Bidentate Lewis Acids for the Activation of 1,2‐Diazines – A New Mode of Catalysis

Kessler, Simon N.; Neuburger, Markus; Wegner, Hermann A.

doi:10.1002/ejoc.201100335

Cited by 68 publications

(62 citation statements)

References 36 publications

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“…As mentioned earlier, the ability to introduce a substituent at the vinylic position adjacent to the oxygen atom is exemplified in entry 2 (2-n-butyl-DHP was readily synthesized by lithiation/alkylation [33] ). Importantly, the enol ether can be substituted at the nonvinylic position adjacent to the ether oxygen, as demonstrated by the use of ( S )-2-[(benzyloxy)methyl]-2,3-dihydrofuran in entry 3.…”

Section: Resultsmentioning

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: Resultsmentioning

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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“…The rigid geometry of phthalazine ( 7 ) and the defined position of the nitrogen atoms made it a perfect candidate for such an investigation. The bis‐borane scaffold 9,10‐dimethyl‐9,10‐dihydroboranthracene ( 10 ) was selected as the catalyst . It showed the desired performance in the computational screening and is synthetically easily accessible .…”

Section: Bidentate Lewis Acid Catalysis By the Activation Of The Starmentioning

confidence: 99%

Bis‐Boron Compounds in Catalysis: Bidentate and Bifunctional Activation

Schweighauser

Wegner

2016

Chemistry A European J

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The development of metal-free catalysts as an alternative to the use of transition metals has gained tremendous interest in the past. In catalysis, Lewis acidity is one of the major principles used for the activation of organic compounds. Improving the reactivity and selectivity of Lewis acids by utilizing bidentate interactions was already proposed 50 years ago. Nevertheless, product inhibition due to strong binding has made applications of bidentate Lewis acids challenging for many years. Recently, bis-boron compounds have been found to be very effective and several applications in Diels-Alder reactions, carbon dioxide reduction, and ammonia-borane dehydrogenation were reported. All three transformations are enabled by the catalyst at different stages during the course of the reaction. These new and useful examples illustrate the great potential of the concept.

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“…These researchers employed a novel diboraanthracene for bidentate activation of phthalazine towards cycloadditions with enamines and enol ethers, allowing reactions to take place at 40–170 °C. 11,12 We describe the development of silver-catalyzed cycloaddition between phthalazines and siloxy alkynes, 13,14 corresponding to a formal IEDDA reaction, that take place with concomitant loss of nitrogen to afford a wide range of silyl-protected 2-naphthols (Eq. 1).…”

mentioning

confidence: 99%

Silver-Catalyzed Formal Inverse Electron-Demand Diels–Alder Reaction of 1,2-Diazines and Siloxy Alkynes

et al. 2012

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Bidentate Lewis Acids for the Activation of 1,2‐Diazines – A New Mode of Catalysis

Cited by 68 publications

References 36 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

Bis‐Boron Compounds in Catalysis: Bidentate and Bifunctional Activation

Silver-Catalyzed Formal Inverse Electron-Demand Diels–Alder Reaction of 1,2-Diazines and Siloxy Alkynes

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