Cyclic ether formation in superacid media

Carr, Graham; Whittaker, D.

doi:10.1039/p29890000359

Cited by 23 publications

(12 citation statements)

References 5 publications

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“…The residue was distilled at atmospheric pressure to yield 4.6 g (67%) of the alcohol 17 (bp 156-157°C). The I H nrnr spectrum was similar to that reported in the literature (22,29). 'H nrnr (250.13 MHz, CDCl,) ST,,: 1.20 (d, 3H, ,J,, = 6.1 HZ, CH, (1-H) (5) (1.2 g, 0.0078 mol), in 80 mL of acetonitrile was degassed with nitrogen and irradiated for 139 h using a 1-kW lamp.…”

Section: -(4-supporting

confidence: 76%

“…The rules pertaining to the cyclization of radical intermediates were greatly expanded by Beckwith et al (5). Several examples of the cyclization of alkenols, involving a wide variety of mechanisms, have been reported (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26). There are, however, few reported examples of cyclization involving the alkenol radical cation, generated by photoinduced single electron transfer, and these examples have been limited to 1,ldiary1 substituted alkenes (9,10).…”

Section: Discussionmentioning

confidence: 99%

“…Deprotonation from products, the tetrahydrofurans (20,21), are more stable than the oxygen of the distonic radical cations gives the alternative the tertiary P-alkoxy radical leading to the tetrahydropyrans P-alkoxy radicals (reactions [5a] and [&I). Presumably, all of (22,23 (AM1)) that indicate that the tertiary P-alkoxy radical (22a) is, in fact, significantly more stable than the primary P-alkoxy radicals (20a and 21a) ( Table 2). The observed product ratios from the intramolecular cyclizations lead to the conclusion that the regiochemistry is kinetically, not thermodynamically, controlled.…”

Section: Discussionmentioning

confidence: 99%

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The photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 10: intramolecular reactions involving alk-4-enols and 1,4-dicyanobenzene

McManus¹,

Arnold²

1995

Can. J. Chem.

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Our study of the photochemical nucleophileeolefin combination, aromatic substitution (photo-NOCAS) reaction has been extended to include alk-4-enols. Irradiation of acetonitrile solutions of the alk-4-enols, 6-methyl-5-hepten-2-ol(16) and 5-methyl-5-hexen-2-01 (17). and the aromatic, 1,4-dicyanobenzene (I), leads to cyclized 1:l (alk-4-eno1:aromatic) adducts. The addition of biphenyl (5) to the irradiation mixture, serving as a codonor, increases the yields and the efficiency of formation of the adducts. The structures assigned to the products, trans-2-(isopropy 14-cyanopheny I)-5-methyltetrahydrofuran (18,29%) and cis-2-(isopropyl 4-cyanopheny1)-5-methyltetrahydrofuran (19,24%) from 16 (reaction [5j), and r-2-(methyl4-cyanopheny1)-2,t-5-dimethyltetrahydrofuran (20, 13%), r-2-(methyl4-cyanophenyl)-2,~-5-dimethyltetrahydrofuran (21,7%), r-3-(4-cyanophenyl)-3,t-6-dimethyltetrahydropyran (22, 11 %), and r-3-(4-cyanopheny1)-3,c-6-dimethyltetrahydropyran (23,2%), from 17 (reaction [6j), rests mainly upon analysis of the 'H and 13c nuclear magnetic resonance spectra. The structures of 19,22, and 23 were firmly established by X-ray crystallography. The observed ratio of regioisomers indicates a strong preference for 1,5-exo-trig, relative to 1,6-endo-trig, cyclization of the intermediate alk-4-en01 radical cation. The mechanistic implication of these results is discussed.Key words: photoinduced electron transfer, radical ions, cyclization of radical cations, intramolecular reactions of radical cations.

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Section: -(4-supporting

confidence: 76%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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The photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 10: intramolecular reactions involving alk-4-enols and 1,4-dicyanobenzene

McManus¹,

Arnold²

1995

Can. J. Chem.

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“…146 We reported the reaction with TfOH leading to a quantitative yield of 31 with 5 mol% catalyst at room temperature (Scheme 27). 147…”

Section: Scheme 26mentioning

confidence: 97%

Electrophilic Functionalization of Non-Activated Olefins Catalyzed by Lewis Superacids

Antoniotti¹,

Poulain-Martini²,

Duñach³

2010

Synlett

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“…These synthetic approaches often require the use of Brønsted acids and in some cases over-stoichiometric amounts must be used. [30,31] Coulombel et al recently reviewed the use of the trifluoromethane sulfonates TfOH, Al(TfO) 3 and Sn(TfO) 4 as Lewis super acids for the intramolecular cyclisation of alcohols of non-activated olefins. [32] In this sense, AgTfO [33] and lanthanide triflates are efficient catalysts for this transformation, which can be used in combination with ionic liquids at room temperature.…”

mentioning

confidence: 99%

Intramolecular Hydroalkoxylation of Non‐Activated CC Bonds Catalysed by Zeolites: An Experimental and Theoretical Study

et al. 2013

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The high activity and selectivity of zeolites in the cyclisation of unsaturated alcohols is reported for the first time; the details of a reaction mechanism based on quantum chemical calculations are also provided. The high efficiency of zeolites MFI, BEA and FAU in the cyclisation of unsaturated alcohols (cis-decen-1-ol, 6-methylhept-5-en-2-ol and 2-allylphenol) to afford oxygen-containing heterocyclic rings is demonstrated. The best catalytic performance is found for zeolites with the optimum concentration of Brønsted acid sites (ca. 0.2 mmol g(-1)) and the minimum number of Lewis acid sites. It is proposed that the efficiency of the catalysts is reduced by the existence of the so-called dual site, at which a molecule of unsaturated alcohol can simultaneously interact with two acid sites (an OH group with one and the double bond with the other Brønsted site), which increases the interaction strength. The formation of such adsorption complexes leads to a decrease in the catalyst activity because of (i) an increase in the reaction barrier, (ii) an unfavourable conformation and (iii) diffusion limitations. A new procedure for the preparation of tetrahydrofurans and pyrans over zeolite catalysts provides important oxygen-containing heterocycles with numerous applications.

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Cyclic ether formation in superacid media

Cited by 23 publications

References 5 publications

The photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 10: intramolecular reactions involving alk-4-enols and 1,4-dicyanobenzene

The photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 10: intramolecular reactions involving alk-4-enols and 1,4-dicyanobenzene

Electrophilic Functionalization of Non-Activated Olefins Catalyzed by Lewis Superacids

Intramolecular Hydroalkoxylation of Non‐Activated CC Bonds Catalysed by Zeolites: An Experimental and Theoretical Study

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