The cyclic addition of alkoxyl radicals I. Cyclic additions of 4-pentenoxyl radical

Rieke, Reuben D.; Moore, Ned A.

doi:10.1016/s0040-4039(01)88079-5

Cited by 17 publications

(6 citation statements)

References 6 publications

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“…The more favorable entropy of activation associated with the formation of the smaller possible ring (Section IV ,A) has also been advanced (163,164) as an explanation for the preferential 1,5 cyclization of 5-hexenyl radical. Careful scrutiny of the temperature dependence of each mode of ring closure has allowed this hypothesis to be tested (755).…”

Section: 39mentioning

confidence: 98%

“…Thus, photolysis of the nitrite 102 gives good yields (-70%) of the oxime 104 or the nitroso dimer via specific 1,5 ring closure of the intermediate radical 103. The regioselectivity of these reactions has been attributed to entropy factors (163). For example, in contrast to its alkenyl analogue, which undergoes substantial 1,6 ring closure (154,756), the radical 105 undergoes only 1,5 ring closure.…”

Section: E Alkenoxy Alken Aminyi and Other Heteroatom-centered Radimentioning

confidence: 99%

“…The regioselectivity of these reactions has been attributed to entropy factors (163). 102 103 104 0· Ö 105 Photolysis of 5-hexenyl nitrite (106) affords no cyclic product (163,265). Unfortunately, no accurate rate constants are available, but ESR data (268) and product studies (265) suggest that cyclization of 103 is very fast (k > 10 8 sec -1 ) and competes effectively with intramolecu lar hydrogen transfer from an unactivated CH 2 group.…”

Section: E Alkenoxy Alken Aminyi and Other Heteroatom-centered Radimentioning

confidence: 99%

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Free-Radical Rearrangements

Beckwith¹,

Ingold²

1980

Organic Chemistry: A Series of Monographs

114

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Section: 39mentioning

confidence: 98%

Section: E Alkenoxy Alken Aminyi and Other Heteroatom-centered Radimentioning

confidence: 99%

Section: E Alkenoxy Alken Aminyi and Other Heteroatom-centered Radimentioning

confidence: 99%

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Free-Radical Rearrangements

Beckwith¹,

Ingold²

1980

Organic Chemistry: A Series of Monographs

114

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“…There is no reason, a priori, to presume that the pridiate, which proceeds on to distonic radical cations with altermary P-alkoxy radical intermediates leading to the major native carbon-xygen bond formation. 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).…”

Section: Discussionmentioning

confidence: 99%

“…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%

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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Radical Cyclization Reactions

et al. 1996

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Radical cyclization reactions are among the most powerful and versatile methods for the construction of mono‐ and polycyclic systems. The advantages these reactions offer to the synthetic organic chemist include high functional group tolerance and mild reaction conditions combined with high levels of regio‐ and stereochemistry. Furthermore, the recent progress in radical chemistry has led to the development of a broad range of very useful practical methods to conduct radical cyclization reactions. In general, radical cyclization reactions comprise three basic steps: selective radical generation, radical cyclization, and conversion of the cyclized radical to the product. For the generation of the initial radical a broad variety of suitable precursors can be employed, such as halides, thio‐ and selenoethers, alcohols, aldehydes and hydrocarbons. The cyclization step usually involves the intramolecular addition of a radical to a multiple bond. Most often carbon–carbon multiple bonds are employed; however, there are also examples known for the addition to carbon–oxygen and carbon–nitrogen bonds. Depending on the method employed, the cyclized radical is converted to the desired product by trapping with a radical scavenger, by a fragmentation reaction, or by an electron transfer reaction. The section Mechanism, Regio‐ and Stereochemistry provides an introduction to the key features of radical cyclization with a special emphasis on the factors controlling the regio‐ and stereochemistry. The section Scope and Limitations covers the different methods used to conduct radical cyclization. The basic principles of radical chemistry and general practical considerations when conducting radical cyclizations are not discussed in detail. Several excellent review articles and books dealing with these topics are available.

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The cyclic addition of alkoxyl radicals I. Cyclic additions of 4-pentenoxyl radical

Cited by 17 publications

References 6 publications

Free-Radical Rearrangements

Free-Radical Rearrangements

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

Radical Cyclization Reactions

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