Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: faust on October 16, 2005, 10:10:49 AM
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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
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Do you have access to an ozonolysis machine, I noticed your synthesis uses ozone?
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yes I have access, that not a problem. Only the first step is a problem for me...
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Check out the Bayliss-Hillman (http://www.organic-chemistry.org/frames.htm?http://www.organic-chemistry.org/namedreactions/sandmeyer-reaction.shtm) 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.
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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
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It doesn't have to be an aldehyde in the Bayliss-Hillman reaction. You might be able to use an alkyl bromide as well.
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The double bond in the ring wouldn't get chewed up first by ozone, so you could selectively perform ozonolysis.
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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.
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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.
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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...
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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...
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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...
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Oh, now i see your broblem :o really hard one ..Think about how to obtain alfa-halo derivate?
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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)
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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 :)