Copper-catalyzed reactions of organotitanium reagents. Highly selective S N2′-allylation and conjugate addition

Abstract

In the presence of a catalytic amount of CuI·2LiCl, alkyltitanium (RTi(O-i-Pr) 3) and titanate reagents (R nTi(O-i-Pr) 5−nLi) undergo highly selective S N2′-alkylation reactions with allylic chlorides and allylic diethylphosphates in high yields. The regioselectivity of the reaction is as high as 99.8%. The reaction proceeds with excellent anti-stereoselectivity with respect to the nucleophile and the leaving group, and exhibits high 1,2- anti-diastereoselectivity with a δ-chiral allylic chloride. The catalytic copper reagent is also a mild agent to transfer an alkyl group to an enone in the presence of Me 3SiCl. The alkyltitanium-based catalytic reagent selectively reacts with an allylic phosphate rather than with an enone, while in the presence of a silicon activator, it reacts preferentially with the enone rather than with the phosphate. 1H NMR studies on a mixture of Me 2CuLi and TiCl(O-i-Pr) 3 provided information on reagent composition.