[esor]

I was wondering about ring-closing reactions...I started with cyclohexene and want to go to bicyclo [4,4,0] 2,4-decadiene.  I have the start and end, but I just don't know how to close the ring.  I got to butylcyclohexene and got a little stuck.  Then I created 2- (4-bromobutyl)-cyclohexenol but I don't know if I can close the ring from there.  Any suggestions?

[PRIYA1022]

Can you think of applying some photochemistry...or thermal rearrangements? What was the compound you start your synthesis with?

[esor]

I started with cyclohexene, then changed the double bond to an epoxide, then changed the epoxide to an alcohol and the alcohol to a keytone.  Then I used a Grignard (CH3CH2CH2CH2MgBr), changed the OH to a double bond, used BH3 to add an OH to the less substituted carbon.  That's where I got stuck---I'm not sure how to make my chain wrap around to join to the carbon with the OH group.  I guess I've never closed rings without making ethers out of them.  I've also worked backwards from my end product and haven't had a problem getting my double bonds added in the right places after I close the ring.  But once again, I keep getting stuck on the closing part : (

[esor]

I suppose I should also mention that I haven't learned any reactions beyond the alkenes yet...

[PRIYA1022]

Were you asked to start from cyclohexene?

[esor]

Yes, cyclohexene was given as the starting point.  Maybe I approached it all wrong...maybe I should try to add a ring to the cyclohexene instead of a chain.  The problem is that I would have to create the ring from the cyclohexene to use (those are the rules) and I would have the problem of trying to remove two carbons from it so that my bicyclo compound has only 10 carbons.

[Custos]

How about this as an idea. Think about a Diels-Alder reaction between cyclohexene and furane. Look at the product, you have the required carbon skeleton in one step... to get to your final product you only need to open up the oxygen bridge, dehydrate and isomerise the double bond around.

[PRIYA1022]

  A Diels Alder reaction between cyclohexene and cyclopenta-2,4-dienone, followed by a Chelotropic elimination of CO would give the product, but I am not sure if the elimination of CO here is favourable.
As posted by Custos, after opening the oxygen bridge I do not quite get how dehydration and  isomerization of the double bond would occur ,Could you please expand this idea?

[PRIYA1022]

You are missing a bond in your structure.
I would like to know how to attach a chemdraw sheet, or an alternative when posting questions /answers.
Thank You.