[orangbulu]

You can use several steps to accomplish this

http://img227.imageshack.us/img227/1397/sp3220071127233407ua6.gif

[agrobert]

What are your ideas?

You understand that you must react the propene to make a carbon-carbon bond but you must functionalize the propene in some way.  What is available to you?  Think about alkene oxidation and what types of selective haolgenations can be done at alylic centers.

[orangbulu]

Im still working on several solutions, will update this post on my progress

[puppy8800]

NBS substitutes propylene's alpha-H, +Mg yields Grignard reagent (1)
HBr addition(peroxide effect), hydrolysis, Swern oxidation yields (2)
(1) & (2) reacts, +B₂H₆, +H₂O₂(OH^-), TM.

it seems to be prolix...
waiting for better methods

[Rico]

Hey orangbulu

I would suggest the synthesis that i've outlined in the jpeg attached. Formation of the aldehyde is accomplished by hydroboration/oxidation of propene to n-propylalcohol, which is oxidized by a Swern oxidation. A Normant Grignard reagent is prepared by allylic bromination with NBS, followed by hydroboration/oxidation, protection of the alcohol with grignard reagent and formation of grignard reagent at the other end.
The aldehyde is reacted with the Normant Grignard reagent, which upon quenching with water gives the wanted product.

Rico

[Rico]

A little addition to my post above. Of course aqueous work-up is needed after the hydroboration/oxidation steps.

Rico