Alkali amide

The alkali amides are stable, crystalline salts the heavy metal amides are often explosive. The amides are the bases of the ammonia system. 

The amount of metal required gives an indication of the water content. note 3. If the conversion takes longer, add some liquid ammonia to keep the volume of the suspension between 500 and 800 ml. iinte 4. The conversion of lithium and potassium into the alkali amides has never given problems. 

A.lkylation of 2-sec-aminothiazoles can be directed to the amino group if condensing agents such as alkali amides are used (46j, This reaction is... 

Action of alkali amides and alkyl- and aryl-lithiums on mono-halogeno aromatic compounds,... 

Dimethylaminoquinoline is converted into the 2-amino analog by potassium amide (liquid NHg, 20°, 18 hr). 4-Dimethy-laminoquinazoline exceeds the methylamino derivative in reactivity toward ammonium acetate or alkali amides. Hot acid or alkali... 

Sodium amide has been prepared by the action of gaseous 2 or liquid3 ammonia on sodium, by the action of ammonia on alloys of sodium,4 and by the electrolysis of a solution of sodium cyanide 5 in liquid ammonia with a sodium amalgam electrode. A summary of the chemistry of alkali amides is given by Bergstrom and Fernelius.1... 

Sneed, J. K., and R. Levine Condensations Effected by the Alkali Amides. 

Electron-transfer initiation from other radical-anions, such as those formed by reaction of sodium with nonenolizable ketones, azomthines, nitriles, azo and azoxy compounds, has also been studied. In addition to radical-anions, initiation by electron transfer has been observed when one uses certain alkali metals in liquid ammonia. Polymerizations initiated by alkali metals in liquid ammonia proceed by two different mechanisms. In some systems, such as the polymerizations of styrene and methacrylonitrile by potassium, the initiation is due to amide ion formed in the system [Overberger et al., I960]. Such polymerizations are analogous to those initiated by alkali amides. Polymerization in other systems cannot be due to amide ion. Thus, polymerization of methacrylonitrile by lithium in liquid ammonia proceeds at a much faster rate than that initiated by lithium amide in liquid ammonia [Overberger et al., 1959]. The mechanism of polymerization is considered to involve the formation of a solvated electron ... 

Mono-metallation of most simple acetylenic compounds in organic solvents can be accomplished without complications. The same holds for reactions of RCsCH with alkali amides in liquid ammonia. However, HCsCSiR3 and HC=CSnR3 cannot be metallated in this way, because the bonds between C and Si and between C and Sn are cleaved. HCsCSeR and HC=CPR2 disproportionate into HCsCH and RSeCsCSeR or R2PCsCPR2, respectively, under the influence of alkali amides [40,102],... 

In liquid ammonia with alkali amides, or in Et20 or THF with lithium dialkylamides, these complications do not occur, because these bases are considerably weaker than BuLi. 

This process can be avoided if the solution of BuLi is cautiously added to a small excess of. vinylacetylene. Alkali amides or lithium dialkylamides do not cause such an oligomerization. 

Treatment of "skipped" enynes H CCH2CH=CHR with alkali amides presumably will lead to extensive isomerization into C>CCH=CHCH2R. With alkyllithium bases inverse addition has to be applied to avoid dimetallation. This isomerization reaction is likely to be even more serious in the case of the diynes HC=CCH2OCR, since the CH2-protons have kinetic acidities comparable with that of the ethynyl proton. 

For some syntheses the presence of an excess of dissolved acetylene in the ammonia is undesirable in these cases, the addition of metal and introduction of acetylene in the last stage of the preparation, are carried out in a vety controlled way. The best guarantee for the absence of free acetylene is a (faint) uniformly blue solution at the end. Solutions of alkali acetylide prepared from alkali amide and acetylene may contain appreciable amounts of acetylene. 

Frothing can be effectively suppressed by cooling the suspension of alkali amide to a temperature just below the b.p. (-33 C) of ammonia (dry ice/acetone bath). 

All acetylenes with a terminal triple bond are instantaneously converted into the alkali acetylides by alkali amides in liquid ammonia. For many alkylations with primary alkyl halides liquid ammonia is the solvent of choice and the functionalization with oxirane can also be carried out in it with good results. Reactions of ROOM with sulfenyladng agents (R SSR1, R SON, R SSC R ) or elemental sulfur, selenium or tellurium are mostly very successful in ammonia, the same holds for the preparation of ROC1 from RC=CM and iodine. The results of couplings with carbonyl compounds are very variable. 

For the deprotonation of R3S1CECH, R SnCsCH, R2PCSCH, and RSeCsCH, the alkali amide-ammonia combination is unsuitable because of the easy cleavage of tbe heteroatom-C bond, which in the last two cases leads to the formation of R2POCPR2 and... 

Interaction between "skipped" enynes or diynes (RCH CHCT OCH or ROC--CH2C3CH) and alkali amides will lead to partial or complete isomerization (into RCH2CH=CHChCM or RCH=C=CHC=CM). Alkali amides in ammonia are unsuitable reagents if the compounds RSCT C IH and PhCH2C=CH are to be terminally mctallated (isomerization to RSCH=C=CH2 and PhCH OCHj). 

In contrast to the metallation with alkyllithium or alkali amides, Grignardation of HOCR with alkylmagnesium halide is not an instantaneous reaction. The more acidic 1,3-diynes and hetero-subsdtuled acetylenes react most readily. In the other cases heating for several minutes... 

Homologues of ethoxyacetylene can be obtained by reaction of the metallated ethynyl ether in liquid ammonia with primary alkyl bromides and iodides 167]. Because of their better solubiliiy, the lithium compounds are preferred over their sodium and potassium analogues, lithium ethoxyacetylide is generated from the readily accessible 2-bromovinyl ethyl ether and two equivalents of lithium amide. This starting compound is obtained as a mixture of the E-and Z-isomer. When this mixture is heated with powdered KOH, only the Z-isomer is converted into ethoxyethyne. Alkali amides are able to conven both isomers into ethoxyethyne and its alkali compounds. A possible explanation for this violation of the "rule of... 

In the preparation of 1-pentyne and 1-hexyne (exp. 10) complete conversion of the alkyl bromides is effected by using an excess of sodium acetylide. A reasoning based on economics prompts the use of an excess of the alkyl halide if alkali vinylacetylide or alkali diacetylide (generated from alkali amide and dichlorobutene or dichlorobutyne, respectively) are to be alkylated. If slightly mare than the stoichiometiical amount of alkyl bromide is used, no serious separation problems will be encountered during the final distillation. A relatively small amount of DMSO is added to enhance the solubility of the alkyl bromides, thereby facilitating the alkylation reaction. 

For enyne ethers HC=CCH=CHOR, the 1,4-elimination with alkali amides is a very attractive method because the starting compounds ROCH2CsCCH2OR can be readily prepared from the commercially available butynediol... 

Strong bases readily eliminate thiol from vinylic sulfides. 1,2-Bis(alkyl- or arylthio)ethynes for example, react with two equivalents of BuLi or alkali amide to give metallated alkyl- or arylthioacetylenes and thiolates [24] ... 

Many 1-alkynes can be prepared in high yields by adding bromine to 1-alkenes and subsequently treating the adduct with three equivalents of alkali amide in liquid ammonia the 1-alkyne is liberated (after removal of the ammonia) by addition of water. 

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