Sauron
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Phosphite ester Preparation
I'm interested in preparing dialkyl hydrogen phosphites and trialyl phosphites.
Getting PCl3 is a problem. What I am trying to find out is whether or not PBr3 also works. I am pretty sure PI3 does not.
Some sources indicate that PBr3 converts alcohols to alkyl bromides rather than forming the dialkyl or trialkyl esters.
Anyone have any experience in this regard or can point me at the appropriate definitive literature?
I usually search JACS and JOC thoroughly but the internet is acting up today and I can't get in.
PCl3 vs PBr3, is it a black and white thing? Or does PCl3 just give better yields? How to optimize conditions for the phosphite esters with the
tribromide?
Do Na/K/Mg alkoxides react better than the free alcohols with PBr3 (again, looking for the ester not the alkyl halide as product)
Tertiary amine acid scavenger? Pyridine, TEA, DiEtaniline?
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quino
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Preparation of phosphite ester
Liu, Deliang
PATENT NO.
CN 1493575
A process for prepg. phosphite ester includes esterifying reaction between PCl3, phosphorus oxychloride, or phosphorus thiochloride and alc. or
phenol while introducing the liq. mixt. of ammonium salt and phosphite for cooling the resultant, cooling to lower than 40°C by condenser, collecting
the resultant in said liq. mixt. while introducing ammonia to it, filtering for removing ammonium chloride to obtain coarse product, and rectifying.
Its advantages are high speed and high output rate.
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quino
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Preparation of phosphite ester type liquid alicyclic alkene compounds
PATENT NO.
CN 1459452 020514
Abstract
Title compds., e.g. (RO)3P (R = cyclohexenyl, cyclopentenyl, cycloheptenyl, cyclohexenylmethyl, etc.), are prepd. by esterifying alicyclic
alkenol with PX3 (at a molar ratio of 3.0:0.8-1.2) in solvent in the presence of tertiary amine at 50-80° for 0.5-2 h, neutralizing with NaOH soln.,
washing, concg., and vacuum distg. or purifying on chromatog. column. The solvent is benzene, toluene, xylene, THF, petroleum ether, dichloromethane,
acetone, etc. The PX3 is PCl3 or PBr3. The tertiary amine is triethylamine, tripropylamine, triallylamine, pyridine, etc.
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Sauron
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Thanks. Although I was taught from early on to not put too much faith in patent synthetic procedures, at least this gives me some hope for PBr3.
When the web is behaving again I will go root around in JACS and JOC.
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Sauron
International Hazard
Posts: 5351
Registered: 22-12-2006
Location: Barad-Dur, Mordor
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Got the articles thanks to solo, and got the answer I needed and it was the answer I was hoping for.
While PCl3 (unavailable now) is the more economical reagent and the best choice, it is indeed possible to prepare dialkyl hydrogen phosphites and
trialkyl phosphites with PBr3 (available) instead.
Trialkyl phosphites are subject to hydrrolysis at the P-O bond by hydrogen halides. Alkyl halides are byproducts.
The order of reactivity is HI>>HBr>>HCl
In the case of PCl3 this is sufficiently slow that in absence of an acid scavenger (tertiary amine) the dialkyl hydrogen phosphite is formed in
excellent yield. In presence of a tertiary amine and with efficient stirring (preventing local buildup of HCl) the trialkyl phosphite is formed.
With HBr in absence of tertiary amine the hydrolysis proceeds to the monoalkyl phosphite at room temperature, or the dialkyl hydrogen phosphite at -10
C. In presence of tertiary amine the temperature can be raised to prepare the dialkyl product or in the cold the trialkyl phosphite can be had,
I love it when a prep comes together.
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