Copper-catalyzed reactions of organotitanium reagents. highly selective SN2′-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 n Ti(O-i-Pr) 5−n Li) undergo highly selective S N 2′-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 3 SiCl. 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. 1 H NMR studies on a mixture of Me 2 CuLi and TiCl(O-i-Pr) 3 provided information on reagent composition. In the presence of cat Cu(I), various titanium reagents undergo S N 2′ alkylation with allylic chlorides and phosphates. These reagents also undergo conjugate addition to enones in the presence of copper catalyst and Me 3 SiCl.