Suzuki reaction and silyl protection

[invite328658a2]

I've been trying to carry a Suzuki rxn out on an aryl bromide and a tbutyldiphenylsilyl- protected phenyl boronic acid but I have read ( Tetrahedron Utters, Vol. 38, No. 2, pp. 187-190, 1997) that the protecting group would not survive alkalinity of the reaction. The protection on phenolic OH is absolutely necessary and it must also get deprotected afer the Suzuki coupling easily. TBDPS and TOM look auspicious for the deprotection step but I first need to get away with their base sensitivity. Any suggestions?
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[Fajan]

tButyl Ester?

[HarleyApril]

Hi
I suppose Fajan means a pivaloyl ester
Benzyl ether could be an alternative choice
Additionnal substitutions with methoxy groups allows additionnal methods of deprotection

Le site étant plutôt francophone, la question est de savoir quel groupe protecteur on peut utiliser qui résisterait aux conditions basiques d'une réaction de Suzuki, les silylés ne seraient pas un bon choix selon la référence citée
cordialement

[shaddock91]

Bonjour.

Es-tu sûr que la protection du phenol est vraiment nécessaire ? J'ai déjà vu des réactions de Suzuki marcher sur des composés du type HO-Ar-B(OR)2 sans protection de la fonction phenol. Reaction classique dans H2O/EtOH ou toluène/Cs2CO3.

[A voir en vidéo sur Futura]

[invite328658a2]

Hiya all,
Well, I might have forgotten to add that the protecting group also needed to be removed EASILY. I tried benzyl but Pd/H2 deprotecting just gives me mess. The reaction is carried out in such a small schale that digging deproted product, if any, was unsussesful.
So the question still remains the same: what protecting group should be used that is:1- compatible with Suzuki reaction and 2- easily comes off afterwards

[invite3c6bdfb9]

hi
the TBDPS on a phenol might survive to Suzuki conditons. But, you dont really need to protect the it to carry the reaction out. As HarleyApril said the benzyl would be a good alternative if you've got a H2-reactor which will give you a very clean product afterward
bye

[invite328658a2]

I know it, but I need it protected for the rest of the synthesis.
thks btw

[shaddock91]

Hiya all,
Well, I might have forgotten to add that the protecting group also needed to be removed EASILY. I tried benzyl but Pd/H2 deprotecting just gives me mess. The reaction is carried out in such a small schale that digging deproted product, if any, was unsussesful.
So the question still remains the same: what protecting group should be used that is:1- compatible with Suzuki reaction and 2- easily comes off afterwards

You have to protect the OH group (I think it's not necessary). However, you can use the 4-MeOBenzyl protective group which is acid sensitive, for the deprotection (no catalytic hydrogenation ---> no mess ?).

[invite328658a2]

You have to protect the OH group (I think it's not necessary). However, you can use the 4-MeOBenzyl protective group which is acid sensitive, for the deprotection (no catalytic hydrogenation ---> no mess ?).

I KNOW OH protecting is not necessary for Suzuki ITSELF but I NEED IT FOR THE REST OF MY TOTAL SYNTHESIS.
Acid is also a big no no for me. I have acid hydrolysis problem in my structure

[shaddock91]

2-nitro benzyl group could be remove by photolysis, is it possible to use that way with your structure?

[invite328658a2]

2-nitro benzyl group could be remove by photolysis, is it possible to use that way with your structure?

huuum, photolysis doesn't look bad. I gotta look it up.
thnks

[HarleyApril]

résumé des épisodes précédents

arom à besoin d'un groupe protecteur de son phénol pour la suite de sa synthèse, il faut que le groupe tienne aux conditions de Suzuki
le benzyle et l'hydrogénation n'ont pas donné de bons résultats
un para-méthoxybenzyle ne convient pas car la molécule ne tiendrait pas aux conditions trop acides
shaddock propose donc un ortho-nitrobenzyl qui s'en va par photolyse

[HarleyApril]

we have also recently tried allyl with a deprotection by Pd(PPh3)4 and sodium borohydride

if compatible with the rest of your molecule !