[2+2] Cycloaddition of Benzyne and Ketene Silyl Acetal as an Efficient Route to Benzocyclobutenones

Hosoya, Takamitsu; Hasegawa, Takayuki; Kuriyama, Y.; Matsumoto, Takashi; Suzuki, Keisuke

doi:10.1055/s-1995-4913

Cited by 73 publications

(32 citation statements)

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“…A similar stereochemical outcome has been reported for the significantly electron-rich, acyclic E / Z β-silyloxy ketene silyl acetals derived from α-( tert -butyldimethylsilyloxy)methyl acetate and the E / Z -ketene silyl acetals drived from ethyl propionate. [26g] However, in that study as well, the E -ketene silyl acetal underwent an ene-type process to a significant extent, and the minor erosion of stereochemistry observed at the ring junction was attributed to this side reaction (called a [4 + 2] process). [26g] All such problems are likely avoidable in reactions of cyclic enol ethers.…”

Section: Resultsmentioning

confidence: 98%

“…In contrast with the limited literature on the reactions between arynes and enol ethers, literature on the reactions between arynes and ketene acetals is more extensive, [25,26] and the utility of reactions between alkoxy-substituted arynes and silyl ketene acetals has been substantially documented. [26] These reagents have provided access to benzocyclobutenones and related complex architectures.…”

Section: Introductionmentioning

confidence: 99%

“…[26] These reagents have provided access to benzocyclobutenones and related complex architectures. [26] …”

Section: Introductionmentioning

confidence: 99%

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Cycloaddition of Arynes and Cyclic Enol Ethers as a Platform for Access to Stereochemically Defined 1,2‐Disubstituted Benzocyclobutenes

et al. 2014

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Benzocyclobutenes (BCBs) are important entities in a multitude of areas, such as complex organic synthesis, materials and polymer chemistry, and electronics. Whereas reactions between arynes and ketene acetals have been well studied, reactions with cyclic enol ethers are unknown. A cis olefin geometry in cyclic enol ethers makes them well suited for formal [2 + 2] cycloaddition with arynes than for competing ene reactions, making them effective reactants. Reactions of 2,3-dihydrofuran, 2,3-dihydro-3H-pyran, 5-butyl-2,3-dihydrofuran, (S)-2-((benzyloxy)methyl)-2,3-dihydrofuran, and 1,4-dioxene with various arynes were successful. An advantage of the use of cyclic enol ethers is that despite the plausible intermediacy of zwitterionic intermediates, the products are limited to a cis ring junction. This can be exploited for potential access to stereochemically-defined 1,2-disubstituted BCBs. As a demonstration, ether ring cleavage with BBr3 provided trans-functionalized BCBs and displacement with azide then provided cis derivatives. DFT computations have been utilized to understand the structures of three arynes in relation to the cycloadditions and for a predictive evaluation of product ratios in two cases. A comparative evaluation of the HOMO energies of a related series of cyclic olefins has also been performed by DFT computations.

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Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Cycloaddition of Arynes and Cyclic Enol Ethers as a Platform for Access to Stereochemically Defined 1,2‐Disubstituted Benzocyclobutenes

et al. 2014

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“…Thus, the synthesis established the stereochemistry of 2 in terms of the relative sense (the C5 stereochemistry was originally misassigned) and the absolute sense (the synthetic material was the enantiomeric to the natural product [5] The first step is the [2+2] cycloaddition of an α-alkoxybenzyne to an olefin. Ketene silyl acetal worked nicely as an olefinic component in this cycloaddition, with the rigorous regioselectivity in a way that the silyl acetal moiety comes near to the alkoxy group of the benzyne (Scheme 5) [6]. The regioselectivity persisted for a variety of ketene silyl acetals, thereby making accessible various benzocyclobutenes of synthetic versatility.…”

Section: First Total Synthesis Of Ravidomycinmentioning

confidence: 90%

Synthetic study of ravidomycin, a hybrid natural product

Suzuki

2000

Pure and Applied Chemistry

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Strategies and tactics associated with the total synthesis of hybrid natural products are discussed. The target is ravidomycin (2), one of the gilvocarcin-class antitumor antibiotics with an aryl C-glycoside structure. The first total synthesis of 2, which was achieved along similar lines of that of gilvocarcin V (1), served for the determination of the relative as well as the absolute stereochemistry of 2. Also revealed was a limitation of the synthetic scheme so long as the amino sugar congener was concerned. A preliminary result is discussed on the [2+2+2] approach that relies on the ready availability of various benzocyclobutene derivatives via regioselective [2+2] cycloaddition of α-alkoxybenzynes and ketene silyl acetals.

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“…Die vollkommene Regioselektivität wird mit dem induktiven Elektronenzug der Alkoxy-oder Benzyloxy-Gruppe erklärt und ist in Einklang mit Grenzorbital-Betrachtungen. [16] Ersetzt man 5 durch das vollständig oxygenierte Silylacetal 8 (R = SitBuMe 2 ), lässt sich diese Synthesemethode auch auf gespanntere Benzocyclobutendione wie 9 ausdehnen. [17] Wie im Fall von 5 werden übli-cherweise die tert-ButyldimethylsilylDerivate eingesetzt.…”

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Synthese des Kohlenstoffoxids C₁₂O₆ über hoch gespannte Benz‐ine

Butenschön

2007

Angewandte Chemie

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[2+2] Cycloaddition of Benzyne and Ketene Silyl Acetal as an Efficient Route to Benzocyclobutenones

Cited by 73 publications

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Cycloaddition of Arynes and Cyclic Enol Ethers as a Platform for Access to Stereochemically Defined 1,2‐Disubstituted Benzocyclobutenes

Cycloaddition of Arynes and Cyclic Enol Ethers as a Platform for Access to Stereochemically Defined 1,2‐Disubstituted Benzocyclobutenes

Synthetic study of ravidomycin, a hybrid natural product

Synthese des Kohlenstoffoxids C₁₂O₆ über hoch gespannte Benz‐ine

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[2+2] Cycloaddition of Benzyne and Ketene Silyl Acetal as an Efficient Route to Benzocyclobutenones

Cited by 73 publications

References 0 publications

Cycloaddition of Arynes and Cyclic Enol Ethers as a Platform for Access to Stereochemically Defined 1,2‐Disubstituted Benzocyclobutenes

Cycloaddition of Arynes and Cyclic Enol Ethers as a Platform for Access to Stereochemically Defined 1,2‐Disubstituted Benzocyclobutenes

Synthetic study of ravidomycin, a hybrid natural product

Synthese des Kohlenstoffoxids C12O6 über hoch gespannte Benz‐ine

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Synthese des Kohlenstoffoxids C₁₂O₆ über hoch gespannte Benz‐ine