Sciencemadness Discussion Board

aldehyde conversion to ketone or propene question

SunriseSunset - 27-12-2015 at 14:08

Is it possible to convert a molecule with a 2-methylpropanal to a ketone or propene, that correspond to the following structures?

I uploaded an attachment to help explain what I'm talking about. It seems like a brain blender sort of problem, but I figured to ask.

Are any of these things possible?

steps.jpg - 45kB

[Edited on 27-12-2015 by SunriseSunset]

zed - 27-12-2015 at 16:39

Looks like kind of an exotic starting material. Wouldn't you just prefer to purchase some Eugenol? AKA clove oil. From there you can easily make either of the other two materials.

https://en.wikipedia.org/wiki/Eugenol

Available cheaper no doubt. http://www.ebay.com/itm/EUGENOL-1X4oz-Bottle-Dental-/2708645...

[Edited on 28-12-2015 by zed]

[Edited on 28-12-2015 by zed]

SunriseSunset - 27-12-2015 at 17:20

Thanks zed, but i'm just seeing if this could possibly work out in theory. I wouldn't dare waste such a material unless there was a sure route with plenty of experimental data. lol I'm conservative :p

Btw, I'm not concerned about the stereo chemistry. just only the bonds.

Here's an idea, what if FIRST oxidize the aldehyde to a carboxylic acid, and then decarboxylate it? That might get it partially the way there! to the shorter-chain alkane. :|

Then brominate the alkane with N-Bromosuccinimide, then use a strong base to yield the desired phenyl-1-propene

Or the phenylpropane could be oxidized to a secondary alcohol, then to the ketone desired. Not sure.

[Edited on 28-12-2015 by SunriseSunset]

CuReUS - 28-12-2015 at 08:17

Quote: Originally posted by SunriseSunset  
Is it possible to convert a molecule with a 2-methylpropanal to a ketone
there is a rearrangement to convert 2-phenylpropanal to phenylacetone using conc H2SO4 or HgCl2 given in strike's book " total synthesis 2 ", pg 186 (but it might not work for your compound,maybe the benzene ring needs to be alpha to the CHO for the rearrangement to work ? )
see this(for procedure)
http://www.sciencemadness.org/talk/viewthread.php?tid=19505
also see this
http://chemistry.mdma.ch/hiveboard/methods/000456276.html
Quote:
or propene

carbonyls can be converted to alkenes with this reaction
http://www.sciencemadness.org/talk/viewthread.php?tid=64659#...

[Edited on 28-12-2015 by CuReUS]

MeshPL - 28-12-2015 at 09:36

Here is a somewhat suitable conversion, not sure if reagents will fit your abilities:

1. Oxidise aldehyde to carboxylic acid. Choose mild oxidising agent, one that will not oxidise phenols, or benzylic carbons.

2. Decarboxylate carboxylic acid using Kochi reaction or Hunsdiecker reaction.

3a,b. Halogenated hydrocarbon with halogen atom in place of aldehyde group is your product. Now you can turn that into internal/external alkene mix by elimination or alcohol by nucleophilic substitution with base. Whichever you choose, you will need to select good reagents and reaction conditions, otherwise you will get a mixture of products. If you choose elimination, you will get a mixture of internal, external alkenes anyway. (I guess ~70%/30% each).

3c. External alkene can be main product of Hofmann elimination and Cope elimination, you will first need to convert your halocarbon to quatenary ammonium hydroxide or tertiary amine oxide. Than you heat it/pyrolyse it. Yield of external alkene compared to internal can be good although there are extra steps involved.
Quote:

Here's an idea, what if FIRST oxidize the aldehyde to a carboxylic acid, and then decarboxylate it? That might get it partially the way there! to the shorter-chain alkane. :|

Then brominate the alkane with N-Bromosuccinimide, then use a strong base to yield the desired phenyl-1-propene.


Good idea, although N-Bromosuccinimide is not required, I think. Just bromine will quite selectively attack benzylic position. N-Bromosuccinimide is required for situations where double bonds are present, and could be attacked. Although, I'm not sure about overbromination by Br2 vs NBS.

[Edited on 28-12-2015 by MeshPL]

CuReUS - 28-12-2015 at 22:22

Quote: Originally posted by MeshPL  

Quote:

Here's an idea, what if FIRST oxidize the aldehyde to a carboxylic acid, and then decarboxylate it? That might get it partially the way there! to the shorter-chain alkane. :|

Then brominate the alkane with N-Bromosuccinimide, then use a strong base to yield the desired phenyl-1-propene.


Good idea, although N-Bromosuccinimide is not required, I think. Just bromine will quite selectively attack benzylic position. N-Bromosuccinimide is required for situations where double bonds are present, and could be attacked. Although, I'm not sure about overbromination by Br2 vs NBS.

The ring is quite activated,so ring bromination could be a significant side reaction using NBS or Br2