3.7- dimethyl-10-ethyl lithium

Lithium, methyl, 55,7, 10 Lithium, phenyl-, 55,11 Lithium phenylthio(alkyl)cuprates, 55,122 LITHIUM, phenyltluo(fe/f-butyl)cuprate [Lithium, phenylthio( 1,1 -dimethyl-ethyl)cupiate, 55,122 Lithium, 1-propenyl-, 55, 111 LITHIUM, ( >l-propenyl-, 55, 103 Lithium thiophenoxide [Ben7enethiol, lithium salt], 55, 122... 

SCHEME 76. Regio- and stereoselective protonation of the lithium anion generated by 1,6-catalyzed addition of methyllithium onto (2R,6R)-6-methyl-(4, 4 dimethylpent-2 -yn)-yliden-2-(l,l-dimethyl-ethyl)-l,3-dioxan-4-one366... 

The Lewis acidity of organoaluminium compounds is the reason of their association. The association of alkylaluminium molecules and aluminium hydrides proceeds by way of electron-deficient bonds [143a], The associates of dimethylberyllium, dimethyl- and diethylmagnesium, methyl- and ethyl-lithium are of the same type each alkyl group is simultaneously bound to two or three metal atoms [143b],... 

Of 18 proton sources used with the lithium enolate of methyl 4-tert-butylcyclohexanecar-boxylate, water yields a product ratio cis/trans close to that at equilibrium which highly favors the tram-isomer. However, such different proton sources as butanol and dimethyl ethyl-malonate preferentially attack the enolate from the less hindered side producing a ca. 72 28 ratio of cis/trans-isomers, the highest obtained in that investigation55 68,95. 

Amylopectins. — The effects of acrylamide graft copolymerization on the solution properties of amylopectin have been discussed. Amylopectin has been dyed with DyAmyl-L and used in this form as a substrate for the assay of a-amylase. Amylopectin has been treated with isocyanate derivatives of 4-amino-( 1,1-dimethyl ethyl)-3-(methylthio)-l,2,4-triazin-5(4/f)-one ( metribuzin ) or acid chloride derivatives of 2,4-dichlorophenoxyacetic acid ( 2,4-D ) and 2,2-dichloropropionic acid ( dalapon ), to produce controlled-release polymeric pesticide systems. The solvent system utilized for these reactions, a lithium chloride or bromide salt in AW-dimethylacetamide, allows dissolution of the reactant salt and facilitates analysis of the polymer product by such techniques as i.r., U.V., and n.m.r. spectroscopies and gel permeation chromatography. Derivatives of other naturally occurring polysaccharides, including amylopectin, cellulose, chitin, and dextran, were also prepared. 

The same names are used in organic as in inorganic chemistry e.gf.,phenylsodium, ethyl-lithium, dimethyl-mercury not sodium phenyl, lithium ethyl, or mercury dimethyl) methylmercuric bromide chloromercuri-benzoic acid (ClHg C6H4 C02H). lUPAC rules to cover wide areas of this extensive field are in an advanced stage of preparation at the time this book goes to press. 

The leaving group in the alkylating reagent has a major effect on whether C- or O-alkylation occurs. In the case of the lithium enolate of acetophenone, for example, C-alkylation is predominant with methyl iodide, but C- and O-alkylation occur to approximately equal extents with dimethyl sulfate. The C- versus O-alkylation ratio has also been studied for the potassium salt of ethyl acetoacetate as a function of both solvent and leaving group. ... 

In the case of 1,3-diphenylisoindole (29), Diels-Alder addition with maleic anhydride is readily reversible, and the position of equilibrium is found to be markedly dependent on the solvent. In ether, for example, the expected adduet (117) is formed in 72% yield, whereas in aeetonitrile solution the adduet is almost completely dissociated to its components. Similarly, the addition product (118) of maleic anhydride and l,3-diphenyl-2-methjdi.soindole is found to be completely dissociated on warming in methanol. The Diels-Alder products (119 and 120) formed by the addition of dimethyl acetylene-dicarboxylate and benzyne respectively to 1,3-diphcnylisoindole, show no tendency to revert to starting materials. An attempt to extrude carbethoxynitrene by thermal and photochemical methods from (121), prepared from the adduct (120) by treatment with butyl-lithium followed by ethyl chloroform ate, was unsuccessful. 

The lithium alkoxyenolatcs derived from ( + )-ethyl (S)-3-hydroxybutanoate and (-)-dimethyl (S)-2-hydroxybutanedioate, respectively, undergo addition to nitroethene with good diastereose-lection28. 

Potassium or lithium derivatives of ethyl acetate, dimethyl acetamide, acetonitrile, acetophenone, pinacolone and (trimethylsilyl)acetylene are known to undergo conjugate addition to 3-(t-butyldimethylsiloxy)-1 -cyclohexenyl t-butyl sulfone 328. The resulting a-sulfonyl carbanions 329 can be trapped stereospecifically by electrophiles such as water and methyl iodide417. When the nucleophile was an sp3-hybridized primary anion (Nu = CH2Y), the resulting product was mainly 330, while in the reaction with (trimethylsilyl)acetylide anion the main product was 331. 

Halogenation of 106 with triphenylphosphine, iodine, and imidazole provided the iodo derivative 109. On treatment with lithium aluminum hydride, 109 was converted into two endocyclic alkenes, 110 and di-O-isopro-pylidenecyclohexanetetrol, in the ratio of 2 1. Oxidation of 110 with dimethyl sulfoxide - oxalyl chloride afforded the enone 111.1,4-Addition of ethyl 2-lithio-l,3-dithiane-2-carboxylate provided compound 112. Reduction of 112 with lithium aluminum hydride, and shortening of the side-chain, gave compound 113, which was converted into 114 by deprotection. ... 

A similar sequence starting with the acylation product (76) from metachlorophenylacetonitrile gives the halogenated tricyclic ketone 83. Condensation of that intermediate with ethyl bromoacetate in the presence of zinc (Reformatsky reaction) gives the hydroxyester 84. This product is then in turn dehydrated under acid conditions (85), saponified to the corresponding acid (86), and converted to the dimethyl-amide (87) by way of the acid chloride. The amide function is then reduced to the amine (88) with lithium aluminum hydride catalytic hydrogenation of the exocyclic double bond completes the synthesis of closiramine (89). This compound also exhibits antihistaminic activity. 

Presence of carbon dioxide in solutions of the hydride in dimethyl or bis(2-methoxy-ethyl) ether can cause a violent decomposition on warming the residue from evaporation. Presence of aluminium chloride tends to increase the vigour of decomposition to explosion. Lithium tetrahydroaluminate may behave similarly, but is generally more stable. 

R)-aluminum-lithium-BINOL complex (0.024 g, 0.04 mmol) was dissolved in toluene (0.4 ml), and to this solution was added dimethyl phosphite (0.044 g, 0.4 mmol) at room temperature the mixture was stirred for 30 min. Benzaldehyde (0.042 g, 0.4 mmol) was then added at -40°C. After having been stirred for 51 h at -40°C, the reaction mixture was treated with 1 N hydrochloric acid (1.0 ml) and extracted with ethyl acetate (3 x 10 ml). The combined organic extracts were washed with brine, dried over sodium sulfate, and concentrated under reduced pressure. The residue was purified by flash chromatography (silica, 20% acetone/hexane) to give the diethyl (S)-a-hydroxybenzylphosphonate (78 mg, 90%) with 85% enantiomeric excess as a colorless solid of mp 86 to 87°C. 

It was already noted that activated enynes bearing an acceptor substituent at the double bond react with organocuprates under 1,6-addition to provide functionalized allenes (see Section III.A)38. Interestingly, the preference of these reagents for triple bonds persists even when the distance between the acceptor group and the triple bond is increased by the introduction of further double bonds. For example, lithium dimethylcuprate attacked ethyl 8,8-dimethyl-2,4-nonadien-6-ynoate at the triple bond exclusively, and regioselective... 

Ethyl 3-oxoalkanoates when not commercially available can be prepared by the acylation of tert-butyl ethyl malonate with an appropriate acid chloride by way of the magnesium enolate derivative. Hydrolysis and decarboxylation in acid solution yields the desired 3-oxo esters [59]. 3-Keto esters can also be prepared in excellent yields either from 2-alkanone by condensation with ethyl chloroformate by means of lithium diisopropylamide (LDA) [60] or from ethyl hydrogen malonate and alkanoyl chloride usingbutyllithium [61]. Alternatively P-keto esters have also been prepared by the alcoholysis of 5-acylated Mel-drum s acid (2,2-dimethyl-l,3-dioxane-4,6-dione). The latter are prepared in almost quantitative yield by the condensation of Meldrum s acid either with an appropriate fatty acid in the presence of DCCI and DMAP [62] or with an acid chloride in the presence of pyridine [62] (Scheme 7). 

Similar results were achieved when benzene was reduced with alkali metals in anhydrous methylamine at temperatures of 26-100°. Best yields of cyclohexene (up to 77.4%) were obtained with lithium at 85° [396]. Ethylamine [397] and especially ethylenediamine are even better solvents [398]. Benzene was reduced to cyclohexene and a small amount of cyclohexane [397, 398] ethylbenzene treated with lithium in ethylamine at —78° gave 75% of 1-ethyl-cyclohexene whereas at 17° a mixture of 45% of 1-ethylcyclohexene and 55% of ethylcyclohexane was obtained [397], Xylenes m- and p-) yielded non-conjugated 2,5-dihydro derivatives, l,3-dimethyl-3,6-cyclohexadiene and 1,4-dimethyl-1,4-cyclohexadiene, respectively, on reduction with sodium in liquid ammonia in the presence of ethanol (in poor yields) [399]. Reduction of diphenyl with sodium or calcium in liquid ammonia at —70° afforded mainly 1-phenylcyclohexene [400] whereas with sodium in ammonia at 120-125° mainly phenylcyclohexane [393] was formed. 

Acetals of aldehydes are usually stable to lithium aluminum hydride but are reduced to ethers with alane prepared in situ from lithium aluminum hydride and aluminum chloride in ether. Butyraldehyde diethyl acetal gave 47% yield of butyl ethyl ether, and benzaldehyde dimethyl acetal and diethyl acetal afforded benzyl methyl ether and benzyl ethyl ether in 88% and 73% yields, respectively [792]. 

B. (2S, 3R)-2,4-Dimethyl-1,3-pentanediol3. To a stirred solution of (+)-2 (2.75 g, 5 mmol, 96 4 isomeric purity) in tetrahydrofuran (THF) (50 mL) is added lithium aluminum hydride (0.19 g, 5 mmol) at 0°C. The reaction mixture is stirred at room temperature for 1 hr and quenched by the careful addition of sodium sulfate decahydrate (5 g). The mixture is stirred vigorously for 30 min and filtered. The filtrate is concentrated, dissolved in 75 mL of a 1 1 mixture of hexane and dichloromethane. This solution is dried over sodium sulfate, filtered and concentrated under reduced pressure. Trituration of the resulting oil with hexane (50 ml) results in the precipitation of auxiliary alcohol 4 (1.6-1.8 g) which is recovered by filtration (Note 11). The residue is separated by chromatography over silica gel (40 g) (Note 2) with hexane and ethyl acetate (3 1-1 1) to afford additional 4 (0.2-0.4 g. Note 12) and 3 (0.60 g, 92%) (Notes 13, 14). 

The reaction of ethyl A-arylcarbamates 3 with l-bromo-3,3-dimethyl-2-buta-none or l-bromo-3-ethyl-3-methyl-2-pentanone 4 in the presence of lithium bis(trimethylsilyl)amide (LiHMDS) results in the one-step synthesis of 3-aryl-5-ferf-butyl-2(3/T)-oxazolones 7 in fair to good yields (Fig. 5.2 Table 5.1, Fig. 5.3). This method is efficient for the preparation of bulky 5-substimted-2(37f)-oxazo-lones. 

A solution of 20 mmol of a .s-3-(2-alkyl-l-oxoalkyl)-l, 5-dimethyl-4-phenyl-2-imidazolidinone 5 in 40 mL of dry THF is slowly added at 0 3C to a stirred suspension of lithium aluminum hydride in 30 mL of THF under argon. The mixture is stirred for 1 h, then the reaction is quenched by the cautious addition of methanol, followed by 2M aq hydrochloric acid. Extraction with ethyl acetate is followed by concentration under vacuum and flash chromatography (cyclohexane/ethyl acetate). For specific examples, see Table 12. 

Die Reduktion von N-(2-Dialkylamino-ethyl)- und N-(3-Dialkylamino-propyl)-succinimi-den mit Lithium-alanat liefert l-(2-Dialkylamino-ethyl)- bzw. 1 -(3-Dialkylamino-propyl)-pyrrolidine (s. Bd. XI/1, S. 586). Dagegen verlauft die Reduktion von N-(Ani-lino-methyl)-succinimiden mit Natrium-boranat in Dimethyl-sulfoxid unter C-N-Spal-tung und Bildung von N-Methyl-anilinen4 ... 

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