Triethylamine-Lithium bromide

Triethylamine, 322, 328 Triethylamine-Lithium bromide, 322 Triethylamine-Magnesium bromide, 322... 

When 2,2-dimethylpropanal is used to prepare the azomethine moiety, the corresponding azaallyl anion may be obtained when l,8-diazabicyclo[5.4.0]undec-7-ene/lithium bromide is used as base. The subsequent addition to various enones or methyl ( )-2-butenoate proceeds with anti selectivity, presumably via a chelated enolate. However, no reaction occurs when triethylamine is used as the base, whereas lithium diisopropylamide as the base leads to the formation of a cycloadduct, e.g., dimethyl 5-isopropyl-3-methyl-2,4-pyrrolidinedicarboxylate using methyl ( )-2-butenoate as the enone84 89,384. 

Very recently examples of tandem Michael-azomethine ylide cyclization reactions have been presented.626 Thus, divinyl sulfone reacted with imine (124) in the presence of lithium bromide and tri-ethylamine to give (126) in 40% yield (Scheme 38). Presumably formation of Michael adduct (125), tau-tomerization to an azomethine ylide and ensuing intramolecular [3 + 2] cycloaddition afforded (126). Indeed, (125) could be independently synthesized and converted to (126) under the reaction conditions. The preference for initial Michael addition, rather than cycloaddition, was variable. When (124) and divinyl sulfone were treated with silver acetate and triethylamine in DMSO, intermolecular azomethine cycloaddition occurred giving (127) in 27% yield. 

A range of organic transformations promoted by lithium bromide and triethy-lamine under neat reaction conditions have been reported. As the reagents ben-zaldehyde and triethylamine are liquids, these reactions may not be entirely solvent free, just without an added solvent. The product distribution (or class of reaction) was affected by the solvent used in the reaction work up (Figure 2.14), and therefore a wide range of products can be obtained using a very simple approach. 

DEHYDROHALOGENATION Amidines, bicyclic. N-Bromosuccinimide. I, S-Dia-zabicyclo[4.3.0 nonene-5. Diethylamine. Dimethyl sulfoxide. Hexamethylphosphor-ic triamide. Lithium bromide. Potassium r-butoxkle. Sodium amidc-Sodium r-but-oxide. Tetia-n-butylammonium bromide. Triethylamine. 

In the presence of lithium bromide in THF the imines of a-amino esters can be deprotonated with triethylamine at room temperature to generate highly reactive 1,3-dipoles 141, which exist either in an N-lithiated azomethine... 

The N-metallated azomethine ylides having a wider synthetic potential are N-lithiated ylides 141, derived from the imines of a-amino esters, lithium bromide, and triethylamine, and 144 from the imines of a-aminonitriles and LDA (Section II,G). Ester-stabilized ylides 144 undergo regio- and endo-selective cycloadditions, at room temperature, to a wide variety of unsym-metrically substituted olefins bearing a carbonyl-activating substituent, such as methyl acrylate, crotonate, cinnamate, methacrylate, 3-buten-2-one, ( )-3-penten-2-one, ( )-4-phenyl-3-buten-2-one, and ( )-l-(p-tolyl)-3-phenyl-propenone, to give excellent yields of cycloadducts 142 (88JOC1384). 

Dehydrohalogenation Benzyltrimethylammonium mcsitoate. r-Butylamine. Calcium carbonate. j Uidine. Diazabicyclo[3.4.0]nonene-5. N.N-Dimethylaniline (see also Ethoxy-acetylene, preparation). N,N-Dimelhylformamide. Dimethyl sulfoxide-Potassium r-but-oxide. Dimethyl sulfoxide-Sodium bicarbonate. 2,4-Dinitrophenylhydrazine. Ethoxy-carbonylhydrazine. Ethyldicyclohexylamine. Ethyidiisopropylamine. Ion-exchange resins. Lithium. Lithium carbonate. Lithium carbonate-Lithium bromide. Lithium chloride. Methanolic KOH (see DimethylTormamide). N-PhenylmorphoKne. Potassium amide. Potassium r-butoxide. Pyridine. Quinoline. Rhodium-Alumina. Silver oxide. Sodium acetate-Acetonitrile (see Tetrachlorocyclopentadienone, preparation). Sodium amide. Sodium 2-butylcyclohexoxide. Sodium ethoxide (see l-Ethoxybutene-l-yne-3, preparation). Sodium hydride. Sodium iodide in 1,2-dimethoxyethane (see Tetrachlorocyclopentadienone, alternative preparation) Tetraethylammonium chloride. Tri-n-butylamine. Triethylamine. Tri-methyiamine (see Boron trichloride). Trimethyl phosphite. 

A screening experiment with different types of electrophilic additives showed that a promising procedure for future development was to treat methyl vinyl ketone (MVK) with chlorotrimethylsilane (TMSCl) in the presence of triethylamine (TEA) and lithium bromide in tetrahydrofuran. 

The synthesis of 2-trimethylsilyoxy-l,3-butadiene by treatment of methyl vinyl ketone with chlorotrimethylsilane, lithium bromide and triethylamine in tetrahydrofuran was discussed in section 12.5.6. It was discussed how the stoichiometry of the reaction was determined by canonical analysis of the response surface model, and how this analysis made it possible to establish experimental conditions which afforded a quantitative conversion. However, before the response surface model could be established it was necessary to find a reaction system worth optimizing. 

Triethylamine in THF can be used as the external base to deprotonate triazolium salts. The resulting NHCs were complexed in situ, e.g., to [(/7 -cymene)RuCl2]2, [(/ -cod)RhCl]2, and [(/ -C5Me5)RhCl2]2. Sodium carbonate in water/ DMSO deprotonates imidazolium iodides in the presence of mercury(II) dichloride to give [Hg(NHC)2][Hgl3Cl]. " A pyridine-functionalized imidazolium salt was deprotonated by lithium diisopropylamide (LDA) in THF and attached in situ to [(p -cod)Pd(Me)Br] [Eq.(17)]. After abstraction of the bromide anion with silver(I) a tetranuclear ring is formed. 

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