Lewis Acid Catalyzed Ene Reactions Research Articles

Synthesis of 3β-tert-Butyldimethylsiloxy-22-phenylthio-23,24-bisnorchola-5,9(11)-diene and Reductive Nucleophilic Attack on a Branched Aliphatic Aldehyde.

3β-tert-Butyldimethylsiloxy-22-phenylthio-23,24-bisnorchola-5,9(11)-diene, which has a double bond between C-9 and C-11 and a phenylsulfenyl group on the terminus of the side chain, is a potential synthetic intermediate for steroids with 9,11-unsaturation or 9,11-seco skeletons. We describe here the synthesis of the title compound from 17-ethylenedioxy-3-acetoxyandrosta-3,5-dien-11-one. The introduction of an ethylene unit to 3β-tert-butyldimethylsiloxyandrosta-5,9(11)-dien-17-one by the action of ethyltriphenylphosphonium bromide under basic conditions resulted in an inseparable mixture of two stereoisomeric products (5 : 1). However, in the subsequent step, only the (Z)-isomer was susceptible to the Lewis acid-catalyzed ene reaction with formaldehyde, giving a stereochemically pure product with the desired configuration. Within three steps, the ene-product was derivatized to the title compound, with a total yield of 53% over seven steps. Reductive terminal anion formation by treatment with lithium di-tert-butylbiphenyl (LiDBB) and subsequent nucleophilic attack on a branched aliphatic aldehyde was demonstrated, with an eye toward the introduction of side chains, especially for steroids with oxygen functionality at C-23.

ChemInform Abstract: Lewis Acid-Catalyzed Ene Reactions of Esters of 2- Trifluoromethylpropenoic Acid.

ChemInform Abstract: Lewis Acid-Catalyzed Ene Reactions of Esters of 2- Trifluoromethylpropenoic Acid.

13C and (2)H kinetic isotope effects and the mechanism of Lewis acid-catalyzed ene reactions of formaldehyde.

13C and (2)H kinetic isotope effects were determined for the ene reaction of formaldehyde with 2-methyl-2-butene at natural abundance catalyzed by diethylaluminum chloride. The reactive methyl group exhibits a k(12)(C)/k(13)(C) of 1.006-1.009 and a k(H)/k(D) of approximately 1.22-1.23. The latter represents a combination of primary and secondary effects and is consistent with a significant primary deuterium isotope effect. A very close correspondence of the other isotope effects with the equilibrium isotope effects predicted for formation of a model intermediate cation is observed. An intermolecular deuterium isotope effect of 2.0-2.5 was observed under several reaction conditions in the Lewis acid-catalyzed reaction of formaldehyde with d(0)/d(12)-tetramethylethylene. The results are interpreted as supporting the reversible formation of an essentially classical open cation followed by rate-limiting proton transfer.

The Total Synthesis of 8β-Hydroxycycloaraneosene by Means of an Eight-Membered Ring-Formation via a Lewis Acid-Catalyzed Ene Reaction. Confirmation of Its Natural Occurrence

Abstract An improved eight-membered ring closure by means of a Lewis-acid-catalyzed ene reaction was applied to the synthesis of cycloaraneosene and its congener, “hydroxycycloaraneosene.” Comparisons of the NMR spectral data of the synthetic and natural compounds established that the natural product possesses an 8β-hydroxy structure, not the originally proposed 9α-hydroxy one.

ChemInform Abstract: The Mechanism of Lewis Acid Catalyzed Ene Reactions.

AbstractIntermo1ecular[with (V) and (VI)] and intramolecular kinetic isotope effects [with (I), (VII), and (VIII)] establish that the Lewis acid catalyzed ene reactions of formaldehyde (II) [e.g.

Reductive metallation : A general preparative method for hydrocarbon allylmetallic compounds

Because of the great ease of preparation of allyl phenyl sulfides and their smooth reductive lithiation using lithium naphthalenide or 1-(dimethylamino)naphthalenide, these are ideal substrates for a particularly versatile preparative method for allylic anions. The lithio compounds react with aldehydes and ketones readily and with moderate regioselectivity. The allyltitanium compounds formed by addition of titanium tetraisopropoxide react with enals with very high regioselectivity and stereoselectivity. The allyltilanium compound derived from 2-phenylthio-1-methylenecyclohexane adds in a 1,2-fashion to crotonaldehyde at the secondary terminus of the allylic system. The potassium salt of this adduct undergoes the anion-accelerated oxy Cope rearrangement to the product of formal 1,4-addition of the crotonaldehyde to the primary terminus. The rearrangement product is an aldehyde which is also synthetically useful, undergoing the Lewis acid catalyzed ene reaction to produce a ring-closed product.

The mechanism of Lewis acid catalyzed ene reactions

The mechanism of Lewis acid catalyzed ene reactions

ChemInform Abstract: Synthesis of Protected Vinylic Amino Acids by Intermolecular Lewis Acid Catalyzed Ene Reactions.

AbstractDie durch FeCl3 katalysierte intermolekulare En‐Reaktion von (II) mit den Allylaminosäurederivaten (Ia)‐(Ie) führt zu E‐konfigurierten ungesättigten Pimelinsäureestern (III).

Syntheses of protected vinylic amino acids by intermolecular Lewis acid catalyzed ene reactions

Intermolecular ene reaction between ethylglyoxylate and allylic amino acid derivatives gave highly functionalized unsaturated pimelic acids in one step. This synthetic approach appears as a new efficient method for the synthesis of vinylic amino acids.

Intramolecular and intermolecular Lewis acid catalyzed ene reactions using ketones as enophiles

On applique la reaction ene aux alcenyl-2 cyclopentanones et cyclohexanones, catalysee par les halogenures d'alkylaluminium

Observations on the mechanism of the Lewis acid catalyzed ene reaction

Observations on the mechanism of the Lewis acid catalyzed ene reaction

Stereoselective and regioselective Lewis acid catalyzed ene reactions of .alpha.-substituted acrylate esters

Stereoselective and regioselective Lewis acid catalyzed ene reactions of .alpha.-substituted acrylate esters

Lewis acid catalyzed ene reactions of ethynyl p-tolyl sulfone

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLewis acid catalyzed ene reactions of ethynyl p-tolyl sulfoneBarry B. Snider, Thomas C. Kirk, David M. Roush, and Domingo GonzalezCite this: J. Org. Chem. 1980, 45, 25, 5015–5017Publication Date (Print):December 1, 1980Publication History Published online1 May 2002Published inissue 1 December 1980https://doi.org/10.1021/jo01313a001RIGHTS & PERMISSIONSArticle Views306Altmetric-Citations24LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (395 KB) Get e-Alerts Get e-Alerts

Lewis Acid Catalyzed Ene Reactions: Comment on the “Cycloaddition of Olefins to Methyl Acrylate”

Abstract Recently we became aware of a communication describing a very simple synthesis of cyclobutanes. Sands1) claimed to have obtained substituted methyl cyclobutanecarboxy-lates by aluminium chloride catalyzed reaction of methyl aerylate with olefins, such as isobutylene, 2-methyl-2-butene, tetramethylethylene, 4-methyl-2-butene (?) and 2,3-dimethyl-1-butene. This synthesis of cyclobutanes seemed amazingly simple, but questionable in view of the fact that certain olefins had been reported to undergo ene reactions with methyl acrylate under very similar reaction conditions2),3). These conflicting reports provoked our effort to establish irrevocably the nature of the products obtained by Sands' method.