol in acid turns the aldehyde into an a geminol diol.

then wouldn't the KMnO4 cleaves the double bond and leaves the adjacent carbon as an acid and the distal carbon as CO2?

PCC is a mild-oxidant that converts 1 primary alcohols to aldehydes. KMn04 oxidant is stronger oxidant that forms COOH (caboxylic acid). By product I think should be H20. Try working out the mechanism.. im not 100 percent sure though.

 

[Kahr]

The PCC first makes the primary alcohol turn into an aldehyde.

Then, the methanol and H+ turn the aldehyde into a hemi-acetal.

We have KMnO4, but it doesn't say it's hot or concentrated, or both, so we assume it doesn't cleave anything. What we assume it does is open up the alkene into the diol like you see there at the end, adds syn by the way.

Now, the final part, H3O+, reverts the hemi-acetal to the aldehyde. You should remember that H3O+ always reverts these ketals and acetals (hemi as well).

Hope that helps.

 

[wall1two]

i dont understand, the pcc turn the OH into an aldehyde.

then the methanol in acid turns the aldehyde into an a geminol diol.

then wouldn't the KMnO4 cleaves the double bond and leaves the adjacent carbon as an acid and the distal carbon as CO2?

The PCC first makes the primary alcohol turn into an aldehyde.

Then, the methanol and H+ turn the aldehyde into a hemi-acetal.

We have KMnO4, but it doesn't say it's hot or concentrated, or both, so we assume it doesn't cleave anything. What we assume it does is open up the alkene into the diol like you see there at the end, adds syn by the way.

Now, the final part, H3O+, reverts the hemi-acetal to the aldehyde. You should remember that H3O+ always reverts these ketals and acetals (hemi as well).

Hope that helps.

awesome! thank you