Synthesis-now stuck halfway

[miznaz]

Only allowed to use molecules that are 3 or less carbons to make the attached molecule. So I've started making this molecule and im stuck.

I started with propane.

 

Propane + Br2 + light --> bromopropane---> Mg, ether---> grignard + propanal + Hcl --> Ch3CH2CH(Ch3)OH---> PBr3 --> CH3CH2CH(CH3)Br....

added more Br, then NaOH +H20 to get BrCH(OH)CH(Ch3)Br--> PCC--> BrC=OCH(Ch3)Br + Ch3Ch2Ch2MgBr + Hcl---> see 2nd molecule attached.

 

and now im stuck.

 

i have a feeling theres an easier/simpler way to do this and i cant think of it. and if someone could help to get the last CH3CH2 on there and replace the H (red) to a CH3, that would be awesome!

[onequestion]

if you want to replace the h with ch3, simply use a methylating agent...

i.e. methanol or a methyl halide

 

R-H + ICH3 > R-CH3 + HI

 

to replace the oh with ch2ch3, first you will have to reduce it to h (use hydrogen gas + nickel catalyst or something like lithium borohydride)...

then use something like ethanol or an ethyl halide

 

R-H + ICH2CH3 > R-CH2CH3 + HI

Edited July 13, 2009 by onequestion

[John Cuthber]

"if you want to replace the h with ch3, simply use a methylating agent...

i.e. methanol or a methyl halide"

wrong.

[ope]

john do you do everything by the book or how about growing a brain

even if it doesn't work (idk maybe wrong hydrogen will be replaced) its logical.........

[UC]

john do you do everything by the book or how about growing a brain

even if it doesn't work (idk maybe wrong hydrogen will be replaced) its logical.........

 

You clearly have no idea at all what you're talking about. Kindy shut it.

 

To the author of the thread:

 

The way to approach this kind of problem is to backtrack through simple reactions. The molecule you want to make has bromines on adjacent carbons. This is the result of the textbook addition reaction of bromine across a ___________.

 

There are quite a few ways to make a _________, but there is probably one you have learned which utilizes triphenylphosphine.

 

I'll let you run with the rest of the problem. Hopefully that nudge got you going in the right direction

[Horza2002]

Sorry if its a bit late but heres how I'd try it. Ive outlined the route in an image below.

 

The first step involves the carbonylation of propene using a boron reagent. The subsequent steps would need to be performed in a certain order; but as youre trying to get a symmeterical product it will make the process much easier.

After the addition of carbon monoxide to the alkyl borane intermediate, water followed by H2O2/NaOH mixture would give you the hept-4-one needed for the next step.

 

This ketone can then be converted into the alkene with a Wittig reaction. An then simple electrophilic addition of Br2 to the alkene gives the product.

 

Hope that makes sence

[cpazchem]

Hey, i know its prob too late to be helpful. But, could someone read over my synthesis so i have an idea whether i am on the right track myself... I am not new to organic chemistry, but im only started second year uni (tho i am a few steps ahead of the bulk of the year), anyway, so if i dont know i particular way to do a reaction i will just discribe my thoughts if someone is ever able to elaborate on them.

 

Anyway, so, looking at the product (second picture) i can see two 3-carbon chains, essentially a propyl substituant, and "propane chain"... i know its a hexane chain, but breaking it into the 3 carbon blocks...

 

So, the propyl chain can be added using H3CCH2CH2Li (can be made from propene- bromination-etc) or being only 3 carbons, may be allowed straight up... Now, it will attack at a carbonyl group and make an alcohol, so thats that taken care of provided we make 1,2-dibromopropanal.

 

So, to make 1,2-dibromopropanal, i was invisioning starting with 1propenol, oxidising with PCC (wont oxidise the double bond, and stops at aldehyde) to 1propenal- then reaction with Br2 to give 1,2-dibromopropanal.

 

-----edit-----

If Br2 would oxidise the aldehyde, then protection using Tosyl Alcohol (TsOH) and ethylene glycol in benzene.

----end edit----

You can then alkylate this at the carbonyl using the n-propyl lithium, followed by acid work up.

 

Idk, but that seemed the simplest way? though i understand there would be many ways, but are there any major flaws in mine?

Edited April 1, 2010 by cpazchem
Added thought