Regioselective Protonation of Allyllithium Compounds

By varying the general acid, the regioselectivity of the protonation of (triphenylsilyl)allyllithium ( 1 ) in diethyl ether in the presence of HMPT can be changed from 9:1 to 1:9 at room temperature. When other aprotic solvents are used, the nature of the lithium salt changes, and the selectivity decreases. The regioselectivity of the protonation of the dithio‐stabilized allyllithium 4 by water is highly dependent on the age of the allyllithium solution with α/γ ratios varying from 2.7:1 to 1:3.5.