[2 + 2] Cycloaddition of ethyl propiolate and silyl enol ethers

Clark, Robin D.; Untch, Karl G.

doi:10.1021/jo01316a020

Cited by 79 publications

(17 citation statements)

References 10 publications

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“…However, we found that the addition of EP (1) to the enamine 26, when performed under solvent-free conditions, led to the corresponding [2ϩ2] cycloadduct 27, while, when DMAD (5) was used as the acetylenic partner, the cycloheptadiene derivative 29, resulting from the ring expansion of the initially formed [2ϩ2] cycloadduct 28, was isolated. It should be noted that such a ring-expansion reaction was never observed during the addition of ketene trimethylsilyl acetal 8 to DMAD (5). Moreover, when the cycloadduct 13 was heated in toluene at reflux, [14] the starting material was recovered completely (Scheme 6).…”

Section: Resultsmentioning

confidence: 99%

“…[2] This also proves to be true for the [2ϩ2] cycloaddition of 1,1-dimethoxyalkenes and cyclic enol ethers to acetylenecarboxylates. [3] On the other hand, [2ϩ2] cycloadditions of alkenes, [4] silyl enol ethers, [5,6] acyclic ketene trimethylsilyl acetals [7] and allylsilanes [8] with electrophilic acetylenes need to be promoted by Lewis acid to afford the corresponding cyclobutenes (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

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Uncatalyzed, Solvent-Free [2+2] Cycloaddition of Cyclic Ketene Trimethylsilyl Acetals with Electrophilic Acetylenes

Miesch

Wendling

2000

Eur. J. Org. Chem.

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Cyclic ketene trimethylsilyl acetals reacted with electrophilic acetylenes (ethyl propynoate, dimethyl acetylenedicarboxylate and ethynyl methyl ketone) to afford the corresponding [2+2] cycloadducts. The reactions were run at room temperature, without a catalyst and under solvent-free conditions. Scheme 1. [2ϩ2] Cycloaddition without activation and with activation [a][a] Chromatography on silica gel was not necessary in this case.Scheme 5. Stereoselective [2ϩ2] cycloaddition of 23 with EP (1) and DMAD (5) Scheme 6. [2ϩ2] Cycloaddition of enamine 26 with EP (1) and DMAD (5) Eur.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Uncatalyzed, Solvent-Free [2+2] Cycloaddition of Cyclic Ketene Trimethylsilyl Acetals with Electrophilic Acetylenes

Miesch

Wendling

2000

Eur. J. Org. Chem.

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“…Methyl enol ethers 2bϪd and 2f were prepared according to reported procedures. [13,14] The silyl enol ethers 2e, [7b] 2g, 2h, 2j, 2k and 2l [15] were prepared by Duboudin's modified procedure [16] starting from the appropriate chlorosilane and ketone (NaI/Et 3 N/MeCN/20°C). Spectroscopic data of adducts 3a/4a, 3d/4d and 3e/4e were described in a previous paper by our group.…”

Section: Methodsmentioning

confidence: 99%

Lewis Acid Catalysed [4+2] Heterocycloadditions between Ketone Enol Ethers and β-Ethylenic α-Oxo Esters

Martel¹,

Leconte²,

Dujardin³

et al. 2002

Eur. J. Org. Chem.

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The [4+2] heterocycloaddition reaction between (E)-γ-substituted β-unsaturated α-oxo esters 1a−d and cyclic and acyclic ketone enol ethers 2a−l afforded heteroadducts 3−5 in high yields when either [Eu(fod) 3 ] or SnCl 4 were used as the catalyst. With methyl (E)-benzylidenepyruvate (1a), the two catalytic modes displayed divergent stereoselectivities. In the case of the heterocycloaddition of silyl enol ether 2h, X-ray investigations established the relative configurations of the bicyclic adducts 3h and 5h, each obtained as the major isomer with [Eu(fod) 3 ] and with SnCl 4 , respectively. These as- [a] signments provided valuable information concerning the concerted vs. nonconcerted mechanism of these acid-catalysed reactions. With methyl (E)-tert-butoxymethylenepyruvate (1d), the scope of the reaction proved to be restricted to alkyl enol ethers as the dienophiles. In this case, the stereochemical process followed a different pathway, exemplified by the X-ray structure of the adduct 4q, obtained with total stereoselectivity from 1d and 1-methoxycyclohexene (2f) when SnCl 4 was the catalyst. present a survey of these results, and Ϫ from stereochemical assignment of representative structures Ϫ to deduce a set of significant arguments concerning the concerted vs. nonconcerted mechanisms that can be ascribed to [Eu(fod) 3 ]vs. SnCl 4 -catalysed reactions.

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“…Results and Discussion Preparation and Isolation of 2A,6X-Bis-O-(mesi-tylsulfony1)-@-cyclodextrins (10-16). 6 are converted to (28)-2,3anhydro-8-cyclodextrin (1) lla*16 and 3,6-anhydro-fl-cyclodextrin (9),17b respectively. The two arylsulfonyl groups in 10-16 were selected from among phenylsulfonyl, p-tosyl, mesitylsulfonyl, l-naphthylsulfonyl, and 2-naphthylsulfonyl groups to give the best resolution in reversed-phase column chromatography as described below.…”

Section: Hydroxy-8-( Hydroxymethyl)-7-methyl-3-[ (2)-prop-l-enyllnaphmentioning

confidence: 99%

Preparation and enzymic structure determination of a complete set of 2A,6X-bis (O)-(sulfonyl)-.beta.-cyclodextrins

Fujita¹,

Ishizu²,

Obe³

et al. 1992

J. Org. Chem.

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Received M a y 13, 19922A,6x-Bis-0-(mesitylsulfonyl)-@-cyclodextrins (X = A-G) were prepared by the reaction of 2-O-(mesitylsul-fony1)-8-cyclodextrin with mesitylenesulfonyl chloride in pyridine. All regioisomers were isolated and their structures determined.Bifunctionalization of cyclodextrins has attracted much attention with respect to the construction of artificial en-The reaction of (trimethylsily1)vinyl selenide 1 and (trimethylsi1yl)allenyl selenide 2 with vinyl ketones 3a-c in the presence of a Lewis acid gave cyclobutane derivatives stereoseledively. The reaction of 1 and 3a-c with SnCb was quenched either with EhN to give cyclobutanes 4a-c or with H20 to give acylsilanes 1 la-c. The formation of both products is explained in terms of a zwitterionic intermediate. The cis relationship between the phenylseleno group and the carbonyl group of 4a-c is rationalized by consideration of a combination of secondary-orbital interactions and steric effects in the early stage of intermediate formation.

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[2 + 2] Cycloaddition of ethyl propiolate and silyl enol ethers

Cited by 79 publications

References 10 publications

Uncatalyzed, Solvent-Free [2+2] Cycloaddition of Cyclic Ketene Trimethylsilyl Acetals with Electrophilic Acetylenes

Uncatalyzed, Solvent-Free [2+2] Cycloaddition of Cyclic Ketene Trimethylsilyl Acetals with Electrophilic Acetylenes

Lewis Acid Catalysed [4+2] Heterocycloadditions between Ketone Enol Ethers and β-Ethylenic α-Oxo Esters

Preparation and enzymic structure determination of a complete set of 2A,6X-bis (O)-(sulfonyl)-.beta.-cyclodextrins

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