Vitamin B12 Catalyzed Radical Cyclizations of Arylalkenes

The use of vitamin B12 for synthetic organic transformations has been extensively studied. Herein, we report the intra­molecular cyclization reaction of a series of arylalkene substrates catalyzed by vitamin B12. These reactions proceed in good yields in environmentally benign solvents and do not require the use of a ­toxic heavy metal catalyst. Variation of the reaction pH can predictably alter the product distribution.