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Lithium alkenes

It is clear from these experiments that the presence of ethylene catalyses the fixation of nitrogen in lithium complexes. This assisted complexation was also observed with methyl-substituted ethylene and butadiene. It is a characteristic property of lithium-alkene complexes, as experiments performed with other lithium complexes have so far not yielded such ternary complexes. If one can easily anticipate that the fractional positive charge on the lithium in LiC2H4 and Li(C2H4)2 facilitates the coordination of N2 with, presumably, a a-donation to lithium, and possibly, to a weaker extent, p-donation from the metal, it is difficult to rationalize why LiC2H2 and LiC2H4 behave so differently with respect to nitrogen, for instance. [Pg.243]

Halo-1-lithium alkenes react with chlorotrimethylsilane in TMF/HMPT to form 1-halo-l-trimethylsilyl alkenes (Eq.3.31) ... [Pg.28]

The 2-alken-4-ynylamine analogues (A. Stiitz, 1987) are best synthesized by Grignard-type additions of lithium acetylides to propenal and either... [Pg.303]

There are a wide variety of methods for introduction of substituents at C3. Since this is the preferred site for electrophilic substitution, direct alkylation and acylation procedures are often effective. Even mild electrophiles such as alkenes with EW substituents can react at the 3-position of the indole ring. Techniques for preparation of 3-lithioindoles, usually by halogen-metal exchange, have been developed and this provides access not only to the lithium reagents but also to other organometallic reagents derived from them. The 3-position is also reactive toward electrophilic mercuration. [Pg.105]

A useful alternative to catalytic partial hydrogenation for converting alkynes to alkenes IS reduction by a Group I metal (lithium sodium or potassium) m liquid ammonia The unique feature of metal-ammonia reduction is that it converts alkynes to trans alkenes whereas catalytic hydrogenation yields cis alkenes Thus from the same alkyne one can prepare either a cis or a trans alkene by choosing the appropriate reaction conditions... [Pg.376]

Epoxidation of an alkene followed by lithium aluminum hydride reduction of the result mg epoxide gives the same alcohol that would be obtained by acid catalyzed hydration (Section 610) of the alkene... [Pg.681]

Ca.ta.lysts, A small amount of quinoline promotes the formation of rigid foams (qv) from diols and unsaturated dicarboxyhc acids (100). Acrolein and methacrolein 1,4-addition polymerisation is catalysed by lithium complexes of quinoline (101). Organic bases, including quinoline, promote the dehydrogenation of unbranched alkanes to unbranched alkenes using platinum on sodium mordenite (102). The peracetic acid epoxidation of a wide range of alkenes is catalysed by 8-hydroxyquinoline (103). Hydroformylation catalysts have been improved using 2-quinolone [59-31-4] (104) (see Catalysis). [Pg.394]

Vinyllithium [917-57-7] can be formed direcdy from vinyl chloride by means of a lithium [7439-93-2] dispersion containing 2 wt % sodium [7440-23-5] at 0—10°C. This compound is a reactive intermediate for the formation of vinyl alcohols from aldehydes, vinyl ketones from organic acids, vinyl sulfides from disulfides, and monosubstituted alkenes from organic halides. It can also be converted to vinylcopper [37616-22-1] or divinylcopper lithium [22903-99-7], which can then be used to introduce a vinyl group stereoselectively into a variety of a, P-unsaturated systems (26), or simply add a vinyl group to other a, P-unsaturated compounds to give y, 5-unsaturated compounds. Vinyllithium reagents can also be converted to secondary alcohols with trialkylb o r ane s. [Pg.414]

Lithium aluminum hydride normally reacts with thiiranes via nucleophilic attack on carbon, but where that process is hindered sulfur is attacked to give the alkene, usually in good yield, and lithium sulfide (70JPR421). [Pg.155]

This procedure illustrates a general method for the preparation of alkenes from the pal 1 adium(Q)-cata1yzed reaction of vinyl halides with organo-lithium compounds, which can be prepared by various methods, including direct regioselective lithiation of hydrocarbons. The method is simple and has been used to prepare a variety of alkenes stereoselectively. Similar stoichiometric organocopper reactions sometimes proceed in a nonstereoselective... [Pg.45]

Seven procedures descnbe preparation of important synthesis intermediates A two-step procedure gives 2-(HYDROXYMETHYL)ALLYLTRIMETH-YLSILANE, a versatile bifunctional reagent As the acetate, it can be converted to a tnmethylenemethane-palladium complex (in situ) which undergoes [3 -(- 2] annulation reactions with electron-deficient alkenes A preparation of halide-free METHYLLITHIUM is included because the presence of lithium halide in the reagent sometimes complicates the analysis and use of methyllithium Commercial samples invariably contain a full molar equivalent of bromide or iodide AZLLENE IS a fundamental compound in organic chemistry, the preparation... [Pg.224]

The pyrolysis of sodium chlorodinuoroacetate is still a widely used, classical method for generating difluorocarbene, especially with enol and allyl acetates [48, 49, 50, 51] (equation 21) A convenient alternative that avoids the hygroscopic salt uses methyl chlorodifluoroacetate with 2 equivalents of a lithium chlonde-hexa-methylphosphoric triamide complex at 75-80 °C in triglyme [52], Yields are excellent with electron-rich olefins but are less satisfactory with moderately nucleophilic alkenes (4-5% yields for 2-bulenes)... [Pg.771]

Simultaneous elimination of chloride ion and carbon dioxide occurs dunng heating of methyl chlorodifluoroacetate with lithium chloride in hexamethyl-phosphoric tnamide (HMPA) The difluorocarbene generated in this way is trapped by electron-rich alkenes to form 1,1-difluorocyclopropanes [26] (equation 24)... [Pg.894]

Examine the eleetrostatic potential map of eaeh nueleophile (enamine, silyl enol ether, lithium enolate and enol) with emphasis on the face of the nucleophilic alkene carbon. Rank the nucleophiles from most electron rich to least electron rich. What factors are responsible for this order (Hint For each molecule, consider an alternative Lewis structure to that given above that places a negative charge on the nucleophilic carbon.)... [Pg.166]

Reaction of 2-chloromethyl-4//-pyrido[l,2-u]pyrimidine-4-one 162 with various nitronate anions (4 equiv) under phase-transfer conditions with BU4NOH in H2O and CH2CI2 under photo-stimulation gave 2-ethylenic derivatives 164 (01H(55)535). These alkenes 164 were formed by single electron transfer C-alkylation and base-promoted HNO2 elimination from 163. When the ethylenic derivative 164 (R = R ) was unsymmetrical, only the E isomer was isolated. Compound 162 was treated with S-nucleophiles (sodium salt of benzyl mercaptan and benzenesulfinic acid) and the lithium salt of 4-hydroxycoumarin to give compounds 165-167, respectively. [Pg.210]

A more promising procedure for the formation of alkenes from tosylhydrazones is represented by the Shapiro reaction It differs from the Bamford-Stevens reaction by the use of an organolithium compound (e.g. methyl lithium) as a strongly basic reagent ... [Pg.24]

An alternative method for the conversion of an alkyne to an alkene uses sodium or lithium metal as the reducing agent in liquid ammonia as solvent. This method is complementary to the Lindlar reduction because it produces... [Pg.268]

Mechanism of the lithium/ ammonia reduction of an alkyne to produce a trans alkene. [Pg.269]

The product i n this case is a cis-disubstituted alkene, so the fi rst question is, " What is an immediate precursor of a cis-disubstituted alkene " We know that an alkene can be prepared from an alkyne by reduction and that the right choice of experimental conditions will allow us to prepare either a trans-disubstituted alkene (using lithium in liquid ammonia) ora cis-disubstituted alkene (using catalytic hydrogenation over the Lindlar catalyst). Thus, reduction of 2-hexyne by catalytic hydrogenation using the Lindlar catalyst should yield cis-2-hexene. [Pg.275]

Alkynes can be reduced to yield alkenes and alkanes. Complete reduction of the triple bond over a palladium hydrogenation catalyst yields an alkane partial reduction by catalytic hydrogenation over a Lindlar catalyst yields a cis alkene. Reduction of (he alkyne with lithium in ammonia yields a trans alkene. [Pg.279]

It was demonstrated that when a better leaving group than lithium oxide (Li20) is present at the a-position (e. g., epoxide 125 Scheme 5.27), alkene formation occurs with retention of the alcohol moiety [44]. [Pg.159]

Deprotonation of alkenes by butyllithium in the presence of TMEDA affording, for example, 2-propenyllithium from propene14, (2-methyl-2-propenyl)lithium from 2-methylpropene31,... [Pg.233]

Racemic [l-(4-methylphenylsulfinyl)-2-propenyl]lithium, prepared with lithium diiso-propylamide in THF, adds to racemic chiral 2-methylalkanals with good a- and syn selectivity114, us Qn heating with trimethyl phosphite or triethylamine, the major isomer furnishes the ( )-.yvn-2-alkene-l,4-diol by Mislow rearrangement1 lb. [Pg.244]

The strict geometrical requirements for elimination can be put to further use, as illustrated by elegant procedures for the geometrical isomerization of alkenes. Trimethylsilyl potassium (10) and phenyldimethylsilyl lithium (11) both effect smooth conversion of oxiranes into alkenes, nucleophilic ring opening being followed by bond rotation and spontaneous syn fi-elimination ... [Pg.45]

These alkene isomers are separately available (4) by treatment of threo-S-trimethylsilyloctan-4-ol, prepared by reduction of the corresponding ketone with DIBAL in pentane at —120°C, with base or acid. The preparation of 5-trimethylsilyloctan-4-one itself illustrates three general procedures the addition of alkyl lithium reagents to vinylsilanes to generate a-lithiosilanes, the preparation of complex /5-hydroxysilanes, as diastereoisomeric mixtures, and the oxidation of such compounds to /8-ketosilanes... [Pg.127]

Ketosilanes react with alkyl lithiums in a diastereoselective manner (7), the preferred diastereoisomer being the one predicted on the basis of Cram s Rule acidic or basic treatment provides a stereoselective route to trisubstituted alkenes. [Pg.128]


See other pages where Lithium alkenes is mentioned: [Pg.772]    [Pg.772]    [Pg.772]    [Pg.772]    [Pg.242]    [Pg.141]    [Pg.587]    [Pg.308]    [Pg.311]    [Pg.525]    [Pg.133]    [Pg.113]    [Pg.153]    [Pg.154]    [Pg.155]    [Pg.225]    [Pg.587]    [Pg.103]    [Pg.269]    [Pg.155]    [Pg.157]    [Pg.325]    [Pg.1021]    [Pg.33]   
See also in sourсe #XX -- [ Pg.41 , Pg.178 ]




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1-Alkenes Lithium 2,2,6,6-tetramethylpiperidide

1-Alkenes Titanium chloride-Lithium aluminum hydride

Alkenes lithium metal

Lithium alkene complexes

Lithium derivatives from alkenes

Lithium reactions with alkenes

Lithium, a-selenobenzylreactions with alkenes

Lithium, a-selenobenzylreactions with alkenes reactivity

Lithium, phenyladdition reactions alkenes, palladium catalysis

Lithium-alkene interactions

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