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All 2 posts Subject: On PTC reaction of acetone with halobenzene Please login to post Down

ning
(acetaminophanatic)
04-27-04 04:22
No 503258
User Picture On PTC reaction of acetone with halobenzene

This is a retread of the famous "much discussed but never done" Drone 342 enolate synth of P2P. Two of the big annoyances of this method are (1): the need for a strong base, and (2): the need for DMSO, a bothersome solvent to work with.

However, during recent studies on PTC technology, it struck ning that the pKa of acetone is pretty low, and would bee easily deprotonated under PTC conditions. Very likely chlorobenzene could be coerced into reacting under these conditions, and it is used as a solvent, should bee far less suspicious than bromobenzene. Has this been discussed or tried before?

Suggested procedure.

11.6 g acetone
11.3 g chlorobenzene (or 15.7 g bromobenzene)
16 g NaOH
1 g or so Na2CO3 to keep NaOH from wadding up
100 mg PTC like alkyl benzyldimethylammonium.

Grind NaOH and Na2CO3 together until powdered and well mixed. Place in 100 ml RBF and stir like a mofo at R.T. for a few hours to a day, then evaporate acetone and dilute mixture with water, and the P2P should seperate out. Distillation {may} be required, depending on the degree of overalkylation/aldol condensation that occurs. Perhaps a hydrolytic workup would undo some aldoling.

C6H5-Cl + CH3C(=O)CH3 --PTC--> C6H5-CH2-C(=O)-CH3
as well as
(Ph)2CHAc
(Ph)3CAc
Typically, PTC has less multiple alkylation than a corresponding strong-base reaction, if I am to believe what I read. That is good.

Could this work?

I've been chased by both cops and robbers. So what does that make me?

Nicodem
(Hive Bee)
04-27-04 19:26
No 503359
User Picture Just my doubts

The pKa of P2P is lower than the pKa of acetone. As a consequence any of the molecules of P2P formed would form a nucleophylic anion a few magnitudes more readily acetone, therefore getting further alkylated. But this is not really a problem since with such a system it would bee quite impossible to have the acetone anion stable for much time due to the presence of non-deprotonated acetone. Self condensation of acetone to diacetone alcohol would bee the consequence. Indeed the only way to use acetone anion is to make it really fast in a way that leaves no non-deprotonated acetone (that is with LDA or other super strong bases).

“The real drug-problem is that we need more and better drugs.” – J. Ott

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	All 2 posts		Subject: On PTC reaction of acetone with halobenzene		Please login to post		Down


		ning (acetaminophanatic) 04-27-04 04:22 No 503258				On PTC reaction of acetone with halobenzene
						This is a retread of the famous "much discussed but never done" Drone 342 enolate synth of P2P. Two of the big annoyances of this method are (1): the need for a strong base, and (2): the need for DMSO, a bothersome solvent to work with. However, during recent studies on PTC technology, it struck ning that the pKa of acetone is pretty low, and would bee easily deprotonated under PTC conditions. Very likely chlorobenzene could be coerced into reacting under these conditions, and it is used as a solvent, should bee far less suspicious than bromobenzene. Has this been discussed or tried before? Suggested procedure. 11.6 g acetone 11.3 g chlorobenzene (or 15.7 g bromobenzene) 16 g NaOH 1 g or so Na2CO3 to keep NaOH from wadding up 100 mg PTC like alkyl benzyldimethylammonium. Grind NaOH and Na2CO3 together until powdered and well mixed. Place in 100 ml RBF and stir like a mofo at R.T. for a few hours to a day, then evaporate acetone and dilute mixture with water, and the P2P should seperate out. Distillation {may} be required, depending on the degree of overalkylation/aldol condensation that occurs. Perhaps a hydrolytic workup would undo some aldoling. C6H5-Cl + CH3C(=O)CH3 --PTC--> C6H5-CH2-C(=O)-CH3 as well as (Ph)2CHAc (Ph)3CAc Typically, PTC has less multiple alkylation than a corresponding strong-base reaction, if I am to believe what I read. That is good. Could this work? I've been chased by both cops and robbers. So what does that make me?



		Nicodem (Hive Bee) 04-27-04 19:26 No 503359				Just my doubts
						The pKa of P2P is lower than the pKa of acetone. As a consequence any of the molecules of P2P formed would form a nucleophylic anion a few magnitudes more readily acetone, therefore getting further alkylated. But this is not really a problem since with such a system it would bee quite impossible to have the acetone anion stable for much time due to the presence of non-deprotonated acetone. Self condensation of acetone to diacetone alcohol would bee the consequence. Indeed the only way to use acetone anion is to make it really fast in a way that leaves no non-deprotonated acetone (that is with LDA or other super strong bases). “The real drug-problem is that we need more and better drugs.” – J. Ott

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