Selective syntheses with organometallics. 7. (Z)-2-Ethoxyvinyllithium: a remarkably stable and synthetically useful 1,2-counterpolarized species

Lau, Kreisler S.Y.; Schlosser, Manfred

doi:10.1021/jo00402a028

Cited by 96 publications

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“…The most straightforward route to b-ionylideneacetaldehyde (again obtained as a mixture of geometrical isomers [3] ) is based on the addition of (Z)-2-ethoxyvinyllithium [4] to bionone and the subsequent hydrolysis of the resulting (Z)-2-ethoxyvinyl-b-ionol under acidic conditions. However, from an economic point of view, it would be attractive to avoid the expensive organometallic reagent and to apply a two-step Scheme 1.…”

Section: Introductionmentioning

confidence: 99%

A Novel Aldol Condensation Alternative:α,β-Unsaturated Aldehydes from 3-Hydroxy-1-alkynes via Dihydrodioxepins

Wei

Schlosser

1998

Chem. Eur. J.

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The controlled aldol condensation between an aliphatic ketone and an acetaldehyde equivalent remains a challenge. One solution to this evergreen problem consists of the nucleophilic addition of acetylene to the ketone and the subsequent isomerization of the resulting 3-hydroxy-1-alkyne to the corresponding 2-alkenal. So far, however, the latter step could only be executed with acid-insensitive substrates. We now present a milder, three-step method which extends the scope of the procedure considerably. In the first step, the 3-hydroxy-1-alkynes are converted into 2-propynyl ethylene glycol monoethers; these then undergo base-catalyzed cyclization to give the dihydro-1,4-dioxepins, which are hydrolyzed in acidic medium in the third and final step.

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Section: Introductionmentioning

confidence: 99%

A Novel Aldol Condensation Alternative:α,β-Unsaturated Aldehydes from 3-Hydroxy-1-alkynes via Dihydrodioxepins

Wei

Schlosser

1998

Chem. Eur. J.

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“…a,P-Unsaturated aldehydes are important in synthetic organic chemistry (18) and previous preparations include: (i) from ketones by one-carbon homologation procedures (19,20); (ii) from methyl vinyl ethers by photooxidation (18); (iii) from aldehydes via organolithium derivatives (20,(22)(23)(24) or by oxidation via a-chloroaldimines (1 8); (iv) from a-bromoaldehydes via N, N-dimethylhydrazones (25) or piperidine enarnines (26); (v) from a-lithiated allenic sulfides (27); and (vi) a single example (for l-cyclohexenecarboxaldehyde) from a nitromethylolefin (28).…”

Section: Resultsmentioning

confidence: 99%

Reactions of unactivated olefins with Vilsmeier reagents

Katritzky¹,

Щербакова²,

Tack³

et al. 1992

Can. J. Chem.

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Reactions of N-f0rmylmorpholine/POC1~ with several unactivated olefins yield the corresponding a,P-unsaturated aldehydes. Norbornene affords with dimethylformamide/POC13 a product formed by a novel inverse-electron demand Diels-Alder reaction of an acyclic 2-azoniodiene. The structure ofthis product was confirmed by X-ray analysis. Crystals are monoclinic: a = 8.025(3), b = 11.670(3), c = 9.309(4) A, P = 108.03(3)", P2,,Z = 2; the structure was refined to R = 0.044 for 1379 independent observed reflections. Les reactions du couple N-formylmorpholine/POC13 avec plusieurs olefines inactives foumit les aldehydes a,p-insaturks correspondants. Le norbornbne qui rkagit avec le couple dimCthylformamide/POC13 par une nouvelle reaction de Diels-Alder comportant une demande inverse d'electrons fournit un 2-azoniodibne acyclique dont on a dktermink la structure par diffraction des rayons-X. Les cristaux sont monocliniques, groupe d'espace P 2 , , avec a = 8,025(3), b = 11,670(3) et c = 9,309(4) A, P = 108,03(3)" et Z = 2; on a affine la structure jusqu'h une valeur de R = 0,044 pour 1379 reflexions independantes observees.[Traduit par la redaction]

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“…Vinyl halides containing vinylic protons can undergo either halogen-metal exchange or hydrogen-metal exchange when treated with an alkyllithium compound [317,[325][326][327]. Scheme 5.…”

Section: Vinylic Carbanionsmentioning

confidence: 99%

“…Alkenes which can be metalated and trapped with electrophiles, and preferred sites of vinylic deprotonation [317,326,[328][329][330][331][332]. Alkenes which can be metalated and trapped with electrophiles, and preferred sites of vinylic deprotonation [317,326,[328][329][330][331][332].…”

Section: Vinylic Carbanionsmentioning

confidence: 99%

The Alkylation of Carbanions

Dörwald

2004

Side Reactions in Organic Synthesis

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The deprotonation of organic compounds by strong, non-nucleophilic bases followed by C-alkylation with a suitable electrophile has become one of the most predictable and straightforward methods for formation of C-C bonds. The popularity of this chemistry is also a consequence of the often-seen close resemblance of feasible structural modifications by a deprotonation/alkylation strategy to an unsophisticated retrosynthetic analysis of a given target compound. Other reactions, which involve, for instance, substantial rearrangement of the carbon framework (e.g. Cope rearrangement, fragmentations, ring contractions or enlargements) are usually more difficult to take into account during retrosynthetic analysis.LDA and related, sterically hindered, lithium dialkylamides, first investigated by Levine [1], have completely replaced the more nucleophilic sodium amide, which had been the base of choice for many years [2]. Because the reactivity of an organometallic compound depends to a large extent on its state of aggregation (i.e. on the solvent and on additives) and on the metal, transmetalation of the lithiated intermediates and the choice of different solvents and additives emerged as powerful strategies for fine-tuning the reactivity of these valuable nucleophiles.In this chapter the alkylation of carbanions with simple carbon electrophiles will be discussed, with special emphasis on the structure-reactivity relationship of the carbanion and on side reactions. In this context the term "carbanion" refers to an intermediate prepared by in-situ deprotonation of an organic compound, followed by optional cation exchange (transmetalation), which tends to be alkylated at carbon by soft electrophiles such as MeI or PhCHO. This type of reactivity is characteristic of enolates with an ionic M-O bond or for organometallic compounds with a strongly polarized or ionic M-C bond, M typically being an alkali metal, Mg, Cu, or Zn. Carbanions can, alternatively, also be prepared by halogen-metal exchange [3-8], sulfoxide-or sulfone-metal exchange [9-13], or by transmetalation of stannanes. The most suitable reagents for performing such metalating exchange reactions are organometallic compounds with a metal-bound secondary or tertiary alkyl group, such as tBuLi, sBuLi, iPr 2 Zn [14, 15], or iPrMgHal [6]. These reagents are thermodynamically less stable than organometallic compounds with primary alkyl 5 146 Scheme 5.1. Approximate relative rates of proton transfer in water at thermoneutrality (DpK a = 0) [35, 39, 51]. 147 Scheme 5.2. The effect of fluorine on the acidity of organic compounds [24, 62-65]. 148 Scheme 5.3. Dependence of the reactivity of carbanions on their basicity [68, 72-74]. Regioselectivity of Deprotonations and AlkylationsThe organic chemist is occasionally confronted with the problem that a compound has several differrent X-H groups of similar pK a . If only one of these is to be alkylated, one option would be to perform a regioselective deprotonation. This can sometimes be achieved by exploiting small differences be...

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Selective syntheses with organometallics. 7. (Z)-2-Ethoxyvinyllithium: a remarkably stable and synthetically useful 1,2-counterpolarized species

Abstract: Der (Z)‐ Brom‐vinylether (I) reagiert mit Butyllithium unter Halogen‐Li‐Austausch zu (II), das mit Ketonen zu Addukten (III) führt und zu (IV) substituiert werden kann.

Cited by 96 publications

References 0 publications

A Novel Aldol Condensation Alternative:α,β-Unsaturated Aldehydes from 3-Hydroxy-1-alkynes via Dihydrodioxepins

A Novel Aldol Condensation Alternative:α,β-Unsaturated Aldehydes from 3-Hydroxy-1-alkynes via Dihydrodioxepins

Reactions of unactivated olefins with Vilsmeier reagents

The Alkylation of Carbanions

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