Methods in alkaloid synthesis. Imino ethers as donors in the Michael reaction

Trost, Barry M.; Kunz, Robert A.

doi:10.1021/ja00857a030

Cited by 68 publications

(29 citation statements)

References 19 publications

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“…This material was prepared from 2.0 g (23 mmol) of 3-methyl-3-buten-1-01 in 97% crude yield according to the procedure of Trost and Kunz (27) to give 9d as a yellow oil that was used directly in the dianion alkylation or to prepare the iodide 9b above.…”

Section: -Methyl-3-brrterzyl-i-p-tolrrenesrclforzate (9d)mentioning

confidence: 99%

The synthesis of the isomeric components of San Jose scale pheromone — an illustration of a stereospecific synthesis of trisubstituted alkenes

Alderdice¹,

Spino²,

Weiler³

1993

Can. J. Chem.

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The three isomeric components of the San Jose scale pheromone, 5-7, have been synthesized from a common P-keto ester intermediate. A study of the alkylation of the dianion of methyl acetoacetate with a series of alkylating agents with the same carbon skeleton has been carried out. The trisubstituted alkenes in 5 and 6 have been synthesized stereospecifically via a copper-catalyzed coupling of a methyl Grignard reagent with the E or Z en01 phosphate from the alkylated P-keto ester. In the case of the Z en01 derivative, the coupling reaction was carried out on the diethyl-and diphenylphosphates, and the en01 triflate. 'The diethyl en01 phosphate gave the highest stereoselectivity. The synthetic pheromones were attractive to San Jose scale in the field.MARGOT ALDERDICE, CLAUDE SPINO et LARRY WEILER. Can. J. Chem. 71, 1955Chem. 71, (1993. Utilisant un p-ceto ester commun comme intermediaire, on a synthetise les trois isomitres 5-7 de la pheromone du pou de San JosC. On a rCalisC une Ctude de I'alkylation du dianion de 1'acCtoacetate de mCthyle par une sCrie d'agents d'alcoylation ayant le m&me squelette carbone. On a synthCtisC les alcitnes trisubstituCs 5 et 6 d'une maniitre stCreospCcifique en faisant appel a un couplage catalysC par le cuivre d'un mCthyl magnesien avec le phosphate d'Cnol E ou Z obtenu B partir du p-ceto ester alcoyle. Dans le cas du dCrivC Cnolique Z, on a rCalisC la reaction de couplage sur les phosphates Cnoliques diCthyle et de diphenyle et sur le triflate Cnolique. Le phosphate Cnolique diethylique donne la meilleure sterCosClectivitC. Dans les champs, les phCromones de synthitse attirent le pou de San Jose.[Traduit par la redaction]

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Section: -Methyl-3-brrterzyl-i-p-tolrrenesrclforzate (9d)mentioning

confidence: 99%

The synthesis of the isomeric components of San Jose scale pheromone — an illustration of a stereospecific synthesis of trisubstituted alkenes

Alderdice¹,

Spino²,

Weiler³

1993

Can. J. Chem.

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“…[46,47] Die Anellierung mit Pyrrolidin (über ein Enamin-Intermediat) war wesentlich effizienter als andere basische Bedingungen, insbesondere fürH ydrindenonsysteme. [46,47] Die Anellierung mit Pyrrolidin (über ein Enamin-Intermediat) war wesentlich effizienter als andere basische Bedingungen, insbesondere fürH ydrindenonsysteme.…”

Section: Aldolcyclisierungunclassified

Enantioselektive Synthese von Robinson‐Anellierungsprodukten und Michael‐Addukten als Vorstufen

Gallier

Martel²,

Dujardin³

2017

Angewandte Chemie

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Die Robinson‐Anellierung hat seit ihrer Entdeckung 1935 in zahlreichen Synthesen Anwendung gefunden, besonders auf dem Gebiet der Steroidsynthese. Die Produkte werden gewöhnlich nach drei aufeinanderfolgenden Stufen erhalten: der Bildung eines Enolats (oder Derivats davon), einer konjugierten Addition und einer Aldolreaktion. Im Laufe der Jahre wurden mehrere methodische Verbesserungen für jede einzelne Stufe vorgenommen oder alternative Synthesewege hin zu Robinson‐Anellierungsprodukten entwickelt. Im ersten Teil dieses Aufsatzes werden die wichtigsten Entwicklungen für die Bildung Monocarbonyl‐abgeleiteter Robinson‐Anellierungsprodukte (MRA‐Produkten, MRAPs) und von einer aktivierten Monocarbonylverbindung abgeleiteter Robinson‐Anellierungsprodukte (AMRA‐Produkten, AMRAPs) erläutert. In den folgenden Abschnitten werden diastereoselektive und enantioselektive Synthesen dieser Produkte beschrieben, und im letzten Abschnitt wird die Racematspaltung von Enantiomerenmischungen dargelegt.

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“…Unfortunately, however, this plan was thwarted at an early stage by the fact that when cyclohexenone 16 was treated with lithium dimethyl cuprate in diethyl ether at O°C, the solvent was replaced by 1,2-dimethoxyethane, and the resulting solution of enolate was treated with iodo alkene 41, the major product isolated was that of simple conjugate addition, 2,3-dimethylcyclohexenone, very little alkylation of the enolate having taken place. This undesired result can be attributed at least in part to P elimination from the homoallylic iodide, 41, (thus providing a source of protons for ketonization of the enolate) under the highly basic conditions of the reaction, although other workers have reported no problems with the same alkylating reagent and related carbanionic substrates (64,82). 36 This octalone was prepared, in the early stages of our work, by the method of Kelly and Zamecnik (12c), but we later found the more selective Boeckman sequence to be somewhat more satisfactory.…”

Section: Total Synthesis Of Ishwaranementioning

confidence: 99%

“…j71n one small-scale experiment, probably due to loss of methyllithium during addition, the intermediate dibromocyclopropane, 64, was isolated and could be completely characterized. It appeared to be a mixture of diastereomers, indicating that the addition of dibromocarbene to the octalin was non-stereoselective (cf.…”

Section: Generrdmentioning

confidence: 99%

Carbon atom insertion bicycloannulation: total syntheses of ishwarane and ishwarone

Cory¹,

Burton²,

Chan³

et al. 1984

Can. J. Chem.

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. Can. J. Chem. 62, 1908Chem. 62, (1984. insertion of a carbon atom into a methyl cyclohexene, leading in a single synthetic step to a bicyclo[3.2. I .02.']octane by carbene addition to the double bond and carbene insertion into a methyl C-H bond, has been accomplished by treating the cyclohexene with carbon tetrabromide and methyllithium at low temperatures. This new bicycloannulation method has been employed in a total synthesis of ishwarane (I), the naturally occurring parent hydrocarbon of the ishwarane class of tetracyclic sesquiterpenes. Although this reaction was not successful with various possible precursors of ishwarone (2), this natural product was prepared in low yield by a two-step version of the carbon atom insertion bicycloannulation (CAiB) procedure involving addition of bromoform-derived dibromocarbene to the octalone (5) followed by treatment of the resulting dibromocyclopropane (56) with methyllithiurn. The same two-step sequence was also successful in the first synthesis of norishwarane (20), the hydrocarbon comprising the bare ring system of the ishwarane sesquiterpenoids. The Diels-Alder synthesis used in the preparation of the octalin precursor (18) of norishwarane could not be used for the terpenes themselves because of the lack of dienophilic reactivity of the required cyclohexenone (7). A regioselective Diels-Alder equivalent sequence was therefore developed, consisting of conjugate addition of lithium di(3-methyl-3-buteny1)cuprate (42) to 2,3,4-trimethylcyclohex-Zen-I-one (7), epoxidation, base-catalyzed cyclization of the resulting epoxide (47) to a mixture of primary and tertiary alcohols (50 and 49, respectively), and dehydration of 49 to give 5. In the case of ishwarane, the octalin precursor (62) was synthesized by conjugate addition of lithium dimethylcuprate to octalone 59, addition of methyl magnesium bromide to the resulting decalone (60) to give octalol 61, and dehydration. Chem. 62, 1908Chem. 62, (1984.En faisant rkagir le cyclohexkne avec le titrabromure de carbone et le mCthyllithium a basse tempkrature, on a rtalisC I'insertion d'un atome de carbone dans le mCthylcyclohexkne; on a ainsi obtenu en une seule Ctape le bicyclo[3.2.1 .02.']octane par I'addition de carbene sur la double liaison et par une insertion de carbkne dans une liaison C-H du mithyle. OR a utilisee cette nouvelle methode de bicycloannellation dans une synthttse totale de I'ishwarane (I), I'hydrocarbure naturel parent des sesquiterpknes tetracycliques de la classe de I'ishwarane. Bien que cette reaction n'aie pas pu &tre appliquCe avec succes i divers precurseurs possibles de I'ishwarone (2), on a prepare ce produit naturel avec un faible rendement en faisant appel a une version en deux Ctapes de la mtthode de bicycloannellation par insertion d'un atome de carbone (BIAC) impliquant une addition d'un dibromocarbkne, provenant du bromoforme, sur I'octalone (51, puis une reaction du dibromocyclopropane (56) qui en rtsulte avec du mCthyllithium. On a aussi utilist cette mCthode avec succks pour realiser ...

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Methods in alkaloid synthesis. Imino ethers as donors in the Michael reaction

Abstract: kindly communicated to us that he found a similar product in the Tl(lll) oxidation of etlolporphyrln I. The NMR spectrum was very similar to the spectrum reported here (two methine proton signals), and elemental analysis also yielded additional hydrogen and oxygen. (29) D. F.

Cited by 68 publications

References 19 publications

The synthesis of the isomeric components of San Jose scale pheromone — an illustration of a stereospecific synthesis of trisubstituted alkenes

The synthesis of the isomeric components of San Jose scale pheromone — an illustration of a stereospecific synthesis of trisubstituted alkenes

Enantioselektive Synthese von Robinson‐Anellierungsprodukten und Michael‐Addukten als Vorstufen

Carbon atom insertion bicycloannulation: total syntheses of ishwarane and ishwarone

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