Lithium ethenyl-

The reaction of the enamines of cyclohexanones with a,ft-unsaluraled sulfones gives mixtures resulting from attack of the enamine at the a- and /(-carbons of the oc,/ -unsaturated sulfone. The ratio of x- and /1-adducts is dependent upon the reaction solvent, the geometry and structure of the sulfone1 4. The diastereoselectivity of these reactions is also poor. The reaction of lithium enolates of cyclic ketones with ( )-[2-(methylsulfonyl)ethenyl]benzene, however, gives bicyclic alcohols, as single diastereomers, that result from initial -attack on the oc,/ -unsaturated sulfone5. 

The question of configurational stability has been investigated first for vinylidene carbenoids and, more recently, for alkylcarbenoids. Vinyl anions are usually considered to be configurationally stable" ° the calculated inversion barrier of the ethenyl anion 10 (R = H) is about 35 kcal mol (equation 4)" . Concerning lithioalkenes, this configurational stability has been confirmed experimentally for a-hydrogen, a-alkyl and a-aryl substituted derivatives . The inversion of vinylidene lithium carbenoids was already... 

S)-Pinanediol boronic esters 2 with (dichloromethyl)lithium produce (aS)-a-chloro boronic esters 3. The first experiments provided diastereomerie ratios in the range 75 25 to 98 2. The best results (>94 6) were obtained with phenyl, ethenyl, or 1-phenylethyl attached to the boron atom39 40. The diastereomerie ratios were estimated from the rotations of esters of derived secondary alcohols. It was subsequently found that zinc chloride catalysis of the rearrangement of the intermediate borate complexes 2 improved the yields, usually to 85-95%, with diastereo-meric ratios often >99 1 when R1 = alkyl, as shown by NMR measurements15,43. 

Anstclle der Amine + Katalysator konnen anch die gesondert hergestellten Lithium-amide eingesetzt werden, so z.B. bei der Oberfiihrung von Ethenyl- und Allyl-phosphanen in (2-Amino-alkyl)-phos-phane in siedendem Toluol (maBige bis gute Ausbeuten)7. 

Auch die Alkalimetalle selbst konnen als Katalysator eingesetzt werden8,9 (s.a. oben Herstellung von l-Ethyl-piperidin) sie bilden mit dem Amin das katalytisch wirksame Alkalimetall-amid. So hat sich fur die Addition von Diethylamin an 4-Ethenyl-4-methyl-benzol zu l-(2-Diethylamino-ethyl)-4-methyl-benzol die Verwendung von Lithium (14mol%) als geeignet erwiesen8. 

Bei einer anderen Zweistufen-Variante der Schweizer-Reaktion werden die aus prima-ren Aminen und Ethenyl-triphenyl-phosphonium-bromid erhaltlichen (2-Alkylamino-ethyl)-triphenyl-phosphonium-bromide nach Lithiierung mit 2-Aquivalenten Butyl-lithium in einer Carbonyl-Olefinierungsreaktion mit Aldehyden zu 1-Alkylamino-2-al-kenen umgesetzt2. Es entstehen uberwiegend die ( )-Isomeren. 

Vinyl acetate- Acetic acid vinyl ester Acetic acid ethenyl ester, (108-05-4), 65, 135 VINYL CATION EQUIVALENT, 66, 95 Vinyl cation synthons, 66, 102 Vinyl radical cyclization, 66, 81, 82 VINYLAT10N OF EN0LATES. 66, 95, 104 Vinyl lithium, 66, 53, 55... 

The reactions of poly(styryl)lithium in benzene with an excess of diphenyl-ethylene 272) and bis[4-(l-phenylethenyl)phenyl]ether158) also were found to proceed by a first order process. However, the reactions of poly(styryl)lithium with the double diphenylethylenes l,4-bis(l-phenylethenyl)benzene and 4,4 bis(l-phenyl-ethenyl)l,l biphenyl gave l58) non-linear first order plots with the gradients decreasing with time. This curvature was attributed to departure from a geometric mean relationship between the three dimerization equilibrium constants (Ka, Kb and Kab). The respective concentrations of the various unassociated, self-associated and cross-associated aggregates involved in the systems described by Equations (49) to (51) are dependent upon the relative concentrations of the two active centers and the respective rate constants which govern the association-dissociation events. 

A related approach exploited a A-cyanomethyl group to serve in the dual role of a nitrogen protecting group and a latent precursor of the formaldehyde im-inium ion (e.g., 478), and this innovative modification in tactics resulted in a simplified route to the c/.v-3a-aryloctahydroindole 474 (203a,c). To this end, the amino ketone 482 was readily prepared in one step by the reaction of 1,2-bis(trimethylsilyloxy)cyclopentene with A -benzyl-A -cyanomethyl amine. When 482 was exposed to [l-(3,4-methylenedioxyphenyl)ethenyl]lithium, a mixture (1 14) of 483 and 484 was obtained. It is noteworthy that the stereochemical sense... 

Upon treatment with lithium triethylborohydride in tetrahydrofuran, 2-benzoyl-l-ethenyl tellurium trichlorides produced did not produce the expected ditellurium compounds but bis[2-benzoylethenyl] telluriums2. 

Bis[2-benzoyl-l-ethenyl] Tellurium1 To a solution of 0.239 g (1.0 mmol) of 2-benzoylethenyl tellurium trichloride in 5 ml tetrahydrofuran are added via syringe 1.10 m/ of a 1 molar solution of lithium tricthylborohydride (1.1 mmol) in tetrahydrofuran. The mixture is stirred for 2h at 20 and then concentrated. The residue is chromatographed on silica gel. 

The proton on the ethenyl-CH group in ethenyl phenyl tellurium is replaced by lithium upon treatment with lithium dialkylamides in THF or diethyl ether at temperatures between — 20° and — 70". The 1-lithio-l-ethenyl phenyl tellurium reacted with deuterium oxide, benzaldehyde, and diphenyl ketone as expected1. 

Alkyl but-3-en-l-yn-l-yl tellurium and lithium in liquid ammonia form lithium al-kanetellurolates. The tellurium-ethenyl bond is broken in this reaction1. 

Aryl tellurium halides react with aliphatic and aromatic Grignard reagents, with ethenyl magnesium halides , with ethynyl magnesium bromide with dimethyl and diethyl cadmium , with 2-(diphenylphosphino)-phenyl lithium, and with phenyl mercury chloride to produce aryl organo telluriums (p. 416). 

Alkyl but-3-en-l-yn-l-yl tellurium and lithium in liquid ammonia form lithium al-kanetellurolates. The tellurium-ethenyl bond is broken in this reactionh When 1-adamantyl phenyl tellurium was treated with sodium in liquid ammonia, the Te-adamantyl bond is preferentially cleaved, although the Te-phenyl bond is also attacked. The ratio of the fragmentation rates is approximately 13. ... 

The spiro bis-Cp-amido complex Ti[CsH4C(=CH2)N(SiMe3)]2 (Scheme 587) has been isolated in 81% yield by treatment of lithium [l-(lithio-N-trimethylsilylamido)ethenyl]cyclopentadienide with TiCl4(THF)2.983... 

On treatment with n-BuLi, 2-(trimethylsilyl)-4-[(2,2-dibromo)ethenyl]furan undergoes a Fritsch-Buttenberg-Wiechell rearrangement to provide the lithium acetylide, which reacts with... 

Organo-lithium-Verbindung) 2-(2,2-Bis-[4-dimethylamino-phenyl]-I-fluor-ethenyl)-.., 581... 

ETHENYL-4-METHOXYCYCLOBUTENE-l,2-DIONE. This procedure also provides a convenient method for the preparation of DIMETHYL SQUARATE, an important intermediate. The synthesis of (lR, 6S, 7S )-4-(tert-BUTYLDIMETHYLSILOXY)-6-(TRIMETHYLSILYL)BICYCLO-[5.4.0JUNDEC-4-EN-2-ONE is representative of a general protocol for the construction of cycloheptenones by a [3 + 4] annulation. The method features the addition of a lithium enolate to an acryloyl silane to give a 1,2-adduct that undergoes a novel sequence of a concerted Brook rearrange-ment/cyclopropanation and an anionic oxy-Cope rearrangement. 

---