[The Guy]

Can I oxidize secondary alcohol in presence of double bond in the same molecule? they are not conjugated and far apart from each other.

I am thinking of PCC and I am afraid that it will oxidize the double bond too, to produce epoxied or alcohol.

Is the double bond sensitive to slightly acidic reagent?

Thank you

[Archer]

Look up the mechanism of PCC oxidation of alcohols, how does the hydroxyl group interact with the chromate ion? Would this interaction occur with an alkene?

Look up Corey & Suggs original paper for PCC oxidations for more detail.

[discodermolide]

I prefer either TEMPO/Bleach or a Swern oxidation.

[Archer]

I prefer either TEMPO/Bleach or a Swern oxidation.

I agree, PCC is very messy, in my experience Swern is superior provided you take precautions to keep the smell in the fume hood. I have never run a TEMPO/Bleach reaction so couldn't comment on it.

[spirochete]

A harder question would be how to selectively oxidize a C=C pi bond in the presence of a primary or secondary alcohol? I am now genuinely curious about the best way to do this. Do things like OsO₄ selectively dihydroxlate a pi bond or do they do funny side reactions with alcohols?

[Archer]

A harder question would be how to selectively oxidize a C=C pi bond in the presence of a primary or secondary alcohol? I am now genuinely curious about the best way to do this. Do things like OsO₄ selectively dihydroxlate a pi bond or do they do funny side reactions with alcohols?

Catalytic OsO₄ dihydroxylation reactions of olefins are carried out in acetone with t-butanol (used to disolve and store the highly toxic OsO₄) and tBuOOH to regenerate the OsO₄ so alcohols are unaffected.

[spirochete]

A harder question would be how to selectively oxidize a C=C pi bond in the presence of a primary or secondary alcohol? I am now genuinely curious about the best way to do this. Do things like OsO₄ selectively dihydroxlate a pi bond or do they do funny side reactions with alcohols?

Catalytic OsO₄ dihydroxylation reactions of olefins are carried out in acetone with t-butanol (used to disolve and store the highly toxic OsO₄) and tBuOOH to regenerate the OsO₄ so alcohols are unaffected.

But t-butanol is a tertiary alcohol. Isn't that significantly different than primary or secondary alcohols?

[Archer]

But t-butanol is a tertiary alcohol. Isn't that significantly different than primary or secondary alcohols?

Good point! But the generated diol in the catalytic cycle remains intact so the only question is whether 1° alcohols are affected.

This article suggests that additives are needed to facilitate oxidation of 1° alcohols by OsO₄

 http://www.sciencedirect.com/science/article/pii/0021951780903528

 

[zsinger]

Archer,
I am going to try the Swern tomorrow in my lab, and was wondering if you had any tips/why it is easier?  Separations easier?  Thanks.
       -Z

[Archer]

I am going to try the Swern tomorrow in my lab, and was wondering if you had any tips/why it is easier?  Separations easier?  Thanks.

As with everything it can be substrate dependent, what are you oxidising?

You have to keep the temperature low (-60°C) but the reaction is clean and the reaction bi-products are either gaseous or pretty volatile.

Only issue with my protocol is that the excess of DMSO (2.2 molar excess) can be difficult to remove if your product is particularly volatile or water soluble.

I had to make this molecule

Which Swern did not work out for me and so I resorted to PCC in DCM.

[discodermolide]

@Archer:
You really should give TEMPO/bleach a go. I have a procedure if you want to try it.

[Archer]

@Archer:
You really should give TEMPO/bleach a go. I have a procedure if you want to try it.

Happy to try anything new, please let me know either on here or PM.

Thanks

[AlphaScent]

Disco,

I would take that procedure if you are willing.  I am being asked to scale up a fickle oxidation of (4Z,2E)-Octadien-1-ol.

PCC on 10-20 grams is ok.  Still a pain in the ass.  It is done at like 0.1 M so a lot of DCM is involved and the work-up is hell even on that 20 grams.  100 or more is out of the question.

I would really enjoy reading it!!

PM me it or I can give you my email.