Tandem Radical Cyclizations and Alkylations

The synthetic scope of radical cyclizations can be further extended by tandem trapping by electrophilic alkene. 

Alkenyl radicals generated by intramolecular addition to a triple bond can add to a nearby double bond, resulting in a tandem cyclization process. 

Reactions Involving Carbocations, Carbenes, and Radicals as Reactive Intermediates 

As with carbocation-initiated polyene cyclizations, radical cyclizations can proceed through several successive steps if the steric and electronic properties of the reactant provide potential reaction sites. Cyclization may be followed by a second intramolecular step or by an intermolecular addition or alkylation. Intermediate radicals can be constructed so that hydrogen atom transfer can occur as part of the overall process. For example, 2-bromohexenes having radical stabilizing substituents at C(6) can undergo cyclization after a hydrogen atom transfer step.348 

E = C02CH3 X,Y = TBDMSO, H Ph, H C02CH3, H C02CH3, C02CH3 2-dioxolanyl 

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