[faust]

Hello

I'm looking for condition to do a tandem reaction for my first step.

i think a good way is the following : addition of PhS(e)Cl by michael addition than capture of the enolate by C akylation on bromopentene. Then oxydation and elimination of PhS(e)O2

But after two hours on Scifinder, I can't find conditions! (solvent, time of reaction, base?, equivalent)

Do you have any references with experimental conditions? Or any other idea for my synthesis of acid?

Thank you

[Mitch]

Do you have access to an ozonolysis machine, I noticed your synthesis uses ozone?

[faust]

yes I have access, that not a problem. Only the first step is a problem for me...

[movies]

Check out the Bayliss-Hillman reaction.

Also, ozone might chew up the double bond on the other side of your molecule.  I think other procedures like OsO₄/NaIO₄ are usually more selective and mild.

[faust]

yes I know the bayliss hilmann... but it's trapped with an aldehyde...

I have already tryed ozonolyse with this molecule and the "michael" double bond isn't converted into ozonide

[movies]

It doesn't have to be an aldehyde in the Bayliss-Hillman reaction.  You might be able to use an alkyl bromide as well.

[Mitch]

The double bond in the ring wouldn't get chewed up first by ozone, so you could selectively perform ozonolysis.

[movies]

Yeah, I figured that you might have a shot since it is electron deficient, but I wasn't sure how good the selectivity was in reality.

[HP]

What about if you start your synthesis from tetronic acid  to brominate its OH group by Appel reaction with CBr4/PPh3 and after that Grignard with  penteneMgBr.

[faust]

Sorry I didn't catch your reaction...

I start from tetronic acid (the same as my first molecule but with a OH in beta of the ketone) --> it become a Br and then I don't catch the reaction with penteneMgBr... It will do an addition 1-2 on my ketone...

[HP]

You are probably right about this side reaction...Then i suggest you to obtain organozink or cadmium derivate of your halopentene which may be much selective for your C-C forming  
Really complicated synthesis I'll think for anotrher rote...

[faust]

i can do an organozincic, but i'll do an addition 1.4 and be in beta of the carbonyle but i want to functionnalize the alpha position...

[HP]

Oh, now  i see your broblem   really hard one ..Think about how to obtain alfa-halo derivate?

[faust]

In fact I have seen a publication with the variant of Bayliss Hilmann.

They use Ph-Se-Li instead of DABCO. and they do an addition of an aldehyde... May be I can try to replace the aldehyde by the bromopentene... But I don't know if it is commercial or not (the bromopentene)

[HP]

Now i think a synthesis start from furan-2(5H)-one which if react addition with B2 to give 3,4-dibrom dihydrofuran-2-one. In this compound you have 2 Br athom close to different group: alfa and beta-position the carbonyl(CO) one.Then i suppose the alfa-brom will be much reactive with for example bromcadmium pentene and after C-C formin on alfa-position you siply have elimination with alcoholic KOH to eliminate HBr and may be to obtain desired product...I dont know try to imagine that synth