Stereoselective Nickel‐Catalyzed Cycloisomerization of 1,6‐Dienes

Abstract

Highly stereoselective cycloisomerization of 1,6-dienes with a catalyst system based on [Ni-and Wilkes 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.

Ni‐Catalyzed Asymmetric Cycloisomerization of Dienes by Using TADDOL Phosphoramidites

“…The addition to the terminal double bond leads to cyclic products with a trisubstituted double bond, which can have an E or Z configuration. In contrast, the addition to the higher substituted internal double bond yields products with an exocyclic methylene group 18. 31…”

“…Finally, the cycloisomerization of N,N ‐diallyltosylamide (X=NTs; 5 f ) was investigated, thus representing a feasible route to five‐membered chiral N ‐heterocycles. Up to now, only low‐to‐moderate enantioselectivities have been achieved for this class of substrate, from which the best result was obtained by using the Wilke azaphospholene all ‐( R )‐ 1 and [Ni(allyl)(cod)][Al(pftb) 4 ] (i.e., 99 % selectivity and 54 % ee ; pftb=perfluoro‐ tert ‐ butoxide) 17b…”

“…By using the Wilke azaphospholene all‐ ( R )‐ 1 , the corresponding five‐membered ring products of type B were formed in moderate‐to‐high enantioselectivities (up to 80 and 54 % ee for X=C(CO 2 Et) 2 and NTs, respectively), thus providing the best currently found values for these substrates 17. Furthermore, we reported the highly chemo‐ and regioselective cycloisomerization of unsymmetrically substituted 1,6‐dienes and bis‐allylamines with this catalytic system 18. The possibility of tandem sequences that involve asymmetric cycloisomerization as an initial CC bond‐forming step was also shown.…”

Copper(ii) complexes incorporating poly/perfluorinated alkoxyaluminate-type weakly coordinating anions: Syntheses, characterization and catalytic application in stereoselective olefin aziridination

“…8 Meanwhile, as is the case with perfluoroborates and carboranes, per/polyfluoroalkoxyaluminates are of great interest for catalysis, e.g. C-C bond formation, 1k enantioselective hydrogenation, 9 asymmetric cycloisomerization, 10 3 ) 4 ]show at least the same or superior catalytic activities than other types of WCAs.…”

Deacylative Allylation of Nitroalkanes: Unsymmetric Bisallylation by a Three‐Component Coupling

“…[1] While monoallylation products are typically formed, bisallylation of malonates and related ketone enolates leads to 1,6-dienes. [2] Given the utility of these 1,6-heptadienes in metal-catalyzed cycloisomerization reactions, [3] it would be beneficial if one could perform controlled bisallylation of less stabilized carbon nucleophiles. Unfortunatly, the one-pot bisallylation of other carbon nucleophiles is not well documented and usually requires harsh reaction conditions.…”