Author Topic: benzaldehydes to phenylacetones  (Read 32796 times)

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Barium

  • Guest
Acid catalysis
« Reply #60 on: October 06, 2003, 01:39:00 AM »
I have searched but not found anything interesting on that topic yet. Someone with online access to the major chemical search engines could perhaps give it a try?
The only requirement of the PTC is a hydrophobic nature and the ability to carry hydroxide ions from the water pahse to the organic phase where they can rip off protons. So, a large nuber of PTC's can be used.


Bandil

  • Guest
Acid catalysed Darzens condensation
« Reply #61 on: October 06, 2003, 10:08:00 AM »
The articles describing the acid catalysed Darzens condensation are according to "Advanced Organic Chemistry - fourth ed." :

Sipos; Schöbel; Baláspiri J. Chem. Soc. C 1970, 1154

and

Sipos; Schöbel; Sirokmán J. Chem. Soc., Perkin Trans. 2 1975, 805.

I don't have access to the two articles right now, but i'll post abstract + full PDF first thing in the morning!

Regards
Bandil


Bandil

  • Guest
Crap...
« Reply #62 on: October 07, 2003, 02:17:00 AM »
I'm sorry, but the library i have access to, is not carrying those articles. Anyone who's had more luck than I?


Rhodium

  • Guest
I thought those articles looked familiar...
« Reply #63 on: October 07, 2003, 05:27:00 AM »
Yes, both articles by Sipos has been retrieved a long time ago by lugh. Search for "darzen" in

Post 436354

(Rhodium: "Archive of  "Wanted References" Volume 1", Novel Discourse)
.

Rhodium

  • Guest
OR5: The Darzens Glycidic Ester Condensation
« Reply #64 on: February 13, 2004, 11:51:00 AM »
The Darzens Glycidic Ester Condensation
M.S. Newman & B.J. Magerlein

Organic Reactions, Vol 5, Ch. 10, pp. 413-440 (1949)

(https://www.thevespiary.org/rhodium/Rhodium/pdf/darzen.org.react.5-10.pdf)

Contents

Introduction
Scope and Limitations
Carbonyl Components
Halogenated Esters
Other Halogenated Compounds
Side Reactions
Selection of Experimental Conditions
Conversion of Glycidic Esters into Aldehydes or Ketones
Reactions of Glycidic Esters
Rearrangement
Reactions with Hydrogen Halides
Reactions with Ammonia and Amines Reduction
Grignard Reaction
Hydration
Reaction with Active Methylene Groups
The Dichloroacetate Synthesis
Experimental Procedures
Methyl -Methyl-,-epoxycyclohexylideneacetate
Ethyl -Methyl--p-tolylglycidate
Ethyl -Methyl--phenylglycidate
Hydratropaldehyde
Ethyl -p-Chlorophenylglycidate
Ethyl -Chloro--hydroxy--phenylbutyrate
Examples of the Darzens Glycidic Ester Condensation
Tables
I. Glycidic Esters
II. Glycidic Amides
III. -Chloro -Hydroxy Esters


dioulasso

  • Guest
Drazens in DMF with K2CO3 + PTC
« Reply #65 on: February 13, 2004, 01:09:00 PM »
I feel the need to point out this modification of the Drazens condensation wich has recently been discussed:

Post 487007 (missing)

(Fomalhaut: "Ïðîäâèíóòûé Äàðçàí", Russian HyperLab)


Though this interesting paper has been on Rhodium's I feel it hasnt been highlited enough.



Synthesis of Glycidic esters in a two-phase solid-liquid system
S. Gladiali and F. Soccolini

Synth. Commun. (1982), 12, 355

(https://www.thevespiary.org/rhodium/Rhodium/djvu/gladiali.djvu)




EXAMPLE OF EXPERIMENTAL


Preparation of 3,4-dimethoxyphenylacetone.

A suspension of anhydrous potassium carbonate (6.9 g, 50 mmoles) in DMF (7.8 ml, 100 mmoles) containing veratraldehyde (4.15 g, 25 mmoles), methyl alpha -chloropropionate (3.8 ml, 35 mmoles) and Aliquat 336 (0.5 g, 1.25 mmoles) was vigourously stirred under nitrogen at 40C for 46 hours. At this time the conversion, estimated by GLC (200C), was about 95%. The reaction mixture was processed as above and the ethereal solution containing the glycidic esters was stirred at room temperature with 50% aqueous NaOH (4 ml). A vigourous reaction took place immediatly and the sodium glycidate separated as a thick paste. The mixture was stirred for ten minutes and then water was added (50 ml). The aqueous solution was separated, acidified with HCl (pH= 1) and stirred at 40C until the evolution of carbon dioxide ceased(30'). The oily product which separated was taken up in ether (30 ml) and the ethereal phase was dessicated (Na2S04). Evaporation of the solvent gave crude 3,4-dimethoxyphenylacetone (3.87 g, 80% yield), more than 98% pure on GLC (180C): b.p. 138-140C(1Torr) (lit. 135C at 0.8 Torr) 16; NMR: 6.67 (m, 3H); 3.60 (s, 6H); 3.48 (s, 2H); 1.87 (s, 3H); M + m/e 194 (calcd. 194). When TEBA was employed as PTC catalyst for the Darzens condensation, the hydrolysis of the glycidic esters required more time to be complete (3 hours) and the overall yield was slightly reduced (72%).



silenziox

  • Guest
Quite old post, but still I'm wondering one...
« Reply #66 on: February 23, 2004, 06:11:00 AM »
Quite old post, but still I'm wondering one thing about the workup..

The methanol was removed by distillation in a rotovap and the ketone was isolated by steam distillation. The distillate was extracted with 3x75ml toluene and the collected toluene phases dried over MgSO4. The toluene was removed by distillation in a rotovap leaving a clear yellow oil.

As my rotovap is still broke I'll just evaporate the methanol off to get the crude ketone, but is there any reason to steam distill the ketone? Would just simple wash be enough for purification?


psyloxy

  • Guest
skip the pyridine, use cat. DMF !
« Reply #67 on: June 21, 2004, 02:57:00 PM »
J.Chem.Soc. Perkin Trans.1;10.1995;1247-1250

ethyl (R)-2-chloropropanoate

To neat ethyl (S)-lactate (50g, 424 mmol) containing DMF (0.3 ml) was carefully added neat SOCl2 (33ml). The mixture was refluxed until the evolution of SO2 ceased (3h). The crude mixture was poured onto ice and was extracted three times with ether. The combined ether extracts were washed with brine and dried (MgSO4) and the ether was evaporated under reduced pressure at room temperature. The resulting yellow oil was distilled to provide the title compound (43,6g, 319mmol, 75%), colorless oil; bp 143-145°C.

--psyloxy--

Rhodium

  • Guest
Benzaldehydes & Ethyl Chloroacetate: Darzen Rxn
« Reply #68 on: September 04, 2004, 01:47:00 PM »
Efficient Synthesis of ?,?-Epoxy Carbonyl Compounds in Acetonitrile:
Darzens Condensation of Aromatic Aldehydes with Ethyl Chloroacetate

Zong-Ting Wang, Li-Wen Xu, Chun-Gu Xia, Han-Qing Wang

Helvetica Chimica Acta, 87(8), 1958-1962 (2004)

(https://www.thevespiary.org/rhodium/Rhodium/pdf/darzen.ethyl.chloroacetate.pdf)

Abstract
The Darzens reaction of ethyl 2-chloroacetate (1) with aromatic aldehydes 2 in the presence of polymer-supported or nonsupported quaternary ammonium salts proceeds under mild conditions by phase-transfer catalysis to give the corresponding epoxides 3 in satisfactory yields (Tables 1 and 2). With both MeCN as solvent and polystyrene-supported catalysts, diastereoselective Darzens reactions proceed in excellent yields and short times, with a fair degree of stereoinduction.


Rhodium

  • Guest
Darzen Synthesis of Aryl-2-propanones etc.
« Reply #69 on: October 11, 2004, 09:43:00 PM »
Synthesis of 1-(2-Furyl)-2-alkanones
Eldon H. Sund and David Scott Hunter

J. Heterocyclic Chem. 11, 1123-1124 (1974)

(https://www.thevespiary.org/rhodium/Rhodium/pdf/darzen.arylalkanones.pdf)

In connection with our interest in enolizable ketones, it was found of interest to synthesize a series of 1-(2-furyl)-2-alkanones. Previously three of these ketones were prepared by Hass, et al.3 by the condensation of 2-furaldehyde and the requisite nitroalkane with subsequent reduction of the resulting nitroalkane to yield the ketone. This method lacks generality because of the difficulty in obtaining higher homologs of the nitroalkanes.

A convenient method of preparation of these ketones is the Darzens glycidic ester condensation and subsequent hydrolysis and decarboxylation of the glycidic ester to yield the requisite ketone. The ethyl 2-bromoesters were either purchased or prepared by the method of Schwenk and Papa4. These ethyl 2-bromoesters were condensed with 2-furaldehyde essentially as described by Ruzicka and Ehmann5. The resulting glycidic ester was not isolated, but rather saponified and decarboxylated in the usual manner to yield the 1-(2-furyl)-2-alkanone, usually in good yield.

Experimental

Preparation of 1-(2-Furyl)-2-alkanones

A mixture of 29.8 g (0.31 mole) 2-furaldehyde and 0.31 mole of the ethyl 2-bromoester were cooled to 5-10°C. While maintaining this temperature and with stirring a solution of sodium ethoxide prepared from 13.8 g. (0.60 mole) sodium in 150 mL of ethanol was slowly added to the aldehyde-ester mixture. The reaction mixture was stirred an additional 30 minutes at this temperature and then allowed to warm to room temperature with an additional 2 hours of stirring. Approximately 30 mL of water were added to the flask and the mixture stirred on a steam bath for 3 hours. The reaction mixture was cooled to room temperature and a sufficient quantity of dilute phosphoric acid was added to the solution to bring the pH in a range of 3-4. As the acid was added a large quantity of carbon dioxide was evolved. The ketone was extracted with ether, washed with 5% sodium bicarbonate solution, water and dried over anhydrous sodium sulfate. After removal of the ether by flash distillation the ketone was distilled through a Nester-Faust annular Teflon spinning-band column under reduced pressure. These ketones are shown in Table I.


References
[3] H. B. Hass, A. G. Susi and R. T. Heider,

J. Org. Chem. 15, 8-14 (1950)

(https://www.thevespiary.org/rhodium/Rhodium/pdf/nitro.alkene.derivatives.pdf)
[4] E. Schwenk and D. Papa,

J. Am. Chem. Soc. 70, 3626-3627 (1948)

(https://www.thevespiary.org/rhodium/Rhodium/pdf/alpha-bromination.carboxylic.acids.pdf)
[5] R. Ruzicka and T. Ehmann, Helv. Chim. Acta 15, 160 (1932)