Stereoselective nickel-catalyzed cycloisomerization of 1,6-dienes

Article abstract of DOI:10.1002/adsc.200800104

Highly stereoselective cycloisomerization of 1,6-dienes with a catalyst system based on [Ni-(allyl)(cod)][BARF] and Wilke's azaphospholene all-(R)-1 is described. Unprecedented high enantiomeric excesses of up to 91% were obtained for the formation of five-membered cyclic products from symmetrically substituted 1,6-dienes. High chemo- and regioselectivities were achieved also for unsymmetrically 1,6-dienes substituted in terminal position leading again to five-membered cyclic products in fair to very good yields. Cycloisomerization products were subjected to sequential hydroboration as well as hydrogenation of the exo-methylene functional group. Promising diastereoselectivities were achieved and these reaction sequences could be efficiently performed in a one-pot procedure.