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Bwiti
(PVC-Analog Taste-Tester)
05-27-02 13:44
No 314728
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Acetone Enolate Question
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I was reading Drone #342's enolate phenylacetone FAQ when an idea popped into my head. Rather than reacting bromobenzene with acetone enolate, could substituted/halogenated benzenes such as bromo-benzodioxole be used? Peace!<img src="../forum/images/icons_lightgrey/cool.gif" alt="cool" title="Cool" heigth="15" width="15"><br><hr>Love my country, fear my government.
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<font color="#FF0033">Rhodium</font><br>
<i>(<span title="The user's title at the time of posting">Chief Bee</span>)</i><br>
<span title="Posting date">05-27-02 22:15</span><br>
<span title="Link to this post by using the markup [314882]">No 314882</span><br>
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<b title="The subject of this post">The reactivity of 5-bromobenzodioxole would be ...</b>
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The reactivity of 5-bromobenzodioxole would be lower due to the electron-donating properties of the oxygens, but providing that the reaction is valid, it would theoretically work to some extent.
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Bwiti<br>
<i>(<span title="The user's title at the time of posting">PVC-Analog Taste-Tester</span>)</i><br>
<span title="Posting date">05-28-02 10:34</span><br>
<span title="Link to this post by using the markup [315106]">No 315106</span><br>
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<b title="The subject of this post">"but providing that the reaction is valid" Cool, ...</b>
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<font color="blue">"but providing that the reaction is valid"</font color="blue"><br><br> Cool, thanks! When you speak of the reaction's validity, are you referring generally to the successful reaction of chloro, iodo, and bromobenzene; Is the FAQ on your site a sure thing? Or, is it just the validity of the use of halogenated <b>substituted</b> benzenes that you're not sure of? Thanks and peace!<img src="../forum/images/icons_lightgrey/cool.gif" alt="cool" title="Cool" heigth="15" width="15"> <br><hr>Love my country, fear my government.
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<font color="#FF0033">Rhodium</font><br>
<i>(<span title="The user's title at the time of posting">Chief Bee</span>)</i><br>
<span title="Posting date">05-28-02 14:35</span><br>
<span title="Link to this post by using the markup [315160]">No 315160</span><br>
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<b title="The subject of this post">Somebody! Do it NOW!</b>
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In Drone's FAQ he has combined several tried and true enolate reactions:<br><br>Pinacolone Enolate + Bromobenzene + DMSO + FeSO4 <br>Acetone Enolate + Iodobenzene + DMSO + UV Irradiation<br>Pinacolone Enolate + Iodobenzene + DMSO<br>Acetone Enolate + Bromobenzene + Anhydrous ammonia + FeSO4<br><br>...to hopefully assume that:<br><br>Acetone Enolate + Bromobenzene + DMSO + FeSO4 <br><br>is something that will produce P2P in high yields. That remains to be discovered, as well as the reaction details - noone knows what the suitable reaction times is yet (although in the first ref they say the reaction with iodobenzene took one hour together with pinacolone enolate (which is more substituted and therefore a more stable/reactive enolate than that of acetone), and that together with bromobenzene reacted six times slower). <br><br>Also, the conditions needed for the production of acetone enolate has not been determined using OTC chemicals. In the refs they use KOtBu/Acetone, we don't know yet if easily made Mg(OEt)2 works, or NaOiPr. Iodobenzene is very expensive and involved to make, so we must hope for bromobenzene to be reactive enough to make the method attractive. And we definitely must test the method on unsubstituted bromobenzene before moving on to bromobenzodioxole. <br><br>I sound very sceptical, perhaps unnecessarily so, but I don't like to run around telling people that something definitely works until it has been proven in practice. The theory is just fine, I just wonder why noone has even tried it out - Drone posted this four years ago!
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Bwiti<br>
<i>(<span title="The user's title at the time of posting">PVC-Analog Taste-Tester</span>)</i><br>
<span title="Posting date">05-28-02 16:41</span><br>
<span title="Link to this post by using the markup [315196]">No 315196</span><br>
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<b title="The subject of this post">What's Holding Bees Back?</b>
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<font color="blue">"And we definitely must test the method on unsubstituted bromobenzene before moving on to bromobenzodioxole."</font color="blue"><br><br> That sounds like a much more sensible approach! I tend to jump too far ahead as far as applying crank chemistry to trippy amphetamines, and this behavior has gotten me burned before. Yeah, it's kind of crazy that the FAQ was posted 4 years ago and nothing new has popped-up; think it's because that at least in the U.S. bromobenzene's watched for obvious reasons. Shit, it's not like the stuff's listed, but I'd still be nervous about buying it. I've tried making it with bromine/benzene/iron, which didn't work, so I guess that pyridine is needed, or maybe iodine? I'm getting a picture flashing in my head that says "UTFSE".<img src="../forum/images/icons_lightgrey/cool.gif" alt="cool" title="Cool" heigth="15" width="15"> <br><br><hr>Love my country, fear my government.
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jim<br>
<i>(<span title="The user's title at the time of posting">Hive Bee</span>)</i><br>
<span title="Posting date">06-04-02 05:35</span><br>
<span title="Link to this post by using the markup [317362]">No 317362</span><br>
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<b title="The subject of this post">References for enolate formation</b><br>
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Here is something that I put together a long time ago....<br><br><br>From "Advances in Solution Chemistry", Edited by I. Bertin, yr 1981,<br>Library of Congress # QD540 I57 1980; article title "Reactions and<br> Behaviour of Organic Anoins in Two-Phase Systems", paragraph 4,<br> page 311<br><br>"... The low acidity of many CH acids requires, as a rule, only strong<br>bases: NaH, NaNH2, t-BuOK, etc., in strickly anhydrous organic <br>solvents, can be employed for the generation of carbonions. The use of<br> sodium hydroxide for the generation of carbonions is rather limited <br>because of the equilibrium <br><br>->C-H + NaOH <==> ->C(-)-Na(+) + H2O<br><br>is shifted to the left due to the high acidity of water, and also <br>because of its high hydrolytic activity. Both these limitations are<br> eliminated when sodium hydroxide is employed in the form of a <br>concentrated aqueous solution and the generation and reactions of the <br>carbonions are carried out in two-phase systems in the presence of TAA<br> salts or other sources of lipophliic cations [5]. Here the acid-base<br> equilibrium proceeds at the interface, producing carbonions in low <br>concentration in the inactive form of sodium derivetives anchored at <br>the phase boundary in a kind of absorbed state. Subsequently these <br>carbonions are continously transferred into the organic phase as the<br> TAA derivetives, where they enter into the required reactions,<br> thus shifting the acid base equilibrium to the right. <br><br>[Diagram]<br><br>This hyperbasic effect as well as the fact that the reacting compounds<br> contact with aqueous alkali only at the interface are the most<br> characteristic features of the catalytic two-phase generation of <br>carbonions. These conditions are efficently applicable for a vareity<br> of reactions of carbonions derived from CH acids of pKa value up to <br>22.<br><br>Such important processes as alkylation of arylacetonitriles,<br> cyclopentadiene hydrocarbons, aldehydes and ketones, esters, sulfones <br>etc., condensation of carbonions with aldehydes or ketones, the <br>Knoevenagel, Darzens, Micheal and related reactions as well as many <br>reactions involving sulfonium and phosphonium ylides have been <br>sucessfully carried out under these conditions.<br><br>...<br><br>Although hetrogeneity of the catalytic two-phase system prevents <br>alkaline hydrolysis of the reacting compounds, there are many cases in<br> which aqueous sodium hydroxide cannot be used as a base. We have <br>found that instead of NaOH, anhydrous sodium or potassium carbonates <br>can be used for the generation of anions, even from rather weak CH <br>acids. In these cases the systems contains organic reactants in <br>liquid phase, the catalyst (TAA salt or crown ether) dissolved in a <br>non-polar solvent and anhydrous alkali carbonate in the solid phase. <br> Here the acid base equilibrium occurs on the surface of the solid, <br>subsequently the carbonions are transformed from this absorbed state<br> into the organic phase in the form of TAA salts. The carbonates are<br>relatively mild bases so they can be used at relatively high tempatures<br> without decompostion of the starting materials and products. <br><br>This simple solid liquid system can be efficently applied in many<br> important reations involving carbonions and other organic anoins. It<br> is particularly useful for the alkylation of ethylmalonate,<br> cyanoacetate, and acetylacetate<br> [10] e.g.<br><br>CH2(COOEt)2 + C4H9Br --{Q(+)X(-)/Na2CO3}--> C4H9CH(COOEt)2<br><br>...<br><br>Even such weak CH acids as phenylalkylacetonitriles can be deprotonated<br> and acylated under these conditions [10]. <br>"<br><br>[10]- J. Org. Chem. 43:4682 (1978)<br><br>========================================<wbr>====<br><br>From "Pure and Applied Chemistry", Vol 43, yr 1975, page 439-462,<br>article title "Two-Phase Reactions in the Chemistry of Carbonions and<br>Halocarbenes- A Useful Tool in Organic Synthesis", by M. Makosza<br><br>"Abstract<br><br>Amoung numerous base-solvent systems usually applied for the generation<br> of carbanoins the two-phase system in which concentrated aqueous <br>sodium hydroxide solution in the presense of quaternary ammonium <br>compounds acts as the proton acceptor seems particularly useful. Under <br>these conditions, C-H acids up to 22 pKa value can be converted into <br>carbanions which exist in the organic phase as ion pairs with the <br>quaternary ammonium cation. Though the concentration of the carbanoins<br> is very low, and does not exceed that of the catalyst, numerous <br>reactions have been successfully performed under these conditions. <br>Thus, alkylation of various C-H acids, such as arylacetonitriles, some<br> esters, ketones, aldehydes, cyclopentadiene hydrocarbons, etc. <br>proceeds in this way with higher selectivity and yield compared to the<br> tradional conditions. The two-phase system is of particular advantage<br> for the generation of trihalomethylanions and dihalocarbenes <br>thereafter, as it allows us to carry out all the reactions typical for<br> these species in the simplest and most effective manner. It is <br>moreover mostly convenient for the reactions of some carbanions with <br>aromatic nitrocompounds (substitution of halogen and nitro group or <br>electron-transfer) which otherwise give rather poor results. And the <br>latest so far recognized application of this system in carbanions <br>chemistry is the reaction of halocarbanions and ylides leading to <br>oxiranes, cyclopropanes and alkenes. <br><br>The author's point of view is that the first common step of all these <br>reactions, namely proton abstraction with the formation of a carbanion <br>quaternary ammonium cation ion pair, occurs at the phase boundary.<br><br>The ion pair thus formed penetrates inside the organic phase where all <br>the subsequent steps (reactions of carbanions with various <br>electrophiles, formation and reactions of halocarbanions etc.) take <br>place."<br><br>page 455<br>"LIMITAIONS<br><br>The numerous examples of the successful application of two-pahse <br>catalytic and ion-pair extractive methods in the reaction of carbanions<br> and halocarbenes illustrate the great versatillity of these methods <br>in organic synthesis. There are of course severe limations in these <br>methods. The most important on results from the fact that only <br>relativity strong C-H acids can be anionized in the presence of <br>aqueous sodium hydroxide. So far it seems the upper pKa limit is <br>around 22, since the alkylation of fluorene still occurs whereas that <br>of acetonitrile does not under these conditions. The second limitation<br> is due to the instablity of some C-H acids in the presence of aqueous<br> alkali (e.g. hydrolysis of ester of other functional groups). <br>This limitation can often be overcome by the use of more stable t-butyl<br> esters, less concentration aqueous sodium hydroxide solutions, larger <br>amounts (up to equimolar) of quaternary ammoinium compounds etc. The <br>compounds reacting with carbanions or halocarbenes should also be <br>stable in the presence of aqueous alkali. This limitation is, however,<br> often overestimated since many alkali-sensitive compounds have been <br>successfully used in these reactions. Another significant limitation <br>of the catalytic procedure is that the products must not be stronger <br>C-H acids than the strating compounds, otherwise the former produce <br>relatively unreactive ion-pairs with the quaternary ammonium cations <br>and the reaction is arrested. In these cases and in the cases of <br>relatively strong C-H acids, the application of ion-pair extraction <br>procedures is usually advantagous as compared to the catalytic or <br>tradional homogeneous ones. The requirement that poorly solvated <br>inorganic anions (e'g' I(-)) should not be formed in the catalytic <br>process has not confirmed in some cases. Of course it does not limit <br>the 'ion-pair' extractive procedure."<br><br>page 443<br>"Esters and other carbonyl compounds<br><br>... The two-phase system with TEBA catalyst seems to be the most <br>convenient for the alkylation ofbenzylic ketones like desoxybenzoine <br>and phenylacetone [30]. The ion-pair extraction procedure has also <br>been very convenient for the alkylation of these ketones [21]. ..."<br><br>[21]- Tetraherdon Letters, 473 (1972)<br><br>[30]- Tetrahedron Letters, 1351 (1971); Roczn. Chem. 45, 1027, 2097 <br>(1971); Roczn. Chem. 47, 77 (1973).<br><br>page 456-460<br>"MECHANISM<br><br>...<br><br>Many observations are, however, better explained by the supposition <br>that the first step of the carbanionic reactions- the abstraction of <br>proton and the formation of ion-pair in the two-phase system- occurs <br>on the phase boundary. The ion-pair migrates subsequently into the <br>organic phase where all further reactons with the liberation of the <br>catalyst take place. These two alternative mechanisms are visualized <br>as follows:<br>[not verbatum, but format changed, where " -> " indicates 3 bonds, Q <br>is the quaternary, X is the electrophile]<br><br>->C-H(org) + Q(+)X(-)(org) + NaOH(aq) <==> ->C(-)Q(+)(org) + NaCl(aq)<br><br>->C(-)Q(+)(org) + R-X --> Q(+)X(-) + ->C-R<br><br>or...<br><br>Q(+)X(-)(org) + NaOH(aq) <==> Q(+)OH(-)(org) + NaCL(aq)<br><br>->C-H(org) + Q(+)OH(-)(org) <==> ->C(-)Q(+)(org) + H2O(org-->aq)<br><br>C(-)Q(+)(org) + R-X --> Q(+)X(-)(org) + ->C-R(org)<br><br>========================================<wbr>===<br><br>From " The Journal of Organic Chemistry", Vol 43, No 3, yr 1978,<br>page 4682, article title "Sodium and Potassium Carbonates: Efficent <br>Strong Bases in Solid-Liquid Two-Phase systems[1]"<br><br>"Summary: Anhydrous potassium and sodium carbonates in the presence of<br> catalysts-tetraalkylammonium salts or crown ethers were found to be <br>efficent strong bases for generation and reaction of a variety of <br>carbanions.<br><br>Sir: A recent paper by White [2], in which the alkylation of diethyl<br> malonate, ethyl cyanoacetate, and some other compounds in the presence<br> of potassium carbonate in DMF was reported, prompts us to to publish a<br> preliminary communication describing some of our results concerning <br>the application of alkali metal carbonates as efficent strong bases. <br><br>Amoung the wide variety of basic agents employed for the generation of <br>carbanions, concentrated aqueous sodium hydroxide in the presence of <br>tetraalkylammonium salts or crown ethers is of particular interest [3].<br>Such reactions take place in a liquid-liquid two-phase system in which<br> both phases, aqueous sodium hydroxide and organic reactants (neat or <br>in organic solvent) are mutally immiscible. ...<br><br>Despite many advantages, the CTP [Catalytic Phase Transfer] system has <br>some limitations, one of them being the hydrolytic activity of <br>concentrated aqueous alkali. Although, due to the mutal immisciblity <br>of the phases, hydrolysis of starting materials and/or products <br>interfers much less than one would expect; carboethoxy and <br>carbomethoxy groups are hydrolyzed in this system to a considerable <br>extent. ...<br><br>We have found that many reactions proceeding via carbanions can be <br>efficently carried out useing anhydrous sodium or potassium carbonates<br> as bases. In these cases the reaction proceed in liquid-solid <br>two-phase systems. ... In this system reactions are catalyzed by <br>tetraammonium salts or crown ethers. The catalysts are unable to <br>transfer carbonate anions ( CO3(2-) ) into the organic phase [4], thus <br>solid-liquid phase transfer phenomena are probably not involved here.<br>It is more plausible that the first step, namely proton abstraction, <br>takes place on the surface of the solid carbonate. ... Since ahydrous<br> alkalicarbonates from fine powders with well devolped surfaces and <br>show no tendency to form lumps, the speed of stirring is is not of <br>crucial importance. When K2CO3 or Na2CO3 are used as bases the <br>reaction should be carried out at higher tempatures than if aqueous <br>NaOH is used in the CTP system. This normally does not cause any <br>difficulties, since the carbonates are rather mild bases. <br><br>Up to now the following reactions have been found to proceed efficently<br> in the presence of alkali carbonates. <br><br>...<br><br>3. Alkylation and nitroalkylaton of diphenylacetaldehyde.<br><br>Ph2-CHCHO + RX --{ K2CO3/crown }--> Ph2-C=CHOR<br><br>Exclusively O-alkyated derivetives are formed in high yeilds.<br><br>...<br><br>9. Williamson ether synthesis.<br><br>C4H9Br + C4H9OH --{ K2CO3/18-crown-6 }--> C4H9OC4H9<br><br>...<br><br>[1]- Paper 86 in the series Reactions or Organic Anions, Part 85;<br> A. Jonczyk, Z. Ochal, and M. Makosza, Synthesis, in press.<br><br>[2]- D. A. White, Synth. Commun., 7, 559 (1977), and refernces sited <br>therein. One should mention a paper by R. M. Boden [Synthesis, 784 <br>(1975)] describing the use of potassium carbonate for the generation <br>of phosphonium ylides and subsequently the Wittig condensation. <br><br>[3]- Pure and Applied Chemistry, 43, 439, (1975); W. P. Weber and G. <br>W. Gokel, "Phase Transfer Catalysis in Organic Synthesis", Springer<br> Verlag, West Berlin, 1977.<br><br>[4]- We have found that CO3(-2) anions (determined as total <br>alkalinity) are not transferred into acetonitrile on [<- a missprint I <br>believe, rather "or"] benzene solution from solid phase of K2CO3 either <br>by 18-crown-6 or by tetrabutylammonium bromide."<br><br>========================================<wbr>========<wbr>========<wbr>=<br><br>From "Tetrahedron Letters", No 18, pp 1351-1352, yr 1971, article title<br>"REACTIONS OF ORGANIC ANIONS. XXVI. x/CATALYTIC ALKYLATION OF KETONES<br>IN AQUEOUS MEDIUM", by A. Jonczyk, B. Serafin, and M. Makosza<br><br>"... we found recently that ketones can be readily transformed into <br>[alpha]-alkylated products when reacted with alkyl halides in the <br>presence of 50% aqueous NaOH and catalytic amounts of triethylbenzyl-<br>ammonium chloride /TEBA/. The catalytic effect of the latter on the <br>reaction yield was particularly strong in the case of weakly active <br>alkylating agents. Thus, phenylacetone and Bu-Br in 50% NaOH gave <br>about 5% of 3-phenylheptanone /I, R=C4H9/, whereas in the presence of <br>TEBA the yield increased to 90%. <br><br>Best results were obtained in the case of ketones with an aromatic <br>substituent at the [alpha]-CH2 group; phenylacetone and deoxybenzion <br>yielded monoalkyl derivetives /I/xx/; with active alkylating agents, <br>e.g. benzyl or alkyl chloride, used in excess, [alpha], [alpha]-<br>disubstitution /II/ occured. ...<br><br>I___Ph-(CH)R-COCH3<br><br>II__ Ph-(CRR)-COCH3<br><br>...<br><br>... Catalytic alkylation of other ketones, e.g. acetophenone, cyclo-<br>hexanone and acetone, yielded mixtures of mono-, di- and O-alkylated <br>products, monoalkyl derivetives being usually preponderant.<br><br>The new method provides a convenient route for the synthesis of <br>[alpha]-substituted ketones. It eliminates inflammable solvents and <br>unstable condensing agents /NaNH, tert- alkoxide, Ph3CNa, BuMgBr/ used <br>in the procedures described eariler /3/. The yields are in many cases<br> superior to those reported in literature."<br><br>x/ = Part XXv. M Makosza and M Jawdosiuk, Chem. Comm., 648 /1970/<br><br>xx/ = Examples given for phenylacetone<br><br>/3/ = Bull. Soc. Chim., 31, 1073, /1922/; Chem. Rev., 12, 43 /1933/; <br> 20, 413 /1937/; Bull. Soc. Chim. France, 1040 /19656/; Record Chem. <br>Progr., 24, 43 /1963/; ibid., 28, 99 /1967/; Modern Synthetic <br>Reactions, p 184, yr 1965; Bull. Soc. Chim. France, 160 /1969/.<br> <br>========================================<wbr>==<br><br>
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