Cationic Nickel Complexes with Weakly Coordinating Counterions and Their Application in the Asymmetric Cycloisomerisation of 1,6‐Dienes

Abstract

Abstract The influence of the counterion on cationic nickel catalysts for asymmetric cycloisomerisation of diethyl diallylmalonate ( 1a ) and N , N ‐diallyltosylamide ( 1b ) is investigated. The activity of the catalysts formed from [Ni(η 3 ‐allyl)(η 4 ‐cod)] + salts of weakly coordinating anions in combination with Wilke's azaphospholene ligand decreases in the order [Al{OC(CF 3 ) 3 } 4 ] − >[B{3,5‐(CF 3 ) 2 ‐C 6 H 3 } 4 ] − >[Al{OC(CF 3 ) 2 Ph} 4 ] − for 1a and [B{3,5‐(CF 3 ) 2 ‐C 6 H 3 } 4 ] − > [Al{OC(CF 3 ) 2 Ph} 4 ] − >[Al{OC(CF 3 ) 3 } 4 ] − for 1b , respectively. No significant influence on the enantioselectivity is observed for 1a whereas a marked increase in ee parallel to a decreasing activity is found for the cyclisation of 1b .