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Halogen atom transfer reactions radical cyclizations

The EtsB-induced halogen atom transfer radical cyclization reaction is a successful application. Cyclization of iodo acetal 44 afforded the tetrahydrofuran derivative 45 in almost quantitative yield (Scheme 26) [32]. Et3B also induced radical cyclization of A -allylic a-iodoacetamide to give y9-iodomethyl-y-lactam via an atom transfer process [34]. The reaction of 46 prepared from 2-prolinol proceeded smoothly within 10 min in boiling benzene in the presence of Et3B to yield IR, 8S)-... [Pg.24]

Highly enantioselective atom transfer radical cydization reactions catalyzed by chiral Lewis acids have been reported by Yang et al. [80]. Two main advantages of these enantioselective cyclizations include installing multiple chiral centers and retaining a halogen atom in the product, which allows for further functionalization. [Pg.138]

Alkoxyl radicals can be generated by a variety of methods including peroxide reduction, nitrite ester photolysis, hypohalite thermolysis, and fragmentation of epoxyalkyl radicals (for additional examples of alkoxyl radical generation, see Section 4.2.S.2). Hypohalites are excellent halogen atom donors to carbon-centered radicals, and a recent example of this type of cyclization from the work of Kraus is illustrated in Scheme 43.182 Oxidation of the hemiketal (57) presumably forms an intermediate hypoiodite, which spontaneously cyclizes to (58) by an atom transfer mechanism. Unfortunately, the direct application of the Barton method for the generation of alkoxyl radicals fails because the intermediate pyridine-thione carbonates are sensitive to hydrolytic reactions. However, in a very important recent development, Beckwith and Hay have shown that alkoxyl radicals are formed from N-alkoxypyridinethiones.183 Al-... [Pg.812]


See other pages where Halogen atom transfer reactions radical cyclizations is mentioned: [Pg.22]    [Pg.169]    [Pg.232]    [Pg.802]    [Pg.812]    [Pg.814]    [Pg.158]    [Pg.1173]    [Pg.695]    [Pg.734]    [Pg.338]    [Pg.812]    [Pg.820]   
See also in sourсe #XX -- [ Pg.4 , Pg.802 , Pg.803 ]

See also in sourсe #XX -- [ Pg.4 , Pg.802 , Pg.803 ]




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Atom transfer radical cyclization

Atom transfer radical cyclization reactions

Atom transfer reactions

Atom-transfer radical

Atom/radical reactions

Atomic halogens

Cyclization reactions

Halogen atom transfer

Halogen radicals

Halogen transfer

Halogenation reactions

Radical cyclization

Radical halogenations

Radical reaction cyclization

Radical reactions atom transfer

Radical reactions halogenation

Radical transfer

Radical transfer reactions

Radical, halogenation

Radicals halogen atom

Reactions halogens

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