Reaction, terminal transannular

Finally, cerium(IV) ammonium nitrate can serve as the radical source by itself, generating NO3 radicals If by photolysis. The addition of such radicals to cyclo-alkynes 20 initiates an interesting tandem reaction [12]. Transannular hydrogen atom abstraction by the vinyl radical 21 affords the intermediate 22, which undergoes a 5-exo cyclization to the radical 23. In the last step, the ketone 24 is formed by elimination of NO2 in moderate yield thus, the overall sequence can be described as a self-terminating radical reaction (Scheme 7). 

Raney catalysts s. Nickel Rays s. Irradiation Reaction, terminal s. w-Halogenation -, transannular s. Transannular... 

Catalyst 70 is very effective for the reaction of terminal alkenes, however 1,1-disubstituted olefins provide hydrosilylation products presumably, this is due to steric hindrance [45]. When a catalyst with an open geometry (78 or 79) is employed, 1,1-disubstituted alkenes are inserted into C-Y bonds to give quaternary carbon centers with high diastereoselectivities (Scheme 18). As before, initial insertion into the less hindered alkene is followed by cyclic insertion into the more hindered alkene (entry 1) [45]. Catalyst 79 is more active than is 78, operating with shorter reaction times (entries 2 and 3) and reduced temperatures. Transannular cyclization was possible in moderate yield (entry 4), as was formation of spirocyclic or propellane products... 

Cyclooctadiene undergoes a transannular reaction to form a bicyclo[5.1.0]octane system 1. The initiating electrophile and terminating nucleophile are trans-located in the product19. 

E,E)-. 6-Cyclodecadienone undergoes a transannular cyclization in the presence of mercuric acetate to form rram-decalins. Mixtures of products are found due to the nonselective termination reaction which consists of a nonregioselective proton elimination but stereoselective attack of the hydroxide ion16. 

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