An alkynylboronate cycloaddition strategy to functionalised benzyne derivatives

Kirkham, James D.; Delaney, Patrick M.; Ellames, George J.; Row, Eleanor C.; Harrity, Joseph P. A.

doi:10.1039/c0cc01345e

Cited by 43 publications

(15 citation statements)

References 42 publications

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“…Thus, this cycloaddition methodology appears to be a convenient platform from which a range of new stereochemically defined 1,2-disubstituted BCBs can be obtained. Because of the easy access to various aryne precursors [41–43] and the various functionalized BCBs that can be obtained from them, this chemistry is likely to see utility in wide-ranging areas, from organic synthesis to materials chemistry, and electronics.…”

Section: Discussionmentioning

confidence: 99%

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: Discussionmentioning

confidence: 99%

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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“…In this case, the regiochemistry is believed to be mainly controlled by the steric bulkiness of the C3-silyl group of 4f. 68) Despite extensive examples in the literature involving the reactions of halobenzynes with a range of arynophiles, [79][80][81][82][83][84][85][86][87][88][89][90][91][92] the nucleophilic fluorination of halobenzynes 4h-4k, generated from 3h, 3i, 3j′, and 3k′, with Bu 4 NF(t-BuOH) 4 under normal batch conditions produced complex mixtures, and the yields of the expected fluorobenzenes 1 were very poor ( Table 3). In stark contrast, the reaction of 5-chloro-3-(tertbutyldimethylsilyl) benzyne (4h), generated from 3h, with Bu 4 NF(t-BuOH) 4 under the optimized flow conditions produced 1h in 51% yield as a mixture of two regioisomers (meta-1h/ortho-1h=1.2 : 1, Entry 1).…”

Section: Resultsmentioning

confidence: 99%

Microflow Fluorinations of Benzynes: Efficient Synthesis of Fluoroaromatic Compounds

2018

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Fluorinated aromatic compounds are found in a variety of biologically active compounds, including clinical drugs and agrochemicals. Therefore, the synthesis of aryl fluorides is particularly important in the medicinal and process chemistry fields. In this paper, we report a method for the synthesis of aryl fluorides by benzyne fluorination under microflow conditions using the efficient Comet X-01 micromixer. In comparison to our previously reported method under ordinary batch conditions, this approach facilitates a significant reduction in reaction times, to ca. 10 s, as well as increases in the yields of fluoroarenes (by up to 51%).

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“…It requires very little energy without catalyst, and thus has been widely used in many organic reactions [ 44 , 45 , 46 ]. Alkynylboronates have found to be reactive reagents to undergo the [2 + 4] cycloaddition to form six-membered functionalized organoboronates [ 47 , 48 ]. Harrity, et al ., found that alkynylboronates are relatively electron rich and thus have a cycloaddition reactivity that resembles that of acetylene.…”

Section: [2+4] Cycloadditionmentioning

confidence: 99%

“…Harrity, et al ., found that alkynylboronates are relatively electron rich and thus have a cycloaddition reactivity that resembles that of acetylene. Therefore, the [2 + 4] reactions between alkynylboronates and electron-rich dienes were unsuccessful [ 47 , 48 ]. The use of cyclopentadienones, tetrazines and 2-pyrones as diene components led to the formation of highly functionalized organoboron synthetic intermediates as outlined in Scheme 9 .…”

Section: [2+4] Cycloadditionmentioning

confidence: 99%

Application of Cycloaddition Reactions to the Syntheses of Novel Boron Compounds

et al. 2010

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This review covers the application of cycloaddition reactions in forming the boron-containing compounds such as symmetric star-shaped boron-enriched dendritic molecules, nano-structured boron materials and aromatic boronic esters. The resulting boron compounds are potentially important reagents for both materials science and medical applications such as in boron neutron capture therapy (BNCT) in cancer treatment and as drug delivery agents and synthetic intermediates for carbon-carbon cross-coupling reactions. In addition, the use of boron cage compounds in a number of cycloaddition reactions to synthesize unique aromatic species will be reviewed briefly.

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An alkynylboronate cycloaddition strategy to functionalised benzyne derivatives

Abstract: A new approach to benzyne precursors has been developed that involves the [4+2] cycloaddition of trimethylsilyl alkynylboronates with 2-pyrones, followed by oxidation and trifluoromethylsulfonylation of the boronate moiety.

Cited by 43 publications

References 42 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

Microflow Fluorinations of Benzynes: Efficient Synthesis of Fluoroaromatic Compounds

Application of Cycloaddition Reactions to the Syntheses of Novel Boron Compounds

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