[nottingham]

 Hi, guys,

Does anybody have idea how to selective oxidation cleavage of the terminal olefin if both a cis-disubstutited alkene and a terminal alekene presented in the same molecule.

Thanks.

[movies]

You might be able to get it with osmium tetraoxide, if the disubstituted olefin is significantly sterically hindered.

You could also do something elaborate with hydroboration/oxidation.  Large borane reagents (e.g. 9-BBN) are reasonably selective for terminal olefins.

Is there any other electronic difference between the two alkenes?  If one is conjugated to a carbonyl then you could likely epoxidize the other one selectively or possibly even do selective ozonolysis.

[nottingham]

Thanks for your very good ideas, but I have tried the dihydroxylation using OsO4, both of the double bond were reacted. As far as the hinderence concerned, I think the disubstituted alkene is much easier attackable because I can selective dihydroxylated the disubstituted alkene using AD mix.

I think boron reagent can react with the terminal olefin selectively, but what I want to do is to kick off the terminal olefin completely.

both of the alkene was reacted within 5 minutes during the process of ozonolysis.

It's really difficult to selective kick off the terminal olefin in very short steps. Any ideas? Thanks again.

[movies]

If you have a very hindered olefin, even if it is relatively electron rich, Os will be slow to dihydroxylate!

That's apparently not the case here though, obviously.

Have you tried a Prevost dihydroxylation (I₂, AgOAc) or the Woodward modification (adding AcOH and water)?  Probably not very selective either.

How about this: do a cross-metathesis with allyl alcohol (that would be selective for your terminal olefin) and then use that to do a directed epoxidation or directed dihydroxylation of the newly formed allylic alcohol.  It's a few steps, but I bet it'd work.